492nd Meeting - May 2, 2002
Official Transcript of Proceedings
NUCLEAR REGULATORY COMMISSION
Title: Advisory Committee on Reactor Safeguards
492nd Meeting: OPEN SESSION
Docket Number: (not applicable)
Location: Rockville, Maryland
Date: Thursday, May 2, 2002
Work Order No.: NRC-356 Pages 1-48/60-226
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
NUCLEAR REGULATORY COMMISSION
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ADVISORY COMMITTEE ON REACTOR SAFEGUARDS (ACRS)
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THURSDAY, MAY 2, 2002
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The ACRS met at the Nuclear Regulatory
Commission, Two White Flint North, Room T2B3, 11545
Rockville Pike, at 8:30 a.m., George E. Apostolakis,
GEORGE E. APOSTOLAKIS Chairman
MARIO V. BONACA Vice Chairman
F. PETER FORD Member
THOMAS S. KRESS Member-at-Large
GRAHAM M. LEITCH Member
DANA A. POWERS Member
VICTOR H. RANSOM Member
STEPHEN L. ROSEN Member
WILLIAM J. SHACK Member
JOHN D. SIEBER Member
GRAHAM B. WALLIS Member ACRS STAFF PRESENT:
JOHN T. LARKINS Executive Director, ACRS/ACNW
Designated Government Official
SHER BAHADUR Associate Director, ACRS/ACNW
HOWARD J. LARSON Special Assistant, ACRS/ACNW
SAM DURAISWAMY Technical Assistant, ACRS/ACNW
PAUL A. BOEHNERT
ZENA ABDULLAHI NRR
TONY ATTARD NRR
GOUTAM BAGELI NRR
S. SINGH BAYWA NRR
HERB BERKOW NRR
TAMMY BLOOMER NRR
RALPH CARUSO NRR
ED CONNECE NRR
RICHARD ECKENRODE NRR
RAJ GORJ NRR
JOHN GOSHEN NRR
DONNIE HARRISON NRR
GARY HOLAHAN NRR
T.W. C. HUG NRR
EDWARD D. KENDRICK NRR
RALPH LANDRY NRR
ALSO PRESENT: (Cont'd)
RICHARD LOBEL NRR
KAMAL MANOLY NRR
L.B. (TAD) MARSH NRR
RALPH MEYER NRR
BRENDA MOZAFARI NRR
YURI ORECHWA NRR
K. PARCZEWSKI NRR
ANNE PASSARELLI NRR
ROBERT PETTUS NRR
J.H. RAVAL NRR
THOMAS SCARBROUGH NRR
HERALD SCOTT NRR
MOHAMMED SHUMBI NRR
DAVID TERAD NRR
D. THATCHER NRR
N.K. TREHAN NRR
S.D. WEERAKKODY NRR
ERIC WEISS NRR
JARED WERMIEL NRR
JIM WIGGINTON NRR
ALAN LEVIN OCM/RAM
FAROUK ELTAWILA RES
JOCELYN MITCHELL RES
JASON SCHAPEROW RES
ALSO PRESENT: (Cont'd)
CHARLES TINKLER RES
LEONARD R. BELLER Progress Energy, CP&L
TOM DRESSER Progress Energy, CP&L
PAUL FLADOS Progress Energy, CP&L
C.J. GANNON Progress Energy, CP&L
MARK GRANTHAM Progress Energy, CP&L
ROBERT KITCHEN Progress Energy, CP&L
MARK A. TURKAL Progress Energy, CP&L
MICHAEL S. WILLIAMS Progress Energy, CP&L
BLANE WILTON Progress Energy, CP&L
FRAN BULGER GE Nuclear Energy
CARL HINDS GE Nuclear Energy
DAN PAPPONE GE Nuclear Energy
JASON POST GE Nuclear Energy
GEORGE STRAMBACK GE Nuclear Energy
CHARLES BRINKMAN Westinghouse Electric Company
WILLIAM SLAGLE Westinghouse Electric Company
PETER HASTINGS DCS
LAWRENCE LEE ERIN Engineering
JAMES F. MALLAY Framatome ANP
JOE MIHALCIK Constellation Energy Group/EPRI
Opening Remarks by the ACRS Chairman 6
Brunswick Steam Electric Plant, Units 1 & 2
Core Power Uprate
By Carolina Power & Light Company
Graham B. Wallis 8
Robert Kitchen 8, 77
Tom Dresser 36
Blane Wilton 60
Mark Grantham 64
Dan Pappone 68
By NRC Staff
Tad Marsh 84
Brenda Mozafari 90
Ralph Caruso 91
Zena Abdullahi 103
Expert Panel Recommendations on Source Term
for High Burnup and Mixed Oxide Fuel
Jason Schaperow 123
Confirmatory Research on High Burnup Fuel
Ralph Caruso 155
Ralph Meyer 212 P-R-O-C-E-E-D-I-N-G-S
CHAIRMAN APOSTOLAKIS: The meeting will
now come to order. This is the first day of the 492nd
meeting of the Advisory Committee on Reactor
Safeguards. In today's meeting, the Committee will
consider the following: Brunswick Steam Electric
Plant, Units 1 and 2 Core Power Uprate, Expert Panel
Recommendations on Source Term for High Burnup and
Mixed Oxide Fuel, Confirmatory Research Program on
High Burnup Fuel, Subcommittee Report regarding MOX
Fuel Fabrication Facility, Safeguards and Security
Activities, Proposed ACRS Reports.
A portion of the meeting will be closed to
discuss General Electric proprietary information
applicable to the Brunswick Plant core power uprate.
the entire session on safeguards and security
activities will be closed to protect national security
information and safeguards information. This session
will be held in T8E8.
This meeting is being conducted in
accordance with the provisions of the Federal Advisory
Committee Act. Dr. John Larkins is a designated
federal official for the initial portion of the
meeting. 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, identify themselves and speak
with sufficient clarity and volume so that they can be
I have a short announcement before we
start. Mr. Jit Singh, stand up, please. He's leaving
us. He'll be joining the Office of Nuclear Regulatory
Research as a Senior Reliability and Risk Analysis
Engineer in the Division of Risk Analysis and
Applications, and this will be effective May 6, which
is next Monday.
As we all know, Jit has provided very
valuable service to this Committee for seven years,
about seven years, especially in the area of fire
protection. And there will be a farewell luncheon in
the Subcommittee Room tomorrow at lunchtime. That's
when usually luncheons are held. And we are all
invited. That's my understanding. Is that correct,
Jit? Okay. We wish you well.
Okay. The first item on the agenda is the
Brunswick core power uprate, and Professor Wallis is
the cognizant member. Please.
MR. WALLIS: Good morning.
CHAIRMAN APOSTOLAKIS: Good morning.
MR. WALLIS: This is a power uprate of a
BWR to roughly 20 percent above its original power
level. It's very much like what we've seen before
with Duane Arnold, Dresden and Clinton, and I think it
needs no more introduction from me.
MR. KITCHEN: Good morning.
MR. FORD: Excuse me. I'd like to declare
a conflict of interest being a GE retiree.
MR. RANSOM: And I have to declare a
conflict of interest because I still haven't sold my
GE stock, but I'll get rid of it shortly.
MR. WALLIS: I'll give you ten bucks a
MR. KITCHEN: Good morning. My name is
Bob Kitchen. I'm the Project Manager for the power
uprate at the Brunswick Station. I'd like to take a
few minutes and just talk to you about the project in
total and a few items for the overview, also to give
you a reference of where Brunswick is today relative
to where we're trying to go.
Currently, we -- we previously had done a
stretch uprate, which is a five percent increase in
power above the original licensed power level. So we
currently operate at 105 percent relative to original
power. We're also a two-year operating cycle, 24
months, which I think we are the first licensee for
the ACRS review that is a two-year fuel cycle. Our
increase is actually to raise power to 120 percent
above licensed power level, which represents a 15
percent power rise above our current power level.
The implementation of uprate at Brunswick
will be very similar to those you've seen before, with
a two-step uprate. The first being about 112 to 115
percent, and then the second being up t 120 percent.
These are some parameters that you can
look at to see the change in power. Currently, we're
2558 and going to 2923. You can see the steam flow,
and feed flow, of course, would increase
proportionately to that. Also, the reactor pressure
change we had previously done for the five percent
uprate, increasing it up to 1045, there is no pressure
increase associated with this uprate, which you've
seen simplifies the analysis somewhat.
We have several modifications very similar
to previous uprates in terms of the type of
modifications that we're doing. We only have two that
are safety related modifications. The first which was
of interest is our Standby Liquid Control, our SLC
System. We are increasing the boron concentration to
support cold shutdown. We are making a modification
to implement that. That's going to be done actually
with the second fuel load of GE14. We have to change
our fuel type to support the two-year fuel cycle from
GE13 to GE14. Along with the higher energy, the
significant power increase, we're going to be changing
our boron concentration in SLC.
MR. SIEBER: Is it necessary that you make
that modification, that change, to accommodate this
core? Or are you doing it just to gain greater
control and ease of operation?
MR. KITCHEN: The change is necessary.
The degree of the change is somewhat -- there is some
flexibility there. We need to achieve a 720 ppm boron
concentration in-vessel. Currently, the requirement
is 660. And we could do that in several ways. We are
going to do that in such a way to support, as we'll
show later, right now we require a two-pump SLC
operation to achieve shutdown. The way we're doing
this modification will enable us to reach success
criteria with one pump. So we have to do a
modification, but the type of modification or the
degree that we're doing it there's some flexibility.
MR. SIEBER: On the other hand, you could
just increase the concentration and continue to use
two pumps, and you would still be safe, right?
MR. KITCHEN: Yes, sir.
MR. LEITCH: This modification occurs --
is necessary to support what we'll call Phase 2, that
is, the ultimate uprate power, or is it necessary to
support Phase 1?
MR. KITCHEN: Actually, it's required for
the second load of GE14 fuel. And the reason I
distinguish with that is that we actually loaded GE14
on Unit 2 at our previous refueling. So our first
uprate outage on Unit 2 will be our second load of
GE14. So really the requirement is tied to the fuel
loading as opposed to the uprate stages that we're
planning to do directly. We have a commitment, which
I'm sure the Committee has seen, we've made a
commitment to the Commission to make that change and
also to make the change in such a manner that one pump
will support success criteria for SLC.
MR. LEITCH: You have committed to do
MR. KITCHEN: Yes, sir. Since the ACRS
Subcommittee, we have provided a commitment to the
MR. LEITCH: Thank you.
MR. KITCHEN: The other safety related
modification relates to our electrical buses. Our
emergency buses are powered from off-site through our
MR. LEITCH: Just before we leave this,
I'd like it if we could --
MR. KITCHEN: Yes, sir.
MR. LEITCH: Is there another modification
associated with the relief valves on the SLC pumps?
Is that part of what you're speaking -- in other
words, does what you say just refer to the boron
concentration or is the same timing and all involved
with the relief valve modification?
MR. KITCHEN: The relief valve
modification is not tied to -- not really an uprate
requirement. It is tied to an issue with under ATWS
conditions where depending on how quickly you inject
you can result in relief valve lifting. Mark, I can't
remember if that's --
MR. GRANTHAM: This is Mark Grantham,
Carolina Power & Light. We are planning to replace
the relief valves with a higher lift pressure that
will gain us 50 psig in relief valve margin. That is
currently planned for the next Unit 2 outage and the
following Unit 1 outage. There is no formal
commitment for that, but right now that is planned
MR. LEITCH: Very good. I understand.
MR. KITCHEN: The second safety related
modification that we show here is tied to our
electrical load supply. As I mentioned, the emergency
buses are powered from off-site through our balance-
of-plant buses, and with the higher loads that we are
putting on our balance-of-plant buses to support
uprate, larger pumps and motors, et cetera, that are
required, there's a bit more of a challenge on our
voltage support for degraded grid voltage reset; in
other words, to be able to maintain the off-site power
support to the emergency bus, which is obviously
To support that, we're putting in what we
call a Unit Trip Load Shed. This is a tiered support.
We can select certain standby balance and plant loads,
for example, a standby condensate pump, standby
condensate booster pump, to trip or not to start --
excuse me, their standby to not autostart in the event
we have a unit trip. So that prevents large loads on
balance-of-plant from starting and further lowering
the voltage. This modification involves a select
switch which is key-locked on the individual loads
that are selected to not start in the event of a unit
trip. And it will ensure that we maintain required
voltage to the E buses under unit trip conditions from
MR. LEITCH: That autostart defeat does
not interfere with the normal autostart on, say, loss
of low suction pressure or something like that. In
other words, if you lost a condensate pump but didn't
trip the unit, you'd still be able to start the other
MR. KITCHEN: That's correct. It does not
affect autostart under normal conditions.
MR. LEITCH: It's only after the unit has
MR. KITCHEN: Yes, sir.
MR. LEITCH: -- that this comes into play.
MR. KITCHEN: That's correct.
MR. LEITCH: Thanks.
MR. ROSEN: In reading the staff's safety
evaluation on this uprate, it was not clear to me
whether or not this Unit Trip Load Shed would be
required if you were not making an uprate. Can you
help me with that?
MR. KITCHEN: That's correct. The uprate
raises horsepower requirements on the load supply by
balance-of-plant buses. And that's the reason for the
MR. ROSEN: The only reason. There were
no grid reasons to not -- if Brunswick was not making
this uprate that you wouldn't go ahead with these
changes anyway, changes to the switchyard and other
changes to help with grid stability in the region?
MR. KITCHEN: Not for the Unit Trip Load
Shed. Now the grid stability, yes, and that's the
second -- that's a balance-of-plant modification.
MR. ROSEN: Well, maybe you could help me
when you get to that to --
MR. KITCHEN: Sure.
MR. ROSEN: -- clarify that.
MR. KITCHEN: This would not be tied to
the grid situation; this is tied to uprate.
MR. ROSEN: Okay.
MR. KITCHEN: balance-of-plant, as I
mentioned, we're going to be doing the uprate in two
phases. There are a number of balance-of-plant
modifications. I think the Committee will see these
are very similar in type to the others that we've
looked at -- turbine replacements. One that we've
asked about was the power system stabilizer and out-
of-step protection, and that is related to grid. It
is related to uprate, it is also tied to grid loads in
And there are a couple of -- I'm sure
there are many -- factors that lead to instability
situations. One is tied to the unit load itself. The
larger the R load, the more susceptible we are to grid
instability. Also the larger load in our area, the
more susceptible the grid instability. So even with
that uprate, we could have conditions which might make
us want to make these modifications to ensure
stability. But the driver for these is really the
The power system stabilizer is basically
a feedback loop on our excitation to stabilize any
oscillations on the generator. The out-of-step
protection is just that. If we end up with an out-of-
phase situation or leading to an out-of-phase, we'll
trip the generator rather than end up tripping off-
site breakers to ensure not only generator protection,
which in this case is really secondary, but really to
ensure that we don't have a cascading grid failure.
MR. POWERS: Why wouldn't it be prudent to
go ahead and make these changes to the grid stability,
allow that to sort itself out for a while and then go
the power uprate?
MR. KITCHEN: Well, in effect, we are
doing that. We've already made these changes on Unit
1. The power system stabilizer and out-of-step is
already installed on Unit 1, and testing was conducted
in association with the startup. Of course, we have
not uprated. We plan to do that shortly after this
meeting. But we have done testing at current power
levels with these modifications.
MR. POWERS: Then why not allow things to
operate for a cycle, two cycles?
MR. KITCHEN: It's already -- I mean these
types of modifications are not unique to the uprate.
They're fairly common in the industry. The testing
that we perform demonstrates the -- clearly
demonstrates the performance of the system. And if we
had a problem with the system, we could maintain
current power levels or simply remove them from
service if required. So there really wouldn't be any
benefit in delaying the uprate implementation one
cycle and test it.
The Phase 2 modifications at the plant are
really not quite as extensive, although they are major
modifications to the main transformers, other
additional feedwater heaters and moisture separator
reheaters. And both of those are tied to uprate
because of not only performance but also to support
As you well know, the uprate leads to
degraded margins. We'll talk about those quite a bit
in our presentation today. But I wanted to point out
also there are some things that we're doing that will
either regain or maintain margins in the operational
area. Just to give you for examples, we've talked
about the standby liquid control modification, and
we're doing a little more than you would say you have
to to maintain our margin on SLC. We're going to go
from the current two-pump to a one-pump requirement
for operability there. That's definitely an
We also are changing our Power Range
Instrumentation System, and that does a couple of
things for us. Currently, we operate on thermal-
hydraulic instability solution E1A, which is a prevent
solution. With the new powering system, we're going
to option three, which provides detect and suppress,
a SCRAM, based on instability and detection, which we
see as an enhancement, particularly for the operator
interface. It's a little better digital controls
interface, as well as reducing maintenance
requirements, less surveillance is required, the
system eliminates half SCRAM. So there are some
benefits there with this modification.
Also, I think you may have seen some
uprates where condensate, condensate booster pumps all
were required to operate to support uprate. We
elected to improve the system to maintain our standby
pump capability. We didn't want to give that up with
And, finally, we've talked about the power
system stabilizer, but that will, as was pointed out,
not only because of uprate but also because of grid
growth would be a mod that would be desirable to
The Subcommittee asked about the interim
operation, because with the two-step implementation we
would get the license for reactor power operation up
to 120 percent and then be plant-limited by balance-
of-plant equipment. And the question was how do you
control this in the interim? There are a couple of
aspects of that.
One, during the startup and the power
ascension for implementation of the uprate, we are
going to do testing, as you've seen before, response
testing on our controls for the turbine and response
of the digital feed controls, as well as performance
monitoring on balance-of-plant equipment. And we'll
be looking at where we have predictions based on our
analyses on the system, where we expect parameters to
go. But we'll be looking closely at the actual plant
performance to assess that we're not limited in some
criteria before we expect it.
We'll translate that procedurally to an
operational guidance as far as plant control, because
you want the operators to be able to operate the plant
on something they're looking at in the control room as
opposed to a BOP limit in the plant, although that's
what will really limit it. And the way I look at
this, it's really not different today than if I were
to have a component out-of-service in the plant, like
a condenser water box, for example, which would limit
us in reactor power. It's really the same type of
operational control that we would have.
So these are the plans we have for our
transition, just to basically test, monitor and then
MR. LEITCH: You referred to turbine
testing. Could you say a word more about exactly what
kind of turbine testing you plan to do?
MR. KITCHEN: Well, during the startup, of
course, we did the routine vibration and over-speed
checks, but the testing I'm specifically talking about
are controls tests. We do pressure regulator fail-
over. We have backup and primary controls that
pressure regulators will fail the primary over. We'll
do step changes in pressure to verify the valve
response is correct. And we'll also monitor the
system response, it's called incremental regulation,
to make sure that the valve position response is as
you would expect based on the power increase.
MR. LEITCH: Now, will the EH -- I'm just
a little confused -- is the EHC system going to be
modified prior to Phase 1 or prior to Phase 2?
MR. KITCHEN: It's part of the mod
requirements for Phase 1 and --
MR. LEITCH: Phase 1.
MR. KITCHEN: -- it's part of the --
really, it's tied in with the high pressure turbine
modification. Specifically, we operate in partial
ARC, 3-ARC control today, and we'll be going to 2-ARC
control, partial ARC with uprate.
MR. POWERS: Do I understand correctly
you're going to train the operators from what they do
now to what you do at an interim, and you're going to
untrain them on that and train them for what you'll do
at the final power up?
MR. KITCHEN: We started training
operators actually last year on the modifications that
are being installed. In fact, the modifications that
are installed in the Unit have been installed in the
simulator, and the operators have trained on the
equipment itself. We're training this phase, which
started this week, on the actual uprate -- the license
change, the technical specification changes and the
allowed operation. So, really, operationally, the
only change is the modifications and then the licensed
power. They will train on transients associated with
MR. POWERS: So right now we have a
situation where the operators have a plant that they
run with one set of limits and are training on a
different set of limits?
MR. KITCHEN: They are -- well, we always
train on the current plant operation. The operators
are training on what the limits will be in terms of
power operation with uprate approval. Now, the
parameters that control like our average power range
monitor trips, main steam line flow set points, those
will only change one time. They will change with the
uprate, and they will be that way for both stages. So
really it's a lower power level training up to full
MR. ROSEN: Before you get too far away
from it, let me ask, have you something in your
presentation this morning, some more insight that you
can offer us on the power range instrumentation
changes? Of is what you said about it all that you
plan to say?
MR. KITCHEN: That's all I planned to say.
We could talk through that more if you like. The
system that we're installing is the General Electric
NUMAC System. It's a digital system that installs not
only with the change in the instrumentation itself,
but it also provides a change in our instability
solution protection. We call it Operate E1A which has
areas that the operators avoid and areas where there
would be an automatic SCRAM, just based on where you
are located in the power operation region.
With Option 3, the stability solution is
tied to what's called period-based algorithm which
looks for certain frequencies which are representative
of thermal-hydraulic instability and has a threshold
based on the number of cycles counted and the
amplitude of those cycles. If it meets those
criteria, there's an automatic SCRAM. So regardless
of where you are operating, if the system sees an
instability, there would be an automatic SCRAM.
MR. SHACK: I thought there was a problem
with actually implementing Option 3 at the moment
because of a Part 21 --
MR. KITCHEN: There is an industry issue
with the Option 3 stability solution. There is a Part
21. Under certain circumstances, the generic curve
that is used to determine the set points for the
operating cycle can be non-conservative. And along
with that Part 21, the GE resolution or the GE interim
guidance provided where there are certain calculations
the fuel folks can do to determine if, for our
specific operating cycle, if that curve bounds our set
points; in other words, if they are conservative.
For Unit 1, which we've installed Option
3 on, those calculations have been performed and prove
that the curve bounds Brunswick Unit 1, that the
systems installed are operable on Unit 1 today and
will be operable through the cycle. So Part 21 still
applies, but for our specific application it's not
MR. POWERS: How many cycles do you have
to go through before the system actuates?
MR. KITCHEN: Don't know the answer to
that. Jason, the question is how many cycles of
instability before a trip?
MR. POST: Yes. This is Jason Post of GE.
It has to establish a base period within a criteria
which takes a half a cycle and then every half cycle
after that it adds one count. So you have to -- it
will take you about five and a half or six cycles to
reach a count of ten or 11 counts. And then it also
has to reach an amplitude set point. So, typically,
1.1 peak over average, and then the SCRAM will occur.
So it could be, with a two-second period, we're
talking around -- I think around ten seconds or so.
MR. ROSEN: How do you test that in the
MR. KITCHEN: Actually, the system has
some self-test features in the digital system. We
actually tested similar to what we would do other
systems. We can remove a channel from service and
perform the set point verifications for the trips,
also check the sensitivity of the system for a
response to instability and the thresholds.
Basically, it's not unlike any other system that we
would test. It does have an advantage in that
currently if we remove a channel for testing, we have
to put in a half SCRAM. And with the new system, the
logic is set up such that we can take one channel, one
APRM channel out of service and not have a half SCRAM.
So it's a pretty significant advantage. It reduces
significantly the number of half SCRAMS that we have
for routine testing.
MR. ROSEN: Well, you've described
checking the set points and those sort of things, but
do you actually check the oscillatory counting
procedure algorithm in the software?
MR. KITCHEN: There's one. Jason, go
ahead, address that.
MR. POST: Yes. This is Jason Post with
GE. There's various parameters in there that cause
the -- even with normal noise and the REM variation in
the neutron flux signal, you will get periodic counts
from your system. So there are some tuning
parameters, and we make sure that the system is tuned
adequately to give an adequate level of response for
normal noise. It's a procedure we use to confirm
system operation for an actual instability that
occurred at Liebstadt. So we ensure that the system
is adequately responsive during normal operations so
we've ensured that when an actual instability does
occur, we will get the counts.
MR. POWERS: I think what you said is that
there is no test for this system, this Plant.
MR. POST: It's continuously being tested.
You notice the -- as I said, during normal operation,
there is some level of counts. In fact, one of the
original surprises when we put the system in was we
got more counts than expected. It was being very
responsive during normal noise, and you could get
single channels that would give you five, six, seven
counts just from normal noise and the random nature of
that. So it is -- you know continuously that it is
MR. POWERS: Do you understand that,
MR. ROSEN: Only marginally, Dr. Powers.
MR. POWERS: It seems to me that when you
find you've got a noisy channel and you suppress the
noise, you also suppress its ability to respond under
MR. ROSEN: Well, that comes down to the
operating procedure. If they are suppressing noise
that way, you're right. If you get five or six or
seven counts during normal operations just because of
random variations of the signal and you need ten or 11
to trip the plant, I would suspect the operators are
starting to get a little nervous.
