486th Meeting - October 4, 2001

                Official Transcript of Proceedings


Title:                    Advisory Committee on Reactor Safeguards
                               486th Meeting

Docket Number:  (not applicable)

Location:                 Rockville, Maryland

Date:                     Thursday, October 4, 2001

Work Order No.: NRC-039                               Pages 1-265

                   NEAL R. GROSS AND CO., INC.
                 Court Reporters and Transcribers
                  1323 Rhode Island Avenue, N.W.
                     Washington, D.C.  20005
                          (202) 234-4433.                         UNITED STATES OF AMERICA
                                 + + + + +
                            486TH ACRS MEETING
                                 + + + + +
                              OCTOBER 4, 2001
                                 + + + + +
                            ROCKVILLE, MARYLAND
                                 + + + + + 
                       The Advisory Meeting met at the Nuclear 
           Regulatory Commission, Two White Flint North, Room 
           2B3, 11545 Rockville Pike, at 8:30 a.m., Dr. George E.
           Apostolakis, Chairman, presiding. 
                 DR. GEORGE E. APOSTOLAKIS, Chairman
                 DR. MARIO V. BONACA, Vice Chairman
                 DR. DANA A. POWERS, Member
                 DR. WILLIAM J. SHACK, Member
                 DR. THOMAS S. KRESS, Member at Large
                 DR. JOHN D. SIEBER, Member
                 DR. F. PETER FORD, Member
                 DR. GRAHAM  B. WALLIS, Member.           ACRS STAFF:
                 DR. JOHN T. LARKINS, Executive Director
                 DR. PAUL A. BOEHNERT, Executive Secretary
                 MEDHAT EL-ZEFTAWY, ACRS Staff
                 DR. ROBERT ELLIOT,  ACRS Staff
                 CAROL A. HARRIS, ACRS/ACNW
                 DR. JAMES E. LYONS, ADTS 
                 SAM DURAISWAMY, ACRS
                 DR. SHER BAHADUR, ACRS
                 PRASAD KADAMBI
           .                                 I-N-D-E-X
                          AGENDA ITEM                      PAGE
           Opening Remarks by ACRS Chairman . . . . . . . . . 4
           Duane Arnold Core Power Uprate . . . . . . . . . .10
           Readiness Assess for Future Plant Designs. . . . 100
                 and Staff Proposal Regarding Exelon's 
                 Regulatory Licensing Approach for the 
                 Pebble Beach Bed Modular Reactor
           Action Plan on Steam Generator Tube. . . . . . . 202
           Proposed Resolution of Generic Safety. . . . . . 247
                 Issue 173A, Spent Fuel Storage Pool for
                 Operating Facilities
           .                           P-R-O-C-E-E-D-I-N-G-S
                                                    (8:30 a.m.)
                       CHAIRMAN APOSTOLAKIS:  The meeting will
           now come to order.  This is the first day of the 
           486th meeting of the Advisory Committee on Reactor
                       During today's meeting the Committee will
           consider the following:
                       The Duane Arnold Core power Uprate; and
           the Readiness Assessment for Future Plant Designs and
           the Staff Proposal Regarding Exelon's Regulatory
           Licensing Approach for the Pebble Beach Bed Modular
                       The Action Plan to address ACRS Comments
           and Recommendations Associated with the Differing
           Professional Opinion on Steam Generator Tube
                       And the Proposed Resolution of Generic
           Safety Issue 173A, the Spent Fuel Storage Pool for the
           Operating Facilities; and the Proposed ACRS Reports.
                       A portion of this meeting may be closed to
           discuss General Electric Nuclear Energy proprietary
           information applicable to the Duane Arnold core power
                       This meeting is being conducted in
           accordance with the provisions of the Federal Advisory
           Committee Act.  Dr. John T. Larkins is the designated
           Federal official for the initial portion of the
                       We have received no written comments or
           requests for time to make oral statements from members
           of the public regarding today's sessions.  A
           transcript of portions of the meeting is being kept,
           and it is requested that the speakers use one of the
           microphones, and identify themselves, and speak with
           sufficient clarity and volume so that they can be
           readily heard.
                       We will begin with some items of current
           interest.  You all have this document with items of
           interest, and it contains a speech by Chairman Reserve
           on the growing area of radiation protection of
           patients.  He gave his speech at the IAEA general
           conference of senior regulators.
                       And also there are some safety significant
           findings that would be of interest to us when we
           discuss the reactor oversight process.  There was a
           yellow finding at the plant and six white findings. 
           I found them very interesting to read for later this
                       The NRC is putting together the 2002
           regulatory information conference, and requesting
           suggestions for agenda items.  If you have any, you
           have by October 5th to send them to the staff.  
           And Dr. Larkins has a short announcement to make. 
                       DR. LARKINS:  Yes.  Good morning.  Members
           of the public and all non-NRC employees attending this
           meeting to be escorted when leaving this floor.  It
           would be appreciated if people would leave at the end
           of the session, such that an ACRS office individual
           can escort you to the first floor.
                       An escort will be available at the end of
           the session, or each session, to take individuals down
           to the first floor on the elevator.  Obviously, this
           does not preclude individuals from using the
           facilities, the restroom facilities and others on this
           floor, as a guard will be stationed outside of the
           meeting room.
                       We appreciate your cooperation in what we
           hope will be a temporary situation.  Secondly, I would
           note for ACRS members and staff, that the Deputy
           Executive Director for Management, Ms. Pat Nouri, will
           give a presentation at one o'clock today in this
           conference room on security issues at I and II White
           Flint Complex, and other matters.
                       You are invited to either have your lunch
           before or during this discussion, and she will answer
           questions related to matters surrounding the operation
           of the two buildings.  Thank you.
                       CHAIRMAN APOSTOLAKIS:  Two more items.  By
           a voice vote on September 26th, the Senate confirmed
           former Commissioner Diaz to serve a second term as an
           NRC Commissioner, through June 30th, 2006.  Dr. Diaz
           will be sworn in today for his second term.
                       And the last item is that because of
           illness, our member, Graham Leitch, will not be
           attending this meeting.  He is at home recuperating,
           and of course we all wish him a speedy recovery.  
                       Now, back to the agenda.  The first item
           is the Duane Arnold Core Power Uprate.  Dr. Powers is
           the Cognizant Member.  Dana.
                       DR. BONACA:  I would like to make a
           statement.  I have a conflict of interest.
                       CHAIRMAN APOSTOLAKIS:  So you will keep
           quiet for a change?
                       DR. BONACA:  I will try to keep quiet.  
                       DR. FORD:  On the Duane Arnold issue, I
           have a conflict of interest being a former GE
                       CHAIRMAN APOSTOLAKIS:  It is going to be
           a quiet meeting.  Dr. Powers.
                       DR. POWERS:  Gee, I don't have any
           conflict of interest.  Sorry.  Well, we are going to
           discuss the application for a power uprate from Duane
           Arnold.  It has significance for us, and it is the
           first that we have heard of many that we expect to
           come in the future.
                       Many, if not all, of the BWRs, were
           designed for much higher powers than they have been
           operating for the last several years.  They were kept
           at a somewhat lower powers because of concern over the
           ATWS and the reactor stability issue back a long time
           ago, and part of that concern came from the ACRS
                       So it is somehow fitting that we should
           hear about the relief from that concern, which has
           come about in a generic way from General Electric. 
           When we go into this power uprate, you are going to
           see that the applicant and the staff have addressed a
           host of issues, quite a lengthy list of issues that
           had to be addressed in looking at these power rates.
                       But in truth, they are relatively few that
           are of particular concern.  Those tend to be the ATWS,
           the operator response times, material degradation, and
           some infrequencies in the containment response
           capabilities, and I think that is where the committee
           should be focusing its attentions.
                       The application that is being made here is
           not a risk informed application.  This is a classic
           deterministic application.  But I think you are going
           to find that risk is a language that has crept into
           the classic deterministic analyses, and has played a
                       And in some cases I might say the
           applicant has done some very imaginative and creative
           things in the use of risk, even though he has a
           deterministic application here.  
                       And I think it would be great fun to have
           them back and go through in some detail the risk
           portions of what they have done with their plant,
           because I think we would find it interesting on what
           they have been able to do, and what they have been
           able to learn from risk.
                       But that is not our focus here.  The order
           of presentations today is going to begin with a
           presentation by the applicant himself.  We have given
           him a very easy chore.  We have only asked him to
           compress 4-1/2 hours of a very detailed presentation
           into 26 minutes or so.
                       And in looking at his view graphs, he has
           done a manful job of doing this, but do recognize that
           he is giving a synoptic account of all that they have
           done; and that will be followed by the staff, who are
           equally time constrained for their -- what amounted to
           a little over 4 hours of presentation on their part
           before the subcommittee.
                       So with that, I am going to introduce Ron
           McGee to begin the presentations, and Ron, you will
           introduce Tony and other people as they present.
                       MR. MCGEE:  That's correct.  Thank you,
           Dr. Powers.  Good morning.  As he stated, my name is
           Ron McGee, of the Nuclear Management Company at the
           Duane Arnold Energy Center.  
                       We have been asked to provide an overview
           of the material that we presented to the subcommittee,
           the Thermal Hydraulic Subcommittee, and as a
           subcommittee members kind of test, we provided a large
           amount of information.
                       And hopefully we can address any of your
           questions.  As you can see from the introductory
           slide, our original rated thermal power was 1593
           megawatts thermal, and we uprated the plant in the
           early 1980s, and are currently licensed for operation
           at 1658 megawatt thermal.
                       The application that we have before the
           staff at this time is for operation at 1912 megawatts
           thermal.  We prepared a deterministic application in
           accordance with the previously approved General
           Electric topical reports.  
                       Although the application was not a risk-
           informed submittal, we have performed an impact review
           utilizing our PRA, and I will point out how that
           information was utilized in some of our upcoming
                       Concerning the modifications for power
           uprate, we installed all of the necessary safety
           related hardware changes during the 2001 spring
           refueling outage.  For the balance of the plant, we
           have decided to implement the power uprate in two
                       They are the modifications in Phase I for
           operation up to 1790 megawatt thermal, which were also
           accomplished during our spring refueling outage.  The
           remaining modifications will be installed during a
           future refueling outage.
                       Operator training.  Once the engineering
           evaluations were completed and the modifications were
           designed, we began training the operators on the
           impacts of power uprate.
                       In the classroom, we emphasized the design
           basis changes, and explained the plant equipment
           modifications.  In the simulator, we showed them
           static and dynamic examples of the most significant
           changes, and then put the crews through routine
           simulator accident and transient scenarios.
                       The PRA analysis and the engineering
           evaluations each pointed out the importance of the
           ATWS event as we mentioned earlier.  Specifically, the
           operators' ability to correctly inject standby liquid
           in a timely fashion is critical to mitigate this
                       So we emphasize this point in the
           classroom, as well as in the simulator training
           sessions.  The revised PRA assumes a 20 percent
           failure rate for injecting standby liquid.  
                       In reviewing past performance records, we
           found 58 evaluated ATWS, with a 100 percent success
           rate for the operating crews completing this task for
           injecting standby liquid.
                       DR. POWERS:  This is a striking thing.  I
           mean, you go through the human reliability analysis,
           and you come up with .1 and .2, and some sort of
           failure rate.  You get a hundred percent success rate
           in your training exercises.
                       And I looked at some of the studies that
           have been done in the past, and while I find for in
           NUREG CR 3737 that they went through an analyses, and
           they came to the conclusion that there was no
           relationship between scores during training exercises,
           and air rates by plants.  Do you have any thoughts on
                       MR. MCGEE:  We merely used the information
           provided to us by the training session as a benchmark
           so that we were certain in our minds at least that the
           failure rate that we had chosen was at least
                       So utilizing the industry acknowledged
           standard for error rates for operators, we were
           confident that we were bounded by that particular
                       CHAIRMAN APOSTOLAKIS:  Where did that 20
           percent come from?
                       MR. MCGEE:  Brad, could you address that,
           please, the 20 percent that we assumed in the PRA
           analysis for the operator failure rate for injecting
           standby liquid.
                       MR. HOPKINS:  This is Brad Hopkins from
           the NMC.  The error rates that we used come from a
           variety of industry standard methods for determining
           human error probabilities.  So we have a formula that
           considers the complexity of the actions, and how time
           they have to achieve the actions.
                       DR. POWERS:  Can you give us an idea of
           how the time changed, and from your originally
           licensed power to the higher level, or the
           intermediate to the higher, whichever one is easiest
           for you to do.
                       Well, for the key operator action, or for
           the ATWS event, is the time available for injecting
           standby liquid control, and there we have values for
           early injection, and one for late injection.  
                       For early injection, the time decreased
           from six minutes to about four minutes; and for late
           injection, I believe from 15 minutes down to about 12
                       CHAIRMAN APOSTOLAKIS:  So what was the
           failure rate when the time was 6 minutes?
                       MR. HOPKINS:  You will have to excuse me. 
           I have a slide with that number on it.  Just a minute.
                       CHAIRMAN APOSTOLAKIS:  So are you planning
           to talk about these things later?
                       MR. HOPKINS:  Yes.  
                       MR. MCGEE:  We do have a slide
           presentation on PRAs.
                       CHAIRMAN APOSTOLAKIS:  So you know then
           what question I am going to ask.
                       MR. HOPKINS:  Yes.  Here is the answer. 
           From .11 to .18.
                       CHAIRMAN APOSTOLAKIS:  And we will have
           some questions on that later.
                       MR. HOPKINS:  Okay.  Very good.  
                       DR. POWERS:  In my thinking on this
           subject is the human reliability analysis has done its
           job here, and that you record a relatively high
           potential for failure in this operation, and
           consequently you train on that.  
                       And we can't just help feel that training
           must help in keeping that number lower than perhaps we
           calculated here.  We may not know exactly what it is,
           but at least we are providing experience and training
           with this kind of an event. 
                       MR. HOPKINS:  That's correct.
                       DR. POWERS:  That is my interpretation of
           what has happened here.
                       MR. MCGEE:  Unless there are other
           questions at this point, I would like to turn the
           presentation over to Tony Browning.
                       MR. BROWNING:  Good morning.  Once again,
           my name is Tony Browning, and I am with the NMC at the
           Duane Arnold Plant.  I have the privilege this morning
           to present to the ACRS the results of our thermal
           hydraulic evaluations for EPU, our reviews of plant
           materials in the EPU environment, and finally our
           investigation into risk insights from EPU operation,
           using our probablistic risk assessment methodologies.
                       Today I will briefly summarize our
           evaluation in these key thermal hydraulic analysis
           areas.  For the ATWS EPU evaluations, we analyzed the
           four bounding events identified by the generic studies
           in the ELTRs:
                       The main steam isolation valve closure
           transient, and the pressure regular failure open
           transient, and the loss of off-site power transient,
           and the inadvertently opened relief valve transient.
                       These evaluations were performed using NRC
           accepted methods and assumptions.  This is a
           deterministic evaluation, with conservative
           assumptions and acceptance criteria; as opposed to our
           more realistic or best estimate evaluations performed
           with our PRA models, which I will discuss later in a
                       The purpose of this evaluation is to
           demonstrate compliance with prescriptive hardware
           requirements of the ATLS rule, 10 CFR 50.62, by
           showing conformance to the underlying analysis basis
           for BWRs as documented in the GE topical report NEDE-
                       As we can see the results were all within
           their respective acceptance criteria, with margin. 
           Thus, the DAEC will continue to comply with the ATWS
           without changes to the existing plant hardware.  
                       Next I would like to discuss our
           evaluation of thermal hydraulics stability.  First, I
           would like to start off with some background
           information.  The DAEC has implemented the stability
           solution called Option 1-D.
                       The key point of the Option 1-D solution
           is that it has been demonstrated that these plants,
           through their inherent design characteristics, are
           only susceptible to core wide or fundamental mode
           oscillations, and not the regional or higher harmonic
                       This greatly simplifies the solution
           approach.  This solution utilizes a combination of
           prevention with detection and suppression measures to
           conform to general design criteria 12.
                       DR. POWERS:  What this means is that you
           are getting parallel channel flow problems?
                       MR. BROWNING:  No.  That's the regional
           mode, where you have one side of the core oscillating
           out of phase with the other side.  Our plant is not
           susceptible to that mode of oscillation.  
                       It is only the fundamental mode where the
           code is oscillating in unison.
                       DR. POWERS:  It is sometimes called the
           direct loop oscillation?
                       MR. BROWNING:  Correct.
                       DR. POWERS:  And it is an NED24222 that I
           will find the mathematics on this?  
                       MR. BROWNING:  No, the General Electric
           topical report that I referenced earlier was for the
           ATWS evaluation.  I'm sorry, but off the top of my
           head, I don't remember the topic number for that
                       DR. POWERS:  I have looked, and I cannot
           find the underlying analyses that support your
                       MR. BROWNING:  It is in one of the early
           topicals, but I don't know it off the top of my head.
                       DR. POWERS:  If you happen to find that
           after we are done here, I would sure appreciate
           looking at it.
                       MR. BROWNING:  Very good.
                       DR. POWERS:  I am willing to believe right
           now, but --
                       MR. BROWNING:  Yes.  Prevention is
           accomplished by establishing this exclusion zone right
           here, this red line, on the power to flow map. 
           Operation is restricted in this region inside of here.
                       Thus, we prevent the oscillations by
           affording the area of operation most susceptible to
           instability, and we introduce a 20 percent margin by
           using a conservative criteria of 0.8 for the
           calculated K-ratio used to establish this boundary.
                       We introduce additional margin by
           establishing this buffer zone, represented by the
           orange line, by adding another 0.05 to K-ratio margin
           to the exclusion zone, where operation is allowed only
           when the SOLOMON software is available on the plant's
           core monitoring computer.
                       The SOLOMON software is the same model as
           ODSY, the frequency domain code used to calculate the
           decay ratios used to establish the exclusion zone and
           buffer zone boundaries.
                       So we are only allowed to operate in this
           region between the two lines when SOLOMON is available
           to provide the operators a prediction of their margin
           to an unstable condition.
                       Otherwise, operation is prohibited in the
           boundary zone region as well.
                       DR. KRESS:  This is a picture of how you
           start up and shut down?
                       MR. BROWNING:  Correct.
                       DR. KRESS:  Are there accident conditions
           that will force you into that zone?
                       MR. BROWNING:  Yes, there are.  Any number
           of transients, either single or dual pump --
                       DR. KRESS:  Will take you down the mellow
                       MR. BROWNING:  -- will put us down into
           this region, right.  And the operators are instructed
           any time they enter the exclusion zone to take
           prescriptive measures to leave that zone immediately.
                       And if they notice any instability
           condition on their in-core monitoring, they are to
           SCRAM the plant immediately.  Detection and
           suppression comes from the flow bias neutron flex
           reactor trip signal.  
                       We validate this capability by
           demonstrating analytically that any oscillation will
           be suppressed by this flow bias SCRAM prior to the
           fuel experiencing a transient that would exceed the
           safety limit minimum critical power ratio.
                       While the major impact of extended power
           uprate on thermal hydraulic stability is through the
           introduction of MELLLA, which is raising the rated
           load line from the black line to the blue line, which
           expands the size of the exclusion and boundary zone
           regions on the power to flow map, the operational
           impact is acceptable as seen by this actual plant
           start-up trace.  
                       As we see, it is possible to maneuver the
           plant around these zones, and thereby introducing more
           margin in the stability.
                       DR. POWERS:  When you plot power versus
           flow, if I were to look at power versus time, would I
           see a continuous curve here, or would I see a lot of
           steps and overshoot and undershoots of that curve?
                       MR. BROWNING:  I will let Steve answer
           that, our plant operator.
                       MR. KOTTENSTETTE:  I am Steve
           Kottenstette, and I am an operations shift manager at
           the plant.  Normally over time, you will see us come
           up in power and stabilize to do some annual requested
           testing, and then go up.  
                       We don't have overshoots or anything.  We
           just pretty much gradually go on up in power.
                       DR. POWERS:  So where you come up and
           enter your buffers or touch your buffer zone margin at
           about 25 million pounds per hour, I would not see you
           jumping in and out of that buffer zone? 
                       MR. KOTTENSTETTE:  No, you wouldn't. 
           Remember that the start up here is to our current
           1658, and the power flow map that you have there is
           actually what we will have.
                       DR. POWERS:  I understand that.  I am just
           asking generically what the curve is.  It seems to me
           that the curve could have been drawn with a much wider
           pencil if there was a lot of overshooting and
           undershooting, and things like that.  You are really
           telling me that I am really looking at the outer
           bounds on it?
                       MR. KOTTENSTETTE:  Right.  
                       MR. BROWNING:  Thus, by establishing
           conservative boundaries for the exclusion and boundary
           zones and demonstrating the detect and suppress
           capability of the flow by flux SCRAM to ensure that
           safety margins are maintained under extended power
           uprate operation.
                       And as seen from our start up example,
           adequate operating margins exist under extended power
           uprate as well.  Now I would like to move on and
           discuss the impact of a potential --
                       DR. WALLIS:  While you have got this
           figure up there, you are a hundred percent power, and
           you are asking for 1912 megawatts, and it looks like
           if it is a very small region of flow rate that you can
           be in to be at the hundred percent power.
                       MR. BROWNING:  Right.
                       DR. WALLIS:  And you are right in the
           corner of that graph, and the question is whether you
           can really keep it as close as that without stepping
           over some boundary.  There is very little room for
           error up in that corner.
                       MR. BROWNING:  A very astute observation,
           Dr. Wallis.  Our reactor engineering crew is going to
           be challenged to find drive patterns that will allow
           maneuvering in here.  Most likely what will happen is
           that we will have to be very slow and deliberate in
           this region to ensure that we don't encroach on the
                       And so again you are very astute.  It is
           going to be somewhat of a challenge to operate up in
           this very tight corner of the power plant.  
                       DR. WALLIS:  And as your fuel burns up,
           you will have different work patterns and so on in
           order to maneuver in there.   
                       MR. BROWNING:  Correct.
                       DR. WALLIS:  So you might well find
           yourselves operating at 95 percent power for quite a
           while until you learn how to get up there.
                       MR. BROWNING:  Yes.  We will need to have
           some operating experience in this region in order to
           better refine our capability there.
                       MR. MCGEE:  And also -- this is Ron McGee
           -- during our interim plant, or during our phase one
           session, we expect to accumulate quite a bit of
           operating experience because we will have a larger
           flow window.  We will be operating between our current
           and the expected maximum allowable.
                       MR. BROWNING:  Right.
                       DR. WALLIS:  And if you look at what you
           do now, that wanders around in an almost erratic way
           as you search for broad patterns near the top in the
           present plant.
                       MR. BROWNING:  Yes, and also compensating
           for Zenon as things build in.  Now I would like to
           move on and discuss the impact of a potential ATWS
           instability during DPU operation.  
                       As part of the closure of thermal
           hydraulic stability issues, generic studies were
           performed to determine whether the combination of a
           core wide instability event with failure to suppress
           the oscillations by a plant SCRAM because of an ATWS
           event would lead to significant fuel failure.
                       And if so, to determine mitigating
           strategies that would minimize these impacts, because
           the first study did confirm that such an event,
           assuming no mitigation at all, would lead to
           unacceptable fuel cladding failure.
                       And a second study was conducted to find
           mitigating strategies.  The conclusion of the second
           study confirmed that existing ATWS strategies
           implemented by the BWR owners group emergency
           procedure guidelines were effective in precluding
           these fuel cladding failures.
                       And these being lowering the water levels
           below the feed water sparger, which reduces the core
           inlets subcooling, and which lowers the magnitude of
           the power spikes during the oscillations.
                       And, second, and in the lower term,
           injection of boron through the standby liquid control
           system to completely dampen the oscillations.  
                       DR. POWERS:  When these studies were done
           did they consider the power profiles similar to the
           type that you will have once you start operating at
           the higher power?
                       MR. BROWNING:  Yes, and that is a good
           seagueway.  The generic studies were found to be
           bounding upon Duane Arnold because they had previously
           considered operation in the MELLLA region.
                       And they were also looking at peak bundle
           powers significantly higher than what Duane Arnold
           will be operating after an extended power uprate.  So
           it is the peak bundle power that drives the response,
           and that was bounding upon us.  
                       DR. POWERS:  I guess what I am questioning
           is whether the peak bundle power is really what is
           limiting here, or does it make a difference how that
           power varies along the length of the core?
                       And the reason for asking the question is
           that it is fairly simple.  You lower the water levels
           so that the collapsed level is below the top of the
           core.  So you are relying on a certain amount of steam
           cooling for the upper region of the rods.
                       Now, your upper regions of the rods have
           a higher decay power than they would if you had a
           classic cone type of power distribution.  You have a
           little different one now.  
                       And so what I am asking you is does that
           make any difference in this recovery process or is it
           being looked at?
                       MR. BROWNING:  Unfortunately, I am not the
           person to ask that.  We don't have our General
           Electric experts with us today.  
                       DR. POWERS:  Gee, with all the conflicts
           of interest at the table, maybe they could answer.  
                       MR. BROWNING:  One of the things that is
           important in the extended power uprate for Duane
           Arnold is that we are going to the GE14 fuel design,
           which has partial length fuel rods.
                       So that tailors the power shape in the
           upper region to keep it from being overly top-peaked. 
           So by that combination, I think if we did do the
           investigation we would find that that would be the
           factor that would keep us bounded by the study.  And
           you have stolen most of my thunder of this
                       DR. POWERS:  Keep covering your thunder. 
           Don't stop.
                       MR. BROWNING:  And one of the important
           points of this is what we have touched on; is that the
           peak bundle power under extended power uprate is not
           increasing from where it is today.
                       What we are doing is flattening the radio
           profile and raising the average core power so that the
           peak bundle response is not changing from where we are
                       DR. POWERS:  I have to admit that when you
           first came into this application for a power uprates,
           and you find that nothing seems to change, you are
           wondering if it is done with smoking mirrors here.  
                       MR. BROWNING:  That is a astute
           observation, because you find through this exercise
           the parameters that do drive the response, and it
           turns out in many cases that just basic power level is
           not one of them.
                       But this is an area of containment where
           we will see it.  We will see it.  So, for the DAEC
           extended power uprate, we reanalyzed the containment
           response using previously approved NRC calculational
           models and assumptions for the FSAR events.
                       To illustrate the impact of EPU, let's
           look at both the short term and long term cases for
           the design basis loss of coolant accident.  First, for
           the short term response, the increased subcooling due
           to EPU increases the blow down flow rate, which
           directly drives the dry wall pressure response.  
                       As we see here the dry wall pressure
           increases slightly due to EPU, but we are not
           increasing the reactor pressure, and the impact of EPU
           is not dramatic in the short term.  So, we have
           learned it is the reactor pressure that drives this
           response, and not the sub-cooling.
                       However, because the decay heat power
           increases proportional to the increase in core thermal
           power, the long term impact is a bit more noticeable
           as you see here.  
                       DR. WALLIS:  But that temperature depends
           upon the temperature that it starts out at doesn't it?
                       MR. BROWNING:  That is correct.
                       DR. WALLIS:  So how close is the initial
           temperature controlled?
                       MR. BROWNING:  That is controlled by
           technical specifications in our license.  We are not
           allowed in steady state operations to go above 95
           degrees unless --
                       DR. WALLIS:  So this is calculated
           assuming you are at 95 when you start?
                       MR. BROWNING:  That is correct.  That is
           a conservative input measure.
                       DR. ROSEN:  At the time that you reach the
           215.3 degrees in the suppression pool what is the
           pressure in the containment?
                       MR. BROWNING:  At the corresponding time?
                       DR. ROSEN:  Yes.
                       MR. BROWNING:  Do you have that number,
                       MR. RODERICK:  Not off the top of my head,
                       MR. BROWNING:  Do we have one of our back
           up slides?
                       (Brief Pause.)
                       MR. BROWNING:  We are looking it up for
           you.  We will move on then.  This impact is also true
           in the calculation of net positive suction head in the
           emergency core cooling system, plus taking suction
           from the suppression pool.
                       The hotter pool, due to increased decay
           heat from EPU, leads to an increase in the amount of
           over pressure required to ensure adequate MPSH.  It
           should be noted that Duane Arnold has always been
           licensed to allow over pressure for meeting adequate
                       As we see here the DAEC's dependence is
           not in the short term, but only in the long term.  We
           also see that we have adequate margin between the 5.3
           psi that is required, and the 13.3 over pressure that
           is available during the peak suppression pool
           temperature for MPSH.
                       DR. POWERS:  I think that gives us the
           pressure doesn't it?
                       MR. BROWNING:  It is similar, but this is
           a slightly different analysis, with slightly different
           assumptions.  So it is not quite the answer you were
           looking for.
                       DR. KRESS:  Usually in the long term the
           pressure corresponds to the saturation pressure from
           the temperature in the pool.  That is probably pretty
                       MR. BROWNING:  It is very close.
                       DR. POWERS:  It seems to me that if I was
           going to have to have over pressure giving me enough
           net positive section head, I would want it in the
           short term and not want it in the long term.  And it
           seems exactly the opposite here.
                       And things are going to degrade and I am
           going to lose pressure and it is in the longer term
           and not in the short term.
                       DR. KRESS:  Well, I don't know when they
           call to require that section head.  It is probably
           needed in both short term and long term.
                       DR. ROSEN:  I think what they are saying,
           Tom, is that it is not needed in the first 10 minutes. 
           It is beyond 10 minutes where it is needed.
                       DR. WALLIS:  But the two are interrelated. 
           I mean, the amount of containment pressure and the
           amount of MPSH you need is sort of interrelated,
           because the temperatures are interrelated anyway.
                       MR. BROWNING:  A lot of it has to do with
           the density of the water in the pool, and so that is
           what happens, and that is what you see in the longer
                       It takes a while for the pool ot heat up,
           and then at that point with the new strainer designs
           that we have, and the assumption of the debris
           loading, it is not until much later when we get into
           a position where we require the over pressure in order
           to meet MPSH.  
                       All right.  This is the time response in
           hours for the event, and as we see here, the red line
           is the required MPSH for the core spray pump, which is
           bounded over the RHR pump, and we can see here the
           time frame in which we need the over pressure as we
           cross over atmospheric.  So it is after about the
           first hour into the event, and lasts until about 23
                       DR. WALLIS:  That's what I mean about the
           temperatures being interrelated.  These curves all
           have the same shape, and if you are going to change
           one by something, then probably the others will change
           as well.  If you have some sort of containment, then
           they will all change.
                       MR. BROWNING:  Right, and you can see here
           that this is the actual response, and it is
           significantly more throughout the duration.
                       DR. POWERS:  So we have about a one day
           window in which we need over pressure.
                       MR. BROWNING:  Correct.
                       DR. POWERS:  And so we can't have any
           degradation of the drywall pressure boundary during
           this period, right?
                       MR. BROWNING:  That is correct.  One of
           the assumptions that goes into this calculation -- and
           Mr. Roderick can correct me if I am speaking out of
           turn here, that one of the assumptions for this
           analysis is we assume twice the tech spec allowable
           leakage rate for the containment to do these
           calculations.  So it is a conservative calculation.
                       DR. POWERS:  Well, why did you pick twice? 
           Why not 10 times?  
                       MR. RODERICK:  This is Al Roderick with
           Duane Arnold.  The assumption of a 5 percent leakage,
           which is a little over twice the tech spec limit, is
           consistent with the way that the containment analysis
           was done when we established over pressure for the
           original license.  And that assumption was used at the
           original plant licensing.
                       DR. POWERS:  Well, you didn't really tell
           me what the underlying scheme is.
                       DR. WALLIS:  It is really a factor of two
           because this is thermal hydraulics.  If it were a PRA,
           you would use a factor of 10.
