111th ACNW Meeting U.S. Nuclear Regulatory Commission, July 20, 1999
UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
ADVISORY COMMITTEE ON NUCLEAR WASTE
***
MEETING: 111TH ADVISORY COMMITTEE ON
NUCLEAR WASTE (ACNW)
Conference Room 2B3
Two White Flint North
11545 Rockville Pike
Rockville, Maryland
Tuesday, July 20, 1999
The committee met, pursuant to notice, at 1:00 p.m.
MEMBERS PRESENT:
JOHN GARRICK, Chairman, ACNW
GEORGE W. HORNBERGER, Vice-Chairman, ACNW
RAYMOND G. WYMER, ACNW Member
CHARLES FAIRHURST, ACNW Member. P R O C E E D I N G S
[1:00 p.m.]
DR. GARRICK: Good afternoon. The meeting will now come to
order.
This is a continuation of the second day of the 111th
meeting of the Advisory Committee on Nuclear Waste. My name is John
Garrick, Chairman of the ACNW. Other Members of the Committee include
George Hornberger, Ray Wymer, and Charles Fairhurst.
The entire meeting will be open to the public. Today the
Committee will continue preparation of ACNW reports, and before that
we'll get an update on DOE Yucca Mountain repository design matters.
Andy Campbell is the designated Federal official for the
initial portion of today's meeting, and as usual, this meeting is being
conducted in accordance with the provisions of the Federal Advisory
Committee Act. We have received no written statements or requests to
make oral statements from members of the public regarding today's
session. Should anyone wish to address the Committee, please notify and
make your wishes known to a member of the staff.
The procedure if you wish to make a comment is to identify
yourself and speak clearly so that we can all hear the important message
that you have to say.
We're now going to move directly into the Yucca Mountain
repository design discussion. This discussion will be led by Committee
Member -- as far as the Committee is concerned -- Charles Fairhurst. So
with that, I guess we're ready to proceed with the first speaker. I
think that's going to be --
DR. FAIRHURST: Paul Harrington.
DR. GARRICK: And would each presenter introduce themselves,
say a little bit about what their role in life is for the benefit of the
Committee.
DR. FAIRHURST: You mean as far as DOE's concerned.
DR. GARRICK: You two must know each other.
MR. HARRINGTON: My role in life with respect to the DOE is
maybe not as interesting as some of the other roles I may play.
I am Paul Harrington. I am the DOE design lead for Yucca
Mountain activities. The way our organization is set up, Steve Brocoum
is the assistant manager responsible for regulatory activities, and Dick
Spence is the assistant manager responsible for actual production of
products doing work activities within the M&O. And I am the design lead
in Dick Spence's organization.
So I've been on Yucca Mountain about four years now, having
come from Rocky Flats, and the commercial nuclear world prior to that.
Before I talk, I'll say a little bit about where we stand in
this whole LADS process, though. We've broken this discussion up into
two sections. I'll give the process, how LADS came to be, what it is we
looked at, and what the several recommendations, enhanced design
alternatives were and a recommendation that's been made from the M&O to
the DOE. DOE has not acted on that yet. And Dick Snell will give a
more detailed discussion of what the enhanced design alternative to
recommendation really contains.
Now the M&O made an initial recommendation through Rev. 0 of
the LADS report in the middle of April, on the 15th, to the DOE. We did
a technical review, had comments on it that resulted in issuance of Rev.
1. That is the rev that the TRB and others have reviewed and made
comments to. We are still collecting review comments. We've not yet
made a selection or final decision on whether or not to proceed with
EDA-2 or something else.
DR. HORNBERGER: Paul, what's the time frame for making that
decision firm?
MR. HARRINGTON: Well, we have a TRB member coming to the
project Thursday, Friday of this week to try and talk about the
ventilation issues. I'm sure you've seen the letter that they sent us a
week or so ago, and they continue to be interested in a cooler
repository then EDA 2 looks like. So they're coming out to talk about
possible ways to achieve that. This is not going to be just DOE
presentations but much more of an interaction and listen to what they
have. That happens the end of this week. Lake will probably take that
into consideration and sometime fairly soon after that come out with a
conclusion.
DR. FAIRHURST: Who is the one -- which RB member is coming
out --
MR. HARRINGTON: Dan Bullen.
DR. FAIRHURST: Okay.
MR. HARRINGTON: And a staff member, Carl DiBello, with him,
and I don't know of any other board members that are coming.
As we were doing the characterization work, one of the
significant issues that came up were uncertainties with respect to
modeling not just the engineered but the natural systems also. So we've
looked at what can we do to reduce uncertainties. That ultimately led
to the LADS exercise.
Now there had been a number of proposals made from a lot of
different areas as to alternate designs that the project might pursue.
Some of them were fairly narrowly focused, like rod consolidation.
That's really something that could be applied to most any fundamental
design approach. And there were other more broad design approaches that
were proposed, including both cooler and hotter repositories. So the
attempt of the LADS exercise was to do a comprehensive assessment of all
of the different proposals that were on the table at the time or that
could be developed during this process to try and reach closure on what
a best-design approach might look like to us.
Now this was not intended to be a final design. As we go
through this, we'll see references to specific thicknesses of waste
package materials and drip shields and that sort of stuff. The
thicknesses there were for analysis. They're certainly subject to being
validated through the continuation of the design exercise that we're
doing from now to site recommendation, and then to LA, assuming that a
site recommendation is made.
In addition to trying to do that comprehensive assessment,
NRC Regs 60 and 63 require that we look at alternative designs. So
there were a number of drivers causing this.
As I said, we'll have to develop that further to support and
SR and LA. This is conceptual. The terminology that is contained
throughout the report addresses design alternatives and design features.
Design alternatives were the really fundamentally different approaches
we talked about a moment ago, such as a high or low thermal load. We'll
have lists of them a little further in the presentation. And then the
design features were the relatively minor changes that could be applied
to any inherent approach.
We had just issued the viability assessment prior to
starting this. This really started in July of last year. But in the --
or not but, but in the viability assessment volume II was the design
product, and section 8 of that had a number of different alternatives.
So that was one of the bases for starting this work, but we were not
constrained just to following that.
And if you guys have questions as we go through this, please
feel free to go ahead and address them.
DR. GARRICK: One of the things that I do have a question on
is if DOE has established a criterion or a definition of what
constitutes an alternative design, at what level of change does it
become an alternative design?
MR. HARRINGTON: As opposed to a design feature?
DR. GARRICK: Yes. Yes.
MR. HARRINGTON: Okay. A specific criterion, I don't
believe we have. As we look at what they are, you can kind of see how
we treated some versus others. And the treatment of one versus another
wasn't a major motivator in this anyway. It was an attempt to group
activities for alternative evaluation. Rather than looking at 32 or so
off the bat, we tried to identify which ones we thought, and again I
don't know that specific criteria were more fundamental and which ones
were less.
DR. GARRICK: Now has the Technical Review Board been
specific on what they mean by alternative designs?
MR. HARRINGTON: Not more specific than we have as I can
remember.
DR. GARRICK: Um-hum.
MR. HARRINGTON: They may have issued something, but not
that I recall now.
Dick, have you -- okay, Dick Snell doesn't remember
anything, either.
DR. GARRICK: Okay. Thank you.
DR. FAIRHURST: But they have -- the Technical Review Board
has sort of almost accepted your definition of alternative designs,
because they speak of them. They would prefer EDA 1 rather than EDA 2.
Right?
MR. HARRINGTON: Yes.
DR. FAIRHURST: So they have in essence said these are
alternative designs and they're willing to accept this.
MR. HARRINGTON: Oh, I think they're willing to accept our
definition of alternatives. I thought the question was had they come up
with their own definition or something more explicit.
DR. FAIRHURST: Oh, I agree. I'm not contradicting your
answer.
MR. HARRINGTON: Okay.
DR. FAIRHURST: I'm just saying that they have in essence
bought off your definition.
MR. HARRINGTON: Yes. I think they were reasonably
comfortable with what we had defined as alternative approaches. They're
not as comfortable with the recommendation that was made to the DOE
obviously.
DR. GARRICK: Yes.
MR. HARRINGTON: Okay. The LADS process went through
several steps. These next two pages enumerate those. We went ahead and
identified the objectives to use for developing the concepts, and then
we had a series of workshops. In early January there was a two-week
workshop to look at the analyses that had been generated for the design
features and design alternatives trying to find how we might then
structure those into a narrower set of fundamentally different
alternative approaches.
We used a consensus decision process, with the LADS core
team as the decision makers. Now, something that has come up a number
of times is the lack of a very numerical approach to this exercise, and
we weren't trying to do a numerical approach. It wasn't really of value
to us. We didn't think to try and assign a number, a rating of 83 to 1
approach versus 67 to another approach. All we are really looking for
was relative contribution to performance and to the other criteria that
we had. So that is another comment that the project has gotten, and we
will go further into detail in a moment.
DR. HORNBERGER: Amongst your criteria, ideas to consider,
how fundamentally do workshops identify changes? Did you consider
different tunnel diameters? Did you consider vertical emplacement of
the canisters and boreholes? I mean how far did you go?
MR. HARRINGTON: With respect to emplacement, we went back
to vertical borehole emplacement, horizontal borehole emplacement, short
cross-drifts rather than the long ones we have, putting packages into
trenches with a shield over them. We looked at larger and smaller
tunnel diameters.
There hasn't been much of a push to go larger. Actually,
that does provide some benefit if you are truly trying to limit the
temperature in the rock, though.
DR. FAIRHURST: You only want for the repository in them,
yes.
MR. HARRINGTON: Pardon me?
DR. FAIRHURST: I said if you only need -- if you just want
one to put everything in.
MR. HARRINGTON: Yeah. But we did consider going to a
smaller diameter in more detail than the larger, and did some scoping
analyses on the equipment size to emplace waste, to retrieve it
backfill, drip shield, and decided that we really can not significantly
decrease size. So we tried to look at a lot of different things.
This obviously has to be a documented basis to support what
we did. And I keep saying "we," again, this is the M&O process to
develop a recommendation to make to the DOE.
There was something called the LADIG, LA Design Integration
Group. In December we realized that there was a need for an overall
policy coordination group, something driven by the DOE, so we created
the LA Design Integration Group. It had senior members from both the
DOE and the contractor. It was chaired by Steve Brocoum, our AM for
licensing. It included senior members from the M&O staff, Dan Wilkins,
Jack Bailey was on it.
And the intent of that was to have a venue to discuss policy
issues. You may have heard that that was another issue that had come up
at the TRB meeting a couple of weeks ago was the -- there was a concern
that the M&O was creating policy decisions. That is what the LADIG was
there for, and there will be a revision to the LADS report that will
capture those LADIG policy issues.
One question I have for you. Have you folks gotten to see
the LADs report yet, or is this really pretty cold?
Okay. I apologize for that. We could have brought copies
out. I went ahead and gave the NRC site rep a copy, only about a week
ago though. So, obviously, it hasn't gotten distribution here yet.
Okay. I will keep that in mind as we are going through this thing.
So in the process, these are some of the things that the
LADIG looked at is, what is the decision methodology? There were
several different approaches we could have taken to that. One is a very
numeric rank ordered, here is what we looked at, here is how we assign
numbers to them. Here is the roll-up of that, and here is the only real
possible answer as a recommendation.
The other end of the spectrum was go out and evaluate these
different alternative approaches and provide the pros and cons of them,
but don't attempt to make any relative comparison, leave that to the DOE
to do, to incorporate whatever additional DOE criteria there may be.
We ended up in this LADIG group deciding to take a middle
course, which is to say do a relative comparison between the various
approaches and come up with a recommendation rather than being silent on
what a proposed recommendation might look like.
DR. HORNBERGER: You did a formal analysis, not an MUA, but
something else?
MR. HARRINGTON: Not an MUA, a paired comparison analysis.
DR. HORNBERGER: Okay.
MR. HARRINGTON: Yeah, we will go through that a little bit
later.
Let's see. We also talked about what were the evaluation
criteria to be used during Phase II. Now, Phase II was when we had
taken the design alternatives and design features of Phase I, had the
Phase I closure workshop meeting to define what we were going to look at
as structured enhanced design alternatives in the Phase II process. We
reassessed what criteria to use for that Phase II assessment and that
went to the LADIG for consensus.
The desired product, sort of a restatement of the first one.
The first was methodology. The third one is, what does the product
actually look like? The documentation necessary to support this.
