Advisory Committee on Nuclear Waste 131st Meeting, January 8, 2002
Official Transcript of Proceedings
NUCLEAR REGULATORY COMMISSION
Title: Advisory Committee on Nuclear Waste
Docket Number: (not applicable)
Location: Rockville, Maryland
Date: Tuesday, January 8, 2002
Work Order No.: NRC-166 Pages 1-37
NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers
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(202) 234-4433. UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
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ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW)
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JANUARY 8, 2002
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The ACNW met at the Nuclear Regulatory
Commission, Two White Flint North, Room T2B3, 11545
Rockville Pike, at 11:00 a.m., George M. Hornberger,
GEORGE M. HORNBERGER, Chairman
RAYMOND G. WYMER, Vice Chairman
B. JOHN GARRICK, Member
MILTON N. LEVENSON, Member
ACNW STAFF PRESENT:
HOWARD J. LARSON, Special Assistant, ACRS, ACNW
RICHARD K. MAJOR
JOHN T. LARKINS
RICHARD P. SAVIO
CAROL A. HARRIS
Opening Statement. . . . . . . . . . . . . . . . . 4
Discussion of Proposed Amendment to
10 CFR Part 63 Adjourn . . . . . . . . . . . 5
Presentation by Tim McCartin . . . . . . . . . . . 7
CHAIRMAN HORNBERGER: The meeting will
come to order. This is the first day of the 131st
meeting of the Advisory Committee on Nuclear Waste.
My name is George Hornberger, Chairman of the ACNW.
Other Members of the Committee present are
John Garrick, Milton Levenson and Raymond Wymer.
During today's meeting, following the
planning and procedure session, the Committee will
discuss proposed revisions to 10 CFR Part 63, discuss
proposed letters and finalize plans for a Committee
John Larkins or Howard Larson is the
designated federal official for today's initial
This meeting is being conducted in
accordance with the provisions of the Federal Advisory
Committee Act. We have received no written comments
or requests for time to make oral statements from
members of the public regarding today's session.
Should anyone wish to address the Committee, please
make your wishes known to one of the Committee staff.
It is requested that speakers use one of
the microphones, identify themselves and speak with
sufficient clarity and volume so that they can be
Before proceeding, I would like to cover
some brief items of current interest. It has been
announced recently that Bill Reamer will become the
Deputy Director, Division of Waste Management,
replacing Josie Picone who will become the Deputy
Director, Office of State and Travel Programs. Mr.
Jack Sorenson, ACRS staff Senior Fellow, completed his
term with the Office on December 31, 2001. He has now
joined the Office of Nuclear Material Safety and
Safeguards to assist in risk-informing activities.
The trade press recently reported that politicians in
the Swedish town of Oesthammar have voted to allow
drilling in bedrock in the community to see if it is
suitable for a final spent fuel repository. Mr. Phil
Justice has been assigned as NMSS liaison for the
We are going to proceed to our discussion
of the proposed amendment to 10 CFR Part 63 and John
Garrick is the cognizant member. I'll turn it over to
MEMBER GARRICK: Thank you. We're going
to hear from the staff on a proposed rule on 10 CFR
Part 63 which has to do with the specification of the
probability for unlikely features, events and
processes or as they are affectionately known as FEPs
and as I understand it, the Commission has voted this
proposed rule, but it has not been published yet for
public comment because the SRM is still being held up
for reasons that maybe Tim will explain.
What is involved here is that the EPA
Yucca Mountain standard is really -- involves three
standards, three separate standards: the so-called
All Pathway standard, the Human Intrusion standard and
the Groundwater standard.
And in the EPA standard, the concept of
very unlikely events has been defined as a specific
number and these are excluded from all three
standards. So these numbers, these thresholds become
very important because they drive the issue of what
can be considered or what has to be considered and
what doesn't have to be considered.
And for the Human Intrusion and
Groundwater standard, the category called unlikely
events may also be excluded, but the EPA left it up to
the Nuclear Regulatory Commission to define what is
meant by unlikely.
