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                Official Transcript of Proceedings

                  NUCLEAR REGULATORY COMMISSION

Title:                    132nd Advisory Committee on Nuclear Waste

Docket Number:  (not applicable)

Location:                 Rockville, Maryland

Date:                     Thursday, February 7, 2002


Work Order No.: NRC-213                                Pages 1-89




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						UNITED STATES OF AMERICA
                       NUCLEAR REGULATORY COMMISSION
                                 + + + + +
                ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW)
                                 + + + + +
                               BRIEFING ON
           STATUS OF ESTIMATING PERFORMANCE OF IGNEOUS ACTIVITY
                                 + + + + +
                                 THURSDAY
                             FEBRUARY 7, 2002
                                 + + + + +
                            ROCKVILLE, MARYLAND
                                 + + + + +
                       The Commission met in at the Nuclear
           Regulatory Commission, Two White Flint North, Room
           T2B1, 11545 Rockville Pike, at 1:30 p.m., B. John
           Garrick, Chairman, presiding.

           COMMISSIONERS PRESENT:
                 B. JOHN GARRICK, Acting Chairman
                 MILTON N. LEVENSON, Member
           .           ACNW STAFF PRESENT:
                 HOWARD J. LARSON, Special Assistant, ACRS/ACNW
                 RICHARD K. MAJOR
                 LYNN DEERING
                 ANDREW C. CAMPBELL
                 LATIF HAMDAN
                 SHER BAHADUR, Associate Director, ACRS/ACNW
                 JOHN T. LARKINS, Executive Director, ACRS/ACNW
                 AMARJIT SINGH, ACRS Staff
           ALSO PRESENT:
                 BILL HINZE, ACNW Consultant
           .                           P-R-O-C-E-E-D-I-N-G-S
                                                    (1:30 p.m.)
                       CHAIRMAN GARRICK:  Come to order.  As we
           announced this morning, my name is John Garrick,
           accompanied by Milt Levenson, another member of the
           committee, and Bill Hinze, a former member of the
           committee and consultant.  We are short a couple of
           members of the committee -- George Hornberger, the
           Chairman, for compelling reasons, and Ray Wymer, Vice
           Chairman, for other reasons -- so we're going to have
           to do the best we can.  This topic we're going to
           start off with, the member who has the lead on it
           happens to be Hornberger but, in his absence today,
           we're going to lean heavily on former member Bill
           Hinze and his distinguished knowledge about this
           topic.
                       So, with that, I think we will go ahead
           and start.  Tim, are you going to start it?
                       MR. McCARTIN:  And end it hopefully.
                       (Laughter and simultaneous discussion.)
                       MR. LARSON:  If I were introducing this
           topic, I'd say, "This is the cat, the cat that has had
           nine lives, or more".
                       MR. McCARTIN:  Thank you, Dr. Garrick.
                       (Slide)
                       Today I'll be talking about the status of
           estimating performance for igneous activity, and
           you're right in that I'm starting it.  I will give the
           entire presentation, and let me just say the reason
           for this is, what we are hoping to do today is give a
           perspective not so much in terms of the detailed
           geologic igneous processes involved, but more how
           we're representing it in the performance assessment
           and what it means in terms of its implications in
           terms of the dose.
                       We'll be talking about the differences
           between ourselves and DOE, et cetera, but today what
           we're hoping to do is talk more about how things are
           abstracted in the performance assessment and not
           really the detailed geologic processes, why I'm here
           rather than someone like Brit Hill from the Center of
           John Trapp from the staff.  And John Trapp is notable
           by his absence.  He is recovering from some recent
           surgery, which is why he's not here.  I'm sure he'd
           rather be here than recovering from surgery, that's
           for sure.
                       (Simultaneous discussion.)
                       MR. McCARTIN:  In terms of how I'm going
           to present things, it's not so much in order, but the
           topics that I'll address, and what I'm hoping to do is
           give some small insight on the uncertainties in
           estimating volcanic disruption of the repository, talk
           to differences between the NRC and DOE in our
           approaches for representing this in the performance
           assessment, talk to a path forward and, at the very
           end -- and I'll do those three topics in the context
           of the "big ticket" items for estimating the
           performance of the repository.
                       At the end, I'd like to talk briefly about
           the treatment of uncertainty in NRC's TPA code, and
           I'm going to draw parallels to what we do in igneous
           and in the waste package area.  It's the beginning of
           an effort to scope out how we're dealing with
           uncertainty in the entire code, and we hope to
           certainly pull out are there discrepancies.  We want
           to see, as Marty Virgilio talked about earlier today,
           we want to see a consistency in the way we're dealing
           with uncertainties, get a better handle on it -- it
           might get to some of the treatment of conservatism, et
           cetera -- but that's at the very end, and it's a small
           nugget.  We probably will be coming back to it maybe
           later in some subsequent meeting when we have it
           fleshed out for the entire code.
                       (Slide)
                       First, as just a general overview -- and
           this pretty much gets to what I'll be talking about --
           what are the areas of uncertainty?  Certainly, we have
           estimating the probability, and then after you get, if
           it will occur, the consequences, and there we have --
           I'll talk to five particular topic areas -- the
           interaction of magma in the repository, magma in the
           waste package, magma in the waste form, the
           redistribution of volcanic ash after the event has
           occurred, you have an ash deposit, how may it
           redistribute in time, and then, ultimately, for the
           exposure scenario, the inhalation is the dominant
           pathway.  And so I'll be talking to each one of these
           with respect to those -- the uncertainties, the
           approaches, and the path forward.
                       CHAIRMAN GARRICK:  Are there areas that we
           should have our attention called to that have gone
           through some change in the last few months?
                       MR. McCARTIN:  I'll try to address that.
           I think there have been some changes in the DOE
           program.  I certainly will be talking to things that
           we're in the process of examining and I think in the
           next six months to a year, we -- I won't guarantee
           that we have changes, but we'll have hopefully at
           least increased confidence in the approach we have if
           it doesn't change.  But I will try to talk to that as
           I go through.
                       Right now, in terms of resolutions, there
           are agreements in place for all these that we think
           the DOE will address the issues. However, one thing I
           think the staff certainly recognized that we aren't
           going to reduce all the uncertainties in any area of
           the TPA code, and uncertainty is something we need to
           live with, and we think that we want to see a
           treatment of uncertainty commensurate with its
           importance to risk, and also a recognition that
           information in the performance confirmation period
           will continue to be collected and also will shed some
           light on the uncertainty.
                       CHAIRMAN GARRICK:  The issue is not to
           eliminate the uncertainty, the issue is to quantify
           them.
                       MR. McCARTIN:  Yes, exactly.  And what you
           will see today is, really what I am trying to show is
           that what we are trying to do is get a better
           understanding of the uncertainties and possibly use
           that to refine the agreements and help in our getting
           ready to review a DOE license application.
                       (Slide)
                       With that, let me go to the first area,
           which is the probability of an igneous disruption.
           Basically, in terms of the issue, estimating the
           probability of disruption is related to how many
           volcanoes are currently there from the past, and
           looking at subsurface geologic features.  Those are
           two parts of, we believe, in estimating the
           probability.
                       In terms of the NRC approach, we're using
           the currently identified features from the past, and
           that is approximately 13 events over the past 11
           million years, and using subsurface geologic features
           to better constrain what might be the probability of
           disruption at the Yucca Mountain Repository.
                       Nevada is using a smaller subset of that.
           They are using primarily volcanoes that have occurred
           over the last million years comprising two to three
           events.  They use that in the defined particular
           zones, some narrow zones that tend to focus on the
           Repository.
                       MR. LARSON:  Is that Cole (phonetic) and
           Smith, or is it Smith and Kenno (phonetic), or who is
           it?
                       MR. McCARTIN:  With that, I'll refer to
           Brit.
                       MR. HILL:  This is Brit Hill, from the
           CNWRA.  That's the series of models from Smith, et.
           al., 1990, also a series from the Cole and Owen Smith.
                       MR. LARSON:  Does this take into account
           the recent work of Smith and his student Kenno?
                       MR. HILL:  No, it does not.
                       MR. McCARTIN:  Notably, the zones are not
           constrained by subsurface geologic features.  DOE's
           approach, they are constrained -- their probability
           probably primarily on volcanoes over the last five
           million years, that's approximately seven events.
           They just define some broad zones, some of which miss
           the Repository.
                       They also are not using geologic features
           to constrain the probability.
                       MR. LARSON:  Is that really right?  Is
           that really right?  It seems to me that DOE's approach
           does use geology in the sense that they are limiting -
           most of the source-zones are limited to crater flat,
           and also they use topography, which is certainly, in
           this area, part of the geological regime.
                       MR. HILL:  Again, this is Brit Hill, from
           the Center.  When we say the zones are not bounded by
           geologic features that localize volcanoes, we've
           addressed the technical basis on why alluvium or small
           topographic changes do not localize volcanoes, and are
           restricted solely to the crater causation.  And zones
           that are defined based on features that do not
           demonstrably localize volcanoes are the ones that are
           in many of the source-zones that bypass the
           Repository.
                       I would also point out, in the PVHA
           report, when the experts talk about how they define
           the zones, they clearly do not make a linkage to
           exclusive geologic features.
                       (Slide)
                       Now, with that, what does it mean
           quantitatively in terms of where the various groups
           are at, and the horizontal lines on the left are
           depicting the range of probabilities that were seen
           estimated by the three groups.  You can see, State of
           Nevada-sponsored work is somewhere in the 10-6 to 10-8,
           NRC is around 10-7 to 10-8, and the Department of
           energy is somewhere -- a little bit of both, 10-8 down
           to 10-10.  The Department's mean value is approximately
           1.6x10-8, which has it in that area of probability
           space where it needs to be considered in terms of the
           Yucca Mountain Repository, our probability cutoff
           being approximately 10-8.
                       CHAIRMAN GARRICK:  Now, are they all using
           the same time interval?  I thought I heard you say
           that Nevada was using a different time interval.
                       MR. McCARTIN:  Well, in terms of what are
           the relevant events that they're using to determine
           the probability, you're right.  The easiest way to put
           it, there's not an off-the-shelf thought to here's how
           you determine --
                       CHAIRMAN GARRICK:  So, these are not all
           against the same database.
                       MR. McCARTIN:  Correct.  Well, people are
           using different parts that they believe are more
           relevant, and it is a matter of opinion.  The
           Department -- and I'll let Brit add anything -- but
           the Department feels the most relevant events are
           those in the last 15 million years, and they have a
           basis for not including --
                       CHAIRMAN GARRICK:  But this is such a
           straightforward kind of question that we're asking
           here, namely, the likelihood of the event.  And it
           would seem that you would not want to sweep any
           knowledge under the rug that would shed any light on
           the frequency of that event, of the recurrence of it.
                       MR. HILL:  Brit Hill, from the Center.
           First, a minor correction.  The Department is heavily
           focused on 5 million year and younger, not 15 million
           year and younger.
                       MR. McCARTIN:  Oh, I thought you said 15.
                       MR. HILL:  I wouldn't characterize it as
           "sweeping it under the rug" or anything like that,
           except a difference of opinion by what is the most
           relevant in determining recurrence in the next million
           to 10,000 years.  Whether you are using a tighter
           range of information because of your understanding of
           process, how these were formed by the same process or
           not, or believe that only the last million years is
           the most important for the next 10,000 years --
                       CHAIRMAN GARRICK:  Of course, the
           discriminator here would preclude the need for asking
           the question would be if we saw the probability of
           distribution, we'd be able to see what the shorter
           time interval meant in terms of the uncertainties
           versus the longer time.