MR. KITCHEN: But the tuning procedure
that Jason is talking about is really set to verify
that we have appropriate response so that the operator
has enough time to take action if there's an
instability. But the system will still provide
protection, and also not so low that we have -- you
don't want a lot of nuisance alarms associated with
the system. So that's the band that you tune it
within, but there's not a situation where you tune it
to a point where you eliminate protection from the
instability of that.
MR. LEITCH: It actually takes two
parameters for the system to actuate. You know, it
can be counting forever, but if the signal's not --
the variations are not big enough, it won't make a
MR. KITCHEN: That's correct.
MR. LEITCH: So when you look at noise all
you're doing is seeing whether it counts or not.
MR. POST: Just to reinforce that point,
that's exactly one of the concerns with the Part 21
issue is that if we lower the amplitude set point too
far, you'll come too close to where a normal noise
event could cause an unnecessary SCRAM.
MR. KITCHEN: The power uprate for
Brunswick is -- we do have a few exceptions to the
ELTR. Generally, the guidance in the ELTR was
complied with totally. There a few exceptions. Three
of these are related to the constant pressure nature
of this uprate and some of the simplifications which
are warranted. We feel that these can be discussed
later in proprietary section. These as well as the
fourth one I've identified up there, which is large
transient exception, are similar to what have been
presented before with other uprates. Basically, the
large transient testing is associated with the MSIV
closure and generator load reject, and we would like
to waive both of those tests.
MR. ROSEN: Some of the other plants that
have come before us have included a re-circ runback
feature. I don't see that in your proposal.
MR. KITCHEN: The ones that I'm familiar
with, sir, are associated with the condensate system
itself in that they need to run all the condensate
pumps to support operation. In that situation, if you
have a pump trip, you need to reduce power to
basically the original power level, and they do that
with a re-circ runback. In our case, with a standby
pump, the standby pump would start, and there's no
need for runback.
MR. ROSEN: Right. And I was waiting for
you to make a further comment on large transient
MR. KITCHEN: Certainly can.
MR. ROSEN: There have been a number of
questions raised about the need for that testing by
members of the staff and also by this Committee. And
there are currently considerations in the staff of
setting up some criteria for when large transient
testing might be required. Are you aware of those
MR. KITCHEN: I'm aware there's been quite
a bit of discussion about the large transient testing.
I'm not familiar with the specific Committee
MR. ROSEN: Well, the staff established a
panel to look into the need for integrated testing for
extended power uprates. And that Panel has concluded
its report, which sets up --
MR. MARSH: Mr. Rosen, we may into an area
which is not publicly released yet, okay? This is the
area of the Panel and how the Panel looked at it. So
can I ask you to forebear till we get into a --
MR. ROSEN: Oh, I see. Is the staff going
to address some of this?
MR. MARSH: To some extent.
MR. ROSEN: And the implications of that
to the Brunswick --
MR. MARSH: We're going to discuss with
you what our plans are regarding that Panel and what
its recommendations are and how we're going to
MR. ROSEN: Well, it seems to me that
there's a question here as to whether or not the
outcome of all of that will be applied to Brunswick.
MR. MARSH: Let's see, what can I say? We
are going to consider the extent to which the decision
in the guidance that will be made should be back-fit
to this Plant or to any plant that's already gone
through this process.
MR. KRESS: Will that require back-fit --
MR. MARSH: It involve looking backwards
into the back-fit type of procedure, that's right.
MR. ROSEN: So that would be clearly true
for plants whose license uprate has been approved.
MR. MARSH: Yes, sir.
MR. ROSEN: For Brunswick, which is not
quite there yet, would it apply to them?
MR. MARSH: Yes, it would.
MR. ROSEN: In other words, as a back-fit
to them or --
MR. MARSH: Yes, it would.
MR. ROSEN: -- or in their case, as part
of their approval, should they be -- should this
request be approved? Do you see the difference I'm
MR. MARSH: We recommend we continue on
the same track that we've been on, because the
guidance isn't yet developed nor has the back-fit
analysis been done. So we recommend continuing along
the track that we've been on, which is to approve --
grant a request to waive those tests. Staff will
develop guidance, will apply back-fit analysis to that
guidance to find out whether this Plant and others
should do the large transient testing. Have I
answered your question?
MR. ROSEN: Not exactly, because it would
seem to me that plants to which you have to apply the
back-fit rule, 5109, I assume --
MR. MARSH: Right.
MR. ROSEN: -- would have a higher
threshold in terms of whatever the criteria turn out
to be than a plant which was licensed for uprate with
the understanding that when the tests criteria were
determined that they would be applied to Brunswick.
And depending on whether they fell within the criteria
or not, they would either be applied to them or not.
MR. MARSH: Right. Well, we haven't yet
decided whether large transient testing should be
done, okay? That is still part of the charge that
we're being given by the Office Director. And once
the decision is made, then a guidance is developed as
to whether it should or should not be done. Then
we'll apply the back-fit to it. So we would be
premature to condition this license or in any way use
that criteria beyond what the staff's acceptance
criteria is now.
MR. KRESS: In order to apply the back-fit
regulatory analysis, you have to determine the risk
REMS that you offset by this.
MR. MARSH: Sure.
MR. KRESS: How in the world can you ever
do that for something like large transient testing?
MR. MARSH: That's just one of the tests
that's embodied in the 109. There are other tests
that are there.
MR. KRESS: I know, but if it fails -- I
mean you have to pass that test too.
MR. MARSH: Sure. Sure.
MR. KRESS: And I just don't see how you
can actually do that.
MR. MARSH: We'll have to develop -- we'll
have to study it in detail, which is what the charge
is all about, and develop regulatory guidance and
decide whether or not it should be done, and then
that's a forward-looking issue. And then in terms of
backward-looking, we'll have to apply the 109 test to
find out whether it should be done, whether the gain
is worth the cost in terms of REM, in terms of safety
margins and if it comes to be an adequate protection
issue, if that's where it is. But that is the charge.
MR. ROSEN: It seems like we're working on
a very short fuse here, from my reading of the
information, which I now understand is not released
yet. But that all of this is very near-term stuff.
MR. MARSH: Our charge from -- I was going
to do this at the beginning, but I'll be glad to do it
now. The Office Director has asked us to develop a
plan to give back to him by the end of this month with
how we will formulate the staff guidance and the
extent to which we'll apply the back-fit. We'll be
glad to, of course, brief the Committee on that and
how we do that. We haven't yet set the time frame
when we will do that, but it's thought to be this
year. This is a this year type of an effort. So it's
a short-term effort.
MR. KRESS: Have you already decided this
is not a compliance issue and therefore is a back-fit?
MR. MARSH: It's premature to say that.
I think we have to hold out on that. We have to think
about that. My impression is that it would not be
since we are, at this point, saying this licensee is
in conformance with the regulations, go forth without
testing. So unless some other regulatory requirement
emerges when you look at the back-fit analysis, if you
judge that they're not in compliance with the
regulation, then you'd be in the compliance exception,
but we'd have to study that in more detail. I don't
MR. KITCHEN: Can we move on?
MR. SIEBER: Yes.
MR. KITCHEN: There are a few unique
aspects of Brunswick uprate I just wanted to point out
to the ACRS. First, we do have, as we talked about,
some actions that we're implementing to enhance grid
stability. Secondly, we are, I think, the first plant
you've reviewed that's hydrogen water chemistry versus
normal metal chem.
Finally, we have significant energy
requirements to support our operating cycle. We are
asking for 120 percent power operation relative to our
original license, and we are a two-year fuel cycle.
We also operate at 97 percent capacity factor. That's
our design criteria, and we've done quite well at
Brunswick. So those things combined give a pretty
significant energy load for the cycle. And those
impact, of course, our fuel design.
With that, we talked about fuel. So, Tom?
MR. DRESSER: Good morning. My name is
Tom Dresser. I work for CP&L's BWR Fuel Engineering
Group, and I'm going to discuss very quickly five
different topics related to the reactor core. The
first two, the fuel bundle and the core design and the
ATWS, are performed completely consistent with the
previous mils and with the generic methodology of ELTR
1 and 2. The last three, the transient analysis,
thermal-hydraulic stability and LOCA analysis, each
take some kind of exception to the generic
methodology, which I'll discuss when we get there.
And those last three topics do contain material in my
presentation, which is proprietary to GE, so we'll
pause from the second and third topic and go to closed
The fuel bundle and core design that is
performed in support of the power uprate itself to
provide the input to all the fuel-related tasks is
done for a full equilibrium cycle. And the design
targets to be achieved by that equilibrium cycle are
similar to what's been seen by the ACRS for other
plants. As Bob mentioned, Brunswick is a higher
energy cycle because of the 24-month refueling outage
and the excellent operations.
That forces us to do a number of physical
changes to achieve the energy requirements. The first
is that we need to change our fuel design from GE13 to
the ten by ten GE14 fuel design. Now, amongst many
other attributes, the GE14 is a heavier bundle with
about five percent more uranium in each bundle loaded.
Additionally, we have to increase the enrichment on
the order of four-tenths weight percent in that new
fuel, and we have to increase the number of new fuel
bundles substantially. The reload pressure goes from
about 39 percent to about 47 percent to achieve this
extra 15 percent power.
Now, by making all three of those changes,
we do get the required energy for the two-year
refueling cycle, but it does make for a more reactive
core. So by the time we get to the full equilibrium
cycle, we do need to make the Standby Liquid Control
System boron equivalent change.
MR. ROSEN: What did you say about
enrichment, would you repeat that?
MR. DRESSER: Yes. The enrichment must be
increased. Of course, it's -- I can't give you one
single number to cover everything, but the range of
the enrichment increase is on the order of 0.4 weight
MR. ROSEN: The increase is 0.4.
MR. DRESSER: The increase is 0.4. It
goes from the highest sub-batch. The fuel goes from
about 4.0 to about 4.4 weight percent.
MR. ROSEN: Okay. Now I understand.
MR. DRESSER: And as Bob mentioned, we
will need to make a change to the effective boron
concentration of about ten percent, to go from about
660 ppm to about 720 ppm by equilibrium.
The last change that we need to make is
pretty trivial. The tech specs power at which we
start monitoring thermal limits decreases from 25
percent to 23 percent, but that is just to maintain
the same absolute bundle power calculational basis as
used generically for GE BWRs in the fleet.
MR. SIEBER: It seems to me that the per
rod duty is going up substantially in this fuel. And
if you look at GE13, that's like spaghetti, and GE14
is like vermicelli.
MR. SIEBER: From the standpoint of
bending and --
MR. DRESSER: That's true. The bending
moment in that kind of thing is going to be smaller
for the GE14. The linear heat generations is a lot
less for the GE14, and the limit goes down and the
actual amount of linear heat generations goes down
even more. One thing that going with these very large
reload fractions it's not possible to design the fuel
cores with the same fuel efficiency that we've been
used to in the past. And so the average exposure on
the fuel goes down a lot. So whereas our batch
average exposure limits are 50,000 megawatt days per
ton and we had been able to design our lead sub-
batches and bundles to go up to the 48 or even
sometimes over 49 megawatt days per ton, with this new
core design, our lead bundle burnups are in the range
of 45, 45.5. So it's a whole lot less exposure on the
fuel, and that should improve the --
MR. SIEBER: On the other hand, you're
going to have maybe six percent of the bundles that
will be in core for three cycles?
MR. DRESSER: That's correct. And that --
MR. SIEBER: What is the peak bundle
MR. DRESSER: Those are the bundles that
contribute to that 45.5. There are also bundles which
are substantially less exposure. So the high bundles
are in the range of 45.5. And that's because a lot of
these bundles spend time near the outside of the core
where the flux is less.
MR. SIEBER: Thank you.
MR. POWERS: Tom, you just recently
experienced the fuel leak, I believe. Was that in
MR. DRESSER: Yes. We did have two GE14
fuels that have leaked. We've removed those from --
this is the Unit 2 Plant. Those have been -- the
Plant was shut down and those bundles were removed.
They'll be tested. We'll go examine those bundles in
about two months to --
MR. POWERS: Okay. So you don't yet know
the nature of that --
MR. DRESSER: That's correct.
VICE CHAIRMAN BONACA: Did you shadow
those failed pins?
MR. DRESSER: Yes, we did. They failed
nearly a year ago, and we did power suppression
testing and then suppressed those bundles. It was
fairly effective in controlling the degradation of the
fuel. And the bundles were located in a vicinity that
had been identified.
VICE CHAIRMAN BONACA: So you must have
lost quite a bit of cycle length.
MR. DRESSER: Well, because this -- we
shut down the Plant in the middle of a cycle, and so
we will lose, I think, on the order of a week, not too
VICE CHAIRMAN BONACA: You shut it down?
MR. DRESSER: We did shut it down and we
threw those out and we've started the Unit.
The first actual power uprate cycle is in
Unit 1, Cycle 14. I'm going to go through this
relatively quickly. The design goals are similar.
They were all met. It required a slightly smaller
relay fraction to achieve the energy, about 46 instead
of 47 percent of the core. Otherwise it's not that
different from the equilibrium cycle.
One big difference is that there is, as
Bob mentioned, no need to modify the Standby Liquid
Control System boron concentration for the cycle
because of the single reloaded GE14 fuel. One thing
that's interesting about both this and equilibrium
design with those large batch fractions is that the
power -- the radio power distribution is very, very
flat for Brunswick, and that will affect many things
that we look at today. One of the things it affects
right here in this cycle is the safety limit MCPR must
be increased from 1.10 to 1.12.
MR. ROSEN: Do you have some way of
characterizing this very flat versus what it was
MR. DRESSER: Yes. I have a couple -- I
have a visual which I'm going to share with you.
I'm going to respond to this in two ways.
I'm going to show you a visual first and then give you
some numbers. This is an open session. I think is
probably not proprietary. This is last cycle. This
is a radio power distribution for the bundle peak
powers. The blue is the highest power density, 1.2 to
1.4, and peach is 1.0 to 1.2. And then as we go
progressively further out along the radius of the
core, the power densities get less and less. That's
basically what the non-power uprate cycle looks like.
Now, if we go to the current cycle, the
first power uprate, we see some migration of power
towards the outside and a little bit lower power
density towards the interior of the core. And then if
we look at the full equilibrium cycle, it's more
Now, to put some numbers on that, the
highest sub-batch power fraction for Cycle 14 is about
1.22. By equilibrium, it goes down to about 1.19.
And in comparison, I think that the last plant that
came before the ACRS and showed a flat power
distribution that corresponding number was about 1.26.
So this is the flattest power distribution that has
MR. ROSEN: You know, visually, if you put
-- somehow maybe you could show the first and the last
one on the same -- the blue is the high power regions,
am I correct?
MR. DRESSER: That's correct. That's the
MR. ROSEN: Okay. So if you just look at
-- do some sort of mental integration of that --
MR. DRESSER: To me, the numbers might be
a little bit easier to understand, the 1.26, 1.22,
1.19. I can look at this and see visually that the
equilibrium is lighter, it's not as dark as the
MR. ROSEN: I believe you.
MR. WALLIS: Did you average in the --
MR. SIEBER: That's a first.
MR. WALLIS: You're pushing the power up
towards the edge, you can see that. The edge is the
MR. DRESSER: That's correct.
MR. WALLIS: That's the clearest thing you
see from that visual integration.
MR. ROSEN: The edges, is that what you
were looking at?
MR. WALLIS: Yes. Power towards the side
MR. DRESSER: Would you like to see those
MR. ROSEN: Yes. Would you go back to
MR. WALLIS: I'm just trying to help you
with your integration.
MR. ROSEN: I was looking at the blue.
MR. WALLIS: Yes, but the blue is
misleading. Look at the edges. You find those
skinny, it's a yellow region. So that the low power
regions are lower.
MR. ROSEN: Yes. Now I see that.
MR. WALLIS: Of lower extent.
MR. ROSEN: Okay. Thank you.
MR. DRESSER: To conclude for the fuel
design itself, it's necessary to make some physical
changes to the plant and load much more fuel and make
a change to the Standby Liquid Control System. But in
order to maintain the types of design margins that we
typically expect, it does not require any change to
our methodology or expectations.
The second topic would be ATWS. This
analysis was done consistent with the ELTR as well so
that the four limiting ATWS events were analyzed. The
one that's of greatest interest is going to be the
pressure regulatory failure open event, which shows a
peak vessel bottom pressure increasing to about 13
pounds less than the ASME service level C limit.
Licensing-wise, I guess that's 12 pounds and change
more than it has to be in terms of margin. But it
appears pretty close. What offers comfort in that
amount of margin here is that this analysis is done
not with normal transient, best estimate kind of
inputs, but the estimates are conservative. The set
points and things are biased to be towards the worst
allowable value limits. Also, the SRV capacities,
which would be very important to this, are only 90
percent of the actual capacities. And this analysis
does assume one SRV is out of service as well.
Then the final thing is that these
calculated results are using GE's ODYN code. If we
had recalculated these using GE's more sophisticated
and accurate TRAC-G code, that, by itself, would
produce well over 100 pounds additional margin. So
though the numbers appear fairly close to the design
limit, there really is no concern with respect to
actual safety here.
MR. WALLIS: So you know what track it
would predict without actually running it?
MR. DRESSER: Well, G's got a lot of
experience with TRAC, so that's just a rule of thumb
kind of number. It produces much lower results.
In the interest of time, I'll just comment
that the other three analyses show a great deal of
margin to be respective limits, and unless we have
particular questions about that, I'll --
MR. ROSEN: Well, only that the peak clad
temperature goes down. Would you want to comment on
MR. DRESSER: Yes. The peak clad
temperature goes down. There are a couple other
facts, but probably the most important thing for the
ATWS is that with power uprate we have a higher void
fraction and a much more bottom-peaked flux
distribution so the peak node is lower in the core
where there is more water and less void in the power
uprate case, and you get a better heat transfer out.
These results, in general, for the ATWS
show that the ATWS analysis for Brunswick is done
consistent with the standard generic methodology, and
there is no requirement to support the ATWS now. It's
just to make changes to the Standby Liquid Control
System boron concentration. There's no need to make
changes to the actions that the operators take, and
the standard designs are satisfied.
Next, we're going to want to go to the
final three topics, and we'll need to go to closed
MR. BOEHNERT: All right. If we can have
anyone from the public please leave the room. It will
be, I don't know, a short time. There's not too many
slides. I will come out if there's anyone here.
Okay. Well, let's proceed to closed
session then. And, Transcriber, if you'll go to a
closed session transcript, please. Thank you.
(Whereupon, the proceedings went into
MR. WILTON: Good morning. My name is
Blane Wilton, and I'm the Supervisor of Reactor
Systems at Brunswick Nuclear Station. I'd like to
discuss the reactor vessel and internals,
specifically, the effects and impacts of power uprate
as it relates to the internals.
What we found is the reactor vessel and
all the internals were addressed in accordance with
ELTR. The impacts that we found were our PT curves,
our pressure temperature curves, were impacted. Our
current curves that we're operating on are good
through March of 2003, have been approved with the
effects of power uprate included. We have a
commitment to resubmit PT curves to the staff for
review by June of 2002 with the new fluency
methodology, in accordance with Reg. Guide 1.190
Fluency was also affected by power uprate.
What we saw is that fluency did not increase
proportionally with the power increase. There was a
greater than a 20 percent increase. The reason for
that is just the core configuration going to an
equilibrium core, pushing the power farther out to the
periphery of the core, increased the fluency that we
Embrittlement. Embrittlement was
affected. We're an older Plant, so we don't have full
SHARPIE test data on our vessel materials. Ten CFR 50
Appendix G requires that you meet certain criteria for
both initial plate materials as well as end-of-life
materials. If you don't have full materials, you can
do what's called an equivalent margins analysis. We
redid that for our Plant, found that we met all
requirements. We also did a plant-specific one on our
N16 nozzles because those are in close proximity to
the beltline region, and they met all limits also.
So, therefore, embrittlement was okay.
Fatigue. Fatigue is also affected. We
did a fatigue evaluation on our limiting components,
and what we found is that all fatigue values are met
through end-of-life plus 20 years. We looked at the
20 years just to make sure, because we are looking
down the road at life extension. But we met it for
end-of-life, plus we met it for end-of-life plus 20
years on all of our components.
MR. SHACK: Just in your --
MR. WILTON: Sure.
MR. SHACK: You're in a normal hydrogen
water chemistry, so are you continuously monitoring
ECP somewhere in the vessel?
MR. WILTON: We do not have ECP monitoring
installed. We don't have ECP probes. What we do is
we have run models of plant-specific models of our
Plant; we've done that. We also monitor parameters
like main steam line rad monitors, radiation --
MR. SHACK: So you monitor N16.
MR. WILTON: Yes.
MR. SHACK: Do you monitor oxygen coming
MR. WILTON: We don't monitor oxygen, but
we monitor hydrogen concentration in our feedwater.
MR. SHACK: Have you run the radiolysis
model with the higher fluency?
MR. WILTON: Yes, we have. And what we've
found is that our protection -- host power uprate is
actually better, at least as good or better with the
high fluency, because the radiolysis model is affected
by fluency. The higher the fluency, the more
efficient the recombination reaction is. And,
therefore, what you see is that your protection
actually goes slightly more negative. And when we saw
that, we questioned that, and we went back through
EPRI and had them validate our model for us. And what
we saw is that we actually had at least as good or
better protection under power uprate conditions than
we currently have.
MR. SHACK: Now, in your feedwater lines,
because you have hydrogen water chemistry, do you have
any more difficulty in maintaining a reasonable oxygen
level in the feedwater?
MR. WILTON: We haven't seen that, no.
MR. SHACK: What do you maintain, 20 ppb?
MR. WILTON: Yes, 20 ppb oxygen in our
feedwater lines. And we inject at 39 and a half SCFM,
which equates to about 1.0 to 1.05 ppm in our -- so we
are a moderate hydrogen water chemistry plant. And
our plan is to continue maintaining hydrogen at our
current levels. Now, how we validate that is we have
an extensive inspection program. So we're following
the guidelines of the VIP, we maintain our water
chemistry in accordance with the VIP guidelines, and
our model shows what our ECP levels are, our
inspections, then validate that. What we've seen,
we're not -- where we do have cracking we're not
seeing crack growth, which is what our models show --
say that we should have. So our inspection program is
really a validation of what our models and all show
us. And we've committed -- you know, we will continue
to do our inspection program through end-of-life.
MR. FORD: Just a curiosity question. Do
you inject oxygen into the condensate?
MR. WILTON: Yes, we do.
MR. WALLIS: May I ask a question for
MR. WILTON: Certainly.
MR. WALLIS: Are you a noble chem?
MR. WILTON: No, we are not a noble chem
MR. WALLIS: Do you plan to be?
MR. WILTON: No. At this point we do not.
MR. ROSEN: You say you inject oxygen. Do
you really do that or do you -- are you injecting air
with oxygen in it?
MR. WILTON: It's air.
MR. ROSEN: It's air.
MR. WILTON: Yes, I'm sorry. Any
MR. GRANTHAM: Good morning. I'm Mark
Grantham. I'm the Design Superintendent on our Power
Uprate Team. I'll be talking about our containment
analysis that was performed and the impact of that
analysis on MPSH for ECCS pumps.
The containment analysis was performed in
accordance with the ELTR. For data comparison
purposes, what we have is actually the first data
column, and all these columns are 102 percent of
reactor thermal power. The first column provides
actually our current UFSAR values. We re-ran the
analysis at 102 percent of our current licensed
thermal power using the same assumptions that were
used in our power uprate analysis. And what this does
it provides a direct comparison for the uprate to
provide basically the overall impact to the
containment analysis strictly from the power increase.
Reviewing the data, drywell pressure under
EPU conditions goes up to 46.4 psig. The acceptance
limit is 62. Drywell space temperature 293 degrees F
versus an acceptance limit of 340. Wetwell pressure,
31.1 psig versus an acceptance limit of 62.
Suppression pool temperature, 207.7 degrees F versus
an acceptance limit of 220. So we still maintain a
substantial margin under uprate compared to the
VICE CHAIRMAN BONACA: What's the
difference in methods between the FSAR and the
MR. GRANTHAM: There's four main
differences. The FSAR analysis was performed using
the homogeneous equilibrium model for determining
VICE CHAIRMAN BONACA: Okay.
MR. GRANTHAM: The power uprate model used
Moody slip critical flow model.
VICE CHAIRMAN BONACA: Okay.
MR. GRANTHAM: The original FSAR analysis
used nominal decay heat values, whereas the power
uprate analysis applied a two sigma uncertainty adder
to those values.
VICE CHAIRMAN BONACA: Okay. Thank you.