And the next slide is really a graphic of the process. Oh,
I am sorry. I have been talking to --
DR. GARRICK: We are up with you, but you are not with
yourself.
MR. HARRINGTON: Okay, great. Okay. This is really a
graphic of the whole process. The first one we do the description of
the alternatives and features. We have talked through that. Much of
that came from the VA work.
Second was develop the evaluation criteria for that. There
is a slide a little later on that describes what that criteria was.
Third is then evaluate those alternatives and features.
The fourth was the workshop to develop the enhanced design
alternatives.
Fifth was develop the criteria that those would be assessed
against.
The next is then to do that evaluation and ranking of the
EDAs.
And the last is to come up with a recommended design. So
that is really what this whole LADS process did in a single graphic.
Okay. Again, for the Phase I, we took all of the design
alternatives and features and did analyses specific to each of those,
and two pages back, we will get to those. In fact, maybe I will just --
these next two slides are text of what we had here in a graphic form, so
I will just go through them quickly.
Again, the development, the January workshop, then EDA II or
the Phase II part in March. Did the comparative evaluation with
rankings, comparative rankings.
I wanted to have EDAs, Enhanced Design Alternatives -- let's
see -- that were fundamentally different. It goes back to just the
regular design alternatives, I'm sorry.
As much of a definition of what a design alternative versus
a design feature is, we are kind of capturing here. Okay.
DR. FAIRHURST: Before you get off these, you have almost
answered John's question. You said that is a fundamentally different
conceptual design.
MR. HARRINGTON: Yes.
DR. FAIRHURST: Now, what is fundamentally different between
EDA I and EDA II?
MR. HARRINGTON: Ph, temperature. The concern there, the
big issue, the big difference between I and II is keeping the rock
always sub-boiling.
DR. FAIRHURST: Okay. So a fundamental difference is below
boiling.
MR. HARRINGTON: In the rock.
DR. FAIRHURST: In the rock.
MR. HARRINGTON: Yes.
DR. FAIRHURST: Or above boiling in the rock.
MR. HARRINGTON: Yes.
DR. FAIRHURST: That's one.
MR. HARRINGTON: Yes.
DR. FAIRHURST: Okay.
DR. HORNBERGER: You know, the real fundamental difference
is spacing of drifts, right?
MR. HARRINGTON: Well, that just --
DR. FAIRHURST: Again, you know, this is -- you are testing
the argument. How fundamentally different is it?
DR. HORNBERGER: The argument itself, you could ventilate
EDA II for 300 years and keep the temperature down.
MR. HARRINGTON: Yes, we could. And it wouldn't even take
that long.
DR. FAIRHURST: It is not a fundamental -- you are right.
DR. HORNBERGER: That is a design feature.
DR. FAIRHURST: The thing that bothers me is fundamental, it
is not fundamental.
DR. HORNBERGER: The drifts are a different spacing.
DR. FAIRHURST: Right.
DR. HORNBERGER: They can't change that. So that is why it
is fundamentally different. I'm sorry.
MR. HARRINGTON: Oh, we can change drift space.
DR. HORNBERGER: No, no, no. But between --
MR. HARRINGTON: But the difference in concept --
DR. HORNBERGER: -- the two alternatives. Between the two
alternatives, one is that -- I forget how many meter spacing, and two is
a closer spacing. That is a difference that you can address with a
design feature. That is difference, if you mine it out, you can't
change it by ventilating or backfilling or anything else. The design
features you can apply to anything.
DR. FAIRHURST: No, if you want to, you can change it, you
can drive a drift between them. No, you can, George.
DR. HORNBERGER: Okay.
MR. HARRINGTON: What we were trying to get to --
DR. FAIRHURST: Or you can go from 81 to 40 and you are
still different than the VA design.
DR. HORNBERGER: I withdraw my comment.
MR. HARRINGTON: What we were trying to --
DR. HORNBERGER: I am sorry I asked the question.
MR. HARRINGTON: What we were trying to get to in EDA I was
something where you don't get into the vapor phase for in the rock.
DR. HORNBERGER: No, I know. I mean I know the result. I
was just -- I was quibbling with Charles.
MR. HARRINGTON: Okay.
DR. HORNBERGER: He and I like to do that.
MR. HARRINGTON: Okay. These are the design alternatives
that were looked at in Phase I. Now each of these and the design
features on the next two pages had analyses written against them that we
then used as the basis for the workshop in early January to try and
discuss how each of these met the criteria that were assigned, or that
we were reviewing them against.
So tailored waste package spatial distribution. Is there
some way we can orient or separate the packages in some manner that
would improve performance or give us some other benefit?
Low thermal load design, obviously, postclosure ventilation
system. That is something that continues to get interest. At the most
recent TRB meeting one of the professors from the University of Nevada,
Reno, made a comment that he thought we had prematurely terminated
assessment of postclosure ventilation, but let me talk about that one
for just a moment.
The concept there is that as long as you can pass air
through a drift, you can remove heat and moisture from a waste package.
If you can continue that in the postclosure phase, then there may be
some merit to it. We had a workshop that Nye County actually hosted in
early December looking at concepts. One was a flow from outside a
repository through and back outside. Certainly that would bring in dry
air, but you were left with the problem that the repository was not
isolated.
We looked at a couple of concepts for circulation within the
mountain.
DR. FAIRHURST: The bow tie arrangement.
MR. HARRINGTON: Yeah, there was the bow tie and there was
another one. And one of the big problems we had with that was trying to
prove that it would perform that function for a period long enough to be
of benefit in the postclosure world where you are really not having an
opportunity to monitor it or to act on it. That difficulty versus the
somewhat marginal improvement that we got in performance from it, as I
said, that didn't go forward.
Enhanced access design. We talked a moment ago about
packages and drifts in the floor. One of the concepts was, what happens
if there is a problem as you are moving a package in or if, while it is
in, you need to go into the drift and do some maintenance, or if you
have a retrieval exercise, you have maybe equipment failure or something
else, what can you do to the packages to make them more approachable,
primarily from a radiological perspective? So that was that one.
Modified waste emplacement mode design. There was the VA
design, we didn't want to simply discount the viability assessment.
There was a lot of good thought that had gone into that. And the VA had
some options that included backfill, drip shields and ceramic coatings,
and then a modular design in phased construction. That was more of a
surface issue we rolled into this to try and see how that would affect a
subsurface, but there was also some modularization of subsurface
construction besides.
The next one is design features. These are things that were
considered to be less fundamentally different and could be applied to
just about any of the basic design approaches. Ceramic coatings, drip
shields and backfills came out of the viability assessment as options.
Aging and blending of waste, certainly, the more you age it, the more
heat it is able to reject, the less heat you have to worry about in a
repository. Likewise, if you do blending of packages, you can better
control the thermal content of a waste package.
The VA design -- design basis, 21 PWR, had about 9.8
kilowatts per package, but the max was up at about 18 kilowatts per
package. With blending, you can keep that lower, avoid hot spots as you
go down through the drift length.
Rod consolidation, it was more of an issue than a
performance issue.
Timing of closure, if you can delay or accelerate, you may
have longer ventilation periods.
What do you have to do for maintenance of underground
features, particularly if you go to some extended period?
Drift diameter, that came up a little earlier. Spacing,
both of the drifts and of the waste packages within a drift
Self-shielding of waste packages. We looked at other shielding
approaches to waste packages, including trenches. There was a clam
shell approach where the shield was separate from the waste package but
could be applied on top of it. Corrosion-resistant materials, different
materials than have been looked at in the VA.
A Richards barrier, that is a two grain backfill material.
The intent is to cause water to wick down at the interface between the
two. We actually did a test on that out at our ATLAS facility on
Russell Road, you may or may not be aware of.
DR. GARRICK: Yes, we are aware of that.
MR. HARRINGTON: Okay.
DR. GARRICK: Did you have the results from it yet?
MR. HARRINGTON: I don't. Dick, do you know what we have
gotten?
MR. SNELL: Dick Snell with the M&O. I was going to say
they did find one thing, you have to be careful selecting the grain size
and the materials in the two layers, because the first one picked, the
water went right straight through the -- excuse me, the fine grain
material went right straight through the second layer. They had no
barrier between the two layers of material. But they are doing tests
now with dissimilar materials, two layers, and we do not have yet any
conclusive results. It does seem to be performing as anticipated, that
is, it is causing materials to move -- water to move at the interface
between the two materials, to the side. Water is not getting down into
the lower backfill material. But no firm conclusions as yet.
DR. FAIRHURST: You are also doing a heated test, aren't
you?
MR. SNELL: The heated test is to begin shortly. It is set
up for temperature testing and I believe -- I think within a matter of a
few weeks that test will begin.
DR. FAIRHURST: Okay.
DR. GARRICK: Paul, in your evaluation or approach to
evaluation and the factors you consider in the evaluation, one of the
things that there was always been a lot of talk about on this project,
because of its magnitude and its long duration, is the finding of a way
to be flexible and change the direction, even after the so-called design
is frozen.
MR. HARRINGTON: Yes.
DR. GARRICK: How much is -- and, of course, the regulators
are wrestling with that whole issue as well, because that is a difficult
one to factor into the regulatory process. But, nevertheless, there is
a certain amount of sympathy because of the nature of the project
towards that. How much is flexibility in the design, how much is that
entering into the evaluation process itself?
MR. HARRINGTON: Greatly. That was one of the four major
sets of criteria for the EDA II evaluation.
DR. GARRICK: Yeah.
MR. HARRINGTON: There are several subcriteria on that.
DR. GARRICK: Are you trying to quantify that when you do
your evaluation?
MR. HARRINGTON: Yes, we did assign a number to it, but the
number is really relative performance between EDA approaches, not to say
that a number 2 equates to some measurable item, but number 2 or a rank
of 2 with respect to flexibility means that one EDA is more or less
flexible than another.
DR. GARRICK: Yeah. Well, the thought here, of course, is
that as you get further down the road and as you do more field studies,
more R&D, learn more about the design, you may reduce some uncertainties
about some of the design features, for example, and decide that there is
just not a good return on them, and you would either like to be able to
eliminate them or change them or what-have-you, such as a Richards
barrier or such as a drip shield.
MR. HARRINGTON: Yes.
DR. GARRICK: Because I think that some of these things come
out of people's mouths awfully easy, like drip shields, but when you
stop and calculate what is involved, not only in materials and costs,
and installation and what-have-you, but the whole support effort that is
involved, you know, we end up with huge numbers.
So I would think that would be an extremely important
consideration.
MR. HARRINGTON: Yes. When we get to the rankings of
different EDAs, that was one of the things that caused EDA I to be moved
down, because of the area that it would take, being a low thermal load.
DR. GARRICK: Right.
MR. HARRINGTON: It takes up all and then some of the
repository block if we are also looking at possibly having to put more
than 63,000 MTU commercial in there. So it was one of the less flexible
ones. I think it is actually the least flexible.
DR. GARRICK: All right.
MR. HARRINGTON: Let's see, these are just some of the other
features. I probably need to be moving on here.
These are the criteria we used for the Phase 1 evaluations
of these design features and design alternatives. Pre- and postclosure
performance, assessment assurance of safety, construction ops and
maintenance, et cetera. And also our confidence in the above
assessments.
We've been doing a lot of work to try and identify just what
are the areas that the project thinks we have less confidence in and
what are the areas that we think would drive performance more or less
and use that coupling to allocate resources for what it is we do in the
future.
The DOE concluded an exercise, scoping exercise in that vein
about two months ago. The M&O's working up their enhanced version of
that, and I have not seen that final yet, but we spend a lot of our
focus to make sure we're working on the right things.
DR. WYMER: Is dose kind of a washout in all of this?
MR. HARRINGTON: Yes. Yes, when we get to the EDA 2, you'll
see -- actually I didn't put them in here -- but we did curves for
10,000-year and million-year releases for each of the five EDAs, and all
five of them perform real well at 10,000 years, but one of the EDAs that
has a carbon steel liner waste package material fails sooner after the
10,000 years than all of them with CRMs. So especially for the
10,000-year period, dose really was not a discriminator.
Okay. So we did the workshop, and that was to look at
everything that had been done in these analyses for the design features
and alternatives to figure out how could we structure a set of enhanced
design alternatives to then evaluate to try and make a recommendation
from. So the intent of these, these enhanced design alternatives, was
to capture several fundamentally different approaches that were not just
one offs, which is what the Phase 1 part had been, but that would be a
reasonably complete design approach. So within these enhanced design
alternatives, we mixed and matched different -- some design alternatives
and design features to come up with a design approach that was more
fully developed.