                       MR. HILL:  Right, in trying to gauge a
           model that's based on recurrence rates of 1 to 2
           events per million years, and you think about space
           and time, and then look at -- you're trying to focus
           on a 10,000-year interval which is so much shorter
           than anybody's recurrence rate.  I can give you a
           sense of why, for example, our position is that really
           an order of magnitude construction of probability is
           about all that's warranted because both the time
           interval, sparsity of data, and the long recurrence
           doesn't warrant a large significant figure.
                       CHAIRMAN GARRICK:  Well, the only thing is
           that if it comes down to -- if it's a 10-7 value
           that's important, and a 10-8, or whatever the line is,
           is not important, then it becomes more important to
           turn up the microscope a little bit on the different
           assumptions that are made about the input information
           for the distributions.
                       MR. HILL:  Just one final point.  It's not
           really the input assumptions that are driving this,
           it's the alternative conceptual models.  And whether
           we want to take a single tendency from a series of
           alternative conceptual models or not is not at all
           clear at this stage.
                       CHAIRMAN GARRICK:  Well, I didn't mean to
           spend so much time on it, but I just wanted --
                       MR. LARSON:  There really has been very
           little -- very few attempts at this kind of prediction
           until this problem came up, and the predictions were
           either on a very short-term basis -- an ad hoc basis
           of days, hours, months -- and the longer-term like
           we're talking about has just not been approached.  So,
           we don't have standardized procedures -- I think
           that's what Tim said, that we don't have standardized
           procedures.  And so while we're doing this job, we're
           trying to find those procedures.
                       CHAIRMAN GARRICK:  The only thing I can
           think that comes close to this is the frequency of
           occurrence of very strong motion earthquakes.
                       MR. LARSON:  Absolutely.  There's a lot of
           analogy there. In terms of short-term prediction
           versus long-term prediction, these kinds of things,
           this is the same problem, except that you have more of
           an historical record with seismicity which gives you
           a better chance of doing a decent job.  And, also, we
           understand that earthquakes are associated with
           faults.  Frankly, we have a really difficult time
           pinning down what's really happening in the mantle
           that's generating volcanic magmas.
                       Cognizant of your preamble, Tim, about not
           getting into too much detail, but also recognizing
           that you are talking about uncertainty, it strikes me,
           when I see this diagram, I can recall during the PVHA
           very lucid discussions of the NRC approach were made
           by Brit and by Chuck Connor of the Center, and John
           Trapp.  I don't know whether I attended those or not,
           it's been too long ago, but if I understand correctly
           the results here and your previous slide, the ten
           experts in volcanology that were selected by the DOE
           to run -- to be involved in this expert opinion, chose
           not to accept the approach that is being used by NRC
           today.
                       Can you understand the uncertainties that
           develop as a result of this?  Can we understand why
           they failed to accept this?  Does this cast any light
           upon the uncertainties that we see not within NRC's
           work, but between NRC and DOE?
                       MR. McCARTIN:  Well, in terms of between
           NRC and DOE, I think it's -- in terms of -- I wasn't
           involved in the PVHA either, so I don't want to talk
           to that.  I'll ask Brit to comment, if he'd like.
           But, generally, this diagram here is showing the
           variation of probability spatial based on the NRC
           approach, and you can see the Repository loosely is in
           this 10-7-10-8 range, and I think, obviously, these
           aren't very -- you see variations in these isopleths,
           and I think you're seeing the effect of structure,
           which I think is useful in terms of new information
           that could come in with the aeromagnetic data, but
           you're seeing -- and I think Brit's right, in order of
           magnitude, somewhere between 10-7 to 10-8.  From my
           standpoint, I look at the DOE current number, 1.6x10-
           8, they are in that same range -- I don't know if one
           could say we're in that big a disagreement at this
           time.  And as I said before and you indicated, there
           is no textbook on how to do this, and there is
           opinion, there is what-features-matter, et cetera, but
           I don't know if Brit has anymore of what happened at
           PVHA.
                       MR. LARSON:  I just wanted to make the
           point that -- and I do respect the NRC's approach and
           people that are doing it very much, I respect them
           very much, but I'm also struck by the fact that the
           expert elicitation seems to disregard the NRC
           approach, and I wonder where this is going to end up
           when you come to some kind of judicatio on it.
                       MR. McCARTIN:  One thing that at least I,
           from my perspective and more PA rather than --
           certainly, more PA than igneous -- but I think, as my
           next slide will allude to, we're expecting to get new
           aeromagnetic data that has been alluded, that there is
           possibly 13 more identified events in the area.
                       When I look at what I've heard and my
           limited knowledge --
                       CHAIRMAN GARRICK:  Thirteen more, did you
           say?
                       MR. McCARTIN:  Yes, potentially --
           potentially.  It's still being evaluated, but it is
           possible.  Now, remember, you've got to look at the
           time period, too.
                       MR. LARSON:  Yes, location and the timing
           is everything.
                       MR. McCARTIN:  Is key, yes.  But I think
           when that information comes in, if I had to guess,
           because of the fact that we use structure, subsurface
           geology, to help constrain these numbers, I don't
           believe the identification of those events will have
           as big of an effect on the NRC estimate as it will on
           potentially the State or DOE, and that's purely from
           my very novice opinion, and does the NRC have a more
           stable estimate because we have this other constraint
           there that allows for -- this additional information,
           depending on where it is, there are some bases.  And
           I don't know if Brit has --
                       MR. LARSON:  But there was more than just
           geological structure, I think it also had to do with
           the length of the igneous dikes that were going to be
           associated with it, and perhaps also the number, is
           that correct?  There's a difference between the NRC
           approach and the PVHA approach.
                       MR. HILL:  Again, this is Brit Hill, from
           the Center.  There are a number of questions that have
           been raised.  Going back to why the Center approach
           wasn't used, I think it's just important to clarify
           that the models that you see here that have geologic
           structure incorporated into the clustering algorithms,
           those models were not developed by the PVHA, they were
           subsequent to it.  So, this really represents our
           preferred approach was not available at the time the
           DOE conducted PVHA in 1995, so there's been a
           difference in the available models, first of all.
                       Second, to clarify on the aeromagnetic
           anomaly -- of course, that is fairly new information
           -- the U.S. Geological Survey just released until it
           could file a report, an interpretation that says that
           these anomalies that are shown on the figure in the
           labeled letters are -- can be interpreted as varying
           basalt.  It's not just the location of those features,
           but the age of those features that's going to affect
           all models, not just the State and DOE's, but it may
           affect ours as well.  All assumed occurrence rate is
           fairly uniform and doesn't cluster in time. Until we
           have a better handle on the age, it's very difficult
           to say what the effect could or could not be.  But
           taking a recurrence rate of seven volcanoes over 5
           million years to 20 volcanoes for 5 million years
           could have a significant effect on any probability
           model.
                       MR. LARSON:  Can I ask another question?
                       CHAIRMAN GARRICK:  Sure.
                       MR. LARSON:  Going to this aeromag survey
           -- and certainly it very much bears on the uncertainty
           -- has the NRC considered the number of possible
           basaltic features that might have been uncovered if
           that survey had been flown with the specifications
           appropriate for a survey designed for detecting these?
           This aeromagnetic survey was conducted to map
           hydrologic features.  It was flown in a direction in
           which you cannot adequately map dipolar features that
           are small -- and I've written to you about that in a
           report -- and, also, if this is so important to
           determining the igneous concerns, why isn't this
           magnetic survey extended into other regions, to the
           north and to the east?  There is a 300,000 year old
           volcanic feature to the northwest, off of -- called --
                       MR. HILL:  Thirsty Mesa.
                       MR. LARSON:  -- Thirsty Mesa, thank you.
           This survey doesn't go up into that area.  If this is
           so important, why aren't you pushing to get
           appropriate data to do the job?
                       MR. McCARTIN:  Once again, Brit will have
           to answer that.  However, what we're trying to do here
           is give you a sense of the differences between
           ourselves and DOE, and we certainly can go into that
           detail, but Brit is going to have to answer that
           question.
                       MR. HILL:  Well, we had looked at
           available information at the time, and thought that
           the Cain and Bracken (phonetic) survey, the existing
           aeromagnetic data, we had evaluated that and, as you
           are aware, conducted a series of ground magnetic
           investigations to look for potentially varying
           characteristics, and we felt that with the available
           information we didn't have a significant concern.  Now
           we're seeing new information from this aeromagnetic
           survey.  And I agree, it was not flown designed to
           look for these features, but it was a target that
           provided the Department a chance to mine the existing
           data and come up with new characterization
           information.  Now we have the report, and it's raising
           some very potentially significant concerns about how
           many features, varied igneous features -- it doesn't
           mean intrusive, necessarily, it could be buried
           volcanoes -- really are within an area that could
           affect our understanding of the probability.
                       MR. LARSON:  Does that open up then other
           areas for further investigation based upon what you're
           seeing here?
                       MR. HILL:  We're going to have to have
           discussion with the Department of Energy fairly soon,
           once we've had a chance to evaluate the open final
           report that came out last week, but this is the
           preliminary interpretation, which is also part of the
           technical basis impact weather report where the
           preliminary interpretations were that there were
           additional features, but they would not affect
           Department of Energy probability models.
                       MR. LARSON:  Well, if you find all these
           to the south and west of the Repository, I just wonder
           what's up there to the north and west, because we do
           have one that certainly falls within the time span of
           anyone's evaluation of the volcanic processes in the
           area.
                       MR. HILL:  We're very concerned about
           noisy terrain both adjacent to or east of the
           Repository as containing present but undetected
           igneous features.
                       CHAIRMAN GARRICK:  Tim, this is something
           -- do these numbers within these contours, say, the
           10-7 to 10-8, do they reflect your uncertainty about
           the likelihood, and is that all informational as
           opposed to modeling?
                       MR. McCARTIN:  Well, in this area,
           certainly these are related to models that the Center
           has used, and there's variation within those models.
           In terms of whether modeling uncertainty or
           uncertainty of another kind, I think Brit has to talk
           to variation there.
                       MR. HILL:  A very good answer is that the
           uncertainty in the parameters, and also alternative
           conceptual models.  It does not capture the model
           uncertainty.  We have not evaluated quantitatively the
           uncertainty in each probability model and factored
           that in as an uncertainty.
                       CHAIRMAN GARRICK:  Right, because this
           suggests a pretty high level of certainty.
                       MR. HILL:  We did not overinterpret each
           line being a solid line that's fixed to the ground.
                       CHAIRMAN GARRICK:  That's the only reason
           I asked the question, don't want to do that.
                       MR. LEVENSON:  Tim, I have a question.
           Just because somebody wrote the words down forces me
           to ask the question.  In the Center review of DOE's
           elicitation of expert opinion was criticized for what
           ten people said greater balance is needed on the panel
           to encompass a wider range of viewpoints, and also
           potential conflicts of interest.  Is the same
           criticism potentially applied to inhouse version?
           You'd probably have less than ten people.
                       MR. McCARTIN:  Well, we certainly had less
           than ten people.  That's -- I'm not sure how to answer
           that question.
                       MR. LEVENSON:  I wouldn't have raised the
           issue, but you people raised it.
                       MR. McCARTIN:  Right.  I mean, there's a
           difference in looking at DOE, what they need to do to
           provide this information.  We certainly are working to
           develop our own understanding here -- and I'll get to
           you in a second, Brit, I know he wants to add
           something here.
                       We have gone for peer review and outside
           review of what we've done.  We certainly have not done
           a separate expert elicitation.