                       DR. POWERS:  I understand.  And if it were
           metallurgy, we would use a factor of a hundred, right?
                       DR. BONACA:  I have a question.  Did you
           have to make any changes to your EPGs?
                       MR. BROWNING:  As a result of?
                       DR. BONACA:  As a result of -- well, these
           issues, but also power uprate in general.
                       MR. BROWNING:  No, we did not.  There is
           subtle changes in some of the parameter graphs that
           are driven by the decay heat levels, but the actual
           flow charts with the operator actions and precautions
           were not changed as a result of the EPGs.
                       DR. BONACA:  When you went through a total
           review of the EPGs?
                       MR. BROWNING:  That is correct.
                       DR. POWERS:  This requirement for over
           pressure for net positive section head, however, is
           not qualitatively different than what was required in
           your original license, and there is simply a
           quantitative difference? 
                       MR. BROWNING:  That is correct.  The shape
           of this curve is fundamentally the same as it was in
           the original license.
                       DR. POWERS:  Was the period of time that
           you needed for the net positive section head, has that
                       MR. BROWNING:  I can't answer that today,
           Dr. Powers.  We would have to go back and look, unless
           Al has information on that.  Were you able to do some
           background there?
                       MR. RODERICK:  This is Al Roderick.  Just
           from the standpoint of the increase in the power
           level, the decay heat is going to be running you out
                       So given that the pool temperature really
           drives when you need the over pressure, I would say
           the time from the time that the overpressure is needed
           at 1593, compared to 1912, yes, we are going to need
           a longer period of time.
                       DR. POWERS:  The curves are all the same
           shape.  It is adding one thing.  It is not like we
           have a very long tail here.  
                       MR. RODERICK:  While I am up here, the
           answer -- you asked what the containment pressure was
           when we are at the peak pool temperature of 215.3 for
           this event, in looking at the graphical results, we
           are about at 20 psig for containment pressure at that
           point in time.
                       MR. BROWNING:  If there are no more
           questions, I would like to move on, and we would like
           to talk about ECCS analysis that was performed.  The
           DAEC has utilized the SAFER/GESTR methodology for ECCS
           analysis prior to EPU and this is an entire change for
                       Under the SAFER/GESTR LOCA methodology
           approved under the provisions of SECY 83-472, for the
           use of nominal or more realistic models, dual
           acceptance criteria, are applied.  
                       First, the licensing basis peak cladding
           temperature is calculated using the required Appendix
           K inputs to demonstrate conformance to the 50-46
           acceptance criteria of 2200 degrees fahrenheit.
                       The second acceptance criteria is on the
           so-called upper bound PCT, which is calculated from
           the nominal inputs statistically adjusted for the
           uncertainties in the models due to both generic and
           plant specific inputs.
                       The resulting upper bound PCT is first
           compared to the licensing basis PCT to demonstrate
           that the licensing basis calculation is higher, and
           does a bounding result.
                       And then we ensure that the upper bound
           PCT remains within the 1600 degree fahrenheit limit
           placed on the methodology, which ensures that the
           results stay within the bounds of the test data on
           which it is based.
                       DR. POWERS:  Let me make this very clear. 
           Is there two different analyses, with different sets
           of assumptions, going into them?
                       MR. BROWNING:  Correct.  And it is
           graphically depicted here.  This figure is a bit busy,
           but it succinctly presents a number of key points
           about the analysis.  
                       First, we see that for small and large
           breaks, they were analyzed to confirm that the large
           break, or the dba case here, remains limiting under
           extended power uprate conditions.
                       Next we see that the upper bound PCT is
           indeed less than the licensing basis PCT, and below
           its 1600 degree limit.  In addition, we see that the
           licensing basis PCT has significant margin to its 2200
           degree limit.
                       Now, comparing the current and EPU
           results, we notice that here in the small break LOCA,
           we see a slight difference.  But as we move up at the
           licensing basis calculation, the EPU does not have as
           big an impact on the licensing basis PCT.
                       And this is because the peak bundle power
           is not changing from the pre-EPU conditions, which is
           what drives the PCT calculation.  Thus, we conclude
           that under EPU, we have both substantial safety
           margins as required by the regulation, as well as a
           significant operating margin here.  This concludes my
           presentation.  If there are no further questions in
           this area --
                       DR. ROSEN:  I do have a question.  I would
           like to come back to the question and answer we had a
           moment ago about the peak pressure, and if you would
           go back to your slide nine.  
                       (Brief Pause.)
                       DR. ROSEN:  And when we talked about the
           suppression pool temperature in the long term, and the
           EPU conditions of 13.3 degrees, it was offered from
           the floor that that pressure is 23 psig in the
           containment at that time.  
                       But if you go to the next chart in the
           long term, what we see there is that the pressure is
           13.2 psig over pressure at the peak at the suppression
           pool temperature.
                       And I don't understand the distinction
           between those two numbers, and perhaps you could clear
           that up.
                       MR. BROWNING:  The 13.2 psig is the over
           pressure required, and the absolute power is 28 pounds
           at that point.
                       DR. ROSEN:  But I am comparing the 20 psig
           that was offered from the floor at that similar
           condition, and there was a statement made that they
           are not exactly comparable.  
                       Hence, the difference between 13.3 and 20,
           but I don't understand the reasons why they are not
           exactly comparable.  I don't expect those numbers to
           be the same.
                       MR. RODERICK:  This is Al Roderick.  Those
           are two separate analyses that use different
           assumptions.  The DBA LOCA is using assumptions that
           will maximize pool temperature, and takes no credit
           for heat syncs, et cetera.  
                       When we do a containment analysis looking
           at over-pressure, the assumptions that we make in that
           model, while we have to balance the needs, we are
           doing two things.  
                       One, we are trying to maximize pool
           temperature, and at the same time we are trying to
           minimize containment pressure.  So it is its own
           containment analysis.  So that is why you see a lower
           pressure in the over-pressure for MPSH at 13.3 at its
           peak temperature, versus the 20 pounds in the DBA
                       DR. ROSEN:  It's a question of doing the
           conservatisms differently because of the two different
           acts or two different conditions.  In one case, you
           are trying to show conservatively that you have enough
           MPSH, and hence you could up with a lower number.  
                       MR. RODERICK:  Correct.
                       DR. ROSEN:  And in the other case, you are
           doing the DBA calculations to look at the containment
           response, and the margin to containment design
                       MR. RODERICK:  That's correct.
                       DR. ROSEN:  So I understand now.  So what
           it is then is both of those analyses, if done
           conservatively, so that you have an appropriate margin
           of conservatism for the parameter of interest for that
                       MR. RODERICK:  That's correct.
                       DR. ROSEN:  Thank you.
                       MR. BROWNING:  Let's now move on to a
           discussion on BPO and pictorial materials.  Before I
           begin with my formal presentation, we would like to
           take this opportunity to address the subcommittee's
           open item from last week's meeting.
                       For the record, we have included in the
           handout package a copy of the written response that
           explains in the increase in stress on the main reactor
           flange from the increase in temperature due to EPU.  
                       And I would be happy to address any
           questions that the Committee might have on this
           particular issue at the end of our prepared
                       With that, I would like to begin our
           discussion on the impact of EPU on materials, and
           specifically our programs for addressing flow assisted
           corrosion, otherwise known as erosion/corrosion and
           in-service inspection of the reactor vessel internal
           and associated piping systems.  
                       DAEC has modeled its carbon steel piping
           systems, which are susceptible to flow assisted
           corrosion, using the EPRI CHEKWORKS package.  The
           changes in flow and temperature profiles due to EPU
           have been modeled in CHEKWORKS and its resulting
           predictions for wear are being incorporated into the
           second and most important part of this program, which
           is the actual inspection of piping for wall thinning.
                       These CHEKWORKS predictions tell us to
           expect a slight increase in wear after EPU, on the
           order of a half, to one-and-a-half mils per year.  But
           based on our base line from previous inspections, this
           increase in wear should not cause a wall thinning
           problem over the remaining life of the plant.
                       It seems that we have been blessed with
           fat pipes, with wall thicknesses on the high side,
           with the specified manufacturing tolerances.  So we
           have installed margin in this area.
                       DR. ROSEN:  What are the most sensitive
           components to flow assisted corrosion?
                       MR. BROWNING:  It is generally the
           chemistry and the temperature.
                       DR. ROSEN:  No, but what components do you
           find the biggest changes as a result of EPU?
                       MR. BROWNING:  The feed water piping.  We
           have a table for that.  This is the results on the
           representative feed water piping that shows the
           increases.  So from this we could see where the
           changes occurred in the parameters.
                       DR. POWERS:  I think you will probably
           have to translate for the committee what DLA-02-E14
           is.  The Committee reads these things very thoroughly,
           but they probably just have a hard time recalling
           those particular sections.
                       MR. BROWNING:  These are particular
           sections in feed water piping, and this is how we
           designate them in our plant drawings so that we know
           what we are talking about.  
                       And this is an elbow, and as you can see,
           it is in elbows that you would expect to see most of
           the wear.
                       DR. ROSEN:  This is main feed water piping
           at the elbows, and -- 
                       MR. BROWNING:  Correct.  You can see the
           current wear ways to predictions, and you can see the
           predictions, and then from there you can see how many
           bills of margin we have to the acceptance criteria. 
           So, they say we are blessed with fat pipe.
                       DR. WALLIS:  How do you measure a minimum
           thickness?  You measure thickness at various places,
           but to get a minimum, you have to measure everybody?
                       MR. MCGEE:  They have several spots when
           they pick a section of pipe, and they have a grid work
           that they work out for the entire pipe basically for
                       DR. WALLIS:  So it covers many, many, many
                       MR. MCGEE:  Yes, hundreds of measurements
           in a small area.
                       DR. ROSEN:  Now, you have a column called,
           "Current Predicted Wear Rate."  And looking at the 10
           inch elbow, it is 5.9 mils per year.  Is that at the
           EPU, or is that prior to EPU?
                       MR. BROWNING:  Correct.  Here is the EPU
           wear rate, a 120 percent prediction.  So you can see
           like we said about 1-1/2 mils in some of the larger
           areas as being --
                       DR. WALLIS:  What was the actual wear 
           rate from the measured values?
                       MR. BROWNING:  This is the last --
                       DR. WALLIS:  Yes, but what was the wear
           rate actually?  Was it much less than predicted?
                       MR. BROWNING:  Yes, it should be
           significantly less, and not having a prior inspection
           before the current one, we don't have that data
           available unfortunately.
                       MR. MCGEE:  But the predictions versus the
           actuals, they do compare those, and they found a very
           good predictability of the wear rate.  So it is very
           close to the actuals that they find in the model.
                       DR. ROSEN:  If you would look with me at
           the 16 inch elbow, what you see is that there are lots
           of margin as you point out, but that the rate for wear
           for the EPU has gone up substantially from 3.6 to 4.9
           mils per year, and that is about a 30 percent increase
           in the wear rate.
                       MR. BROWNING:  Correct.
                       DR. ROSEN:  So it is having a rather
           substantial effect on the feed water piping at these
                       MR. MCGEE:  And not necessarily from the
           flow.  The temperature effect as we have discussed
           previously at the thermal-hydraulics subcommittee,
           depending on where in the pipe the temperature that
           you get the best or the highest wear rate at, the
           temperature may have moved up in the pipe or occurred
           earlier in the pipe now.
                       So this particular pipe might have seen a
           cooler temperature previously, but now because of a
           power uprate and the feed water heating effect that
           you get an increase in the temperature, and thus an
           escalated wear rate associated with that temperature.
                       DR. WALLIS:  Maybe I could point out to my
           colleagues that the NRC is using a proprietary
           description of this, and that does give the predicted,
           versus the observed, in the corrections, et cetera.
                       So many of these questions are addressed
           here, and I don't think it is going to be talked
           about, but it is in this document.
                       DR. SHACK:  Of course, they mis-labeled
           the figures, whether it is an over prediction or under
           prediction.  But we can figure that out.  Now, how
           long is the period between inspections?
                       MR. MCGEE:  Refueling outages
                       MR. BROWNING:  As we try to stretch them
           from an 18 to a 24 month cycle, and we are going to be
           transitioning to 24 month cycles.
                       DR. SHACK:  So you use up about 10 percent
           of your expected margins or something like that?
                       MR. BROWNING:  Yes.  And we will now move
           on.  For the reactor vessel internals, and other
           stainless steel components, those inspection programs
           conform to the recommendations that a boiling water
           reactor vessel internals project or VIP program.
                       So this program directs the scope and
           frequency of the inspections to be performed each
           refuel outage, and DAEC is a leader in the industry in
           implementing the recommended inspection program.  DAEC
           is also a leader in the industry reactor water
           chemistry, and being the lead plant for both hydrogen
           water chemistry with crack or erosion/corrosion
           verification, as well as the application of Noble
                       DAEC has performed two successful
           applications of Noble metals to date.  Because of our
           good inspection results in the past, and by
           maintaining our excellent water chemistry program as
           we move into EP operation, and while we do not expect
           to see any impact on IGSCC susceptible components due
           to the uprate.
                       And while the core power is increasing
           substantially, the increase in fluence on key
           components, susceptible embrittlement or irradiation
           as to stress, corrosion, or cracking, such as the
           vessel walls, core shroud, or top guide, is not
           increasing as dramatically.
                       This again is the influence of the partial
           length full rods in the GE14 design.  And with less
           fission taking place in the upper port of the core,
           where the fluence spectrum is hardest, we minimize the
           impact of the increase in core average power and flux
           profiles on that area of the vessel, and internals
           most susceptible to radiation damage.
                       Thus, we believe that with our aggressive
           monitoring programs for both fact and stress corrosion
           cracking, we will ensure adequate safety and
           operational margins are maintained as we implement the
                       DR. FORD:  My original questions at the
           subcommittee meeting on this particular item really
           related to the fact that the VIP inspection schedules
           and deposition curves for degradation, those latter
           were based on data produced with very low flow rates
           in the laboratory.
                 And so the question really was how would you
           expect those degradation kinetics to increase or
           decrease with flow rate?
                       Now, those are not taken into account in
           the VIP documents, and flow rate is a critical change
           when you go to a power uprate in some components.  So,
           that was the question.  How would the risk increase
           because of specifically flow rate increases?
                       MR. BROWNING:  In most cases -- for
           example, in the core region, the flow rate is not
           going to change at all.
                       DR. FORD:  Correct.
                       MR. BROWNING:  And so in those areas there
           is no change at all.  In the down come region, we are
           getting a slight increase in the drive flow by about
           .3 percent to overcome the delta-P as a result of the
           increase in the power in the core.
                       So we are seeing a slight increase there,
           but that has the most impact on the jet pump
           assemblies, and not so much on the areas that we are
           concerned about for cracking.  
                       Now, those are just long term wear issues
           and vibration issues which we did investigate and
           didn't see any susceptibility there.  And then the
           third area of the vessel of course is in the upper
           region, where the increase in the steam flow rate is
           going up somewhat proportional to the increase in the
           power level, an approximate 16 percent increase in the
           steam flow rate.
                       So we do see an impact in the upper
           regions, but we have investigated those as well for
           the concern of the flow induced vibration issues, and
           also the actual operating experience of those
           components to the chemistry changes that they are in
           so that you don't get quite the same protection from
           the hydrogen water chemistry in that region as you do
           in the lower part of the vessel.
                       So we have seen industry experience with
           IGSCC on those components, and our inspection program
           has factored that in from the GE seal and from the VIP
           recommendations to inspect those components carefully
           for those issues.
                       So that is the way that we have tried to
           address it on our end, is through the inspection side
           of the world to look more carefully, and be more
           cognizant as we move up in the higher flow regimes.
                       DR. SHACK:  And the VIP report on hydrogen
           water chemistry does address flow effects.  Now, you
           may not agree with all of what they say, but they have
           addressed the issue.  
                       DR. FORD:  I was being a devil's advocate
           to a certain extent, because many of these aspects of
           flow rate are well known in the technical community. 
           In fact, generally they decrease the cracking
                       And I just want to make sure that it goes
           out in the public domain that these things have been
           talked about in this committee.  
                       DR. POWERS:  I am going to move this along
                       MR. BROWNING:  We are ready to move into
           the risk perspective.
                       DR. POWERS:  That would be great.
                       MR. BROWNING:  Very good.  I would like to
           now move into the insights that we have learned from
           using our risk assessment tools.  And as we said
           earlier, although our application was not risk
           informed in accordance with Reg. Guide 1.174., we did
           apply our probablistic risk assessment tools to gain
           valuable insights into the possible effects of this
           extended power uprate on the operation of the Duane
           Arnold Energy Center.
                       Although the results of both the Level 1
           analysis of core damage frequency, and the Level 2
           analysis of large early release frequency due to the
           uprate, were not significant as defined by the EPRI
           guidelines for evaluating plant changes.  We did gain
           valuable insights from this exercise.  
                       DR. POWERS:  Did you calculations include
           that extended period of time on any effect that might
           have the -- well, the extended period of time that you
           need the net pressure suction head margin?
                       MR. BROWNING:  I would turn to Brad, our
           PRA expert.
                       MR. HOPKINS:  This is Brad Hopkins from
           NMC.  We do factor in net positive suction head into
           the PRA.
                       DR. POWERS:  In the interest of time that
           you need that, that enters into the --
                       MR. HOPKINS:  In the Level 2, yes, we are
           looking at a 24 hour period after the start of the
           event.  So, yes, we do factor in the likelihood of
           pump failure due to inadequate net positive suction
                       CHAIRMAN APOSTOLAKIS:  What kinds of
           uncertainties do you have there?  I mean, you say 1.55
           and 10 to the minus 5.
                       DR. POWERS:  That is very accurate,
           George.  That is precise.  
                       CHAIRMAN APOSTOLAKIS:  This is 10 to the
           minus 5.
                       MR. HOPKINS:  This is Brad Hopkins again. 
           We have not performed a detailed uncertainty analysis
           for the PRA.  We addressed uncertainty in our initial
           IPE submittal, with a sensitivity analysis, and for
           the present power uprate study, we started the study
           by selecting sensitive parameters, and sensitive
           operator actions, and sensitive components.
                       CHAIRMAN APOSTOLAKIS:  Well, Regulatory
           Guide 11.74 requires the use of mean values.  And you
           don't know that these are mean values do you?
                       MR. BROWNING:  Right.  But as we said,
           what we are looking for is insights.  We are not
           looking for a specific precise calculation of what the
           actual core damage frequency is.  We are just looking
           for changes and what drives those changes to look for
           the insights.
                       CHAIRMAN APOSTOLAKIS:  And what are you
           going to do with the insights?
                       MR. BROWNING:  Well, first, and most
           importantly, no new risk vulnerabilities were
           identified in initiating event frequencies, component
           reliability, or key success criteria.  This is because
           sufficient plant operating margins will be maintained
           during the implementation of the uprate either through
           inherent design margin, or modification to equipment,
           such that the plant's overall reliability will be the
           same as before.
                       The one area where we did see an impact to
           the uprate was in the event timing, and in particular
           where operator actions are important to success,
           almost all of the change in core damage frequency and
           large early release frequency is due to changes in
           human error probability.
                       And especially in those events where there
           is heavy reliance on operator actions, such as ATWS. 
           As you heard earlier in Ron's presentation, we use
           this insight to tailor our operator training in both
           the classroom and dynamic simulator scenarios to
           ensure that the operators would continue to respond
           successfully in these events after the uprate --
                       CHAIRMAN APOSTOLAKIS:  I am just curious. 
           Suppose that PRA never had been abandoned, and you
           were following the strict traditional deterministic
           licensing approach, would this issue of operator
           actions come up here?
                       Is there a part there that says to
           calculate the time for operator action?
                       MR. BROWNING:  It may not have been so
           much driven by time, but I think as we would have gone
           through the exercise of looking at the deterministic
           evaluations, we would have also in parallel been
           looking at the impacts in the emergency procedures
           that the operators have to follow.
                       And from that side of the world, we would
           have driven probably the similar conclusion that there
           are certain key actions in the emergency procedures
           that are important for the operators to take in a
           timely manner in order to be successful.
                       So I think we probably would have come to
           a very similar conclusion in this case, because ATWS
           drives both of those, and what we are seeing here is
           a corroboration of that knowledge.
                       DR. POWERS:  I think it is a most obvious
           conclusion when you say Dana Powers is going up, and
           you say, well, since the plant is kind of fixed,
           operator response time is going to be shorter just
           because of higher power.
                       MR. BROWNING:  Especially by those things
           that are driven by decay heat.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       DR. POWERS:   And I will just interject
           here.  George, you didn't get to attend the
           subcommittee meeting, but you might want to look at
           some of the notes on that, because one of the things
           that they did was use the PRA to look at all of their
           operator actions and get a raw on them on risk
           achievement work.
                       And then that gave them a prioritization
           to go through and look at them, and I thought it was
           a fun thing to look at.  
                       MR. BROWNING:  Right.  And back to what
           Brad was talking about with respect to sensitivity
           cases as well.  We also went back and looked at those
           operator actions that were below the raw value of
           1.06, and did some sensitivity cases there as well to
           make sure that we weren't missing anything by setting
           a screening criteria in appropriate levels.
                       So we look at all actions underneath that
           screening criteria, and made some adjustments there in
                       CHAIRMAN APOSTOLAKIS:  Do we have these
                       MR. MCGEE:  I can get you a copy, George.
                       DR. KRESS:  In the subcommittee, we asked
           what delta-CDF meant and the raw value corresponding
           to it, and at one time I believe it was 1 times 10 to
           the minus 6.
                       MR. BROWNING:  Right.  
                       DR. KRESS:  I thought I remembered that.
                       DR. ROSEN:  Here you have only discussed
           a couple of the operator actions that were actually
           examined and reported to the subcommittee.  I think
           there were a half-a-dozen key operator actions that
           were examined.
                       Some of them, you know, have fairly longer
           times available than the particular one that we
           focused on here, which was the initiation of standby
           liquid control within ATWs, which goes from 6 to 4
                       But there are others described there,
           took, George, that are not -- well, that one is the
           most severe and the largest change.
                       MR. BROWNING:  There were four key actions
           that really came to the top of the list, and three of
           them were driven by ATWS; and then the last one was
           transients where the reactor stays at high pressure,
           and the need for the operator to respond to pressurize
           the vessel in a timely manner to get low pressure
           ejection on it.  And those were the key operator
           actions that we learned from the PRA.
                       DR. POWERS:  I am going to move you along
           on this.  We can talk PRA for a long time.  
                       MR. BROWNING:  And that is pretty much the
           conclusion that we came to, and the insights that we
           gained from the PRAs, and with that, that concludes my
           portion of the presentation, and I am going to turn it
           back over to Ron now.
                       CHAIRMAN APOSTOLAKIS:  I am very curious
           about how you quantified this thing.  You have a
           number of the available time that goes down from 6
           minutes to 4 minutes, and the failure probability
           increased from .11 to .18.
                       Now given the state of the art in these
           things, this is really noise.  
                       DR. POWERS:  Well, I think that the issue
           is bigger than that, George.  I don't think that the
           change from .1 to .18 is what is striking.  What is
           really striking is that we have a relatively high
           probability of human error here, but we have a
           database on simulator training where their rate after
           50 or 58 tries, I believe, is zero.
                       CHAIRMAN APOSTOLAKIS:  Yes, and that's why
           I am curious.
                       DR. POWERS:  And that is what is striking.
                       CHAIRMAN APOSTOLAKIS:  And how old is the
           methodology, and how all that stuff comes together. 
           It must be somebody's judgment at the end.
                       MR. BROWNING:  I think that is a great
           deal of it, and it comes down to expert panel type
           judgments, where you have a number of people sitting
           down and looking at video type of operator
           performance, and doing the calculations, and factoring
           all those pieces together to arrive at a conclusion.
                       I don't think it is strictly driven solely
           by any one aspect.  You are trying to model something
           that is very complicated, and so you are trying to use
           as much input as you can from diverse sources and
                       CHAIRMAN APOSTOLAKIS:  So if you were to
           draw on uncertainty as an analysis to this, the .11
           could be as high as .6?
                       DR. WALLIS:  No, no, no, George.  It is a
           change, George, that they are talking about.
                       CHAIRMAN APOSTOLAKIS:  No, it's not.  They
           are talking about increased from .2.
                       DR. WALLIS:    Yes, but it is only
           influenced by one small thing, and the change --
                       CHAIRMAN APOSTOLAKIS:  It was .11.
                       DR. WALLIS:  The change is what they are
           talking about.  The change is much more precise than
           the uncertainties, and these absolute values.
                       CHAIRMAN APOSTOLAKIS:  The change is more
                       DR. WALLIS:  Yes.
                       DR. POWERS:  I think it is one of the
           esoterics of human error reliability that will arise
           in our November meeting.  I need to move us along
                       DR. WALLIS:  Could you bring up your
           number seven very quickly for one minute, the number
           seven slide.  There is something different about your
           slide and mine, and I just think for the record that
           the arrow in my slide points to the blue line, and
           whatever is going to go into the record should be the
           right slide, which may be a copy of this one.  Thank
                       MR. MCGEE:  Unless there are any other
           questions, and I heard no open items for us, then in
           conclusion the DAEC believes that our submittal has
           shown that EPU will result in only a minimal increase
           in risk, and that a substantial margin of safety will
           be preserved. 
                       The conclusion was confirmed by the NRC
           staff's confirmatory analysis, and a review of
           calculational results, on-site audits of design record
           files, and our responses to many requests for
           additional information.
                       As reflected in the draft SER, after
           scrutinizing our limited deviations from previously
           approved methodology and in general, a healthy
           questioning attitude during its review of our
           submittal, the NRC has confirmed our view that the
           proposed power uprate complies with NRC regulations. 
                       And that there is reasonable assurance 
           that public health and safety will be protected.  We
           believe the rigor with which we prepared our submittal
           and the thorough NRC staff review have demonstrated
           that operation at the uprated power level is
           acceptable.  We thank you for your time and attention
                       DR. POWERS:  Are there any other questions
           for the applicant?  If not, Ron, I thank you for your
           presentation, and I will call on John Zwolinski to
           begin the staff presentation.
                       MR. ZWOLINSKI:  Dr. Powers, thank you for
           recognizing me and our staff is prepared to go
           forward.  Good morning to all of the members.  For the
           record, my name is John Zwolinski, and I am the
           Director of the Division of Licensing Project
           Management in the Office of Nuclear Reactor
                       During last week's ACRS Thermal-Hydraulic
           Subcommittee meeting, we made a presentation on our
           review of the Duane Arnold  extended power uprate.  
                       I am here for two reasons.  One is to
           represent senior management and the support of our
           staff, and secondly, to emphasize that the staff has
           conducted a thorough review in all areas potentially
           affected by this power uprate submittal.
                       The staff conducted its review consistent
           with existing practices, including the lessons learned
           from Maine Yankee.  If you recall when I briefed the
           subcommittee a few months ago, I went into great
           detail on lessons learned from Maine Yankee.
                       I did not intend to repeat those.  I did
           want to take just a couple of minutes to reflect on
           the process.  I also reflect that Dr. Powers did
           allude to the staff diving deeply into certain review
           areas, and highlighted a couple of those that we
           intend to speak to specifically today.  
                       Those are ATWS, fatigue containment, and
           things of that nature, but as a general reminder our
           staff did undertake this activity using template
           reviews.  We relied on our standard review plan. 
           There was an extensive effort that our staff undertook
           to ensure that we crossed all the T's and dotted all
           the i's.  
                       We got into the field as you have heard
           with General Electric and with the licensee.  Our
           senior staff and management team that is here today
           have been deeply involved with this activity.  
                       We have relied heavily on GE topical
           reports that have been reviewed and approved, and
           presented to this committee in days go by.  And
           management and the Division of Engineering, through
           Jack Throwsnider in the Division of Systems Safety,
           and through Gary Hallahan, as well as in projects
           myself, have all been deeply involved to ensure that
           this project moves on smartly.
                       DR. WALLIS:  This SRP is not specifically
           for uprates is it?
                       MR. ZWOLINSKI:  That's correct.  It is for
           individual sections or topics within various chapters
           of the standard review plan.  Although we reviewed the
           information in many areas and on a licensing basis of
           the Duane Arnold plant and beyond by use of risk
           information, we will focus our presentation today on
           the areas that we believe to be the most interesting
           to the power uprate.
                       And we will also address the areas that
           the ACRS expressed interest in.  I would like to now
           turn to our project manager, Brenda Mozafari.  We are
           essentially prepared to give about five minutes of
           presentation each, and we will try to move quickly,
           but obviously we want to take questions as
                       MS. MOZAFARI:  Good morning.  My name is
           Brenda Mozafari.  I am the project manager assigned to
           the Duane Arnold at NRR, and I am going to tell you
           briefly what our agenda is.  
                       We have received the open remarks from
           John Zwolinski, and I am going to provide an overview
           of how the staff proceeded in their reviews.  
                       The NRC staff evaluation is going to be
           presented in large part by Ralph Caruso, who is going
           to address the reactor fuel performance and in GE
           audits that were performed to assist in the review.
                       Kamal Mandly is going to present some
           information on the cumulative usage factors, and we
           are going to have Rich Lobel present an evaluation or
           the staff's evaluation of the containment response
           evaluation by the licensee, and then John Zwolinski
           will give some concluding remarks.
                       Okay.  I think it is important to note
           that the staff started out with a submittal by the
           licensee that was provided to us within the guidelines
           of ELTR-1 and ELTR-2 as the framework for the review. 
                       The Monticello -- we previously approved
           the Monticello safety evaluation as more or less a
           template to kind of guide where the emphasis would be
           put in the reviews and the depth of the reviews, and
           plant specific design differences were addressed
           within our draft of safety evaluation which you have
                       Several additional submittals of
           information were provided following teleconferences to
           support NRC staff reviews.  Now, in this I would like
           to speak a little to this streamlined RAI process that
           encouraged questions by our staff.
                       Although we have many additional
           submittals of information along the way that we felt
           were necessary to put on the docket, there were a lot
           of telephone calls where we got clarifications to make
           sure that we truly understood how the licensee
           remained within the bounds of the generic topicals and
           the analyses, and to make sure that we understood the
           manner in which they performed calculations.
                       We were building our lessons learned from
           previous uprates, and the licensee did make a
           submittal that was informed by previous RAIs that have
           been done on Monticello and Hatch,a nd tried to
           address those up front, and provided us with detailed
           lists of methodologies.
                       DR. WALLIS:  I guess the streamline
           process also allowed enough time to analyze the
           answers to the questions, as well as allowing you to
           pose questions?  
                       MS. MOZAFARI:  Right.  And it allowed us
           to have a good interchange of information to make sure
           that there was true understanding.  Statistically, we
           ended up with a 120 page application that the licensee
           submitted, which resulted in about 3,000 -- it will be
           in excess of 3,000 staff review hours.
                       And we incorporated the staff review hours
           and the inputs into approximately a hundred page draft
           safety evaluation, which we did provide you.
                       And it is a work still in progress and we
           recognize that it had a few quirks, but the outcomes
           or the conclusions would not change.
                       CHAIRMAN APOSTOLAKIS:  I was not present
           at the subcommittee meeting, but I am trying very hard
           to understand what these statistics are telling me. 
           More than 3,000 review hours.  Okay.  So what?  I
           mean, what does this prove?
                       MS. MOZAFARI:  The staff will go into
           that.  What I am trying to say is that it wasn't a
           cursory review, where we just looked briefly at the
           submittal and said, oh, they need the generic
                       We did go into -- and I will outline what
           was done to substantiate what the licensee provided. 
           The review questions came from eight different
           branches within the NRC, and there were 26 written
           responses, and we had three general meetings with the
           entire review staff.  