When I said one off a moment ago, what we tried to do was
look at each of the design alternatives and features in the Phase 1
process as that one item compared to the VA design just to try and make
a more manageable comparative exercise. The intent of the enhanced
design alternative was actually to structure more complete design
approaches that would be relatively different from each other.
Now we came up with a couple of approaches to
low-temperature designs, a couple to high-temperature designs, and some
enhanced-access designs. We then decided that -- there were eight in
that first cut, and that was a little too many. Some of them weren't
really fundamentally different, so we scrubbed it down to five.
This is the EDA discussion here. We did general sessions to
review it. We had performance assessment and cost folks there to get
some idea of the performance contributions of each of these things, and
also relative costs. Did some design analyses. Wanted to know surface
doses as we were changing waste package materials and thicknesses, for
example. Obviously the dose outside the waste package changes. And
that then came up to be the set of EDAs. I'll put this up here. I
think you will need to refer to your handouts, though.
Now EDA 1 was really the low-temperature design. The
fundamental feature there is to keep all of the rock below boiling, stay
out of the vapor phase water in the rock. This particular design
construct does allow the waste package itself to exceed boiling, though.
There are a couple of versions of what a true
low-temperature design would be. One of them says that you keep the
waste package itself also below boiling, and I think the end of that
spectrum says that you keep the waste package below the point that you
would have corrosion other than general corrosion on it. So that would
be from a waste package of 85 C to a waste package of 96 C to a rock
temperature of 96 C. Those are sort of the three stages of a
low-temperature design cooler than EDA 2 is.
Reading down through that, the aerial mass loading is 45 MTU
per acre. So for 63,000 MTU of commercial SNF, plus the DOE SNF and
high-level waste, that would take 1,400 acres.
Now it says point loading. What that means is the waste
packages have some spacing between them that's dictated by the thermal
content of the individual waste package. The other ones are line
load -- that means the waste packages are butted up to about 10
centimeters apart. Basically they are as close as we can reasonably
emplace them doing a remote exercise.
We limited the waste package size to limit the thermal
content of the package. There are 12 PWRs and 24 BWRs. Still, though,
with the 5-1/2-meter drift diameter, one of the things that we find as
we try and shrink the drift diameter is not only do you have less room
for emplacement equipment and other equipment to work, but because that
rock is closer to the package, it gets hotter than it would if it were a
little bit bigger. This has a 43-meter drift spacing.
And all of them we tried to have a 50-year closure period
taken as from time of start of emplacement to closure. Now that's
something that we need to do more work on, because the actual analyses
that we did were based upon all of the inventory being emplaced at once
halfway through the emplacement cycle and, yes, that was just to make it
numerically a little bit simpler, and then taking a 50-year cooling
period on that. So the intent is to be able to close it at 50 years
from start of emplacement in each of these EDAs, but we need to do a
little more analysis to make sure that we can do that and that the
ventilation rates that we're proposing do that.
So this says 2 to 10 cubic meters per second per drift for
that 50-year period. We're really up toward the top end of that, and
we're closer to 10 than we are to 2, especially in EDA 2. And it has
20-percent blending to keep the waste package thermal content down from
the 18 kilowatts that the 21 PWR could have had with no blending. This
is limiting it down to 6.7 kilowatts in these smaller packages, the 12
PWRs. But it also is requiring blending to get there. And the waste
package material is 2 centimeters of alloy 22, nickel-based material
over 5 centimeters of 316 stainless steel.
Now these thicknesses certainly are subject to change
through validation, through completion of the calculations that we'll
do, but that's what was used for the basis of this LADS work. It does
not have filler within the packages. It does not rely on backfill. It
does have a drip shield. Titanium, grade 7, at 20 millimeters was
considered for all of them. And because of the smaller packages, then
the number of packages went up to not quite 16,000. Okay?
EDA 2, the intent there was to get an appreciably lower
thermal goal than the viability assessment, but not to drive it as low
as EDA 1 had to allow some of the rock to be above boiling. But to keep
a space at the center of the pillar between drifts where it would always
be subboiling, and that would then provide a channel for flux to come
down and then drain between drifts.
One of the concerns in modeling flux was if we had an
above-boiling isotherm across multiple drifts, what would that do to the
water? Would it stay up? Would it find fractures? Would it do
something else? So doing this we thought took a significant chunk of
that uncertainty out by providing a relatively large subboiling region
where water could relatively freely drain.
DR. FAIRHURST: Paul, on that --
MR. HARRINGTON: Yes.
DR. FAIRHURST: And it's somewhat of a technical point, but
even though you've got the region below boiling, the rock is heated up.
MR. HARRINGTON: Yes.
DR. FAIRHURST: And therefore you are closing apertures to
total thermal expansion. Just by keeping it below boiling doesn't mean
to say that you've got an open pathway in the middle.
MR. HARRINGTON: Yes. You certainly would have the
mechanical aspects of that, but we would get away from the vapor phase
problem with the water coming down through there. So -- see, this --
DR. HORNBERGER: You don't have vapor. You don't get away
from the vapor phase.
MR. HARRINGTON: No, you don't.
DR. HORNBERGER: You just don't boil water.
MR. HARRINGTON: Well, okay.
DR. FAIRHURST: That's right. When you get thermal
expansion --
DR. HORNBERGER: I mean, your humidity is going to change,
and so you are still going to evaporate water, you're just not going to
boil it.
DR. FAIRHURST: That's right.
MR. HARRINGTON: Okay.
DR. HORNBERGER: And so you still see --
DR. FAIRHURST: So this is -- see, this is this question
about not taking into account discrete fractures.
DR. HORNBERGER: Right. They're still going to --
DR. FAIRHURST: Because you close those fractures.
DR. HORNBERGER: They're going to close. Above.
DR. FAIRHURST: Because the rock's expanded.
DR. HORNBERGER: That's right, above the --
DR. FAIRHURST: Lineally with temperatures, not going to --
and there's nothing magic about going above and below boiling.
DR. HORNBERGER: Right. Right.
MR. HARRINGTON: The degree of closure would be thermally
driven; right?
DR. FAIRHURST: Yes. It's not quite lineally, because the
stiffness -- there's a residual aperture in a joint that you can't
close.
MR. HARRINGTON: Okay.
DR. FAIRHURST: Anyway --
MR. HARRINGTON: So doing this, though yes, it does still
heat up and yes, there will be some --
DR. FAIRHURST: It's better if it's -- temperature, right.
MR. HARRINGTON: It's lower than it had been in the VA.
DR. FAIRHURST: Right.
MR. HARRINGTON: Now this says we want to keep the center of
the pillars below boiling. In reality, in looking at the numbers that
we've run so far with this particular spread, about 80 percent of the
pillar is subboiling. So by the time I get to the center of it, it's
appreciably below boiling.
Because this is 60 MTU per acre, it takes somewhat more
footprint than the viability assessment design. So we're up to 1,050
acres. That would just about fit within the upper block of the
currently characterized area. Now we also have the lower block
available, too. Again, that's just for the 63,000 MTU commercial,
though. This is going to line loading.
Now, something to point out there with respect to drip
shields, I mean yes, we do talk about some of these things as if they're
fairly simple, and they're going to be far more complex than that. In
the point loading, the concept of a drip shield was that it was a
breadbasket. It would sit over an individual waste package and it would
have ends on it.
When you have the waste packages in a line load, there's
really no space to have a drip shield come down across each end, and you
don't want that, because you're trying to get thermal transmission in
between adjacent waste packages. So the concept here is to have the
adjacent sections of this continuous drip shield overlap each other.
Now obviously we have to model what will happen with water potentially
coming through that joint, but it's just something to keep in mind in
this line load concept and drip shield versus the point load.
We are back up to the 21 PWR, 44 BWR though, we can go with
the larger packages. This is the VA size package, so it doesn't result
in an increase in the waste package number, again, with 5-1/2 meter
drift, but the drift spacing now been increased to 81 meters to try and
provide that relatively cool zone in between drifts.
The 9.8 kilowatts is a design basis, is the same as the VA
essentially, but now we have got blending in there to limit the hottest
package to no more than 20 percent over that. We don't have the 18
kilowatts per package from the viability assessment design.
The same construction as for EDA I, no fillers but with
backfill over the drip shield, and we are back down to a little over
10,000 waste packages.
DR. HORNBERGER: Is the backfill just generic backfill tuff
or to do you have getters or chemical things in there?
MR. HARRINGTON: We are considering two different backfill
materials, generally. One is a crushed quartz sand, I think, and the
other I think was a tough. We did consider getters and stuff as some of
the design features in the EDA I.
DR. HORNBERGER: But they are not here.
MR. HARRINGTON: No. No. One of the concerns with them is,
would they still be there and able to function when you needed them?
You know, at the point that the waste packages would finally start
failing and you start actually releasing material, would that getter
that you placed really be there?
EDA III is the most similar to the viability assessment
designs, and we have two versions of that, A and B, and the only
distinction between them really is the waste package material. So if we
jump down toward the bottom of the page, you can see that A has to the
two centimeters of Alloy 22 over the five of stainless, but B has a
three layer material with titanium sandwiched in between the Alloy 22
and stainless.
The thermal goals for III were the same as for the viability
assessment. All of these were trying to protect the cladding on the
fuel so they have a 353 degree C clad limit. This one tries to get the
waste package to cool down to 80 degrees C before the relative humidity
comes back to 90 percent. On the curves that we did, we defined the
window of susceptibility of materials, and that is temperature-humidity
driven, and if we can keep the waste package temperatures out of that
region, then we expect to have enhanced waste package life. So EDAs
III, IV and V were not as successful in staying out of that region as I
and II were.
This is back to the 85 MTU of VA design, so it took the same
740 acres that the VA did. Line loading, though, instead of the point
load. Again, 21 PWR, 5-1/2 meter. This is up to 56 meter spacing,
though, the VA design at 28 meters spacing between drifts. Again, with
the continuous ventilation during a 50 year preclosure period. It says
limited blending, that is just simply to not exceed 18 kilowatts in the
hottest package. The reference is still 9-1/2 for the 21 PWRs.
We talked about the materials a moment ago. No fillers, no
backfill, it does have a drip shield. And this is also slightly over
10,000 packages.
EDA IV was the concept that was taken forward as the most
likely shielded package. Rather than trying to deal with unshielded
packages and in a shielded environment like a trench or a short
emplacement drift or something like that, or a shield that was placed
over the package after the package was placed, all of those had real
operational difficulties in that you weren't really protected while you
were working on the waste package itself, while you were doing the waste
package emplacement. They were all sort of after the fact exercises.
So to get the true benefit from shielding, we decided that the package
itself ought to be shielded.
So this one, the big difference here is it is 30 centimeters
of carbon steel. Okay. That brought the gamma levels down to I think
it was couple of hundred MR per hour. The numbers are in there. But it
was appreciably less than the other ones.
Just as a point of reference, the VA design was about 20 R
per hour or 20 to 50 R per hour and the EDA II design, because it is
thinner, is about two or 300 R per hour. So this one was to get it down
to a much more manageable level.
In 200 degrees C on the drift wall, the intent there was to
let it head up, to use that to keep the drifts dry for thousands of
years. Okay, it has got 200 MR per hour on here as the primary goal of
this EDA IV. 85 MTU, same placement or same density as VA. Line load,
this also is a 56 meter drift spacing.
Pardon me?
DR. WYMER: You are saying R per hour.
DR. FAIRHURST: He was, on the other designs.
MR. HARRINGTON: Yes, this one is 200 MR per hour. The
others -- the other EDAs, except for EDA IV, are two or 300 R per hour.
Again, a little bit of blending to make sure we don't exceed
18 kilowatts per package. This does have an integral filler to it, it
does have backfill and drip shield. Because these are 21 PWRs, it is
also a little over 10,000 per.
EDA V was an appreciably different concept. That says heat
might be advantageous in that, if it drives water off, and can keep it
away, then you can keep drifts dry and promote or extend waste package
life. So this is appreciably hotter than the other designs. It allows
the drift wall to go up a little bit, from 200 to 225 C, but it is now
up to 150 MTU per acre. Because of that, it takes less acreage. One of
the thoughts associated with this one was, since it is appreciably
smaller, we might be able to find some more advantageous section of rock
to locate it in. That would have been pursued more if we had gone
further with EDA V.