                       MR. HILL:  We have not held our work out
           as an expert elicitation.  We put it as expert
           judgment, and we put it in peer review literature, but
           we have not tried to portray this as a consensus.
                       MR. LARSON:  Well, I don't want to come to
           anyone's defense here.  God help me, I don't want to
           do that.  But I sat in on some of the reviews of --
           for the peer reviews of the Center's work, and
           although there were problems, there was general
           consensus that this was really headed in the right
           direction.
                       In addition, when many of their
           publications came up for review, I happened to be
           editor of the Journal and they fell in my lap, and I
           don't think I've ever given anything as tight a review
           as the papers that came in from the Center.  Instead
           of having two, three reviewers, they had five or six,
           including members of the DOE staff.  So, I think that
           this has been looked at by the public and been pretty
           well received.
                       CHAIRMAN GARRICK:  Is that articulated in
           your database and in your supporting information, what
           Bill just described?
                       MR. HILL:  I'm not sure what you mean by
           supporting information.
                       CHAIRMAN GARRICK:  Well, that's pretty
           valuable evidence, it seems to me, what he just
           described.
                       MR. HILL:  It's not part of the record.
                       MR. McCARTIN:  In general, though, our
           approach has been to make sure DOE -- what information
           do they have to bring forward to support so that we
           can review their license application?
                       (Slide)
                       Continuing -- hopefully I'll be able to
           pick up the pace.
                       CHAIRMAN GARRICK:  That's not your
           problem.
                       MR. McCARTIN:  In terms of probability,
           we've pretty much discussed this quite a bit.  As I
           said, the new aeromag data is coming in.  From a risk
           standpoint, what we see now is there's an
           approximately an order of magnitude difference in the
           probability between ourselves and DOE.
                       MR. LARSON:  DOE keeps talking about their
           probability assessment as being very robust, and I
           think perhaps if we asked you, you'd say the same
           thing.
                       What's going to happen with -- let's say
           that just a few of these anomalies are volcanics that
           fall within a range of distance and time that are
           interesting.  What's this going to do to 10-7, 10-8?
           What are we worried about?  Are we so -- is this whole
           approach so fragile that finding another volcano or
           two is going to send this catapulting to an even
           higher probability?
                       MR. McCARTIN:  Well, as indicated here, if
           you ask for a best-guess at the moment, we're looking
           at a 2 to 5 times increase in probability.
                       MR. LARSON:  On the basis of 13 more
           volcanoes in their position, in their place, as you
           have them?  So you analyzed them?
                       MR. McCARTIN:  Well, what we're trying to
           do is give you where we're at today and where we think
           things may end up.  And to say -- I mean, I don't
           think we want to be held firmly to anything here, but
           trying to give you an informed estimate that's where
           we think it might end up.
                       Is that a big deal?  I think what I'd like
           to do is look at all the uncertainties we have and
           look at it from that standpoint.
                       MR. LARSON:  But, Tim, this is really the
           critical uncertainty.  The DOE oftentimes approaches
           this, and many people approach this, from the
           standpoint that you're multiplying zero times any
           number is still going to be zero, and such a low
           probability -- the probability is the backbreaker on
           this.
                       MR. McCARTIN:  Well, in one sense.  I
           don't believe that's so much the case currently, and
           for this reason, that if it was below 10-8 and now
           we're looking at a decision to whether it's considered
           or not considered and it's screened up, that's not the
           case.  Right now, DOE is, like I said, approximately
           1.6x10-8, so it's being considered.
                       And at least from my standpoint, not
           looking at whether it's probability or some other
           factor, if the estimate -- clearly, if the probability
           increases by a factor of 5, it does increase the
           overall risk by a factor of 5, but there are many
           other aspects of the calculation that have similar
           effects, either raising it or lowering it.  And so
           this is one of those factors, but if it were not in a
           position of whether it's considered or not considered
           -- and that's where I think the critical aspect was.
           Whether it's 10-8 or 10-7, I don't think is as critical
           as it's going to be considered or not going be
           considered, at least from my perspective.
                       CHAIRMAN GARRICK:  Tim, we're sorry to
           press you the way we are.
                       MR. McCARTIN:  No, no. It makes it more
           interesting for me.
                       CHAIRMAN GARRICK:  Let me ask this
           question.  Supposing that the TSPA/LA comes out with
           a much more robust analysis that shortens the time to
           the peak dose dramatically, as well as the magnitude,
           and we already see scenarios where the peak dose time
           varies from a few thousand years to a million years,
           and it is  swung dramatically by certain parameters
           and certain performance characteristics, such as
           actinide solubility and -- so, if it turns out that in
           the license application or in the analysis that's
           going on now that's a follow-on from the SSPA, that
           this dose drops down and the time at the peak dose
           shortens dramatically, does that impact the
           significance of the 10-7?
                       MR. McCARTIN:  In terms of -- you're
           saying if the base case dose shortens and --
                       CHAIRMAN GARRICK:  Yeah.  It's one thing
           to talk about recurrence of the order of 10-6, 10-7,
           when you have a situation where the worst part of the
           problem is of that same order in terms of time, but
           it's another thing when that time dramatically
           shortens as well as the magnitude of the dose.  And
           I'm just asking if the performance calculations change
           dramatically, does that change the significance of the
           recurrence interval for igneous activity?
                       MR. McCARTIN:  Well, I guess I still have
           to ask, with respect to the base case, you're saying
           that the base case scenario occurs much earlier --
                       CHAIRMAN GARRICK:  Yeah.
                       MR. McCARTIN:  -- so that there's not --
                       CHAIRMAN GARRICK:  I'm saying if they come
           forward with --
                       MR. McCARTIN:  -- would they add together
           rather than be separated in time?
                       CHAIRMAN GARRICK:  -- yeah, one in ten
           million year event, how significant is that when now
           you're talking about something of the order of 103rd
           years and a much lower peak dose?  It seems to me that
           you've got to reassess the significance of --
                       MR. McCARTIN:  I think that the
           information that DOE will give us, we'll be able to
           see what the base case results -- what the disruptive
           ones are.  The Commission will have to weigh that in
           terms of what does that mean, if these two are
           additive and now they are slightly above the standard.
                       CHAIRMAN GARRICK:  Now, picking up on
           something that Bill said earlier alluding to the fact
           that the DOE has come forward -- feels that their
           recurrence interval calculation, their probability
           calculation is very robust, and yet they have kind of
           caved in to the NRC number.  Does that make sense?
           Have they been able to -- have you been able to
           demonstrate to them that your number is comparably
           robust and that's why they chose to do this?
                       MR. McCARTIN:  Well, in this particular
           area, there is an agreement that the DOE can come
           forward with a license application with their
           probability number.
                       CHAIRMAN GARRICK:  Oh, I see.
                       MR. McCARTIN:  They have agreed to also,
           as the sensitivity analysis, to include analysis with
           the 10-7 value, to provide that additional
           information, but it's sort of a two-prong kind of
           thing.
                       CHAIRMAN GARRICK:  Okay.
                       MR. HILL:  Just perhaps one very brief
           point, the reason that we have that agreement is
           because at the staff level we had fundamental
           disagreement with the robustness of DOE analysis.
                       CHAIRMAN GARRICK:  That's what I was
           curious about.
                       MR. HILL:  In August of 2000, we had a
           technical exchange that seemed like we were really in
           a fairly impractical position on several of the
           issues, and determined that if we got the analysis as
           part of the TSPA/SR and TSPA/LA we agreed would have,
           in our view, an adequate basis at 10-7 at that time.
           That would provide us with enough information to reach
           a licensing decision, and we would not need to move
           the issue forward, but it's more that this was to
           address specific technical concerns at that time.
                       CHAIRMAN GARRICK:  See, I have a --
                       MR. HILL:  It was not a matter of we were
           just insisting on this number for some unspecified
           reason.
                       CHAIRMAN GARRICK:  Yeah.  See, I have an
           ulterior motive here.  I'm trying to extract from this
           whole process how much of it is compliance-driven and
           how much of it is risk-driven.
                       MR. McCARTIN:  In terms of the path
           forward, there's really two parts of it.  The second
           -- that last part we've talked about enough, the 10-7
           value that DOE will use, but the first part -- I think
           both ourselves and DOE will be analyzing the
           aeromagnetic data and updating estimates, and I think
           including uncertainty is a key part of that, that I
           think one of the things we'll be looking at, does it
           make sense to have a single value, or should we be
           sampling from a distribution --
                       MR. LARSON:  Does that mean that DOE will
           go beyond the report that was published this year, of
           the USGS?  Is Los Alamos continuing their work on
           this?
                       MR. McCARTIN:  Well, right now DOE, I
           think, is updating a lot of their plans and what they
           are going to accomplish, and when.  And I don't know
           if I want to try to speculate what DOE is going to do.
           I assume they will analyze this information, but in
           what time frame and how, I don't know.  We would
           expect to analyze -- to speak more for ourselves, and
           I put 2002 there -- we're going to analyze this
           information this year.  I would expect DOE to do the
           same but, like I said, they are updating their plans.
                       (Slide)
                       I finally got off probability.
                       CHAIRMAN GARRICK:  That was the easy one.
                       MR. McCARTIN:  Uh-oh, I'm in trouble.  In
           terms of getting in more now to the consequences in
           terms of the Repository magma interactions, the issue
           is one of when magma rises up and there is a drift,
           there's obviously a path there that it can take down
           the drift, and the question is one of what's going to
           happen in terms of an alternative pathway.  Rather
           than continuing straight up to the surface, the magma
           goes down the drift and breaks out at some more
           distant part, thereby intercepting more waste
           packages.  And so it has to get to how many waste
           packages are intercepted in the event.
                       Alternatively, the NRC approach, we still
           have a single vertical conduit, 1 to 10 waste packages
           are intercepted, it depends on the diameter of the
           conduit, on average 5 waste packages.  However, there
           are these numerical experiments and calculations being
           done to look at what happens when the magma hits the
           drift, and there are evaluations for that at the
           current time we are looking at it is on average.  It
           could be as high as 100 waste packages, depending on
           some assumptions in terms of how far down the draft
           things go.  But if we represented today this
           alternative, you'd be looking at approximately 100
           waste packages versus the 5.
                       DOE has a very similar approach right now
           of looking at a single conduit up through the
           Repository.  They sampled somewhere between 3 to 30
           waste packages, a median value of around 10, as part
           of this vertical conduit.  They have agreed to look at
           this alternative approach.  We haven't seen any of
           their analysis related to this, but that's part of the
           --
                       MR. LARSON:  Is the alternative approach
           only for dikes, or is it for a pipe?
                       MR. McCARTIN:  Well, if the dike comes up,
           intersects the drift, the Repository drifts, and then
           the question, where does the conduit form?  And it's
           the dike actually that's intercepting the drift, and
           could intercept multiple drifts, which is how we get
           the possibility for 100 waste packages, and it is on
           average 2 drifts are intercepted and where conduits
           form.
                       MR. LARSON:  Maybe the committee knows
           this already but, if not, just what is NRC doing in
           this area at this time, have you people learned that?
           Do you know what --
                       MR. McCARTIN:  Well, I thought in August
           Brit Hill gave a presentation to the committee in
           terms of the -- both there are numerical calculations
           going on with laboratory experiments, analog
           experiments, to try to corroborate the numerical
           calculations.  I don't know if Brit wants to add to
           that at all, but --
                       MR. HILL:  We also went over this last
           month.