                       I would like to show you just briefly the
           scope of the review.  We did review -- and you can
           read them -- in all these areas involving these
           different branches, and from those branches, we
           gleaned the fact that we had three characteristic
           types of ways that we would evaluate things.
                       Site audits were performed by the reactor
           systems group, and we reviewed specific calculations. 
           For example, electrical and stress calculations, and
           Kamal Mandly is going to demonstrate the kind of
           stress calculations we have looked at, and we did
           confirmatory analyses, particularly in the containment
           systems area.
                       And with that, I will turn it over to
           Ralph Caruso, who is a section chief on the BWR
           systems and nuclear performance section to present the
           field specific issues.
                       MR. CARUSO:  Good morning.  This is an
           introductory, and this is who I am.  I don't have a
           lot of slides this morning, and I am going to be doing
           mostly talking from this one particular slide.
                       The staff review of the power uprate for
           Duane Arnold was quite involved.  This was a
           significant review because the power level increase
           that was requested was above any power level increase
           that had been granted before.
                       Before we started the review, we had lots
           of meetings with the Duane Arnold people, and I
           believe they even came in and talked to the ACRS
           before the application.
                       And one consistent question that came up
           during this time is how can you do this.  How can you
           raise the power level in this reactor by 20 percent
           and not change the pressure.  Aren't all sorts of
           things going to change, and how do you do this.
                       There was just a lot of incredulity
           expressed by a lot of knowledgeable engineers about
           how you could do this.  Well, we talked to GE about
           this, and it turns out that the way they actually did
           it when it comes down to looking at the course is
           pretty simple.  
                       They flattened the flux shape in the core. 
           They got the peak bundle constant and they raised the
           average bundle power, and that is a pretty simple
           thing to do.  
                       I mean, it requires some sophisticated
           engineering by GE to do core design, but when you look
           at it, fundamentally it is pretty simple, and they
           were able to accomplish this within the existing
           analysis methods that have been used over the years to
           evaluate the performance of BWRs.
                       Now, that is what I am talking about when
           I say in this first bullet that approved methodologies
           were used for the safety analyses.  BWRs are nice
           machines.  I wasn't originally trained on them, but I
           have grown to appreciate them over the years.
                       They are basically channel reactors, and
           they scale very well, and the analysis methods are
           pretty simple because they just boil water. They don't
           have these strange steam generators and funny loops
           and stuff.  
                       So if you can figure out a way to define
           the flux shape and stay within the limits for the
           individual channels, you can raise the power levels
           with a reasonable amount of effort, and the staff
           review of this reactor looked at these methodologies
           to make sure that they were being done in accordance
           with those methodologies.
                       DR. KRESS:  And you get an increased steam
                       MR. CARUSO:  That's correct.
                       DR. KRESS:  And how do you maintain your
           pressure constant with that?
                       MR. CARUSO:  How do you maintain --
                       DR. KRESS:  The head pressure being
                       MR. CARUSO:  Well, the reactor pressure
           remains the same.  The pressure in the reactor vessel
           remains the same, and you open the valve at the other
           end a little bit more, and you redesign that valve,
           and you redesign the turbine so that you can get more
           steam flow.
                       DR. KRESS:  So you redesign the turbine
           and the control valves?
                       MR. CARUSO:  Yes, but you maintain the
           steam pressure in the reactor constant, and that makes
           a lot of other things a lot simpler.
                       DR. KRESS:  So it is not just simply a
           flux flattening.
                       MR. CARUSO:  I understand that, but I
           think -- I started this because that was one of the
           big questions that came up in the beginning was how
           can you do this.  People were just incredulous that
           you could do this.  And I have got to give GE credit
           for this.  They were very clever.
                       DR. WALLIS:  So how do you know the flux
           is flat when you are doing all this rod stuff and the
           operation.  Do they measure the flux profile in some
                       MR. CARUSO:  There are surveillance
           requirements for operators to periodically measure
           flux distributions, and to ensure that the reactor is
           operating within the analyzed limits.  Those are
           important not just for safety purposes, but for
           economic purposes.
                       DR. WALLIS:  So they actually measure the
           flux distribution?
                       MR. CARUSO:  Yes.
                       DR. WALLIS:  Thank you.
                       DR. KRESS:  You would have a real problem
           getting another 20 percent increase.  You have already
           flattened the flux about as much as you can do it.
                       MR. CARUSO:  I don't know.  I don't want
           to speculate on that.  I mean, I don't want to
           foreclose the skills of GE's engineers.
                       DR. POWERS:  Well, I don't think we should
           take the view as this being a very simple change
           because of some generic feature of the BWR.  The fact
           of the matter is that actually the boiling water
           reactor is fairly complicated.
                       MR. CARUSO:  I would not disagree with
                       DR. POWERS:  You have the void and
           reactivity are coupled, and in a fashion that
           inherently makes this system non-linear.  So
           stability, which we can analyze in a linear fashion,
           becomes complicated when you are working with a non-
           linear system.
                       MR. CARUSO:  I understand that, Dr.
           Powers, and I think I will be addressing some of this
           in my fourth bullet.  
                       DR. POWERS:  Will you be able to tell me
           where I can go to look and see if in fact 1-D is
                       MR. CARUSO:  Right here.  And I have got
           someone on the staff here.
                       DR. POWERS:  So I will be able to look at
           differential equations and see IKON values?
                       MR. CARUSO:  I am not so sure about that,
           but maybe I can point you in a direction.
                       DR. POWERS:  Somebody I would hope would
           point me, because I would really like to see the
           differential equation analysis with this core, with a
           flat and flexible --
                       CHAIRMAN APOSTOLAKIS:  The stability
           analysis --
                       MR. CARUSO:  Well, let me think about
                       DR. POWERS:  Quite frankly, the stability
           analysis has been done with enormously complicated
           equations and are actually fairly simple equations.  
                       MR. CARUSO:  So I am starting out with the
           point that the licensee used approved methodologies;
           the SAFER/GESTR methodology for LOCA analyses, and
           TRAC-G for stability, and ODYN I guess is one of the
                       There are a number of methodologies that
           are used for various different Chapter 15 analyses. 
           This brings me to my second point, which is the
           licensing limits for these analyses were retained.  
                       The 2200 limit that is in the regulation
           for LOCAs is still there, and the license showed you
           that they continue to meet the 2200 limit.  They
           continue to meet the 1600 limit, the additional 1600
           limit that is in the SAFER/GESTR methodology.
                       They continue to meet the 99.9 percent of
           all rods do not undergo boiling transition, which is
           the standard for AOOs.  They continue to meet the ATWS
           SLC injection requirements that are in the regulation.
                       They continue to meet the subsidiary
           requirements int he ATWS analyses that they don't
           exceed the 2200 degrees and the field geometry limit,
           and the containment pressure limits.  All of those
           limits are retained. 
                       DR. WALLIS:  And these are all based on
           calculations done by the licensee?
                       MR. CARUSO:  Yes, or its contractor,
           General Electric.  And given the increase in power,
           and the amount of the increase in power, the staff
           decided that as part of its review to go out and
           actually do an audit of these calculations.  
                       We sent a team of four or five people to
           GE-Wilmington for a week, and they went through the
           detailed design calculations for this plant for a
           number of these transients and accidents in order to
           satisfy themselves that the methodologies were being
           appropriately applied, and that the results were
                       During the course of that review, that
           audit, we found a few problems with some different
           aspects of the GE methodology that we described and
           discussed with the subcommittee, and I think that we
           discussed several months ago.
                       And that was useful.  We found that
           useful, and GE has resolved those issues, and we don't
           think they stand in the way of this power uprate. 
                       So based on the fact that they are using
           the approved methodologies, and that they meet the
           licensing limits, and which hasn't changed -- and I
           brought that point up because there were some concerns
           that we might have changed something like the fuel
           burn up limit.  
                       There is no change to the fuel burn up
           limit.  There were concerns that because it was a
           power uprate that the fuel would be burned to a higher
           level, and therefore, it would be in some sort of a
           weakened state.  
                       And the answer is, no, it's not.  The fuel
           is being burned within the limits of the methodology. 
           So those concerns turned out to be not well-founded,
           and based on the use of these methodologies, and the
           audits that we did, and the reviews that we did in-
           house, we believe that this is a fully-justified power
                       Now, the last bullet concerns ATWS issues. 
           There were several ATWS issues that came up during the
           subcommittee meeting.  One concerned -- I thought it
           was Dr. Powers's radio peaking factor, and whether the
           flattening of the flux shape resulted in a core that
           was different than what was actually analyzed as part
           of the ATWS stability bounding calculations.
                       And in talking to GE, we discovered that
           indeed it is bounded by the analyses that were done
           back then, and that flattening the flux shape does not
           invalidate those analyses.  I think today that you had
           a question about an axial power shape.
                       DR. POWERS:  Axial power shape comes up in
           the ATWS recovery.
                       MR. CARUSO:  Okay.
                       DR. POWERS:  The first one that you are
           raising I guess -- well, that was one of the
                       MR. CARUSO:  Well, I can show you a power
           -- well, I don't want to get too complex, but there is
           a concern about operating at the MELLLA point, and
           comparing the new operation at this MELLLA point here
           to the original license value, and whether the core
           state would be somehow different, and therefore
           whether the bounding analyses didn't apply.
                       And GE talked about this at the
           subcommittee meeting; that in any case, if you have an
           ATWS and you don't do any mitigation, in both cases
           the reactor ends up at the same stay point, which is
           inside the instability region.
                       So the initial conditions are essentially
           the same for instability.  And therefore this
           operation at this higher value is bounded by the
           original bounding analysis.  
                       And in actual point of fact, when you look
           at ATWS and you look at the mitigation that occurs,
           the plants don't go to that particular state point,
           they actually drop down further on a natural
           circulation line.
                       So we would expect that they would not end
           up inside that instability region.  The analyses
           aren't --
                       DR. WALLIS:  There is extra steam in the
           lower level that reduces the power.
                       MR. CARUSO:  That's correct.  That's
           correct.  When you reduce the water level, you will be
           reducing the reactor power.  Now, you had a concern
           this morning -- 
                       DR. WALLIS:  That is below the stability
                       MR. CARUSO:  I don't show the stability
           region here, but just looking at it and eyeballing it,
           I believe it is below the instability region.  Now,
           you had a concern this morning about I believe decay
           heat in the upper part of the bundle if you had
           started with a core that had a top skewed power shape.
                       DR. POWERS:  The question really is does
           the -- well, when we looked at the ATWS recovery, part
           of that involves bringing the water level so that the
           collapsed level is below the top of the fuel.
                       MR. CARUSO:  Right.
                       DR. POWERS:  The staff resisted that
           substantially when we discussed the recovery sequence,
           or when it was first being considered.  We have
           actually agreed to that because there was adequate
           steam cooling of the top of the core. 
                       That was with an unflattened power profile
           in the core.  The question is that now that we have
           flattened it, we have raised the amount of heat that
           is available in that upper part of the core.
                       The staff is still comfortable with
           dropping the collapsed water level below the top of
           the core, and why?
                       MR. CARUSO:  Okay.  I have one of my staff
           members here, Tony Ulyses or one of my former staff
           members.  He now works for the Office of Research
           here, and he can talk about this a little bit.
                       MR. ULYSES:  Yes, my name is Tony Ulyses,
           and essentially, Dr. Powers, the question boils down
           to the fact that when the water level was originally
           developed -- and again this is referred to as the
           minimum steam cooling reactor water level.
                       It was derived with the assumption of a
           top feed axial power distribution, which at the time
           was obviously not realistic, but it was done in order
           to bound any future operations.
                       And that power distribution will continue
           to bound the current operational strategies that are
           being used right now and at the power uprate
                       DR. POWERS:  And where do I find in the
           safety examination that the staff has done the
           discussion that the staff looked at the flattened
           power flow profile, and found that indeed it was
           bounded by the original analyses and that the ATWS
           recovery sequence was still applicable?
                       MR. ULYSES:  In the SER that you are
           looking at right now, the draft SER?
                       DR. POWERS:  Yes.
                       MR. ULYSES:  I would say probably nowhere,
           having not actually written it myself.  
                       MR. CARUSO:  Off the top of my head, I
           don't know that we explicitly addressed that
           particular issue.
                       MS. ABDULLAHI:  If I may interject.  I
           actually did the review for --
                       MR. CARUSO:  Introduce yourself.
                       MS. ABDULLAHI:  I am Zena Abdullahi,
           Reactor Systems Branch.  Dr. Powers, the submittal
           itself did not actually consider or address
           instability, because instability is considered by the
           industry at large as a closed issue.
                       However, due to the concerns of the ACRS,
           I did go through and looked at these topical reports,
           and see if it is bounded.  And I think that Mr. Caruso
           has sections of it in which it talks about the power
           shape in the topical reports itself.
                       What the draft SER basically says is that
           we have not received any analysis, for specific
           analyses, for instability, for ATWS instability, for
           Duane Arnold.  That's number one.
                       And, number two, we expect as an Option 1-
           D plan if in fact you have the transients that create
           the potential for instability, and that they would end
           up being or have the potential for core-wide
                       Having core-wide instability, they would
           take the mitigating factor, the mitigating steps, for
           SLC introducing water level, and the analysis that was
           done, could it be bounded for Duane Arnold.
           And operators would also get -- in other cases, the
           alarms would let the operators know that they are
           experiencing -- the plant is experiencing instability.
                       DR. POWERS:  I bet you when they go into
           instability that there is a whole lot of information
           going to the operators telling them that things are
           not quite right.  The question is whether the recovery
           process still going to work.
                       MS. ABDULLAHI:  There are a couple of
           things that I could point out basically from the top
           of my head right now without getting to you with the
                       DR. POWERS:  Well, what was in the part of
           the examination.
                       MR. CARUSO:  I am looking at the draft SER
           here on page 60, and it is the section that talks
           about aspects of ATWS instability and the EPU reports. 
           It talks about operator actions to mitigate ATWS
                       And the staff made a conclusion that the
           mitigating actions that the plant will take with
           regard to ATWS instability are exceptional.  We make
           that statement there.  Is it your concern that we did
           not specifically say --
                       DR. POWERS:  Well, when I read statements
           like that, I am not sure what you did.  So, I am just
           asking.  It just seems to me that when somebody comes
           into me and says I am going to do something to a BWR,
           almost the first question that comes to mind is ATWS,
           and the second question is ATWS recovery.
                       It seems like maybe it peculiar to me, but
           those are the things that I promptly think about, and
           I am asking what was done with the recovery sequence. 
           I think the previous speaker said that she looked at
           it, and that is just is not something to worry about,
           and I am willing to accept that.
                       MR. ZWOLINSKI:  And it would strike me,
           Dr. Powers, that would be the type of issue that we
           would consider as follow to put in the final safety
                       DR. POWERS:  There has got to be something
           more than we looked at it and everything is okay.  
                       MR. ZWOLINSKI:  I understand your point.
                       DR. SHACK:  There is another peculiar
           sentence in the SER on page 61 that says that the
           staff realizes that the EPU safety analysis did not
           include a review of the applicability of the generic
           instability analysis specified in EPU operation
           involving a high density core MELLLA and GE14 fuel
                       And my question is why didn't you?  I
           would have thought that was the number one item to be
                       MR. ULYSES:  Actually, Ralph, I can
           probably answer that question.  Essentially, if you
           look at the instability mitigation strategies which
           have been approved, they are intended to be reactor
           design specific, and at the time of the submittal we
           didn't have the actual specific reactor design to go
           to the EPU conditions.
                       But that will be dealt with during the
           reload calculational phase.  What we did do was we
           looked and we considered the applicability of Option
           1-D, and we actually looked at the calculations which
           were done by GE on our staff audit, and which was done
           on what they called a representative core.
                       In other words, it is not the actual
           reactor that they are going to be running, but it was
           a representative core to demonstrate that they will
           continue to be able to use Option 1-D.
                       Essentially, they show that there is a 
           -- that the core-wide instability mode will continue
           to dominate.  And all these calculations for reactor
           instability based on the GE methods are done with
           frequency domain methods.
                       In other words, they are calculating
           basically to K-ratios.  So they are not looking at
           these instabilities in a time delay domain.  They are
           not using the TRAC code, for example, and those are
           not being used in this case.  
                       And those calculations were examined and
           they were looked at, and there was a finding basically
           that, yes, that basically from what we see right now,
           we can conclude that they will continue to be able to
           use Option 1-D.
                       However, it will have to be confirmed on
           a cycle-specific basis, and that is the methodology
           which is approved now, and that is the methodology
           which will continue to be used in the future.
                       DR. WALLIS:  I have a question, and maybe
           it is for management.  When we read these SERs, we
           read the issues and then we reach the bottom line,
           which as the staff stated is that this was acceptable
           or something like that.
                       And then we hear in these presentations
           that actually there is a technical basis for this. 
           Isn't there a paper trail somewhere where the staff
           actually records the technical basis for accepting
           these particular calculations by a licensee, whatever
           the issue is?
                       MR. CARUSO:  It depends on the issue.  I
           mean, the staff reviews -- well, we accept things
           based on doing our calculations, which leaves a paper
           trail, and by looking at the actual calculations that
           the licensee does step-by-step.
                       DR. WALLIS:  Well, if we are curious can
           we find that paper trail?  Can we follow it?
                       MR. CARUSO:  Sometimes, but realize that
           a lot of the time that staff decisions are judgment
                       DR. WALLIS:  Well, that is what bothers
           me.  I mean, where is the part that was reassuring
           when there was a technical analysis before.
                       MR. CARUSO:  But in the end what it
           absolutely comes down to is I have knowledgeable
           engineers on my staff, and I count on them to have
           good judgment.  That is what it comes down to. 
                       We don't have black and white criteria for
           a lot of these things, because they are judgment.  I
           mean, I sit here and I listen to all 12 of you, and
           you don't have black and white criteria.  And you
           disagree very frequently about what those criteria
           should be.  The staff is in the same position.
                       MR. ULYSES:  Let me jump in here and say
           that one thing that we can do when the staff reviews,
           Dr. Wallis, is that we can look at the application of
           an approved methodology, and when we  do the review,
           we confirm that the methodology will remain
                       But that is something that we can do that
           is black and white, and that is one thing that is
           done, and that is something that was done in this case
           as well.
                       MR. CARUSO:  Okay.  One last item that you
           have on that was concern of the operator response
           times, and Dick Eckenrode from the staff is able to
           address that.
                       MR. ECKENRODE:  First of all, are there
           still concerns about operator response time?  
                       DR. POWERS:  You betcha.
                       MR. ECKENRODE:  I am Richard Eckenrode
           from the operator licensing and human performance
           staff.  As part of the human performance review, we
           examined all of the risk important operator actions
           identified by Duane Arnold as being affected by the
           power uprate.  
                       There were five actions which in time
           available the operator complete the action was
           reduced.  Initiation of standby liquid control in the
           ATWS events is the most limiting time dependent
                       The time available to avoid emergency
           depressurization will be reduced from 6 to 4 minutes. 
           The staff requested Duane Arnold to prove or provide
           evidence that the operators could perform this action
                       This is a critical task in the operator
           requalification training and testing program.  An
           examination of the last four years of regular test
           results showed that the ATWS scenario was exercised 58
           times, with 100 percent success.
                       Since the ATWS EOP says to initiate SLC
           based on suppression pool temperature approaching the
           boron initiation temperature, it is not based on time.
                       CHAIRMAN APOSTOLAKIS:  Well, let me
           understand this.  It was exercised 58 times you said?
                       MR. ECKENRODE:  Yes, over the last four
                       CHAIRMAN APOSTOLAKIS:  And when you say
           successfully, you mean it was completed within how
           much time?
                       MR. ECKENRODE:  That task -- that was what
           I was just about to say now.  The task was not timed. 
           The reason it was not was because the EOP indicates
           that you want to do it before the suppression pool
           temperature approaches the byte temperature. And so it
           is not a timed item.  You are watching the suppression
           pool temperature increase.
                       CHAIRMAN APOSTOLAKIS:  But that must have
           something to do with the 6 and 4 minutes?
                       MR. ECKENRODE:  Correct.
                       CHAIRMAN APOSTOLAKIS:  So is it correct to
           assume that it was done successfully within 6 minutes
                       MR. ECKENRODE:  Obviously, yes. 
                       CHAIRMAN APOSTOLAKIS:  And what does that
           tell us about our ability to do it within 4 minutes? 
                       MR. ECKENRODE:  I have that, too, and am
           coming to it.  In fact, that is the next statement
           really, is that it was estimated in those runs that
           the action takes about 10 to 15 seconds.
                       DR. BONACA:  It is not the action itself
           it seems to me.  It is deciding to do it.
                       MR. ECKENRODE:  It is the decision, right;
           the decision to do it, yes.
                       DR. BONACA:  It took 10 seconds? 
                       MR. ECKENRODE:  No, the action takes 10 to
           15 seconds.  The decision is simply as the two
           temperatures approach each other.  Again, it is not a
           timed decision.
                       DR. BONACA:  So what you are saying is
           that they really don't look at their watch.
                       MR. ECKENRODE:  That's correct.
                       DR. BONACA:  It's just that this
           temperature is approaching, and then we trust that as
           this temperature approaches this particular limit,
           even within a minute, they will react appropriately?
                       MR. ECKENRODE:  Correct.  Correct.
                       DR. BONACA:  Which is a significant
           assumption here is it not?
                       MR. ECKENRODE:  Yes.
                       DR. BONACA:  I mean, you are saying that
           this is really the driver.  They see the temperature
           going up, and whether it goes up in 10 seconds or 3
           hours, they are going to do the right thing.  And that
           is exaggerating a little bit, but not much. 
                       MR. ECKENRODE:  At the high power levels,
           in which most of these were run, the time that you are
           talking about here is what is the 4 minutes.
                       CHAIRMAN APOSTOLAKIS:  But the four
           minutes is from the initiation of the ATWS event, and
           not from the moment in which the temperature reaches
           the point?
                       MR. ECKENRODE:  That's correct.
                       DR. BONACA:  And the question I have is
           how long does it take from the beginning of the ATWS
           event to the point where the temperature reaches that
           point, and the operator takes the action?
                       MR. ECKENRODE:  At the high power level,
           it used to be six minutes.  
                       CHAIRMAN APOSTOLAKIS:  So, six minutes,
           and now it is four.  
                       DR. BONACA:  Okay.  I understand now.  All
                       CHAIRMAN APOSTOLAKIS:  So they have to
           decide to do it, and then do it within that period of
                       DR. BONACA:  And then do it within 15
                       DR. ROSEN:  They have four minutes to do
           it, but once they have decided the question of
           actually initiating it, that takes 10 seconds.
                       DR. POWERS:  And as was said that is
           hardly the issue.  Let me ask you another question. 
           The licensee came in with their analyses and found
           five critical operator actions.  When you looked at it
           independently did you confirm that there were just
           five to look at, that merited being looked at?
                       MR. ECKENRODE:  No, I did not do that. 
           The risk people did that, I believe.
                       MR. HARRISON:  This is Donnie Harrison,
           and I am in the PRA branch.  What we did was after the
           licensee submitted their information, they identified
           five operator actions that had a raw value above 1.06,
           which as we talked about before was equivalent to a
           CDF impact if you assume that operator action failure
           is 10 to the minus 6 core damage frequency increase.
                       What we did was that we went back to the
           licensee and asked them if there were operator actions
           that were below that criteria that may if you were to
           look at combinations become more important, and the
           licensee came back and identified one additional
           operator action that was a little bit below the
                       And its impact was identified that if you
           assumed it failed as an impact on core damage
           frequency of 5 times 2 to the minus 7, they also then
           went back into all of their operator actions that were
           screened out, and they doubled their operator action
           failure rates.
                       DR. POWERS:  What I am asking really is
           you found their case so persuasive that you felt there
           was no need to independently look at those?
                       MR. HARRISON:  What I would say is that
           first of all the PRA part of this is confirmatory to
           gain insights.  It is not the basis for the decision
           making process.  That first.  Secondly --
                       DR. POWERS:  Well, operator actions is
           very much a part of this.
                       MR. HARRISON:  Right, and the values that
           they provided of a 20 percent chance of failure the
           staff felt was a conservatively high number,
           especially given the antidotal events from the
           training simulators that they meet their criteria
           every time they have done it in the last four years.
                       DR. POWERS:  But from your own reports
           there is no correlation between scores on training
           exercises and operator errors.
                       MR. HARRISON:  Right, and we are not
           basing our answer on that.  We are just saying that is
           just information.
                       CHAIRMAN APOSTOLAKIS:  Now, it would help
           me to understand the situation here to know what is
           the error forcing context in the initiation standby
           liquid control?
                       MR. HARRISON:  I'm sorry, but I didn't
           catch the first part of your question.
                       CHAIRMAN APOSTOLAKIS:  What is the error
           forcing context?  Have you heard those words before?
                       MR. HARRISON:  I am not a human factors
           person, but there is performance shaping factors and
           on this one there is --
                       CHAIRMAN APOSTOLAKIS:  So you are using
           what, the level of stresses that are going out?
                       MR. HARRISON: This is not my analysis, and
           I would actually turn to Brad Hopkins from the
           licensee to address actually how they modeled that. 
           Again, I believe he referred to these as a group of
           different human action models to come up with their
                       CHAIRMAN APOSTOLAKIS:  But you approved
                       DR. POWERS:  Mr. Chairman, I am doing
           grievous damage to your schedule.
                       CHAIRMAN APOSTOLAKIS:  Yes, you are.
                       DR. POWERS:  And I know that your generous
           nature doesn't extend to me in that direction.  I
           think I am going to have to move this along here, and
           I will turn to the speakers and ask if you can help me
           any, because he gets violent with me.  
                       MR. CARUSO:  The next speaker is going to
           be Kamal Manoly from the civil engineering and
           mechanics section of the Division of Engineering.
                       DR. POWERS:  I am I am the one that was
           particularly interested in communicative usage
           factors, and could I say that I think that this is not
           an essential thing for the committee, and we can move
                       CHAIRMAN APOSTOLAKIS:  And that is no
           reflection of you, Mr. Manoly.
                       MR. MANOLY:  Thank you.
                       MR. LOBEL:  My name is Richard Lobel, and
           I am a reviewer in the plant systems branch in NRR. 
           And I have been asked to address the audit calculation
           we did to look at the GE calculations for the Duane
           Arnold Power Uprate.  
                       We decided to do the audit for four
           reasons.  First, there was a large increase in power,
           and we wanted to be sure that we understood the
           behavior with that increase in power.  
                       Second, there was a lack of a staff review
           on one of the codes that is used by the licensee, and
           we wanted to gain some confidence in the GE code.
                       There was also a desire to better
           understand the input assumptions that are used by the
           licensee; and finally there was the issue of the
           credit that was taken for the containment accident
           pressure, and doing MPSH calculations.
                       Four cases were considered by the
           licensee, and we audited -- that is, we did our own
           calculations for two of those cases as indicated by
           the little hand-pointers.
                       The name of the GE code I put in
           parentheses.  The peak pressure calculation is a short
           term calculation that is done with the M3CPT code, and
           the peak wet well water temperature calculation was
           done with a SHEX code.
                       And that is a long term calculation, and
           the difference between short term and long terms is in
           the type of assumptions that are used, and the way
           that the two are modeled.
                       Another calculation that is done with SHEX
           is the containment conditions for the MPSH pressure,
           the MPSH margin calculations; and finally there is a
           peak dry well temperature calculation that is done for
           EQ purposes, and that is done with SHEX and a spread
                       Okay.  The calculations were performed for
           the NRC staff by Information Systems Laboratories,
           Incorporated, ISL.  They did a very good job.  ISL
           used the NRC contained two code at our request.
                       ISL was also requested to use some
           guidance that was developed by our Office of Research
           for the use of contained 2.0 for design basis accident
                       Contained 2.0 is a best estimate code, and
           this guidance document was some work that was done for
           research at our request to ask what assumptions should
           be made to do a conservative calculation.
                       The guidance is similar to the licensee's
           assumptions in many ways.  Finally, and this is
           important, we used the licensee's mass and energy as
           an input.  Mass and energy is important, and this is
           where the effect of the uprate shows itself in the
           containment calculations.
                       But we were interested in assessing the
           containment codes, and in this case we weren't looking
           at the behavior of the reactor and the blow down of
           the reactor.
                       So we used the licensee's input for the
           mass and energy.
                       DR. WALLIS:  How many nodes are there in
           this model for the containment?
                       MR. LOBEL:  I believe -- Ben, do you want
           to answer that?
                       MR. GITNICK:  My name is Ben Gitnick, and
           I work for Information Systems Laboratories, and I was
           the engineer who performed the audit calculation for
           the plant systems branch.
                       The audit calculation model as developed
           by CND in this guidance that Rich just mentioned has
           a four-node --
                       DR. WALLIS:  Four nodes?
                       MR. GITNICK:  Four nodes, and the reactor
           program system is one node, and the dry well is one
           node, and the suppression pool is another.  In this
           case though it would not really make much difference
           because we are not looking -- and particularly in the
           long term, we are looking more at the mass and energy,
           and not so much --
                       DR. WALLIS:  So it is a very simple
           calculation, and probably a simple problem.
                       MR. GITNICK:  Well, there is some great
           complex mechanics going on in vent clearing, and I was
           going to say the fourth node is the vent, and it has
           a special model, which is sort of a response to the
           vent clearing.
                       Containment, of course, is very flexible,
           and you can set up as many nodes as you like, but we
           are not looking at issues of stratification or mixing
           as much as vent clearing and energy deposition in the
           suppression pool.
                       DR. WALLIS:  And another question is what
           is the basis for the bottom line?
                       MR. LOBEL:  I was told that you were all
           given a copy of the contractor's report, and --
                       DR. WALLIS:  You are not going to show us
           the curves?
                       MR. LOBEL:  I can show you the curves if
           you want to see the curves.
                       DR. WALLIS:  Well, they seem to know what
           the basis for a good agreement is.
                       MR. LOBEL:  This is a curve of the long
           term pressure, and I have another one of the long term
                       DR. WALLIS:  So is there some criterion
           for how close they have to be?
                       MR. LOBEL:  No, this gets back to what
           Ralph Caruso was talking about.  There is no criteria
           for how close they have to be.  Really what we were
           looking for was that the curves basically would have
           the same trend, and be fairly close int he absolute
                       DR. WALLIS:  And not step outside some
           regulatory limit?
                       MR. LOBEL:  Right.  
                       DR. WALLIS:  Well, that would be good to
           show some limit.  A limit is a criterion.  A
           regulatory limit is presumably a criterion.
                       MR. LOBEL:  Well, the limit in this case
           -- and I don't have the conversion off the top of my
           head, but it would be 281 degrees fahrenheit.
                       DR. WALLIS:  Which isn't shown here.  Are
           there some other kinds of units for temperature here?
                       MR. LOBEL:  Right.
                       DR. POWERS:  I have to say that this
           report that you provided on this was very helpful to
           understand the conclusions that you reached, and it
           was the kind of thing that we were looking for in some
           of the other areas.
                       MR. LOBEL:  Thank you.  I guess I am done. 
           I was going to say a few more things, but it isn't
           necessary.  Are there any other questions?
                       (No audible response.)
                       MS. MOZAFARI:  I would just like to have
           a few concluding remarks by John Zwolinski on behalf
           of the NRR staff.
                       MR. ZWOLINSKI:  I would like to thank the
           committee for the opportunity to present our review of
           a first of a kind extended power uprate to you.  
                       The staff has considered this a first of
           a kind application because of the magnitude of the
           uprate.  It is the first application to take a plant
           to 20 percent over its original rated thermal power.
                       I would like to again emphasize that the
           NRR staff has taken an extensive review of the Duane
           Arnold Power Uprate request.  All areas affected by
           the power uprate have been reviewed and evaluated.