Line loading, drift spacing is now down to 32 meters between
drifts, again, trying to keep it hotter. To avoid hot spots, though,
within a drift, there is blending so that you don't have exceptionally
hot packages as you go down the length of the drift. So we are back
down to the 11.8 kilowatts as a max, 20 percent over nominal.
DR. FAIRHURST: All of these calculations were done with
fresh waste, right? There was no aging considered?
MR. HARRINGTON: I believe that there was some aging
considered. The fresh waste would have given us the 18 kilowatts per
package. So the 9.8 is assuming some aging. I don't remember just how
much, but the design package of 18 is about where we would be if we had
all five year old fuel.
DR. FAIRHURST: So the blending is age of waste as well as
type of waste?
MR. HARRINGTON: Oh, that's -- I'm sorry, I wasn't clear
earlier. That really is age of waste. This is all commercial SNF that
we are talking about here, it is not the DOE SNF or the high level
waste. I will talk about that in a second. This is just commercial, so
it is as fresh as five years and, if so, if we had a 21 PWR with five
year old fuel, it would be 18 or a little bit higher in terms of
kilowatts. We recognize that some of what we get will be older than
that, so this blending here really was referring to taking cooler, older
fuel, mixing it in with hotter, newer fuel.
DR. FAIRHURST: Okay.
MR. HARRINGTON: Now, this whole discussion really is
focused on commercial SNF. The approach for DOE SNF and high level
waste is to use co-disposal packages. They are physically about the
same size as the commercial packages, they are about 2 meters in
diameter. These 21 PWRs are 1.6 or 7 meters diameter, and they are all
about 15 feet long. The DOE fuel and waste are both very cool so they
don't figure into the thermal calculations, so as we do these
calculations, that is just using commercial stuff. The intent with the
DOE material is just to space it in between the hotter commercial
packages.
Because of the 21 PWR we are still a little over 10,000
packages.
What was common to all of these? They all had a drip
shield. They all had carbon steel ground support. One of the VA
designs -- well, the VA design had a concrete liner to the drift. That
came about several years ago, about three, three-and-a-half years ago
when we recognized the need for a very robust low maintenance solution
to ground control in drifts that were not going to be able to be
accessed very readily, once waste gets emplaced.
Since then, over the past year or so, in looking at not just
the engineered but the natural system modeling, we have identified that
there were some issues with water flowing through that concrete, its
effect on the PH of the water, and then on the waste package integrity.
So going away from the concrete liner removes that uncertainty, and
right now we are looking at carbon steel.
We had a couple of meetings with a drift stability panel,
one in December and another one this spring, to look at different
approaches to doing that, try and identify just what the mechanisms
would be for the drifts to become unstable. And I asked them, as a
secondary question, what an appropriate set of ground support might be
for that. We are taking that report under advisement, along with some
other input that we have got. We haven't reached a conclusion.
See, all of these had 5-1/2 meters. They all have
preclosure ventilation, they do not have postclosure ventilation. This
is all for 70,000 MTU. This is 63,000 worth of commercial, and the
7,000 remaining is two-thirds DOE high level waste and one-third DOE
spent fuel. And they all have a steel invert with a granular ballast of
some sort.
These were the variable features among those. The thermal
goals. What were we trying to accomplish? Did or didn't we use
backfill? What materials was waste package made of? How much, if any,
thermal blending was required? The spacing between the drifts and of
packages within a drift. And what the location was within the
characterized area?
Constraints that we tried to apply to all of the EDAs were
that we protect the commercial cladding. We didn't see any reason to
purposely damage it. There are certainly some issues as to how well
characterized is it. How well does anyone know what either existing
failures or incipient failures might there be, and how much credit we
might be able to take for that? Setting that question aside, we simply
didn't see any reason to knowingly do something that would compromise it
beyond whatever it might be right now.
We also had to have the ability for personnel to access
these waste packages for off-normal events, either maintenance or some
DBE. For the non-shielded waste package, the concept there is simply
that you have to bring in portable shielding should you work in a drift.
Certainly, the first approach, say, if you had drift maintenance to do,
would be to unload the drift so you could go in unrestricted. If there
were a problem, if the equipment had broken or you had a rockfall or
something such that you couldn't unload it, then you would have to go in
with portable shielding.
DR. WYMER: At one time you were talking about 300 years,
now you are talking about 50.
MR. HARRINGTON: That is the difference. This is a
constraint. We wanted to have a design that could be closed at 50
years.
DR. WYMER: Why?
MR. HARRINGTON: Institutional control. For us to come up
with a design that had to stay open 300 years really presumes a lot for
future generations.
DR. WYMER: You must have known that when you selected the
300 years.
MR. HARRINGTON: We didn't select it. No, what we said we
were going to do is come up with a design that could be closed
relatively soon, 50 years, or it could be left open if people chose to
do so.
Now, we didn't want to come up with a design that had some
inherent feature that would prevent people from continuing to monitor,
if they chose to do so, but rather would be relatively maintainable for
whatever features might be necessary. So that is really the difference
between the 50 and the 300.
That is one of the concerns about looking at extending the
preclosure ventilation period for EDA II, if you then end up with a
repository that has a minimum life of 125 years versus something that is
more controllable.
Now, these next several slides go through in text what we
talked through from the table.
DR. FAIRHURST: Well, I think, you know, we have seen -- we
are pretty much familiar with the EDA I through V.
MR. HARRINGTON: Okay. Do you want to skip through this?
DR. FAIRHURST: So why don't we just jump over that?
MR. HARRINGTON: Great.
DR. FAIRHURST: At least we have them here for reference.
MR. HARRINGTON: Okay. There were five EDAs. As we looked
at them, we thought that all of them actually were viable. They all had
good releases, especially through the 10,000 year expected regulatory
performance period. That is the second bullet, they all met that
criterion. They all had defense-in-depth. One of the criteria we
looked at was the extent of defense-in-depth, and that was defined in
part as the number of separate features within a design, and they all
could be closed as early as 50 years from start of emplacement.
And I will put the same caveat on this bullet that I
mentioned earlier, the analyses were based on 50 years ventilation, so
we just need to work this issue.
What were the criteria that we used to evaluate it? They
had to be consistent with the repository design objective. We got to
multiple subcriteria to try and better define just what it is we were
looking at within the larger ones, and again because we were not trying
to do this multiattribute utility analysis, we didn't go to the point of
saying that they had to be mutually exclusive or comparable within
criteria, that sort of thing. That wasn't really what we were trying to
do with it.
They were there so that we could have a consistent set of
information and judgments across each of the EDAs, and to provide a
basis for this pairwise comparison that we spoke about a little earlier.
Again, there was no numeric score assigned to them.
Okay. These are the criteria. The screening one was simply
did it meet the regulatory criteria, and certainly that's still
proposed. EPA has not acted on it, but what we used was the 25 MR per
year at 20 kilometers over 10,000 years. Each of the bullets within the
criteria boxes under the main relevant factors, those were all
subcriteria.
So for each of them, we looked at the five EDAs and did a
paired comparison to say does this EDA perform better or worse than the
other EDAs with respect to each of those bullets or subcriteria. We did
a numerical ranking on a 1-to-5 scale, but again the intent was not to
say that a 5 assigned to degree of defense in depth meant the same thing
as a 5 assigned to maintainability. They were simply relative within a
particular subcriterion.
Now you had a question earlier about flexibility. Obviously
that was important to us. The first subcriterion was increased disposal
capacity. The 87,000 MTU comes from the total amount of SNF that we
project would be created if all of the licensed plants ran to the end of
their license lives. The 105,000 MTU commercial comes from having half
of those plants have 20-year life extensions. These are the same
numbers that the EIS used, so for the EDA or for the LADS exercise, we
wanted to be consistent with that and look at how would each of these
perform if we had a greater inventory to work from.
Now the --
DR. HORNBERGER: Was there any consideration given to this
phased or modular construction? That is, are any of these EDAs more or
less friendly to, say, construction on a phased basis, where you could
anticipate design changes from module to module underground?
MR. HARRINGTON: We looked at that somewhat in the Phase 1
of this and found that it wasn't really much of a discriminator. All of
them we thought, given that you're going to buy waste packages over a
long lifetime, they all could pretty much be made to suit whatever
design modes might come around.
Preclosure period, this says 10 years. The reason that says
10 years is a year or so ago OCRWM headquarters in our highest-level
requirements documents put a requirement in there that the repository be
able to be closed 10 years after emplacement of the last waste package.
That was driven by a consideration as to how long it might take us to
get enough data from performance confirmation to make an adequate case
to request closure. We're removing that because all of these require
enough ventilation that a 10-year preclosure or postemplacement closure
period really just isn't enough, and it didn't have much of a basis to
start with.
DR. WYMER: But I'd be safe in assuming that you were
looking ahead, and doing all this looking ahead to how to write your
environmental impact statements, you discovered that there wasn't much
difference among these various approaches that it made any difference?
MS. DEERING: Roy, would you use the microphone, please?
DR. WYMER: The question was, and this is sort of leading
into the next presentation, which deals only with EDA 2, but when you
were doing all this work, I presume you looked ahead to the time when
you were going to have to write an environmental impact statement and
get it accepted. Did you discover that -- and I would assume you might
have -- that there was not enough difference in the environmental
impacts from one to the other that that wasn't a consideration?
MR. HARRINGTON: No. We spent a lot of time coordinating
this with the EIS preparers. As you know, we're getting close to
issuing the PEIS. And when we set up the EIS a couple of years ago, we
tried to identify what the bounding designs might be, and at the time --
and we still think that that's really driven by the thermal load and the
AML per acre, the areal mass loading. So in the EIS, 25 MTU per acre is
the lower bound. We had an upper bound. I don't remember offhand what
that number was. I think it might have been 85. Now certainly one of
these is higher than that. And there was a middle range of 50 or so. I
don't know.
DR. WYMER: All of these other factors like the number of
packages you had to load in and that kind of stuff.
MR. HARRINGTON: We thought that would be bounded by the AML
thing. Certainly amount of excavation. With the real low environmental
impact statement lower-bound design, I think that even used smaller
packages, just to try and keep the temperatures down. So that would
have picked up the larger number of packages that EDA 1 has.
DR. WYMER: Okay.
MR. HARRINGTON: So the brief answer is yes, we did this in
conjunction with the EIS, and we think it's consistent with it.
Let's see, design changes hot to cold. If we wanted to take
a hotter design and move it to a colder design such as taking EDA 2 and
moving it to the goals of EDA 1, could you do it? And also, the other
direction, blending backfill, unanticipated features.
I'm afraid that I'm about out of my time here, and I've got
a couple more pages. So if you have other questions on this one, I'll
be happy to --
DR. FAIRHURST: I think it would be best to move on.
MR. HARRINGTON: Okay. Great.
Okay. Again, we did the comparative evaluation simply to
rank them against each other to come up with a recommended design. The
pairwise comparisons and the inputs were -- everything we had done after
creation of the EDAs in mid-January to this March exercise.
Now under the four major evaluation criteria, here's the
relative ranking of each of those.
Under performance certainly because of its cooler attributes
EDA 1 we thought would have the highest demonstrable performance,
followed by EDA 2.
DR. HORNBERGER: So that means you agree with TRB's basis.
MR. HARRINGTON: With respect to nothing but performance,
yes, we agree.
DR. HORNBERGER: So you agree that a cooler repository is
simpler to analyze and you have greater confidence in your analysis.
MR. HARRINGTON: Yes. But the rest of this says that EDA 1
has other not so positive attributes. Under flexibility, because it
took the largest volume, and in fact if you looked at the 105,000 MTU
potential, it doesn't even fit within the repository block. It also has
smaller, more expensive because there's more of them, waste packages.
So under construction, operation, and maintenance EDA 1 is relatively
low. EDA 4 is a little lower, just because of the much heavier
packages; 5 got the best one because there was less excavation involved.
Under cost, the first line has several of them on there,
because they're all about the same. The life-cycle cost for each of
those range between 20.0 to $21.7 billion. EDA 1 was $25.1 billion. It
was about $4 billion extra. That's why it was separated from the
others.
DR. FAIRHURST: That cost -- what's that the cost of?
MR. HARRINGTON: That's the repository life cycle cost.
That doesn't include the transportation.
DR. FAIRHURST: No. No, no. Okay.
MR. HARRINGTON: That is, though --
DR. FAIRHURST: But the construction cost is about what, 25
percent of that, right?