                       CHAIRMAN GARRICK:  The one thing that has
           always been difficult for me to understand, and not
           being an earth scientist, it's not difficult to
           understand why I don't understand, but it's one thing
           to get these recurrence intervals on the basis of the
           kind of data we've been talking about, but what do you
           use to establish your insights on pathways and depths
           and magma flow and what have you?  Where do you get
           that information? How do you get that information?
                       MR. HILL:  There's a lot of sources of
           information.  At first, we are strongly based on an
           analog approach where we looked at similar volcanoes
           that have been recently active.  Second, on the flow
           pathways, we're taking a stronger numerical and analog
           experimentation approach because we can't go down 300
           meters and look at these sorts of conditions.  And
           it's unprecedented that ascending magma has
           intersected a horizontal void of any extent at these
           kind of depths.  We hear a lot of tubes, but they are
           very, very shallow, and so you don't have the same
           sort of depressurization and flow phenomenon that you
           would expect down at 300 meters.  That's in part why
           we've been doing a lot of the experimentation and are
           talking about this year continuing with fluid dynamic
           flow experiments to better look at this kind of a
           process at the appropriate scale for fluid containing
           a lot of gas.  But there really is a lot of
           information out there on how normal volcanoes of
           similar composition and volume and character, how the
           volcanoes erupt in nature.  We can glean an awful lot
           of the physics and fluid dynamics just by very
           straightforward observation and simplified modeling.
           And, remember, we're talking about a pressurized fluid
           intersecting an atmospheric void.
                       CHAIRMAN GARRICK:  Right.  And I guess the
           issue of backfill comes into this in a significant
           way.
                       MR. HILL:  Certainly.
                       MR. McCARTIN:  From a risk standpoint,
           obviously we are looking at an approximate order of
           magnitude, when you look at 1 to 10 waste packages, of
           up to 100 on average.
                       In terms of what's going to go on to move
           the path forward, DOE -- we're expecting them to
           analyze this scenario and come to some conclusions.
                       From NRC's standpoint, as Brit indicated,
           we are continuing with the numerical analyses in some
           of the experiments.  In September of this year, we
           expect to have some additional information on
           verification of the model and the experiments, and as
           you indicated, backfill, and that's exactly what this
           last tic is, looking at the consideration of
           Repository design in terms of how this impacts the
           number of packages that could be affected.  Backfill
           certainly has a big impact. Right now, the design is
           not to backfill the drifts, but the access tunnels, et
           cetera, would be backfilled, and that has some
           implications.
                       MR. LARSON:  Are you having any peer
           review of the work that you are currently doing,
           verifying the numerical models and the analogs, the
           laboratory analogs?
                       MR. McCARTIN:  A couple of them.  Well, I
           guess it was about two years ago we had -- well, some
           might call it a peer review, we certainly brought in
           a number of different experts in different areas to
           review what we were doing with the TPA code, and got
           review comments, et cetera -- maybe an expert review
           rather than a peer review.  And certainly the Center,
           as a group, tries to publish in a number of journals.
           NRC staff did the same thing, and so we continue to
           publish.  I don't know if there are any explicit plans
           for any specific review of a particular topic.
                       MR. HILL:  The publication is to elaborate
           very briefly.  We've been having trouble getting the
           two reports that we talked about earlier last year,
           getting those reports accepted for review because the
           topic is deemed too esoteric to appear in Geological
           Journal.  So, we have yet to receive --
                       CHAIRMAN GARRICK:  I knew these scientists
           were stuffy.
                       MR. HILL:  But we're continuing to
           resubmit to different journals that have a little more
           dynamic approach.  Of course, this has been presented
           at international meetings like the American Geological
           -- or American Geophysical meeting.
                       MR. LEVENSON:  Tim, I have a question in
           the context of trying to move toward risk-informed.
           There's a statement in the report here that "Staff
           concludes that the character of past YMR igneous
           activity represents the most conservative bounds on
           future YMR activity".  That most conservative, 1 order
           of magnitude, 3 orders of magnitude?
                       MR. McCARTIN:  I guess I'm not -- what
           report is that?
                       MR. LEVENSON:  That's the Center's report
           on --
                       CHAIRMAN GARRICK:  It was in our briefing
           book.
                       MR. LEVENSON:  -- our briefing book.  I do
           read the junk you send us.  It's Technical Basis for
           Resolution of Igneous Activity.
                       MR. McCARTIN:  I'd be happy to take that
           page down and -- I can't --
                       MR. LEVENSON:  I'm really asking a generic
           question.  I get nervous whenever people say, "Well,
           that's very conservative, so it's okay".  I mean, is
           it a factor of 2, is it a factor of 100?
                       MR. McCARTIN:  Well, partly, what I'm
           trying to do in going through this is give sort of
           where things could end up, and I will talk to that,
           but the approach we're trying to do and part of what
           this is as a result of, we're looking at the
           information that we have, what we're using to estimate
           the consequences, and how we might improve things to
           get a more realistic approach.
                       We certainly are not trying in any area of
           the TPA code to take the most conservative approach.
           I'm not -- those words trouble me, I guess, because
           it's not clear on the context --
                       MR. LEVENSON:  It isn't clear from here
           whether it's the NRC staff that did that analysis or
           what, you can't tell who did that.  This is the staff
           commenting on it.
                       MR. SINGH:  I'm not sure if that's been
           issued to -- sounds like it's still being reviewed.
                       MR. LEVENSON:  I'm sorry, go ahead.
                       (Slide)
                       MR. McCARTIN:  In terms of the magma-waste
           package interactions, clearly, when a hot magma
           interacts with a waste package, we're talking about a
           -- certainly, in the conduit, a fairly violent
           interaction.  Physically, chemically, thermally, these
           conditions are quite extreme.
                       So, the question is how does the package
           act in this environment?  In terms of the NRC, for the
           extrusive amount, the package is in the conduit.
           We're assuming the package offers no protection from
           the spent fuel from the magma.  And so it's as if
           there is no package.
                       MR. HILL:  Just to answer the previous
           question about the character of Yucca Mountain
           volcanoes conservatively, that's specifically to
           address that we do not believe that magma water
           interactions would create a different class of
           volcano, and that there is no other class of volcano
           of this composition that would give a more dispersive
           eruption, which is the process that was discussed in
           that section.  So, the past character would bound the
           dispersivity and fragmentation capability, and that
           any other -- trying to say that they're less
           dispersive would be a less conservative approach.
                       MR. McCARTIN:  In terms of the intrusive
           amount, we have on average in our code approximately
           40 waste packages failing, and just assume, once
           again, if magma contacts those waste packages, it will
           fail the container.  Part of it is due to the
           temperatures.  The magma is approximately 1100
           degrees, et cetera, and the drifts are unbackfilled.
           This really does not account, at this time, for this
           alternative flow path.  It could be more packages if
           we looked at that alternative flow path.  We have not
           worried about varying that.  We believe that's a very
           small contribution to the overall risk, and you'll see
           that actually is a slight difference between ourselves
           and DOE.
                       In terms of the DOE approach --
                       MR. LARSON:  Excuse me, Tim.  Is that then
           all taken -- enters into the biosphere through
           groundwater?
                       MR. McCARTIN:  It has that possibility,
           yes.
                       MR. LARSON:  But only --
                       MR. McCARTIN:  Only -- yes, it is
           intrusive, yes, absolutely.  For the DOE approach,
           they have a similar approach for the extrusive. Any
           waste packages in the conduit don't have any effect of
           limiting the entrainment of spent fuel in the magma.
                       In terms of the intrusive, they have a
           slightly different approach.  They have two zones.
           Zone 1 where the package offers no protection, also
           similar to ours, and in that zone right now they have
           approximately 200 waste packages. And then there is a
           Zone 2 where they have what's called some "end-cap"
           failures, some moderate failures of the waste package.
           And they have, on average, 2,000 waste packages there,
           a significant amount more.  And that is a big
           difference between ourselves and DOE.  They have far
           more -- they get a larger intrusive release than we
           do.  However, even if we increased our number of waste
           packages, we would not get, I don't believe, get to
           the numbers that DOE has, and that's something that
           you'll see in terms of the path.
                       CHAIRMAN GARRICK:  Well, what they gain on
           their probability, they lose on their consequences.
                       MR. McCARTIN:  That's one way to put it,
           for intrusive. That's the intrusive -- yes.
                       (Slide)
                       And that's part of the risk insight here.
           We understand that the intrusive is a very low
           fraction of the extrusive, and so we have not
           concentrated much effort on that particular part.
                       Conversely, DOE has the intrusive a much
           larger fraction.  Until recently, the intrusive was
           the larger dose contributor.  In the SR, intrusive was
           a larger dose than the extrusive.  That has
           flipflopped, but it is still a very high percentage of
           the extrusive.
                       CHAIRMAN GARRICK:  Now, have you seen the
           analyses that they performed where they assume these
           2,000 waste packages?
                       MR. McCARTIN:  Yes, that's the SSPA.
                       CHAIRMAN GARRICK:  So you're able to pin
           it down as to the fundamental difference between the
           NRC analysis and the DOE analysis?
                       MR. McCARTIN:  Qualitatively, I believe
           so.  I'm not convinced.  I mean, that's one of the
           things, path forward, that this last -- this year, I
           promise you, we will understand those differences.  I
           think they're -- at a very broad level, I believe
           there is approaches in terms of the release, in terms
           of their diffusional release, that when they go to
           this igneous scenario where they fail the waste
           package, I believe they give some very, very large
           diffusional releases, and that's part of it.
                       There might be some ways that they are
           using the probability to weight things that we don't
           quite understand how they are doing it.  They have a
           slightly different approach to weight the consequences
           with a probability than we do, and there are some
           other aspects to the calculation.  We are digging into
           it.  We don't have the answer.  This year, we will.
           I think part of it is we need to get a little smarter,
           look a little deeper into the DOE calculations, and
           ultimately we will end up with probably an Appendix 7
           or some other type of meeting with DOE to go over,
           okay, here's how we understand your representation.
                       As you know, I've mentioned this before,
           diffusional -- one simple thing to point to is
           diffusional.  Ourselves, and DOE, for the base case,
           have approximately the same releases for completely
           different reasons.  We take no credit for cladding,
           but we have no diffusional releases.  We did an
           estimate and saw that diffusional releases were such
           a small fraction of the invective releases that we
           don't have diffusional release.
                       DOE, on the other hand, takes a lot of
           credit for cladding, and has a diffusional release
           that dominates over their invective release,
           approximately an order of magnitude, and I think we --
                       CHAIRMAN GARRICK:  Particularly for long-
           term effects.
                       MR. McCARTIN:  Yes.  And in the situation
           for volcanism in the intrusive, I believe for those
           200 waste packages they take no credit for cladding
           and no credit for the waste package, and so they have
           some very, very large releases.  I think that's at the
           heart of it, I'm not certain, but there's an aspect of
           taking in and understanding this better that we
           certainly are in the process of doing.  I'm very
           confident this year we will have an answer to that.
           To me, from a performance assessment standpoint,
           that's the most fun this job brings, is trying to
           uncover a mystery.  We have a mystery here we don't
           quite understand, and technically it will take a
           little bit of work, but I think that's the fun part.
                       CHAIRMAN GARRICK:  Andy.
                       MR. CAMPBELL:  Tim, are there any examples
           of magma interaction with features at all?  The reason
           I ask is, if I understand correctly, basically, once
           a waste package "fails", for all intents and purposes,
           it is not there.
                       MR. McCARTIN:  Right.
                       MR. CAMPBELL:  And you haven't talked
           about waste form interactions, but essentially you
           assume a significant fraction of the waste form
           becomes a very small particle.  Is there anything that
           can be gathered in terms of interactions with engineer
           features or wall rock interactions that can constrain
           these kinds of models?