                       The staff has critically examined the
           methodologies and their application for this power
           uprate request.  The staff has concluded that all
           analytical codes and methodologies used for licensing
           analysis are acceptable for this application.
                       The results of the deterministic analyses
           have demonstrated the proposed increase in power level
           at Duane Arnold is acceptable, and meet regulatory
                       Based on the review the staff has
           concluded that the proposed power uprate can be
           approved at this time, and Dr. Wallis, your comments
           are ringing in my ears, as well as the Committee's,
           and Dr. Power's.
                       I can assure the Committee that the safety
           evaluation will contain the appropriate technical
           basis to support each section and thus the approval of
           the power uprate.  And with that, this concludes our
           presentation.  I would be happy to take any additional
                       DR. POWERS:  Are there any other questions
           posed to the staff in this area?  Seeing none, I will
           thank you, Mr. Zwolinski and Ms. Mozafari, and your
                       And I will thank Mr. McGee and his team
           for their presentation to the staff, and presentation
           of materials to the Committee, and I will turn the
           session back to the Chairman.
                       CHAIRMAN APOSTOLAKIS:  Thank you very
           much, Dr. Powers.  We will recess until 10:55.
                       (Whereupon, the meeting was recessed at
           10:35 a.m., and resumed at 10:55 a.m.)
                       CHAIRMAN APOSTOLAKIS:  We are ready to go
           back into session.  The next item is the Readiness
           Assessment for Future Plant Designs and the Staff
           Proposal Regarding Exelon's Regulatory Licensing
           Approach for the Pebble Bed Modular Reactor.  And Dr.
                       DR. KRESS:  Thank you, Dr. Apostolakis. 
           I think the committee will find this session to be
           quite interesting.  We ought to view it as a sort of
           an early interaction on this issue and something more
           like a briefing more than anything else.
                       I don't think we will be charged with a
           letter, but if we have any preliminary responses to
           what we hear, then we can make some oral statements,
           or we could write a letter if the Committee thought it
           was necessary at this time.
                       But I think it is a little preliminary to
           do that.  We are going to hear two things.  From the
           staff, we are going to hear how ready they are to
           attack the licensing or certification of these events
           plans, and the plans for getting ready.
                       And from Exelon and also the staff, we are
           going to hear about how to -- well, a possible
           proposed approach for certification of the Pebble Bed
           Modular Reactor itself.
                       And since most of our regulations are
           highly biased by LWRs, the question is how do you
           wedge a pebble bed modular reactor into that
           structure.  So I think that will be a very interesting
           subject matter and very enlightening.  
                       So with that, I guess I will turn it over
           to whoever this guy is.  Who are you and why are you
                       MR. LYONS:  In case you forget, my name is
           Jim Lyons, and I would like to thank you for the
           opportunity to come talk to you this morning.
                       DR. KRESS:  Before we go any further, I
           would like to note for the committee that one item on
           our handout, Item F, is still very preliminary, and is
           for internal committee use only in our handouts.  So
           treat it in that fashion, please.
                       MR. LYONS:  I would like to talk just a
           little bit about -- and I am going to try and go
           through this quickly -- our readiness assessment that
           we have done to assess the staff's readiness to
           license and inspect the new reactor.
                       And what this paper is trying to do, and
           it is up and getting ready to go to the Commission,
           and it will probably go to the Commission next week,
           and then it will be made public in a week or two after
           that, after they have had a chance to look at it.
                       But back in -- and I will go to my next
           slide, but back in February the Commission asked us to
           assess the technical licensing and inspection
           capabilities that the staff has to perform these new
           reactor licensing.
                       And we were supposed to identify any
           enhancements for reviewing or inspecting early site
           permits, licensing applications, and the construction
           of new plants.
                       They also asked us to assess 10 CFR Part
           50 and 52, both of them, the regulatory
           infrastructure, and whether that was sufficient for us
           to move forward with these new plants.  
                       As part of that we considered the
           certified designs that are already in the rules, and
           the certified designs that may come in in the future,
           and the pebble bit modular reactor, which we are going
           to talk more abut today.  And other generation 3 plus
           and 4 light water reactors.  
                       We also were asked to provide schedules
           and resource estimates to perform these reviews.  I am
           not going to get into those too much today.  Those
           will be in the report.  
                       I guess I would like to say at this point
           that some of those estimates are pretty high.  They
           are really based on the information that we had at the
                       We are starting to get more information,
           but as we get more information, we are going to be
           updating those resource estimates and we are proposing
           to the Commission that we come back to them like on a
           6 month interval to let them know that as business
           decisions are made, and plans are firmed up, what
           really we are going to be working on, and what we are
           not going to be working on.
                       To perform these assessment, we formed an
           inner office working group with members from the NRR,
           Research, NMSS, and the Office of General Counsel, to
           look at these things.
                       And the group has had several licensing
           scenarios for future applications based on the
           information that we had gotten.  We worked to estimate
           the duration of the reviews and the resources that
           would be necessary.
                       They used the results of critical skills
           and resource survey that we presented to the staff. 
           We also had the benefit of industry plans and proposed
           schedules that we heard in presentations or they sent
           to us.
                       We looked at what it took to do previous
           licensing and pre-application reviews, and previous
           design certifications.  We tried to factor in the
           effect of complex technical issues or policy issues
           that will be coming up.
                       And we also looked at previous resource
           and schedule evaluations that had been done in the
           late '80s and early '90s when we were in the midst of
           doing the design certifications before.  We had tried
           to do some projections, and so that kind of made the
           basis for where we were.
                       One of the things that we wanted to do was
           identify the capabilities of the staff to perform
           these reviews, and we identified skill gaps, or what
           we are calling skill gaps, and what we are calling
           skill gaps are areas where individuals with the
           expertise we needed are either limited in number,
           working on some other important issue that the agency
           has in-house, or maybe not even in the office where
           the gap exists.
                       We did not do a whole lot of looking
           across offices.  We did look at these mostly within
           the offices that -- well, each office looked
                       We tried to identify people that were at
           or near retirement and that we might expect to see
           leave the agency within the next 6 to 12 months.  And
           that expertise that just doesn't exist in the staff at
                       There were still gaps that we identified,
           and kind of a big picture or manner identified on this
           next slide.  We see gaps in nearly all areas of the
           site environmental reviews, and that is something --
                       DR. KRESS:  A lot of those in the past
           have been done by subcontractors. 
                       MR. LYONS:  Right.
                       DR. KRESS:  And can you still call upon
           those people?
                       MR. LYONS:  We still can, and in fact we
           have these gaps within the offices if you would, and
           within NRR, but in the license renewal arena, we have
           been doing environment reviews.
                       We have contracts set up, and I think we
           have somewhere on the order of 140 contractors that we
           have identified that could help us in this area.  So
           we think in the short term that some of these gaps
           could be handled by contracting out to the National
           Labs or other suppliers of environmental reviewers.
                       Let me go through some of the other
           things.  Historic and archeological resources that are
           part of this site environmental review, and that is
           something that we don't have here.
                       Financial analysts, and especially in the
           anti-trust area.  We have financial analysts that are
           looking at license transfers, and we have some strong
           people there, and we are starting to look at anti-
           trust reviews, and that would be another area that
           would be hard.
                       CHAIRMAN APOSTOLAKIS:  Did the agency ever
           have experts on the historical and archeological
                       MR. LYONS:  I think they actually had
           people that did those reviews back in the '70s, and
           when we were doing that.  We had people that would go
           and look at historical records and look at
           archeological records, and we had those people in-
                       Obviously, we have not had the need for
           that, and in some of the cases -- and the reasons that
           we don't have these people available anymore is
           because there really wasn't any work for them.  So
           they left and took on other jobs, and we never
           replaced them.
                       And there are some fairly senior people
           around that have been involved in some of these areas
           that can help us, but they are not at the reviewer
           level that we are going to need to do some of these
                       And in environmental reviews, a lot of the
           environmental reviewers and sitemologists, and
           geologists, hydrologists, that were in NRR have now
           shifted over to NMSS, and are working on Yucca
           Mountain and that type of work.  So there might be
           some people to draw on.
                       DR. KRESS:  I guess the natural question
           is given that you have identified these areas where
           there are gaps in skills, you are going to make plans
           on how you are going to deal with those gaps?
                       MR. LYONS:  That is one of the things that
           we are working with the Office of Human Resources on,
           on how we are going to bring people in, and what areas
           should we be targeting to bring new people in.
                       And then again like I said, in the short
           term, we can fill some of these gaps with contractor
           resources.  Obviously, that group is mostly for the
           early site permits, which we would expect to be the
           first areas that we would see.
                       DR. ROSEN:  Jim, one of the critical areas
           on the pebble bed will be fuel performance, and I
           expected to see that as a gap here.
                       MR. LYONS:  I think that is really the
           next bullet, which is high temperature gas reactor and
           graphite technology that the fuel aspects are going to
           be very key to this.  And in fact how you spend your
           time looking at the various aspects of the plant.
                       DR. ROSEN:  But my point is that there is
           no bullet on the slide that --
                       DR. KRESS:  Fuel performance.
                       MR. LYONS:  Well, that's really what I
           meant by the high temperature gas reactor and the
           graphite technology.  We also need help in metallurgy
           and chemical engineering, and high temperature gas
           reactor accident analysis.
                       And then when you look at inspections,
           construction inspectors, and all the people that are
           doing the construction inspections have now moved on
           to doing other types of inspections.
                       We are especially light in the
           geotechnical areas, and the same with the
           environmental reviews.  Also, as part of our
           discussions with the regions, you might have some
           fairly senior people that had construction inspection
           experience, but now are in the region or somewhere
           else, and it may be a little bit difficult to get
           people to go to a site to start doing these
           construction inspections.
                       The other thing that we identified was
           that with construction that there may be large
           portions of a plant that are built away from the site.
                       So having a strong site presence, you will
           need that in some instances, but you also will need to
           be sending inspectors to the fabrication facilities to
           do some of the inspections there.
                       DR. KRESS:  That is something that you
           haven't done much of have you?
                       MR. LYONS:  Yes, which we have not done
           much of in the past, and we did have an inspection
           program that did look at that, but again that has kind
           of gone by the wayside.  So that is an area that we
           are looking at.
                       Moving on, the overall conclusions of the
           report, and I will run through those, is that first of
           all the licensing processes that are in 10 CFR Part
           52, are ready to be used.  That doesn't mean that they
           couldn't be better, but right now we can license a
           pebble bed modular reactor, and we can license any
           other combined license that comes in.
                       We can use the procedures and the
           processes that we have now, and I guess that is our
           first point that I want to make.  And with resources
           that we have got lined up, we can see that we can
           complete the current new reactor license activities,
           which include the AP1000 pre-application review, which
           I know that the Committee is seeing some work on.
                       And the PBMR pre-application review that
           we are working on, and the rule makings that were
           going on in 10 CFR Parts 51 and 52.  
                       DR. WALLIS:  You said that 10 CFR 52 is
           ready to be used.  What does that say about something
           like containment for PBMR?
                       MR. LYONS:  Well, right now there are in
           the regulations and the general design criteria, and
           they have criteria for containment.  And as part of
           this licensing approach, the discussion that we will
           have next, we will talk about how Exelon is going to
           take the group regulations that are in Part 50, and
           how they are going to identify which of those
           regulations they will meet, and which ones they will
           meet in-part, and which ones are not applicable.
                       And that's really the whole crux of the
           next presentation.  So let me defer that to that.  The
           other thing on this Part 52 rule making that we have
           ongoing right now -- in fact, we just put up on our
           website last week draft rule making language to get
           some early interaction with stakeholders.
                       We are working on preparing a proposed
           rule making by the end of March of next year, and
           those changes are really meant to address lessons
           learned if you would from the design certifications
           that we have done previously to clarify the
           regulations and to make them easier to use.
                       And we have also had some initial
           discussions with the industry on how we are going to
           implement the early site permit, and the combined
           license reviews.  
                       So they are more trying to make the rule
           a little more efficient and easier to use.  So that is
           what we are working on there.  We also identified
           research and additional infrastructure changes that
           will make the reviews for early site permits, and
           license applications, more effective and efficient,
           and to in the long run maybe reduce some unnecessary
           regulatory burden in that area.
                       For one thing, we were looking at is there
           a another way or another regulatory framework that we
           could have put in place that would be more risk
           informed, and that would be technology neutral if you
                       So those are all things that we are
           looking at in the long term to try and do.  We also
           need to reactivate our construction inspection
           program, especially the 2511, and I don't want to get
           into a bunch of numbers.
                       But the 2511 portion of the construction
           inspection program is the pre-construction
           inspections.  So those would be the ones that are
           actually applicable to an early site permit review,
           and the inspections that we would have to do there.
                       That manual chapter is no longer active
           because we weren't using it.  So we have to look at
           how we are going to do the construction inspection
           program to verify the inspections test analysis, and
           acceptance criteria, the ITAAC that are put in place
           as part of the combined license.
                       So there is a lot of work there just to
           kind of construction inspection program back up to
           use.  As you know, and as you may know, I guess, the
           House and the Senate have appropriated $10 million to
           the NRC for next year or I guess for this year.  It is
           this year now.
                       And that is to work for future licensing,
           but those bills have not gone to conference, and they
           have not come out, and so we really don't know whether
           we are going to get all $10 million of that, or we
           will get any of it, or more, or what.
                       But right now it looks like they are in
           pretty much agreement that we would get $10 million. 
           Certainly the events of September 11 may affect that.
                       So all the work that we have done on this
           readiness assessment was really pre-September 11th,
           and so we don't really -- other than to recognize that
           it may change, you know, it is really not factored
           into our readiness assessment.
                       But even if we get the full $10 million,
           there is more work identified than there would be
           resources to do.  So obviously we would have to
           prioritize what we are going to do and which
           activities need to be worked on.
                       A lot of that has to do with how the
           industry falls out in making business decisions that
           are supposed to be made in the next 3 to 6 months.  So
           we will start to see really what applications we are
           going to get, and what applications we are not.
                       So that is why we are saying that our
           priorities are still evolving, and so we have kind of
           given a first cut at this, and the report looks on a
           project basis.
                       It gives resource estimates and duration
           estimates on a project basis, and it doesn't break it
           down on a year by year basis, because again we are not
           sure exactly when a lot of these things are going to
                       DR. KRESS:  Would that $10 million,
           assuming that you get it, go mostly to acquiring new
                       MR. LYONS:  That would be another thing. 
           Some of it would be to bring in new staff, but I would
           say that it is about -- I would say about a fourth of
           that money would be bringing in new staff and about
           three-fourths would be using contractors assistance
           for the first year.
                       The budget looks as it goes out that the
           Commission is looking at more money in the out years
           and we are trying to prioritize that work, too.  Just
           to kind of give you -- this is something that is in
           the report, but to kind of wrap this thing up, is that
           future Commission correspondence, and the Commission
           papers that we are working on, we are working on two
           that are in due in November, legal and financial
           issues that are based on a series of white papers that
           Exelon has provided us.
                       We don't plan on coming to the Committee
           with that paper.  It gets into things like anti-trust
           reviews, and the number of licenses, and what should
           the annual fees be, and I don't think that you all are
           really that interested in that.
                       You might be interested in seeing the
           paper, and reading it, but I don't think we need to
           give a presentation on that.
                       DR. KRESS:  I think we would be very
           interested in the second one though.
                       MR. LYONS:  In the second one though,
           Exelon's licensing approach, which is what we are
           really talking about today, that paper will give you
           an idea of where Exelon is coming, and where we are
           coming from, for that paper.
                       DR. KRESS:  Will we have that one on our
           November agenda?
                       MR. LYONS:  I think so.  
                       MR. ZEFTAWY:  We can have it for the
           November agenda, provided that we can get it in a
           couple of weeks before the November meetings.
                       MR. LYONS:  I think we will need to work
           with you on the timing of when we will have that
                       CHAIRMAN APOSTOLAKIS:  Yes, we need it two
           weeks before the meeting.
                       MR. LYONS:  Yes, I understand that.  I
                       CHAIRMAN APOSTOLAKIS:  But now you are on
           the other side.  
                       MR. LYONS:  We will give it to you the day
           of the meeting.  No, I understand.  The other things
           that we are working on now is AP1000, Phase 2 review,
           which I think is already on the schedule.
                       And the proposed revision to Part 52 is
           now looking for late March or early April; and we have
           some work on alternative regulatory frameworks that
           NEI is talking about presenting a paper.
                       Again, resources may cause us to not get
           too far into that, and that may or may not happen in
           June.  But definitely I think the last two would be
           ones that we would definitely come to you when we
           start talking about technical issues and policy issues
           for PBMR.  
                       So we will get into things like
           containment and some of the other technical issues on
           how the fuels will be verified and fabricated, and
           that sort of thing.  
                       So those are other things that will be
           coming to you.  But that is mainly all I wanted to
           talk to you about.  I would like to turn it back over
           to Exelon.  
                       DR. ROSEN:  Not so fast.
                       MR. LYONS:  Okay.  Sure.
                       DR. ROSEN:  Could you go back to the first
           slide.  I think I have a simple slide or a simple
           answer.  What do you think the step requirements memo
           is talking about in the very last bullet on that
                       And did your remarks cover that?  Is that
           the AP1000 that you are talking about there on that
                       MR. LYONS:  To consider the certified
           designs and other generation --
                       DR. ROSEN:  The last bullet there, that
           says other generation --
                       MR. LYONS:  Yes.  
                       DR. ROSEN:  Do you see anything else
           coming down the pike in the near term other than PBMR?
                       MR. LYONS:  Yes.  We are already in
           discussions with Genotomics on the GTMHR, the gas
           turbine modular -- well, I am trying to learn these as
           they changed their name.  Actually, it is from the
           MHGTR that they had before.
                       So, the GTMHR, and they are looking at
           coming in, and also Westinghouse is looking to come in
           with the IRRAS plant.  So that might be another one,
           and there may be other vendors out there that would
           seek for us to review --
                       DR. ROSEN:  Well, do you want to
           reconsider any of your questions about capability? 
           Imagine if you got all of that.
                       MR. LYONS:  Well, that is one of the other
           messages that I am trying to get, is if industry -- if
           all the industry proposals, and plans come to
           fruition, we are going to be very tight on resources. 
                       And we are going to as an agency are going
           to have to work with industry to try and prioritize
           which reviews will go forward and which won't.  
                       And obviously the first priority would
           always go to someone who came in with a combined
           license application, because that pushes you forward
           to actually license a plant.
                       I think early site permits would also be
           high on our list to review, but that is one of the
           things that we are really looking at, is that it is
           going to be tough if everybody comes in.
                       That is one of the messages that we were
           trying to send to the Commission.  Any other
           questions?  I will turn it over to Kevin Borton and
                       MR. MUNTZ:  Good morning.  I would to
           thank the ACRS for this opportunity to discuss our
           proposed licensing approach for the PBMR in the United
           States.  I would like to introduce our team.  I am Jim
           Muntz, vice present for Exelon for PBMR North America
                       And next to me is Rod Krich, who is our
           vice president for PBMR licensing; and then Mr. Kevin
           Borton, who is our manager of licensing for PBMR.  We
           have Mr.  Greg Krueger, from Exelon, who is our PRA
                       And Mr. Fred Silady from Technology
           Insights, a consultant to Exelon.  And Mr. Steve
           Frantz, a consultant to Exelon from MLB.  At this
           point, I would like to turn it over to Kevin to start
           through the presentation.
                       MR. BORTON:  Good morning.  As Jim said,
           I am Kevin Borton, and I am the licensing manager and
           in today's presentation we would like to present to
           you the proposed methods and processes that we
           presented to the staff that we feel could use to
           assess the PBMR design in order to obtain an NRC
                       We will also demonstrate these methods
           with some examples from an earlier advanced gas
           coolant reactor.  We will describe our process which
           we will use to judge the applicability of the current
           regulations, and we will compare the approach with
           some current regulatory practices.
                       Just an outline of this morning's
           presentation.  We will give you a brief summary of our
           licensing strategy and what built up to our strategy.
                       We will go into some detail about the
           elements of our licensing approach, and we will do a
           high level summary of some NRC policies and practices
           that we would like to compare this to.
                       Also, we will talk about some outcomes or
           desires that we have for the pre-application
           activities with the NRC, and with this last bullet in
           mind, you just heard that the staff has identified
           some technical issues that they would like to resolve
           with us during pre-application space.
                       Our intention is to work with the staff
           during pre-application to bring some of these
           technical issues to resolution.  However, what we are
           presenting this morning does form the basis on which
           we could work with the staff to resolve those
           technical issues.
                       CHAIRMAN APOSTOLAKIS:  You will come back
           to the Regulatory Guide 1.174??
                       MR. BORTON:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. BORTON:  This is just the outline of
           what we have for today.  Now, briefly our strategy has
           been to work within the Part 52 process in order to
           obtain a combined license.  
                       We are building upon a design and review
           of a South African demonstration plant.  We are not
           looking or seeking for any new rule making.  We are
           going to use the existing regulations.
                       Part of our strategy was to ensure that
           there is a definable and stable licensing approach,
           and this is the basis of today's presentation.  Part
           of the strategy was to develop a licensing basis
           acceptance criteria, and will be building upon the
           MHTGR work done in the 1980s by the DOE and reviewed
           by the NRC.
                       Now, it will take a little time here, but
           this is the basis or the biggest part of our
           presentation today, is the elements of our licensing
                       The first element is the top level
           regulatory criteria, and that establishes what must be
           achieved in order to conclude that the public is
           adequately protected.
                       Equally important is the licensing basis
           event, which define the situations when the top level
           regulatory criteria must be met.  We will establish
           some design specific regulatory design criteria, and
           safety related equipment classification, which will
           establish how it will be assured that the top level
           regulatory criteria are met.
                       And then we will identify the conditions
           for and special treatment of the equipment to assure
           us how well the top level criteria are satisfied. 
           Now, if you take a look at the first four elements,
           that could define the licensing basis.
                       However, in addition to that, we are going
           to use those first four elements to determine the
           applicable regulatory requirements which will
           establish the scope of our application.
                       DR. ROSEN:  I am going to have to
           interrupt and ask a question about the fourth point. 
           When you talk about special treatment requirements and
           defining how well they need to be applied, it seems to
           me that is a little bit of a conflict with the prior
           slide, where you talked about use of current
                       Will you be seeking exemption from the
           special treatment requirements in Part 50 as part of
                       MR. BORTON:  We are going to be addressing
           the special treatment in there with our analysis and
           I think when we walk through those steps later on that
           you will see specifically how we are going to do that.
                       DR. ROSEN:  Are you going to use 50.12 to
           try to get an exemption, as has been done in light
           water reactors recently?
                       MR. KRICH:  In those cases where we need
           to get an exemption from an existing rule, yes, we
           would use 50.12.
                       DR. ROSEN:  And that's what I thought you
           could do, and I am not characterizing that is a good
           idea or a bad idea, but I am just saying that it
           doesn't seem consistent, unless you would say that
           using 50.12 is using the current regulations.
                       MR. KRICH:  Using 50.12 is using the
           current regulation.
                       DR. ROSEN:  Fine.
                       CHAIRMAN APOSTOLAKIS:  On Item 2, I don't
           understand the word when; define when the TLRC must be
           met.  Are there other situations when they are not
           met?  The word when throws me off.
                       MR. BORTON:  We are going to be looking at
           different frequency of events and categorizing those
           frequencies, and then how we compare those different
           regions against the top level regulatory criteria.  So
           we are looking at a number of criterion.
                       MR. KRICH:  I think as we go through it we
                       CHAIRMAN APOSTOLAKIS:  Will it be
           replacing the current design basis events?
                       MR. KRICH:  The licensing basis events
           incorporates all the events that covers the
           anticipated operational occurrences.
                       CHAIRMAN APOSTOLAKIS:  I guess the word
           when is not clear to me.
                       MR. BORTON:  This next slide depicts the
           overall approach in a model.  As you can see on the
           right side, there is a green area, and that is our
           elements 2 through 4, our top level regulatory
           criteria, aligned with the NRC mission and safety
                       Again, those elements were the licensing
           basis events, and development of regulatory design
           criteria, safety related equipment selection, and
           special treatment.
                       As you can see the block towards the
           center in the compare, we break these down into a
           functional level, and the resulting criteria then
           could be used to compare it against the current
           regulations on the blue side there, also at their
           functional level or underlying purpose, which goes
           back to the question of 50.12.
                       DR. KRESS:  This approach, which I would
           call a risk informed approach, is going to rely
           heavily on having a good PRA.
                       MR. BORTON:  That's correct.  And we are
           going to talk about some of the attributes of the PRA.
                       DR. KRESS:  Talk about the attributes of
           that, and then how it is going to be reviewed and
           qualified as a good PRA.
                       MR. BORTON:  We will get through the steps
           on those.
                       DR. ROSEN:  Well, it will be more than
           just the PRA, because this is a risk informed approach
           and not a risk basis approach.
                       MR. BORTON:  It's both.
                       DR. ROSEN:  So it is going to require the
           same kind of expert panel structure and protocols that
           have been developed to make applications work on the
           light water side as well, I think.  Is that your view
           of it, Greg?
                       MR. KRUEGER:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Another thing.  It
           says licensing approach, NRC mission and safety goals. 
           As far as I know the safety goals are not the
           regulation --
                       DR. KRESS:  They kind of show up in
           regulations here and there, and like the regulatory
           analysis.  They show up in 1.174.
                       CHAIRMAN APOSTOLAKIS:  But the Commission
           never said that if you meet the goals that you are
                       DR. KRESS:  No, but this is a different
           date and time, and a different reactor, and you have
           to start somewhere.
                       CHAIRMAN APOSTOLAKIS:  So it is the blue
           boxes then --
                       DR. KRESS:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And right now that
           is what it is, right?
                       MR. BORTON:  That's correct.  Just the
           lower part of that model shows that we will be going
           through and looking for the regulations that are
           applicable, and partially applicable, and not
           applicable, or identify areas where this design
           requires attention to that.
                       We will also be in a better position to
           address any policy issues, and being armed with this
           information, and being able to put together the scope
           of our application.
                       DR. ROSEN:  Does the PBMR specific block
           imply that there may be some new requirements that are
           not in Part 50 now?
                       MR. BORTON:  Yes, that's correct, design
                       DR. KRESS:  Does this have to do with the
           graphite, for example?
                       MR. BORTON:  Yes.  The first element is
           the top level regulatory criterion, and this fits into
           the establishment of a reference value to make sure
           that there is adequate protection afforded by the
                       We will look at the criteria coming from
           the current regulations and guidance based on these
           specific principles.  We want to ensure that there are
           direct statements of acceptable health.  
                       In other words, ensure that the criteria
           is fundamental to protection.  We will look at it and
           make sure that it is quantifiable, and measured or
           calculated, and ensure that we can make an
           indisputable conclusion or come up with unambiguous
                       And finally that it is an independent
           reactor type site, and generic in terms, and to ensure
           that is purely top level.  
                       DR. KRESS:  In terms of this independent
           site, it sounds like a touch assignment to me.  That
           means that you are going to have to bound any
           potential sites that you have because these
           attributes, these top level criteria, are dependent on
           population, and meteorology, and that sort of thing.
                       So in order to make them what you have to
           meet in, say, certification, and site independent, you
           will have to have sort of a bounding site or a
           bounding meteorology, or something of that nature?
                       MR. SILADY:  My name is Fred Silady.  We
           are looking at their current regulations and screening
           them on these three criteria.  When it comes to the
           assessment, yes, at a particular site, and then there
           are various approaches on whether to do it
           individually or bound.
                       DR. KRESS:  I see.
                       DR. BONACA:  If you are working at
           developing these criteria that you would propose to
           the NRC, I guess since it is going to be an
           independent reactor type, are you working with other
           designers?  Are there some industry standard
           committees being formed to look at those issues?
                       MR. BORTON:  No, what we are doing is we
           are trying to look at establishing those top level
           criteria, and I think the next slide gets a little bit
           more into details of why we selected what we selected.
                       And again it is used as a reference value
           to judge -- not to measure, but to judge the
                       CHAIRMAN APOSTOLAKIS:  I see.  All right.
                       MR. BORTON:  So looking at those
           principles, we did select these limiting top level
           regulatory criteria for the PBMR.  The first is 10 CFR
           50, Appendix I, which is the annualized off-site dose
                       And 10 CFR 50.34, which are the design
           basis accident off-site doses; EPA-400, which are the
           protective action guideline doses; and the NRC safety
           goal for individual prompt fatality risk.
                       So again these are the direct measures,
           quantitative, independent limiting criteria used to
           assess the design against.  The second element is to
           define what are the licensing basis events.  So it is
           when these top level criteria must be met.
                       So we will look at off-normal and accident
           events for the PBMR, and Exelon will develop the
           licensing basis events through our PRA, in which they
           are collectively analyzed for demonstrating
           conformance with the safety goals.
                       Now, thinking back, we have a top level
           regulatory criterion, and in order to assess these
           events in relation to those criteria, frequency
           regions are necessary to frame the criteria in the
           context of risk, and this is the three regions that we
           alluded to before which have been identified.
                       The first region is the anticipated
           operational occurrences region.  This is where events
           are expected once or more in a lifetime of the plant.
                       A plant is defined as having up to 10
           reactors.  The plant lifetime is assumed to be 40
           years, and therefore a lower frequency of 0.025 times
           10 to the minus 2 was selected.
                       Again, Appendix I was selected as the
           criteria for this region, and it will be -- the
           frequency of events, and the events will be identified
           as families of events.  They could exceed the Appendix
           I criteria if certain equipment or design features had
           not been put into the plant.
                       The consequences will be realistically
           analyzed for compliance with Appendix I.  The second
           region is the design basis event region.  These are
           events of lower frequency not expected to occur in the
           lifetime of a plant.
                       DR. POWERS:  Excuse me, but I am not sure
           how you do the frequency analysis, and maybe you can
           help me a little bit.  You quote .025 per plant, and
           that can have 10 reactors at that plant, or is it .025
           per reactor? 
                       MR. SILADY:  The .025 is per plant year,
           and we are just making the point that for the PBMR
           that a plant could have up to 10 reactors, but all the
           assessments will be done on a per plant year basis.
                       DR. POWERS:  Okay.  So that each reactor
           would have a frequency of .0025?
                       MR. SILADY:  For independent events.
                       DR. POWERS:  And are all of the events
                       MR. SILADY:  Not necessarily in a PRA. 
                       DR. POWERS:  So do you calculate the
           common mode --
                       MR. SILADY:  Yes.
                       DR. POWERS:  -- explicitly, or do you use
           some sort of a beta factor or something like that?
                       MR. SILADY:  The PRA is being done now,
           and I think that they will use the best methods
           available, which generally are the beta factor
                       DR. POWERS:  What do you choose as the
           beta factor for a common mode between two individual
                       MR. SILADY:  We will probably have more
           interactions on how we do the PRA and so on.  At this
           point, we want to define the criteria, and we know
           that we have to do it per plant year, because it is
           kind of unique with 10 reactors.
                       DR. ROSEN:  When you chose an example, you
           chose seismic as affecting more than one unit at a
           site, and that I think is fairly obvious to us.  But
           are there internal events at a plant with up to 10
           reactors that could affect more than one reactor?
                       And that comes to the question of how much
           isolation, how independent the individual units are
           intended to be, and maybe that is a design detail and
           I am way ahead of where you are.
                       MR. SILADY:  Well, we would want to
           consider it, and we are setting it up where we can by
           making it per plant year.
                       DR. ROSEN:  I am not sure you answered my
           question exactly.
                       MR. SILADY:  The answer is that there are
           internal events.  Let's say a common mode on a control
           room or whatever, you can think of things, and the PRA
           needs to do that.