MR. SIEBER: This is, Mark, one
MR. GRANTHAM: That's correct. The impact
of that on net positive suction head -- currently,
Brunswick is a Safety Guide 1 plant which currently
does not allow credit for containment overpressure.
As a result of the power uprate and in accordance with
the allowances of the ELTR, we will, after the uprate,
require credit for containment overpressure.
We actually looked at a short-term and
long-term MPSH requirements. Short term is for the
first ten minutes when operator action is not
credited, and the pumps are assumed to be at run-out
conditions. Under the first ten minutes, there is no
credit for overpressure required. After ten minutes,
the flows on RHR and course-rate pumps are assumed to
be throttled back in accordance with the approved
operating procedures. For the long-term analysis, the
peak required overpressure is 3.1 psig. The actual
available overpressure is 11.3 psig. In the license
submittal, we've actually requested five psig to
account for future changes and provide some margin
between the limit.
The analysis that determined this was a
conservative analysis in that for determining wetwell
pressure, we assumed containment sprays were used,
which actually resulted in a lower wetwell pressure.
For suppression pool temperature, we assumed direct
pool cooling was used, which actually results in a
higher pool temperature. So for the MPSH evaluation,
we actually have a combination of two different
analyses, resulting in a worse-case condition -- lower
pressure in the wetwell air space and higher pool
MR. WALLIS: Are we ready to move on? We
are somewhat behind the original schedule, but it's
because my colleagues are asking questions. I think
it's appropriate that you continue to ask questions.
But let's see if we can move along.
MR. PAPPONE: Well, I'll try to get
through this as quickly as Ken. I'm --
MR. WALLIS: You're an old hand at this,
MR. PAPPONE: I'm Dan Pappone of General
Electric. I'm the LOCA Process Lead, and I'll be
going through a couple of things here. One is the
feedwater and recirculation line break loading on the
reactor internals, and then later on I'll go through
the Appendix R.
What I've got here are the -- what I'm
showing here are the external loads that come into the
-- from the pipe break that come into the defective
reactor internals that a set of loads that are due to
the break itself. The jet impingement is from the
pipe end of the break, the flow from the pipe end of
the break hitting the vessel. The jet reaction is the
break flow coming out of the vessel pushing. The
annulus pressurization load, that break flow is --
some of that break flow is going into the space
between the reactor vessel and the shield wall and
pressurizing that region. And there's an asymmetrical
loading trying to push the vessel over. And then
there's also a pipe whip restraint on the pipe to keep
the pipe from flailing around out in the drywell
space. And those restraints are on the shield wall.
The loads from the shield wall then get transmitted
through the stabilizer to the vessel.
MR. SIEBER: That would be what we would
consider the nozzle load? Or is the nozzle load
something different there?
MR. PAPPONE: When you're saying the
nozzle, you're talking about the reactor vessel
MR. SIEBER: Right.
MR. PAPPONE: At this point, we've severed
the pipe completely, so --
MR. SIEBER: So you're assuming there is
no nozzle load.
MR. PAPPONE: There isn't a nozzle load at
that point. We're not looking at --
MR. SIEBER: Something less than severing
it completely would create a big nozzle load and maybe
a complete severing of the pipe would not be the most
MR. PAPPONE: On the nozzle, right.
Right. That's what I'd say --
MR. SIEBER: Sooner or later you would end
up with a total break after the nozzle fails, right?
MR. PAPPONE: Right. Or, actually, most
likely it would be a junction between the pipe and the
safe end on the nozzle.
MR. SIEBER: Right. Right.
MR. PAPPONE: And then the other part that
wasn't shown on there was internal loads that are
going to affect the vessel. We've got blowdown
pressure difference loads between the regions, which
we have flashing through the different regions. And
also flow-induced and acoustic loads. In the
Subcommittee discussion, the flow-induced and the
acoustic loads were really the topic of interest. And
for those loads, we're looking at the recirculation
line break as the limiting location. That break is
down low in the subcooled region of the vessel. The
other pipe breaks -- the other large pipe breaks are
up in the saturated region. And the acoustic wave
propagation isn't very good in saturated water
compared to the subcooled water. Down in the recirc
nozzle location, we've got a fairly restrictive area
in that down-comer region, so that's where we get the
MR. WALLIS: Why should this change with
MR. PAPPONE: What changes with EPU is
that because we've got a little more steam flow going
out of the vessel, we've got a little more feedwater
flow coming in, and even though the feedwater
temperature is a little bit higher because we've got
more flow coming in, when we mix that, we end up with
a little bit lower down-comer temperature. And with
lower temperature things like the flow loadings and
the acoustic loadings get a little bit worse.
When we look at -- the components that
we're looking at when we're looking at the flow-
induced and acoustic loads are the jet pump and the
core shroud and the shroud support. In the shroud
support, we're only looking at the acoustic loads
there. It doesn't see -- it's not in the flow field,
so we don't see any flow loads on that.
And the approach that we take when we're
evaluating these loads on the internals is we first
try to fit within the original load definitions with
the break flow driving source term. If we can do
that, we stop there, because if the load definitions
don't change, the structural stresses don't change.
And if we can't fit within those envelopes with
pencil sharpening, we go to the next stage. We look
to see how much margin we have in the stresses to the
allowables, and we eat into some of that margin. And
the third step is to look at the actual stresses
themselves from the original stress calculation and
look for some conservatisms in that calculation.
So the original calculation may have used
whatever the most conservative ASME structural
approach is, and there may be another allowed approach
that doesn't take out some conservatisms or may have
done simple summing of both the first time you do the
square root. Some of the squares may separate the
loads into whatever their timing is. Like the
acoustic load is in the first few milliseconds, and
that's before the flow-induced loads come along. So
we can separate those loads. They don't have to be
MR. SIEBER: For all these steps that you
went through to -- that I would call pencil sharpening
steps, how far did you have to go with Brunswick under
EPU conditions to come up with a reasonable answer?
MR. PAPPONE: That's the next slide. The
components that do see an increase of load are the
ones that are in that core flow and steam flow path.
They're the ones that see an increase in the loads.
And for most of the components, like shroud heads and
dryers and the like, we have margined the allowables,
so we were able to just accommodate those without
having to do any pencil sharpening.
The acoustic loads we've refined our
analysis technique down to a very fine mesh, basically
water hammer calculation and reduced that driving
forcing function. And on those components, the shroud
head -- or the core shroud, the shroud support and the
jet pumps are the ones that benefit from that. And we
did do some pencil sharpening on the feedwater line
break loads to get that down below. That wasn't
fitting in the --
MR. SHACK: So for those you just refined
the thermal-hydraulic analysis, and you didn't have --
MR. PAPPONE: That's right.
MR. SHACK: -- to mess with the stress
MR. PAPPONE: That's right.
MR. SIEBER: I presume that the more
severe of these is the recirc line break, right?
MR. PAPPONE: Right.
MR. SIEBER: Okay.
MR. PAPPONE: Well, for the pressure
difference loading, it's the steam line break that
gives us highest load there because of the rapid
depressurization and the very rapid --
MR. SIEBER: It's a bigger line.
MR. PAPPONE: Right. Well, it's about the
same size pipe, but because it's up in the steam dome
it pressurizes the vessel very quickly.
Okay. Next I'll be going through the
Appendix R, and the case that was presented in the
Subcommittee is really more of a what if beyond
licensing basis case. So it's the only case where
there's a heat up. In all of the Appendix R scenarios
that in Brunswick's licensing basis, they have the
RCIC system available. So there would be no core and
covering heat up. But this is a postulated scenario
that's a what if the RCIC didn't work or something
like that, even though it's a protected system.
So conservatisms in this particular -- or
the scenario for this analysis is we've got the loss
of off-site power, ramp the feedwater down, no credit
for the RCIC and standard with the Appendix R
calculations we've got the nominal core power level
and a nominal decay heat, realistic decay heat.
There are three relief valves that are
used for the blowdown, and we're assuming that the
operators initiate that blowdown at 40 minutes when
they get a diesel started back up so that they have a
low pressure coolant injection pump available for
cooling once the vessels depressurize.
The conservatism in the analysis -- the
biggest conservatism is that 90 percent of the actual
relief valve capacity being used in the analysis,
we're using the tech spec value as opposed to the
actual valve capacity. With the Appendix R analysis,
since this really is truly -- it is a nominal
analysis, we could have taken credit for the full
valve capacity. The ECCS performance values, the pump
flow rates in the valve stroke times and what not,
took those from the LOCA licensing analysis. And
those again are minimums where we could have used
nominal values and not taking credit for the RCIC.
And the results of this analysis, we've
got a temperature of 1458 degrees. We've got an
acceptance criteria for the Appendix R analysis of
1500 degrees, and that's based on no fuel damage.
MR. ROSEN: You said 1450, but your slide
MR. PAPPONE: Fourteen sixty-eight. I
misread it there. This was about 250, 300 degree
increase over the current power case, and that's
primarily due to the limited relief valve capacity,
only using three relief valves. And, say, the
standard Appendix K small break LOCA analysis were
taking credit for five or six valves.
MR. SIEBER: Yes. But you assume three
valves because you're operating from the standby panel
MR. PAPPONE: That's correct.
MR. SIEBER: -- and it probably only has
three valves on it.
MR. PAPPONE: It only has three valves on
it, but the thing is with the three valves, we're more
sensitive to a change in core power, because we're
generating more steam.
MR. SIEBER: That's why you can't
MR. PAPPONE: Right. And these results
are consistent with what we've seen for the other
power uprates in the Appendix R.
MR. SIEBER: It would have been better off
to add another valve to the standby panel except for
the fact that you would have to protect that division,
MR. PAPPONE: We'd have to --
MR. SIEBER: Which would be probably
MR. PAPPONE: Right. We'd have to protect
the cabling and add the logic to it. And the other
part is that this really is a what-if calculation,
because all of their Appendix R scenarios they've
already protected the RCIC, so --
MR. SIEBER: Every calculation is what if
until it happens, right?
MR. PAPPONE: That's true.
MR. SIEBER: Okay.
MR. PAPPONE: Back to Bob.
MR. KITCHEN: This is Bob Kitchen. I just
want to close, discuss briefly the operator impacts
and PSA results. The operator impacts -- of course,
the testing that we have planned, as we've discussed,
is per the ELTR with the exception of large transient
testing. The operational changes that we see we've
talked about the change in instability solution for
the operators. The nature of the power uprate where
we're operating on the power flow map is more
restrictive than our core flow window, so that results
in more power reductions to make rod pattern change.
This is an impact the operators will see. So this is
more of what we've been doing.
Then, finally, there is some small
response in -- small reduction in operator response
time. What we're talking about here is the just the
higher power operation, you know, higher feed flow,
higher steam flows. The transient simulations that
we've run in the simulator is really almost
imperceptible to the operator, and we don't see a
significant impact there.
MR. ROSEN: What did you say about more
power reductions? I lost track of that.
MR. KITCHEN: We were operating on a
powered flow map in an area that's more restrictive.
There's less core flow variation allowed just because
of where we are. And that necessitates rod pattern
changes more often to maintain full power. And to
make the rod pattern change, we'll be doing more power
MR. ROSEN: Come down, make the rod power
change and go back up, and you'll have to do that more
MR. KITCHEN: Yes, sir. So really, all in
all, the operator impacts are relatively small.
The PSA results, just to show you,
basically, the PSA review showed no change in success
criteria or accident sequences. There were no
significant changes in procedures so no significant
impacts. And the hardware changes are like in-kind.
Really, in terms of impact, there's a very small PSA.
There were some slight decreases in operator response
time in the PSA analysis associated with HPSI and RCIC
level control in ATWS, but they were small: 30
minutes currently, 24 minutes under uprate; a six-
When we look at the PSA results, just the
bottom line, across the top here is a current values
for core damage frequency and large early release.
With EPU, our psi review showed basically about 1.6
increase in CDF and about a four and a half percent
increase in large early release. But as we --
VICE CHAIRMAN BONACA: Did you do an
uncertainty analysis on these or are these point
MR. KITCHEN: I'll let Larry Lee address
the analysis. Larry's with ERIN Engineering.
MR. LEE: Hi. This is Larry Lee from ERIN
Engineering. Yes. These are point estimate
evaluations. We didn't do a detailed classic
uncertainty analysis. We did do sensitivity studies.
VICE CHAIRMAN BONACA: So how -- I mean
look at the difference -- 255, 259. You're talking
about four tenths to the minus seven difference, and
this comes from a point calculation which can be off
by a factor of two.
MR. LEE: True. We didn't do -- because
this wasn't a risk-informed submittal, we didn't do a
classical uncertainty analysis. We believe the
uncertainty analysis would be similar to the
uncertainty shown in NUREG 1150, and we don't believe
that the Brunswick PSA has any unique plant features
that would change the results from that uncertainty
MR. KITCHEN: The other point is that when
we factor in the SLC boron concentration increase,
which we have committed to since the ACRS Subcommittee
meeting, with that change, we go from -- and ATWS is
a highly weighted accident PSA. When we make that
change alone, going from two-pump required success
criteria to the one-pump required success criteria, as
you can see it reduces the impact.
MR. ROSEN: To what do you attribute the
slight increase in the EPU case, in the point
MR. LEE: The increase in the point
estimate is due to some decreased time for available
operator actions related to level control. So the
decreased time available showed resulted in a slight
increase in some human error probabilities.
MR. POWERS: Are we looking at a balancing
of negative and positive things? I mean it seems to
me you've done some -- you're doing some things
stabilizing your grid, which clearly should reduce
your risk. At the same time, you're decreasing the
opportunities for the period of time available for
operator actions, which apparently increases your
risk. Is the magnitude of that increase masked by
some of the grid stability things that you've done?
MR. KITCHEN: We didn't -- Larry, we
didn't credit the --
MR. LEE: No. We did not credit any
potential positive impacts by increasing grid
stability. Like, for example, decreasing the loss of
off-site power initiating event. The only one we --
in sensitivity studies, we took credit for the SLIC
modification. We also did a sensitivity where we
increased the turbine trip frequency by ten percent to
account for any uncertainties in any potential
increases in SCRAMs due to Plant modifications or
potential decreases in SCRAM margins.
MR. KRESS: What is your conditional late
containment failure probability?
MR. KITCHEN: I'm sorry?
MR. KRESS: The conditional late
containment failure probability? It's a Mark 1
containment. Usually those things are done around
MR. LEE: We didn't recalculate the late
containment failure probability for the Level 2
MR. KRESS: Well, it probably doesn't
impact it except it gives you a late containment
failure frequency which is basically equivalent to
your CDF, which would make it like two times ten to
the minus five. I just wondered if that gives anybody
any pause for reflection other than me. Late
containment failures we know of impact on either. I
recognize that Reg Guide 1.174 doesn't talk about late
containment failures, which is one of the things I
think's wrong with it. But I just wondered if the
staff looked at that and gave them any pause for
reflection at all?
MR. WALLIS: Are you going to ask the
MR. KRESS: Pardon?
MR. WALLIS: Are you going to ask the
staff that when they --
MR. KRESS: Well, I think that's a staff
question. Did they think about that and did it give
them any serious heartburn at all?
MR. HARRISON: If I can -- I think the
answer is fairly quick. This is Donnie Harrison from
the PRA branch, and I'll give you two parts to the
answer. The first one is we didn't look at it. The
second part is that it is something that's being
thought about, but it's not in the guidance now. And
it's something that the staff does need to think
about. Under what conditions would you really want to
look at the late containment failure probability? And
I think unlike South Texas, on their exemption, there
was a case where we didn't want them having some
systems that only come into play on the late
containment getting dropped. So there will be cases
where that is looked at, but it's something I think
the staff needs to think through completely to come up
with some guidance on when you would apply it and when
MR. KRESS: That might be some sort of
update to the Reg Guide 1.174 at some time maybe?
MR. HARRISON: I'm not involved in that,
but I would hope in that revision they think about
that type of thing. And I'll take that back to them.
MR. KRESS: Okay.
MR. WALLIS: So let's just clarify.
That's since we met you a week ago, you have agreed
with the staff that you will install the SLIC
modification. That's part of your application now?
MR. KITCHEN: Yes, sir; that's correct.
MR. WALLIS: Okay.
MR. KITCHEN: And installed in such a way
that it results in single-pump --
MR. WALLIS: Single pump, right.
MR. KITCHEN: -- success criteria.
MR. WALLIS: Thank you.
MR. KITCHEN: This concludes the
presentation that we have prepared.
MR. WALLIS: Any more questions for the
presenters? I'd like to move on to the staff
presentation. Thank you very much.
MR. MARSH: I'm going to go ahead and get
started while people are shuffling around. Good
morning. My name is Tad Marsh, and I'm the Acting
Deputy Director of the Division of Licensing Project
Management in NRR. We are here today to summarize our
review for the extended power uprate application for
the Brunswick units.
The staff has conducted a thorough review
of the Brunswick Plant and those areas potentially
affected by the power uprate, with the focus of our
CHAIRMAN APOSTOLAKIS: Excuse me. Who is
MR. MARSH: Oh, I'm sorry.
CHAIRMAN APOSTOLAKIS: Dr. Wallis, are you
going to need extra time?
MR. WALLIS: I'm not taking any time. The
staff is taking the time. I think the staff may need
some extra time, because --
CHAIRMAN APOSTOLAKIS: We're supposed to
finish at 10:30.
MR. WALLIS: That's right.
CHAIRMAN APOSTOLAKIS: Twenty minutes is
MR. WALLIS: Tad Marsh has no -- how much
time do you need?
MR. CARUSO: We had assumed that we would
have an hour.
MR. WALLIS: No, you weren't even allowed
an hour originally.
MR. CARUSO: Forty-five minutes.
MR. WALLIS: Can you do it in a half an
MR. CARUSO: We can give our presentation
in a half an hour.
MR. WALLIS: The problem is our colleagues
CHAIRMAN APOSTOLAKIS: Well, the whole
idea is --
MR. MARSH: We probably need a half an
hour to go through our slides. If there's no
questions, we can go through it --
PARTICIPANT: If we're not going to ask
questions, there's no point having a meeting.
CHAIRMAN APOSTOLAKIS: No, no, no. We
should ask questions.
MR. CARUSO: We'll try to be efficient and
CHAIRMAN APOSTOLAKIS: Huh?
MR. CARUSO: We'll try to be efficient and
CHAIRMAN APOSTOLAKIS: Well, the best way
is to actually skip some slides. Can you do that
MR. CARUSO: We'll try. We'll try to go
CHAIRMAN APOSTOLAKIS: Or does he have to
go through five letters of review?
MR. MARSH: Why don't we --
MR. WALLIS: Maybe, Tad, we could cut down
MR. MARSH: That would be fine, but I do
want to make some comments.
MR. WALLIS: Sure, certainly.
MR. MARSH: Okay.
MR. WALLIS: So let's try to --
MR. MARSH: I do have some things I need
to say. Okay. I'll skip some of the boilerplate, but
I do want to concentrate on the large transient
testing statement. And I want to reemphasize what I
said earlier regarding the large transient testing.
And as you know, the licensees have proposed not to
conduct such tests for EPUs. And as I said earlier,
the Director of the Office of Nuclear Reactor
Regulation has tasked the staff to develop generic
guidelines for testing programs, including power
uprates. And this effort will formulate guidance to
determine whether or not such tests are to be
conducted, including the large transient tests.
During previous meetings with power
uprates, the Committee has commented that such
guidance should be developed to provide the staff,
licensees and the public with clear criteria for
evaluating these requests related to testing. We
intend to provide the plan to the Office Director by
May 31, 2002, and we will of course keep the Committee
involved in those discussions.
I want to emphasize, though, that the
charge from the Office Director was not to require
tests, it was to develop criteria such that the staff
can evaluate in some more routine manner whether they
should be conducted or not. The charge was also not
citing that there was any immediate safety concerns
absent those tests. So I wanted to emphasize that.
Now, as I said, we'll be glad to discuss
this with you further, but because of the nature of
the issue and how it arose and how it's being pursued,
we should probably conduct it in a manner different
than having a public meeting. And we'd be glad to do
that with you and for you at your choosing.
With that, Mr. Chairman, I'll turn it over
to Brenda who's going to go through our presentation.
MR. ROSEN: The difficulty I have with
that is that the Panel's recommendations may or may
not be applied retrospectively, and then that -- I
think the Committee needs to understand that point.
MR. MARSH: Yes. What could I say? The
Office Director, in transmitting this thing to Brian
Sheron and asking him to develop criteria said to use
the normal process for deciding whether this should be
back-fit or not. It said to use your budgeting
process in terms of laying out the time frame period
to be done and the endorsement of the Panel's
recommendation. The Panel's recommendation itself was
to develop the criteria, as opposed to require
testing. So there was not an endorsement to require
testing, rather to develop the criteria. And there
was no criticism specifically of the final judgment
that has been made in these past cases; rather it was
the process by which the decision was made.
MR. ROSEN: Try to make this clear. If
the Panel's recommendations are accepted and
ultimately criteria are developed that would apply to
Brunswick and require large transient testing, how
would that end up being applied to Brunswick?
MR. MARSH: We would have to go through a
50.109 process. We would have to go through a back-
fit evaluation to decide whether to change the
licensing basis for this Plant, unless there's an
adequate protection issue or there's a compliance
issue. But we have to go through --
MR. WALLIS: Is this assuming that they've
already been given the license?
MR. MARSH: Yes. Yes.
MR. WALLIS: But suppose the license has
not been modified by then, what do you do?
MR. MARSH: As I said earlier, if the
license were not, then it would have to be -- the
outcome would depend upon what the evaluation said.
If you haven't issued the license yet, then you could
theoretically apply that judgment in a forward manner
as opposed to a backward manner.
MR. WALLIS: Does that answer your
MR. ROSEN: Yes, that answers it.
MR. MARSH: Let me just -- we're on
difficult grounds here because of the nature of the
issue and the nature of how it arose. I want to just
call your attention to the memo that you have before
you and the safety perspective that was embodied in
that Panel recommendation. I think that's an
important element, and it was an important
characterization from the Office Director to the
Associate Director in terms of the timing of how this
thing should be developed. There was no urgency
And those are my statements, Mr. Chairman.
I'd like to turn it over to Brenda Mozafari to
MS. MOZAFARI: Okay. My name is Brenda
Mozafari. I am the Project Manager for the Brunswick
review. I'm going to skip over the overview, just
make a few comments to the effect that they provided
the application last August and for the most part it
follows ELTR 1 and 2. Exceptions were noted in their
application. It is not a risk-informed submittal, and
it did base a lot of issues in their submittal on
previously accepted aspects of previous EPUs.
Now, I just show -- just so that you can
see, there were reviewers and reviews done in all
these areas, and those you saw reflected in the safety
evaluation. But we tried in this presentation, albeit
a little shortened, and it was presented during the
Subcommittee meeting, but we tried to focus on some
aspects of the staff review and certain areas that the
ACRS seemed to have some potential added interest. So
with that, I'd like to turn it over to the Chief of
the Reactor Systems and Fuels Group of NRR, Ralph
MR. CARUSO: Since my boss is sitting
here, I should explain that I'm not the Chief of the
Reactor Systems, Brenda.
MS. MOZAFARI: Oh, excuse me.
MR. CARUSO: I'm only the --
MS. MOZAFARI: Section Chief.
MR. CARUSO: I'm only the Section Chief of
the BWR Nuclear Performance Section.
MS. MOZAFARI: I promoted you.
MR. CARUSO: This is not the moment for a
What I wanted to talk to you about, and I
wouldn't be here -- the reason I'm here is that
there's an issue that keeps coming up during these
discussions with the Committee and involves the
applicability of the analytical methods that are used
in doing these power uprates. And I would like to
discuss -- start the discussion this morning with a
review of this issue and a restatement of discussions
that we've had in the past on code applicability.
This is the fourth significant BWR power
uprate that we've done: Duane Arnold, Dresden, Quad
Cities, Clinton and Brunswick. And I wanted to
describe to you today code applicability. I want to
discuss code applicability and how we assure that the
codes are used appropriately.
I'd like to open first with a discussion
of our review scope. How do we decide to review and
to look at what we review? This point in the process
we are gaining most of our -- making most of our
review decisions based on experience from prior
reviews, the three that we've done so far. Now we've
got a fourth. They give us a lot of experience. They
give us a lot of ideas about what to look for in the
We have some guidance documents, we have
a Standard Review Plan, we have Reg Guides, and we
have the topical reports that are used to -- that
describe the approved methodologies. We use those
guidance documents as well as -- as far as they go.
MR. WALLIS: Now this SRP is a general
SRP, it's not for uprates.