                       MR. McCARTIN:  Certainly, there's wall
           rock interaction.  On here, we are going to try to
           look at the literature for analogous kinds of
           situations, and it's primarily the Center is going to
           be helping us, try to see are there things that we can
           draw some parallels.  It's not easy, and I don't know
           if Brit has any other ideas, but we're going to try to
           look at that in a data-poor situation and try to find
           some additional information -- I know Dick Codell is
           trying to look at are there some reactor accidents,
           like TMI, where maybe there's some information more in
           the fuel area, can you glean some information in an
           area where you have very little, but we are going to
           try to pull in information where possible.
                       MR. LEVENSON:  There is data from
           Chernobyl, both the U.S. models and the Russian models
           predicted that the molten core would certainly go
           through the floor down, and it didn't penetrate the
           floor anywhere.  The molten fuel ran for long
           distances on the top of floors, and then poured down
           through existing holes, and all of the models were
           incorrect in their projections, both U.S. models and
           Russian models.
                       MR. HILL:  To directly answer your
           question on engineering analogs, the answer is no.
           There is no experience of having a basaltic volcano or
           any volcano erupt directly through an engineered
           facility.  And, remember, we're talking about putting
           a waste package into an erupting volcano, not on top
           of a lava flow.  So, there is a long-range of
           physical, thermodynamic process that's involved in
           this, and exactly modeling what's going to happen as
           we go from highly reducing environment at temperatures
           of about 1100o C. under very high dynamic flow, the
           best I can tell you is that this starts off as a 1
           meter wide dike and reams out the wall rock on the
           order of 10s of meters in diameter, through
           overpressure-underpressure relationships, so there is
           sufficient force, sufficient work to essentially at
           times melt or disaggregate solid rock.
                       And just a clarification on some of the
           Chernobyl information, I believe the temperature for
           the fuel to become molten is about 2000o Centigrade,
           there's some very high temperature beyond what we have
           been seeing in igneous events, or well below the
           solubleness for incorporation in basalt, but we're
           dealing with, again, a process where at the point of
           initial incorporation where a highly reducing
           environment of producing these are very low, on order
           of 10-9 atmospheres, but as we go up into the erupting
           cloud, we're going -- mixing with the atmosphere very
           rapidly, at temperatures on the order of several
           hundred degrees Centigrade.  And one analogy we have
           drawn from the Chernobyl accident is a very rapid
           oxidation and formation of secondary oxide phase and
           embrittlement of fuel particles during these complex,
           rapid geochemical mixing events.  We are continuing to
           work with people like Dick Codell and other folks that
           have a much better background in waste forms to try to
           glean some things from these reactor accidents to look
           at more mechanically how would the fuel aid during an
           event, but we're dealing with very rapid changes of
           very high dynamic load on all of the waste packages
           waste forms.
                       CHAIRMAN GARRICK:  Just in that
           connection, what do you assume about the deposition of
           the radionuclide inventory in the magma, is it just
           instantly available?
                       MR. McCARTIN:  There's an incorporation
           ratio that picks it up.
                       MR. HILL:  And we're looking at a process
           of conduit-widening right now where the waste package
           is heated up for ambient conditions up to about
           magmatic temperatures, and the internal contents are
           heated as well, so we're going to have cladding
           degradation, oxidation --
                       CHAIRMAN GARRICK:  So there is a process.
                       MR. HILL:  It's process-driven, but it's
           not mechanistic because there are so many
           uncertainties about how would this feature behave.  We
           faced early on the dilemma of, well, guess, it's not
           instinct, would it be 100 percent efficient?  Probably
           not, except if I look at holes in the ground from
           volcanoes, they're 100 percent efficient in
           lightening.  But how would I get a technical basis to
           say it's 80 percent or 70 percent efficient?  How
           would I defend that?
                       CHAIRMAN GARRICK:  So it's just one of the
           many abstractions that are involved.
                       MR. HILL:  It's a complex abstraction,
           that is a simplification, but it is based on the
           unusual mass and mechanical loads that are inherent in
           this system, analogous for a reactor loci than any
           sort of storage type accident.
                       CHAIRMAN GARRICK:  Thank you.
                       (Slide)
                       MR. McCARTIN:  Going to the fuel, along
           the similar lines, but certainly once again the
           chemical/thermal aspects of the magma are going to be
           a harsh environment for the fuel.  Right now, NRC has
           a fairly simplified approach -- it's an incorporation
           ration in that particles -- in simple form, particles
           that are larger than the spent fuel particles can
           incorporate that smaller particle.
                       DOE has adopted a similar approach.
                       MR. LARSON:  Does that take into account
           the density of the -- the high density of the fuel?
                       MR. McCARTIN:  Yeah.
                       (Slide)
                       In terms of the risk insight, there's a
           lot of uncertainty here, as Brit was describing,
           exactly how is this fairly violent eruption, as its
           pushing through the conduit, interacts with the fuel.
           Certainly, you can do some further refinement, but our
           gut feeling is that the refinement would not result in
           a significant change.  Right now, 100 percent of the
           fuel is incorporated.  Is it 80 percent?  Is it 50
           percent?  You might have to do a lot of work to get a
           little more resolution on that, and we're not
           convinced you could get it down very low, but that's
           a gut feeling.  Certainly, our path forward this year,
           we're looking at refining our source-term model in
           that sense.  Once again, as was mentioned, we're going
           to try to evaluate the relevant reactor accidents
           possibly.  Maybe there's some information there that
           will help us.
                       And the bottom line is, DOE does need to
           develop a technical basis for this. This is one area
           where I know they have adopted our model.  Merely
           adopting the NRC model is not a technical basis.  Just
           because it's our model doesn't mean it's necessarily
           supportable.  The DOE needs to do some work to at
           least convince themselves that it is a reasonable
           model, not just because it's the NRC's.
                       MR. LARSON:  Are you evaluating more
           complex repositories that simply are a tube?  Are you
           assuming any distortion of the tube?  Any rock falls,
           and backfill?
                       MR. McCARTIN:  In terms of the alternative
           pathways?
                       MR. LARSON:  Right.
                       MR. McCARTIN:  Yes.  That was part of the
           repository design, you look at backfill.  But we also
           are looking at, over time, you'll have rockfall and
           accumulation of material in the drifts.
                       MR. LARSON:  If I understand the process
           here, what you would end up with is the canisters that
           are being opened up being pushed to some portion of
           the drift.  Are you evaluating the effect of that, of
           a concentration of the fuel on the thermal aspects of
           the surrounding rock?  You know, if we're going after
           a low temperature repository, we'd push all of the
           magma -- or all of the fuel into one end, we've
           changed that process.
                       MR. McCARTIN:  Yes.  The initial
           calculations were assuming empty drifts, and
           subsequent ones are looking to refine things -- and
           Brit can talk to the later work.
                       MR. HILL:  Right.  The initial scoping
           report back in 1999 talked about the possibility of
           the initial shock being sufficient to move waste
           packages.  In the Woods, et. al. paper, we've refined
           that approach with a little more added, and do not
           believe that you have either enough friction or
           velocity to move a waste package.
                       MR. LARSON:  So, a lot of simplifying
           assumptions.
                       MR. HILL:  We're not seeing things like
           moving down the drift, the waste package remains
           intact even under the range of flow conditions in the
           Woods, et. al. report.  So that was an initial model
           that turned out to be --
                       MR. LARSON:  So there will be no
           concentration of the fuel in any portion of the
           drifts?
                       MR. HILL:  Not during the initial stages
           of flow because you cannot move an intact cold waste
           package under the conditions that we currently realize
           as reasonably bounding the expected upper range of
           flow during that initial impact.
                       CHAIRMAN GARRICK:  You can't have it both
           ways.
                       MR. HILL:  Another thing is, we haven't
           looked segregated flow during sustained eruption.
           After the waste package is disaggregated, it's
           possible you could get a concentration zone between a
           low velocity and high velocity horizontal flow, but I
           don't think that's likely given the turbulence
           inherent in the system. However, we haven't analyzed
           it, but plan to analyze it in the coming year.
                       MR. LARSON:  Thank you.
                       (Slide)
                       MR. McCARTIN:  Well, we finally got out of
           the repository now.  We have an ash deposit on the
           ground, and the question is one of with this ash
           deposit at the RMEI location, how is it going to
           evolve with time?  There are really processes that
           could remove material.  There's processes that can
           bring it in from, say, flooding from the repository,
           100-year flood comes in and washes some of the ash
           from near the mountain down to the RMEI location.
                       Right now, NRC has a simplified approach.
           I have "conservative" with a question mark.  I think
           the gut reaction is that this is a conservative
           approach.  However, having criticized DOE for doing
           the same thing, what is your basis for saying it's
           conservative?  And I think we have to do more work to
           understand that.  It may very well be.
                       Right now, we're having the ash plume blow
           in the direction of the critical --
                       MR. LEVENSON:  Excuse me a minute, Tim.
           Before you get to the ash moving, what was the
           approach in deciding what the composition of the ash
           was, the ratio of plution or fission products or what
           have you, to ash.  Is this concentration of mass
           involved here?
                       MR. McCARTIN:  Well, there's the volume of
           the mass of the --
                       MR. LEVENSON:  You've got a limited number
           of containers that have failed, and a huge amount of
           ash.
                       MR. McCARTIN:  We're assuming a uniform
           mixing.  At the RMEI location, the material that's put
           down is uniform within the ash.
                       MR. LEVENSON:  And the difference in
           density of a factor of 10 doesn't give you any
           segregation at all.
                       MR. McCARTIN:  Right now, we're not
           accounting for those kinds of things.
                       MR. HILL:  Please recall that it's being
           incorporated into molten material, not adhering on a
           solid.
                       MR. CODELL:  This is Dick Codell, NRC.  We
           are working on an alternative model of the fuel ash
           incorporation where we do take density into account,
           and it may supersede the incorporation ratio model.
           In this case, the fact that the fuel is much denser
           than the ash could lead to more small dense particles,
           which may behave differently once they are thrust out
           into the atmosphere, although we don't really have an
           adequate model for dealing with that atmospheric
           transport.
                       MR. HILL:  We did do a very quick scope
           that even if we fail 10 waste packages, there still --
           with a small volume tetra eruption, you're dealing
           with .01 weight percent of high level waste in the
           total amount of the eruption.  So this is really a
           trace component in the total mass core volume of the
           eruption.
                       MR. LARSON:  But it would seem reasonable
           that you could get some stratification in terms of the
           distribution of the fuel contained tetra.  It just
           seems logical that there would be a stratification
           with the density --
                       MR. LEVENSON:  Especially at the low flow
           rates.  At the relatively low flow rates, there's not
           turbulent mixing as this goes down the drift.
                       MR. CODELL:  Well, the true is, what's
           likely to happen, though, is that the biggest ash
           particles will take the biggest fuel particles with
           them, simply because there's more of the bigger ash
           particles.  There's more mass in the bigger ash
           particles, so it's not going to change density of the
           mixture that much.  My best guess is it's a relatively
           small effect.
                       MR. LARSON:  But calculations are being
           made on this?
                       MR. CODELL:  Yes.
                       MR. LEVENSON:  Having spent a number of
           years trying to mix things to get uniformity, and
           knowing how difficult it is, I have trouble assuming
           this kind of a thing.  I mean, the flow down the tubes
           is not fast enough to push the containers, and yet
           you're assuming complete mixing of everything which is
           coming long after the containers have failed.  It
           doesn't sound like a good assumption to me.