So this is a topic of considerable
interest to the Committee. The problem here is that
it is sort of after the fact advice that something we
were talking about earlier and it's somewhat difficult
for the Committee to have had much of an impact on the
voting of the Commission. And this is one of the
flaws that we've spoken about in the past that's
inherent in this whole advisory process. But we don't
want to dwell on that at the moment. We are going to
talk about it at our retreat.
One of the things that I'm very interested
in, in this whole discussion is I think maybe an issue
that's just as important as what these numbers ought
to be is the issue related to the process of
assembling or disassembling or aggregating FEPs
because you can imagine that you might have something
that's just above an acceptable threshold and through
redefinition of the FEPs or the scenarios or what have
you, you end up with a set of conditions that are
actually below the threshold and I'd be very
interested in the discussion in being assured that
that kind of manipulation is protected somehow.
So with that, Tim, Tim McCartin, we're
looking forward to your clarifying where we are in
this issue and perhaps answering some of our
MR. McCARTIN: Hopefully. Thank you, Dr.
As you noted, we'll be talking about the
probability of unlikely events. I would like to make
a few introductory statements and one would be, as you
alluded to, although we are anticipating an SRM
shortly, we do not have one, so this presentation
should be viewed as the staff opinion. It isn't the
Commission's opinion yet until a proposal is
Likewise, I do know that I believe we try
to and get benefit from participation with the
Committee and I would say it is unfortunate that we
did not -- were not able to come to the Committee with
our proposal prior to going to the Commission.
However, we were aware of that. We knew the
limitations of it. We were operating with an SRM on
final Part 63 that directed us to do an expedited rule
making and gave us a relatively short time period to
do this. And so there really wasn't an opportunity to
interact appropriately or as we typically would like
However, we think that going out with the
proposal, rather than getting the Committee's maybe a
very hurried quick opinion, we're proposing a 75-day
comment period. During that public comment period we
would like to come back to the Committee, discuss the
public comments we get and get the Committee's
reaction at that time and certainly we would factor in
any Committee's opinions, views in the final to this
amendment. But it really -- we had approximately 2 to
3 weeks to do this before getting into the concurrence
process and so writing this in two to three weeks
really does not lend itself well to getting a lot of
input and thereby the Commission saying do an
expedited rule making which is direction to skip some
of the things you normally would do.
Also, along those lines, I'll repeat it at
the end, but when we're talking about unlikely events
in this context, I think it's very important to
recognized that unlikely is for this application only.
It is a very good qualitative word. We aren't
suggesting that we're defining the word "unlikely" for
all the uses that might be used in regulation at NRC,
but merely in this application.
Generally, I'd like to give you a little
of the regulatory background, some of the technical
background that we thought about and then finally I'll
give what our proposal for the probability value for
unlikely events is.
I will probably slip into using the
unlikely events. The language is actually features
events and processes and sequences of events and
processes, but a shorthand way of saying is I just use
the word "events", but I mean the full spectrum.
The background, as actually Dr. Garrick
alluded to, the EPA standards were finalized on June
13th of last year. There were three standards: the
individual protection standards, human intrusion and
groundwater protection. Very unlikely FEPs are not to
be considered in any of these calculations. Unlike
FEPs are to be considered only for the individual
protection standard. They're excluded from
consideration in groundwater protection and human
The final standards went a little further,
obviously as proposed in the EPA standard the cutoff
for very unlikely FEPs was a one chance in 10,000 of
occurring within the 10,000 years, what we sometimes
refer to as the 10-8 per year cutoff. That's for very
unlikely FEPs. The probability for unlikely FEPs were
not defined and they left that to the NRC.
In looking at the preamble to the
standards, it's important to look at how unlikely is
to be applied. As I mentioned human intrusion,
groundwater protection. They're very specialized
calculations. The human intrusion calculation is done
to look at the robustness of the repository to the
consequences of intrusion. Likewise groundwater
protection is to evaluate the degradation of the
groundwater resource. They're very specialized
And further, in looking at these
calculations, the preamble to the standard really
talks to focusing the calculations on likely or
expected performance, so the reason for excluding
unlikely is you're trying to get to what is the likely
behavior, expected behavior for these two specialized
Final part 63 was published in November of
last year. In it, the Commission indicated that they
intended to conduct a separate rulemaking to define
unlikely and indicated that the numerical value would
be somewhere between 10-8, 10-4 per year.