MR. CARUSO: This is not for uprates, but
realize that the SRP -- it's a general SRP. It was
designed originally to license these plants, so it
includes all the areas that would normally be
considered if you were going to relicense this Plant,
start from zero. And therefore, theoretically, it
should be applicable to reviews for power uprates. So
we use that guidance in the SRP and in the regulatory
We are also doing, simultaneously with
these power uprates, other licensing actions. We're
doing tech spec amendments, we're doing topical report
reviews, we're doing lots of other licensing actions,
and we learn from them. We have information from them
that we consider.
Fourth, we look at operating experience
and feedback from the field. We get licensee event
reports, we get deficiency reports from licensees.
All that information is considered. And, finally, all
this information is put together by knowledgeable
people, people that are paid to do this job and
exercise their judgment to decide what's important and
what's not important.
So this is where we get the idea about
what to review and what not to review. And you should
realize that what we don't review is a lot. The vast
overwhelming majority of the information that's
developed for these power uprates is not reviewed by
the staff. GE has 40 people working on each power
uprate. Licensees have probably another 100. I have
three people. I can't review everything they do. I
can't even review a significant fraction of what they
do. So I have to make a choice.
Now, one of the issues that's come up is
how do I know the codes are the right codes to use?
Once again, this is judgment, but there's actually a
bit of a basis to this. This is a BWR and the BWR
methods have been applied across the entire BWR range,
from probably Big Rock Point all the way up to Grand
Gulf. And the power uprates that we've seen so far
have all been within the range of applicability for
which there are already plants operating at those sort
of power levels and power densities. So these codes
are not being applied outside a range of applicability
for which they're already in use right now.
MR. WALLIS: I guess a question that
several of us raised was, yes, it's an approved code,
but you know that how you use the code can make a
difference to the answer. So you have to worry about
how the code is used.
MR. CARUSO: That's in my second slide.
I'll get to that in a second.
The second part of this was we're not
using any new codes. There was a big flap about power
uprates about eight years ago at Maine Yankee because
someone decided to use -- among other things, a
licensee decided to use a new code for a power uprate,
and it hadn't been well-validated. We're not using
new codes for these power uprates. They've been in
existence for a while, and they're mature. So there's
not a Maine Yankee scenario here.
In addition, even though the codes have
been around for a while, GE has been making
modifications to them continuously. We recently
completed a review of a change to the SAFER/GESTER,
we've looked at the ODYSY code, and we have ongoing
experience with TRAC-G. We completed a review for
AOOs about a year that we discussed with the
Committee. So the staff has kept in touch with these
codes and these methodologies.
Now, I'd like to go on to the question of
how do we know that they're being used appropriately?
And I'll start by asserting that the vendors use the
codes rigorously. The limits for using the methods
are described in topical reports. For GE, there's a
topical report known as GESTAR. It's a massive
document. It describes in intricate detail how to do
the calculations. GE takes these limits from the
topical reports and it develops procedures so that it
can do production calculations. And that's an
important phrase -- production calculations.
These production calculations are done by
knowledgeable engineers, they're done in accordance
with written procedures. They have to be done that
way in order for them to be done efficiently. And
those procedures are checked by internal quality
assurance people in GE, reviewed by several levels of
management, they're attached to a large Appendix B
quality assurance program, they're reviewed by
licensees who have a vested interest in making sure
they're done properly, and the inputs are controlled.
GE has a central database. The inputs are also
checked by licensees. So there are a lot of controls
on the use of these codes to prevent them from being
used too creatively.
MR. SIEBER: It's my impression that GE
does all the calculations necessary for these kinds of
analyses with the same group.
MR. CARUSO: Yes.
MR. SIEBER: And that -- for all BWRs?
And that licensees don't do any of these calculations
independent of General Electric. Is that true?
MR. CARUSO: I don't know. You're talking
-- that's probably going to a plant-specific issue.
There may be some licensees that do some containment
calculations of their own, for example.
MR. SIEBER: I accept that.
MR. CARUSO: The fuel calculations,
though, I believe are done by the fuel vendors, and I
don't know of the other -- how much technology
transfer goes on between the other vendors, but I
believe GE does not do much, if any.
MR. SIEBER: Okay.
MR. CARUSO: I'd have to ask them, but I
believe they don't do it.
MR. WALLIS: It does mean that they're
very dependent on the results prepared by GE. They
are the source of the numbers, which are quoted and
approved and all that. Nobody else is.
MR. CARUSO: Well, GE is responsible for
the results, but they depend on inputs that are
received from the licensees about the plant
MR. WALLIS: Right.
MR. CARUSO: About the operating
procedures, about the assumptions for operator action
times. So there is -- it's not all done by GE in a
black box; the licensees interact with them.
MR. ROSEN: Accepting that point, could we
have the GE guy tell us how much is done by the
MR. CARUSO: Fran?
MR. ROSEN: -- in Brunswick, in
particular, but more generally if you can.
MR. BULGER: This is Fran Bulger from GE.
We have made these codes that are used in these
licensing analyses available to the licensees, and
most all of them have, at least to some extent, some
of the codes. At least -- most all have the core
design codes, and many have the transient analysis
codes. A number of them actually have done in-house
training with some of these licensing codes, so they
try to see if they can reproduce some of the GE
We've held training up in Raleigh with
some of the CP&L staff to get into some more of the
details of the transient codes. The CP&L has a number
of the GE codes. A number of the utilities send their
staffs to GE and do actually perform some of the
licensing analysis at our site.
MR. CARUSO: So you see that the licensees
and GE work together on this. This is not something
that's done by GE in a vacuum.
MR. WALLIS: But there is no independent
calculation made by somebody else.
MR. CARUSO: That is correct.
MR. SIEBER: It was my impression --
MR. CARUSO: At least not by the staff.
MR. SIEBER: -- that if the licensee, on
its own volition, wanted to perform the calculations
and make those calculations the record calculations
for the plant, they would have to have all this
infrastructure that GESTAR discusses, including an
approved topical that describes how they will do the
MR. CARUSO: That's correct.
MR. SIEBER: And that's a big hurdle to
MR. CARUSO: I believe at this point that
we have not approved the use of any of the GE methods
by any licensees. Is that correct, Fran?
MR. BULGER: That's not correct. Southern
Nuclear is approved to use GE methods.
MR. CARUSO: Okay.
MR. SIEBER: That's pretty helpful.
MR. CARUSO: That's something I did not
MR. BULGER: That's the only utility that
MR. CARUSO: Is that the only utility?
MR. BULGER: For the GE methods. Excellon
had been using some of the GE methods to do slow
transient analysis and some of the core design work.
Recently they've decided to contract that out to GE.
MR. ROSEN: This is, of course, not true
in the PWR side.
MR. CARUSO: That's correct. That's why
I'm careful about saying this.
MR. ROSEN: Numerous PWR utilities do
their own calculations and have approved topicals, as
far as I know.
MR. CARUSO: That's correct.
MR. SIEBER: Some do, some don't.
MR. ROSEN: Some do, some don't, but there
are quite a few that do have approved topicals and do
their own calculations.
MR. DRESSER: This is Tom Dresser with
CP&L. Though CP&L does not do licensing calculations
independently from GE, we do, as part of our own
review and oversight program, we do quite a bit of
independent calculations. We have to access to some
of the codes from GENNE, and we also have independent
neutronic methodology. So it's -- we do, in addition
to oversight of the vendor, we do alternate
calculations for our own review purposes.
MR. CARUSO: So the licensees -- in this
case, this licensee does do some independent checks,
independent calculations, but the staff does not for
these normal -- for these sort of applications where
a licensee or GE is using an approved methodology in
an appropriate way, in a way that is not, as I put it,
MR. RANSOM: Ralph, I think you said that
they have made some changes to these codes?
MR. CARUSO: They make changes on a
periodic basis, yes.
MR. RANSOM: Have you looked at their
review procedure or quality control or quality
assurance procedures, I guess, to assure that these
changes do not change past results?
MR. CARUSO: The changes that I was
talking about have been reviewed by the staff. They
submit a revision to the topical report, and we review
that, and we assure that the change does not -- well,
it usually affects the results in some way, but we
assure that it's an appropriate change, that it's
justified and documented and it has a basis.
And then my last two items here we've been
doing audits of these calculations as part of these
power uprates, where we will go to GE Wilmington or GE
San Jose and we have a team of five people who
actually look at the detailed design record files for
selected calculations. Based on their judgment, they
decide, "I want to go look at LOCA this week. I want
to look at ATWS next week. Next time I want to look
at Standby Liquid Control System."
MR. RANSOM: I guess my concern was that
they have a procedure in place such that someone
cannot simply put in an ad hoc change that a
particular individual wants.
MR. CARUSO: It's my understanding that
the proceduralization of the analysis process is done
to prevent that from occurring. That's a major sort
of change, and they don't like to do that.
MR. SIEBER: It's my understanding that
the vast majority of the changes are basically
corrections that have somehow or other been discovered
through the use of the codes, and they're required to
be submitted annually.
MR. WALLIS: I'm going to be in great
trouble with my Chairman if we don't proceed.
MR. CARUSO: I'm sorry I'm taking so long.
I'm just about done here. This has been philosophy.
Zena is going to talk about two areas where during our
review we actually did identify some problems and
pointing out the value of doing these audits and doing
them in a targeted fashion. And she's going to
explain to you what she found.
MS. ABDULLAHI: Good morning. My name is
Zena Abdullahi, and I'm the Reactor Systems -- one of
the Reactor Systems Reviewer for the Brunswick EPU
application. I'm going to try to skim through my
notes and try to speak fast since we are pressed for
In the previous EPU presentation, you
asked us to discuss specific areas of review that
would give you a sense of our review process.
Therefore, we did decide -- we decided that we will
pick up two areas of examples and try to present it to
you to show you to the detailed level that sometimes
we look into things. We've decided to address today
ATWS and Standby Liquid Control.
In the ATWS case, one of the reasons we
selected ATWS because it was -- the peak pressure was
high. The PUSAR reported a peak pressure of 1492 psig
compared to 1500. And we decided, therefore, to look
further and to check since it's a two-unit application
and the units have many similarities but they do have
also some differences, including bypass capacities and
the orifice sizes of the units.
We then decided for the ATWS to make sure
that, at least in terms of peak pressure, that the two
units the most limiting is used in terms of plant
condition. And we found out that in fact, yes, the
analyses were based on Unit 1, which had a bypass
capacity of about, I think, 20.6 percent. This is the
turbine bypass capacity. And that for Unit 2, in
fact, which has a larger bypass capacity of 69.6
percent for the EPU rated thermal power, that for a
specific event, called the pressure regulator failure
open, that Unit is in fact more bounding.
The reason the Unit would be more bounding
would be that you would have a failure of the pressure
regulator to maximum demand. It would open faster, it
would steam out through the bypasses, and the unit
that actually depressurizes through the lowest --
pressurizes earlier would be the one that would have
MSIV close earlier. And, as such, then you would have
the pressure go up, the boards collapse, the power go
up, and that would be the unit that in terms of peak
pressure would be more bounding.
We have asked the Licensee, and they have
confirmed that, yes, this unit -- the analyses were
based on Unit 1 in which the loop and the MSIV closure
were the bounding case, and they reanalyzed the Unit
2 using the Unit 2 bypass capacity. However, they do
actually use plant-specific parameters in order to try
to reduce the conservatism. And one of the things
that they have done is they changed the pressure --
the SRV set point, and instead of using the GE value
of 44 psig, they used three percent tolerance, which
is the plant-specific value, in which case that comes
to 34 psig. Then you would end up having ten valves
popping open earlier, which will help you reduce the
And as a result, the peak pressure that --
it basically compensates for the impact that you would
have got from the larger bypass capacity. And from
that they did in fact come up with a lower peak
pressure of 1487 as opposed to 1492. However, the
staff did go through the details officially that we're
comfortable with the value that they came up with and
can say that, yes, they do meet ATWS, and the peak
pressure is acceptable as long as it's below the 1500.
I'll go faster. With the --
MR. POWERS: Let me ask a question about
MS. ABDULLAHI: Yes.
MR. POWERS: You indicate that they
changed the set point away from that recommended by
General Electric. Is there any possibility of error
in making those set points?
MS. ABDULLAHI: You mean the tolerance
value or error in -- for the set points, yes. I mean
if set point drift goes up, their ATWS analysis would
not work. But the GE value of 44 psig was based on
certain type of valve that they knew had a propensity
for high drift.
MR. POWERS: What I'm asking you, or I'll
get around to asking, I guess, is that do you do a
calculation and say, "Oh, what if by mistake the put
their set points in incorrectly?"
MS. ABDULLAHI: Oh, you mean the numbers.
MR. POWERS: Yes.
MS. ABDULLAHI: Well, we are relying on
their analysis. What we actually check is key
parameters, limiting conditions, limiting components
out of service. We look more on the sequence, and we
look if the result makes sense and if there's
sufficient margin. But we have not inputted the
Having said that, from the audit point of
view, I don't see that it's such a far-fetched thing
that -- the way we do it we look at the plant-specific
and then we also look at GE methodology. And I don't
see that it's not possible that at one point we would
actually go to that degree of some other audit, but we
haven't done it this way.
MR. POWERS: So the impression I'm getting
is that you look at what they have done, and you say
is that acceptable, but you don't do what my colleague
here is suggesting is you might say, "Why don't you go
back and make some other assumption?"
MR. CARUSO: We don't do our own
sensitivity studies to look at the potential errors
that might be made in input values by licensees or by
MR. MARSH: Just a reminder these values
are technical specifications, and they're, of course,
bound by those, and they have LERs and other reporting
criteria should they find these out of specification.
MS. ABDULLAHI: I think I have time to say
a few things about the SLC.
MR. WALLIS: I think we're all interested
in that one.
MS. ABDULLAHI: Oh, I see.
MR. POWERS: It's not for lack of
MS. ABDULLAHI: Maybe I should skip it.
All right. The SLC issue, the PUSAR did not contain
an SLC relief valve margin evaluation. And the
objective for us presenting this to you is to tell you
that we do not only look most cases at only what is
discussed in the ELTR 1 and 2. If there is an
information notice or other information that would
tell us some issue, we would actually carry it
through, because we would think what would be the
impact for the EPU, and then we would look into it.
And this is the case that we have done that.
In this particular case, the concern is
that the SLC System would -- okay, what we would like
to know is whether the SLC System could inject into
the reactor at the assumed time, in the analytically
assumed time, based on the predicted pressure and
without lifting of the SLC relief valve. Because
there's a set point in which the SLC relief valve will
lift, and if the pressure in the ATWS analysis is at
some point, then you might end up getting the relief
And in the initial we asked the Licensee
to do that evaluations, and in the initial evaluation,
the Licensee did come back and say that, "Well, the
value -- we have actually no margin." And as a result
of it, they went again and recalculated their two-pump
system losses. The original system losses was based
on 1984 GE evaluation. So they substituted that with
their own system loss test. They also calculated the
plant-specific using plant-specific elevation head
calculations, and then they came up with a better
margin. And it's a positive value, but it was still
The staff could not, at that point -- the
staff accepted it for several reasons. One reason is
the value is positive, and the margin belongs to the
licensee. However, the staff felt that it was small
and had several discussions, and the Licensee did
recognize it. The Licensee did recognize it, and they
actually are going through with their own system
upgrades. And as a result of that, they will --
informed us, "Yes, we will increase the margin by
changing out the valves." However, it's their own
call to make. We can only encourage and support. And
we have been told that, yes, they are making it. We
have a letter that they sent us in which they told
that, "We have already ordered the valve change-out
and we will change."
MR. SIEBER: Actually, restructuring SLC
operations to one pump is a benefit from the
standpoint of margin.
MS. ABDULLAHI: Yes, it is, because if,
for instance -- let me first make another point of
view addition to that. Even if they go to one-pump,
single-valve success criteria and they will be able to
shut down the reactor, the Licensee intends to stop
both pumps, because they do not want to change their
EOPs or retrain their operators.
MR. SIEBER: On the other hand, that means
there's greater chance that you'll lift a relief valve
with two pumps.
MS. ABDULLAHI: Exactly. What would
happen is if one pump can do the job and you stop both
pumps, even if the relief valve pops open and recycles
back to the tag, you still would put in enough boron
concentration to shut down the reactor, probably more
than usual. So we have accepted it.
However, there are two license conditions
that are in the easy application. And the two license
conditions basically deal with the fact that when they
load the second batch of GE14 fuel, they would need to
increase the boron concentration, and as such we would
like to have an amendment request submitted in advance
before they do the load -- load in the GE14. So
there's that amendment request license condition.
Secondly, the Licensee had decided to
commit to the single-pumps with valve success criteria
in a sense of having a sufficient boron concentration
to be able to achieve shutdown using one system. And
that is also a license condition for the application.
Thank you very much.
MR. WALLIS: Now, I'm trying to see what
would the ACRS might say about this, the letter. You
have agreed with the Licensee, it seems, since our
last meeting, they will install these modifications.
So this -- first we need to say less to encourage
this. Has it already happened?
MS. MOZAFARI: It's happened.
MR. WALLIS: Okay. Thank you.
MR. SIEBER: Go ahead with your
conclusions. I have something to say after you're
MS. MOZAFARI: Okay.
MS. ABDULLAHI: We have reviewed the
Licensee's application for EPU, and we have concluded
that -- from all the reviews, we have concluded that
BSEP units can be operated safely to 2923 megawatt
thermal, and the Licensee's analysis has been
demonstrated it can support this uprate.
MR. LEITCH: I take it by that statement,
then, you have no problem with allowing credit for the
five pounds containment pressure?
MS. ABDULLAHI: I am not --
MS. MOZAFARI: She's the reactor --
MR. MARSH: That's next. That's not this
one -- that's not reactor systems, that's containment
MR. WALLIS: It's very similar to what was
granted at another plant.
MS. MOZAFARI: Richard? Richard can speak
to that, Richard Lobel.
MR. LOBEL: This is Richard Lobel from
Plant Systems Branch. No, we don't have a problem
with it. It was considered in the review. It's a
small fraction of the total containment pressure which
was calculated to be conservatively low. And what
we've done on this review is consistent with what
we've done in other reviews and what we've discussed
with ACRS in the past.
MR. ROSEN: My comment is that this is an
excellent piece of work, and the reviews that have
been done have found important things, and I want to
commend you on that. One of the concerns of the
Committee has been one central aspect of core design
for these uprates and the limited amount of review we
actually do. You described you do fairly little, but
we do only a piece of what we could do is small also.
So it seems to me that I derive considerable comfort
from the fact that you are out looking at these
analyses, but this a bad news/good news story. The
good news is you're out looking, the bad news is you
found some substantive things that were wrong. So my
encouragement is to keep looking and to make sure that
you do -- I think this Committee has made this point
in the past, that these audits that you do have great
value and should be continued.
MR. CARUSO: For the BWRs, because of the
interest, because of the large amount of the power
uprate, we do intend to do that. And we do intend to
do it on a focused basis. We don't intend to look at
the things that are listed in the guidance documents,
because everyone knows that's what we're going to look
at. So those are the ones that are always right.
We're looking at the things that aren't -- we're
trying to look at the things that aren't listed in the
guidance documents, and we get hints about where to
look by --
MR. MARSH: Operational experience plus
any types of other evaluations that come up in the
MR. CARUSO: By thinking about these
MR. MARSH: Right. I did want to point
out that in terms of the SLIC review they've just gone
through, this was a topic that came up as part of an
operational experience. So operational experience
vectored us into, and that's why we focus on this
topic, which is building on Ralph's thought of that
being a source of staff scope concerns.
MR. CARUSO: We look at as much as we need
to look at to make a decision. And we're comfortable
with the level of review at this point.
MR. MARSH: Ralph mentioned three staff.
I want to say something about three staff. If the
Agency felt like there was an operational experience
that warranted more staff to be devoted to this type
of audit or confirmatory calculations, the Agency
would devote the staff that it needed to do these
things. So I want you to understand which comes
first, the chicken or the egg. Ralph has three staff
because that's what we think is needed at this point.
If more staff were needed, we would go through a
budget process and decide whether it were needed and
devote more staff to it. So we are driven in
resources by the safety concerns that these staff are
MR. WALLIS: So somebody made the decision
that for all these uprates having to do with GE
reactors, that the ELTR 1 and 2 and all that were so
good that you didn't really need any kind of work to
MR. MARSH: Well, you've heard some
independent calculations beyond ELTR 1. You've heard
Rich talk about some containment calculations which he
has done beyond what the ELTR 1 leads you to do. The
SLIC work that's here is not -- the SLIC doesn't tell
Zena to do the type of reviews that she does. This is
beyond -- this is -- the ELTR doesn't tell Ralph what
to do in audits.
MR. CARUSO: Interestingly enough, in the
SLIC case, it's not a question of the methodology
changing, it's a matter of what point they pick on the
curve to assume as the peak pressure. And there were
some assumptions made about when the operators would
start the SLIC system and the pressure at that point.
And that's not a calculational issue, that's a much
bigger, what we would call, methodology issue.
So doing an independent calculation would
not have told us anything in the SLIC area. We had to
look at what they did with the numbers and what
judgments they made with the numbers. And we looked
at the operating experience and what the operating
experience told us about the assumptions. So you have
to fit them all together. That's why you need
somebody, a person who's knowledgeable and can make a
judgment about what's necessary.
MR. MARSH: The importance of Ralph's
audits going beyond, looking over the fence, can't be
MS. MOZAFARI: Right.
MR. MARSH: He goes beyond what you would
expect to be looking at to see whether those other
areas that are of concern, and if concerns were found
in that area, that would widen the staff's scope
depending upon the safety significance. And, also, we
rely on Part 21, we rely on licensee event reports, we
rely on a lot of elements to determine our scope.
MR. CARUSO: In the area of core design,
we have been spending I believe Ed Kendrick, who's
here, did look at some core design issues during
Brunswick review or during one of the earlier ones.
So we have been looking a little bit at the core
design, but in a lot of cases we just don't think it's
worthwhile to look at calculations that have been done
on a routine basis for a long period of time using
well-established methodologies. It's just not
MR. WALLIS: Ralph, can we move quickly
through the rest of the slides?
MR. CARUSO: I'm sorry, excuse me.
MS. MOZAFARI: Ralph's going to cover the
appendix, our evaluation from the fuel --
MR. CARUSO: I don't have the slide in
front of me, so I'm going to have to read from the --
MR. WALLIS: I think we've all read it by
MR. CARUSO: We've seen this?
CHAIRMAN APOSTOLAKIS: Yes. We've read
it, and the last bullet is your conclusion.
MR. CARUSO: I'll make one more point
about this. There was a concern about the increase in
the temperature from less than 1200 to close to 1500.
It's our understanding that the less than 1200 number
was not actually a calculation but was an estimate.
So we would say it's not really fair to make a
comparison between an estimate and a calculation and
say the value went up by 300 degrees.
And I agree with the points that Dan
Pappone made. Those are reasonable assumptions made,
using a reasonable code, and they came up with an
answer that is reasonable, and we accept that. We
don't see any reason to redo the calculation.
MR. WALLIS: Okay. Thank you.
MR. CARUSO: Thank you.
MR. MARSH: Okay. Mr. Chairman, would you
like us to go through the mechanical engineering
presentation? Would you like us to focus on
MR. WALLIS: I think the bottom line is
that you think is everything fine.
MR. CARUSO: Yes.
MS. MOZAFARI: That's the bottom line. So
you're not interested in hearing it? That's fine.
MR. CARUSO: Okay.
MR. WALLIS: So you believe Dan Pappone's
analysis about acoustic loads? You're happy about the
acoustic loads issue?
MR. MANOLY: Yes. I just want to correct
-- this is Kamal Manoly from the Mechanical Branch.
Apparently, there was some misunderstanding about the
magnitude of the loads from the pipe break, and
they're dependence on the pressure and the temperature
in the line and not the flow rate.
MR. WALLIS: Right. It depends on the
pressure in the line mostly, isn't it, and not the
flow rate. Yes.
MR. MANOLY: And the temperature.
MR. WALLIS: Right.
MR. MANOLY: And I looked at the tables --
my lead reviewer is not here this week, but I looked
at the tables of the results of the difference in
pressure. Slight, very slight increases in pressure.
VICE CHAIRMAN BONACA: Please speak into
MR. MANOLY: Yes. There's very slight
increases in the pressure, the differences in the
internals. So the stresses increased are fairly
MR. WALLIS: So you have checked this
point raised by the Subcommittee, and you've come to
the conclusion it's not an issue.
MR. MANOLY: Right.