                       MR. HILL:  Just to follow up with that,
           we're considering that we're dealing with a very
           complex gas-fluid mixture that's taking a very
           irregular geometry.  Even though we talk about
           horizontal flow, it's coming up from depth vertically
           as about 50 percent fragmented -- 50 percent gas
           volume, 50 percent magma -- both horizontally and then
           breaks and goes vertically again along something that
           starts off as a 5 meter in diameter tube, but we have
           every reason to believe that as the wall rock is
           stressed, the over- and underpressure will be plucked
           and scoured the way any other volcanic conduit is.
                       So, while we may develop a quasi-angular
           flow regime, there's going to be backpressure within
           the system and there's going to be angular collapse if
           it has any reasonable analogy to a volcanic conduit.
           Both will produce an incredible amount of churning and
           turbulence within the deposit.  So, it may not be
           uniformly turbulent with continuous incorporation, but
           for the duration of the eruption, something on the
           order of three weeks, we'd be having repeated overturn
           and convection within the system.  It would be hard to
           say that you would keep segregation throughout the
           duration of an eruption.
                       CHAIRMAN GARRICK:  Does the scouring and
           the other phenomena that's taking place have a
           significant effect on the density?
                       MR. HILL:  There may be very transient
           effects due to gas resorption during slight
           overpressuring, but that would quickly be -- it would
           only be in the change in the bulk.
                       MR. LEVENSON:  Because the wall is almost
           the same density as the magma.  It's the fuel that's
           a factor of 10.
                       MR. McCARTIN:  In addition to having the
           wind blow south to the RMEI location, the question is
           how long does that deposit persist at the RMEI
           location?  And right now we have a half-life of
           approximately 1,000 years for the persistence of that
           deposit.  That's primarily based on the fact that in
           looking at analogous deposits, that they seem to
           persist in an area for around 10,000 years.
                       CHAIRMAN GARRICK:  What do the wind rows
           look like at Yucca Mountain?
                       MR. McCARTIN:  It's quite varied, and it's
           approximately, I'll say, on the order of 30 percent of
           the time due south.  Now, the other part of this is
           that we don't account for any movement in to the
           dislocation from other parts, to the flooding, et
           cetera.  There's no remobilization.  We are merely
           subtracting.  It is a simple approach.  Like I said,
           we're actually going to try and do a fair amount of
           work this year to get a better sense of the
           reasonableness of this approach.
                       DOE has partly a similar approach.  They
           are having the wind blow due south also, however, in
           terms of how long does the deposit persist, I estimate
           a half-life of around 50 years, so it doesn't persist
           nearly as long.  And I'm trying to understand a little
           better -- they do not use the half-life concept, they
           have a different kind of approach, but between the
           erosion rates they use how thick the ash deposits are,
           I'm estimating that -- I think I'm close, but I may be
           off on that -- but you can see significantly different
           half-life than the NRC.  At the NRC, we're looking for
           a much longer lived.
                       CHAIRMAN GARRICK:  As I recall, you used
           the same erosion rate for longer periods of time as
           you did for initial periods, did you not?
                       MR. McCARTIN:  Yes.  I mean, it's a
           constant.
                       (Slide)
                       In terms of what this might mean, I think
           in terms of the redistribution, I think increasing the
           removal rate, if we went to a shorter half-life for
           the deposit, I think there could be possibly an order
           of magnitude difference.  I'm not convinced of that,
           but it could be between the DOE and the NRC approach.
                       There are a lot of other effects that need
           to be considered in that.  In terms of path forward,
           I think next year we're going to try to evaluate, if
           we take into account the local wind effects.  As you
           were saying -- Brit was indicating this could be last
           three weeks, a month.  How does this deposition look
           like with a varied wind pattern?  I think it would be
           useful to look at that.  Knowing, of course, what you
           get in one area, you take away.  Then if you spread it
           out more, you have to be a little more careful about
           the redistribution over time.  And that's why we want
           to understand, I think, better -- the risk
           significance this year is, how much does this
           redistribution really matter, and do some, obviously,
           sets giving analyses with the TPA code and see exactly
           what some of those assumptions mean.  There's a lot of
           -- one of the key things you want to be very careful
           with in any analysis, and especially the TPA code
           where there is a host of interconnecting things,
           getting much better on one aspect like, say, the wind,
           and neglecting these other things, the confounding
           sensitivities that you might create by getting very
           sophisticated in one area and not doing it in another
           area, and that's a very complex problem that's part of
           this analysis.  Certainly, I can get better in one
           area, but in terms of the overall analysis, what have
           you now done.
                       CHAIRMAN GARRICK:  Sometimes this is
           referred to as the "lamppost" syndrome.
                       MR. McCARTIN:  Absolutely, yes.
                       MR. LARSON:  At what depth do you no
           longer consider the radioactivity?  You get an
           accumulation.  What is the maximum depth of
           consideration?
                       MR. McCARTIN:  Well, we only look at the
           top 3 millimeters in terms of what would be possible
           to be in the mass load, in the particulates.  Now, we
           keep track of the entire blanket in terms of -- or
           deposit for how long it persists there, but in terms
           of what's available for an inhalable dose, it is, I
           believe, is the top 3 millimeters.  It's some small
           amount.
                       MR. LARSON:  Taking into account the
           porosity of the tetra amount?
                       MR. McCARTIN:  Yes.  Now, DOE has a
           slightly different approach.  They assume all the
           radionuclides are in the top centimeter.  We do not do
           such a thing.  That's where we start comparing that
           very carefully.  We're looking at the -- it's an
           average -- it's uniformly mixed through the entire
           deposit.  DOE takes the radionuclides, as far as I
           understand it, and puts them all in the top
           centimeter.  So, there are differences.  There's a lot
           of subtle differences.  I tried to get on the ones
           that -- for now, we'll be doing some analyses in the
           future.
                       Here's another area where we think we can
           improve the understanding of erosion processes and
           things.  Certainly, some surface water hydrologists at
           the NRC -- Ted Johnson has been out to Yucca Mountain
           to help us better understand how things might change
           with major floods, et cetera.  And so we're hoping to
           do some more work along that line.  And certainly with
           respect to redistribution, there certainly are analogs
           for movement of even ash deposits.  I know Brit and
           some of this Center colleagues have been to Sierra
           Negro where there's an ash deposit, et cetera.  So
           there is some information that hopefully we can
           continue to --
                       MR. LEVENSON:  Tim, before you leave that,
           remobilization, in this same infamous report, it says
           "The high level waste contaminated tetra fall deposit
           will be modified by wind and water for many years
           after the eruption can be transported away into the
           critical group by wind and water following most future
           eruptions".  Are you analyzing multiple eruptions?
                       MR. McCARTIN:  No.  Once again, I'd have
           to read the whole page.  I recognize the one sentence.
           We certainly only analyze a single event.  I don't
           know -- Brit, do you know?
                       MR. HILL:  I was the author of the report,
           I think I can clarify that.  You consider a variable
           wind rows for any future eruption most of the time,
           unless you had a wind directed blowing towards the
           northwest sector at an extremely high wind speed,
           something on order of 10s of meters per second, you
           would have an appreciable amount of tetra falling on
           east-facing slopes that drain into the 40-mile wash
           drainage system.  So, for most eruption scenarios, you
           would have, even if the plume is directed away from,
           at that time, the critical group location, you would
           still have tetra that would fall on slopes that would
           feed into 40-mile wash and the potential grade leading
           down to the critical group location.  It's very
           difficult to have an eruption for a probability at the
           proposed repository site, and not have material
           eventually end up in 40-mile wash, even if the plume
           is 180 degrees from it.
                       MR. LEVENSON:  Well, that I understand,
           but that's not what this says.  This talks about
           future eruptions many years later.
                       (Simultaneous discussion.)
                       MR. HILL:  I know we haven't appreciated
           --
                       MR. LEVENSON:  Maybe it's just the words
           that are here.  I'm just reading what's here.
                       MR. LARSON:  Is DOE conducting similar
           studies?
                       MR. McCARTIN:  Certainly, they have
           evaluated the redistribution and the erosion at the
           location of the RMEI.  They right now are -- I don't
           know in terms of analogs off the top of my head, I
           know they are using USDA numbers for similar kind of
           areas to get a general erosion rate.
                       MR. LARSON:  There was some talk about
           using Sunset Crater at one point.
                       (Simultaneous discussion.)
                       MR. McCARTIN:  Could be, I'm not familiar.
           But it is an aspect of the calculation that certainly
           we think has some importance.
                       (Slide)
                       Finally, you end up getting a dose, and
           the inhalation scenario generally is related to how
           much dust or ash mass is in the air.  Estimating the
           mass loading as uncertainties, there are assumptions
           about outdoor activities, et cetera.
                       For the NRC approach, once again, we have
           -- and I tried to put these in similar terms between
           ourselves and DOE for ease of comparison.  We don't
           use an average over 10 years, but DOE's numbers were
           presented in that way, and so it's slightly easier.
                       As you can see, we have approximately on
           average about 1.5 to 2mg per cubic meter.  How did we
           get that number?  There are three components to it.
           The first one is a high disturbance, and that's
           looking at activity such as farming and plowing where
           a lot of dust is raised, possibly traffic on roads, et
           cetera, and there's a certain exposure time to that.
           We have approximately 1 percent of the time in this
           high disturbance type of activity.
                       Next, a lower value of mass loading for
           general outdoor activity, being outside, walking,
           other types of things.  That exposure time is around
           20 percent, and then sort of a background level that
           is at around -- add the two, it will be around 79
           percent to get to the 100 percent.
                       Generally, the dose is dominated by the
           first two.  Those two contributing about the same. You
           can see right now you have about an order of magnitude
           higher mass loading for this value, but the exposure
           time is about an order of magnitude less.  So, between
           the two, the overall dose is really dominated by those
           two.
                       In terms of, well, how long does it stay
           dusty?  What we do, we have a background mass loading
           that is significantly smaller, and we have a half-life
           of 10 years, and so this higher mass loading decays
           into the background with a half-life of about 70
           years. So, at approximately 70 years, it's going to be
           pretty much at that background, but it gradually
           decays.  And that is an assumption.  Some of that is
           based on analog information at Sera Negro.  That
           deposit has been there for a while.  How long will
           this ash stay there in a fairly --
                       CHAIRMAN GARRICK:  So what are some of
           these conditional dose rates?
                       MR. McCARTIN:  It depends on when -- well,
           it's dependent on many things.  Probably the two
           biggest variables to give you would be -- one would be
           the time that the dose occurs, primarily because of
           decay of some of the key -- the short lived nuclides
           that you don't see in the groundwater pathway, but if
           you have an event at, say, year 100, it's certainly
           more prevalent there rather than at 500 years.
                       And then how many waste packages do you
           assume are entrained -- and it's always dangerous to
           go off the top of your head, however, I will try to
           give you my best estimate.  I believe that for our
           base case, it's on the order of 10-to-100 rems at 100
           meters.  So that would be the worst event, and that's
           using these assumptions and everything else.
                       MR. HILL:  This is in the IRSR Rev 2, and
           Tim is correct, at about 100 years it's on order of an
           average of 100 rems.  At 1,000 years, it's on average
           of order 10 rems, and by 10,000 years it's on average
           of 1 rem as the conditional dose in that given year.
           But it is in IRSR Rev 2.
                       CHAIRMAN GARRICK:  Of course, if you were
           talking about a 100-year compliance period, you'd be
           talking about a substantially different probability.
           So, the weighted risk is still the way you have to
           look at it.  But I was curious.  Thank you.  I wanted
           to know what those numbers were.