Our approach in looking at how to define
unlikely, conceptually we thought it was easier to
think of three broad categories: very unlikely,
unlikely and likely. Clearly, we already had a
definition, a quantitative definition very unlikely,
the 10-8 per year and in looking at those three
categories we felt it was easier conceptually to think
of very unlikely and likely. If you set the values
for those two, you clearly have the middle defined and
so looking at a lower bound for what should be
considered a likely FEP, we felt that somewhere
between 10-6 and 10-4 range was an appropriate value
for what could be considered likely as a lower bound
Quantitatively, what does that really
mean? The 10-6 per year is essentially a 1 percent
chance of occurring within the 10,000 year period. We
felt that a 1 percent chance of occurring is neither
expected nor likely. 10-5 per year is a 10 percent
chance of occurring within the 10,000 years. And then
if we go to 10-4 per year, it's a very high
probability of occurring within the 10,000 years.
Obviously, it's very likely that it would occur.
And I know I was accused early on of the
Goldilocks Syndrome here and one's too low, one's too
high, the middle one is just about right and the 10-5
per year would seem to be a 10 percent chance of
occurring as the lower bound for likely, that if you
got much lower than that, sort of like 10-6, 1
percent, that should not be considered likely. The
10-4 per year, that would seem to be, you would want
to be a little lower than that. It's almost certain
to occur. It's very likely to occur.
And thus, our proposal, we felt that
unlikely FEPs would be best characterized by a
probability range and we're defining the unlikely FEPs
as that value between 10-5 and 10-8 per year,
essentially a 10 percent chance of occurring at the
high end, down to the .01 percent chance which is
really the 1 in 10,000 over 10,000 years at that for
the very unlikely.
We think that upper bound of 10 percent
for unlikely seems to be a prudent range for defining
the unlikely events in the context of these two
calculations. Once again, it's not intended as a
precedent for other applications where the term
unlikely might be used in NRC regulations. At the
beginning of this exercise of writing the amendment,
we looked at the word unlikely, where is it used? It
appears in all kinds of places, other regulations. It
really is the context and for this particular
application it's appropriate. There are many other
uses of the word unlikely and we are not setting
precedent for that.
Where are we at? Right now, we anticipate
that we will get an SRM shortly and the amendment will
be published this month, 75-day comment period. We
anticipate that we would have a final amendment some
time in the summer to early fall. And once again, I
would like to reiterate that I think during the public
comment period, as we get some of the comments in,
there could be an appropriate time, maybe more than
one time, to come back to the Committee and discuss
the comments we've gotten and where we think we're
headed with this amendment.
And with that, if there are any questions,
I'd be happy to try to answer them.
MEMBER GARRICK: Thanks, Tim. Milt,
MEMBER LEVENSON: You did what is fairly
easy to do which is to confuse me, Tim. After you've
defined that you're going to talk about three things,
very unlikely, unlikely and likely, you then ring in
a new one which is very likely. Is that intended to
be a different category?
MR. McCARTIN: No, no. It was just -- the
10-4 in terms of -- I guess we could have -- well, we
were looking for the lower bound for unlikely or the
-- the lower bound for likely and --
CHAIRMAN HORNBERGER: Just take the "very"
off and you solve the problem.
MR. McCARTIN: The reason "very" is there,
that in terms of -- it's too likely to be considered
the lower bound for likely.
MR. BAHADUR: Is 10-5 likely?
MR. McCARTIN: That's the -- yes, the
lower bound for likely. That's what our proposal is.
The lower bound for likely, the upper bound for
unlikely. You've got three categories. Obviously,
MEMBER LEVENSON: Okay, one other
question. From a standpoint of risk informed and I
know maybe probably it isn't possible for this, but
I'd like your comment on the idea of defining these
independent of consequences when they're a basis for
screening out things. You're not -- there's nothing
in here that allows you to throw something out because
even if it's likely, the consequences are unimportant.
There's a whole separate set of things, right?
MR. McCARTIN: Right. It does not look --
MEMBER LEVENSON: You still have the other
screen, even if something is very likely, but has
extremely low consequences, still have the ability to
throw it out?