MR. WALLIS: I think that's all we need to
MR. LEITCH: I just have a question about
the overall efficiency of the process, and we
discussed it a little bit at the Subcommittee meeting.
But I suspect that there are going to be a large
number, perhaps almost all, of the BWRs in this cube
to get power uprate. And it seems to me that this has
taken an inordinate amount of time, a very large
number of RAIs involved in the process, and I just
wonder if we can't learn something from the license
renewal process, which seems to be running much more
smoothly with a fairly low number of RAIs. Is there
a more systematic way in which this type of a review
could be conducted?
MR. CARUSO: I believe that for the BWRs
MR. MARSH: Let me give it a try from
here, because I want to answer it globally. I talked
a little bit about it at the Subcommittee --
MR. LEITCH: Yes. That was my question
was really a global one.
MR. MARSH: Yes, sure. Let me try, Ralph.
We are committed -- as you say, we are committed to
get to the Commission by March 26 with some effort to
try to improve the efficiency and effectiveness of the
reviews. And we are going to talk with the Commission
on July 10 at a Commission meeting with license
renewal. Because they've charged us to look at the
license renewal process as they improve their
efficiency to see whether we can draw from some of the
benefits that they have found in terms of the process.
So we are charged to do that. And we hope to meet
with you and talk with you about that process before
we meet with the Commission; that's our intent.
A couple things. CPPU, the reliance on
CPPU as a process will help us in some respects. It
will help us in terms of efficiency. The number of
RAIs we're looking at that carefully. We're making
sure that the scope that we're looking at, how we look
at them is the appropriate number, the appropriate
number of questions. And I think licensees are
learning also as we go through this process for what
we are interested in. And they're focusing their
submittals on the issues that we have sought through
We need to be more efficient. We've spent
a great deal of FTE on power uprates last year -- over
11, 11.5 FTE in the licensing area. That's a large
number. So we need to be better, and we're committed
to doing that, and we're going to be discussing it
MR. LEITCH: Good. Thank you.
MR. WALLIS: Anything else? We've lost
our Chairman. I'd like to hand the meeting over to
the Vice Chairman.
VICE CHAIRMAN BONACA: Okay.
MR. WALLIS: Thank you very much.
VICE CHAIRMAN BONACA: Any other questions
from members? If not, we'll take a recess for 15
minutes. We'll actually get back again, we're kind of
late, so maybe at ten after 11.
(Whereupon, the foregoing matter went off
the record at 10:57 a.m. and went back on
the record at 11:12 a.m.)
VICE CHAIRMAN BONACA: Okay. The meeting
is called to order again. We have now the -- the
purpose of this meeting is to review the findings and
observations of the Expert Panel convened by RES to
assess the applicability of the NUREG-1465, accident
source term for light water reactors to high burnup
and MOX fuels.
Two ACRS members, Dr. Powers and Dr.
Kress, were members of this Panel. Therefore, they
will not participate in discussions on the potential
finding of the Committee, although they are not
prohibited from providing the Committee with factual
information on the subject.
The staff has not requested a letter on
this issue, in part, because the information is quite
preliminary. We are running late, so I would like to
understand how much time you think you need. I think
you have half an hour allotted for the presentation?
MR. SCHAPEROW: Yes. I've got about 16
slides, but it shouldn't take too long.
VICE CHAIRMAN BONACA: So I think we
should be able to stay within the hour that we have --
MR. SCHAPEROW: Certainly.
VICE CHAIRMAN BONACA: -- scheduled for
the presentation and questions. So with that, I'll
introduce Mr. Schaperow?
MR. SCHAPEROW: That's correct.
VICE CHAIRMAN BONACA: Okay.
MR. SCHAPEROW: Thank you for pronouncing
it like that. My name is Jason Schaperow. I'm
Project Manager for some of the agencies who do
accident research. My presentation today will cover
a research effort in the area of fission product
The objective of this research was to
assess the applicability of the revised fission
product source term to high burnup and MOX fuels. The
approach we took involved holding a series of Expert
Panel meetings. Panel membership included experts who
had developed the basis for the original revised
source term a number of years ago. At these meetings,
the experts suggested source term values for high
burnup and MOX fuel, identified source term issues and
recommended needed source term research.
The next couple of slides provides the
background for this research. First, I would like to
briefly review the revised source term. Now, the
source term is defined as the fission product release
into the containment atmosphere which is available for
release to the environment. Now, RES published the
revised source term, also known as the alternative
source term, and adopted it and called NUREG-1465 back
This revised source term is more realistic
than an earlier source term called the TID-14844
source term. The revised source term is aerosol
except for about five percent of the iodine which is
vapor. Now, the TID source term was mainly vapor.
Also, the revised source term has a four-phase
release, which is broken down as follows: Gap, early
in-vessel and ex-vessel release, which is during core
concrete interactions, and finally the late in-vessel
release from the reactor coolant system. This takes
place over several hours. The TID source term,
however, is instantaneous at the start of the
Also, the revised source term is actually
two source terms: One for a PWR and one for BWR.
There's not a lot of difference, but there are a few.
The main difference, I believe, is the release timing
for the iodine. In the BWR, the iodine release occurs
a little later as a result of the BWR's lower power
The revised source term is used in a
number of regulatory applications. In particular, the
first two release phases, basically up to the point of
lower head failure, is used for LOCA design basis
accident analysis. And I've listed here five ways in
which we've used this. It's used to assess doses for
the Exclusion Area Boundary, the Low Population Zone
and in the control room. It's used for the
containment isolation valve closure time requirements,
and in this particular use is just used as a start
time on the gap release. It's been used in a fashion
as an integrated dose of the source term. It's been
used to qualify equipment in the containment. It's
been used for post-accident shielding, sampling and
access. And, finally, it's been used to evaluate the
hydrogen generated by radiolytic decomposition of
water during an accident. And all four phases of the
source term may be used for severe accident risk
The effect of the revised source term on
licensing, as well as the risk impacts, were evaluated
in our rebaseline project a few years back. After the
rebaselining project, the staff, NRR in particular,
developed a rule to allow licensees to implement the
revised source term. Now, their baselining analyses
identified that there would be a number of safety and
cost benefits that would result from implementing the
revised source term. And as you can see here, a lot
of licensees have opted to voluntarily implement the
revised source term. So far NRR has issued license
amendments for ten plants and seven more plants in
process right now for getting their license amendment.
VICE CHAIRMAN BONACA: Most of -- I mean
all of these applications have to do with the first
two phases, right?
MR. SCHAPEROW: That's correct. They have
to do with the first two phases.
VICE CHAIRMAN BONACA: The first two
phases. Okay. So just gap release and in-vessel.
MR. SCHAPEROW: And early in-vessel.
VICE CHAIRMAN BONACA: Early in-vessel.
MR. SCHAPEROW: That's correct. The
approach we took to assess the applicability of the
revised source term for high burnup and MOX fuels
involved holding a series of Expert Panel meetings.
These meetings were held over the last six months, and
in these meetings, the Panel members were requested to
judge the applicability of each aspect of the revised
source term. If the Panel members judged a particular
aspect to not be applicable, then we would request of
them to propose an alternative. As part of this
effort, Panel members considered recent data from
international tests. They discussed physical
phenomena extensively that affect the source term and
for high burnup and MOX fuels. And also they did
quite a bit of work in the area of identifying and
prioritizing source term research.
MR. WALLIS: Was this a PIRT sort of
MR. SCHAPEROW: We didn't go through the
PIRT process. We identified phenomena and ranked
them. It was an expert elicitation, but we did --
there were extensive discussions of physical phenomena
that would affect the source term for high burnup and
This slides lists the Panel members and
the other main players in this research. And as the
Chairman mentioned, two of the ACRS members were
involved in this work.
MR. WALLIS: Kress is one of those
MR. LEITCH: Yes. He's from the country
MR. KRESS: I'm not supposed to say
anything. I've got a conflict of interest.
MR. SCHAPEROW: For the experts to assess
the applicability of the revised source term for high
burnup fuel, it was necessary to specify certain
parameters, such as how high of a burnup we are
talking about. This is the decision we made. We
decided to go ahead with a Panel assessment based on
a maximum assembly burnup of 75 gigawatt days per ton.
Currently, the maximum assembly burnup is on the order
of about 60 gigawatt days per ton. We also decided to
go ahead with the assessment based on a core average
burnup of about 50 gigawatt days per ton. For PWR,
the assessment was based on cladding made of Zirlo,
and for BWR, Zircaloy cladding.
And, finally, the assessment of fission
product release fractions, which is part of the
overall source term assessment, was based on a low
pressure scenario. Now, this minimizes RCS retention
and is the same approach that we took in developing
the original revised source term.
MR. SHACK: Explain to me the low pressure
MR. SCHAPEROW: In a low pressure
scenario, such as, let's say, a two-inch break,
because the pressure is low, and in these scenarios is
a fairly direct release path to the environment.
There's no recirculation in the system to allow
deposition. For example, in a station blackout
scenario, the system sits there for a while with water
low in the vessel. And so the steam recirculates and
fission products deposit throughout the system but in
a low pressure scenario as a whole, and it just comes
out -- goes out of the --
MR. ROSEN: Low pressure refers to low
pressure in the containment.
MR. SCHAPEROW: No, low pressure in the
MR. SHACK: So any LOCA would be a low
MR. SCHAPEROW: That's correct. Any LOCA
of a size --
MR. SHACK: A big one.
MR. SCHAPEROW: -- to open up a hole so
that the fission products could flow right out without
having to circulate through the system. A PORV type
of LOCA, where the PORV opens and closes, that would
basically keep the reactor's coolant system in tact,
and the steam would circulate the fission products and
it would deposit. So that would maximize deposition.
And the types of deposition we're talking about for a
low pressure scenario is about 50 percent of the
fission products released from the core and deposited
in the reactor coolant system. In a high pressure
scenario, it could be a lot higher.
MR. SHACK: For those first two stages,
you really do retain 50 percent of the stuff.
MR. SCHAPEROW: That's what we believe.
That's what the experts believe, excuse me. I was not
on the Panel.
MR. WALLIS: Even a large-break LOCA you
deposit 50 percent of the stuff? It gets out of the
core and deposits somewhere else in the --
MR. SCHAPEROW: I believe so.
MR. WALLIS: Where does it go?
MR. SCHAPEROW: Well, there are structures
in the reactor, there's pipe -- mainly reactor
VICE CHAIRMAN BONACA: I think much is in
aerosols too, right, inside in some other structures?
MR. WALLIS: I think maybe 50 percent is
an expert guess between zero and 100.
MR. SCHAPEROW: Well, a lot of those
calculations were actually done quite a number of
years ago with a search and code package by Jim
Gieseke who's one of our Panel members. We had, I
think, about 30 cases that were run for five different
plant designs to look at deposition. We really didn't
tackle that subject much in these Expert Panel
meetings. We really did focus in on the fuel. That's
what we're really changing here. In one case, we're
letting the burnup go a lot higher; in the other case,
we're changing to a mixed oxide fuel.
VICE CHAIRMAN BONACA: But TMI also was a
good data point, right? And it was a high pressure
scenario. I mean it was a small break, TMI?
MR. TINKLER: TMI was characteristic of
those sequences where you would get more deposition --
MR. LEITCH: Charlie, identify yourself.
VICE CHAIRMAN BONACA: And I'm saying the
deposition inside was --
MR. TINKLER: Was quite high.
VICE CHAIRMAN BONACA: -- quite high. It
was higher than 50 percent.
MR. TINKLER: Jason, if I might, I might
point out that --
MR. LEITCH: Charlie, please identify
MR. TINKLER: Charles Tinkler from RES
staff. There is some variability within large LOCAs.
The very largest LOCA, if it were a double-ended hot
leak break, for example, where it was a direct path
out of the vessel, you would get retentions of less
than 50 percent. But when this Panel considered large
LOCAs, all large LOCAs aren't double-ended hot leak
breaks. Cold leak breaks where the path is through
the steam generator or back up through the down-comer,
you get larger amounts of deposition. And not all
large LOCAs are double-end guillotine breaks. So I
think it's true to say that the Panel considered LOCAs
as a general group and thought that the 50 percent was
MR. WALLIS: But if you had a hole in the
vessel head, I think most of it would come out.
MR. TINKLER: Which would be pretty close
to a double-ended hot leak nozzle rupture too, and
there wouldn't be a great deal. You might see
retentions in those cases of maybe ten, 20, maybe 25
percent, but, like I said, they're --
MR. KRESS: You have to keep in mind that
these are source terms to be used primarily with
design basis accidents. They're not to be used for
PRA for the whole sequence of accidents. And so you
ask yourself what should be in design basis space.
Then you go from there to --
VICE CHAIRMAN BONACA: No, 1465 actually
allows you to assess variations depending on the
scenarios you're addressing, right? I mean I read it
recently and it says that the licensees can propose --
MR. KRESS: If they want to justify some
different source term --
VICE CHAIRMAN BONACA: Exactly.
MR. KRESS: -- they can --
VICE CHAIRMAN BONACA: They can do that.
So there is a condition that the scenarios for the low
pressure used here is not all bounding, it just simply
is the most likely scenario you're looking at and
you're using it.
MR. SCHAPEROW: The low pressure scenarios
were found to be just as -- about as likely as the
high pressure scenarios.
VICE CHAIRMAN BONACA: Yes.
MR. SCHAPEROW: So in NUREG 1465, they
said, "Well, geez, in that case we're going to go with
the retention of the low pressure scenario, because
VICE CHAIRMAN BONACA: It's conservative,
MR. SCHAPEROW: They tilt it towards
VICE CHAIRMAN BONACA: But it doesn't
preclude the use of less conservative approach if you
can justify it.
MR. SCHAPEROW: That's correct. Actually,
I think the regulation in the Regulatory Guide speaks
directly to that.
VICE CHAIRMAN BONACA: Exactly that, yes.
MR. SCHAPEROW: Okay. This table, taken
directly from the Panel's draft report, shows the
Panel members' recommendations for a PWR. The first
row shows the recommendations for the durations of
each release phase. For example, the Panel
recommended a gap release phase duration of 0.4 hours
while the revised source term duration, in parentheses
next to it, is 0.5 hours. The Panel's release phase
duration recommendations are about the same, or
exactly the same in some cases, as the revised source
In the cases where not all the experts
recommended the same value, the value recommended by
each expert was recorded. For example, in the second
row, the noble gas row, for the gap release you'll see
that there were four values listed there that are
ranging from 0.05 to 0.07. For the so-called volatile
groups, the noble gases, the halogens and the alkali
metals, the release fractions are about the same as
the revised source term.
MR. SHACK: Just out or curiosity, were
these differences from 1465 due strictly to the high
burnup fuel or were they revising 1465 on the fly too?
MR. SCHAPEROW: They thought about both
things, because we have recent test data. We've got
the French have run a fission product tests and the
Japanese have run a couple of fission product tests in
the last few weeks. And I'll go into that a little
bit. In the next slide, I go into a little more
detail what I thought were some of the main points
that the Panel raised.
VICE CHAIRMAN BONACA: In fact, it's an
important point. This is an important point you're
making, Bill. Probably that's the best -- biggest
lesson learned from the report is that 1465 may have
to be looked at.
MR. SHACK: See, I didn't have a chance to
read any of it, because --
VICE CHAIRMAN BONACA: Yes.
MR. SHACK: -- I've been off --
VICE CHAIRMAN BONACA: And I'm saying that
it's interesting that it went from eight groups in
1465 to 14 groups here.
MR. SCHAPEROW: Well, the experts believe
that we learned something. I think there was general
agreement that we could go ahead and break it further
down, because there is -- even into these groups,
these heavier groups, there is a range of -- I'm
sorry, originally we had noble metals group, but the
experts felt that the Molybdenum and Technetium
releases were a bit higher, and they felt that it
would be worthwhile this time to go ahead and break it
MR. WALLIS: It's interesting, when they
don't know, they like numbers like one percent or one
I mean the number one or two appears an
MR. SCHAPEROW: Yes. Well, there is a lot
of uncertainty associated with the last three groups.
The last three groups are the ones which are generally
released in the smallest amounts. We haven't focused
on them in the past, and they generally -- I don't
think that they generally have a huge influence on
dose, but --
MR. WALLIS: There's no expert who has
some data and calculation and can say it's 0.00957 or
something like that?
MR. SHACK: I'm sure his computer will say
MR. SCHAPEROW: Actually, in the original
revised source term, there was a question as to
whether we should specify more than one figure. And
we did actually go to two significant figures. For
example, the halogen release was 0.35, and they said
-- it was one of these a five but not a one or a two.
It was a 0.35 but not 0.33.
Now, this slide provides an overview of
the results of the Panel assessment for high burnup
fuel. Now, the Panel members generally expected the
physical and chemical forms to be applicable. Only
small changes in the release-phase duration and the
release fraction were expected as a result of going to
the burnups we talked about.
However, the Panel did identify some
issues that were based on recent tests that were
independent of burnup. The first issue was the
potential for enhanced Tellurium release, and I'll
talk about that in my next slide a little more. As I
just mentioned, there's also a continued uncertainty
in the releases of the heavier elements, the noble
metals, the Cerium and Lanthanum groups. Also, recent
data does suggest it may be worthwhile to subdivide
those three groups into additional groups.
Now, related issues, which the Panel
members discussed, which I'd like to talk about
briefly, were, as you heard about at this point, BWR
power uprates and BWR fuel design.
VICE CHAIRMAN BONACA: One point I would
like to make here is just simply this is very clear
for them to have -- there are lessons learned for 1465
here, burnup-independent issues. The report doesn't
really speak so clearly about that, and I think you
want, at some point, to -- the report should say
something about 1465 because there are these changes
here and they're burnup independent. So it's left a
little bit with the open question when I was reading,
so what was going to happen to 1465? Is there some
lessons learned that is going to be communicated
within this report?
MR. SHACK: Fourteen sixty-five Rev 1.
VICE CHAIRMAN BONACA: Yes.
MR. SCHAPEROW: That's a reasonable idea,
VICE CHAIRMAN BONACA: The report doesn't
say, doesn't put it this clearly.
MR. SCHAPEROW: The report is just the
results of the expert elicitation.
VICE CHAIRMAN BONACA: Understand.
MR. SCHAPEROW: Exactly. And then the
research at NRR, I will -- when this is finished we
will -- we do have a number of comments in. We're
revising the report now.
VICE CHAIRMAN BONACA: Okay.
MR. SCHAPEROW: But that is a good point.
Now I'll talk a little bit about the Tellurium issue.
With regard to the Tellurium, the revised source term
specifies an early in-vessel release of Tellurium of
five percent. This is supported by Oak Ridge tests
performed a number of years ago indicating that
Tellurium gets sequestered in the tin, and the
Zircaloy cladding is not released until a high
fraction of the cladding is oxidized. And by high
fraction, we're talking numbers about 90, 95 percent
MR. WALLIS: What do you mean by "gets
MR. SCHAPEROW: It's get bound up, bound
up with the tin.
MR. WALLIS: It gets bound up during the
accident or --
MR. KRESS: Tin Telluride tries to escape
its way through the cladding.
MR. WALLIS: As it tries to escape it gets
MR. KRESS: Yes.
MR. WALLIS: Things aren't happening too
quickly for that?
MR. KRESS: This, of course, is a
speculation because the Tellurium was found associated
with the tin in the clad in tests at Oak Ridge, and
they didn't get a lot of release of the Tellurium
which was a surprise because Tellurium is very
volatile. So it's a speculation because it was found
associated where the tin was, but there was never any
determination that it was Tin Telluride.
MR. WALLIS: You'd think if things are
happening quickly, it would just escape, it wouldn't
have enough time to get caught up with the tin.
MR. KRESS: Well, the reaction could go
pretty fast, but these things aren't as fast as you
might think, these transients.
VICE CHAIRMAN BONACA: Yes.
MR. WALLIS: It's a diffusion process.
MR. SHACK: Now, would the tendency in
modern clads to go lower tin change this at all or are
is there still so much tin?
MR. SCHAPEROW: That's one point the Panel
raised. They said, "Well, we think we need -- we'll
probably need some more research. We may need to run
some tests with -- some source term tests with
cladding that doesn't have tin in it." This is the M5
cladding if I'm not mistaken.
MR. SHACK: Well, even modern Zircaloy the
tin goes with that.
MR. SCHAPEROW: There are some more recent
tests that have been conducted in France that indicate
that the Celerium release could be larger, could be
somewhere to that iodine, on the order of about 30
percent. And so this was a contentious issue among
Panel members. We spent quite a bit of time
discussing this to see if we could get any sort of --
if any of the Panel members might agree on this, and
the answer was no.
MR. ROSEN: You've got two of your own
Panel members to get agreement.
MR. SCHAPEROW: Well, this was not a
consensus process, but we did want them to discuss it
amongst themselves to try to flesh out the issues.
MR. SHACK: Well, except for early in-
vessel, there was one rugged holdout. Everybody
seemed to line up.
VICE CHAIRMAN BONACA: I think even more
striking is the fact that over the four phases you're
showing a release of 95 percent, practically all
Tellurium being released, while in the original, in
1465, it's only about 25 percent. So that's another
big issue that says what's -- because some of the
processes by which you see the differences, like for
example, late in-vessel has to do with oxygen entry,
but that's true also for low-enriched fuel. I mean
you have -- in the phase of the accident, you have
integration and you have oxygen coming in. So there
is a big discrepancy there which is even larger than
the five percent to 30 percent. It's really 25
percent to 100 percent that has to be reconciled.
MR. SCHAPEROW: This issue was raised when
we originally developed the revised source term. If
you look back at the old document, we had a draft of
NUREG-1465 ion 1992, and three years later we had a
final, and the Celerium release went down. I think,
if I recall, it was 15 percent in the draft, and it
went down to five percent in the final. So this issue
has been hanging around for a little while, but it's
been brought to the forefront, as I said, by some of
these more recent tests that were conducted in France.
MR. WALLIS: What's the effect of higher
burnup? Is it that the fuel is more porous or
MR. SCHAPEROW: Break sizes go down,
fission products inside the pellets.
MR. WALLIS: So you'd expect more release,
MR. SCHAPEROW: Earlier, earlier. For the
volatiles, earlier. For the volatiles, things get out
anyway in either case, so we expect to kind of shift
things. The gap release phase, which ends when the
pellets start releasing fission products, so the gap
release ends a little earlier for the high burnup
I don't think I quite finished this slide.
I wanted to mention for the BWRs the Panel members
pretty much stuck with Tellurium release in the
revised source term. They felt that the Zircaloy fuel
channels would tend to limit cladding oxidation. Now,
this wasn't a fuel that had Zircaloy cladding, so
there was tin, and you also had the Zircaloy fuel
channels to limit the oxidation, because the release
doesn't occur until the oxidation gets pretty high.
There are two other source term issues
related to high burnup that I would like to mention.
One is power uprates for BWRs. We had one -- one of
our experts said he didn't think we should change
anything, he thinks it's okay the way it is, no basis
for significant effect. However, at least one other
expert said they thought things would be changed, they
thought that that flux-profile flattening associated
with the power uprates could increase the releases for
the outer assemblies.
The second issue I'd like to mention
involves BWR. Our NUREG-1465 specifies actually two
different source terms: One for BWR and one for PWR.
However, the Panel members noted that the
characteristics of the more recent BWR fuel rod
designs are closer to the PWR fuel rod
characteristics. The BWR rods have smaller pellet
diameters and thinner clads. So the Panel felt that
similar rod designs would tend to result in similar
source terms and tending to maybe not be such a big
difference between a BWR and a PWR source term.
The Panel also assessed the applicability
of the revised source term for MOX fuel. This slides
gives the condition that we used for our expert
elicitation. We assumed that we're using MOX in a
PWR, which is consistent with what has been proposed
by Duke, Cogema, Stone & Webster, and that the MOX is
distributed fairly uniformly throughout the core.
That's what I mean by about half of the core. It's
not just all bunched up around the outside or bunched
up in the middle.
The typical MOX assembly burnup, and this
is meant to represent sort of a maximum, this 42
gigawatt days per ton, the assessment was based on M5
cladding and, again, a low pressure scenario for
assessing RCS retention.
MR. SHACK: Now that's a much higher level
of MOX than DOE's proposing to use.
MR. SCHAPEROW: That's correct. They're
proposing I think it was a maximum of 40. The point
here was just to say that it's basically throughout
the core, and it's going to experience the same
temperatures that the rest of the core would. It sees
the same thermal accident, the same heat-up as all the
VICE CHAIRMAN BONACA: For that
information on MOX, I mean a lot of the elicitation
ended up with N/As because there is not sufficient
information to make -- oh, you have that. Okay.