                       MR. McCARTIN:  There's been a lot of
           evolution of this calculation, and even in the IRSR
           Rev 2, we have changed -- some of the mass loadings
           have reduced since then, and so there's a lot of
           thinking going on, but certainly we're in the right
           ballpark.
                       MR. HILL:  I don't think we've had order
           of magnitude changes, but again an order of --
                       CHAIRMAN GARRICK:  Well, I think the way
           you've stated it in terms of mg/m3 is the way to start
           this process.
                       MR. LEVENSON:  Do you have an estimate for
           how much solid material is deposited in the lungs if
           you're breathing 4.5 to 9 mg/m3?  Do you die of the
           dirt in your lungs?
                       MR. McCARTIN:  No, no, it's not that high.
           And be aware -- and this is another aspect that we're
           looking at with respect to -- I mean, it's -- and be
           aware that that's for 1 percent of the year at that
           high number, so --
                       MR. LEVENSON:  No, no, I was looking at
           the 4.5 to 9, which is 20 percent.
                       MR. HILL:  That's total suspended
           particulate, so an appreciable portion of that doesn't
           go into the lungs.
                       MR. McCARTIN:  That's what I was trying to
           get to, is the -- one of the things we want to look at
           -- I know DOE accounts for a much lower value than we
           would for what gets ingested, but some of this is
           larger particles that get into the nose and ultimately
           get ingested.
                       My understanding, in talking to our health
           physicist, is that doesn't cause -- it still causes a
           fairly significant dose, not as low as the DOE is
           estimating.  I'm not sure why those differences are
           there, that's another aspect that we want to look at.
           I don't know who has the more reasonable approach, but
           we're looking at -- in my mind, I thought -- we looked
           at particles that were inhaled through the nose and
           ultimately ingested, not going into the deep lung,
           caused about a factor of 2 lower dose than what was
           inhaled into the lung.  And so it isn't quite as
           important.
                       For DOE, I thought I remember reading
           something that was 3 orders of magnitude less, and I'm
           not quite sure why that difference is there, and
           that's something that I want to --
                       MR. LEVENSON:  Well, that would be a big
           function of time because if you are a couple of
           thousand years down the road and most of what's left
           is plutonium, it pretty much goes through your gut,
           it's not absorbed at all, whereas in your lung you get
           the dose.  So that ratio would be a big swing with
           time.
                       MR. McCARTIN:  Yeah, and that's -- once
           again, it's another thing we're looking at, but in
           terms of deep ingestion into the lung, we're not
           looking at.  It's not causing a significant health
           problem just because of the dust itself.
                       CHAIRMAN GARRICK:  Well, thanks to us,
           we've extended this a little, so maybe we'd better try
           to wrap up this before we freeze to death.
                       Who controls the thermostat in this room?
           Is there a reason that door is open?
                       VOICE:  Yes, sir.
                       MR. LARSON:  To let the heat in.
                       CHAIRMAN GARRICK:  Oh, to let the heat in.
           Oh, okay.
                       MR. BAHADUR:  It is by design so that the
           meeting will be really short.
                       (Laughter.)
                       CHAIRMAN GARRICK:  It didn't work.  Okay,
           Tim.
                       MR. McCARTIN:  I will try to go quickly.
           The DOE approach is -- we're not that different, but
           you can see we got to these numbers quite a big
           differently.  DOE has an outdoor value that they have
           32 to 45 percent of the time, and an indoor value for
           the remainder.  However, they have a mass loading that
           applies for 10 years.  After 10 years, they're at the
           background level, and so it drops off quite a bit
           quicker than ours.
                       (Slide)
                       In terms of the risk insight, if I look at
           the differences between our two approaches and be
           aware that there still is a fairly fluid situation, in
           my mind, because of the different approaches, also the
           part that DOE puts all the radionuclides in the top
           centimeter, there's a lot of little things there.  But
           I think, I'll say around a factor of 5 difference in
           risk.
                       What are we going to do?  we're going to
           start -- continue to look at analog systems for what
           is the right mass loading for different situations.
           As I mentioned, Brit, they've done some measurements
           at Sera Negro that can be used.
                       What's the evolution of the ash particle
           over time?  As was indicated, once you get up in the
           air is a big part of this calculation, when this ash
           is deposited.  How much of this and how does it change
           the particle size, that also is an important part.
           See, there's a lot of subtleties here that need to be
           considered.
                       And the last one that we're looking at is
           there has to be a correlation for how long the deposit
           persists and how dusty it is, and there certainly
           should be some -- if there's a lot of it in the air,
           the wind is blowing, it shouldn't last very long, and
           we'll be looking at that aspect of it for
           reasonableness, how long the deposit continues, and
           that's where the remobilization and the inhalation --
           this is one where there's just a lot of
           interconnection between what assumptions are being
           made.
                       And the next two slides is really -- and
           I'll try to go through them very quickly, and I think
           I can --
                       CHAIRMAN GARRICK:  They are very good, and
           they are quite self-explanatory.
                       (Slide)
                       MR. McCARTIN:  Right.  And what this --
           this is sort of a preview for the future, and what
           we're trying to work on is a simple explanation of the
           approaches in the TPA code, where the uncertainties,
           how we got to where we are.  I think we would like to
           do this for both our own code, but also for the DOEs,
           possibly a way to provide a very simple, quick way of
           explaining, understanding of the Repository.  And
           rather than going through the igneous slide, which
           really is in some areas pretty much a summary of what
           you just heard, I will skip past that and go --
                       (Slide)
                       -- one of the things we're hoping to learn
           from this exercise is that, indeed, as Marty
           indicated, we're treating uncertainty in a similar
           fashion.  That may not be the case everywhere, but I
           think it is important to understand how we're dealing
           with uncertainty.  And this may be -- I said earlier,
           when we're a little further along with this for the
           entire TPA code, it may be useful to come back to the
           committee and go through this and get feedback.
           There's a lot of different areas of the TPA code.
                       For example, what really matters for waste
           package?  Well, if you have a waste package that you
           think is going to last past 10,000 years, initial
           defective packages are quite important.  the question
           is, the uncertainty in estimating that is the
           manufacturing process, the closure, weld defects, are
           things you have to consider.  Right now, in the TPA
           code we have -- we're going from 0.01 percent to a 1
           percent failure based primarily looking at some analog
           manufacturing information.
                       CHAIRMAN GARRICK:  Boy, that's a big jump.
                       MR. McCARTIN:  Yes.  Well, on average,
           0.01 percent.
                       In terms of the corrosion, as we
           indicated, what are the big uncertainties there, and
           certainly the hydro-chemical/thermal environment is
           the key there, and certainly we have the short-term
           measurements, and the effect of the welding, and the
           post-welding, et cetera, what's the going to do to the
           lifetime.
                       Our current approach is that the corrosion
           rate is based on the relative humidity, however, how
           do we account for more aggressive water chemistries?
           We have a chloride multiplication factor that
           increases the chloride content and thereby affects the
           waste package failure time.  Right now, failures, as
           indicated here for uniform passive corrosion, it's on
           the order of 10,000 to 45,000 years.
                       Dripping on the waste package.  Where will
           packages get wet?  You have possibilities in the
           hydrologic environment for focusing flow.  You also
           have diversion, capillary diversion of water.  And so
           you've got a couple of processes there. In terms of
           the fraction of waste packages that get wet, we have
           a very broad range there.  It's all of them or none of
           them.  We sample between the two.  There is a lot of
           uncertainty three, and you can see we've taken the
           full range.
                       However, within that, there is -- I'll
           maintain it's Dick Codell's finest moment at NRC.  He
           may not think so, but in terms of how do you try to
           represent this dripping aspect, and he came up with
           some factors that account for how much water is
           dripping onto the waste package, and it's correlated.
           Although we do sample between zero and 1, when you get
           close to 1 where all the packages are being dripped
           on, it's a little bit of water.  Clearly, you have
           drips everywhere.  You have a finite amount of
           infiltration.  The amount of water than can drip on a
           package is small.
                       On the other end of the spectrum, when you
           get to very few waste packages, you have some focusing
           of flow, so you get a lot of potential for more water
           dripping on the containers because you have very few
           getting wet, but obviously where it's flowing there
           has to be more water to account for -- and I'll turn
           to Bill's infamous conservation of mass.  We've got to
           account for the water.  You can't have a lot of water
           on a lot of packages.  It's a lot of water on a few
           packages or a little bit of water on a lot of
           packages, and that really is what that tries to
           account for.
                       Right now, how does that vary? We go from
           basically 1 percent of the infiltration rate when a
           lot of them are getting wet, to 3 times when very few
           packages get wet.  So, you can see the range of the --
                       MR. LEVENSON:  Three times as much water
           reaches the package and comes in?
                       MR. McCARTIN:  No, 3 times the
           infiltration rate.
                       MR. LEVENSON:  It would be more than
           filtration rate.
                       MR. McCARTIN:  Not in volume, it's focus.
                       MR. LEVENSON:  Oh.
                       MR. McCARTIN:  The infiltration rate is --
                       CHAIRMAN GARRICK:  Funneled.
                       MR. McCARTIN:  Right.  In terms of the
           drip shield, right now in our code, we have no
           mechanistic model for its failure.  We specify a
           failure of time, which is approximately 5,000 years.
                       CHAIRMAN GARRICK:  That's quite a bit
           shorter than TSPA/SR at least.
                       MR. McCARTIN:  Yeah, I think so.
                       CHAIRMAN GARRICK:  It was about 20,000
           years, as I recall.
                       MR. McCARTIN:  But you can see, for us --
           once again, getting back to what causes corrosion,
           it's the humidity.  So, whether we have drips or not
           really doesn't affect the corrosion rate as much, but
           in terms of can spent fuel, if there is an initial
           defect, can water get in to mobilize the waste, the
           answer would be no.  And as I indicated, we do not
           have a diffusive release, we only have an invective
           release, so you do have to have dripping water.  We
           sort of felt without dripping water, you weren't going
           to get anything out of the waste package.  DOE would
           have releases from drips.
                       CHAIRMAN GARRICK:  So the drip shield
           serves your model.
                       MR. McCARTIN:  Yes.
                       CHAIRMAN GARRICK:  And essentially does
           not serve the DOE model.
                       MR. McCARTIN:  No. I mean, if they had a
           defective canister underneath the drip shield, even if
           the drip shield was intact, the way I understand it,
           they would still have releases.
                       CHAIRMAN GARRICK:  Well, they are based on
           diffusivity transport.
                       MR. McCARTIN:  Yes.  Spent fuel cladding,
           as I indicated, right now there is the unzipping of
           the clad.  We think it's fairly uncertain what kind of
           zipping would occur over hundreds of years, and just
           thermally you're not going to see dripping for quite
           a while, so you're looking at this not really as put
           into the repository, but quite a few hundred years
           afterwards.  We right now take no credit for --
                       CHAIRMAN GARRICK:  And that's kind of
           evidence supported.  There are thousands of assembly
           years of experience with no such phenomena observed.
                       MR. McCARTIN:  And then the final one is
           diffusion of the radionuclides from the waste package.
           There clearly is a very complex chemistry inside the
           waste package, however, when we've done our analyses,
           when you have dripping into the waste package, the
           invection will dominate.
                       We have not included diffusion when -- you
           get a hole and all of a sudden things start diffusing
           out.  we just don't include that, but we're aware of
           it.  We may do some additional analyses along these
           lines because of the DOE model.  At one time, be aware
           that we did have it in our TPA code.  We removed it.