MR. McCARTIN: Oh, absolutely. I mean the
regulation allows for something that does not have a
significant effect and that would be certainly based
on low enough consequences or low enough risk.
CHAIRMAN HORNBERGER: That would occur in
screening the FEPs, is that right?
MR. McCARTIN: That's one area you could
do it. You could actually have a FEP come in. You do
the analysis you see that the consequences and/or risk
is low enough that we -- it does not have a
significant effect on the time or the magnitude of the
dose. I can eliminate it. And that's really the --
in the rule, it does say that. Things that don't have
a significant effect on the timing and magnitude of
the dose, do not have to be included in the analysis.
MEMBER GARRICK: Ray?
VICE CHAIRMAN WYMER: Once these
categories are defined, then you get down to the
really tough question of how do you determine
probabilities. Where in the regulations is there
criteria for doing that?
MR. McCARTIN: Well, the only thing -- the
one thing we have said is that we, along the lines I
know Dr. Garrick mentioned that could there be
mischief by defining things a particular way merely to
get it a low enough probability to get it out of the
analysis and we have said that in general for events,
categories of events and we're expecting a broad
definition of the event, rather than a very narrow
definition and maybe a simple example could be that if
you have seismicity, seismicity as an event occurs.
If you wanted to define maybe a very
narrow range of magnitude of the seismic event, you
could get down to a very small probability and we're
not looking at -- we're not expecting a narrow
definition. It tends to be more of a broader
definition, but other than that, there's nothing
that's part of the NRC review. It would be looking at
how a particular event was defined that potentially
led it to be screened from the analysis.
VICE CHAIRMAN WYMER: So you take somebody
else's calculation of probability and evaluate it?
MR. McCARTIN: Yes.
VICE CHAIRMAN WYMER: Okay.
MEMBER GARRICK: George?
CHAIRMAN HORNBERGER: Tim, let's see, how
can I phrase this question? One of the things that I
found a little confusing is this notion that you
presented that should we have a probability range or
a single number. At first I thought well, a single
number can't be what Tim means because that doesn't
make any sense. You're not going to pick the square
root of 2 times 10-6, the single number for an
unlikely event. So that isn't what you mean.
So what I don't understand is then what
the distinction is between saying okay, I'm going to
pick the single number, less than 10-5. How is that
different from defining a range?
MR. McCARTIN: I don't believe it is.
CHAIRMAN HORNBERGER: Okay.
MR. McCARTIN: But --
CHAIRMAN HORNBERGER: So in terms of plain
language, don't you think that you might be doing
violence to understanding by raising this as a big
MR. McCARTIN: Well, what it does is --
the reason we use the range, we also have that lower
end cutoff, that unlikely doesn't proceed on to zero,
if you will, but it stops at the 10-8 and from that
point on it's very unlikely and it's really just
creating that here's the range for unlikely and then
here is likely. But you're right, it's just --
CHAIRMAN HORNBERGER: In the presentation,
you can add confusion by saying well, we're not
picking a single value. We're picking a range when --
obviously, that's what you're doing.
MR. McCARTIN: Well, yes. Maybe a better
way to say it is it's less than 10-5 and therein is
less than 10-8. That might --
CHAIRMAN HORNBERGER: I think you
mentioned this. It is important to highlight that
this decision, as Ray indicated well how do you decide
on these probabilities. These would only be the
unlikely events or event sequences or the whole -- I'm
using event the same way you said you were going to
use it. It's only for the stylized analyses for human
intrusion and well, basically igneous activity.
MR. McCARTIN: Groundwater.
CHAIRMAN HORNBERGER: Or groundwater
protection. So they're not screened out over the all
pathways dose at all?
MR. McCARTIN: No, no. The individual
protection would have the unlikely events, yeah.
Obviously, very unlikely is excluded from everything.
CHAIRMAN HORNBERGER: Right.
MR. McCARTIN: But the unlikely is
included in the individual pathway.
CHAIRMAN HORNBERGER: Thanks. That's all
MEMBER GARRICK: Tim, how would you
correlate FEPs with scenarios?
MR. McCARTIN: I would say that to me it's
easier to think of the events and an event is like a
scenario class. I think they're similar.