MR. SCHAPEROW: Next slide. This slide
provides an overview of the results of the Panel
assessment for MOX. Again, physical/chemical forms
were not expected to be an issue. The release-phase
duration and the more volatile releases -- noble
gases, iodine, Cesium -- were expected to be about the
same. Same Tellurium issue as for high burnup fuel.
Some experts felt that we would have a higher
One difference, as Mario just pointed out,
from the assessment for high burnup fuel is that in
this case, for MOX, some of the experts did not
recognize release fractions for some of the groups.
In particular, the Barium group on down to the
Lanthanum group. And we don't have data, that's the
problem. Right now the only data that at least the
Panel had available was a test result for Cesium, and
the French chose not to show a scale on the y-axis.
They wanted to -- they're not ready to give us that
information yet, I guess, for whatever reason.
VICE CHAIRMAN BONACA: They don't know.
MR. KRESS: The y-axis was the fission
product release fraction.
MR. SCHAPEROW: I'm sorry. Thanks, Tom.
I just blocked out data. We generally assumed that
the top of the axis was a one, because it was Cesium,
and we have some idea that Cesium is pretty -- would
come out under those conditions.
The Panel also considered what source term
research is needed to complete the Panel
recommendations, particularly in MOX, and to confirm
the other Panel recommendations, the high burnup and
MOX source terms. In this slide, I've tried to list
-- I've listed the Panel members' recommendations for
the highest priority research.
MR. WALLIS: Isn't the most important
thing to get some data? Isn't that the most important
thing when you have almost no facts to go on? It's
all expert judgment.
MR. SCHAPEROW: I think that's -- four of
the five research items here are data. The top one is
that we have a little bit of recent data which we're
validating against right now, the PHEBUS experiments
in particular. We've got some calculations with our
severe accident codes. The other four are data.
One issue is the air ingress issue, which
needs to be addressed at some point.
VICE CHAIRMAN BONACA: The French are
doing a lot of work on fuel. I understand we are not
participating in some of them.
MR. SCHAPEROW: In the severe accident
source term area, they have two programs ongoing: the
PHEBUS program, which we are participating in and we
do have some data from. The other one is the VERCORS
VICE CHAIRMAN BONACA: That's right.
MR. SCHAPEROW: -- source term tests,
which are based on the Oak Ridge source term tests.
I understand that they had requested some of our
experts to come over and help them get started, and
those are the ones that we haven't gotten the data
from. We've asked for it and we're working with them,
VICE CHAIRMAN BONACA: We will get the
data from them.
MR. SCHAPEROW: Pardon?
VICE CHAIRMAN BONACA: We will get the
MR. WALLIS: Do they have several results
of VERCORS or is it so complicated that they just run
a couple of tests and that's it?
MR. SCHAPEROW: Oh, VERCORS is a small-
scale test on the order of a few pellets.
MR. WALLIS: They do a lot of tests,
MR. SCHAPEROW: A few of them, maybe three
MR. WALLIS: Three a year.
MR. SCHAPEROW: Basically, a take off from
what we had done at Oak Ridge.
MR. WALLIS: How do they get high burnup
MR. SCHAPEROW: I assume they either get
it from a test reactor or maybe a lead test assembly.
I'm not sure.
MR. KRESS: Some of its BR3 fuel, which is
-- some of it was high burnup. They've tested up to
65 gigawatt days per metric ton. So they weren't
going to get it out of old reactors.
MR. WALLIS: Well, I think it would be
great if you could go beyond this and sort of lay out
what needs to be learned and what needs to be done to
learn it in a more specific, detailed way. I mean is
a few tests going to do the job or not, and do you
need ten times as many tests over a bigger range or
whatever? Would someone lay out what are the
requirements for knowledge here and what needs to be
done to get it?
MR. SCHAPEROW: Well, we are thinking
about that, and it's going to depend on what burnup
levels people want to go to, for one thing. So it's
going to be application-dependent in the end. We
thought about having some sort of a larger plan, but
in the end it's --
MR. WALLIS: Isn't the time for thinking
about it over and the time to do something here?
MR. KRESS: These are kind of expensive
MR. WALLIS: Yes. But we're going to be
having high burnup fuel and MOX fuel and decisions
have to be made about it, so we need to know.
MR. KRESS: But I think the idea was to
leverage as much you can with these tests that have
already been run and are continuing to be run.
MR. WALLIS: Otherwise you will be letting
people do things and establishing criteria afterwards.
MR. KRESS: Well, we pretty much know what
needs to be done.
MR. POWERS: Tom, I don't know why you're
so concerned. I understand that high burnup fuel is
irrelevant to regulatory decisions.
MR. KRESS: That's the next presentation
after lunch. That doesn't have anything to do with
MR. WALLIS: It's high priority research
but it's unnecessary, is that it? It's irrelevant.
MR. SIEBER: Irrelevant.
MR. KRESS: That's the next presentation.
MR. SCHAPEROW: Finally, a brief status.
We got comments from the Panel members on the draft
Panel report, and we've got a bit of work to do to
revise it and get the thing into final form. We do
plan to issue a final report by June. And as we just
discussed, our feeling is that the results of the
assessment will be used to help address reactor safety
issues as they arise for most applications for high
burnup MOX fuel, which we anticipate will be used for
severance and risk assessment and other applications,
such as the ongoing vulnerability assessment. That
concludes my presentation.
MR. SIEBER: It seems to me that when you
try to redefine the source term for existing plants,
whether it's high burnup or MOX fuel, that the TID-
14844 source term was so severe that it would envelope
anything you would come up with since, right?
MR. SCHAPEROW: Well, actually, not every
aspect. Now, the chemical form, the physical/chemical
form, the vapor does tend to envelope things. The
timing not necessarily. The timing -- having
instantaneous release can cause you to do a lot of
things you really shouldn't be doing.
MR. SIEBER: Yes.
MR. SCHAPEROW: And also on the release
magnitudes, that was more of a judgment call, the 50
percent iodine release.
MR. KRESS: Actually, the TID-14844
reduced that to 25 percent.
MR. SCHAPEROW: That's correct.
MR. KRESS: So these are actually a little
more severe going into containment.
MR. SCHAPEROW: These are 30 and 40
percent for B and a P.
MR. KRESS: But also there's little
consideration of gap release in TID-14844 either.
MR. SIEBER: Would this have some generic
impact on the things like controlling dose?
MR. KRESS: Yes. In general, the new
source terms are a little less severe in terms of
things you have to do in dose in the TID-14844. So
MR. SIEBER: Okay.
VICE CHAIRMAN BONACA: I think for the
purpose of the report, which is the one addressing
burnup, I think it's very complete. Again, my only
suggestion would be although you don't want to address
1465 but to state very clearly that what you wrote in
that Slide Number 10, that a number of those lessons
learned are not independent, because that message then
will be taken once the report is issued, and it will
have to be evaluated, I think, to see if changes to
1465 should be implemented.
MR. KRESS: Yes. I think the Tellurium in
particular is significant, because it has -- there's
a lot of it in there, and it has high biological
VICE CHAIRMAN BONACA: And it goes to
MR. KRESS: Yes, it goes to iodine. And
it may go to it in a way that makes it vapor instead
VICE CHAIRMAN BONACA: Okay. Any
additional questions for Mr. Schaperow? You're not
expecting a report from the CRS at this stage.
MR. SCHAPEROW: No. This is only for the
VICE CHAIRMAN BONACA: Okay.
MR. SCHAPEROW: Only for your information.
We'll let you know of some of the fine research people
we have going on in the Research Office.
VICE CHAIRMAN BONACA: All right. If
there are no additional questions, then thank you very
much for the presentation, and the meeting is
recessed. We'll reconvene at ten minutes of one.
(Whereupon, the foregoing matter went off
the record at 11:50 a.m. and went back on
the record at 12:50 p.m.)
VICE CHAIRMAN BONACA: Back to order.
This is going to be a presentation on high burnup fuel
research and regulatory issues. Dr. Kress?
MR. KRESS: Thank you. I don't have a lot
of introductory remarks. The Committee might recall
that there was an exchange of letters to the places
that high burnup fuel research. Probably not needed
and we wrote a letter asking for some clarification
for that position, and I think this is a briefing to
tell us what's been going on in that area and to fill
us in. And I guess with that, I'll turn it over to
one of the two Ralph's.
MR. CARUSO: This is Ralph Caruso. I'm
going to start the briefing this afternoon, and Dr.
Meyer is going to finish it. I'd like to open my
presentation by, first of all, acknowledging that the
letter that we sent -- it was sent from Sam Collins to
Donnie back in January of this year. It included some
wording that we do consider to be unfortunate. The
use of the word, "irrelevant," was probably not
advisable. The Office of Nuclear Reactor Regulation
does consider that the work that's done by research is
valuable, and we do support it.
Notwithstanding that observation, there
are different types of research that are done in the
Office of Research. There is research that is
requested by the various offices, there is
confirmatory research, there is anticipatory research,
and we're here today to talk to you about one aspect
of the high burnup fuel research program. Actually,
I'm going to give you a little bit of an overview,
some background on high burnup fuel. Dr. Meyer is
going to talk to you about the program itself. I'm
going to give you a little bit of history, and I'm
going to talk about the 280 calorie per gram limit and
where we stand on that particular aspect of that in
MR. POWERS: How about the 180 calorie
gram per limit?
MR. CARUSO: I get into that as part of
this -- 170.
MR. POWERS: Hundred and seventy.
MR. CARUSO: I'd like to start with the
first slide, which is background about -- an NRC user
need request was sent to the Office of Research in
1993. At this time, the Agency was receiving a number
of requests from the vendors to increase burnup
limits, to go from numbers that were in the 30s and
the 40s at that time, up to about 60 or 62. And NRR
at that time decided to send a user need request to
Research to update a number of different regulatory
One of them was the NRC fuel performance
models. These are included in various computer codes
that are used by the Agency to perform independent
calculations of fuel behavior. In addition, there was
a request to revise some models for stored energy
during LOCAS and evaluate the impact of these models
on LOCA analyses.
We also requested research to reevaluate
some of the fuel failure thresholds that are used for
normal operations and RIAs. This is the 280 calorie
per gram limit and the associated 170 calorie per gram
limit that I'm going to talk about later on.
Nineteen ninety-six, after a bit of work
had been done by the Office of Research, a Commission
memorandum was sent that talked about some low
enthalpy fuel failures that occurred in some research
reactors. And it talked about a new complete rod
insertion issue that was becoming evident in a number
of operating plants.
In 1997, we sent another Commission
memorandum talking more about the regulatory
guidelines and licensing criteria for high burnup
fuel, talking about high enrichment, because at that
time there was some evidence that some licensees and
vendors might want to go to high enrichment. And we
were also talking about spent fuel issues, because the
higher burnup fuel is causing some difficulties with
storage and transportation.
In 1997, Research issued a research
information letter. This RIL, as it's called,
proposed some changes to the RAA criteria that were
used -- that were, and still are, contained in Reg
Guide 1.77 and in the Standard Review Plan, Section
4.2. The RIL discussed the history of some tests at
some test facilities -- CABRI and NSRR. And discussed
how the criteria could be changed in order to
accommodate this data.
Eventually, the Agency put together a
program plan in 1998 that included these revised
interim proposed limits, and laid out a larger program
for the Office of Research to perform confirmatory
research to verify and validate a number of fuel
performance models, computer codes and fuel
performance data. It also looked at transportation,
dry storage, source term, whole bunch of issues.
This program plan made it clear that the
body of the plan that the NRC Research would be done
to confirm material properties and fuel behavior for
burnups up to 62 gigawatt days per metric ton. The
body of the report -- the body of the memorandum
stressed that it would be the industry responsibility
to develop the criteria -- I'm sorry, excuse me. For
the criteria that they don't -- and the models for
burnup higher than 63 --
MR. WALLIS: Excuse me, Ralph. What was
actually the burnup which was being achieved in
reactors at that time?
MR. CARUSO: Let's see, in 1998, we had
already licensed at that point most of the fuel to 62.
MR. WALLIS: And then you were doing
confirmatory research to check that --
MR. CARUSO: Yes.
MR. WALLIS: -- you'd done the right
MR. CARUSO: That was the intent of the
Agency high burnup plan at that time, to do
confirmatory research to verify that. The decisions
that have been made were valid. The attachment to
this Agency burnup plan also included some statements
about how research might cooperate with the industry
in doing the testing and gathering some data for
burnups above 62.
MR. WALLIS: Just remind me, when you say
gigawatt days per metric ton or uranium? That means
all of the uranium?
MR. CARUSO: Okay. This is the value
that's used, and this is -- you have to be careful
about how you use it. This is a peak rod average
MR. WALLIS: This is for all the uranium?
MR. CARUSO: For the peak rod average
burnup shall not exceed 62 gigawatt days per metric
ton. If you look at each rod and you look at the peak
rod average, you take the burnup over the entire rod
and you average it so that you have an average number
for the rod.
MR. WALLIS: Yes.
MR. CARUSO: The peak rod in any core
should not exceed 62 gigawatt days per metric ton.
MR. WALLIS: That's Uranium 238 is mostly
MR. CARUSO: Metric ton -- MTU, metric ton
of heavy metal.
MR. WALLIS: So when you change -- there's
nothing here which says what's the effect of changing
in Richmond or more plutonium or anything like that at
MR. CARUSO: No, no, no.
MR. POWERS: How was 62 selected.
MR. CARUSO: Sixty-two -- you're going to
ask me why. This is getting back into history before
my time, so I'd have to reconstruct it. I don't
honestly know, because I wasn't involved in the
cutoff. It's my understanding that the industry tried
to push beyond 62, and the Agency said, "No. This is
as far as we're willing to extrapolate the data at
this point." And a conscious decision was made
sometime in the '90s to stop at 62 until data was
The RAI regulatory criteria. They come
from GDC. Their origins are in GDC 28, and I've
quoted it here. As you see, the criteria are pretty
general GDC 28. They're not allowed to have a
reactivity increase that would result in damage to the
reactor coolant boundary greater than limited local
yielding or sufficiently disturb the core at
supporting structures or other reactor coolant
pressure vessel internals to impair significantly the
capability to cool the core. That's the mother
document for determining RAI criteria.
MR. WALLIS: What does limited local
MR. CARUSO: That's the question of that
ages. That's difficult to determine. So as a result,
there are couple of surrogate acceptance criteria that
are used. We have a Standard Review Plan, Section
4.2, that talks about coolable geometry. I want to
get this first. It defines coolable geometry as,
"Retaining a rod bundle geometry with adequate coolant
channels to permit removal of decay heat." That
addresses the second part of GDC 28.
The first part of GDC 28 is addressed by
limiting the fragmentation and dispersal of molten
fuel from inside the cladding into the reactor coolant
system. And because it's very difficult to calculate
the damage to the reactor coolant pressure boundary
limited to local yielding, we use this surrogate of
making sure that you do not have a violent core
coolant interaction event. And the way we do that,
the way that it has been done in the past is by
limiting the average radial enthalpy limit of 280
calories per gram during an RIA. The calculation is
done by the vendors of a hypothetical RIA, and it's
almost always a rod ejection accident. And they
verify that the average enthalpy does not exceed this
280 calorie per gram limit.
And this 280 calorie per gram limit was
based on some experiments that were done in the SPIRT
facility back in the '60s, '70s, where they observed
that if you got enthalpies up in the 300, 325, 350
range, you got a very violent expulsion of molten fuel
and you got a very strong pressure pulse, and it was
thought that 280 calories per gram would provide
enough margin so that we didn't have to worry about
MR. KRESS: Those expert tests were done
with what burnup?
MR. CARUSO: They were done with pressure
or low burnup. We did a relatively low burnup fuel.
MR. WALLIS: Doesn't this depend on the
fuel design? Haven't fuels changed since that time?
MR. CARUSO: The fuels have changed, but
they're still basically uranium oxide. And the
concern that really arose was molten fuel. You're
talking about does the uranium oxide melt, and do you
have an interaction, a steam explosion of molten UO2
and water? So although the fuel designs have changed,
the fundamental phenomenon really is the same. You're
trying to prevent a steam explosion, and the thinking
is that if you prevent a steam explosion, therefore
you won't have to calculate the pressure pulse, and
therefore you won't have to calculate the building of
the reactor coolant pressure boundary.
MR. KRESS: And the 280 calories per gram
was sufficient -- insufficient to raise the
temperature to melt a certain fuel?
MR. CARUSO: To melt it, right. That's
what was thought at the time. Since then it appears
that the melting enthalpy may be somewhere around 260?
So this number may not be demonstrably not
MR. WALLIS: There's nothing here about
MR. CARUSO: That's correct.
MR. WALLIS: And, presumably, with a lot
of burnup the fuel is more likely to --
MR. CARUSO: I'll get to that. Well,
we'll talk about that.
So with that as a background, we look at
what came out of the CABRI and NSRR tests. The CABRI
and NSRR tests showed that fuel could fail at much
lower energies than 280 calories per gram. The SRP
actually contains a secondary failure criteria of 170
calories per gram. The 170 calorie per gram number is
used to determine when dose calculations need to be
done. There's a two-step regulatory process here.
The licensee is required to assure that the fuel will
not melt and be released into the reactor coolant
system. That's what the 280 calorie per gram number
And then if they calculate that some of
the fuel exceeds 170 calories per gram, they're
required to calculate for those pins which exceed the
170 calorie per gram limit what the dose would be, the
release from the fuel of the fission products and then
the release through the reactor coolant system and out
through any holes in the reactor coolant system and
out through the containment to members of the public.
And the standard for that is that that release should
not exceed a small fraction of the 10 CFR Part 100
limits. That's what the 170 calorie per gram limit
is. It's a no-fuel failure limit, but it's not
actually a limit, it's just a point at which you
decide to do a dose calculation, not a limit per se.
Now, we had this experience at CABRI and
NSRR where the fuel failed at low enthalpies. There
are problems with those tests, though. The NSRR tests
were done at room temperature, low pressure. The
CABRI tests were done in sodium. You can make scaling
arguments, but there were problems with the amount of
corrosion on some of the rods. In some of the tests,
there were --
MR. POWERS: Can you tell what you mean by
MR. CARUSO: Well, some of the rods that
failed had much higher levels of corrosion than we
really expect to see inside an operating PWR. There
were some rods that had spalled fuel.
MR. POWERS: But these rods came from
MR. CARUSO: They might have come from
operating reactors, but they also might have been
preconditioned. There were questions about them.
That's not really important at this point, okay,
because we know they --
MR. POWERS: But it's important enough to
put on the viewgraph.
MR. CARUSO: Well, I wanted to make it
clear that there were atypicalities about these tests.
MR. POWERS: I guess I'm struggling to
understand what's atypical.
MR. CARUSO: Well, had to do, for one
thing, the corrosion, the fact that they were in --
the tests were done in sodium or at low temperatures.
MR. WALLIS: Well, the obvious question
now is --
MR. ELTAWILA: Dana, this is Farouk
Eltawila from Research. I think the issue, and Ralph
can correct me, is that the oxidation and spoilation
it might be typical of what you have in nuclear power
plant, but during the conditioning of the specimen for
the test, they oriented all the hydride in the same
direction. So with that small pulse, it will fail.
And this preconditioning does what's typical, which is
not defeat itself.
MR. MEYER: Could I clarify this? The
concern about preconditioning, and you can call it
fabrication of the specimen from a fuel rod and
preconditioning, the concern has only been expressed
about one test rod, the one indicated up there from
CABRI, Rep NA1.
MR. POWERS: Well, let me express a
concern about all the others.
MR. MEYER: Okay.
MR. POWERS: You have a fuel rod that
you've selected in some way to extract a specimen
from, and all these tests are done with not full fuel
rods but some sections, so somebody has to cut it out.
When you send that to a lab operator and say, "Cut me
out a section or a particular length," that section is
not randomly selected; in fact, the operator operates
considerably on his own to do that. Would an operator
in a hot cell facility with production quotas on him
select a section of the rod that is as pristine as
possible to enhance his chances of getting a
MR. CARUSO: Yes. Of course that could be
done, but that's not what is done. In fact, what we
have found is that for the PWR fuel that there's a
fairly monotonic increase in the corrosion from the
bottom to the top, and the grid span next to the top
has, if not the highest level of corrosion, almost the
highest level of corrosion, and it also has a uniform
burnup over that span. And we typically will select
that span because it represents the worst condition in
We have in three cases tested an upper
grid span and a mid grid span with considerably less
corrosion and done comparative tests three different
times, once in CABRI and twice in NSRR. And in those
three cases -- in all three cases, the rods from the
upper grid span experienced cladding failure, and the
ones from the lower grid span did not. So this is a
way that we can study the dependence of this on the
MR. WALLIS: Then the real question for me
is you have some tests in SPIRT, you have some of
these tests, some of which you seem to cast doubt upon
from CABRI and NSRR. What is the status of knowledge
based on factual information from tests, the tests
MR. CARUSO: Well, the distillation of the
knowledge from those tests came out in RIL 174. At
that time, the RIL 174 made a recommendation to change
the acceptance criteria for RIAs that were in Reg
Guide 1.77 and in the Standard Review Plan, as
described on this page here. Oxide spalling would not
be allowed. Spallation was not good because it
creates weak spots in the fuel. Cladding failure
limit, the 170 calorie per gram limit, would drop to
100 calories per gram. And the coolability limit
would change from -- well, right now it's at 280
calories per gram with no burnup limit. It would
change to be 280 calories per gram for burnups less
than 30,000 megawatt days per metric ton or for
burnups greater than 30 gigawatt days per metric ton,
the criteria would be no cladding failure, i.e. 100
calories per gram. Also, is it the RIL or the -- I'm
not sure if it was the RIL or the Agency program plan
which noted that the 280 calories per gram number
might be reduced to 230 because of the evidence --
MR. WALLIS: I guess you're describing a
regulatory action. I don't know what this 100
calories per gram is based on. It may be based on the
fact that you had a very poor basis for
decisionmaking, so you did something very
conservative. Or it may be based on tremendously good
experimental basis, which may have drove you to a 100
calories per gram.
MR. CARUSO: Ralph has the paintbrush
slide here, which is -- we call it the paintbrush
MR. WALLIS: My impression is there's a
very small test basis for this decision.
MR. MEYER: There is a fairly small
database, and unfortunately when I grabbed this slide,
I didn't get the latest version of it, so there are
some missing points.
MR. ROSEN: Slide it over a bit so we can
see the --
MR. WALLIS: At least there's a scale on
MR. ROSEN: That's right.
MR. MEYER: Yes, there's a scale on the
MR. ROSEN: It should have a scale on the
MR. CARUSO: The numbers in the circles
correspond to tables in a publication. And it's a
paper that we wrote. And the indicators outside of
circles correspond to tests that have been done since
that paper was published. And there are some data
that are not on here. I know this will be
unsatisfying to people who collect good data. It is
all we have to go on, and so we resort to drawing our
lines with broad brushes. We have a better
understanding now than we had in 1977. I can tell you
something about the personality of each of these data
points and the pulse with the test temperature and
other things that we believe would make the points
either move up or down if you were able to normalize
this to a set of appropriate conditions.
The bottom line is once you get away from
uneradiated material, a new damage mechanism comes in,
and it is a mechanical interaction from the expansion
of the pellet pushing against the cladding which has
lost some of its ductility. And we plot this
typically -- we do, not everybody in the world does --
but we plot it as a function of corrosion in some
measure here, the oxide thickness, because it appears
that the oxidation on the rod gives a stronger
dependence than the actual burnup.
MR. POWERS: Well, if we move to clads
that are less corroded --
MR. MEYER: Yes.
MR. POWERS: -- in the reactor, but they
still harden in the course of irradiation, what do you
change that outside thickness to?
MR. MEYER: The irradiation hardening,
we've always thought that the irradiation hardening
hits a stable point very early, about ten gigawatt
days per ton, and you get some equilibrium where
you're annealing it as fast as you're putting it in.
And it doesn't seem to be as important as the
embrittlement that comes principally from the hydrogen
that's absorbed when you oxidize the cladding and
steam. So it's really -- there are two major
variables, burnup and -- or you could say fluency and
oxidation. We have simplified for this plot and may
simplify it in application, because I don't think
we're going to be able to resolve the dependence on
the set of variables.
MR. KRESS: If I look at that curve,
Ralph, and look at things above 40 on the oxide
MR. MEYER: Yes.
MR. KRESS: -- it looks like in order to
envelope those black dots, you need a much lower
MR. WALLIS: Everything fails pretty much.
MR. MEYER: That's right. And,
unfortunately, the points that have not been put on
this add two more right down there in that cluster.
MR. KRESS: Black dots.