MR. HARRINGTON: Oh, I don't remember just how much --
DR. FAIRHURST: From the VA, at least, that's the ballpark
figure, what it was, I think.
In other words, what I'm saying is that the actual cost of
constructing these is not that large. A lot of other things affiliated
with that cost.
MR. HARRINGTON: It may have been 25 percent.
DR. FAIRHURST: Handling, et cetera, et cetera.
DR. HORNBERGER: I think it's a smaller package, isn't it?
MR. HARRINGTON: Well, the big contributors to this one
being more expensive is the increased number of packages. When it's
4,000 packages more.
DR. FAIRHURST: Yes. Underground construction, play around
with these designs, as distinct from what you put in, is nothing like
these numbers.
DR. HORNBERGER: Right.
MR. HARRINGTON: Number 1 also has a lot more drifting. It
has more than twice the amount of drifting of the other ones.
The recommendation was made not using an explicit
value-based model, but trying to consider consistency in ranking across
them. If you had one that performed real well in one spot but did
significantly worse than others in every other criterion, it might not
be your first choice. And the opinion of the M&O in making --
DR. WYMER: The weight is equal on each of these four.
MR. HARRINGTON: We did not try and make an equal weight.
DR. WYMER: Yes, but that has to be a qualifier of what you
said.
MR. HARRINGTON: Yes, that's true. That's true.
DR. WYMER: Okay.
MR. HARRINGTON: Again, with respect to performance, we
think all of them would give a very good 10,000-year performance. Now
in the post-10,000-year period, the EDA 4 fell off quicker than the
others simply because it was carbon steel. It didn't have the
corrosion-resistant materials that the others do. In the report, and
I'd be happy to make copies or however we can do it today if you'd like,
we have curves in there, performance curves of predicted releases for
10,000-year and million-year. And the million-year was to pick up the
peak release. But --
DR. HORNBERGER: You just did that for a base case, Paul, is
that right?
MR. HARRINGTON: For a base case?
DR. HORNBERGER: For -- you just --
MR. HARRINGTON: For each of the --
DR. HORNBERGER: One set of parameters and consistent from
one to the next.
MR. HARRINGTON: Yes. Basically as defined on that chart
that we had, the comparative chart, it was done based on that.
DR. HORNBERGER: Yes. But, I mean, your performance
assessment has a lot more parameters --
MR. HARRINGTON: Certainly.
DR. HORNBERGER: Than are on your chart.
MR. HARRINGTON: Certainly.
DR. HORNBERGER: You just picked a fixed set of them.
MR. HARRINGTON: Yes.
DR. HORNBERGER: Yes.
MR. HARRINGTON: And the curve is also the expected case.
DR. HORNBERGER: Yes.
MR. HARRINGTON: It's not the tails.
DR. HORNBERGER: It's not your expected case in a
statistical sense. It's some base case because you picked some default
values of parameters. In other words, you didn't run 3,000 runs and
find the median and say that's what you're going to present.
MR. HARRINGTON: Right. Right.
These next several bullets are things we've really talked
to. EDA 2 was comparable to the other ones for construction ops and
maintenance.
DR. FAIRHURST: Your table probably summarizes it.
MR. HARRINGTON: Yes. Okay.
DR. FAIRHURST: Now let me ask a leading question. Did you
show this table to the TRB?
MR. HARRINGTON: This table comes out of the report.
DR. FAIRHURST: No, I've seen copies of the latest letter,
and it said that the process by which you selected things was not
sufficiently transparent.
MR. HARRINGTON: We have presented this process to them. In
fact, these two presentations were basically excerpted from what we told
them two weeks ago. So, yes, they've heard the presentation, they've
seen the report --
DR. FAIRHURST: Did they point out to you what was missing
from here that would make it sufficiently transparent?
MR. HARRINGTON: Well, what they're really telling us, I
think, is that there's an appreciable benefit to reduction of
uncertainty by staying underneath boiling --
DR. FAIRHURST: In other words, they're saying that there's
not enough information to get rid of EDA 1.
MR. HARRINGTON: That's right.
DR. FAIRHURST: All right.
MR. HARRINGTON: That's right. So this is really a
synopsis --
DR. FAIRHURST: Um-hum.
MR. HARRINGTON: Of the performance factors versus the EDAs.
Across the top is the releases. That margin is simply the release, the
maximum release within 10,000 years divided by the 25 millirem. All of
them were driven by one waste-package failure, a juvenile failure in the
10,000-year period that happened to be underneath a corresponding
failure in a drip shield.
As you look at the curves, it doesn't come across so well
here, but the 290, 310, 300,000-year -- well, that's time to 25 MR. As
you look at the release curves, you'll see the blips on there from the
superpluvial periods, and when we identify where the peak releases would
be, it certainly corresponds with the superpluvials generally.
DR. HORNBERGER: Okay. So looking at this table it would
be -- I guess this is what Charles said -- but it would be fairly hard
to favor EDA 1 over EDA 2. And so the argument, as you say, I guess
that the TRB has is that they don't believe nearly so strongly in your
results for EDA 2 that they do in EDA 1. It's as simple as that.
MR. HARRINGTON: I think that's fair.
DR. HORNBERGER: Yes.
DR. FAIRHURST: Because your got identical peak annual dose
of 85 millirem for the two, and that's the --
DR. HORNBERGER: Yes.
DR. FAIRHURST: That's the bottom line, isn't it?
DR. HORNBERGER: Yes, and the margin is higher for EDA 2 and
the cost is lower, and everything is better.
MR. HARRINGTON: Worker safety is an issue.
DR. FAIRHURST: Emplacement area.
MR. HARRINGTON: As you do an appreciably extended
excavation and then handle half again as many packages, you're certainly
exposing workers to more risk.
DR. HORNBERGER: That's right, and that's real risk.
MR. HARRINGTON: Yes.
DR. HORNBERGER: We know that. Yes.
MR. HARRINGTON: Yes.
DR. FAIRHURST: This is all postclosure, right?
MR. HARRINGTON: Right.
DR. FAIRHURST: And you have not done an analysis -- a
comparative analysis of preclosure risk for EDA 1 versus EDA 2.
MR. HARRINGTON: That's really the construction operations,
and maintenance.
DR. HORNBERGER: Yes.
MR. HARRINGTON: That's all preclosure.
DR. FAIRHURST: Excuse me. Excuse me. Yes, you're right.
You're right. And there you've got --
MR. HARRINGTON: Um-hum.
DR. FAIRHURST: You've not got into any relative risk for
the two of worker exposure and things of that kind in the construction
operations and --
MR. HARRINGTON: Oh, in the EDA evaluations, when we
evaluated the subcriteria and did that assignment of a number, the
1-to-5 ranking, that was to do that.
DR. FAIRHURST: Yes. So what did EDA 1 and -- don't go back
to the slides.
MR. HARRINGTON: I'd have to go in here and find it out.
DR. FAIRHURST: Was that in there?
MR. HARRINGTON: It's not in my presentation. It is in the
report.
DR. FAIRHURST: Yes. But --
MR. HARRINGTON: EDA 1 gets a lower ranking because of the
additional packages that you have to handle and the additional tunneling
that you have to do.
DR. FAIRHURST: Okay. It's interesting, these are treated
separately, and yet, as we say, one is real risk, and the other is
hypothetical.
DR. HORNBERGER: Right.
DR. GARRICK: So the key evaluative process here is the LADS
core team.
MR. HARRINGTON: The key process is the core team?
DR. GARRICK: The key intelligence behind the evaluation is
the LADS core team.
MR. HARRINGTON: Yes. The core team -- there were about
eight or ten people on that. It was all M&O. They were the ones who
did the assessment of the input that they got from the lead discipline
engineers, the spokespersons for each of the reports and analyses that
were done. But it was the core team that did the actual ranking, and
Dick Snell is the manager of that group and will get to speak to you in
a moment.
Now again this is just the M&O recommendation. It came to
the DOE, the Rev. 0 of the report came, and the DOE had quite a few
comments on it. So that intellectual content has been factored into it
also. It's not simply the core team's report. This really represents
the integrated M&O position with DOE comments.
DR. GARRICK: But when you're challenged as to the
transparency of the process, it's -- I guess it's the inability to
adequately document the thought process that these people went through
and the arguments that were put forth?
MR. HARRINGTON: Well, I'm not sure if it's that as much as
maybe a technical disagreement over the legitimacy of the basis of some
of the numbers, the modeling approaches. And I think they see what we
did. I think there's just a disagreement.
DR. GARRICK: Yes.
MR. HARRINGTON: As to what the right approach might be.
DR. FAIRHURST: I go back to something earlier. You
mentioned ventilation was going to be an issue in the meeting. Did you
ever run the case of 10 cubic meters per second throughput for the
amount of heat removed? I was given a curve showing the amount of heat
removed using the EDA 2 design for two cubic meters and five cubic
meters per second. You said you run them from 2 to 10.
MR. HARRINGTON: I thought we had run it at 10.
DR. FAIRHURST: You may very well, and I'm just asking,
because I just got -- but there was 42 percent of the heat removed in
100 years, 60 percent when it went up to 5 cubic meters, and I was
wondering what it was for 10 cubic meters.
MR. HARRINGTON: I don't recall.
DR. FAIRHURST: Okay. Because the cost -- I mean, the power
required to double that is quite dramatic, right?
MR. HARRINGTON: Yes.
DR. FAIRHURST: And the amount of extra excavation. So I
was just wondering whether it was enough of an argument to say that you
might get from 60 percent to 70 percent, but might get better results by
doing other things.
MR. HARRINGTON: Yes. As you know, Dan McKenzie is our
subsurface design lead, and I'm quite certain he has shown me various
curves --
DR. FAIRHURST: Okay. Yes. I would suspect you had.
MR. HARRINGTON: I just don't remember what's on them.
DR. FAIRHURST: It's easy to run on a computer.
MR. HARRINGTON: Yes.
DR. FAIRHURST: It's not as easy to do.
MR. HARRINGTON: Okay.
Other questions?
DR. HORNBERGER: Just more of a comment than a question.
In looking at your tables, in the first table it strikes me
that the differences between your EDA II and your EDA III-A designs are
not tremendously substantial except probably for temperature.
And then the second table, when you look at it, one of the
key things in terms of the performance, under EDA III-A you have some
waste packages in the aggressive corrosion range for thousands of years,
and the performance turns out to be -- whether it substantial or not,
just looking at it, it looks like EDA II performs a lot better than EDA
III-A. And this would indicate that uncertainty in water getting back
to the waste packages while they are hot makes -- can potentially make a
big difference in what you calculate.
And I know the NRC staff has continued to tell me that they
have concerns about penetration of the boiling isotherm and things
getting back into drifts when things are still hot. I know that there
is still some disagreement, I guess, that some of the DOE people don't
think that the boiling isotherm will be penetrated, but there are
arguments about the solidity of that conclusion, I guess.
MR. HARRINGTON: Okay. That was really what caused EDA III
to be -- to perform less well than II, is we talked about that zone of
susceptibility, the EDA III package spent a lot more time in there than
EDA II did.
DR. HORNBERGER: Exactly.
MR. HARRINGTON: Other questions?
DR. FAIRHURST: Yeah, but you are talking about the
potential for dripping through -- above.
MR. HARRINGTON: Okay. I mentioned kind of early on that
the DOE had concluded a little while ago, and the M&O I think is still
working on the assessment of where the significant program uncertainties
are. The flux end of the drift is one of them.
DR. HORNBERGER: Right there, yes. I think it is just one
of the arguments that people make for keeping everything below boiling.
MR. HARRINGTON: Other questions?
DR. FAIRHURST: Well, if not -- but we are going to hear
from Dick now, right?
MR. HARRINGTON: Yes.
DR. GARRICK: Is he going to say where we go from here?
MR. HARRINGTON: He is going to give you more detail on what
EDA II is and what we do to go from here to try and narrow that down.
DR. FAIRHURST: But EDA II in the future, right?
MR. HARRINGTON: Yes.
DR. FAIRHURST: Enhanced.
DR. HORNBERGER: The future of EDA II.
MR. HARRINGTON: Part of that will be given to the
contractor by the DOE and the DOE hasn't made its mind up yet. So Dick
won't have a complete answer. We will, hopefully, have that in a couple
of weeks.
DR. FAIRHURST: All right. It is on the fast path. Thanks,
Paul.
MR. HARRINGTON: You're welcome.