A scenario class would have some
collection of FEPs within it.
MEMBER GARRICK: Yeah, yeah. FEPs also
contains the word process.
MR. McCARTIN: Yes.
MEMBER GARRICK: So it's not impossible
for a process to be characterized as a scenario.
MR. McCARTIN: Yes, right. Generally, to
date, probabilities, explicit probabilities have been
assigned primarily to events. The DOE and ourselves
have not tried to assign a probability to a feature or
a process. It could be done, but to date it generally
is looking more at the events.
MEMBER GARRICK: Now I guess the other
question I would want to ask is why are we doing this?
Why aren't we just focusing on the risk of not meeting
the standards and just calculate that risk? Why do we
want these thresholds?
MR. McCARTIN: Probably as much for
practicality purposes, I think. Certainly, the 10-8
cuttoff for very unlikely, I think you come to a point
where how low do I want to try to go to estimating
what might happen? And I think 10-8 in part, is due
to practicality of how far I want to go in probability
space. 10-10, 10-12. I mean you get to some pretty
outlandish kinds of things and a lot of speculation,
depending on how far you go down. I think 10-8 is
there, as much for practicality in that it seems to be
a reasonably low level. We don't want to go lower.
The unlikely events, in my opinion, is
recognizing that we have two very special calculations
here, human intrusion and groundwater protection and
you're trying to get more -- you don't want to go to
as extreme events as you've considered in the
individual all pathway. But you're looking at, in a
general sense, what's likely to occur. And it's one
also of for these calculations will do a simpler kind
of calculation. I would say it's one of practicality,
once again and -- but I don't know, from a risk
standpoint should you look at a 10-10 event that has a
MEMBER GARRICK: Well, we've run into this
problem in the large scope risk assessments of nuclear
power plants and the reason I ask the question about
scenarios is that you can look upon a risk assessment
as a structured set of scenarios. And the question
was if you impose screening levels, you need to be
careful to not get in the position that there's 10-4
events and so what we did was stored all of the events
that were screened and included them in the aggregate
calculation of the final risk measure which could be
something like an off-site dose or a release category
or a core damage frequency or what have you.
But that, at least, protected us against
any accumulated effect that might come from a class of
scenarios that met the cutoff criteria, but we didn't
throw them out. We kept them in the bottom line
calculation. Do you anticipate a similar approach
MR. McCARTIN: To date, we have not been
as worried about the completeness argument.
MEMBER GARRICK: Right.
MR. McCARTIN: That -- which is what I
think you're getting at. Could we throw away enough
things that indeed we're really not representing the
risk of the facility any longer.
MEMBER GARRICK: Right.
MR. McCARTIN: And I believe in the rule
where we talk about we're expecting the events in
these types of things to be defined in a broad sense,
that we have not seen an effect that would, that is
throwing out big chunks of risk, if you will. I look
at say volcanism, seismicity.
I mean these things are in and they're in
a broad sense, they're not things -- we have not seen
things being tossed out that the cumulative effect
would be that now we have 10 percent of the risk and
90 percent of the risk was tossed out. Certainly, the
desire was when we said that we were expecting a broad
definition was trying to get at that fact. I think
our review would have to look at it. We have to look
at what gets thrown out, etcetera.
As you know, the rule also talks to not
the amendment, but final 63 talks about we want to see
DOE's basis for what they threw out and I think we
would have to be sensitive and be able to answer that
question. Have we thrown out more risk than we've
kept in, but right now I think because the categories
tend to be broad --
MEMBER GARRICK: Of course, another
opportunity for accountability here would be the
uncertainties, the uncertainties could be impacted by
the impact that is judged from the FEPs that have been
In principle, I like the idea of a range
versus a value, although as George says, the threshold
is a value. But the range is an interesting concept
and I think a step in the direction of accounting for
In the decision to do that did you
consider going the next step of actually imposing a
distribution function? I can imagine a p0 function,
a probability frequency function that would
characterize this parameter, this range even more
fully in a risk sense.
Did you consider that at all?
MR. McCARTIN: No.