MR. MEYER: Black dots. Now, here's where
you have to start looking at the test conditions,
because those are all tests in NSRR. They're tests at
room temperature, and the accident of interest is a
hot zero power accident. That's the worst one, the
one we look at. And so the temperature should be
almost 300 degrees centigrade, 285, 300 degrees.
MR. KRESS: Which makes the clad more
MR. MEYER: Which makes the clad more
ductile. In addition to that, there are different
pulse widths between these facilities. The JAERI
facility has a very narrow pulse of about four and a
half milliseconds, and the CABRI has a normal pulse of
about nine and a half milliseconds, but they have
artificially broadened it to as high as 80
milliseconds in some tests. And this affects the
temperature of the cladding during this rapid period,
the temperature of the cladding at the time that the
stress is applied.
MR. KRESS: It doesn't have time to get
the heat from inside to the clad.
MR. MEYER: Right. So if you imagine
adjustments to all of those, you take the JAERI points
and you push them up. And so we intentionally drew
our line above some of the points from NSRR.
MR. ROSEN: This pulse was compared to
what in the real case? Between four and a half and
nine is what your test facilities have shown. In the
real case, what should they be if we were actually
trying to --
MR. MEYER: That's a very interesting
question, because for years we all thought that
typical pulse widths that an LWR would produce in an
accident like this was 30 to 50 milliseconds, and in
fact last summer I asked Brookhaven, who had done an
extensive study on calculations, to go back and plot
this out as a function -- pulse width as a function of
the energy and the pulse.
And for pulses in the neighborhood of
cladding failure, that is anywhere close to 100
calories per gram, 60 to 100 calories per gram, LWR
pulses will be about ten milliseconds. And we
mistakenly thought they were much larger than that.
So at the time we drew this figure, we're thinking
that the JAERI pulses are far too narrow and that the
normal CABRI pulses are too narrow and the broadened
CABRI pulses are the right ones.
MR. CARUSO: There's some question about
whether PWRs can actually get those sort of pulses,
MR. MEYER: Well, let me respond to that
by saying we all believe, all of us who are involved
ion assessing this, believe that at the end of the day
when we get the fuel damage criteria that we're
looking for, whatever it happens to be, that when a
plant accident analysis is done for real core designs
and real conditions, that you won't get there.
MR. KRESS: Is rod ejection --
MR. MEYER: Rod ejection --
MR. ROSEN: You won't get where?
MR. MEYER: You won't get up around 100.
You'll get maybe 30, 40 calories per gram max.
MR. ROSEN: What about the pulse width?
What would the pulse width be in real plants?
MR. MEYER: This is for a real plant, and
this is several sources of data, and the difference
between them if fairly minor. So if you have a 40
calorie per gram pulse, this is in fuel enthalpy
increase. This is not actual energy of the pulse.
There's a small difference because of heat conduction.
At 40 calories per gram, the pulse width is roughly 20
MR. ROSEN: You're not answering my
question. With all due respect, Ralph, I don't think
you're answering my question.
MR. MEYER: Okay.
MR. ROSEN: It is not about experimentally
what the pulse width is that produces a maximum delta
H that you've shown here, but when a plant has, for
example, if the plant had a rod ejection accident, how
wide would the pulse be?
MR. MEYER: That's what this is. This is
a plant calculation. This is not a test result or a
MR. ROSEN: So how do I pick the pulse
width? Is it 100 or is it zero?
MR. MEYER: It depends on how much
reactivity is in the rod that gets ejected.
MR. KRESS: And where the rod is.
MR. MEYER: Yes.
MR. CARUSO: Whether the rod is inserted
or whether it's normally all the way out?
MR. MEYER: I can tell you that it would
take a reactivity of about $2 to get 100 calorie per
MR. KRESS: That means the rod's all the
way in and it's a really effective rod?
MR. MEYER: I don't have a good feeling
for it, but I'm told that's too big. That's a big
MR. KRESS: That's a big rod.
MR. MEYER: And you're not going to find
any $2 Rod Worths.
MR. KRESS: Most of them are around 50
cents, I think.
MR. MEYER: Most of them are?
MR. KRESS: Around 50 cents or something
MR. CARUSO: The rods tend to be much
lower than the values that are assumed in the accident
MR. MEYER: But I think that's -- this is
the nature of the exercise. You find out where the
damage limit is that you can tolerate, and then you do
the plant calculation and hopefully show that you
don't get to that damage limit. So we don't expect
the plants to be able to deposit the energy in the
vicinity of where we're doing the test, because we're
trying to do the test to find out what the limit of
damage is that we want to tolerate.
MR. KRESS: But the point is that when a
plant makes a calculation for its design, it's going
to calculate a number.
MR. MEYER: Yes.
MR. KRESS: And you're going to say, "We
want that number to be less than 280 or less than
MR. CARUSO: Well, actually the way the
vendors do it -- until now the vendors have all been
using 1-D methodologies. And this issue came up in
the mid-'90s. They were asked if they had any better
estimates of the actual values, because they were
using conservative 1-D methods. Using 3-D methods,
they estimated that the numbers would be well below
100. And we have this information from all of the
vendors, and this is something that Brookhaven has
also calculated. For real cores using 3-D methods,
the values will be much lower than 100.
And about a month ago, we received a
topical report from I can say Westinghouse to review
so that they could redo their calculations using a 3-D
methodology. And this is a comparison of two fuel
enthalpy calculations that they did, one using a 3-D
methodology and one using a 1-D methodology for the
limiting pin. And you can see -- you have to use the
scale on the right, not the BTUs per pound, calories
And you can see that for this limiting
fuel rod, the values are well under 100. They're in
the neighborhood of about 70. This would be for a
rod, I believe, early in life, maybe at the end of the
first cycle, sometime in the first cycle, early in the
second cycle. This is typical of the results we see
from the vendors when they use more realistic but
still conservative analyses.
MR. KRESS: So you're saying you've got
lots of margin to this 100.
MR. CARUSO: Lots of margin.
MR. KRESS: But --
MR. CARUSO: I'm getting way ahead of
MR. KRESS: Yes, but the point is if
somebody were to come in with a calculation that says
it was 99, you'd still would have used up all your
margin, but you would approve it. You'd still meet
your regulatory criteria.
MR. CARUSO: We haven't set these new
regulatory criteria yet.
MR. KRESS: Well, whatever the criteria
MR. CARUSO: And that's something that we
do have to do.
MR. KRESS: Yes.
MR. CARUSO: And we're waiting for the
results of the work that Research is doing to revise
Reg Guide 177 and the SRPs. When that work comes in,
we will revise those regulatory criteria. In the
interim, though, we have lots of licensing actions
that need to be done. This morning I talked to you
about power uprates, I've talked about PWR power
uprates. Work continues. So I can't --
MR. KRESS: I heard you say you're waiting
for the results of the research. Does that mean the
operative words in the previous slide are no longer
MR. CARUSO: No. It says that we will use
the results of the research work. I mean I can't
ignore it, I shouldn't ignore it. I will use it. I
will use it to revise the regulatory guidance. But
until that's done I still have regulatory activities
that I must continue to do. I can't just stop and
MR. WALLIS: Well, you can. I want to go
back to my first question. You have not -- I think
you've convinced me that you do not have a good basis
of test data on which to base these decisions. You've
got points which are all over the place. You don't
have a very good understanding of how fuel fails, and
this 100 calories per gram has been obtained by some
very broad brush estimate.
MR. CARUSO: Well, the 100 calorie per
gram number is the number we were going to use for
fuel failures. Remember that the GDC criteria is two
parts. GDC criteria is no threat to the reactor
coolant pressure boundary and no loss of coolable
MR. WALLIS: I don't really care what
you're going to do regulatory-wise. You haven't
convinced me you have a good basis of knowledge on
which to base your decision.
MR. CARUSO: Oh, but you see I have to
make the decision about whether I will meet the
general design criteria. The general design criteria
is the ultimate acceptance criteria, because as a
regulator that's my criteria.
MR. WALLIS: How can you do it if you
don't have a good basis of knowledge?
MR. CARUSO: Well, I do as good a job as
I can with the information that's available to me.
MR. WALLIS: Then you must have tremendous
uncertainty in your decisionmaking.
MR. CARUSO: And we do. We do have some
uncertainty, but I'm about to get into the reasons why
I sleep well at night, even given that degree of
VICE CHAIRMAN BONACA: One thing that you
said, it sounds almost as if there is new information
coming because for the first time they're doing 3-D
methods. That's not true. I mean I can remember that
combustion engineering was using a 3-D model method
seems for years, 25 years ago, Hermit, I believe, is
the name of it. I think it was a credible nodal
method. I don't know what this is. I don't know, for
example, what kind of work you're ejecting here. I
see that this is a protracted transient and typically
we have seen them turning faster now. I'm trying to
say that they've been using -- yes, Westinghouse has
been using some kind of synthesized method, they were
using 1-D and 2-D and tied them together, and they
were not really a 3-D. And so I'm trying to
understand what we've learned in the past ten years
that is so different from what we learned before.
MR. CARUSO: Well, what we've learned from
the research program is that the fuel failure limit is
not correct. It shouldn't be 170 calories per gram,
and the 280 calorie per gram limit needs to be revised
VICE CHAIRMAN BONACA: No, I was asking
about the results that the vendors are showing now.
Why are they so lower?
MR. CARUSO: Now, what the vendors are
doing, and this is going to get ahead of myself here
again, the vendors are preparing for what's called
extended burnup fuel above 62. And for burnups above
62 we've said they've got to provide the criteria,
they've got to provide the data, they've got to show
why it's safe. We're not going to do that. They've
go to do that work. Now, they have, just last
Thursday, sent in a topical report on this subject
which proposes changing the limits. And they've
proposed changing the limits to about 230 calories per
gram for the upper limit and about -- still leaving it
170 for burnups below about 35 gigawatt days per
metric ton, dropping to about 130 calories per gram at
MR. KRESS: Is this based on new data?
MR. CARUSO: They don't have any more data
than Ralph has.
MR. KRESS: Okay. So it's --
MR. WALLIS: How can they possibly justify
it, except by arm waving and theory?
MR. CARUSO: That's a good question. We
just got this report Thursday, and we have to review
MR. ROSEN: I think it would be
appropriate to read it.
MR. CARUSO: Pardon?
MR. ROSEN: I said it would be appropriate
to read it.
MR. CARUSO: Exactly. But if you -- you
were asking the question what's going on and why am I
getting this all of a sudden if the vendors already
have these methods. They want to go to higher burnup,
so they have to have better methods to go to the
higher burnup. So Westinghouse has got the jump on
the other two vendors by submitting a method here.
VICE CHAIRMAN BONACA: I just was taking
exception on their statement that until recently they
used 1-D methods and they didn't.
MR. CARUSO: What I mean by use it is in
the regulatory context, in terms of the approved
licensing methodologies, they've been using 1-D
VICE CHAIRMAN BONACA: Westinghouse has
used, not -- so, anyway.
MR. CARUSO: Okay. Let's see, where was
I? I think we got sidetracked.
MR. POWERS: Let me continue the
sidetracking a little bit.
MR. CARUSO: I'll put this one up.
MR. POWERS: What I'm struggling with a
little bit, Ralph Meyer, is you and your colleague
have critiqued what data you have based on the
experimental technique that was used. And your
critiques sound possible to me. The experiments are
not high-temperature experiments and what not. And so
you've thought, "Well, maybe I should move my criteria
in just a little bit to reflect what I think the fuel
would do if I had done the experiment correctly, I
mean an absolutely prototypic experiment." And it
sounds as though you've gotten a topical report that
comes in and says, "Okay, we can move these lines a
little more because we think this fuel will behave
even more differently if the experiment had been
Is there, within the psyche of the Agency,
any plausible argument of moving those lines around
where you set the criteria that could be accepted
without at least one experimental data point to show
that what you think the fuel would do had the
experiment been prototypically done it would in fact
MR. MEYER: Yes. In fact, since the 1997
information letter, we have not made any further
statement about how we think that -- about where we
think that line should be drawn. We have learned
enough from recent tests and from our kinetics
analysis to hone in on what we think are fairly
definitive parameters. And the one thing that we are
waiting for in order to make another estimate is a set
of tests that are now scheduled for 2004 in the NSRR
test reactor in a new high-temperature, high-pressure
capsule. So NSRR at that time is going to make a
direct comparison between the room temperature test
and a test conducted at the right temperature.
Now, they will not be able to vary the
pulse width. The pulse width will still be about five
milliseconds, and at the energies of the test the
correct pulse width should be about twice that. Now,
we do have varying pulse widths from CABRI.
MR. POWERS: Could I just hone in a little
bit on this issue of pulse width? And just tell me if
my understanding of the pulse width issue is correct.
The issue is one of how much heat do you get into the
clad, as opposed to keeping it all in the fuel? And
there must surely be a pulse width that is so narrow
that no heat goes into the clad at all. And any pulse
width really doesn't change phenomenology; is that
MR. MEYER: Yes.
MR. POWERS: And the question is can you
give us an idea of what that pulse width is such that
essentially no heat goes into the clad?
MR. MEYER: Yes. More or less, it's
around 20 milliseconds.
MR. POWERS: So it really doesn't matter
whether they have a five or not.
MR. MEYER: My opinion at the moment is
that I doubt it.
MR. POWERS: Okay.
MR. KRESS: And not only that, the
narrower the pulse width, the more conservative the
result is with respect to --
MR. MEYER: Certainly. You could say
that. There is another -- there are two effects that
are hypothesized. One of them is the temperature
effect, which we've spoken of, and it obviously
exists. How important it is we don't quite know yet.
Because in fact when you start looking at the
mechanical properties measured separately as a
function of temperature, in the range from room
temperature to 300 degrees centigrade, uniform
elongation for Zircaloy and some other alloys doesn't
show a temperature dependence there. But the total
elongation that's been measured shows some. But total
elongation is a funny property. It's not really a
materials property. It depends highly on the test
arrangement. So I don't know what to expect --
something or nothing.
There is another effect that's
hypothesized, and that has to do with a dynamic gas --
fission gas expansion that might increase the loading.
In the picture here -- I don't have a slide to
illustrate this -- but the picture here is grain
boundaries, ten micron size, roughly, which are
decorated with fission gas bubbles under high
pressure, lots of them and they're small, and a rapid
temperature transient that expands those bubbles,
forcing the grains apart and sort of acting like
levers to add to the mechanical loading on the
cladding from the thermal expansion of the O2 itself.
Now, I don't know whether that's a real effect, an
imagined effect, how important it is.
MR. WALLIS: This is just part of it. I
mean my colleague is talking about a relaxation time
for the fuel to share energy with the cladding, which
we're talking about on order of ten milliseconds.
There are all kinds of non-homogeneities in this fuel.
There are spots where there's more fuel than others.
It's not absolutely uniform. So at some microscopic
level, when you zap it very quickly, there are certain
spots that get hotter than others. There's all kinds
of things that happen microscopically in there.
MR. MEYER: That's correct.
MR. KRESS: You get more in the power
going into the --
MR. WALLIS: The little nodules of
plutonium or whatever is in there in the MOX fuel.
MR. MEYER: In high burnup UO2 fuel, I
think it's pretty homogeneous. The thing that --
where we are on the lookout for such an effect is in
the MOX fuel, which is not -- it's fabricated with
inhomogeneities which may never disappear. And so
that's a separate matter. I mean it's real. We have
a few tests on MOX fuel, and that's a real effect.
The dynamic gas expansion, I don't know if it's real
or not real, but it's possible.
MR. POWERS: I'll just sideline us just a
little more because he provokes me all the time with
these wonderful statements, things like that. Ralph,
you said that you thought in a high burnup fuel the
power input was fairly uniform?
MR. MEYER: That's what I said. Is that
MR. POWERS: It seems to me that I have
seen plots that would suggest to the contrary, that
it's highly peaked around the periphery.
MR. MEYER: Oh, oh, okay. Sure. I
thought you were talking about like little local
islands of inhomogeneous stuff.
MR. POWERS: Oh. Okay. What you're
saying is --
MR. MEYER: It's creamy smooth, but it's
got a heck of heat on the end.
MR. POWERS: On the perimeter.
MR. MEYER: Oh, yes.
MR. POWERS: But certainly uniformly
across the pellet there.
MR. MEYER: Yes.
MR. POWERS: Okay. I understand now. I'm
MR. RANSOM: I have a question. Why is
the 3-D and 1-D so much different? In fact, it seems
counterintuitive, I would think, that the 3-D might
reveal a higher new energy locally per gram than say
a 1-D energy.
MR. MEYER: I can't answer that question.
Maybe somebody --
VICE CHAIRMAN BONACA: The 1-D were never
neutronics, they were just point kinetics --
MR. RANSOM: Right. But that's the entire
core they're doing 1-D, right?
VICE CHAIRMAN BONACA: That's right. But
I'm saying --
MR. RANSOM: Versus a 1-D where you've
actually getting variations across the cross section.
VICE CHAIRMAN BONACA: Yes. But they were
using typically static calculations. And so it didn't
have all the effect of feedback that you will get in
a neutronic calculation of 3-D.
MR. RANSOM: Is that the explanation that
the feedback is much different then?
VICE CHAIRMAN BONACA: That was a key
MR. CARUSO: Let me go on to my next
slide, which is what I call "why I sleep well at
night" slide. When this issue arose from the CABRI
and NSRR tests, we talked to the vendors and they
performed some 1-D calculations or they showed us some
1-D calculations that showed that the neutronics would
be much better. The limiting fuel, the graph I showed
you for the Westinghouse plot, this is for fuel that's
less than 30 gigawatt days per metric ton for which we
think the 280 or even the 230 value is still
reasonably a good value to use.
MR. POWERS: Why do you think that?
MR. CARUSO: Well, we -- I'd have to go
back to the paintbrush plot, and if you look at the
paintbrush plot and look at burnup against failure,
you plot burnup against failure, you'll see that this
fuel at less than 30 gigawatt days per metric ton
MR. POWERS: I think that I will not see
that. If we could put the paintbrush slide up, I will
be stunned to see --
MR. CARUSO: It's not as a function of
burnup. It's a function --
MR. POWERS: No, I understand that, but we
can -- I'll be willing to make a mental change and
point to a bunch of plots at around 150 and zero and
say, gee, those look black to me.
MR. CARUSO: Do you know what those data
points are, Ralph?
MR. MEYER: Yes. There were cladding
failures in some PBF tests. Where's Harold? Help me
-- and the other SPIRT ones? Those were around five
-- Harold Scott is the Harold that I'm referring to
here, and Harold will come to a microphone and help me
recall some of the details.
MR. POWERS: Well, understand the question
that's being posed is why anyone would think a 280 or
a 230 calorie criterion is adequate for any fuel ever?
MR. CARUSO: First of all, remember that
that criteria is not for fuel failure. That's a
criteria for ejection of molten material.
MR. POWERS: I will repeat my question:
Why would anyone think that a 230 or 280 criterion is
appropriate for any fuel ever?
MR. MEYER: Okay. Let me tackle that. If
you look SPIRT and PBF data with burnups of less than
five gigawatt days per ton, so essentially zero,
essentially zero burnup, fresh fuel, some of them had
very small amounts of burnup. And there's a fairly
sizable database. And you line these up as a function
of the peak fuel enthalpy. You'll find a dividing
line around 230 calories per gram, where below 230
calories per gram you get no fuel dispersal, and above
230 calories per gram you get fuel dispersal. As soon
as you get some burnup, some significant burnup, and
the first time this shows up is with a PBF test with
a burnup of about five or six gigawatt days per ton,
you begin to see the PCI mechanism and the failure at
the much lower energies.
MR. POWERS: Okay.
MR. MEYER: It's much below 30.
MR. POWERS: I'm not sure I want to argue
with you too much about this, but if indeed seven is
your SPIRT data, I certainly see a point up there at
zero that seems to suggest you get failure at below
230. So your dividing line is a peculiar dividing
MR. MEYER: This is zero on an oxide
scale, not a burnup scale.
MR. WALLIS: But it goes down with more
MR. POWERS: Well, would you expect the
oxide to be different than about zero for zero burnup?
MR. MEYER: No, but I expect --
MR. POWERS: Well, then it's a good point.
MR. MEYER: I expect at zero burnup that
you don't have any irradiation targeting.
MR. POWERS: Okay.
MR. MEYER: It saturates somewhere around
ten or at some low value. So I do think there is
something else that is precluding the failure from
limited ductility with very fresh materials. And the
failure mechanism there is a high temperature
oxidation and embrittlement mechanism, something like
you have in --
MR. POWERS: Okay. Let me change my
question: Why would anybody accept 280 or 230 as a
criterion for any fuel with burnups greater than five
to eight gigawatt days per ton?
MR. KRESS: If you had a different plot
that says on the x-axis quantity of dispersed molten
UO2 versus enthalpy increase --
MR. MEYER: That's the important question.
MR. KRESS: -- then you're saying that
plot would -- a line drawn through 230 or something
like that would show roughly very little ejected below
it, and some above it would be ejected is what you're
saying, that the criteria for that is just how much
molten fuel gets ejected, not whether the --
MR. CARUSO: It's the molten fuel
criteria. The 230 is going to be
MR. KRESS: Not whether the clad fails or
MR. CARUSO: Not a clad failure.
MR. MEYER: It's not a clad failure, but
the 230 in fact corresponds to, for the fresh
materials, to no fuel dispersal. I think there were
probably in the whole population of tests there were
only a couple of cracks that occurred at a lower
energy, and they didn't disperse. They didn't lose
any fuel from those.
MR. KRESS: Now, if you start fuel out --
if it's running at hot shutdown, is this the test
you're talking about? So the fuel starts out
something about five or 600 at hot shutdown?
MR. CARUSO: Five or 600 what?
MR. KRESS: Degrees F.
MR. CARUSO: Hot zero power would be 500
MR. KRESS: Okay. And you add to that
temperature 230 calories per gram. Does the increase
MR. MEYER: You know exactly the total --
this is the total. Don't add them.
MR. KRESS: I can't locally put that on a
piece of fuel and say whether it takes me to molten or
MR. MEYER: Two hundred and sixty-seven
calories per gram is the solidest for fresh UO2.
MR. KRESS: It depends on what temperature
you start from.
MR. MEYER: What?
MR. KRESS: It depends on what temperature
you start from. Or are you just giving me the delta
H at the melting point to fully melt it? Is that the
delta H you're giving me?
MR. MEYER: No.
MR. KRESS: I've got to heat the fuel
first, and then I've got to melt it.
MR. MEYER: Two hundred and sixty-seven
gets you up to the solidest, and I think you chemists
do it from room temperature, don't you?
MR. KRESS: Generally, but we're starting
with 500 -- I'm trying to decide how much -- you're
giving me a pulse.
MR. MEYER: Okay.
MR. KRESS: I'm trying to decide how much
fuel I've got.
MR. MEYER: At hot conditions, 285, 300
degrees centigrade is about 18 calories per gram.
MR. KRESS: Okay. So I'm going to get
molten fuel with these pulses, and I'm going to fail
the clad. I'm trying to understand the two curves
that I see. I've got a lot of molten fuel, and I've
got a failed clad.
MR. MEYER: No, no, no, no, no. Something
is not coming across right here.
MR. KRESS: Okay.
MR. MEYER: Because the way the SPIRT data
were analyzed and the way the criterion is written,
it's a total enthalpy. You don't get to add the 18 to
that amount. In later test analysis, we have been
taking it out and just looking at the delta, because
the two main facilities --
MR. CARUSO: Operate from those
MR. MEYER: -- operate at different
MR. KRESS: So you're saying the 280 is
not a delta, it's an absolute --
MR. MEYER: Right.
MR. KRESS: -- enthalpy.
MR. MEYER: Right. Right.
MR. WALLIS: Well, I guess I've got to
drop this, but instead of talking if you'd show us a
figure which is infinitely more convincing than this
one, I would be very happy.
MR. MEYER: Well, I hope in a couple of
years when we get these what I view as key tests from
Jerry to be able to show you one that's more
convincing than this, I don't think you're going to be
happy with it, but I think it's going to be probably
the best we're going to be able to do maybe ever, but
at least for a long time.
MR. KRESS: The reason I was confused is
your y-axis says enthalpy increase. That led me into
that line of thinking.
MR. MEYER: Again, this is not the plot as
a function of burnup. This is --
MR. KRESS: That's the problem --
MR. MEYER: This doesn't have the 18
calories in this plot. Did I say it wrong before?
MR. KRESS: No, no. I was thinking wrong
MR. MEYER: This plot doesn't have. But
as Dana points out, this plot doesn't extrapolate to
zero at 230. That comes in at 150. The 230 probably
has a very limited range of applicability. I agree
with you, Dana.