MR. SNELL: Does this sound okay?
DR. HORNBERGER: Yes, you're fine.
MR. SNELL: Good afternoon. As Paul said, I will give you
some more detail on EDA II. You were asking earlier about the report.
You know, this is the report. It is half an inch thick or so. You
probably don't need any more paper than you already have, but there are
-- for each alternative and each design feature that Paul discussed,
there is a separate technical report on each of those items. They
total, I think 31 documents. So if someone should want them, they are
available. They are finished and you can access them as you see fit, or
your staff can.
Let's see how these show. Again, EDA II. Some of this
material overlaps from things that you have already covered in going
through the discussion with Paul, but I will touch on them lightly. For
EDA II we had some temperature goals. As Paul mentioned, we did not
want to exceed 350 degrees C. We did not want to deliberately do
something that we thought would impair the condition of the cladding as
it was received.
We wanted to maintain a drift wall temperature in the rock
of less than 200 degrees C. That was believed to be a relatively
comfortable temperature for the mechanical thermal stability of the
rock.
As matter of fact, with EDA II the rock wall temperatures
are somewhat below that, they are probably closer to 160 or maybe even
less. And we wanted to maintain the temperature in the pillars between
the drifts at less than boiling. We did not want to have boiling fronts
coalescing in the pillar space.
I will talk a little bit about the underground facility, the
waste package and some of the other engineered components in the system.
The basis, again, for the work that we have done was a 50 year closure,
and keeping the rock below the boiling temperature in the pillar space,
we agree, certainly helps to reduce uncertainty associated with the flow
paths that one could expect and with implications for the water
chemistry.
And there are some additional thermal management techniques.
For example, a later closure that 50 years or the use of higher
ventilation rates and so forth, which, in the case of EDA II, could give
you a design where you have no rock above the boiling temperature, but
it is subject to some of those limitations.
We are using line loading, that is the packages abutted very
close to one another end to end. We are using blending, as Paul
mentioned. That line loading and the blending helps to keep fairly
constant axial temperatures and not -- does not give a lot of axial
temperature variation along the drifts.
The aggressive preclosure ventilation, we have talked about
10 cubic meters per second is currently a number that we will probably
proceed with. And we did widen the drift spacing to 81 meters in order
to promote that idea of keeping pillar temperatures below boiling.
The waste package, we are talking about a 2 centimeter thick
Alloy 22 corrosion resistant material, 5 centimeters of stainless on the
inside for structural capability. One of the concerns that was raised
with the carbon steel package, and it applies to a stainless steel
structure material as well, since it is iron-based, is oxide wedging.
In this case, with the corrosion resistant material on the outside, the
wedging is not so much a concern until you have actually breached the
outer shell, and even then, with the stainless steel on the inside, as
opposed to carbon steel, it does tend to minimize any wedging that you
might get once the breach has occurred.
The life of the corrosion-resistant material is quite long,
as you can see, compared with carbon steel that was used in the
viability assessment design, and the thermal management techniques that
we have been using the ventilation, blending, reduced areal mass
loading, all help to keep the outer surface of the waste package outside
windows of susceptibility for corrosion.
There is a set of curves here and the chart that follows is
probably a little bit easier to read than this one, but this gives you
an idea of a comparison of waste package, relative humidity
considerations, and waste package temperature considerations. There is
a box that is shown up here which defines what is regarded as the most
aggressive of the corrosion regimes that we are dealing with. Waste
package temperature at about 80 and on up, and humidity is from roughly
80 percent up to 100 percent.
The assumptions that were used to prepare these curves, we
used a long-term average climate. The dual continuum refers to this
line here, this bullet refers to the modeling in the rock. Dual
continuum is a model that they use that has both fracture flow and
matrix flow in the rock, and that is the reference to dual continuum.
They used a number of different waste package heat release
rates. Fifty years, and here they used a 50 percent heat removal, that
is through the ventilation mode. And simultaneous emplacement at the
middle of a 23 year emplacement period. The average waste that has been
used for a lot of the thermal calculations is a 26 year old average --
average age on fuel that has been received.
DR. FAIRHURST: So would that -- you say it avoids the
aggressive crevice corrosion region.
MR. SNELL: Yes.
DR. FAIRHURST: As I understood it, below 80 degrees and 80
percent humidity, there are virtually no mechanisms of corrosion, right,
for C-22 -- for the alloy, A-22.
MR. SNELL: I think I would agree with you, but others might
not. What we have shown here, this region that is shown here is what we
believe is a reasonable definition of aggressive range.
There are some thoughts that even lower relative humidities
or even lower temperature regimes, worst case scenarios, if you will,
could give you some sort of corrosion environment. So we --
DR. FAIRHURST: Because we were down at the center, Center
for Nuclear Waste Regulatory Analysis, and they were saying the same
thing, that they thought 80 degrees C was virtually a foolproof
temperature below which nothing would happen.
MR. SNELL: Right.
DR. FAIRHURST: And I think Shoesmith, when he was here, and
Payer are also saying the same thing. So who is saying that there are
opportunities?
MR. SNELL: I am not sure I can ascribe it to any particular
individual. I guess I am referring to comments that have been made
during the course of the work that we have done.
DR. FAIRHURST: I see.
MR. SNELL: I can't give you a specific quote.
DR. FAIRHURST: I didn't know there was any mechanism, I
don't know.
DR. CAMPBELL: There is still corrosion that is taking
place, but it is general corrosion, as opposed to localized.
DR. FAIRHURST: Yes. But apparently that was --
MR. SNELL: He said it.
DR. FAIRHURST: Okay. You said it, it is general corrosion,
and that is such a low rate that it is really a no -- okay. That is
what you mean.
MR. SNELL: I am sorry, I missed your point. Yes, the
aggressive regime would be crevice type corrosion, the general would
occur.
DR. FAIRHURST: So it would be aggressive or crevice
corrosion?
MR. SNELL: Right.
DR. FAIRHURST: It is not an aggressive type of crevice
corrosion.
MR. SNELL: Right.
DR. FAIRHURST: Okay.
DR. HORNBERGER: What are the lines on here that start out
around 170 degrees?
MR. SNELL: I honestly don't know. I just asked a couple of
the people who were working on the group with us. There are some
horsetails there and I can't explain them right now. I will get you a
clarification.
DR. HORNBERGER: Okay.
MR. SNELL: Paul may have an answer. He is going to --
MR. HARRINGTON: Paul Harrington, DOE. We asked that
question earlier. I think it is a TRB thing, and that is the time of
emplacement of backfill, if I remember correctly.
DR. HORNBERGER: Is that what is was?
MR. HARRINGTON: Yes.
DR. HORNBERGER: Okay. So that represents then a sudden
jump?
MR. SNELL: The backfill --
DR. HORNBERGER: It doesn't make sense.
MR. SNELL: -- will alter the temperature environment when
you put the backfill in.
DR. HORNBERGER: Yeah, I know.
MR. SNELL: Temperature and humidity, for that matter.
Yeah, but there is no -- okay. At any rate, all right.
DR. FAIRHURST: What is it?
DR. HORNBERGER: They put backfill in then.
MR. SNELL: Yeah, the backfill gets installed after 50
years.
DR. FAIRHURST: And so nothing goes above 30 percent or low
end.
MR. SNELL: Right. This is a somewhat different portrayal
of some similar information, but this is the Alloy 22 window of
susceptibility again, that box, but this is time scaled, and, again,
plotted against waste package temperature. There are a couple of
different curves. This is the -- perhaps one of the less conservative
waste package temperature models.
This one a little more conservative. And this indicates
that through 10,000 years, really, you are staying outside that box.
This is the box that portrays, again, a return to a humidity of 80
percent about 2,000 years; the first drip shield failure out of this
time frame at about 9,000 years. This is EDA II with backfill. And
this says no aging, but, again, the presumption is 20 fields going into
-- going into the repository. It's no aging beyond the waste, as
received.
Again, the drip shield is a two centimeter thick titanium
seven grade overlap. This was covered briefly before by Paul. It's
seepage protection. It's general corrosion mode and, again, the first
drip shield failure at about 9,000 years. Medium failure with the
information we have now for that grade titanium is about a 50,000
failure time. It does provide, in and of itself, some rock fall
protection for the waste package. We tried using a material different
that -- that was used on the waste package, so that we did not get into
common mode considerations on a material failure. And it helps to limit
the transport modes to a diffusive transport, as opposed to any
advective or liquid flows.
Talk about backfill, of the drip shields, as Paul mentioned,
one of the attractive things about it, and it does have its drawbacks,
in terms of the complications associated with the emplacement and so on,
but it does give you a geometry that's more predictable. If you do not
have backfill and you have a drip shield and you began to experience
some localized collapse on the part of the emplacement drifts, it's very
difficult to predict what form that's going to take. Backfill gives you
a controlled geometry, if you will, at least to the surface of backfill.
Above that, of course, you're at the mercy of the natural degradation of
the drifts. And it helps considerably with regard to rock fall, which
is a major consideration, in terms of long-term stability; helps with
maintaining low relative humidity.
Material is under evaluation right now. We're looking at
everything from a quartz sand, a very fine material, to a crushed tuff,
on the other end, quite a wide range of materials. The thermo
conductivity and other characteristics of the material are part of those
considerations. We don't have an answer yet. We'll be picking material
for backfill near term.
MR. HORNBERGER: Does buffering have a chemical commutation.
MR. SNELL: Here?
MR. HORNBERGER: Yeah.
MR. SNELL: Yes.
MR. HORNBERGER: That was the intent. Also, if you do have
backfill over a drip shield, which has a crack or a minor breach, the
backfill does tend to minimize any water flow through that -- through
that crack. It does tend to wick water back away from the crack.
As Paul mentioned, we earlier had looked at a concrete
ground support structure, a lining, and one of the concerns was that if
the concrete -- presence of the concrete elevated the Ph of the water
that did get back into the drifts and move down through the drifts, that
that higher Ph might tend to promote higher solubilities on some of the
radio nuclides it would get out. And it was enough of a concern and
appeared to be difficult to resolve in a timely fashion, that we decided
that we'd better go to a -- either a steel and expanded metal mesh or
rock bolts and metal mesh, perhaps. There will still be a minor amount
of cementitious material, because we'll probably grout the rock bolts.
But, the quantities associated with that are very, very small, compared
to the quantities that we would have had with a thick concrete lining,
and we believe that those quantities are small enough that we do not
suffer a major problem with that.
It does -- we're using ballast down int he invert area and
it does allow us to do some tailoring on controlling drainage and
providing some material properties that are most beneficial for the
design.
DR. WYMER: What is the ballast?
MR. SNELL: Ballast material, it's going to be a graded
material in the bottom of the --
DR. WYMER: But what is it?
MR. SNELL: Oh, what material? Again, we're not sure. It's
going to be considered along with the backfill choice; if anything, from
a quartz sand or a crushed tuff, and more likely, I would say right now,
probably a -- the crushed tuff or something like that.
Kind of a busy picture, but it gives you some visualization
of what we've got with EDA II. A cross section of the emplacement
drift, something like this, was shown the waste package with about a 1.6
meter diameter; the larger one, the two meter diameter, which is the
largest the waste packages would be here. The drip shield, just large
enough to clear the largest of the waste packages. Free standing, that
is it's not leaning on or supported, in any way, by the waste package,
but it's free standing on the invert and then backfill material over the
top of that.
This is not precisely the scale, but approximately, so you
get some idea in terms of the thermo portabations. The expectation with
EDA II is that the boiling region, something like this around the
emplacement drift, the space from here to the adjacent drift and fairly
large. We're probably talking about a non-boiling zone in here of -- on
the order of 80 percent of the pillar width, something like that. I
think the other points have been covered.
A little bit of a closer look at the cross section for the
drift, I mentioned it briefly a moment ago, but down here, the invert
area and support rails here for the carrier that would bring waste
packages in. And I think as Paul mentioned briefly, this portrays a 5.5
meter diameter emplacement drift; two meter, the largest of the waste
package size. We did spend some time looking at emplacement equipment
getting in. It's very difficult to get a drift diameter much smaller
than that and still be able to get those packages in there fairly
readily. When you look at the section that shows the equipment, and
what they're considering right now is something like a variation on a
straddle carrier, if you will, where you can roll it in on rails and
you're carrying a package underneath. It's a fairly tight fit with the
-- with the inside of the rock face on the emplacement drift.