MEMBER GARRICK: Rather than a limit line
as in the Reg Farmer limit line idea, you would have
a limit distribution and that way --
CHAIRMAN HORNBERGER: Does that mean that
you would partially include the analysis in the human
MEMBER GARRICK: No, what I'm talking
about is that if you do a calculation of the frequency
of occurrence event and you characterize that
calculation as a probability density function, does
that function -- is that compatible with the criteria
and the criteria could be a PDF. That's all I'm
CHAIRMAN HORNBERGER: I guess I don't
follow that. It seems to me that what Tim is
describing is a way to conform to what is stated in
the EPA rule which is to define when an event sequence
or whatever, however we want to call it gets included
in, for example, a human intrusion stylized analysis.
MEMBER GARRICK: Yes, I understand. But
all I'm suggesting is that --
CHAIRMAN HORNBERGER: That requires a yes
or no answer is what I'm saying.
MEMBER GARRICK: Yes. But I think that if
you're starting to talk about criteria of what
constitutes an acceptable value, you could do it in
the context of distribution functions as well as you
could do it in the context of ranges, as well as you
could do it in the context of specific numbers.
That's all I'm saying.
CHAIRMAN HORNBERGER: Not to define a
MEMBER LEVENSON: Well, in essence, it's
the same thing. The EPA cutoff says that you run
hundreds of analyses --
CHAIRMAN HORNBERGER: No, no. I
understand the rule, but it has nothing to do with --
MEMBER GARRICK: George, all I'm saying is
that you can represent likelihood in a number of
different ways. One way you can represent it is with
the frequency without regard to uncertainty. Another
way you can represent it is with the probability and
inherent in your probability would be an uncertainty.
But another way you could represent it is in the
probability of frequency and you could have the notion
of frequency and you could say there's uncertainty in
that frequency and I characterize that certainty in
the form of a probability distribution.
And so all I'm suggesting is was there any
CHAIRMAN HORNBERGER: But still, it
strikes me -- suppose you now identify an events
sequence and you say well, there's a probability
distribution associated with it and with central
tendency as 10-6 or 5 times 10-6 per year and some
dispersion parameter around it. Is that event likely,
unlikely or very unlikely?
MEMBER GARRICK: Oh, I would, I guess I
left out a part. I would -- this is how I would go
possibly instead of the concept of likely and unlikely
and very unlikely.
CHAIRMAN HORNBERGER: Okay.
MEMBER GARRICK: To me, the concept of
very unlikely, etcetera, is an intermediate step 2
that kind of -- that PDF kind of characterization.
CHAIRMAN HORNBERGER: I understand that
now. But what I'm saying is that it strikes me that
what Tim is faced with doing is conforming with the
existing EPA regulation which doesn't permit that.
MR. McCARTIN: I guess I would prefer the
-- in the regulation it be fairly rigid in terms of
less than 10-5, greater than 10-8, but in terms of
application and I don't know if this would get to some
of your desires, would be when I'm looking at
assigning a probability to a particular FEP, could I
use a distribution for the probability of that FEP and
I think the answer is yes.
Now the issue would be one of well, is it
in or is it out? If I get a little bit over here and
I think the intent of the rule where you're looking at
mean kind of behavior, I would say if you use a
distribution which is characterizing the uncertainty
in your probability estimate, if the mean of that
distribution would be -- you would use the mean to
decide whether you're in or out. That's something
that I think we probably will be looking at, possibly,
in the context of the review plan.
VICE CHAIRMAN WYMER: But the real problem
is going to occur when you come up with an event which
is neither very likely nor very unlikely, but likely.
Then you're on pretty shifting ground.
CHAIRMAN HORNBERGER: No, then it's in.
MEMBER GARRICK: Then it's in, yeah.
VICE CHAIRMAN WYMER: But then you're
going to apply a judgment.
CHAIRMAN HORNBERGER: No, no, no. Then
it's in the analysis. Then it has to be considered in
the groundwater protection analysis and in the human
intrusion, stylized human intrusion.
VICE CHAIRMAN WYMER: Okay, I see what you
MEMBER GARRICK: One other comment, Tim,
here. You describe these as qualitative evaluation
guidelines. In order to establish compliance, you're
really imposing a very quantitative requirement on the
part of the analyst, right?