                       DR. ROSEN:  And you want a control room
           for all these plants as I understand in your proposed
                       MR. SILADY:  Without getting into the
           details of the design and going into that review, the
           answer is yes.
                       DR. ROSEN:  Clearly if you have one
           control room for 10 units, you have chances of having
                       DR. BONACA:  I'm sorry, but I had a
           question on the previous page.  On page 8, this is a
           category for anticipated operational occurrences, and
           then the next one you are moving to design basis.  Are
           you planning to divide this operation on occurrences
           also in families of groups?
                       MR. BORTON:  That's correct.
                       DR. BONACA:  So you will have additional
           divisions inside?
                       MR. BORTON:  That's correct, and we will
           plot that for you in other slides.
                       DR. BONACA:  So it will be equivalent to
           the old ANSI standards with the help of a PRA?
                       MR. BORTON:  Yes.  
                       CHAIRMAN APOSTOLAKIS:  When you say vents,
           you mean initiate a new vent or the whole sequence?
                       MR. SILADY:  It is a full sequence of
                       CHAIRMAN APOSTOLAKIS:  A whole sequence of
                       MR. BORTON:  Yes.  So for the DBE, the
           slide that is up there now, we looked at a lower bound
           frequency of 10 to the minus 4 per plant year.  With
           events at 10 to the minus 4, you have a less than one
           percent chance of it occurring over the lifetime of
           the plant.
                       CHAIRMAN APOSTOLAKIS:  So 10 to the minus
           4 and the lifetime is 40 years?
                       MR. BORTON:  Yes, 40 years.  The criteria
           was 5034 and was selected as the top level regulatory
           criteria for this region, and it is the family of
           events that could exceed that criteria if certain
           equipment was not afforded by the design.
                       There will be mean values and uncertainty
           ranges of consequences and are both evaluated to
           provide high confidence compliance with this region.
                       DR. ROSEN:  Why do you pick 40 years? 
           Forty years was an anachronism.  Why not 12?  Why not
                       CHAIRMAN APOSTOLAKIS:  Why not 60?
                       DR. ROSEN:  Yes, why not 60?
                       DR. ROSEN:  What is this magic 40?
                       CHAIRMAN APOSTOLAKIS:  Sixty is good.
                       MR. KRICH:  We agree that 60 is good, but
           right now the way the rules are written and the
           requirements of the law are, 40 years is what a
           license can be given for.
                       CHAIRMAN APOSTOLAKIS:  I see.  Okay.
                       MR. KRICH:  So that was the basis for
           selecting 40.
                       DR. ROSEN:  But you are going to use
                       CHAIRMAN APOSTOLAKIS:  They are changing
           so many things.
                       MR. KRICH:  We weren't anticipating
           looking at that and extending the 40 years at this
           point in time.  We were just looking at the 40 years
           at this point in time.  But certainly if the NRC is
           amenable to asking for a 60 year license, then that is
           something that we should look at.
                       DR. ROSEN:  I am not the NRC.  I am just
           one member of ACRS and I don't know what 40 means.  I
           never did.
                       MR. FRANTZ:  This is Steve Frantz.  The
           Atomic Energy Act also specifies a 40 year period, and
           that is set by law.
                       MR. MUNTZ:  I think we are just looking to
           what we have been working with, and we didn't go much
           further than that.
                       DR. KRESS:  You have to change so many
           things that you might as well not fight every fight
           right now.  You can wait 40 years and fight that.
                       MR. BORTON:  The last region here is the
           emergency planning basis event region, and these are
           events that are not expected to occur in the lifetime
           of a fleet of plants.  A lower frequency was selected
           as 5 times 10 to the minus 7 per plant year.
                       That is consistent with meeting the prompt
           fatality safety goal, and here consequences will be
           realistically evaluated against the other criteria,
           which is protective action guides and their dose
                       Having selected a top level regulatory
           criterion and defining the LBE regions, and now we
           could plot them, and the first thing you note about
           this plot is the Y access is the frequency.  The event
           sequence mean frequency for a plant year.  
                       The X axis is the consequences, and the
           solid line going through the center there, the blue,
           is the top level regular criteria.  And below and to
           the left, which is the acceptable region, and above
           and to the right which is unacceptable --
                       DR. KRESS:  I would like to note as an
           aside to the Committee that frequently stated comment
           that frequency consequences occurs could incorporate
           the whole range of regulatory requirements is now
           given -- this is a demonstration of that comment that
           I have made several times.  I just wanted the
           committee to be aware of that.
                       CHAIRMAN APOSTOLAKIS:  When you say on the
           left event sequence mean frequency, what do you mean?
                       MR. SILADY:  It is the initiating event
           and any subsequent failures.  It is the entire
           initiating event frequency and all the probabilities,
           the entire frequency of the end-state expressed on a
           mean basis.
                       CHAIRMAN APOSTOLAKIS:  But this curve is
           supposed to be a complimentary cumulative curve.  In
           other words, you shouldn't go with individual
           sequences here.  You should go with a sum.
                       In other words, if I look at the curve, at
           the dose, and I pick 10 to the minus 1, and I go up,
           then all the contributions of 10 to the minus 1 or
           less REM should have frequencies smaller than whatever
           the number, 2.5 down to the minus 2.
                       This is an old interpretation of the
           Farmer curve.  It was misinterpreted at the beginning
           that it applied to individual sequences.  Now it
           applies to the cumulative.  Otherwise -- you know the
           old trick.  You can -- what is a sequence is not well
                       MR. SILADY:  I agree with you with regards
           to the comments on Farmers curve and so on, but what
           we were trying to do here was look at each of the top
           of the regulatory criteria.  
                       Some of those are expressed in terms of an
           individual event, and some of them -- like the safety
           goal -- are cued -- and we trying to put everything on
           one plot very simply here, and we have had some
           difficulties as you can see by the footnotes as to
           whether it is at the EAB or EPZ, or LPZ.
                       And some of these are expressed in whole
           body, and some of them are expressed in total
           effective dose equivalent.  We understand that when
           you get down close to the third region there that they
           have to be cued for the safety goal.
                       CHAIRMAN APOSTOLAKIS:  The third region?
                       MR. SILADY:  The emergency planning, and
           I agree with you and we will cum those.  But with
           regards to the design basis events, the derivation of
           what the design basis events should be, and with
           regards to the derivation of what the AOO should be,
           we want to just look at it on a per accident family
                       CHAIRMAN APOSTOLAKIS:  You can do that
           separately, but this curve cannot be applied to
           individual sequences simply because what is a sequence
           is an ill-defined concept.
                       You can give me a sequence as you know
           very well, or I can give you one and you can break it
           up into 20 sequences, each one with 1/20th of the
           original frequency.  Now, the staff will never accept
           something like that.
                       MR. SILADY:  Right, and neither would our
           peer review.
                       CHAIRMAN APOSTOLAKIS:  And I appreciate
           the difficulty you have, but it seems to me that this
           frequency -- I mean, whatever else you have to do,
           this curve has to be interpreted in a cumulative way.
                       MR. SILADY:  It is cumulative for the same
           consequence.  It is an accident family.  They have to
           be summed for accidents, and I agree with that fully.
                       CHAIRMAN APOSTOLAKIS:  Yes, that's what I
           am saying.  Now, Farmer himself, when he did this in
           1967, was not clear.  But his argument later was that,
           look, whether you sum or not doesn't matter.  There
           will be 2 or 3 of those that really dominate.  And I
           think from that point of view that he was right.
                       But I think since we are starting here
           fresh and anew, it seems to me that it would be wise
           to do it correctly, and I appreciate the difficulties
           that you will have with other sites, but this
           particular curve -- and on another point, since again
           we are starting fresh.
                       There have been variations of this that
           some people have found convenient, and some people
           have not.  The variation is in -- I mean, the way that
           you have it now, the original curve, you have an
           unacceptable region and an acceptable region.
                       One could imagine that you have a light
           blue curve that is below this one, and then you have
           three regions; the unacceptable, the acceptable, and
           the let's talk about it.
                       That gives you much more flexibility in my
           view when you negotiate with a regulator.  And that
           curve I don't think you can have from the current
           regulations, unless you can look very carefully.
                       But that probably will help you.  Now, on
           the other hand, you may not want to introduce too many
           new things, but that is just an idea.  Now, in
           fairness, the Dutch did this for all their hazardous
           facilities, and I understand that they are not doing
           it anymore.  So there must be a reason for that.
                       So I am giving you both sides of the coin,
           but --
                       MR. SILADY:  It is a good suggestion, and
           I note that in the U.K. safety assessment that they
           have that.
                       DR. KRESS:  And the Swiss have a curve
           similar to this which is the cumulative SC curve for
           the --
                       CHAIRMAN APOSTOLAKIS:  And they agreed to
           that and so it has to be.  This is a very good step
           forward.  I really like this.
                       DR. WALLIS:  I have a comment on this
           curve.  If this were sort of risk mutual, you might
           like it if it was proportionally 1 over X.  I mean, if
           we have this risk adverse approach, then the curve
           would dip down faster on the right-hand side.
                       This is actually the opposite of risk-
           adverse.  You are allowing more, a very large risk,
           and the very large events.  You are high.  So it is
           not risk-adverse.  It is quite the opposite.  One
           would expect it to be more risk adverse.
                       MR. SILADY:  Can I make a comment on this? 
           That is a good observation, and one that we have
           noticed as well.  But all we are doing is taking the
           regulations as we found them and plotting them.
                       CHAIRMAN APOSTOLAKIS:  One other point
           that will come up in the future I'm sure, is that as
           you move to the right, the uncertainties in those
           frequencies of course will increase as you are very
           well aware.
                       And I wonder whether we need some guidance
           as to how much of that distribution, the vertical
           distribution and frequency, can be allowed to be above
           the blue curve.
                       And it seems to me -- well, I don't expect
           an answer today, but it seems to me -- unless you have
           it.  You do have an answer?
                       MR. BORTON:  We are going to walk through
           those and show some examples here.
                       MR. KRICH:  We have established examples
           for ourselves that we will discuss.
                       CHAIRMAN APOSTOLAKIS:  That's good.
                       MR. BORTON:  I think we covered everything
           that was on this curve.  The only thing again is that
           LPZ and EPZ are assumed to be at the exclusionary
           boundary, which gives us a little bit higher degree of
           margin with the top level regulatory criteria.  
                       So once we have this, we could plot or
           populate the events derived from the PBMR PRA, or test
           some deterministically generated events against this
           type of plot.
                       CHAIRMAN APOSTOLAKIS:  Now, let me
           understand something else and maybe that is a question
           for the staff.  Are all the regulations embedded in
           this?  In other words, if I do this, and I show all my
           sequences cumulative and so on are below the blue
           line, are there any other regulations that I have to
                       MR. KING:  This is Tom King from the
           staff.  Yes, the GDCs are not embedded in this.  This
           is a good approach to lay out the regulations that
           have quantitative dose criterion.
                       But there is a whole other set of
           regulations that are basically embedded in the general
           design criteria that have to be dealt with as part of
           this licensing approach.  They will talk about it and
           we will talk about it.
                       MR. KRICH:  10 CFR 20 and all the other
           regulations, and we will talk about that later, but
           this is really just looking at the off-site dose
                       MR. BORTON:  But our overall approach does
           have to look at the whole Part 50 regulations.  So as
           you see the fifth element and that we will go to later
           on, using these as a top level regulatory criteria. 
           However, we will still have to go through each one of
           the regulations and address each one of them since we
           are not asking for --
                       CHAIRMAN APOSTOLAKIS:  But you will
           declare some of them as inapplicable?
                       MR. BORTON:  That's correct.
                       MR. SILADY:  That's correct.
                       MR. BORTON:  And we will tell you some of
           the criteria for that.
                       CHAIRMAN APOSTOLAKIS:  Okay.  
                       MR. BORTON:  This was the PRA that we
           talked about and the scoping requirements.  There
           needs to be a comprehensive treatment of initiating
           events, sequences, and end states.
                       The PRA will include operational
           experience from both light water and gas reactors from
           here and overseas.  We will address all modes of
           operation, including shutdown in internal and external
                       And the design characteristics that
           support the use of an integrated event tree structure
           from initiating events to end states for accident
           family consequences and frequencies, including their
                       CHAIRMAN APOSTOLAKIS:  I don't understand
           this last bullet.  What do you mean by support?
                       MR. SILADY:  Well, the integrated event
           tree that will be developed will be like a level 1, 2,
           and 3 PRA integrated together.  It won't be separated
           or split due to core damage --
                       CHAIRMAN APOSTOLAKIS:  And this is similar
           to what Sandia did in 1150.
                       MR. SILADY:  Which is classes.
                       DR. ROSEN:  And to take advantage of the
           inherent features of the PBMR, I looked at some of
           your documentation, and you talk about doing a level
           three PRA and taking it all the way out.
                       And that raises the question of needing to
           have a specific site or some sort of -- or not having
           a site and identifying a specific site, and doing a
           very bounding -- or taking a very bounding approach
           which might penalize the design for most real sites.
                       MR. BORTON:  That's correct.  For the top
           level criteria that we are using here today to assess
           the design not against a site, but just looking at the
           design, we will stop at the level two PRA, and that
           will be the criteria which we use to assess against
           the top level regulatory criteria.
                       And the MHTGR, the 1980s and '90s afforded
           us some examples now to plot against this curve.  As
           you can see there the LBEs do populate all three
           regions defining the events for those regions.  
                       There are some events that do not result
           in off-site releases.  They are on the far left. 
           However, we can eliminate those since they are
           corresponding functions of the plant that prevent them
           from migrating or exceeding the Appendix I or 10 CFR
           50.34 limits.
                       Again, you can see the uncertainty bands
           here and they plan role in the classification of the
           vents.  DBE-6, the top arrow, and DBE-7, the mean,
           fall outside the DBE range.  However, their
           uncertainty bands either fall in or are in close
           proximity to the DBE, and that's why they were
           described or classified as DBE events.
                       CHAIRMAN APOSTOLAKIS:  Now, that is
           something that bothers me.  Pick any one of those --
           DBE 11 or somewhere in there -- so that we can all see
           it.  The way it is presented is contrary or in
           conflict with the intent of the criteria, because what
           they are doing is they are keeping the sequence fixed,
           and then they are saying given these sequence of
           events, I am uncertain about their frequency, and I am
           uncertain about the consequences resulting.
                       The intent of the curve though, the blue
           curve you showed earlier, is not that.  The intent is
           that those are independent barriers, from the end of
           the figure from the dose, and I go up, and all my
           uncertainties are on the frequency.
                       So you have to take this and this, and
           when you sum them up, then you have to do that, which
           is done routinely in 113 PRAs by the way, with the
           various contributors.  Ultimately, your independent
           variable is the dose.
                       MR. SILADY:  I can see that there is still
           a little bit of communication -- that I didn't
           communicate properly.  I thought we had it resolved,
           but there is another aspect to it here.  
                       The dose here in the DBE region, for
           instance, the one by DBE 11, back in the MHTGR days it
           was called 10 CFR 100 and now it is 10 CFR 50.34.  It
           is 25 REM whole body it used to be, and now it is a
           total effective dose equivalent.  It is for an event,
           and it is not a cum for all your design basis.
                       CHAIRMAN APOSTOLAKIS:  The sequence is
           constant and then you have uncertainty regarding its
           frequency and its consequences.  So the blue curve is
                       MR. SILADY:  No, this is the blue curve. 
           It is just the blue curve from the '80s.
                       DR. WALLIS:  It is the same, except -- 
                       CHAIRMAN APOSTOLAKIS:  You see, in the
           blue code, and we will go back.  The way that I would
           read this is that I will ask myself on the horizontal
           access, what is the frequency of exceeding this number
           of RADs, right?
                       MR. SILADY:  We are not using this as a
           complimentary cumulative distribution function,
           because 10 CFR 100, and then 50.34 weren't set up that
           way.  It was before PRA.  
                       So for the design basis accidents, the
           traditional practice is that you take whatever the DBE
           is and you compare it, and you come out with hopefully
           a small fraction, different fractions at the
           construction permits stage, and then as built, of that
                       And then you go to a different accident,
           another DBE, and you compare it.
                       CHAIRMAN APOSTOLAKIS:  So what is the
           purpose of this curve then?
                       MR. SILADY:  The purpose of the curve is
           to help us figure out with PRA insights what the
           corresponding DBE should be for this new kind of
           reactor.  It is not a complimentary cumulative
           distribution function up there.
                       CHAIRMAN APOSTOLAKIS:  The concept is that
           if you choose those correctly, and decide to withstand
           them for the things, and then if you did go into the
           cumulative complimentary distribution function, the
           anticipation is that you would meet that, and in my
           mind that proposition has never been proved.
                       MR. SILADY:  Well, we could plot the acute
           and latent fatality safety goals throughout the entire
           region, but they aren't nearly as limiting as 10 CDR
           50.35 and Appendix I are.  
                       The point being made over here is that
           because of the regulations, and not a one over X
           situation, or having any risk aversion in it.  We are
           taking what the current regulations and traditional
           practices have been, and trying to find out if we use
           our PRA insights what the right DBE should be, because
           we have an opportunity here to set them correctly.
                       DR. KRESS:  Essentially, this is a more
           definitive way to establish DBEs.  I think they used
           judgement back in the early days to come up with the
           DBEs with this thinking in mind, and without ever
           really having to quantify.
                       MR. SILADY:  And that's why we use that
           selection criteria for making it quantifiable and
           using the PRA quantifiable techniques, we will know.
                       DR. KRESS:  And they may have missed some
           of them back then.  They may have had some that were
           way out of bounds in terms of frequency and some of
           them probably should not have even been considered. 
           But this to me is a more reasonable way of getting
           them on the page.
                       DR. KRESS:  If you are going to conform to
           the design basis accident or concept, this is a
           reasonable way in my mind to choose those things, and
           hopefully if you choose them correctly, then you will
           come up with meeting this cumulative distribution
                       CHAIRMAN APOSTOLAKIS:  When you say -- and
           let's take an example from a light water reactor. 
           That would be a small LOCA would it not?
                       MR. SILADY:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And it would go to
           the vent for a small LOCA and through all these
           sequences, and add them up, right?  And what I am
           saying is why don't you add them up also across
           initiating events and do it right?
                       MR. SILADY:  Now, that is the part that I
           agree with you that we are going to do.  Let's take a
           small example, like a PBMR, or a small primary coolant
           leak, where you have forced cooling, and you release
           circulating activity.  You have to sum up all the ways
           that you can get to that consequence phenomena.
                       CHAIRMAN APOSTOLAKIS:  Right.
                       MR. SILADY:  And another one where you
           have a larger leak, and let's say a little more, plate
           lifted off, and then you don't have forced cooling and
           you have release from the core because the fuel is not
           perfect, and initially particles are released, and it
           comes out over 50 hours instead of immediately.
                       That is a different kind of phenomena
           consequence sequent.  You have to sum up all the
           initiators for it, and it will have a different DBE
           number.  That is what is being done here.
                       DR. KRESS:  I think what the problem is
           that is having labeled those areas acceptable and
           unacceptable.  I don't think that is the right
           designation for those.  Those should be labeled
           something else.  
                       CHAIRMAN APOSTOLAKIS:  We are talking
           about two different curves now.  I am confused on how
           this one will lead to the other one, because unless
           you do it cumulatively --
                       DR. KRESS:  It is cumulative when you
           determine the overall risk status.
                       CHAIRMAN APOSTOLAKIS:  And the
           acceptability is cumulative.
                       DR. KRESS:  And that's why I say those are
           probably misnomers, that unacceptable and acceptable.
                       MR. SILADY:  There are two curves, and
           there are acceptable and unacceptable on each curve. 
           The first curve that we are presenting here are the
           regulations that are in the law, written in the law. 
                       So, 10 CFR 50.34, we have got to meet it
           on a per accident basis, and later there is another
           acceptable and unacceptable, which is your safety
           goal, and you cum them with complimentary cumulative
           distribution function and assure that you meet that,
           too, in all regions.
                       CHAIRMAN APOSTOLAKIS:  And you are not
           showing that today?
                       MR. SILADY:  No, we are not showing that
           today.  This one is to derive the licensing basis.
                       DR. ROSEN:  Let me check my understanding
           here.  In past licensing activities much of the
           discussion revolved around such topics as let me
           identify for you a very low probability event, and
           having done that the argument becomes, well, that is
           beyond a design basis.
                       To me what you have proposed here will
           completely finesse that discussion.
                       DR. KRESS:  That's exactly right.
                       DR. ROSEN:  Because no matter what a
           person puts on the table that is a design basis event. 
           But it may be that your 10 to the minus 8 or 9, or 10,
           or 11 is below the X axis.
                       So you can tolerate any postulation in
           terms of something happening within this framework. 
           It just ends up being of such a low probability that
           it doesn't have any impact on the design.
                       MR. SILADY:  I agree, but I just want to
           clarify that he design basis region, what you design
           for, is in the middle.  And that leads to these other
           elements that Kevin is going to get into, in terms of
           what is safety related, and show that only with the
           safety related equipment and so on.
                       And given that you design for that region,
           the design has to be able to meet the safety goals and
           the protective action guidelines at some distance in
           the region below that.
                       And even beyond that, ACRS or the staff
           may suggest other events that we both can mutually
           agree are below even that, and we will have to look at
           those, and our best estimate basis shows that the
           residual risk is low.  So there is some finesse here,
           but we are still going to have a design basis region.
                       DR. ROSEN:  Well, clearly, but my point
           was that for things below the 10 to the minus 4, we
           still have framework for discussion of them. 
                       MR. SILADY:  Exactly.
                       DR. ROSEN:  And to come to a scrutable
           decision that is joint between the applicant and the
           staff, and the ACRS, that we have identified a
           sequence that is plausible, albeit very low frequency
           or low probability, which we know where to put on this
           chart.  And we know how to deal with it in the
           regulatory aspect. 
                       DR. BONACA:  But I wanted to say that
           except for the user PRA, you are refining with PRA
           what has been done and designed in the past. 
                       MR. SILADY:  It is a hybrid, and it is
           using the best tools that we have and that we know
           today.  And there are going to be uncertainties on
           them.  This is a new reactor, but the uncertainties
           have to be treated as discussed.
                       DR. BONACA:  I understand and you have a
           much better way to go about identifying those designs,
           those sequences, and having a basis for saying this
           should be in it and this should not be in it, and
           therefore defining what equipment is not going to be
           qualified to meet those criteria, and so on and so
           forth.  So you have a structured approach with the
           benefit of a sound PRA.
                       MR. KRICH:  Exactly.  Let me stop the
           presentation now.  
                       DR. BONACA:  We will see, however, how
           later on --
                       DR. KRESS:  But the only part is the
           regulations only deal with the very right-hand side of
           that, in terms of frequency concepts; and the other
           part of the blue curve as it has been defined, and I
           think it needs defining as part of this exercise.
                       CHAIRMAN APOSTOLAKIS:  Is there a document
           that you can give us, or something that is detailed?
                       MR. BORTON:  Details of what this approach
                       CHAIRMAN APOSTOLAKIS:  Yes.  Do we have
                       MR. BORTON:  I have a letter that we sent
           to the staff on August 31st.
                       MR. ZEFTAWY:  I have the licensing
           approach from Exelon, which is in the book, but it
           does not describe the details of the special design
           basis number 11, and how did he arrive at it. 
                       MR. SILADY:  You are correct that it
           doesn't go into this example that is shown on this
           chart, but it has references back to the publicly
           available pre-application submittals, the MHTGR PSID,
           that tell you what the events are and how they were
           assessed, and it includes the PRA.  But this is just
           an example so that we could talk about what we intend
           to do.
                       MR. BORTON:  Again, the red arrows here
           depict that there are required safety functions that
           are necessary to keep the events in the acceptable
           region to the right here.
                       And that is due to the design of the
           plant.  The MHTGR gives us another example here and we
           expect the results to be similar to those for the
                       Down at the bottom here, the function of
           the MHTGR that are required to meet the DBE limits. 
           So again there is radionuclide retention, control heat
           generation, control of heat removal, and control of
           chemical attack.  
                       It is understanding these functions that
           become the first step in determining the third element
           of our approach, which is design criteria and
           equipment classification.
                       DR. WALLIS:  And chemical attack includes
           air and water?
                       MR. BORTON:  Yes, air and water.  The
           third element is really in two parts here.  We talk
           about something called regulatory design criteria, and
           then we are going to talk about safety classification
           of equipment.
                       And again this is how the top level
           regulatory criteria are met.  The first part of
           element three is the regulatory design criteria.  They
           are qualitative function statements, developed with
           risk insights, of course, because of the events which
           were PRA driven for each required safety function. 
           And now these will supplement the current light water
           reactor general design criteria.  
                       DR. ROSEN:  And again just to emphasize
           that, that is PRA supported, but expert opinion, and
           expert panel structured development.  It is not just
           the PRAs.
                       MR. BORTON:  That's correct.
                       DR. ROSEN:  Because you don't model
                       MR. BORTON:  The PRA becomes an important
           step as I get into looking at the regulations for
           their applicability, and how they apply to the design.
                       And also bringing out -- this RDC though
           are really intended to look at things that are not
           currently in the regulations that are necessary, as
           far as design criteria.
                       DR. KRESS:  If you intend to use
           importance measures for this determination of SSCs,
           like it has been done in some of the risk-informed
           applications, you will have to redefine those in terms
           of does or fission product releases or something?
                       MR. BORTON:  Yes.  The second part of the
           third element is the selection of the safety related
           SSCs.  These are the equipment relied on to perform
           the required safety functions to mitigate or prevent
           the DBEs, design basis events.
                       There is two steps in this selection
           process, and one is real obvious, the consequence
           mitigation.  That assures that the dose criteria are
                       The other one is for high consequence
           preventions, which may or may not apply with doses
           greater than the DBE criteria, and where we worry
           about the frequency of the event migrating out of the
           EP region into the design basis event region.
                       An example of how the MHTGR selected their
           safety related equipment, as you can see here, this is
           the function to remove core heat.  They looked at four
           systems available to remove the core heat.
                       Some of the systems were available and
           some were not.  However, the last two, the reactor
           cavity cooling system, and the reactor cavity in the
           surroundings -- the earth, the building -- were
           capable of renewing the core heat.
                       The RCCS, however, was selected as safety
           related based on the licensee's ability to demonstrate
           its function over the lifetime of the plant.
                       Now, this process was performed for all
           the required safety functions to mitigate design basis
           events, and the results are shown on the next table. 
           Again, this is the MHTGR example.
                       And this shows the relationship of the
           safety function with the safety related equipment.  
                       DR. WALLIS:  I'm surprised that it says
           radiate heat from vessel.  I would think that
           compaction is such a big number and such a small or
           low temperature on this thing isn't glowing red, that
           radiation would be a small contribution to the heat
                       MR. SILADY:  It is primarily radiation,
           because the core heats up in the middle, and conducts
           out to the side wall.
                       DR. WALLIS:  This is called the vessel to
           the outside world?
                       MR. SILADY:  Yes.
                       DR. KRESS:  As best as I recall, they 
           coated the outside of the vessel with --
                       MR. SILADY:  There were discussions on the
           MSTGR of increasing the humidicivity, but no decision
           -- and it is not likely that that will be needed for
           the PBMR for smaller power and power density.
                       DR. WALLIS:  Well, humidicivity is an
           awkward variable.  All you need is a slight change in
           the surface temperature and the humidicivity
           is probably different.
                       MR. SILADY:  True.  It is going to have an
           uncertainty band that you are going to have to look at
           a .2 to a .6, or whatever, and show that it is still
                       CHAIRMAN APOSTOLAKIS:  This looks like a
           master diagram that you can use to define initiating
           events, right?
                       MR. SILADY:  It is a subset of it for that
           which is required for the DBEs.
                       MR. BORTON:  So having identified these
           SSEs, now we can look at the special treatment to
           ensure their performance, which is the fourth element. 
           The PBMR selection for the safety related equipment
           will follow a pretty typical practice.  
                       Again, we are going to look at the DBE
           consequences and show that only using the safety
           related equipment could mitigate those events.  We
           will classify the equipment during its design,
           fabrication, operation, and maintenance, applying
           special treatment to ensure its performance.
                       In the case of the PBMR, the special
           treatment requirements for classified SSEs will be
           developed based on the required functions for each
           DBE.  They have a clear road map now.
                       In this manner a clear basis will be
           established for safety related equipment, selection,
           and corresponding quality requirements over the life
           of the plant.
                       DR. BONACA:  I guess I don't understand
           that very well.  You are not bring PRA into this?
                       MR. BORTON:  No, the PRA is in this.  The
           PRA was used to look at or to define the events.  The
           special treatment was looking at the functions.  So
           you have very clear linkages now between the PRA, the
           selection of the equipment.
                       And now we could look at the special
           treatment, saying under what conditions.  What is the
           performance parameters for those pieces of equipment
           now for those DPEs.
                       DR. ROSEN:  What are the critical
                       CHAIRMAN APOSTOLAKIS:  Well, that would
           depend on the redundancy.
                       MR. SILADY:  Oh, yes.
                       CHAIRMAN APOSTOLAKIS:  So if you go
           strictly by function, you may lose that benefit.  
                       MR. SILADY:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Just saying safety
           related equipment for SSEs are the ones that support
           essential safety functions is not good enough, because
           some of these you have only one, and some of these you
           have 10.
                       So they are not of the same value, and so
           I am surprised that you are not saying that there will
           be some sort of categorization using both safety
           function considerations and PRA worth of some kind.
                       MR. SILADY:  The process uses the PRA in
           the front end to help fix the events, which are the
                       CHAIRMAN APOSTOLAKIS:  I understand that.
                       MR. SILADY:  Then if there is any event in
           that design basis region that if it were not for
           something in the design that it would be unacceptable,
           it becomes a design basis event.  
                       And then you rerun all the design basis
           events with only the safety related equipment that you
           want to rely on, and when you do that, you find out
           what the temperatures, pressures, loads, are that that
           equipment has to be designed to.
                       And in that way you define the conditions
           that it has to operate under.  And then you say what
           the performance requirements are, in terms of quality
           and so on, in order to make the assurance that it is
           going to be able to remove that amount of heat, and
           stay within that temperature and so on.
                       So the PRA was at the front end, but as
           soon as you get those events defined, it becomes more
           of a deterministic traditional approach.
                       CHAIRMAN APOSTOLAKIS:  But that's what we
           learned from that application.  You know, that a
           diesel generator is an important component, but it has
           a few thousand subcomponents.
                       The question is whether all of these
           subcomponents also safety related, regardless of what
           they do?  The utility was complaining bitterly that
           they shouldn't be.
                       MR. SILADY:  It goes function by function,
           and design basis by design basis event.  And, for
           instance, the reactor vessel has three functions that
           it has to perform.  It has to control chemical attack,
           and it has to maintain core geometry, and it has to
           radiate the heat away to remove core heat.
                       It is being made safety related for two of
           those events, for two of those functions.  For
           example, maintain core geometry so you can get the
           control rods in, or to remove the core heat.  
                       So once then you look over the spectrum of
           events, you get different conditions.  Sometimes it is
           pressurized, and sometimes it is depressurized.
                       And sometimes the initiating event was a
           leak, and you go through that whole process and you
           find what the requirements are on the reactor vessel.
           And in a similar way for each of the functions you go
           through it.
                       CHAIRMAN APOSTOLAKIS:  And they cannot go
           beyond that, because to go beyond that and do what was
           done for STP, you need to have the procedures in
           place, and you need to have operating experience, and
           you need to have other staff to make judgments that
           says that this component is not safety important as
           the other component.
                       I mean, you are missing at the design
           level from the mental elements for the --
                       DR. ROSEN:  Well, clearly you are missing
           the operational experience, but you are not missing
           the ability to look at a system and say there is a lot
           of redundancy here from a safety function, and taking
           credit for that redundancy.