DR. FAIRHURST: Is that large time on the drift based on
getting material in or getting material out -- you know, retrievability?
Retrievability, you just pull it out and put it in an empty drift,
right?
MR. SNELL: Both, I suppose, really.
MR. HARRINGTON: Charles was looking at me when he asked it,
so I guess -- how does Paul Harrington deal with --
DR. FAIRHURST: No, he answered it.
MR. HARRINGTON: Okay. It really was more excavation and
emplacement technology, than simply retrieval, since retrieval would use
the same equipment as emplacement, as it was used to emplace it. It's
really the same question.
DR. FAIRHURST: In retrieving, you're going to pull out into
the drift and park another empty drift, right?
MR. HARRINGTON: Well, real retrieval would be --
DR. FAIRHURST: Over the other is what I'm saying.
MR. HARRINGTON: Oh, no, no.
MR. SNELL: That's correct.
MR. HARRINGTON: At one point, we talked about the ability
to move a package over an adjacent package and five-and-a-half meters
was conducive to that. That was not the only thing, though, that was
driving the five-and-a-half meters. Even if we don't continue to
maintain that capability and going to this different type of carrier,
probably, we won't be able to do that. We're still looking at a
five-and-a-half meter drift. So, the ability to pull a package over
another isn't really what drove us at five-and-a-half.
MR. HORNBERGER: Dick?
MR. SNELL: Yes.
MR. HORNBERGER: The shield -- the drip shield --
MR. SNELL: Yes.
MR. HORNBERGER: -- you know, this long mailbox --
MR. SNELL: right.
MR. HORNBERGER: It's going to go in in sections that are
about as long as the canister and then -- a little longer, because then
they overlap?
MR. SNELL: Probably, as we understand it right now. The
idea would be the mailbox sections would overlap one another and you'd
do kind of a -- you'd back out along the drift, as you install the
second --
MR. HORNBERGER: As you install, right?
MR. SNELL: Yeah. It's somewhat instructive to compare EDA
II with the VA design. Some of the comparisons have already been drawn.
But, it is significantly lower mass loading. And, again, it's really
temperature. Mass loading is a number that falls out. It's the
temperatures that are -- the critical items for the design. But, with
60 MT per acre, it lets you control temperatures better. The drift
spacing, as you can see, quite a bit larger, in the case of EDA II, in
order to sustain that non-boiling region between the drifts.
Somewhat different invert design, again, to get away from
concrete. And the same thing with ground support, going to do the steel
sets or rock bolts and mesh, as opposed to a lining. Approximately the
same number of packages total in the repository. Line loading for a
more uniformed temperature distribution. Sizable reduction in the
length of emplacement drifts, because of the fact that you're using line
load. You've got the packages close together and you get more
utilization of the drifts for the same quantity of packages.
Quite a change, as has been noted, in the waste packet
materials, with the alloy 22 and alloy 22 on the outside of the waste
package. Still uses 21 PRW assemblies. The peak ways package
temperature is substantially below what it was for VA. Here, it was
about kilowatts and we're down to about 11 roughly kilowatts maximum
heat output here. We do have the drip shield and there was none here.
And the backfill, there was none here, although drip shield and backfill
were options identified in the VA design. Same closure period, 50
years. And quite a difference, obviously, in ventilation. Here, the
ventilation was really an incidental item; but, it's really important to
us, in terms of temperature control in the EDA II design.
Comparison of the two cross sections, the design on the
left. And, again, essentially, same diameter, concrete lining here
versus steel here. Essentially, the same package geometry and a very
similar appearance in the bottom, except that here, we're going to a
granular material in the invert, rather than concrete in the VA design.
MR. HORNBERGER: All your schematics show roughly half of
the drift filled with backfill. How do you decided how much to put in?
MR. SNELL: We have really not decided yet, is the truth.
It's TBD.
DR. CAMPBELL: What's the -- in the cross section here and
in the two pages previously, the dotted line? The previous view graph
said large waste package.
DR. FAIRHURST: A previous package.
DR. CAMPBELL: What is that for?
MR. SNELL: Some of the -- some of the packages -- or some
of the fuels, rather, and materials we get require somewhat larger
package. The most common one, the large majority, will be the smaller
1. --
DR. CAMPBELL: Is that for a defense, high level waste class
or what?
MR. SNELL: I think it may well -- Paul is nodding his head,
yes, DHLW.
MR. HARRINGTON: Codisposal.
MR. SNELL: For the -- yeah, for the codisposal package,
where you've got a -- I think it's a five array on the outside and one
central canister inside. The sum total of that gives you --
DR. CAMPBELL: That's the five glass containing --
containers and then a central -- central DOE canister.
MR. SNELL: Yes. Five canisters are on the outside, one
canister in the center --
DR. CAMPBELL: Okay.
MR. SNELL: -- for disposal.
DR. GARRICK: You may have answered this, but why have you
made the tolerances so close between the large container and the drip
shield? I mean, is there a reason --
MR. SNELL: No -- no intent, at this point. We have shown
them close; but, frankly, I don't know whether that close a clearance is
desirable or not. I'm inclined to think that it's too close.
DR. GARRICK: Yeah, just from an engineering standpoint, why
would you want to make that a precision situation?
MR. SNELL: I agree.
DR. GARRICK: Yeah.
MR. SNELL: I agree. It was graphics license, I guess, in
this case.
DR. GARRICK: Right, right; okay. One of the things I
wanted to ask, and I don't know where -- when's the appropriate time to
ask it, but in the previous presentation, you had all of the designs
compared and you had the performance information. And the implication
is that they're all with the same degree of prevision. And I doubt that
that's true, given that the VA was analyzed up the kazoo for months and
month in advance and, yet, to the outsider, you would look at this and
say, my God, you've done what you did for the VA in just a couple of
months for five designs. So does that raise some question about the
quality of the analysis that was behind the performance calculations
and, therefore, raise some question about the selection process?
The reason I was asking it, I was going to ask a specific
question of what was the impact on performance of replacing all the
concrete of the VA design with the steel of the EDA II design. Are you
able to see those kind of specific -- specific -- maybe you asked this
question while --
MR. SNELL: No, no.
DR. GARRICK: -- I was out.
MR. SNELL: Well, I'll take your first question first. It's
a reasonable question to ask.
DR. GARRICK: All right.
MR. SNELL: And I think the answer is that first of all, we
benefited greatly by the work that was done for the VA design. When we
started this effort, we worked with the performance assessment people
all the way through. And one of the first things they did was look at
the PA models that were done for viability assessment and we said, to
what extent does that same model correctly reflect or portray these
various enhanced design alternatives that we're looking at. We came up
three sets of situations.
One was the design is pretty close to VA, the PA models are
sufficient, more or less as they stand. The second set was the model is
broadly reflected with the design, but there's some specific aspects
that are different and, in that case, PA went in and made some
adjustments to the PA model. Typically, those adjustments were in the
form of assumptions that were input to the PA model, to more correctly
reflect those design. The third case that we had, and this fortunately
was the less frequent case, was that the PA model, in its then current
form, did not really tell the tale properly and they actually had to go
in and make some modifications and some of the process models that
supported the PA runs. So, they started that work early and they did,
indeed have to make some changes on the PA runs -- or the PA models that
they used for runs on a few of the EDAs.
Certainly, work was done more quickly than it was done for
the VA. But the fact that we had the VA model and they were able to go
in and either change input assumptions or modify the model somewhat,
allowed us, we think, to do a pretty fair appraisals on these designs.
DR. GARRICK: I see.
MR. SNELL: The second question, I think the answer is, no,
we probably do not have enough fidelity in the models to see
differences, as a result of some of these changes that you've mentioned.
DR. GARRICK: Right, okay. Thank you.
MR. SNELL: Some advantages of EDA II over the VA reference
design, we think, in the drifts, we've talked about these a bit already.
It gives us a somewhat higher confidence in the modeling and somewhat
higher confidence in addressing uncertainties. The line loading is
helpful in getting a uniform temperature distribution. Repository rock,
obviously, with the lower thermal load and temperatures -- lower
heating, in terms of temperature, and also shorter time periods with the
package designs and emplacement that we're using. And, again, the drip
shield benefits, which are really significant in getting you beyond a
time period, when you're in some of the most aggressive conditions. A
drip shield is very helpful, if that initial failure not occurring --
predicted, anyway, until some 9,000 years into the period of
performance.
Backfill, again, in a summary. It kind of helps protect the
drip shield, itself, from rock fall and also from iron contact. There's
been some concerns expressed about hydrogen and brittlement and
interaction between iron and the titanium in the drip shield. Switching
the corrosion resistant material, the outside of the waste package is a
major benefit.
DR. WYMER: Doesn't the drip shield rest on a piece of iron,
though?
MR. SNELL: I don't know if we've even got that detailed
yet. Frankly, it's free standing, but we could put it on some material,
other than iron. And I don't think we're there yet, frankly.
The oxide wedging, and, again, we -- with CRM on the outside
of the package, we've got a better situation than we had with VA. And,
again, steel ground support, rather than concrete, we think is a move in
the right direction, in terms of grade, nuclide, mobilization and
transport.
MR. HORNBERGER: I don't think I understood your answer to
Ray's question. You have a steel ground support. You have a canister.
But, you're not sure whether the canister is going to sit on the steel
support?
MR. SNELL: Your question was the drip shield, right?
MR. HORNBERGER: Oh, that's the drip shield?
MR. SNELL: Yeah.
MR. HORNBERGER: The drip shield won't touch the steel
floor?
MR. SNELL: The drip shield might or might not rest on a
piece of steel in the invert design. And the question is a good one.
And I think given any concerns we might have with regard to the effect
on titanium with having iron contact --
MR. HORNBERGER: Right.
MR. SNELL: -- we might choose to put a -- you know, some
kind of a liner, separator, use a different support form. We don't know
yet.
DR. CAMPBELL: Let me clear something up that now I'm
unclear about. The invert consists of what? Before, it was some sort
of a cementitious material. It was provided a flat surface to roll
things in. What is invert now?
MR. SNELL: Well, to use the term "invert" --
DR. CAMPBELL: It is just a --
MR. SNELL: -- is probably an oversimplification. But,
there's a structure at the bottom of the emplacement drift, which
includes the rails and the supports for the rails that allow a
transporter to get in and out. It includes the space between the rails
and below the rails, where we've got material installed -- ballast
material, if you will, if you want to liken it to a railroad. And those
are probably the main elements.
DR. CAMPBELL: So the main structure of that is -- is it
steel or is it carbon --
MR. SNELL: Right now, it's a steel structure.
DR. CAMPBELL: And then you'll fee it with some sort of
filler material, crushed tuff, or something like that, as a ballast
material; okay.
MR. SNELL: Still talking about a comparison with the
viability assessment design, it's a little bit better from a defense and
depth standpoint with the additional barriers. It's probably a little
bit easier operationally. We have a little more latitude with placement
of the waste packages than we might have had with VA, because the
hottest VA package was up at 18 kilowatts. We -- since we're using
blending and line loading, on the other hand, there are some -- there
are some operational complexity associated with the blending operation,
itself. That's not -- that's not a slam dunk. I mean, that's -- it's
going to require some fairly complex surface facilities.
The design does give us pretty good flexibility, in terms of
moving it one way or the other. If the element choice on a design is to
make it hotter or make it cooler, this design tends to be one where you
can kind of its performance, relatively easily compared to some of the
other designs.
DR. WYMER: Doesn't blending imply that you've got quite a
large above surface storage area, so that you can store fuels of a lot
of different decay times, and pick and choose?
MR. SNELL: It could. Our problems is right now, we don't
have a really firm handle on the waste receipt screen that we're going
to get. Obviously, there's a wide array of fuels out there in the
inventory; some hot stuff, five year old, that we could get. There's a
lot of older fuel. And right now, we're trying to anticipate what the
storage -- surface storage receiving storage might be at the repository.
We need some storage anyway, just to deal with operational upsets, with
interruptions or irregularities and deliveries. And adding blending is
another item in the mix, in terms of what we need on the surface. So,
it's probably not a good answer to your question right now, but
certainly there's an implication for more surface storage to handle
blending, yes.
DR. WYMER: Yes.
MR. SNELL: Paul mentioned the cost and the fact that the
net present values are -- for EDAs II through V are fairly close;
somewhat higher for EDA I.