MR. McCARTIN: Absolutely, yeah.
MEMBER GARRICK: Because these thresholds
are pretty definite.
MR. McCARTIN: Well, you are right and the
qualitative was more in terms of the preamble in the
EPA standard. This is a qualitative word. Here are
some of the things they said in a qualitative sense to
give you an indication of what the intent was and by
that, if you look at qualitatively the words, they
were intending to have expected conditions, likely
conditions and so when I look at -- I've got this
qualitative word unlikely and the intent as the way we
read it is to get to likely expected conditions and
that is what allows -- we then went okay,
quantitatively, you're absolutely right.
We want a very sharp, clear indication of
how we will implement that and that's why we're --
there is no doubt there. I mean we're proposing 10-5
as the one end and 10-8 at the other and likewise for
very unlikely, 10-8 is very sharp. There is no
qualitative nature to that.
MEMBER GARRICK: I think the thing that
you have to be very much alert to is that the analysts
don't get so involved in these evaluation guidelines
that they compromise the real issue here which is
calculation of the risk of meeting the standard and
that's -- no, that's the thing that a lot of these
kind of bottom up considerations tend to do.
There is something people can get hold of
and they run with them and it's one of the reasons why
we, for example, were against subsystem requirements
was we want the focus to be the measure of its been
identified by law, in this case the three standards,
15 milirem, 15 milirem and 4 milirem. That's the
context. And that's something I think you'd want to
be very careful with in this.
MEMBER LEVENSON: So is the total thrust
of this as George just implied a minute ago, to these
categories, to decide whether or not you do an
analysis, whether or not it's in the --
MR. McCARTIN: Well, the analysis will be
done. The question is what kinds of FEPs do I include
in the analysis and in reality I mean you can look at
-- and I'll talk to both cutoffs. The 10-8 cutoff, as
you know, I think on the plus side, you can -- do you
consider all the important things at Yucca Mountain.
I mean you have volcanism in that calculation.
We can't think of many things below 10-8,
I mean there's things that people --
CHAIRMAN HORNBERGER: A Bolide impact.
MR. McCARTIN: Which?
CHAIRMAN HORNBERGER: A Bolide impact.
MR. McCARTIN: Oh. Tsunamis. There's
CHAIRMAN HORNBERGER: No, no, no. A
Tsunami isn't very likely to come over the Sierra, but
if you look at a probability of a Bolide impact, it's
not -- it's less than 10-8, but it's certainly not
There are craters in Arizona.
MR. McCARTIN: Yes, yes. But I think one
is sufficient enough to disrupt the repository 300
meters down, I think has been characterized as less
likely than --
CHAIRMAN HORNBERGER: I was agreeing with
you. It's less than 10-8 if you're screening it out.
Potentially bit impact.
MR. McCARTIN: Yes. So I think you've got
those kinds of things in there. When you get to what
should we include in human intrusion and groundwater
protection, certainly igneous activity at 10-5 falls
out certainly and then you've got things like rock
fall seismicity will still be in to some extent. At
least qualitatively that's how we see the
calculations. What is the impact of this particular
amendment, that really is the primary effect and we
think the calculations will be done. It's just a
matter of what gets included.
CHAIRMAN HORNBERGER: Tim, it strikes me,
this is just a follow-up on John's last comment that
you already have, I think, good experience to draw on
that goes to two of the things that John mentioned,
first of all, a distribution of frequencies and second
of all, what happens, how you make logical decisions
about whether something is screened and that is you
look at igneous activity and DOE's analysis as I
recall right below 10-8, but with a broad distribution
adn so it doesn't get screened out even though the
mean or the median of the distribution is below 10-8.
I think that you don't throw out good judgment when
you draw these lines and I think that you have good
experience with that already.
MR. McCARTIN: Right. I believe DOE's
latest numbers have it slightly greater than 10-8, but
it's on that edge, but that's one of the things,
clearly, that we would be reviewing and looking at,
things that are screened out that are near that
boundary, be it the 10-8 or 10-5 and what's the basis.
MEMBER GARRICK: How important do you
think these categorizations will become in the
analysis, the unlikely, very unlikely and likely?