           So there is a hint here being offered to you by ACRS.
                       CHAIRMAN APOSTOLAKIS:  It can't be just
           the function.
                       MR. BORTON:  What we meant by this third
           bullet is that we will have the ability to do that
           tracing back down to that level of detail.
                       CHAIRMAN APOSTOLAKIS:  We will have other
                       DR. BONACA:  I think that we have to argue
           against the design line against GDCs.  That is one of
           the issues.  What I am saying is that I think at the
           design stage that it is hard to do --
                       CHAIRMAN APOSTOLAKIS:  Well, that's where
           people commit to things that they regret 15 years
                       MR. BORTON:  And that is the point of that
           third bullet, is that we have the ability now to
           analyze to that level.
                       CHAIRMAN APOSTOLAKIS:  When in doubt, be
                       DR. ROSEN:  We are talking about one end
           of the spectrum about things that are clearly safety
           related and have important functions, and we are
           urging you to think about redundancy and taking credit
           for it.
                       On the other end of the spectrum, your
           process seems to be very clear, and clearly able to
           sort out the things that have no safety functions, and
           not spend a lot of money and time on those.
                       MR. BORTON:  Things won't be unambiguous.
                       DR. ROSEN:  Yes.
                       MR. BORTON:  Now, we have covered the
           first four --
                       CHAIRMAN APOSTOLAKIS:  Is this clear to
                       DR. ROSEN:  What is the question, George?
                       DR. BONACA:  You said that the process is
           very clear.
                       CHAIRMAN APOSTOLAKIS:  Well, it is not
           very clear.  It is just clear.  But I am not saying I
           am objecting.  I just want to read more about it.
                       MR. BORTON:  Now, having covered the first
           elements, and this brings us back to our model here,
           and just quickly going over it now.  We have looked at
           the licensing basis criteria, and licensing basis
           events, and functions and equipment, and the special
                       The last element is to compare these risk
           informed design criteria and functions with the full
           scope of regulations in order to define the scope,
           which will be able to obtain a license.  And again we
           believe that this could be done at a functional level.
                       And, number five, again it is elements 1
           through 4, could be used to determine the applicable
           regulatory requirements.  We will have to establish
           the logical rules for their selection, and Exelon
           provided an initial screening and results to the NRC
           in our letter on August 31st.
                       We also recognized by going through that
           that we are going to have to do a more detailed
           screening utilizing the four elements, and this is
           what we talked about earlier, about how that supports
           that in getting a more finer screen of the
                       We also feel that this will give us the
           ability to assess these regulations with consistency
           and repeatability, and not subject to arbitrary
           judgment.  So what we used and essentially what this
           slide is trying to say is that we use this systematic
           logic diagram.
                       It's purpose was to determine what
           regulations apply, partially apply, or don't apply. 
           However, it also has steps in it used to assess what
           regulations and guidance could be used as guidance. 
           In other words, we didn't just throw this once we
           determined that it is not applicable, we don't throw
           it out.  We look at it for guidance.
                       And again the first four elements of our
           approach help us determine what guidance is there. 
           Certainly we also look at what guidance is necessary
           that is not currently in the regulations, and we have
           a bin for that as well.
                       The results of our preliminary screening
           is that the majority of the regulations do apply,
           either as required or required as guidance.  And we
           plan to once we have some more information from the
           design, we will be able to do a finer screening and
           share that with the regulators.
                       DR. POWERS:  I guess I am a little
           confused by the drawing.  You look at regulation and
           some of them are directly applicable to PBMR, and you
           go down to what is to me the left side, you could use
           not directly applicable and you throw away.  There is
           no route out of there.
                       MR. KRICH:  Are you talking about
           partially applies?
                       DR. POWERS:  Well, what I am saying is
           that I think it is this guidance business.  For some
           reason, they applied it to the -- say a PWR.
                       MR. KRICH:  Well, maybe by example I can
           maybe help answer the question.  If we look at 10 CFR
           50.46, which is the fuel requirements, or the
           performance requirements for the fuel, that regulation
           is written specifically for LWR fuel.
                       DR. POWERS:  Right.
                       MR. KRICH:  So we said, well, that clearly
           doesn't apply.  However, we are going to need to
           develop the same type of performance requirements for
           PBMR fuel.
                       So we said that then needs to go -- that
           guidance still needs to go in there.  We still need to
           have something that applies to PBMR fuel, along the
           lines of a 10 CFR 50.46.
                       DR. POWERS:  So there is a third leg on
           this someplace?
                       MR. KRICH:  No, all the legs are here.  I
           guess I am not answering your question.
                       MR. BORTON:  We have seven dunes, really. 
           The ones that are shaded are the bins.
                       DR. SHACK:  Is there a bin for -- you have
           guidance, but is there a bin or a new regulation is
           needed, and that's what I don't see.
                       MR. BORTON:  Well, right now we are not
           going to ask for new rule making.  It will be part of
           the design application.
                       MR. KRICH:  So our intent would be that if
           in fact there is something that needs -- some
           requirement that needs to be applied to the PBMR, we
           would include it in our application.  The NRC then
           would include it in their safety evaluation report
           back to us.  So it would be imposed via that
           mechanism, as opposed to there is a written rule.  
                       DR. ROSEN:  You didn't talk about the
           deviation part of that block at all and I am
           surprised.  When you go down to the exemption request,
           typically what kind of -- there are criteria in 50.12,
           and which of those criteria do you think will be
           exercised as part of this?
                       MR. KRICH:  Well, it is hard to say.  It
           is going to be on a case-by-case basis, but I would
           imagine that typically we can meet the requirement via
           some other mechanism.  That is one of the criteria in
                       MR. FRANTZ:  This is Steve Frantz again. 
           One area where we think we may need an exemption is
           from the requirements on operator staffing in and
                       Right now those requirements are general
           and are not designed or specific state as applying. 
           Only LWRs.  But in fact when you go back and look at
           the basis for that regulation, they were developed for
                       And they probably are too stringent for
           our pebble bed reactor or other kind of passive
           reactor.  So we are looking at possibly getting an
           exemption from 50.54 requirements on operator
                       And you would look at the special
           circumstances in 50.12 and show that given a basis for
           that rule that it really does not apply to --
                       MR. KRICH:  That you could meet the
           underlying requirement without meeting the exact
           requirements in paragraph M of 50.54.
                       DR. ROSEN:  Special circumstances apply.
                       MR. KRICH:  Exactly.
                       MR. BORTON:  Okay.  Our presentation has
           gone through the bulk now, and we are looking at the
           next two sessions to have a quick comparison with the
           NRC policy and practices, and specifically advanced
           reactor policy, and risk informed guidance.
                       And then finally to cover some of the
           objectives for our pre-application.  The advanced
           reactor policy, we again in our August 31st letter
           provided to the staff a detailed comparison of the
           policy, and we concluded that the PBMR meets this
                       Some of the high level things that popped
           out of the policy are the early interactions.  Of
           course that is what we are doing with the staff right
           now in seeking their agreement on this process.
                       The same level of degree of protection,
           and we utilize the current regulations, and we develop
           our top level regulatory criteria from the current
                       The proposed specific review criteria or
           novel regulatory approaches.  I think we meet that
           with our design criteria, regulatory design criteria,
           and with our risk-informed approach.  
                       And finally providing enhanced margins of
           safety and/or utilize innovative means to accomplish
           their safety functions.  The design of the gas reactor
           is noted in the policy statement as being innovative,
           using policy -- I'm sorry, passive systems.  
                       And of course our discussion about meeting
           PAGs at site boundings will result in enhanced safety
                       DR. ROSEN:  I would point out that the
           safety criteria say at least the same degree of
           protection, and it underlined that on your chart, but
           you didn't say that in your words.
                       MR. BORTON:  I'm sorry.  The next slide is
           a comparison with the risk-informed changes and
           Guidance Document 1.174.  The first thing to note is
           that it is applicable to light water reactors and
           license amendments.  
                       However, the principles we felt provided
           useful guidance.  We also sent a letter to the NRC in
           detail providing how we meet this Reg Guide as far as
           its principles.  Some of the things that we
           highlighted was defense in depth philosophy that will
           be retained.
                       We look at providing prevention,
           termination of events, and mitigation of consequences,
           as well as providing physical multiple barriers
           through our design.  And we do have a balance between
           prevention and mitigation. 
                       Some of the other areas that we didn't
           touch on earlier is monitoring.  We looked to monitor
           fuel performance with on-line refueling.  The
           important systems like the ARCCS system, we will be
           looking to monitor that in its performance, and of
           course reactor neutronics.
                       CHAIRMAN APOSTOLAKIS:  You said that you
           had a balance between prevention and mitigation.  Can
           you elaborate on that?
                       MR. BORTON:  Yes.  I think we have another
           slide here.  Page 56, towards the end.  If you recall
           before, we were looking at that chart at the
           consequence -- what we talked about before is that we
           look at not only the consequences in ensuring that the
           safety functions could ensure that the events do not
           migrate to the right as you look at this plot.
                       We also look at the frequency as well.  We
           talked about unique situations, and if you have a high
           consequence in a very low probability area, or low
           frequency, we still have to ensure that we can
           maintain that frequency through the design in order
           for it not to become more frequent and result in
           exceeding the DBE region. 
                       MR. SILADY:  Basically, when you go to
           look at the balance between prevention and mitigation,
           you have to look at each situation individually.  In
           one case a particular SSE can serve a preventative
           role, and in another event, it can perform a mitigated
                       And so you really have to go in to each
           particular accident family and say what are the SSEs
           that are preventing this event from occurring, and
           given that it has occurred, what are the SSEs that are
           mitigating the consequences.
                       And as you go down from top to bottom in
           the risk chart, you will see this dual nature; that
           one particular SSE will be a preventive measure in one
           event, and be a mitigative in another.
                       And so it is just a question of taking a
           very careful look at the high risk events, and seeing
           which ones -- what the composite nature is over the
                       MR. BORTON:  The last slide that we have
           here is our outcomes for the pre-application
           activities, and working with the NRC.  We were looking
           for agreement on the top level regulatory criteria as
           the limiting values.
                       Agreement on the risk-informed LBE
           selection process.  Agreement on the process for
           equipment classification and the development of RDCs.
                       Comments and feedback on our approach to
           special treatment.  Agreement on the process of
           determining the PBMR applicable regulations, and the
           reasonableness of a preliminary set of regulations.
                       And finally, comments and feedback that
           our approach is consistent with the NRC current policy
           and practices, and specifically in these last two
                       Now, once this licensing approach is
           mutually agreed upon, it will form the basis in which
           we can work with the staff to resolve the other
           technical issues during the pre-application phase, and
           that concludes our presentation for this morning.
                       MR. KRESS:  Thank you very much.  
                       CHAIRMAN APOSTOLAKIS:  When were you
           looking for or by when would you like these
                       MR. BORTON:  We were looking to seek
           agreement from the NRC in the SECY that is coming up
           in November, around that time frame, so that at the
           end of the year we can make our decisions on whether
           there is a stable platform to move forward.
                       MR. MUNTZ:  We would expect the pre-
           application phase to extend until next September, and
           we would still be expecting to have that type of
                       DR. KRESS:  I think we now turn to see
           what the staff's perspective on this approach is.
                       MR. KING:  We are going to have a joint
           presentation from NRR research, who are working on
           this jointly.  Eric Benner from NRR and Prasad
           Kadamibi from Research.
                       DR. KRESS:  I propose in the interest of
           time that you skip the introductory slides that have
           already been covered pretty much, and then go to the
           slides --
                       MR. KING:  Go right to the slides that
           talk about staff perspective.
                       DR. KRESS:  Yes.
                       MR. KING:  And what you are getting is a
           work in progress.  You are getting a status report. 
           We have not finished yet.
                       DR. KRESS:  That's understood.
                       CHAIRMAN APOSTOLAKIS:  And are we going to
           have a Commission paper?
                       DR. KRESS:  You are going to have that
           Commission paper in when, November?
                       MR. KING:  The Commission paper is due at
           the end of November, and we would like you to look at
           that and give us feedback on that after your November
           meeting is what we would like.  We are not ready to
           ask for it now.
                       MR. ZEFTAWY:  You said the end of
                       MR. KING:  The paper is due to the
           Commission at the end of November.
                       MR. ZEFTAWY:  And we will get it the last
           week in October?
                       MR. KING:  We will get it to you as soon
           as we can.  It is written, but it is being edited and
           comments incorporated, and so forth.  So we have a
           package prepared.  We will get it to you as soon as we
                       But in general this whole PBMR, we have
           many more interactions that we need to have with you,
           and this is not going to be the only topic that we are
           going to talk about.
                       CHAIRMAN APOSTOLAKIS:  Do you have
           supporting documents that explain this approach?
                       MR. KING:  We have received from Exelon on
           August 31st a fairly thick package that explains this
           approach.  You should have it.  I gave copies to
                       CHAIRMAN APOSTOLAKIS:  Do you have it?
                       MR. ZEFTAWY:  No.  Are you talking about
           the one for next week maybe?
                       MR. KING:  That is the same one.  That is
           the same document.
                       MR. ZEFTAWY:  Okay.  That is the one in
           the book.
                       CHAIRMAN APOSTOLAKIS:  Okay.  
                       MR. KADAMIBI:  Basically, you have heard
           that we are talking of course on treads on the ground
           that have already been used in the past.  There was
           extensive work done on the MHGTR, and the staff put
           out a lot review documentation, and we are treating
           this as a run of the mill application of the
           regulations basically.
                       CHAIRMAN APOSTOLAKIS:  Go to the one that
           says, "Staff Perspectives, General.  Appears to be a
           reasonable and structured method for screening
                       MR. KADAMIBI:  Yes, okay.  That is number
           seven.  Well, at the level that we are talking about,
           I guess what we are trying to point out over here is
           that the four boxes that are covered by the
           possibilities in the screening process seem to cover
           it all.
                       That its regulations apply, and that they
           are partially applicable, don't apply, or they may be
           PBMR specific requirements which we might include in
           the license condition, or tech specs, or things like
                       But in terms of -- you know, what the
           method does not offer, and what we find is that it
           doesn't really offer a way to bring to the surface
           safety issues that may not have been dealt with in LWR
           space, which is when all the regulations were done.
                       But there isn't an automatic process to
           bring up potentially significant issues, but that is
           the sort of thing that we will have to cover as part
           of or as we apply the top level regulatory criteria,
           and go through the licensing basis events.
                       We would need assurance that in fact that
           is a sufficiently comprehensive and complete set to
           support the regulatory decisions.  But the other point
           that we wanted to make over here is that there isn't
           right now on the table anything that is a substitute
           for cool damage frequency and/or any kind of a large
                       But one could foresee that there would be
           things like just a calculated peak temperature within
           a few -- a pebble bed.  You know, that would serve as
           a surrogate in the same way that CDF has served.
                       CHAIRMAN APOSTOLAKIS:  Why?  Why would you
           need that?
                       MR. KADAMIBI:  Well, the actual core
           damage that I guess is in a light water reactor does
           not apply in a pebble bed.
                       CHAIRMAN APOSTOLAKIS:  I understand that,
           but why are you looking for something to replace it
                       MR. KING:  It gets back to your question,
           George, of the balance between prevention and
                       CHAIRMAN APOSTOLAKIS:  Okay.  That's what
           I wanted to hear.
                       MR. KING:  And what we saw on the curve,
           the blue curve, was -- well, after you go through the
           accident, here is what you get off-site basically.
                       CHAIRMAN APOSTOLAKIS:  That's right.
                       MR. KING:  It was nothing that dealt with
           the prevention piece, and so that is the issue.
                       MR. KING:  If the Chairman of the
           Subcommittee agrees, can you tell us where you
           disagree with what we heard, because a lot of this
           stuff -- well, of course you have to be perceived as
           being independent, but are there any points where you
           disagree with what Exelon presented, or you don't
           really disagree, but you really want to think about
                       MR. KADAMIBI:  I guess the level of
           agreement at the high level, in terms of where the
           four boxes in fact cover the range of eventuality, we
           agree there.  But actually when you come down to what
           regulations apply or don't apply, I think we may have
           significant disagreements.
                       CHAIRMAN APOSTOLAKIS:   Sure.   
                       MR. KADAMIBI:  And we haven't really gone
           through that.  We haven't really gone through on our
           own either that or a similar process.
                       CHAIRMAN APOSTOLAKIS:  That's fair enough.
                       MR. BRENNER:  I think what we see is that
           the licensing approach provides a very good construct
           by which the applicant and the staff are going to be
           able to bring safety issues to the table, and discuss
           those issues.  
                       While not detailed in the licensing
           approach, we have had a number of meetings with
           Exelon, and we have pointed out to them that one of
           the things that the staff is going to need to do is be
           able to bring new tables, events, and put them on the
           table to see where they fall given the events they
           have selected.
                       And they fully agree, and they say that is
           an inherent part of the licensing approach.
                       CHAIRMAN APOSTOLAKIS:  And you are
           comfortable with the blue curve?
                       MR. KADAMIBI:  Yes, as a starting point
           for the discussion.
                       CHAIRMAN APOSTOLAKIS:  Oh, that is such an
           answer.  Oh, you have been here before.  Very good.
                       DR. WALLIS:  What he said before I thought
           was significant.  I mean, what we seem to be going
           through here is Exelon tells you how you should
           license their reactor, and I think you ought to be
           telling them.
                       And you were saying that you have not yet
           gone through a process like theirs to decide how you
           would license the reactor.
                       MR. KADAMIBI:  That's right.
                       DR. WALLIS:  And doesn't that have to be
           done rather than just accepting what they asked for?
                       MR. KADAMIBI:  Well, the stage at which we
           are does not really reflect an acceptance of
           everything.  It is really an acceptance of the
           validity of the approach, where you go through a
           screening of the regulations, and you develop some
           kind of an objective basis for judging acceptability
           and unacceptability, and trying to deal with those
           issues that are going to be very difficult.
                       And there is a proposal on the table, and
           we have got to begin somewhere, and we are going
           through it.  We only got their application -- I mean,
           their submittal -- on August 31st, and so we haven't
           really had much time to --
                       CHAIRMAN APOSTOLAKIS:  I don't know how
           much the fact that you have to write something by
           November and when you received it at the end of
           August, continues to the continued assurance of
           regulatory independence.
                       I mean, I agree with Professor Wallis that
           the approach may be technically sound, but boy, this
           really doesn't look very good.  They are telling us
           how to license their reactor.
                       MR. KADAMIBI:  Well, we are very sensitive
           to that perception, and at the same time the
           Commission has asked us to engage in early
                       CHAIRMAN APOSTOLAKIS:  And that's very
                       MR. KADAMIBI:  And so we are engaging in
           early interaction, and we will maintain independence
           and bring up the kinds of questions that -- well, I
           think the basis for our regulatory review will to some
           extent naturally bring up -- such as Reg Guide 1.174.
                       If we look at really how it applies in
           terms of defense in depth, Reg Guide 1.174 lays out
           seven attributes that we would look at, and we could
           use those as guidelines.  
                       One of the things that we noticed is that
           they only used six of those seven.  Now, because this
           is an ongoing interaction, we don't necessarily know
           why only 6 of the 7 were chosen.
           But probably there is no reason to exclude any of
           those seven.
                       DR. BONACA:  Another thing is that I don't
           think that they are proposing regulation.  I think
           they are proposing a way in which they can license
           this plant under existing regulations it seems to me.
                       DR. KRESS:  That's my opinion, and I don't
           think you should let the concept of lack of
           independence color your view too much.  I mean, if you
           agree with the proposed approach as having a lot of
           merit, I would urge you not to let the concept of a
           perceived lack of independence color that.
                       MR. KADAMIBI:  Well, we have to assure
           ourselves that we have a sound basis for that.
                       DR. KRESS:  I think you are going to have
           to look at it and see if it is a sound basis, and is
           going to protect the health and safety of the public.
                       MR. KING:  Ultimately that has to be the
           staff's licensing criteria.
                       DR. KRESS:  It will be the staff's
           licensing criteria, no matter where it comes from.
                       MR. KING:  Whether the bright idea comes
           from the staff or somebody else is secondary.
                       DR. KRESS:  That's right.  You certainly
           don't want to dismiss a bright idea just because it
           came from outside.
                       DR. POWERS:  When you think about this
           licensing process, do you think about it as here is a
           site with a control room and a reactor, or do you
           think about it as a site with a control room and 10
                       MR. KADAMIBI:  We haven't really gotten to
           that point yet.  I myself have not given that any
           thought.  I don't know about Eric.
                       MR. BRENNER:  And we early on, there was
           some discussion between us and the potential
           applicant, and the applicant stressed that they wanted
           to focus on the approach, versus the design. 
                       So to that extent, we have tried to not
           look at particular aspects of the design, but look to
           make sure that the approach can handle questions like
           that of, well, okay, because this is different from
           how we have maybe licensed plants in the past, will
           there be a way for the staff to interject those issues
           as the applicant is working through the licensing
                       And that sort of thing has been the focus
           of our judgment of acceptability, versus
           unacceptability, for the approach; as opposed to
           acceptability for --
                       DR. WALLIS:  Well, you knew that you had
           to face this licensing of unusual reactors, and it
           would seem to me that the staff would know it before
           it saw anything from industry to look at the
           regulations and say how are we going to do it.
                       And to have some ideas generated here, and
           not coming all from outside, about how to license
           these new reactors.  I have not seen any independent
                       All your presentation here is based on
           ideas that came in from outside.  Weren't there some
           ideas here before you got ideas from outside?
                       MR. BRENNER:  Yes, and two of the things
           that we have looked at already is the previous
           licensing of gas cooled reactors that the NRC has
           done, and we looked a lot at --  
                       DR. WALLIS:  So you had your own blue
           curves and things like that, or some sort of curve,
           before you saw these that came in from outside?
                       MR. KADAMIBI:  The way that I would put
           it, Dr. Wallis, is that even if we used the curve as
           some kind of value in what we are doing, what we use
           it for could be quite different from what they used it
                       DR. WALLIS:  Did you have any ideas before
           ideas came in from outside, and what did they look
                       CHAIRMAN APOSTOLAKIS:  Did the Option 3
           report help you at all?
                       MR. KADAMIBI:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And would that
           serve a purpose of the thinking that Dr. Wallis wants? 
           Was there anything there that would apply to these
                       MR. KADAMIBI:  Well, Option 3, I believe,
           was to support rule making.
                       CHAIRMAN APOSTOLAKIS:  Well, 1-174 was to
           support the request for changes, but now it is used
           for other things.  
                       MR. KADAMIBI:  Well, we have gone through,
           I think, a relatively and systematically way to find
           the principles in Reg Guide 1.174, and I think we see
           a very clear application of some of the basic
                       In terms of the Option 3, I think the
           concepts of prevention and mitigation, and how one can
           use quantitative analyses will be very useful.  But
           exactly how they might be useful, I don't think we
           have come up with that yet.
                       MR. KING:  The Option 3 work is very
           useful.  Option 3 categorized events by frequency
           categories.  That thinking applies to the thinking we
           heard from Exelon.  
                       You know, the same kinds of questions that
           we had to wrestle with there are the same kinds of
           things that have to be addressed in this proposal; the
           balance of prevention mitigation, and that stuff
                       CHAIRMAN APOSTOLAKIS:  Yes, but there is
           no discussion of it here, and that is what Dr. Wallis
           is saying.  I mean, all you are doing is you are
           responding to what --
                       DR. BONACA:  Well, I want to say that for
           older plants that you could take right now the
           combination of ANSI standards, Chapter 15, and SECY
           goals, and draw the same curve that they have, and it
           would be with a band around it because they wouldn't
           have some foundation.
                       But all I am trying to say is that this is
           not a revolutionary approach.  It is an approach that
           has been used before.  You have not seen a blue curve,
           but you saw pieces of it in different portions of the
           regulation that you had to meet in order to license
                       So I am saying that I don't think it was
           a strikingly or radically different approach.
                       DR. KRESS:  But it puts it all together
                       DR. BONACA:  It puts it all together.
                       DR. KRESS:  And in fairness to the staff,
           this particular presentation was supposed to be what
           was their perspective and response to the Exelon
           proposal.  We weren't asking them to say what else is
           out there that they might do.  I am sure that they
           will think along those lines.
                       MR. KING:  Or if we took a clean sheet of
           paper what would we come up with.
                       DR. ROSEN:  I think that Prasad made that
           very clear in his remarks, that they are thinking
           beyond what the Exelon people put on the table.  
                       And then the statement of what else does
           the staff -- what things will fall outside this
           protocol if that needs to be brought to the table.  If
           you just use the protocol that they suggested and put
           blinders on, clearly you may miss some things.
           And I think that Prasad was quite clear that that is
           not what the staff was doing.
                       CHAIRMAN APOSTOLAKIS:  Well, Exelon, in
           their last slide, stated that they wanted agreement
           from the staff on six processes.  You know, an
           agreement on the process for equipment classification
           and the development of RDC, et cetera, and that is due
           up to the Commission by the end of November.  That
           SECY will do that, will address these?
                       MR. KING:  That SECY will go as far as we
           can go in November.  We may have some IOUs in that
           SECY for follow-up activities.
                       CHAIRMAN APOSTOLAKIS:  You guys need at
           least a month for reviews.  So, we are talking about
           lightening speed here in approving all these things or
                       DR. ROSEN:  But where does the ACRS get
                       CHAIRMAN APOSTOLAKIS:  We don't.  I guess
           they are going to give it to us at the last moment.
                       MR. KING:  Well, we will get the draft
           SECY hopefully in a few weeks.  We would like to get
           your views on it.  As I said the SECY will go as far
           as it can go.  
                       The reason that we picked November was
           because when we first sat down and laid out our pre-
           application plans and discussed it with Exelon, they
           were looking for feedback as soon as they could get
                       We thought that the earliest that we could
           get them something would be November.  It may not be
           everything that they want, but we are trying to be
           reasonable, in the sense that they have decisions to
                       And they are looking for feedback, and we
           are trying to get them whatever we can get them by the
           end of the year.  It gives the Commission a month to
           look at it.
                       DR. BONACA:  I have a question that I
           would like to ask you here.  Regarding the blue curve,
           we heard from Exelon that it is not a frequency
           consequence curve.
                       But in your presentation, you are calling
           it a proposed frequency consequence curve.  I mean, is
           there confusion there on what it is and how they are
           using it?  
                       MR. KADAMIBI:  Our view on this is that
           the actual numbers on there may or may not mean a
           whole lot other than representing something that is of
           a fundamental regulatory value, which is that the
           higher the consequences, the less likely it should be. 
           And this generally represents that concept.  Also --
                       CHAIRMAN APOSTOLAKIS:  There is some
           contributions or on individual sequences, and that is
           a conceptual problem that has nothing to do with the
                       DR. BONACA:  Absolutely.
                       CHAIRMAN APOSTOLAKIS:  The frequency
           consequence curve means cumulative.  Now, if that is
           the wrong interpretation and is interpreted in a
           different way --
                       DR. WALLIS:  They are not talking about
           concepts.  Everybody understands concepts.  We are
           talking about hard criteria that you are going to
           apply to license or not license a reactor.
                       MR. KADAMIBI:  Well, that curve I don't
           think will be the hard criterion.
                       DR. WALLIS:  Well, what are they, or what
           ideas do you have about what they might be?
                       DR. KRESS:  What is already in the
                       DR. WALLIS:  What is it that you need to
           invent or change, or whatever?
                       DR. KRESS:  The design or the selection of
           the design basis and events that will have to meet the
           regulations.  That is what this is about. 
                       MR. KING:  They have not selected a design
           basis and --
                       DR. WALLIS:  Did you know the blue curve
           before it was shown to you by Exelon?
                       MR. KADAMIBI:  It was part of the MHGTR. 
           It wasn't new and the concept has been around.
                       DR. WALLIS:  So the idea that they are
           showing you something is wrong.  You knew this before
           they showed it to you?
                       MR. KADAMIBI:  I got it from NUREG 13-38,
           which is where the staff reviewed what MHGTR had
           proposed, and we are offered is something that the
           staff has spent a considerable amount of time
           reviewing in the past.  So we want to take as much
           advantage of that as possible.    
                       DR. WALLIS:  Well, we knew all of this
           beforehand because you had been through it before, and
           therefore, you are in a good position to evaluate it. 
           So, I wouldn't do away with the impression that it is
           something that came all from outside in some way.
                       MR. KING:  If you were expecting we were
           going to come in here with a design basis, the
           accidents, the GDCs, and all the other criteria that
           we have now decided to apply, we are not ready to do
                       DR. WALLIS:  No, I just wanted to get away
           from the impression that Exelon is telling you how to
           do the regulation.
                       DR. KRESS:  Exelon is telling them what
           the regulations already consist of.
                       DR. WALLIS:  Well, why do they have to
           tell you?
                       DR. KRESS:  Well, they knew that.  They
           are just putting it down on paper so that it is a
           point of focus.
                       MR. KING:  What they are telling us is
           that how they propose to go through the regulations
           and decide what applies and doesn't apply to PBMR.
                       DR. KRESS:  Yes.
                       MR. KING:  Their ideas as to how they
           would like to do it and how they would like us to
           agree with the way they would like to do it.  Our job
           is to take a look at that and say does that sound
           reasonable or not, or do we have another way that we
           think it ought to be done, and that is what we are
                       DR. ROSEN:  I think that Exelon is free to
           propose anything that they want, but one thing that
           Exelon can't do is license a reactor.  That can only
           be done by the Commission, and that is what we are
           doing.  That is what we are looking at.
                       CHAIRMAN APOSTOLAKIS:  I guess Graham's
           point is different though.  He is saying that instead
           of starting that way, and where you have a proposal
           from the applicant, and you say, gee, here I agree or
           there is another way, he is saying why haven't you
           thought about other ways before you got that.  I think
           that is the thrust of his question.
                       DR. KRESS:  Yes, but once again, this is
           the way in principle that they have been licensing
           reactors for years, and it is just putting it down in
           a systematic focus and basis.
                       DR. POWERS:  The difficulty that I am
           having here is that this is exactly the way they have
           been licensing reactors for years, and should that be
           the way that we do things?  
                       I mean, shouldn't we say what is the
           safety that we are trying to achieve, and then define
           what regulations you need to achieve that?  And then
           see which ones you have and which ones you don't have?
                       DR. KRESS:  Yes, and to complete that
           picture, I would have liked to have seen the
           cumulative curve --
                       DR. POWERS:  I am not wild about that, but
                       DR. KRESS:  But that would have defined
           what we were trying to achieve, and this is a way to
           achieve that, although there is a disconnect between
           them.  It is not clear how this leads to achieving
           that other one.
                       But it is the same thing, and it is not
           clear how the design basis accident now leads to
           achieving the safety goals.  And you can meet those
           rules and regulations by many different paths.
                       CHAIRMAN APOSTOLAKIS:  I think you are
           going to have a hell of a problem with defensing that;
           picking it out of 1.174 is --
                       DR. KRESS:  I think the issue is going to
           come down to what in the heck do you mean by defense
           in depth.
                       DR. POWERS:  Well, you have the challenge
           of with your frequency consequence curves, there are
           some high frequency things that you are going to allow
           to occur, upside events that you are going to allow to
                       And it seems to me that I may be
           substantially more conservative than you and say that
           I don't want that kind of thing to occur, period.
                       And I think there is more than just
           defense-in-depth that is going to be a problem.
                       DR. ROSEN:  I see another big problem, and
           that to me is the risk matrix.  I have to define a new
           set of risk matrix, and --
                       DR. POWERS:  Well, I think that CDF is
           shot here.
                       DR. ROSEN:  Clearly, but I didn't hear
           much thinking about that from either the licensee or
           the staff.