           It cost a lot of computer time and produced such a
           small release, we said why bother.  We may add it back
           in, and we'll look at it, but --
                       CHAIRMAN GARRICK:  This was the bathtub
           model.
                       MR. McCARTIN:  No.  I mean -- well, we saw
           the bathtub model, but a diffusional release out of
           the waste package at one time we had.  We removed it.
           We were thinking about putting it back in due to the
           DOE model, but I think the important thing is we
           recognize the differences.  DOE appropriately shows us
           what the diffusional release is, the invection
           release, so we can understand the differences, but
           it's an interesting aspect between the two.
                       With that, like I said, we hope to do that
           for all the codes, and this was really a very quick
           cut.  We've just begun it.  We hope to improve the
           detail and information on there.
                       (Slide)
                       With that, let me wrap up very quickly.
           What we're trying to do is improve our understanding
           in areas important to representing the consequences
           from magmatic events and --
                       MR. LARSON:  Time, as a result of that
           improved understanding, have you come up with any FEPS
           that the DOE has disregarded that should not be
           disregarded?  Is this being looked at?
                       MR. McCARTIN:  Well, we certainly look at
           the FEPs. In a general sense, I'd say no.  They
           certainly are looking at the alternative flow paths as
           another -- although, there's a part -- is that a
           different FEP, or is it part of igneous activity?
                       And I'm really not aware of any
           significant FEPS that we've seen.  And how things will
           change, if I had to give my gut reaction as we go
           through all this work, I think it's possible one could
           see a 1 to 2 order of magnitude change.  Time will
           tell.  Like I said, there's a fair amount of work we
           hope to accomplish this year.
                       I'll make the offer -- none of my
           management are here, so I can speak freely.  I think
           it would be fair, as this work improves, we can come
           back and report on this, and certainly I think Brit
           and John Trapp, as the aeromag data comes in, that
           clearly  mobility is not my strength by any means in
           terms of how those might change.  It might make sense
           when that is, as that's analyzed, to come back also.
                       CHAIRMAN GARRICK:  A couple of closing
           questions.  How many agreements are outstanding on
           this KTI?
                       MR. HILL:  We had 22 to begin with.  I
           believe 6 are completed -- 7 are completed -- close
           enough.
                       CHAIRMAN GARRICK:  If all of this goes in
           the wrong direction, are we heading in a direction
           that could make this a possible problem?
                       MR. McCARTIN:  Well, I guess my impression
           of the estimates are I find it very hard to believe
           that these things at all go in one direction.  I think
           that is a very -- although there's no guarantees in
           life, but I think it would be very, very odd that they
           would all go in one direction or the other.  And so my
           personal take is that I think we're probably closer to
           maybe it stays the same and maybe it drops an order of
           magnitude.
                       MR. LARSON:  So your estimate there is not
           net, but individual estimates?
                       MR. McCARTIN:  No, it's net.  If I had to
           be pinned down, and that's what this is trying to do,
           I'd say 1 to 2 orders of magnitude, and I think that's
           the net change.  Which direction is it?  I think most
           likely it's the lower, my gut reaction at this time.
           There are things that could make it higher.  You saw
           a combination of both. Probability could increase.
           Number of waste packages might increase.  I think mass
           loading probably will be reduced.  So, where you end
           up I don't quite know.
                       CHAIRMAN GARRICK:  Andy, are they wanting
           anything from us on this, or is this informational?
                       MR. CAMPBELL:  Well, this is primarily
           informational preparation for future ACW reports to
           the Commission, but if the committee feels that it
           would like to weigh in on this issue, this is probably
           the time to do that because this is a particular KTI
           that's been talked about.
                       MR. LEVENSON:  Can I ask one more question
           out of ignorance, which is where most of mine come
           from.  Why is Mount St. Helen's not referred to as
           anything that might be an analog, is it so different?
           Probably better measurements on that than most.
                       MR. McCARTIN:  Well, in terms of -- Brit
           probably can answer this better than I, but I'll put
           my two cents in first and then go to Brit.
                       I do know DOE, in their reports, they
           certainly cite Mount St. Helen's as the basis for
           their ten-year -- after ten years reducing the mass
           loading to the background.  And so they are looking at
           some of that information.  There are aspects of the
           eruptiveness that are -- in terms of the mass loading,
           there are some limitations of Mount St. Helen's.
                       If you go near there in terms of --
           there's a lot of education, different soil types than
           Yucca Mountain, et cetera, that you have to take into
           account when you look at if the ash can be easily
           incorporated into the soil there versus possibly at
           Yucca Mountain soils, and that's something that has to
           be considered.  But I think we try to look at
           everything that's analogous, and I'll ask Brit if he
           has some other thoughts.
                       MR. HILL:  Just a couple of very quick,
           off-the-top points.  First, the grain size character
           of the Mount St. Helen ash, especially in the areas
           where the occupational studies were done for particle
           concentration.  It's fundamentally very different from
           what we see from basaltic ash.
                       Second, it is highly dedicated, well
           established soil that receives a lot more rainfall
           than we see from the Yucca Mountain sorts of
           scenarios.  So the granulometry is different, the
           depositional area is different.  The volume away from
           about the initial deposit itself is fairly small and
           very thin deposits.  On slopes and terrain it really
           was very stable to begin with, and also very permeable
           to begin with, that allow a lot of infiltration to
           occur.
                       So, while we can gain some general
           insights from the Mount St. Helen's information,
           trying to understand what's happening between zero and
           20 kilometers away from the Yucca Mountain system has
           some fairly significant limitations.
                       MR. LEVENSON:  We're assuming no climate
           changes for these 10,000 years, right?
                       MR. HILL:  We're looking, though, at these
           peak risks from volcanic disruption occurring on the
           order of the first thousand years.  So, while climate
           change would affect the 10,000 year view for the
           period that we're most concerned about, we're not too
           worried about climate change.  There's at least no
           evidence to support significant climate change in the
           first thousand years.
                       MR. LEVENSON:  And that affects the
           probability by a factor of 10.
                       MR. HILL:  The probability is the same at
           any given year.  There's really no -- with the
           homogenous fall recurring rate, there's no effective
           difference between the probability in year 100 and the
           probability in year 10,000.
                       MR. McCARTIN:  When we do our
           calculations, we're looking at year one, the
           probability.  We're not, say, taking the event,
           multiplying by 10,000 years, and getting a single
           probability to then say -- and I don't know, maybe Dr.
           -- this may not be as clear.  We don't say take 10-7
           times 10,000 so the probability of that event --
                       CHAIRMAN GARRICK:  No, I understand.
                       MR. McCARTIN:  -- okay -- at year one,
           it's 10-7.
                       CHAIRMAN GARRICK:  Right.  Okay.  Any
           other questions from any of the members, consultants,
           staff?  Yes?
                       MR. HAMDAN:  Tim, just one question.  I'm
           not clear on the one aspect of this.  Are we saying
           that every igneous activity will have an intrusive
           component and risk, and extrusive also?
                       MR. McCARTIN:  Yes.
                       MR. HAMDAN:  So, how are you deciding how
           much of the event is extrusive and how much is
           intrusive?  Do you assign probabilities, or how do you
           go about doing that?
                       MR. McCARTIN:  For us, right now, we
           merely -- we have -- we specified a number of waste
           packages that will be affected by intrusion.  We have
           not worried that much about assigning a specific
           probability, we just -- we can allow it to occur at
           the same time we do the eruptive one, but it tends to
           be -- relative to the eruptive one, it's a very small
           risk value.
                       MR. HAMDAN:  So, how about an intrusive
           event -- how about an igneous activity when that does
           not include eruption?
                       MR. McCARTIN:  It could be a factor of 10
           or higher in terms of probability.
                       MR. HAMDAN:  Is that modeled --
                       MR. McCARTIN:  We can.  I mean, right now
           the intrusive event is for us a very small amount.
           DOE obviously has a larger one and, like I said, we'll
           be looking at those differences.  It's quite possible
           we have it wrong.  If it comes up in consequence, then
           maybe we need to look at it a little more carefully.
           But, right now, we see it dominated by the eruptive.
                       CHAIRMAN GARRICK:  Andy?
                       MR. CAMPBELL:  I was just going to ask if
           there was anything to be gained in terms of ash
           distributions from looking at similar type of basaltic
           cones, signatory cones, in the basin and range.  You
           mentioned Sunset Crater.  Is there anything to be
           gained from studying the volcanoes that are there at
           Yucca Mountain in Crater Flats?  Are they so old that
           anything that you can interpolate to 10,000 years has
           long since gone?
                       MR. HILL:  Right.  The youngest volcano is
           80,000 years old, and almost all the ash deposit is
           gone, there's just a fragment here and there.  In
           terms of the basin and range, the Sunset Crater is
           about 1,000 years old.  It's much larger volume.  But,
           again, one of the two volcanoes of similar type that
           still has a preserved deposit, we're not using it as
           a direct analogy, we're trying to look at how tetra
           would behave, but not how the eruption would progress.
                       That's why we've been using the historical
           analogs, because we have nothing in the basin and
           range that's historical, and most of the deposits are
           before the highly eroded condition, so we look at much
           younger deposits on the order of 50 to erupting while
           we watch, so that we can better understand the
           dispersive processes.
                       But looking at places like in Mexico or
           Sunset Crater and then comparing those to the older
           volcanoes in the base and range, that's where we came
           up with the scaling for at 1,000 years there seems to
           be some deposit left, at 10,000 years it seems to be
           pretty well gone.  So, the 1,000 year half-life that
           we're using is really a scale of 100 year, 1,000 year,
           10,000 years.  You see it at 1,000, we don't see it at
           10-, and clearly it's there at 100.  So, 10,000 year
           it's all gone, given a half-life of 1,000, that seems
           to be the best first pass.
                       MR. CAMPBELL:  One other question for Tim,
           on these tables that you developed at the end of your
           presentation, is there any thought to developing a
           column to identify built-in conservatisms, and this is
           an issue the committee has been dealing with, and kind
           of raised it in the context of TSPA/SR of identifying
           conservatism.  Has the staff thought about it, you
           guys thought about, you know, looking at how
           conservatisms are being treated and carried through
           the model?  Is that part of all this?
                       MR. McCARTIN:  We certainly will look into
           that.  I'm always trying to think of a better word
           rather than "conservatism".  I don't think there is
           one, unfortunately.  The only reason I say that, we
           need to get to that, but part of it is the information
           you have, and some of it is you're making some
           assumptions and, as Dr. Garrick said, assumption base
           versus evidence, so often --
                       CHAIRMAN GARRICK:  What might be better is
           a cryptic identification of the relevant evidence.
                       MR. McCARTIN:  Yes.  Absolutely.
                       CHAIRMAN GARRICK:  Supporting evidence.
                       MR. McCARTIN:  And that is one there that
           here's what the evidence tells us, and let someone
           draw their own view of whether it's conservative or
           not.
                       CHAIRMAN GARRICK:  Any other questions
           from anybody?
                       (No response.)
                       Okay.  I want to thank Brit and Tim for a
           very informative hour presentation that went a couple
           of hours, and we look forward to following up with all
           the path forwards that you identify, and we also want
           to thank our consultant for his significant
           contribution in this session, and we will now take a
           recess and when we come back -- this terminates all of
           our briefings and discussions of this type.
                       We will now go into our usual letter
           discussion and letter-writing session, for which we
           will not need reporting, and until then we will take
           a 15-minute break.
                       (Whereupon, at 3:40 p.m., the briefing
           session was concluded.)

Page Last Reviewed/Updated Thursday, March 29, 2012