MR. McCARTIN: The understanding we have
to date would say that it's not very important. With
the simple -- with one simple caveat that there are
some things that the calculation will be somewhat
easier to do without and the -- not having to include
igneous activity in the groundwater protection
calculation and the human intrusion calculation. It's
one less thing to have to include there. The
calculations we've done to date would say that isn't
-- wouldn't have made a difference.
MEMBER GARRICK: In the nuclear weapons
field they have a similar categorization and they have
a very unlikely, well, they have unlikely, very
unlikely and extremely unlikely. Was there any
discussion or interaction with them on this whole
process and how it has worked? They've been doing
this for a number of years.
MR. McCARTIN: No. I can tell you when we
first started on this amendment, we talked to a number
of people in the Agency both within NMSS and NRR and
the Office of Research in terms of give us some
insights on the unlikely, very unlikely, etcetera.
MEMBER GARRICK: Right.
MR. McCARTIN: And the overall response I
got from everyone was that it really depends on the
exact nature of the calculation you're doing and the
consequences and they said -- everyone was somewhat
unwilling to do much without knowing more about the
impact and what the application is. And so I think
for now, I think we're comfortable defining it in the
context of Yucca Mountain, in the context of the
10,000 year compliance period, in the context of human
intrusion, groundwater -- it's a very specialized
application and for here, I think it makes sense.
There aren't many other people that deal
with the 10,000 year compliance period in terms of
looking at consequences and so we didn't get a lot of
information from the people we contacted, but we did
not go outside the Agency, I will say that.
MEMBER GARRICK: Any other questions?
MEMBER LEVENSON: It seems to me an
important factor here, John, and that is that it looks
like they no longer have to consider human intrusion
occurring during a volcano eruption.
MEMBER GARRICK: We used to call those
MR. HAMDAN: Yes. Tim, do you have
anywhere in the rule some basis for the 10-5, why it's
not 10-6 or 10-4, for example?
MR. McCARTIN: Well, that's what the
amendment is doing is proposing 10-5. In the
amendment, we certainly talk to the other three
values, 10-4, 10-6 and give our rationale for it, but
this is the proposal. And once again, when we -- I'll
say we go up before the Commission and even though
OGC, the legal arm of NRC, for a proposal for
rulemaking it's just that. Is this a reasonable
proposal? That's not to say it's going to end up here
at 10-5, but it seems and I think people agreed that
it seemed a reasonable value to go out for public
Will it end up there? We've given our
basis why. We'll see what the public comment says and
likewise, I think for the Committee and once again,
this will be the third time, but I still want to say
we apologize for not coming early on, but I think this
will give you a longer time to think through this.
It's our first cut. That's why we go out for public
comment and maybe 10-5, maybe there's a more
appropriate number, but we'll see what happens during
the public comment period.
MEMBER GARRICK: Any other comments from
audience or staff or anybody?
Okay, I think that satisfies us. Thank
MR. McCARTIN: Sure.
CHAIRMAN HORNBERGER: Thanks very much,
Tim. Anything that anybody wants to bring up that we
could accomplish in 10 minutes or should we break for
lunch adn reconvene?
So because John and I have a meeting with
Commissioner Merrifield at 1 o'clock, what I would
suggest is that Ray and Milt could get us started --
I don't know if either of you have read this yellow
letter, I haven't yet. But there are questions. The
big thing is to look through this research report and
try to come up with the key things that we need to say
in our research report. So my suggestion is you
should go ahead and have a read through that adn the
two of you could discuss it. That one and this white
one that Dick Savio handed around, research.
MR. SINGH: I haven't passed out the
research report yet.
CHAIRMAN HORNBERGER: Oh okay, so it's not
MR. SINGH: But I have copies.
CHAIRMAN HORNBERGER: Okay, so what I
suggest is Dick, why don't you give copies to Ray and
Milt and --
MEMBER LEVENSON: When will you be back?
CHAIRMAN HORNBERGER: Probably around
1:30. Okay? So we'll start our letter writing
session around 1:30 and we don't need to be on the
record at all this afternoon? Is that right?
So this will end the record keeping.
(Whereupon, at 11:54 a.m., the proceedings
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