                       DR. KRESS:  Well, the matrix may be on the
           bottom curve there; frequency of which you exceed a
           certain dose there.
                       DR. ROSEN:  But now the ACRS is defining
           risk as --
                       DR. KRESS:  Well, these guys know that is
                       CHAIRMAN APOSTOLAKIS:  You know, I am
           really curious.  Maybe it sounds like a crazy idea,
           but I would really like to understand or know how 
           many times has industry and regulators which have been
           surprised by operating experience in the last 40
           years, because that tells me a lot about defense-in-
                       DR. POWERS:  Can you ask the question
           again, George?
                       CHAIRMAN APOSTOLAKIS:  How many times have
           we as a community been surprised by the operating
                       DR. POWERS:  A bunch.
                       CHAIRMAN APOSTOLAKIS:  Well, I would like
           to understand that.  I mean, that would be a nice
           little project, because that tells me how cautious I
           have to be for the future, which means defense-in-
                       The words are coming are out with great
           difficulty, but it is the structure of the approach to
                       DR. POWERS:  It is the correct approach.
                       DR. BONACA:  Mr. Chairman, we are
           hopelessly late.
                       DR. KRESS:  Can you guys summarize?
                       MR. KADAMIBI:  Well, if I were to
           summarize, I would go to slide 12.  This is really
           what -- this really captures many of the concerns that
           I have heard expressed over here and these constitute
           the central challenges that I think we face.
                       And we are cognizant of it, and the burden
           is heavily on the staff in order to deal with these
           issues.  At this point, I don't think we have really
           seen enough about the substance of the repeat PBMR
           design in order to be able to say very much about any
           of these.
                       DR. WALLIS:  Well, I think you have a
           great opportunity here to relate the top level
           regulatory criteria, and the real question of adequate
           safety and all that to the way that you apply them to
           this new thing.  
                       You have a wonderful opportunity to make
           things more rational than they were in the past.  I
           think just responding to someone else's idea just
           isn't good enough.
                       CHAIRMAN APOSTOLAKIS:  What do you mean by
           enhanced level of safety margins?
                       MR. KADAMIBI:  Well, that is an
           expectation I believe of the Commission, in terms of
           we don't require or we don't really require a higher
           level of safety, but through applying concepts of
           simplicity and passive systems, and things like that,
           we would expect that there would be an enhanced level
           of safety.
                       CHAIRMAN APOSTOLAKIS:  Okay.  Thank you,
           Gentlemen, and thanks to Exelon for their
           presentation.  We will reconvene at 5 minutes past
                       (Whereupon, at 1:05 p.m., a luncheon
           recess was taken.)
           .                     A-F-T-E-R-N-O-O-N   S-E-S-S-I-O-N
                                                    (2:05 p.m.)
                       DR. BONACA:  All right.  Our Chairman had
           to leave for a few minutes, and so I will be chairing
           this part of the meeting.  Right now we are going to
           review the action plan to address ACRS comments and
           recommendations associated with the differing
           professional opinion of steam generator tube
           integrity, and I will turn to Dr. Powers, who is the
           Cognizant Engineer.
                       DR. POWERS:  The Chairman of the
           Subcommittee will present a summary and that Chairman
           is Dr. Ford, formerly of General Electric.
                       DR. FORD:  I will do exactly the same as
           you did.  I will handle the Chairmanship.
                       DR. POWERS:  I thought you were going to
           offer an opening summary.  
                       DR. FORD:  I will let you do that.
                       DR. POWERS:  Well, being caught completely
           flat-footed here, that the objective is for the staff
           to come up and discuss a little bit on what they are
           doing in their steam generator action plan.  
                       I understand that this is an action plan
           that has existed for some period of time, and has been
           augmented by the staff to address some of the comments
           and recommendations we made in the report that the
           Committee endorsed on the differing professional
           opinion concerning steam generator tube integrity.
                       I think that you will find that the staff
           has gone more beyond than just looking at some of our
           explicit recommendations, but rather has very
           carefully scrutinized the report, because in many
           places in the text we come along and say here are some
           thoughts and comments on this, and they have taken
           them to heart.
                       And they have come up with a plan that
           seems to address most of our comments.  But what I
           don't know is who is the speaker is going to be.  And
           let me go on and say that we did have a subcommittee
           meeting on this, and a substantial portion of the
           plan, or some portion of the plan, has been relegated
           to research to address.
                       And they have some very exciting results
           that are going to be presented to the Committee, and
           more for interest than they are for reviewing.  So,
           with that --
                       MR. SULLIVAN:  Well, all I am going to do
           is make some opening remarks.  There is not too much
           that I have prepared on this little sheet that you
           didn't already go over, but since it is very short, I
           will just go quickly through it again.
                       My name is Ted Sullivan, and I am the
           section chief in NRR responsible for steam generators. 
           In November of 2000, NRR prepared a steam generator
           action plan that addressed the activities that we were
           going to undertake in response to the Indian Point-2
           lessons learned task group report.
                       And the related OIG event report on Indian
           Point-2, and other ongoing activities related to NEI
           97-06.  So that is what we did in late 2000.  Then by
           the time of May, after we had had time to study in a
           fair amount of detail the recommendations in the ACRS
           report related to the DPO, which is NUREG 17-40, we
           expanded the action plan to address the activities
           that we were going to undertake in response to those
                       The major activities as Dr. Powers
           indicated are being undertaken -- I think you did
           indicate this, but they are being undertaken by the
           Office of Research.
                       We understand that as a couple of people
           have said already that the purpose of this portion of
           the meeting is to understand how NRC is responding to
           the recommendations of the ACRS on the DPO. 
                       And what we intend to do for the rest of
           this hour is to present a summary of the work on the
           near term research milestones on the actual plan, and
           that is what Dr. Powers was alluding to.
                       DR. POWERS:  One thing that I would
           correct you about is that I don't attach anything
           minor -- well, the word minor does not come to mind
           when I think about those activities that NRR is
           responsible for in the action plan in responding to
           the recommendations.
                       MR. SULLIVAN:  I would agree, but I think
           that in terms of resource expenditures --
                       DR. POWERS:  That may be true, but the
           resource expenditures I agree with you, but I think
           the things that are going on to look for significant
           deviations from the expected linear response, I think
           that is an extraordinarily important activity, and
           minor is just not a word that I would attach to it.
                       MR. SULLIVAN:  Okay.  I would agree with
           that.  I also wanted to let you know that we are not
           going to hit the entire steam generator action plan
           today or even all of the DPO issues.  
                       But there is a description of the
           milestones related to all of the action plan, but in
           particular the DPO, on a web page that has
           specifically been created for the steam generator
           action plan.
                       And the staff's progress on those
           milestones is updated quarterly.  So if you want to
           track that between meetings that is available.  And I
           guess with that, I would just turn this over to Joe
           Muscara, who is going to lead off these presentations.
                       DR. POWERS:  Never let it be said that a
           metallurgist can't handle a few engineering activities
                       MR. MUSCARA:  Good afternoon.  I guess by
           way of introduction, some of the things that I was
           going to say have already been said, but maybe I will
           just repeat them.  
                       One of the points of interest was that
           when the staff reviewed the RES report, we didn't just
           look at the recommendations.  We studied the report in
           detail, and when ever we found errors where there was
           an interest or a lack of information, we decided to
           address those issues also.
                       The report actually helped us to focus the
           research and to get support for it.  I would also like
           to point out that much of the work was ongoing, and is
           ongoing.  So they have helped us to address in the
           near term some of the issues that were represented in
           the report.
                       As has been mentioned, we do have an
           action plan, and this is updated monthly.  So the
           current status of the work to address the DPO issues
           is available in the action plan.
                       What we were planning on doing today was
           to essentially address some of the recently completed
           research, and also to talk about some of the near term
                       So I will be discussing the work related
           to materials and inspection, and Chris Boyd will give
           us an overview of the thermal-hydraulics work.
           And he will also address some results from CFD
           calculations that he has completed recently.  
                       Now, Milestone 3.1 in the action plan
           deals with understanding any possible crack growth
           during a main steam line break.  The work that we are
           planning on doing here, we will be looking at some
           thermal-hydraulics evaluations to calculate the loads
           that are experienced by the tubes in these conditions.
                       This will be conducted by the staff.  We
           will also be looking at work that has already been
           performed and that is available in dockets.  Based on
           this review and in conducting thermal-hydraulics
           evaluations, we will come up with some upper-bound
           estimates of the loads.
                       And then with these kinds of input, we
           will evaluate the growth of existing range and types
           of cracks to see whether these cracks will propagate
           under the steam line break loads.
                       We will also be estimating the loads that
           are required to propagate a range of cracks, so that
           we can get an idea of the margin for propagating these
           flaws over and above the main steam line break loads.
                       At this point if we find that there is a
           great deal of margin, I think we do not need to do any
           further work to better define the loads, but if we do
           not have large margins, we will then do additional
           work in the thermal-hydraulics area to better define
           the loads.
                       Much of this work will be completed by the
           end of the next calendar year.  Once the evaluations
           have been completed, we will also conduct some tests,
           including both the pressure stresses and axial and
           bending stresses, to essentially validate our findings
           from other core results.
                       DR. POWERS:  Isn't it a case that the
           loading on the tubes is simple; that we have complex
           multi-dimensional loading that complicates these
                       What the subcommittee was thinking of were
           in terms of the support plates, oil canning, and even
           painting.  And we looked upon those as very
           complicated loads that might be difficult to assess
           the magnitude of strictly by analysis.
                       MR. MUSCARA:  Well, we will have to
           monitor that situation.  I think the worse condition
           is when the tube is locked between support plates. 
           And then we should be able to get some input from the
           thermal-hydraulic calculations on the kind of force
           that the support plates are experiencing at a
           particular location.
                       And then we will evaluate what kind of
           loads resulting from that, including body weight
           cyclic loads.  And then we will evaluate the growth of
                       And then in the testing itself, we will
           try to simulate the kinds of loads that we predicted
           in the tubes.
                       DR. POWERS:  I know it is probably too
           soon to ask the question, but I will ask anyway.  You
           have two tube support plates, and if they go into
           oscillation, they don't need to be in-phase do they?
                       MR. MUSCARA:  I suppose not.
                       DR. POWERS:  And that would create just a
           horrific situation I think.
                       MR. MUSCARA:  Well, those are the kinds of
           things that we have to be looking at.
                       DR. SHACK:  And they are sort of coupled
           by about 5,000 tubes though. 
                       MR. MUSCARA:  Well, there are assumptions
           that the overload is transmitted to one tube, but many
           of these tubes are a lot.  
                       DR. BONACA:  So now some tubes may be a
           lot and some may not. 
                       MR. MUSCARA:  Right.
                       DR. BONACA:  So you will have to look at
           what some range of sensitivity might be.
                       MR. MUSCARA:  Some range, and we have to
           make conservative assumptions about the numbers of
           tubes that may be a lot.
                       DR. WALLIS:  Has anybody got any estimates
           of these loads so that you know what sort of thing you
           are dealing with before you go on to something more
                       MR. MUSCARA:  There have been several, and
           maybe a couple of submittals from the utilities, where
           they want to take advantage of the support plate being
           logged, and they are requesting the use of a higher
           voltage and voltage lows, and in that work they have
           conducted a number of analyses to try and predict
           those lows.
                       And we will be reviewing those, and in
           addition we will be doing our own hydraulic
           calculations to see how close these are.  
                       DR. POWERS:  Well, even relatively simple
           axial and bending loads have been done as part of
           setting up the alternate repair criteria.
                       MR. MUSCARA:  I think in that case that
           they are assuming that the support plate was not
           there.  So they do not have to go through that
                       In Milestone 3.2, we were interested in
           evaluating the effects of jets impinging on adjacent
           tubes, both under severe accident conditions, and
           under steam line break conditions.
                       Last year, we presented some results to
           the ACRS on work that had been conducted with respect
           to the erosion of tubes due to the erosion impact from
           severe accidents, and we had concluded at that time
           that the degradation was very minimal and that this
           was not a concern.
                       And the ACRS recommended that we should
           possibly run some longer term tests.  Our original
           tests were 10 minute tests, and so we have since
           conducted some tests of a duration of 30 minutes.  
                       And we have found that we have exactly the
           same data, and so even with the 30 minute testing, we
           still have very low rates of erosion under those
           conditions.  And the rates range from somewhere
           between 2 and 5 mils per hour.  So we still that is
           not an issue.
                       We conducted a number of tests to evaluate
           jet impingement on the steam line break conditions. 
           Much of that work is completed, and we are doing some
           validation work right now on real cracks.
                       But I would like to show you some of the
           data from those tests since you have not seen it
                       DR. WALLIS:  How do you characterize the
           jet?  It is a two-phased jet?
                       MR. MUSCARA:  A two-phased jet.  Last
           year, we presented work on CFD evaluations to get the
           properties of the jet velocities, and temperatures,
           and we made use of that information.
                       DR. WALLIS:  Well, did the tests make an
           effort to model the upstream conditions for the jet
           and everything, and to get the jet velocities and
           quality, and everything right?
                       MR. MUSCARA:  In the severe accident work,
           we used the rig at the University of Cincinnati, where
           we were essentially using a burner.  We injected
           particles into this burner, and we worked on a range
           of velocity conditions; from very little, and up to
           about a thousand feet per second or meters per second.
                       We also found in that work, and based on
           the CFD conditions, that when the jet impinges on the
           tube, the velocity is down pretty much to nil.  In our
           evaluations, we assumed the velocity of 200 meters per
           second.  So we were conservative in that respect.
                       DR. WALLIS:  Isn't that jet a steam water
                       MR. MUSCARA:  No, under severe reactor
           conditions it would be an aerosol, and materials
           evaporate from the core.
                       DR. WALLIS:  Okay.  So you have to model
           that somehow.
                       MR. MUSCARA:  Right.  In a steam line
           break, when we have a blow down facility, we reproduce
           the conditions inside the tubing and outside of the
                       Of course, on a steam line break, there is
           no atmosphere on the outside.  So we have conducted
           those tests under 2400 psi pressure, at a range of
                       And we find that the amount of erosion is
           dependent on the temperature, and it is dependent on
           the amount of sub-cooling.  The greatest amount of
           erosion occurs about 280 degrees centigrade, which is
           about the cold wet temperature.
                       We would not expect to see -- well, cracks
           are less likely in the cold leg, and around 300
           degrees C where we have the hot leg temperatures, the
           erosion rates are quite diminished.
                       DR. WALLIS:  Do you understand the reason
           for this dramatic bump in the curve; the mountain of
           erosion that occurs over a narrow range of
                       MR. MUSCARA:  Again, we need to look that
           this is a two hour test, and at 2400 psi, and the peak
           is about 27 or 28 percent.  
                       DR. WALLIS:  But why does it suddenly
           change under a certain temperature?
                       MR. MUSCARA:  Well, as the temperature
           goes up, we are starting to get some flashing, and so
           the jet dissipates.
                       DR. WALLIS:  So that is the place where it
           changes its two-faced conditions or something like
                       MR. MUSCARA:  We think so, because based
           on evaluating the condition of the surface, we would
           see a larger area that is being affected.  Also, as we
           penetrate into the tubing, then there is water present
           at the bottom and that acts as a cushion.
                       So the tests that we conducted for longer
           times would not get any greater penetration than --
                       DR. WALLIS:  Is this a condition where the
           jet forms bubbles, which then collapse by cavitation
           on the target?
                       MR. MUSCARA:  No, we don't believe that is
           the case under these test conditions.  
                       DR. SHACK:  Well, I have a conflict of
           interest here, but at the 300 and 320, the jet will
           flash obviously given enough time under all these
           conditions, because it is under pressure and
                       But since it is a transient thing, we can
           sort of see from the impact area that it hasn't
           flashed at 280 or lower temperatures.  There is no
           flashing that goes on.  The diameter of the impact
           area is the same as the diameter of the exit hole.
                       And at 300 to 320, it is flashy.  You
           know, the impact area is spread out.
                       DR. WALLIS:  And so that is more benign?
                       DR. SHACK:  That is more benign.  You
           know, we are getting small droplet impacts.  The guess
           is that we are getting a short of bundle cavitation
           damage there at the peak, and when it drops off again,
           we are not getting the cavitation damage.
                       But it is very difficult to really know
           anything except that the peak goes up and the peak
           goes down.
                       DR. WALLIS:  But there is a small window
           there where you will form bubbles in the jet and it
           can collapse on the target.  You have to have just the
           velocities and temperatures just right for that to
                       DR. SHACK:  And it seems to be that degree
           of sub-cooling that you just happen to get in the cold
                       MR. MUSCARA:  We are currently conducting
           additional tests at different pressures, and so we are
           trying to understand this better.
                       DR. WALLIS:  Is there literature on this
           bubble formation cavitation in a jet which is close to
           flashing?  Is there literature on that?
                       DR. SHACK:  We can't find any. 
                       DR. WALLIS:  I remember that I thought
           about it in various circumstances, and I don't know of
           any literature either.
                       DR. WALLIS:  There is lots of literature
           ont the droplet impact, but --
                       DR. WALLIS:  No, that is not it.  It is
           the bubbles that have to form, and then they have to
                       DR. SHACK:  And it clearly is a lot more
                       MR. MUSCARA:  We are planning on providing
           some topical reports by the end of the calendar year
           to describe the work on the jet impingement under
           severe accident conditions, and also on main steam
           line break conditions.  
                       So there should be a lot more detail
           available at the end of this calendar year.  Milestone
           3.6 of the action plan addresses the issue of the POD. 
           And the ACRS made some comments as to the possible
           better use of other parameters rather than a constant
                       Fortunately, we have been doing work in
           this area for a number of years, and we were trying to
           quantify the ability of flood detection using current
           techniques and commercial teams for realistic kinds of
                       We had completed work in the past, but we
           recently completed some of the analyses of this work,
           and I thought it might be useful to show you some of
           those results.  
                       The POD that we are using now is a
           constant number of .6 POD for any size or any voltage
           flaw.  Without going through a great deal of detail,
           what I wanted to show you is that we now have data on
           the POD as a functional flaw depth, and as a
           functional voltage; and four different kinds of flaws
           in different locations; ID and OD SCC at the support
           plate, and at the tube sheet, and the free span.
                       And besides depth, flaw depth and boltage,
           we were also evaluating the data against the parameter
           MCP.  This is a fracture mechanics parameter, and MCP
           describes essentially the stress consideration in the
           ligament at the cracked tip.
                       MCP is a functional of both the flaw
           length and depth.  So it is very strongly dependent on
           flaw geometry, and of course this dictates the failure
           of pressures of these tubes.
                       And so we have also plotted the
           probability of detection for flaws against this MCP
           parameter, and a MCP value of about 2.3 is that
           location where the flaw can no longer meet 3 delta-P
                       So what we can see from these foils is
           that for MCP that around 2.3 probability detection is
           fairly high.  So a flaw that would fail under 3 delta-
           P would be quite detectable.
                       And just to give you a feeling for the
           team performance, the last view graphs are based on
           the results from 11 teams, and in these graphs we are
           showing the performance on a team by team basis.
                       DR. WALLIS:  So the probability of
           detection is very dependent on the people?
                       MR. MUSCARA:  That is what this graph
           shows for some conditions.  You will notice --
                       DR. WALLIS:  Especially the one on the
           bottom right.
                       MR. MUSCARA:  Right.  At the top, we have
           the cracking and tube support plate cracking, and
           these are fairly common cracks, and so you expect to
           see these quite often.  
                       What we see at the bottom is work on POD
           on the free span, and of course we don't get a lot of
           flaws in the free span, and so sometimes these confuse
           the inspectors, and they are not willing to call it a
           flaw, and they think it is something else.
                       In the bottom right we are showing
           information on the POD for the tube support plate
           location from stress corrosion cracking on the inside
           diameter.  Many of our flaws that are stress corrosion
           cracking on the inside diameter are also accompanied
           by denting.
                       Now, the denting produces a fairly large
           complex signal, which makes the detection more
           difficult.  So there is a signal there, but the
           inspector is to decide if this is a flaw or not.  Is
           it a flaw, or is it the signal from the dent.
                       And clearly some inspectors do quite well,
           but then some other inspectors don't do quite as well. 
           So we can see the range of performance we can get from
           team to team, which is quite useful, for example, for
           Monte Carlo evaluations.
                       DR. WALLIS:  From 10 percent to a hundred
           percent.  In one case it is a huge variation.
                       MR. MUSCARA:  Well, it is a large
           variation, but again we need to look at flaws of a
           depth that might be of concern.  So a 40 percent flaw
           for early detection for the worst team is not very
           good, but a tube can withstand -- a tube with an 80
           percent through flow and 85 percent through flow can
           still withstand a steam line break.
                       DR. WALLIS:  How shall I interpret that
           these points are in relationship to the solid curve
                       MR. MUSCARA:  I'm sorry, but the solid 
           -- these are all different symbols for different
                       DR. WALLIS:  That's right.
                       MR. MUSCARA:  So a curve is a particular
           team, and a given series of points is another team. 
                       DR. WALLIS:  For the solid curve?
                       MR. MUSCARA:  For example, the green curve
                       DR. WALLIS:  Well, it misses all the
           points in there?
                       MR. MUSCARA:  No, the points are just a
           different team.  
                       DR. WALLIS:  That's right.
                       MR. MUSCARA:  This just fit a logistic
           fit, and so the points are only describing not the
           data points, but the team performance.  So the dash
           curve is a particular team, and the green curve is a
           team, and the triangles is another team.
                       DR. WALLIS:  The green curve is a team?
                       MR. MUSCARA:  Yes, and that team performed
           quite well.
                       DR. SHACK:  That is the POD for the best
           team, and the dash line is the POD for the worst team;
           and rather than putting 11 curves where you run out of
           ways to distinguish them, we use symbols for the
           intermediate teams.  And also it confuses you, Graham.
                       MR. MUSCARA:  One thing that is worth
           mentioning is that the worst team was not always the
           worst team.  That is for different flats and different
           locations.  There was no consistency, and the worst
           team is not the worst.
                       DR. WALLIS:  You should use this method
           for the ACRS members on what should go on a letter.
                       DR. POWERS:  But no member is ever wrong. 
           So there is no flaw.
                       DR. WALLIS:  Sometimes the teams -- 
                       DR. POWERS:  Low detection rate.
                       DR. ROSEN:  Are you claiming that one of
           our members is flawless?
                       DR. POWERS:  All of our members are
                       MR. MUSCARA:  This particular view graph
           is not really related to materials issues, but it is
           the task on the item of spiking, and I guess very
           briefly what I want to say is that the staff has
           conducted a review, and it was completed this summer.
                       We plan on developing a staff position on
           this by the end of the year, and then to provide this
           to the public, and to have public comment, and then
           finalize our position with respect to ACRS comments.
                       The last area that I would like to address
           is clearly this is not an internal milestone.  Noticed
           that we finished up in '95 or '96, but work will be
           going on in this area beginning the next calendar
                       And this has to do with getting a better
           understanding of stress corrosion cracking phenomena. 
           So we are interested in finding out better information
           on cracking initiation, and crack growth, and crack
                       A particular interest of ours is to really
           understand crack evolution, because as cracks progress
           from their infant stage, where we have many small
           cracks with ligaments in between, they eventually get
           to a point where the ligament is small, and it no
           longer provides any strength.  And then the cracks
           will join up.
                       The reason that the voltage based criteria
           works right now is because cracks really are in a
           infant stage, and these cracks, although they are many
           cracks, have ligaments, and they exhibit very high
           burst pressures.
                       But we need to understand better when we
           start losing the ligaments, and when we need to use a
           different structural integrity criterion.  So we want
           to understand both the initiation, the evolution as a
           crack changes from small cracks to larger cracks, and
           of course the crack growth rates.
                       This work is really in the planning
           stages, and not a lot of detail is available yet, but
           those are the key features if you want to study them.
                       DR. POWERS:  Is this all focused on the
           600 alloy, or is it also looking at 690?
                       MR. MUSCARA:  Thank you for reminding me. 
           We would like to of course look at 600 because we have
           a lot of field experience with this material, and so
           we understand its behavior somewhat in the lab, but we
           must also understand its behavior in the field.
                       Along with these tests we will be
           conducting 690.  And the idea here is to be able to
           understand the behavior of 690 in the field by
           understanding its laboratory performance, as compared
           to 600.  
                       DR. POWERS:  It seems to me that we really
           need some technical guidance on that.  There are a lot
           of licensees coming in with 690 steam generator tubes,
           and they are saying, gee, scratch our inspection
           intervals because this material is more immune, and
           has more sensitivity maybe is the right word to stress
           corrosion cracking.
                       And it seems to me that we really need a
           technical foundation for deciding what to do there.
                       MR. MUSCARA:  Yes.  One of the things that
           we will be looking at for 690 is that we clearly know
           that the material cracks in the laboratory.  And it
           cracks under conditions which may not be atypical of
           steam generator conditions, because it cracks under
           fairly neutral conditions in impurity environments,
           such as things with copper, sulfate.
                       And so we know the material cracks, and we
           want to be able to bound the conditions under which it
           cracks.  One area of concern for us is the inspection
                       There are two items of concern.  One is
           that we want to stretch -- maybe industry wants to
           stretch the inspection interval, and secondly, we are
           inspecting a small sample.  There is maybe 20 percent.
                       If we stretch the inspection interval, and
           some cracking is going on, and we don't catch it on
           time, and if we use a small inspection sample, again
           we need to have a great deal of degradation in the
           generator before a small sample picks up the problem.
                       So we need to be careful about the length
           of the inspection interval, and the sample size that
           we are using.  Clearly the material behaves better in
           the laboratory than 600.  So it probably has a longer
           useful life.
                       But we don't know that we can make it
           through 40 years.  So it may be reasonable for the
           first inspection cycle to have a longer length, but I
           am not so sure that after a certain amount of time
           that they should not be inspecting the same kind of
           frequency as the materials that we are inspecting now.
                       DR. FORD:  Joe, before you get off that
           one, could you comment on the relationship between
           this task, 3.10, which is more of a quantitative task,
           with that of 3.8, which is looking to see whether
           there is a linear bounding relationship.
                       MR. MUSCARA:  There is a great deal of
           confusion with this topic.  We had a very good write-
           up in the ACRS report, and clearly we agree that
           stress corrosion cracking is not a linear phenomena. 
           We know this.
                       What has turned out to be linear is the
           correlation between the voltage growth rate -- well,
           since voltage does not trap crack size, it cannot
           track cracking rates. So the phenomena is not
           changing.  It is only linear.  The voltage seems to be
                       So we will try and get a better
           understanding but I think the answer is that the
           voltage is not tracking what we are looking at.  It is
           not really tracking crack growth rate.
                       And since there is a lot of scatter in the
           voltage correlation with crack size or burst pressure,
           you can draw almost any correlation through that data,
           and right now we have a linear correlation of time
           with voltage growth rate.
           But that does not mean that is a linear corrosion
           between time and crack growth rate.  
                       DR. WALLIS:  If the end result is to
           predict as a function of time, when you have a near
           tube rupture event, are you saying that any current
           will never meet that criteria? 
                       MR. MUSCARA:  No, what I am saying is that
           the voltage will not meet that criteria.  But we
           presented also last week some work, but in more detail
           last year.
                       We have been developing some techniques in
           the laboratory for accurate sizing of flaws.  I think
           the critical parameters really are the flaw geometry,
           the flaw length and depth.
                       If you can't accurate measure these by any
           current, then you can't accurate predict the burst or
           the failure pressures, or the burst pressures, of the
           integrated tubes.
                       The work that we have done so far has gone
           quite well in predicting the failure of tubes that we
           have tested in the laboratory.
                       By using this advanced sizing technique,
           and then from that data predicting the burst, and we
           run a test, and sure enough we are within 200 psi of
           the burst pressure in many cases.
                       So the key here is not that any current
           can't do this job.  It can, but you have to use the
           right parameters.  And the right parameters in my view
           are the flaw size, and the flaw shape, and not the
           voltage, which does not relate to flaw tightness, or
           length and depth, and so on.
                       DR. WALLIS:  So there is not a big jump in
           application technology?  You are not talking about
           changing the whole NDE industry on its head.
                       MR. MUSCARA:  We in fact are using the
           same probes that industry is using, 10-K probes, and
           what we are doing is data analysis, which is fairly
           different from what the industry is using.
                       We are doing this right now in the
           laboratory, and so it is not a user friendly technique
           at this point.  But there is a lot of interest from
           the industry.  EPRI is interested in this technique,
           and we recently had an e-mail from 
           Westinghouse.  They want to come in and look at the
           technique, and be able to use it.
                       So the technique needs to be improved from
           a human factors point of view to make it easier to
           use, and we would like to make it so that there is not
           too much dependence on the uprater.
                       Right now we have a very smart guy doing
           the evaluations and he uses his knowledge, along with
           what he has programmed to come up with the right
                       If the industry uses it, they we have to
           do a bit more work in making it more user friendly. 
           And it may take some time, but it is not a huge jump
           at this point in the technology.
                       I think at this point that I am finished
           with the remarks that I had planned on making, and
           unless you have questions, we can turn it over to
           Chris Boyd.  
                       DR. POWERS:  Are there any more questions
           on the metallurgical aspects of the problem?  Seeing
           none, we will turn to some aspects of the thermal-
           hydraulics issues, and some results that I think the
           Committee will find interesting on some of the
           progress that research has been making in the area of
           computational fluid dynamics.
                       We have commented several times in our
           research reports that we thought that this was an area
           that the agency could use and would profit, and the
           speaker will give us some idea of the progress that
           they are making.  Thanks, Joe.
                       MR. BOYD:  My name is Chris Boyd and I am
           going to talk to you today about the Division of
           Systems Analysis and Regulatory Effectiveness Programs
           in this area.  And I am going to give just a quick
           overview of the entire division activities, and then
           focus in on some of the CFD work that has been done.
                       This overview was given in more detail
           last week.  So based on recommendations from the ACRS
           subcommittee, looking at the DPO, there were two areas
           that our division is focusing on, and these are in the
           action plan, Items 3.4 and 3.1.
                       Item 3.4 has to do with just developing a
           better understanding of the behavior of the tubes
           during these severe accident conditions.  I am going
           to go into a little bit of that.
                       And then Item 3.1 is evaluating the
           potential for damage due to rapid depressurization,
           such as a main steam line break.  So in Item 3.4,
           looking at the tubes in the severe accident
           conditions, the major components of this research in
           our division are system level code analysis.  It is
           the SCDAP/RELAP work.
                       And that is under way now, and there is a
           report that is just finishing up that is covering a
           lot of sensitivity studies and plant design
           differences, and things along those lines, using the
           workhorse code for the thermal-hydraulics.
                       And then we are looking with computational
           fluid dynamics at the inlet plenum mixing in
           particular, and trying to enhance what we understand
           of that mixing, looking or starting from the test data
           that we have, and then trying to enhance that, and
           that is what I am going to talk about today.
                       And then there is some additional
           assessment of the 1/7th scaled data, and we are
           looking at new experimental data, and possibilities
           for that.  As far as the rapid depressurization goes,
           and its impact on the tubes, this work is scheduled
           for completion at the end of the next calendar year.
                       They are looking at the pressure loads on
           support plates and tubes and flow induced vibrations. 
           This work is just now in the early formulation stages,
           and it was presented last week.  But again this was
           just some preliminary thoughts.
                       Now I am going to focus in on some of the
           work.  This is one of the task items, which was the --
                       DR. POWERS:  Chris, going back to the 3.1
           task, I understand that it is just in the formulation,
           and right now that formulation is focusing on
                       The complaint or the issue that comes up
           in this is that it is a very difficult analysis to do. 
           Most of our codes have never been designed to get
           these kinds of vibrations and dynamic effects.  