MR. CARUSO: EPRI seems to think
otherwise, but we'll get a chance to look at that. I
think this is a matter that we will consider as part
of the revisions to the SRP and the Reg Guide, and we
will ask for your help and we'll ask for the help from
the Office of Research, and we'll ask for comments
from the industry in order to set those limits.
MR. KRESS: How far are we from being
MR. CARUSO: Let me just get through this,
because I want to make these points.
MR. KRESS: Okay. Okay.
MR. POWERS: Tom, just for scheduling
purposes, the next speaker will be very brief.
CHAIRMAN APOSTOLAKIS: Have you spoken to
MR. POWERS: I've had an in-depth with
CHAIRMAN APOSTOLAKIS: Okay.
MR. POWERS: And implored him to curtail
his normal exuberance.
MR. MEYER: Is that me, Dana?
MR. POWERS: No.
MR. MEYER: Oh. I thought I was the next
MR. POWERS: No. The next session.
MR. CARUSO: As I said, this is why I feel
comfortable with the plants as they are right now.
MR. POWERS: Your tolerance, sir, is
MR. CARUSO: As I said this morning,
someone has to make these decisions. And if this is
all you've got, then this is all I've got to make a
decision. These are expensive tests. I can't go get
a lot of data. I would like to have lots of data, but
lots of data costs a lot of money.
MR. KRESS: I don't see anything on here
that says the expected frequency of rod ejections is
MR. CARUSO: Well, actually, it's
contained in the third big bullet, okay?
MR. KRESS: Okay.
MR. CARUSO: Let me just talk about the
second bullet first. The fact that the paintbrush
slide, as you noticed, was plotted against corrosion.
Corrosion seems to be very important for these fuel
failures. We are going to materials -- better
materials that don't corrode as much, that don't
spall, hopefully don't spall.
But the third bullet is the important
bullet, okay, about how the machines actually operate.
And it's very important to realize that PWRs are
designed these days to operate with all rods out
during normal operation. Normally they pull all the
rods out and they don't go critical because they have
boron in them. Gradually they dilute the boron, go
critical and operate for a full cycle with all rods
out. Therefore, if you have a rod ejection accident,
there would not be any rods to eject, because they're
already out. There is no reactivity to add.
MR. WALLIS: As long as they stopped. As
long as they didn't go into like containment.
MR. SIEBER: The rods are already out.
MR. CARUSO: They're already out.
MR. WALLIS: They're not in containment.
MR. CARUSO: No. They're out of LOCA.
They're out of the core. They're sitting on --
MR. WALLIS: I thought the rod ejection
was actually a LOCA event where the rod came out and
made a hole.
MR. CARUSO: Well, it doesn't have to be,
but that's the way we would think of them these days.
In order to --
MR. ROSEN: The point is there's no
MR. CARUSO: There's no reactivity
MR. ROSEN: The reactivity has already
been added. When the PWRs are in all rods out
configuration, all the reactivity from the rods have
already been added --
MR. CARUSO: Exactly.
MR. ROSEN: -- to the core.
MR. CARUSO: Thank you, Dr. Rosen.
MR. ROSEN: There's none left.
MR. CARUSO: The analyses that have been
done are analyses of the hot zero power configuration,
okay? Hot, some rods in for some reason, zero power,
just barely critical, eject a rod, you get the highest
pulse. LWR Rod Worths these days are designed in to
be small for a number of reasons -- for safety
reasons, for economic reasons. There's all sort of
reasons rods are designed to have small Rod Worths.
And the concern here is about high burnup fuel. Well,
high burnup fuel, by definition, has been burned up.
Therefore, it has less reactivity than fresh fuel.
And, also, I would add if you look at the
number of rods in a typical core that are anywhere
near the 62 gigawatt day per ton limit, it's extremely
small, extremely small. Batch discharge averages I
think in the BWRs you heard this morning are running
about 45,000 to 50,000. That's the batch average,
which means that there are some rods that are up
around 62, but the average is a 45.
MR. POWERS: I hate to bring up the
paintbrush slide again, but I did not see anything on
that paintbrush slide that suggested there was
something magic about 62 gigawatt days per ton; that,
in fact, it was a fairly substantial degradation as
soon as you crossed -- certainly crossed 40 microns.
That seemed to be very big threshold and that there
are no pins that seemed to survive beyond that. But
even before that, it seemed to me that it was some
MR. CARUSO: We are working on this. I
think that may be a valuable observation, but realize
that 40 microns these days with new cladding materials
is actually pretty high corrosion.
MR. POWERS: Well, I also hasten to point
out that that oxide thickness was selected as the
variable on that plot because it was there, not
because it reflects on how the clad is actually the
embrittlement of the clad. Now, when you change
clads, now you've got to change whatever you're
plotting against, which is going to be something like
a measure of ductility or a measure in embrittlement
or something like that. And that when you look at
these new clads, you're going to find that they suffer
some degradation in strength as you go up in burnup.
MR. CARUSO: Possibly, that's correct. In
any case, there's going to have to be a scaling
argument made between the materials. I believe most
of these tests were done with Zircaloy. We're using
now Zirlo or using M5. BWRs use Zirc-2 which is
different than Zirc-4. So a scaling argument will
have to be made in any case.
MR. POWERS: I would be more enthusiastic
about an experimental argument.
MR. MEYER: The CABRI program is test --
its next two tests will be the Zirlo run and an M5
MR. POWERS: Didn't we -- I mean I see
papers in the literature that suggest that M5 has the
capability of picking up more hydrogen than what you'd
find is usual for the Zircaloy.
MR. CARUSO: I don't know that's the case
at the normal operating conditions. We do know of
this Russian alloy, E110 that seems to pick up a lot
of hydrogen during a high temperature LOCA-type
transient, where you're up above the Alpha-Beta phase
MR. POWERS: I see some -- I've seen at
least one paper concerning the can-do conditions,
where M5 seems to be picking up -- and it wasn't ever
specimen of M5, but some specimens of M5 seem to pick
up like twice as much as hydrogen as is normal, as
MR. CARUSO: Yes. I'm not aware of that.
MR. MEYER: I'm not aware of that either.
MR. POWERS: Maybe I should share that
paper with you.
MR. CARUSO: Okay.
MR. MEYER: Okay.
MR. POWERS: I have to find it, but it
just came to me. It's a curiosity, because it's not
every specimen of M5.
MR. MEYER: I mean we did see -- Framatome
presented last year, both here at NRC and in a public
forum, ductility measurements, these ring compression
tests, for specimens that had been oxidized under LOCA
conditions. And, in fact, the hydrogen content in
those specimens were surprisingly low.
MR. CARUSO: That's what I thought. I
thought they were showing --
MR. MEYER: Yes. Whereas the similar
rings of E110, which is the same nominal alloy, sucked
up a lot of hydrogen under very similar conditions.
This, by the way, is something that we don't
understand fully. We have -- I want to say this. We
have the full cooperation from Framatome on this. We
have signed an agreement with them to do some
cooperative research on M5 cladding at Argon under
these conditions to try and understand the situation.
MR. CARUSO: I think that's all I've got
MR. WALLIS: Ralph, did you ever mention
ATWS? Do you worry about fuel failure during an ATWS
MR. CARUSO: Fuel failures during an ATWS
MR. WALLIS: Calories per gram are used as
a criterion for an ATWS --
MR. CARUSO: ATWS criteria -- well, we
have a rule for ATWS, and then there are several
subsidiary criteria that are used to verify that the
rule is still applicable to new fuel designs or
changes in power level. And those relate to PCT,
containment issues, containment peak vessel pressure.
But for fuel it's a peak cladding temperature of 2200.
MR. POWERS: There isn't a calories per
MR. CARUSO: Lately, for certain ATWS
instability events where you have an ATWS and you've
had an instability, some calculations have been done
because they were not able to show that they met the
2200 degree limit for an unmitigated ATWS event,
unmitigated ATWS instability event. So realize the
event you're talking about you're having an ATWS --
MR. POWERS: I think when we were
listening to these power uprates, they showed us a
MR. CARUSO: Right.
MR. POWERS: -- and they talked about
calories per gram.
MR. CARUSO: Right. That's correct. That
was because they did not meet the 2200 limit.
MR. POWERS: What sort of calories per
gram were we talking about?
MR. CARUSO: Actually, I have a chart
here, and I believe the numbers are on the order of 70
or 80 calories per gram.
MR. POWERS: So it is a consideration.
MR. CARUSO: It is a consideration, but,
once again, you have to consider what the event is for
which this was calculated. This is an unmitigated
ATWS instability event.
MR. MEYER: Are those 70 or 80 numbers
MR. CARUSO: Let's see.
MR. MEYER: Because in NEDO 32047, which
was audited by NRR, I understand that the number was
250 and said to be less than 280 and therefore okay.
MR. CARUSO: This is out of any DC33006P.
This is actually out of a MELLA topical report.
Excuse me, let's see, GE14 --
MR. WALLIS: I just thought that while --
MR. CARUSO: -- 64.
MR. WALLIS: -- you say why you slept well
at night, you ought to cover the ATWS thing, that's
all. And now you're doing it.
MR. CARUSO: Sixty-four calories per gram,
MR. WALLIS: And that's okay.
MR. CARUSO: And that's okay.
MR. WALLIS: By legislative --
MR. ROSEN: Ralph Caruso, on your "sleep
at night" slide, under PWR operational practices,
something I claim to know something about, this hot
zero power case that you say is analyzed, you say
that's a reason you sleep at night. Is that because
PWRs are not at hot zero power very often?
MR. CARUSO: That's correct.
MR. ROSEN: Probably less than one percent
of the time?
MR. CARUSO: Probably much less than one
MR. ROSEN: Probably much less. I'll give
you a tenth of one percent of the time, eight hours
MR. CARUSO: Yes.
MR. ROSEN: Plants don't like to stay at
a hot zero power.
MR. CARUSO: That's correct.
MR. ROSEN: It's not a place you want to
stay. You're either shutting down and going through
it or you're going the other way as fast as you can to
get to power.
MR. CARUSO: Yes.
MR. ROSEN: Okay. So it's a probability
argument. While you're exposed in this position --
MR. CARUSO: I hesitate to make that
statement, because I'm not a PRA expert, and I can't
defend the --
MR. ROSEN: Well, we did do --
MR. CARUSO: -- probability of that.
MR. ROSEN: Well, I can make the
statement, and I think there's hardly anybody in this
room that would deny it, except perhaps -- well, I'll
just say not very many people -- that plants don't
stay at hot zero power very long.
MR. MEYER: Brookhaven did do a
probability estimate in connection with the program
plan in 1998, and they did include that small factor
in coming up with their estimate, which was in the
range of around ten to the minus six. It was at that
time where we did a similar probability estimate for
the rod drop in the BWR, concluded that it was
significantly lower than the rod ejection probability
in the PWR and at that time switched our attention
from the BWR rod drop to the BWR power oscillations.
So that's how we got onto the power oscillations in
terms of the high burnup fuels work.
VICE CHAIRMAN BONACA: I think you should
stay away from probabilities. I mean we just had a
recent even in a plant where we could have gone back
to power without realizing that there was something up
there, and you would have gone critical at zero power
MR. ROSEN: I don't see that as a reason
for not accepting the fact that plants don't stay in
VICE CHAIRMAN BONACA: I agree with you.
MR. POWERS: Let me just remind my
probablistic colleagues that at the Chernobyl Plant
there was a prescription of operating at low power,
absolutely forbidden to operate at low power. Things
that people don't like to do they sometimes do.
MR. ROSEN: What country was that in?
CHAIRMAN APOSTOLAKIS: So this Slide 6 is
going to take forever, huh?
MR. CARUSO: Slide 6, no, that's done.
That's done. Slide 7.
CHAIRMAN APOSTOLAKIS: So, excuse me,
Ralph, are you going to spend all this time on each
slide from now on?
MR. CARUSO: I don't need to spend any
time on this slide if you want to --
CHAIRMAN APOSTOLAKIS: Okay. Then you go
MR. CARUSO: Okay. The other Ralph takes
CHAIRMAN APOSTOLAKIS: The other Ralph
takes over. Okay.
MR. MEYER: I have four slides, and I only
plan to speak to the first two.
MR. POWERS: These are the slides that
you're going to discuss?
MR. MEYER: The upper half of the first
MR. POWERS: Could I ask a question,
Ralph? Will the slides that you provide us give us
some understanding of why this research is irrelevant?
MR. MEYER: I didn't understand you, Dana.
MR. POWERS: Well, one of the questions we
were trying to understand is why NRR considers the
MR. MEYER: Yes.
MR. POWERS: And I'm wondering if your
slides are going to tell us why it's irrelevant.
MR. MEYER: My slides are going to tell
you why I think what we're doing is important.
MR. CARUSO: As I explained at the very
beginning of my discussion, we consider the use of
that word to be unfortunate. And we value the work
that is done by the Office of Research, and I don't
think I personally would characterize the work as
MR. POWERS: But the fact of the matter is
that in the written documentation remains irrelevant;
is that correct?
MR. CARUSO: The document was signed, and
it's in the document system, and that's correct.
MR. KRESS: I guess the broader question
is does NRR still think there is a need for a user
need letter on this research?
MR. CARUSO: Actually, then we're going to
have to go back to the previous slide.
CHAIRMAN APOSTOLAKIS: This is the
MR. KRESS: Yes. Let's go back to the
CHAIRMAN APOSTOLAKIS: This is the
question that needs to be answered.
MR. CARUSO: The user need process in the
Agency right now evaluates -- user needs are evaluated
against these four criteria. These are the four
Agency pillars: Maintaining safety, improving
efficiency, reducing unnecessary regulatory burden and
improving public confidence. Until last Thursday, we
had no licensing actions under review which required
the results of the research --
MR. WALLIS: I'm sorry, Ralph. Do you
think your broad brush curve satisfied Criteria 4?
And if it doesn't, what are you going to do about it?
MR. CARUSO: Well, what we do is we
evaluate against all four of the criteria.
MR. POWERS: How do you do that? How do
you evaluate Number 4?
MR. CARUSO: We have decisionmakers who
sit around in a room and talk about it.
MR. POWERS: Maybe you should make your
presentation to some intelligent technically
knowledgeable members of the public, see if that
MR. CARUSO: Well, all I can say is this
is what we do. And we rank each proposed user need
against these criteria.
CHAIRMAN APOSTOLAKIS: But the criteria
are not equally weighted.
MR. CARUSO: They are equally weighted, at
least in NRR they are. NMSS, I believe, has weighting
factors for different criteria.
CHAIRMAN APOSTOLAKIS: Maintaining safety
and improving public confidence is equally weighted?
MR. CARUSO: Well, in NRR right now the
criteria are weighted equally.
CHAIRMAN APOSTOLAKIS: See, now we can
talk about it forever. I mean which public are you
talking about? But, anyway, why don't we let you go
MR. CARUSO: As I said, until last
Thursday, we had no licensing actions under review
which required the results of the research high burnup
MR. POWERS: That's the one I've never
understood on this. It seems to me that you have all
kinds of things here. You've got a Regulatory Guide
that's in desperate need of amendment. You've got a
topical report there that seems to have a fairly
interesting selection of criteria. I mean just in
your own presentation I think I counted three or four
different things that were on your plate that seemed
to address them, required information from the
MR. CARUSO: Well, this report, as I said,
arrived last Thursday. I didn't expect this report to
contain the information it does. I expected it to
contain information about burnup above 62, not below
61. And the Research Program is not aimed at burnups
above 62, it's supposed to be confirming values for
burnups below 62.
So in addition, you asked about these
regulatory criteria that desperately needed to be
revised, and I guess I would take issue with that
characterization of the need to revise the Regulatory
Guides and the SRP. We know they need to be revised.
We want good data to be provided to us, but that data
isn't going to be provided to us for at least several
more years. And in the interim, I have licensing
actions that I have to make that I cannot delay until
this information comes out, until it goes through a
public comment period, till it comes to the ACRS,
several times probably, goes to the CRGR and is
debated. I have to make a licensing decision in the
MR. WALLIS: You can turn down --
MR. KRESS: You're also going to have to
make licensing decisions later on when you could
really use that data.
MR. CARUSO: And I will. I will. I will
use that information when it eventually comes out.
I'm not saying I'm going to ignore it.
MR. KRESS: Okay. Isn't that a criteria
for a user need letter, "I'm eventually going to need
this to make better decisions?"
MR. CARUSO: I guess I'm going to go to my
bottom line right now, which is to say that the user
need program, we recognize, needs some work, and we
are in the process of revising it. And this issue
will be one of the things that will be considered as
part of the revision to the user need process.
Agencies try to work on a prioritization scheme for
user needs, how to do this in an integrated fashion
between the offices, and --
VICE CHAIRMAN BONACA: You know, you could
characterize your situation as one that says, "I have
to make decisions. Therefore, I'll make decisions
with whatever information I have. And what I have I
can use." I can understand your position, but --
MR. CARUSO: That's the position I'm in
VICE CHAIRMAN BONACA: Wait, wait. But if
I were in your shoes, I would say, "However, I don't
have enough information, and therefore I'm hardly --
I'm pressed to have this data as soon as possible."
I would feel that way, because what you presented to
us wasn't very convincing. And instead you're saying,
"I don't have enough information to do the work, but
I can live with that, and whenever the information
will come, then I will do that. And if it comes in
several years --
MR. CARUSO: I would like to have more
information, but right now we don't have it.
VICE CHAIRMAN BONACA: The reason why I'm
making a comment is that that comment is pertinent to
the recommendation to RES on whether the work they're
doing is important or urgent or whatever enough to
justify stepped up effort or slow down effort or
whatever. That's why I'm making an observation. I
mean to me, particularly on the part of the users,
depending on how you feel pressed for that information
to back up what you have, which is not much. Okay?
Then that will give some kind of impetus to the work
that RES is doing or slow it down.
MR. CARUSO: I'm not sure how much I could
speed it up. I mean the CABRI program is proceeding
at the speed it's going to proceed, and I don't think
I have any effect on whether it proceeds quickly, more
quickly or not. Can we make the CABRI program go
MR. MEYER: No.
MR. CARUSO: No.
VICE CHAIRMAN BONACA: No, but you could
kill it. I mean --
MR. ROSEN: It's not a U.S. program.
MR. CARUSO: NRR has not taken a position
that the CABRI program should be killed. We think
this is valuable research.
CHAIRMAN APOSTOLAKIS: What did you say,
Ralph, I'm sorry.
MR. CARUSO: It's valuable research.
CHAIRMAN APOSTOLAKIS: Okay.
MR. CARUSO: But then I've got to -- what
does the word "need" mean? My management is about to
shoot me. What does the word "need" mean? We don't
know. This is not a well-defined term.
CHAIRMAN APOSTOLAKIS: So the bottom line
then is what?
MR. CARUSO: The bottom line is that this
is not a --
CHAIRMAN APOSTOLAKIS: There is no user
MR. CARUSO: Under the current definition
of "user need," which we have in the office, this is
not a user need.
CHAIRMAN APOSTOLAKIS: Was it at any one
MR. CARUSO: Yes, it was.
CHAIRMAN APOSTOLAKIS: What changed since
that time? The definition of "user need" changed?
MR. CARUSO: You're asking me a policy
matter, which I can't address.
MR. HOLAHAN: I can give it a try. This
is Gary Holahan at NRR. I think the issue of user
need is a confusion factor that we're trying to work
into a better process. At the moment, user need
really means identifying who's the sponsor, who's
responsible for saying, "I want this money spent. I
want this agency money spent on this subject and not
on other subjects." At the moment, when NRR says this
is a user need, we're saying we're responsible. We
want this information, and no one else has to justify
why this program is being done.
At the moment, NRR says we have, and have
had since 1997, interim criteria which provide a
reasonable basis for meeting the general design
criteria. In fact, many people would say at least 100
conservatism between 100 calories per gram and
challenging vessel integrity or probability of the
core. And under those circumstances, we could live
with the interim criteria.
I recognize that we don't have complete
control over these programs. If the Japanese and the
French decide to shut down those test facilities and
take the interim criteria and go through the process
of public comment and all that, those will be the new
criteria for the Reg Guide and the Standard Review
Plan. We could live with that. That doesn't say
there's no value to the research. It doesn't say that
it isn't a good thing to do and that we wouldn't use
it if the data was generated.
The question is who is causing the data to
be generated. Is it because NRR has said, "I need
this information whether anyone else wants it or not"?
And until last Thursday, I don't think we could say
that, because we had an interim position for a low
probability event for which we have a very
conservative criteria, no clad failure for a ten to
the minus six event is the most conservative criteria
among accidents. What we've said is last week EPRI
and NEI sent us a new report, and when we look at that
report we'll relook at the question of what technical
support, what research program and what assistance
from the Office of Research we need in reviewing that
topical report. So each time we have a new set of
regulatory issues before us, we go back and we ask
And the question in my mind now is are we
in a position to review this topical report and the
issues that it puts on the table without additional
research? And we don't have an answer to that yet.
We just got the report. We'll look at it and we'll
reconsider. And it may be that we decide that there's
a real user need or it may be that we don't need that
and we'll review the report under some other --
MR. POWERS: Gary, you've indicated that
you can live with the interim criterion.
MR. HOLAHAN: Yes. And we have been.
MR. POWERS: And what I will point out
that based on the discussion for the last 40 minutes,
you may be very content with them, but you have a very
hard time convincing other people that those are
MR. HOLAHAN: I heard that.
MR. POWERS: So I will draw your attention
again to Mr. Wallis' point in your fourth criterion on
whether you have a user need or not.
MR. WALLIS: My impression is you have a
tremendous user need, unless there's something I
haven't heard today that this seems to be a problem
that's been going on for a long time, that decisions
have been made based on very tenuous information. Now
maybe I'm completely wrong. Maybe you've given me
completely the wrong impression, but that's the
impression that's given.
MR. POWERS: What I will point out to you,
Graham, is that this decisionmaking that went on was
presented to this Committee. This Committee has
supported it, but with the caveat that there was a
strong Agency plan supported strongly by NRR with a
user need to conduct the research to validate that.
And now that component that led to a fairly
enthusiastic endorsement of what was going on seems to
be missing here.
MR. KRESS: I think we've discussed this
a lot. Can we wrap it up pretty fast, Ralph?
MR. MEYER: Could I suggest that maybe you
just view the slides, and if you don't want additional
presentation, I'd be happy to go quickly or just not
MR. POWERS: Well, let me just ask you
this question, Ralph. Your slides are indeed fairly
explicit, but at what point -- do you have any insight
right now on what point it would be useful for a
Reactors Fuel Subcommittee to assemble and look at
your program again?
MR. MEYER: Yes. I think it's time very
soon for that. We have been doing that about once a
MR. POWERS: Right.
MR. MEYER: And we didn't schedule one
this spring. So I think we should. There have been
developments in the last year that are significant,
and it would be a good idea to do that.
MR. POWERS: Yes. I think that just
anticipating the ACRS' obligations, we are obligated
this year to produce a fairly comprehensive research
report, and it would be useful to have a meeting so
that we can prepare this section of that report. So
maybe if you guys can find a time that's convenient.
I don't want to hit you at a time when everything's
chaos and whatnot, but some convenient time maybe we
could find a mutually satisfactory time to do this,
because just looking at your slides there's a lot of
MR. MEYER: I would suggest that the
Subcommittee might also want to look at the EPRI
MR. KRESS: That's a good idea.
MR. MEYER: And I think within a few
months the staff will have time to look at it and
generate some positions, and in fact you might want to
hear from them as well.
MR. POWERS: Maybe some coordinated thing
between the two of them.
MR. MEYER: That would be a good idea.
We've had that happen before.
MR. POWERS: As long as we have the
information so that in the fall of this year we can
prepare our research report, that would be useful.
MR. SIEBER: I'd also like to ask a favor.
The three slides that you used that were graphics, if
you could make us copies and provide us a copy.
MR. CARUSO: I'll get them.
MR. SIEBER: The other thing, I noticed
that the one slide which you said came from
Westinghouse, is that proprietary?
MR. CARUSO: It's not proprietary. The
document itself is proprietary, but this page is not
MR. SIEBER: Okay.
MR. CARUSO: It doesn't have the brackets
around it that indicate proprietary. And I
specifically asked them if I could do that. It's not
MR. KRESS: I want to thank the speakers.
This was a useful exchange of views, I think. And we
appreciate you coming down. With that, I'll turn it
back to you, Mr. Chairman.
CHAIRMAN APOSTOLAKIS: Thank you. I don't
think we will need transcription for the next session.
(Whereupon, at 2:26 p.m., the ACRS meeting
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