Some recommendations with regard to design refinements,
these are contained in the last report. But to go through them briefly,
things that we have to look at, as we go ahead, the design basis heat
output for the waste packages. We've picked some heat outputs right now
for the purpose of this work. We've got an 11.8, I think it is, KW heat
output. That's a max and nine point something average. We need to pin
that down a little more closely, so we can do some more detailed
analyses.
Modular is probably a bit of a misnomer, but phased
construction on the surface anyway is a consideration. And we need to
be able to consider, if we need to phase construction on the surface,
how does that fit with EDA II, as it's presently configured.
Ventilation, segregation of waste types in the drifts and so
on, there still are some thing that we can do there, we think, to
improve or enhance this design. We don't necessarily have enough
information quite yet to be able to do. But, there are some refinements
in thermo management that we should be looking at, as we go ahead.
Right now, we're based on a 50-year pre-closure period, not
only to not preclude a longer period, but there is potentially some
advantage to a longer pre-closure period, should that become a
possibility for the program. We probably have some opportunities for
standardizing waste package designs. I think that might represent some
cost enhancement, maybe some improvement and so forth, that we might be
able to take advantage of.
We need some more focus, development work on the waste
package designs with this alloy 22 on the outside. There's a reasonable
amount of work that's been done so far, but there's more to be done.
We've got to what amounts to a slip fit of the stainless inside the
alloy 22. There's some items at work that have to be done with
regarding fit up welding, closure welds, and so forth. We need to put
some attention on that.
In cases where we do not have zirconium based cladding
coming in, there's some cannisterization techniques that we might be
able to use, similarly to what we're doing with the defense high level
and the DOE waste. You were asking about the invert a moment ago, and
we - obviously, we have some work to do there, with regard to what's the
geometry and what kind of materials are we going to use, how we're going
to put them in, and so forth.
The drip shield design right now is conceptual only. We
picked two centimeters. We picked titanium seven for diversity in
materials. But, we don't have a great deal more than that. I mean, we
need to do some refinements on that. Right now, it's presumed to be --
essentially a smooth shell overlapped from one section to another, but
considerations -- should it be ribbed before additional structural
stability, you know, things that might promote drainage, once we get any
water on the surface and what no. We have to look at those things.
And then our backfill design, again, the selection of
backfill materials, like the invert materials, considerations of thermal
behavior and so forth are important. And backfill, I am the drip
shields, imposed some complications on the installation. We're talking
about drifts that are full of hot waste packages going in with large
remote equipment and placing these things in a controlled manner;
getting a geometry that we expect, when we -- when we finish the
emplacement operations. Those are going to require some attention.
That's pretty much where we are right now.
DR. FAIRHURST: Brett, do you have some questions?
MR. LESSE: I'll wait until you're done.
DR. FAIRHURST: John, do you have questions?
DR. GARRICK: Well, I'm just trying to visualize what the
impact of these different -- these changes might be on the general
operation during the pre-closure phase. And, of course, one of the
things that comes to mind is this -- is what Ray has already raised, is
this blending question, and I just want to understand that. Are you
really talking about blending at the individual fuel assembly level?
MR. SNELL: Yes. Not to say that you have to blend with
every set of fuels that you get in, but it's the thermal output of the
waste package that's critical to us, in terms of controlling
temperature. So, I'm going to have to do some mix and match and some
blending, so that we don't exceed, at least the maximum desire to heat
output per package.
DR. GARRICK: But, it seems to me with a little planning,
one might be able to -- at the originating site, do that in such a way
that you don't have to do it at the repository.
MR. SNELL: I agree. I think there may be some real
opportunities for us. Paul, I think, is going to volunteer a comment,
at this point.
DR. GARRICK: Right.
MR. HARRINGTON: Paul Harrington. We certainly agree with
that. Our receipt folks in headquarters remind us, though, that we have
little control over incoming waste stream. So, what we've asked the MNO
to do is design a solution that is as much as possible waste stream
independent. If we are able to have more control over that incoming
waste stream, then we can simplify some of these operations.
DR. GARRICK: Well, I don't know, I don't know how much time
you've spent around a nuclear power plant, but handling fuel samplings
is not something you do in a hurry. And, of course, you've got lots of
time.
[Laughter.]
DR. FAIRHURST: George, do you have a question?
MR. HORNBERGER: Yeah. I'm still somewhat interested in the
procedure, I guess, that Paul described, in coming down to EDA II and
your consideration, I guess, in the phase one. It strikes me, again,
just looking at some of the performance comparisons that you did for the
alternatives that you considered. Water contacting the waste packages
is really important.
MR. SNELL: Absolutely.
MR. HORNBERGER: And if you turn those canisters on its end,
i.e., if you put them into a vertical bore hole, it seems to me you get
at least an order of magnitude improvements in performance just by doing
that. Now, I believe that you looked at this and you must have some
reason why you discarded those options. But, is it a simple reason or
is it a -- I mean, I know you've put in drip shields to keep water off
and everything else. But, there are some other things that seem very
straightforward that you could do, that -- I mean, if you turn the
canister on its end, nobody can argue that, well, maybe the drip shield
will corrode. I mean, you really have cut down the cross section area.
DR. WYMER: Yes.
MR. SNELL: I'll have to go back -- or we'll have to go back
and look at the report, where we looked at the alternative waste
emplacement models to give you the particulars. I'm not sure that there
is any one simple answer, as to why we did not carry that one forward.
I guess, Paul, were you going to make a comment?
MR. HARRINGTON: I'll volunteer a couple of things I do
remember from that. One, it introduced a great deal of complexity to
the criticality calculations. When that finally does start to go to
degrade mode and you end up with it all piled down at the bottom of the
canister, unless we limited the individual packets to no more than, I
think it was two or three assemblies, then there's a potential for
criticality. In addition, because of having to go to smaller packages,
you end up with an awful lot of them. And there were mechanical
handling complexities, also, with moving in and rotating and translating
and stuff like that. But, it would have been a little tougher. There
are a lot of things, but criticality was one of the big ones.
DR. FAIRHURST: Was that not an issue for the Swedish
design?
MR. HORNBERGER: Right.
MR. HARRINGTON: I don't know enough about that to comment.
DR. FAIRHURST: But, that is a KBS III design, isn't it?
MR. HARRINGTON: Smaller packages than ours, right?
DR. FAIRHURST: Yes.
MR. HARRINGTON: Okay. I'm sure they're having to deal with
that, also.
DR. FAIRHURST: I was just wondering why in this design, if
you've made comparisons of that kind, what other people had come up.
Anyway --
MR. HARRINGTON: I can't speak to theirs, yet.
DR. FAIRHURST: Any other questions, George?
MR. HORNBERGER: That's it.
DR. WYMER: No, I asked mine as we went along.
DR. FAIRHURST: All right, Brett, now is your chance.
MR. LESSE: Brett Lesse, NRC staff. I had a question that
you touched on a little bit on page five and 10. You talk about 50
years at 50 percent heat removal. And it's not clear whether that was a
calculation or an assumption. If it was a calculation, where is it
documented, and would it be possible for the NRC staff to get that, as
well?
MR. SNELL: We can give you the calculation information. I
think the 50 percent may have been an assumption, at the time. We've
used 50 since then. We've done some calculations that suggest that
higher percentages are achievable. If you'd like to get a copy of the
--
MR. LESSE: We'd be interested in looking at the ventilation
calculations --
MR. SNELL: Sure.
MR. LESSE: -- and which kind of codes you're using.
MR. SNELL: Okay.
DR. FAIRHURST: It's been done.
MR. LESSE: Okay. And the second question really had to do
with something that you mentioned twice, which is that the choice of
ballister backfill ranges from sand - or quartz sand to tuff. And it's
my understanding it's either quartz sand or tuff, which is different.
Also --
MR. HORNBERGER: What's between those two, Brett?
[Laughter.]
MR. LESSE: Well, it's also been suggested that limestone
was possibly one of the material. So, I'm kind of unclear on whether
it's a range of materials you're looking at or are you looking at two
materials, because that affects us, how we try to assess some of the
processes that could occur in performance assessment.
MR. SNELL: It is not just two materials, as I might have
suggested. We're looking at any materials that might be suitable. I
mentioned quartz sand and crush tuff, because they kind of represent a
range of mechanical sizes and mechanical characteristics, quartz sand
being fine grain and crushed tuff being relatively coarse. But, the use
of a carbonated based material, limestone or something like that, is
also a consideration. It has some potential chemical benefit, as well
as just its mechanical characteristics and thermo characteristics.
MR. LESSE: And then a follow up question, which is probably
to Paul, which is: my understanding for the site recommendation
consideration draft, that the deadline for data is in August. When will
the decision for a design be made relative, so that we can focus our
performance assessment on appropriate materials? For instance, there
are details associated with the design that have performance aspects.
When DOE chooses a design to go ahead with SR, will it be at a gross
level or will it be at a specific level? When might that decision be
made?
MR. HARRINGTON: I wish could remember.
[Laughter.]
MR. HARRINGTON: As you're asking me that, I'm sitting here
thinking, okay, what were those dates. I think it's November of '99,
was the date that the design folks were to feed their basic design
approach into the PA folks, for PA to use as a basis for their work.
Also, let's see, about June of '00, somewhere right in that time frame,
if I remember right, and I just don't have the schedule here, was the
date that the design group was to have the first cuts of the SR writeup
done for transfer to the licensing guys to start assembling the product.
I may be somewhat off on those dates.
MR. SNELL: I think April of '00 is when they were looking
for it.
MR. HARRINGTON: Okay.
MR. LESSE: Thank you.
DR. FAIRHURST: One of the discussions that I was at, there
was a third defense of concrete, saying that the problems with Ph could
be, you know, dealt with by using low Ph concretes. Is any work being
done on that?
MR. SNELL: Some work was done following those discussions.
I think that was about the workshop time or thereabouts.
DR. FAIRHURST: Right, right.
MR. SNELL: Some work was done following that, quite a lot
of research in this other sources of data on concrete behavior and the
ability to use additives and control chemistry. The conclusion we came
to was that even with the use of concrete additives, we still thought
there was a fairly serious risk of moderately higher Ph results by
having concrete in large quantities present in the drifts. And still,
even where Ph control looked to be fairly promising, there's still a
fair amount of uncertainty in being able to achieve the Ph control with
a lot of confidence. And I think it was more -- probably more of the
uncertainty of Ph control than anything else, which caused us to drop
concrete as an approach for the ground support.
DR. FAIRHURST: Because, that tends to rule out shotcrete,
too, doesn't it? And if you rule out shotcrete, that's a technique
that's quite valuable. Are you looking at any alternative to some sort
of projected concrete or projected materials that would bond the
surface?
MR. SNELL: It does tend to rule out shotcrete, you're
right; same problem, cementitious material. Shotcrete would be probably
thinner, lesser quantity -- total quantity, but the same fundamental
concerns. So, again, the issue, I think, would be --
DR. FAIRHURST: That's of great value, initial stabilization
of an excavation.
MR. SNELL: Yeah. I suppose with more work, you could say,
you know, the use of shotcrete in limited applications might still be
available to us, because we're going to have cementitious material
associated with the grouting of rock bolts.
DR. FAIRHURST: Yes.
MR. SNELL: If you -- if you've got into areas, where you
had some questionable ground or you had some localized concerns about
ground support, maybe you can still use shotcrete and not really
jeopardize performance in any major way; possible.
DR. FAIRHURST: I was thinking that maybe some other agents
that you could use for bonding, rather than sand. That's just a
hypothetical question.
MR. SNELL: It might be others. Some of the things that you
might use as an alternative are hydrocarbons, and those are no good,
either.
[Laughter.]
DR. FAIRHURST: I don't know.
DR. GARRICK: How about salt from Carlsbad?
[Laughter.]
DR. FAIRHURST: Well, depending on the probability, I think
we've used sodium silicates, and you can actually bond stuff with that.
But, I'm not sure that's any better than concrete -- well, not just for
Ph.
Any other questions? What this space with interest. Thank
you, very much.
MR. SNELL: Okay, thank you.
DR. FAIRHURST: We take a break now?
DR. GARRICK: Yeah. I want to thank Paul and Richard for an
excellent presentation, for doing it on time. Now, if you'll just carry
that talent forward to the project.
[Laughter.]
MR. SNELL: A suggestion duly noted.
DR. GARRICK: We'll take a 15 minute break. And also after
the break, we will not need the reporter.
[Whereupon, the record portion of meeting recessed, to
reconvene at 8:30 a.m., Wednesday, July 21, 1999.]
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