                       Are we at a place now where we can start
           talking about what kinds of experimental data would be
           needed to validate these codes.  I understand that it
           is iterative with the kinds of things that the
           previous speaker was discussing on what the magnitude
           of the loads is.  
                       But can we talk about the types of
           experiments, or is that down the road a ways?
                       MR. BOYD:  I think it is down the road a
           little ways.  They are still evaluating what code they
           might use.  So ar far as benchmarking the code if you
           don't have the code yet, and as far as early ideas of
           doing hand calculations --
                       DR. POWERS:  I had a little hope for hand
           calculations in this field.  It's just that it is a
           tough calculation to do without having some
           experimental validation to have any confidence in what
           you got.
                       MR. BOYD:  I would agree.  Most codes fall
           into that category.  
                       DR. POWERS:  Except for chemical codes,
           and that goes without saying that they are all correct
           or all wrong.
                       MR. BOYD:  Well, I will give you a quick
           overview, and I will cover this with the slides.  But
           what we are trying to do is enhance our understanding
           of the inlet plenum mixing.  I am showing here that
           thermal hydraulics reacted to this particular severe
           accident scenario.  
                       This is where the core is uncovered, and
           where it is single-face steam, and the loop seal is
           plugged.  So flow through the hot leg goes through
           part of the tubes and into the outlet plenum, and it
           comes back through the remaining tubes, and mixing in
           the inner-plenum, and this counter-current flow sets
           up in the hot leg.
                       This is modeled with SCDAP/RELAP, a lump
           parameter code.  One of my slides has a noting diagram
           for that.  This areas of interest that I show in the
           SCDAP/RELAP code is essentially three nodes, and they
           nodes have fixed mixing parameters that are set based
           on generally the 1/7th scale experiments that were
           done in a Westinghouse type facility.  
                       So the idea Here is to look at those
           mixing parameters and look at the effect of different
           things on those mixing parameters.  For one with CFD,
           we want to go full-scale, full-pressure.  We want to
           look at the effect of a leaking tube.  
                       We want to look at the effect of different
           inlet geometries, and that is what we are trying to
           accomplish.  The first step will be to benchmark the
           CFD code though to see if it can pick up the right
           behavior, and whether it is a useful tool.  And that
           is what we are going to talk about.
                       But again the background here is that the
           thermal-hydraulic predictions ultimately come from
           SCDAP/RELAP code, ad=nd that is our workhorse code.
                       The tube temperature predictions that come
           out of that are going to be influenced by these fixed
           mixing parameters, and these fixed mixing parameters
           come from a limited set of experimental data.  
                       DR. WALLIS:  You had a picture that you
           just showed of a steam generator with a flow going in
           one direction with some of the tubes, and then the
           other direction and the other tubes?
                       MR. BOYD:  Right.
                       DR. WALLIS:  This sort of situation is
           usually prone to historesis, but it depends on the
           past history which one is going where, and you can't
           just look at it and say 50 percent of the tubes are
           going one way and 50 percent of the tubes are going
           the other.
                       And maybe because of past history, you
           have got something of a 70-30 distribution or
           something.  I think it is not so easy to know how to
           set up the program.
                       MR. BOYD:  We are not setting it up and
           specifying which tubes are in an up and down flow.
                       DR. WALLIS:  Well, then how you set it up
           initially, and then it evolves into something.
                       MR. BOYD:  It evolves into something.  I
           will say that from at least the 1/7th scale that they
           interrupted the entire flow pattern by opening a valve
           at the pressurizer line. 
                       Their experience was that the overall flow
           pattern, and the number of tubes set back into its
           condition fairly quickly after shutting the valve
                       If you can imagine that you have got half
           of them going one way, and the other half going the
           other way, and let's say you want to go to, say, 48
           percent and 51 percent.
                       How do those ones that were going this
           way, how do some of them decide then that I have got
           to reverse?  It is not so obvious how that happens. 
           I would assume that some are just teetering on the
           edge and ready to go either way.
                       MR. MUSCARA:  Well, I would assume that
           some would be obviously teetering on the edge.  The
           assumption would be nearly stagnant given that there
           are up flow and down flow.  
                       DR. WALLIS:   Well, in a continuum like
           that it may be earlier to handle.
                       DR. SHACK:  I remember at the subcommittee
           meeting that you said that you diddled the conditions
           at the core, and you always managed to sort of set up
           a kind of a stable profile, and your counter-current
                       MR. MUSCARA:  That's right.  
                       DR. SHACK:  Did that affect your fractions
           at all?  I mean, when you changed that, did you --
                       MR. BOYD:  No, changing those conditions
           didn't really impact the fractions.  That was a very
           -- it did not impact it significantly.  What happened
           was that there were other parameters to change the
           impact in a much greater sense.
                       So I found that to be a very limited
           impact and that gave us confidence in setting those
           boundary conditions, and that was the point that I was
                       MR. BOYD:  All right.  I talked about the
           background, and the bottom line is that these
           SCDAP/RELAP bins are relying on mixing parameters 
           which come from 1/7th scaled data which we are going
           to try and bolster the confidence in that data.  
                       Why use computational fluids.  Well, it is
           less expensive than experiments.  We can go to full
           scale and full pressure.  We are going to have a
           direct resolution of mixing.  We are not setting fixed
           mixing parameters.
                       And we will then be able to extend our
           data within the MHTGR effects and tube leakage effects
           in a much wider number of variations than we could in
           an experiment.
                       DR. WALLIS:  Well, let's go back to this
           again.  The mixing is dependent upon the flow in the
           tubes, and presumably you have jets coming out of some
           tubes and so on.  So the level of turbulence in the
           lower or left plenum is a function of how the flow is
           coming out of the tubes isn't it?  
                       MR. BOYD:  If I say no to mixed mixing
           parameters, we are not specifying the flow in the
           tube.  We are letting the equations --
                       DR. WALLIS:  But the equations don't model
           many tubes.  They just lump them together.  If you
           limp them together, you get a very different --
                       MR. BOYD:  Well, at 1/7th scale, we have
           got a tube for every tube.  There are only 260 tubes
           here and I am modeling every one of them as an
           individual channel.
                       DR. WALLIS:  And in the real generator,
           you can't do that.  
                       MR. BOYD:  I have my ideas on tube
           modeling if you want to go into that.
                       DR. WALLIS:  Well, at least you realize
           that you have to do it.
                       MR. BOYD:  Just to show a quick flow
           physics comparison.  This is really if people
           understand this,  but on the CF approach the hot leg,
           what I am showing is that we are predicting the direct
           counter-current flow; and in the SCDAP/RELAP
           calculations, you have to set up before the run, and
           run two pipes, and one carries one fixed temperature
           flow in, and the other carries a fixed one-dimensional
           flow back.  
                       In the inlet plenum, in computational
           fluids, we are modeling the rising buoyant plume, and
           letting the turbulent mixing happen, and the lump
           parameter code, we have got these three volumes, with
           fixed flow co-efficients to set up the mixing as you
           see on the three blocks on the right.
                       And then as far as the tubes go, we have
           got the advantage where we are going to directly
           predict the number of tubes in up flow where in the
           SCDAP/RELAP runs that is a fixed parameter again, and
           we had basically one set of tubes all the same
           temperature going up, and one set of tubes, all the
           same temperature, coming back.
                       So we will also be able to get the
           temperature variation, tube to tube variations, which
           could give us some insights.
                       DR. WALLIS:  Again, in CFT, usually you
           have this K esplon model or something for turbulence,
           which was not developed for these conditions, and
           density stratification we know dampens out turbulence.
                       MR. BOYD:  Right.
                       DR. WALLIS:  So you need a different model
           if you are going to do it right.  
                       MR. BOYD:  What I did was that I looked at
           several turbulence models.  I used K-Esplom because it
           is fast for a while, but I didn't want to present that
           here, just because I knew that you guys would pick on
           me if I produced K-Esplon results.
                       But I looked at a few other turbulence
           models, and they didn't make as big an effect as I
                       DR. WALLIS:  Did they take account of the
           Richardson number type thing, the buoyancy and killing
           the turbulence?
                       MR. BOYD:  Yes, there are options for
           that.  The one that I ended up with was a Reynolds
           Stress Model, and so a second order model, modeling
           each of the components.
                       DR. WALLIS:  Was buoyancy in it or it
           doesn't does it?
                       MR. BOYD:  Well, that is implicitly. 
           Buoyancy is implicitly in every one, because I have
           got variable properties and gravities, and all the
           bells and whistles were on.
                       But I was surprised in that it did not
           make as big of a difference as I might have suspected. 
           It did actually look better in some areas, the second
           order of turbulence though.
                       DR. WALLIS:  It certainly looks far better
           than lumped parameters.
                       MR. BOYD:  A little better than lumped
           parameters.  So CFD is going to provide an improved
           understanding at 1/7th scale, and when I say improved
           understanding, we have got data, but we have got
           limited data.
                       There is just a handful of thermal-couples
           no velocity measurements, and mass flows are inferred
           from external energy balances.  So with CFD, you can
           fill in some of the gaps, and you can take a look at
           the errors that you might or the uncertainty that you
           might get by just measuring with four thermal-couples.
                       And assuming that you have measured enough
           in the hot leg to understand the full profile, and
           things along those lines.
                       DR. WALLIS:  It is not a predictive tool
           then, and you just use it to understand data?
                       MR. BOYD:  Well, in this case, I am saying
           one of our action items was to assess the 1/7th scaled
           data.  So this is a tool that helps us assess that.  
                       At this point though we are not really
           interested in this 1/7th scaled data so much as we are
           the full scale data.  And at this point, I am showing
           results against 1/7th.  This was our first step.
                       DR. WALLIS:  And you eventually want to
           predict full scale?
                       MR. BOYD:  That's right, and we are
           working on that now and starting to build the models
           for full scale.  Then extending the full scale, the
           first question --
                       DR. WALLIS:  Full scale means predicting
           full scale without experiments?
                       MR. BOYD:  That's right.  We will be
           making predictions at full scale, that's right, down
           to the third decimal place.
                       Does scale affect the mixing parameters,
           and that is our first question.  And at full scale,
           that is where I am going to look at the effect of tube
           leakage, and the effect of inlet geometry variations,
           as opposed to doing them at the small scale, where we
           are not really interested.  
                       And then we can look at tube to tube
           variations.  The schedule and the approach validate
           the technique to see if it is a valid approach, and
           with 1/7th scaled data we have done that.
                       Extend the predictions to full scale, and
           that is starting up now, and then complete these
           additional studies, and that is next July.  So we will
           take a quick look at what we did at full scale.
                       We have got two measurements at full
           scale.  This is the course mesh and the other mesh is
           actually still running several million cells.  This is
           about a million cells for a hot leg and steam
           generator.  They are about 5 centimeters a piece.
                       And cutting that down to a 2 centimeter
           cell case, which is what is running now, makes the
           mesh obviously a lot tighter, and a lot more
           cumbersome.  But that gives you an idea of what the 3-
           D mesh of each of the tubes being modeled.
                       I look at the results in two ways,
           qualitatively and quantitatively.  Qualitatively, they
           gave a handful of observations from the test, and
           things such as the flow coming in to 60 percent of the
           hot leg, and exiting the hot leg covering about 25
           percent of the hot leg area, and sloping interface, of
                       This was picked up in the test.  The plume
           or the rate of drop off of temperature in the plume
           roughly matched what was predicted.  The temperature
           dropped through the tubes.  Again, similarly matched
           all the counter current flows.  
                       So on a qualitative basis, I am just
           saying that we picked up the global flow phenomena
           that was observed and could be talked about in that
           test series.
                       Quantitatively, when we go down to the
           parameters we are interested in to put into
           SCDAP/RELAP, this is one of the tests that we ran. 
           This is actually the worst set of results.  We do have
           a little bit better, but these aren't that bad.
                       Generally, I would say they are within 10
           percent on most of the parameters.  We have
           overpredicted in this case a number of hot tubes, the
           number of tubes in upflow by approximately 10 percent
           of the tube sheet.  
                       That is probably one of the larger errors,
           and that is something that I am looking at with
           sensitivity studies on the tube model.  As far as
           things like mixing fraction and recirculation ratio,
           which are direct parameters that we care about int he
           SCDAP/RELAP runs, we generally are within 10 percent.
                       And in this particular case, there is a
           model in the recirculation ratios that is as high as
           15 percent off.  Given the data and the limited
           measurements that were made, I would say that we are
           within the uncertainty of the data on this. 
                       So in general I am saying that the code
           has done a decent job.  We are getting the big
           picture, and I think it is going to be a useful tool. 
                       And when I told you that we were about 10
           percent of the tube sheet off in the upflow, this is
           a direct picture of that.  The outside dotted line is
           the fluent prediction of the boundary between up flow
           tubes and down flow tubes, the inner two lines are the
           boundary based on the data.  
                       Now, that is a band because they didn't
           have every tube monitored.  So somewhere within that
           band, is where the region of upflow and down flow
                       They reported the outer band, but I put in
           the inner band because that was just as likely in my
                       DR. WALLIS:  Westinghouse gets fewer --
                       MR. BOYD:  That's right.  So the results
           of the validation, generally I am saying that we are
           within 10 percent of the Westinghouse 1/7th scale.  We
           have picked up the global flow parameters that we
                       And I think given the uncertainty in the
           experimental data, we are doing very well here.  And
           work on full-scale predictions is under way.  And I
           think I am repeating myself here.
                       So I am saying that the CFD technique has
           been demonstrated to be applicable for the prediction
           of these mixing parameters, and for this kind of
           counter-current flow situation. 
                       This work provides a level of confidence
           that CFD can be used to go beyond the experimental
           data to conditions not explicitly covered, such as a
           little variation in the inlet conditions or a
           variation in the height of the hot leg relative to be
           the tube sheet.
                       And further analysis as planned that full
           scale, with tube leakage, and these geometry effects,
           and other sensitivity studies.
                       DR. POWERS:  It is just an exciting
           progress and I look forward to what comes out of it. 
           It is a new level of understanding of what is going on
           in these flow calculations, and it would be delightful
           to have those variations that you are talking about,
           because that has been the subject of endless amounts
           of speculation and hand-waving, and it would be nice
           to have some reliable calculational results in that
                       DR. WALLIS:  You said there was a run
           running now?  I just wondered if it will be over
           before we leave on Saturday.
                       DR. KRESS:  Actually, it won't.
                       DR. POWERS:  That was the right answer;
           whether it was going to be done or not.  All right. 
           Any other questions on the thermal-hydraulic aspects
           of the action plan?
                       It is my impression that the staff has
           bent over backwards to respond to our recommendations,
           and it is my impression that we have helped the staff
           in acquainting the Commission with the fact that they
           need to fund research in these areas if they want the
           level of understanding that they would like to have.
                       And I see us producing an improvement in
           the state of the art in many areas, and certainly in
           the metallurgical areas, and then from this I see in
           the computational fluid dynamics areas.  
                       So I think that truthfully this has been
           win-win situation in producing this review.  Thank you
           very much.  I will now turn the meeting back over to
           you, Mr. Chairman.
                       CHAIRMAN APOSTOLAKIS:  With that, we will
           take our break, and meet again at 3:20.
                       (Whereupon, the meeting was recessed at
           3:05 p.m., and was resumed at 3:20 p.m.)
                       CHAIRMAN APOSTOLAKIS:  The last
           presentation of the day is on Proposed Resolution of
           Generic Safety Issue 173-A, Spent Fuel Storage Pool
           for Operating Facilities, and Dr. Kress, you are up
                       DR. KRESS:  I was looking through David's
           slides, and he goes into the background pretty well,
           and so there is no need for me to make the background
           statements that I was going to make.  I will just let
           him make them.  So I will turn it over to him, and let
           him go ahead.
                       MR. DIEC:  I appreciate that, Dr. Kress. 
           Good afternoon.  My name is David Diec, and with me
           today is Steve Jones from the Office of NRR.  We also
           have the technical staff who are sitting in the
           background and who are available to answer any
           questions that you may have.
                       For today's presentation, I will be
           discussing the purpose of the presentation itself, and
           go over a little bit of background of what GSI-173A is
                       And the staff evaluation of plant specific
           issues.  Steve Jones will then discuss with you the
           basis for the closure of this GSI and make a final
                       The purpose of the presentation today is
           two-fold.  We are addressing the recommendation that
           you made in the June 20th letter, and certainly we are
           seeking for your closure letter on this issue, as it
           has been a long time since we last talked to you.
                       The information that is being discussed
           today has been presented to you so many times in the
           past.  We came before you to discuss about our action,
           task action plan earlier, as early as 1994, and to
           present our findings in 1996, and to as recently as
           last year, to discuss about our proposed resolution
           for a plant specific issues.
                       In the June 20th letter, the Committee
           raised a concern whether the screening criteria that
           we used were appropriate for potential plant specific
           evaluations for spent fuel action and its risk at
           operating facilities.
                       The impetus of the concern was that the
           criteria in the Reg Guide was derived from prompt
           fatalities at facilities, and it is probably
           appropriate for an operating reactor source because it
           was driven by a steam oxidation condition.
                       However, for the spent fuel pool accident,
           and you may be looking at the source term is different
           and involved with a large amount of releases of
           Ruthenium and fuel fines.  
                       As a result of that, the Committee made
           the recommendation that we defer closing out this GSI
           until the technical study that we conduct on
           decommissioning plants is complete, and consider
           developing appropriate screening criteria for
           regulatory analysis of the spent fuel pool accidents
           at other facilities.
                       In way of background, this GSI was a
           genesis of the report filed under Part 21 in 1992 by
           two contractor engineers who performed work at the
           Susquehanna plants.
                       These engineers contended that the
           Susquehanna spent fuel pool failed to meet regulatory
           requirements with respect to sustained loss of pool
           cooling function after the loss of off-site power or
           a loss of LOCA event.
                       And they sustained that boiling could
           cause failure of equipment necessary to mitigate
           accidents, and to safely shut down the plants.  That
           was the genesis of that.  
                       In 1993, we formulated a task action plan
           to resolve issues associated with the spent fuel pool
           storage, and to ensure the reliability of the decay
           heat removal capability, and maintenance of the
           inventory in the pool.
                       The task action plan was completed in
           1996, and we briefed you of our results, and at that
           time after the completion of the briefing, the
           Committee asked us whether or not we would like
           anything; i.e., a response letter.
                       In hindsight, we should have said yes. 
           But it seemed unnecessary at that time, and so that
           leads us to today's presentation.  The task action
           plan looked at three generic areas; coolant inventory,
           and the ability to provide and maintain inventory in
           the pool; and to detect temperature and fuel
           reactivity; and the ability to maintain fuel in the
           sub-critical and the bar flex integrity in the spent
           fuel racks.
                       Just a note on the fuel reactivity.  We
           addressed this issue separately as part of the generic
           letter in the 96-04 response.  So it was not
           considered in this broader scope.  
                       In doing the implementation of the action
           plan, we visited a number of plants, and we reviewed
           plant specific design features that addressed these
           two areas, the coolant inventory and coolant
           temperature, and also the reactivity issue a little
                       And we concluded that these plants
           conformed to the current regulations.  However, we
           identified a number of plant specific issues that need
           further regulatory evaluation; and in June of last
           year, we came before you to discuss specifically how
           we would resolve those.  
                       I am going to go over the probabilistic
           assessment that we used at that time.  We performed
           the probabilistic assessment of these issues by first
           conducting a screening analysis, using plant specific
           design and operational information.  
                       And two endstates were chosen to test the
           design features under the evaluation for inventory
           endstate corresponding to a loss of coolant to within
           a one foot level above the top of the spent fuel pool
           rack was used.
                       For issues involving boiling, an endstate
           corresponding to a sustained boiling in a pool for
           greater than 8 hours was used.  The endstates
           represent conservative points in the sequence, where
           public health and safety was assured.  
                       DR. BONACA:  If I could ask a question and
           if you could go back a moment to that, and you are
           talking about consistent with regulatory guidelines,
           and it seems as if there is one set of requirements to
           which all these power plants are adhering to.
                       And in the license renewal, we have seen
           a lot of different requirements, especially for older
           plants, that seem to have more or less regulatory
           requirements imposed on the equipment.  
                       So the question that I am asking here is
           this implied that it is just one set of requirements
           and applying to all pools, such that you can perform
           a generic PRA screening analysis?
                       MR. DIEC:  We look at the number of plants
           and we choose a specific group of plants that
           represent specific plant issues, using this criteria. 
           So I am not sure it is a blanket approach in this
                       DR. BONACA:  Well, let me give you an
           example.  We have some plants where we were told that
           probably none of the cooling equipment in the  spent
           fuel pool is in their design basis.  
                       Therefore, they only commit to maintaining
           the liner of the pool and the emergency injection and
           both of them are self-degrade and they are in the
           scope of the license renewal.  
                       And we were left with some surprises on
           that.  We are reviewing now an application where the
           cooling system is in the scope of license renewal, and
           therefore the heat exchanger and pumps, et cetera, is
           in the scope.
                       So we have a sense that there is a very
           different regulatory requirements applying to
           different plants, and that's why I was asking these
           questions about this generic analysis.
                       MR. JONES:  That in essence was the
           genesis of this issue.  Most of the design features
           that we evaluated were called for in later design
           guidance, but we are not implemented at a lot of the
           earlier plants because their construction permits
           predated that guidance.
                       Things such as -- well, like safety
           grades, spent fuel pool cooling system, and seismic
           makeup lines, and things of that nature.  So the
           purpose of the evaluation was to determine if we were
           justified in imposing backfill requirements to upgrade
           those systems.
                       DR. BONACA:  So actually what I am raising
           here is it was the center of this issue, and you are
           going to talk about that.
                       MR. DIEC:  After performing the analysis,
           we concluded that if we can see the loss of the spent
           fuel coolant events were less than 1E minus 6 per
           year, and there was no regulatory action justified for
           these plants, group of plants.
                       The frequency of suspended boiling was
           found between 1E minus 6 per reactor year, to 1E minus
           5 per reactor year.  We conducted a further evaluation
           of those plants and concluded that no action was
                       The evaluation that we looked at took into
           consideration the licensee's voluntary actions to
           modify their plant piping system designs to install
           additional low level alarm in the pool, and a switch
           that will give an indication in either the control
           room or at the local station.
                       And also beefing up their operating
           procedures to make sure that the operator is aware of
           the onset of the loss of cooling events.
                       DR. BONACA:  So the first bullet is
           applicable to all power plants?
                       MR. DIEC:  All power plants that fall into
           the loss of cooling events.
                       DR. BONACA:  And that includes the spent
           fuel pool coolant event in their licensing basis.  I
           am trying to understand what that means.
                       MR. JONES:  These were essentially
           screening analyses of certain plants that had
           vulnerabilities to loss of coolant events because of
           the way their spent fuel pools were configured or the
           reliability of their makeup systems.
                       And in the second case there were
           vulnerabilities with the spent fuel pool cooling
           system.  Like it did not have an on-site source of
           power available to the pumps and heat exchanges.
                       DR. BONACA:  So the conclusion for the
           first question was that in no case -- I mean, the
           frequency of loss of spent fuel pool coolant was 1E
           minus 6 for all plants?
                       DR. KRESS:  I interpreted that to mean
           that these individual plants would make a judgment,
           and if their frequency was that, then no action was
           required.  If it wasn't, then you would have to go
           further with it.
                       DR. BONACA:  So this was the conclusion.
           All right.
                       MR. JONES:  We made an effort to select
           the most vulnerable plants and evaluate them on a
           plant specific basis the probability of these two
           events or two endstates.  
                       And it was a bounding assessment for all
           the plants that had some of the design features that
           we were evaluating.    
                       DR. ROSEN:  And a definition of the
           endstate is within one foot above the top of the rack?
                       MR. DIEC:  Correct.
                       DR. ROSEN:  And this was based on an
           analysis of operational experience?
                       MR. DIEC:  Yes.
                       DR. ROSEN:  You are saying that the
           frequency has been less than 1E to the minus 6 based
           on operating experience?
                       DR. KRESS:  No, it was calculated --
                       MR. LEE:  This is Sam Lee.  I was the risk
           analyst that worked on this, and Dr. Bonaca, you are
           correct.  It is per plant frequency estimation, and
           this is all a calculated number based on operations,
           per se.
                       DR. BONACA:  Thank you.
                       MR. LEE:  Well, it is based on operations
           as is, but it is all based on risk analysis, or what
           I would call a probablistic analysis, because the
           endstate that we had used was one foot above the
           stored fuel.
                       DR. WALLIS:  You have to have millions of
           years of experience, and it has got to be calculated. 
                       MR. HUBBARD:  This is George Hubbard with
           the plant systems branch, and I just wanted to clarify
           one thing.  This was the risk analysis that was done
           by the staff and by the contractor through site
                       They went out and they looked at the
           issues, and we performed the screening analysis that
           we are talking about here.  It was not a licensee, per
           se.  It was that we got a contractor and went out and
           did the work ourselves.
                       DR. ROSEN:  What does the operating
           experience tell you?  We have had a hundred plants
           running for 20 or 30 years, but we have never had one
           of those obviously.
                       MR. JONES:  Right.  None of these
           endstates has been experienced in the industry to
           date.  There have been long term loss of coolant
           events, on the order of 24 hours, or more, but those
           were at times when the heat load in the spent fuel
           pool was such that -- well, loss of coolant events
           have been relatively limited.
                       We did look at issues such as what
           occurred at Connecticut Yankee, and also we considered
           the freezing event at Dresden, which was resulted in
           Bulletin 94-01.  
                       And although it didn't directly involve a
           spent fuel coolant system, it was identified at that
           time that there was a vulnerability to a rupture in
           the spent fuel coolant transfer line that could have
           drained the spent fuel pool at Dresden Unit 1.  But to
           answer your question though --
                       DR. ROSEN:  That no operating experience
           would contradict this conclusion.
                       MR. JONES:  Right.
                       MR. HUBBARD:  This is George Hubbard again
           from Plant Systems.  Right in this same time period,
           AEOD did a study that looked at operating experiences
           for temperatures and of the height or the level of the
           water level, and the water level dropped.
                       I was just glancing through here as you
           were talking, and it looks like there were a few in
           which the duration of the loss of coolant was like
           three in greater than 24 hours, in which the loss of
           coolant lasted for longer than 24 hours.
                       As far as the temperature increase, there
           was one time where it got to 50 degrees, and this was
           looking at our operating experience, and when we were
           doing this, we were aware of this data as this report
           was in early '97, and we completed the plant specific
                       And a report to the Commission went up in
           September of '97.  So the operating experience was
           available to us, and I have not found the exact
           probabilities that they used from the AEOD experience.
                       But that was taken into account, the
           operating experience, and your comment that the
           operating experience doesn't contradict this is true.
                       DR. KRESS:  Let me ask you about your two
           screening goals.  It basically implies that if you
           meet these goals that you would meet the Commission's
           safety goals, and there is an order of magnitude of
           difference between these two, and the second one still
           meets the safety goals because during that time period
           you have operator action that could mitigate it so
           that you could get another factor of 10 out of that.
                       MR. JONES:  Right.
                       DR. KRESS:  Is that a correct
                       MR. JONES:  Yes.
                       MR. DIEC:  We take into consideration a
           voluntary action as well and operator actions in this
                       MR. JONES:  These were essentially
           selected as more easily modeled endstates.
                       DR. KRESS:  Oh, yes.  If you go any
           further than that, then you have lots of physics.  And
           if you don't meet these, there is no reason to go
                       MR. JONES:  And also the difficulty in
           assessing the probabilities of recovery when the time
           frames get out to an order of a day or more.
                       DR. BONACA:  So here the criteria is 8
           hours?  So as long as you can recover before 8 hours
           of boiling that's a success?
                       MR. JONES:  Right.  If it is extended
           beyond 8 hours, then it is a questionable recovery.
                       MR. LEE:  This is Sam Lee again.  If I may
           add, the reason behind estimating the frequency of
           sustained blowing, if you remember back in the early
           '90s with the Susquehanna situation, where a boiling
           pool could affect the ECCS of the other units.
                       And that was the basis for why we
           conducted this analysis.  After we did the analysis,
           or when we went to the plant as George said during the
           analysis, we found or discovered the physical layout
           of the plant was such that it was not like
                       That even if you had sustained boiling,
           that the steam environment would not impact the ECCS
           of the other units.  So it really became a non-issue
           for us at that point.
                       CHAIRMAN APOSTOLAKIS:  Do you remember
           what the dominant contributors to these were?  Were
           they seismic events?
                       MR. LEE:  Yes.  A seismic event is one of
           the major contributors, yes.
                       DR. ROSEN:  When we talked about
           decommissioning plants, we talked about loss of spent
           fuel pool coolant events, and we were told at that
           time that the two most likely sequences to get there
           were seismic and sabotage.
                       MR. LEE:  I will talk about one particular
           plant that we have data for, and the loss of inventory
           -- and this is through a break in the pipe -- was one
           of the dominant contributions, and the other one is
           the earthquake.
                       CHAIRMAN APOSTOLAKIS:  Okay.  Why don't we
           go on.
                       MR. DIEC:  Well, at this time, I am going
           to turn it over to Steve Jones, who will discuss the
           basis for closure.
                       MR. JONES:  As you are aware the staff
           completed a study of the events of the decommissioning
           of plants, and that study established a pool
           performance guideline regarding the frequency of
           events leading to a potential fire in the spent fuel
           pool or really fuel uncovery at 1 times 7 to the minus
           5 for reactor year.
                       Using a source term that included
           consideration of large releases of Ruthenian and fuel
           fines, the staff evaluated consequences for a pool
           with approximately 30 days of decay from the most
           recent discharge.
                       That study demonstrated that the
           quantitative health objectives were met for then
           frequencies below the plant performance guideline,
           both in terms of prompt fatalities and latent cancer
                       Since the screening criteria that were
           used in the plant specific studies were more
           conservative than the pool performance guideline of
           the decommissioning study, we considered that that
           would demonstrate that the quantitative health
           objectives were met for all the plant specific issues
           that were evaluated.
                       DR. KRESS:  Let me ask you a simple
           question about that.  The previous study with the
           NUREG 17-38 was dealing with decommissioning plants
           that didn't have a reactor there.
                       MR. JONES:  That's correct.
                       DR. KRESS:  So only the risk associated
           with the suppression pool had to be met in order to
           meet the safety goals.  Now you are talking about a
           subset of sequences at an operating plant.
                       And it is not appropriate to say that the
           subset has to meet the safety goals, because safety
           goals have to be met by the pool summation of all the
                       So when you say it is an order of
           magnitude less than this screening criteria, I
           consider that appropriate, an appropriate choice.  It
           is not overly conservative.  It is an appropriate
           choice for a subset of sequences.
                       So I would not want to see you go up to 10
           to the minus 5, for example, and say we will use that,
           because this is for an operating reactor, and you have
           to keep it down so that it adds in to the other risks. 
           That was just an observation and a comment.
                       MR. JONES:  I understand your point.  We
           concluded that additional screening criteria were not
           necessary and that as Dr. Kress mentioned the absolute
           frequency values were roughly on the order of a
           magnitude lower.
                       And in addition the endstates were
           substantially more conservative, and the pool
           performance guidelines looked at a complete loss of
           inventory in the fuel pool, and our endstates were
           stopped at either sustained boiling or loss of a
           significant inventory, but still the fuel being
           covered.  That concludes our briefing.
                       DR. KRESS:  Are there any comments or
           questions that the Committee has?  Seeing or hearing
           none, I think you made your case clear, and we will
           have a letter on the subject.  And you brought us back
           on schedule, and thank you for the presentation.  It
           was short and sweet and to the point, and we
           appreciate it.
                       CHAIRMAN APOSTOLAKIS:  All right.  Thank
                       (Whereupon, the meeting was recessed at
           3:50 p.m.)

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