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Home > Electronic Reading Room > Document Collections > Commission Documents > Commission Meetings, Slides, Transcripts, Meeting SRMs, and Full Written Explanation for Closed Meetings > 1997
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03/25/1997
1
UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
***
BRIEFING ON HIGH-BURNUP FUEL ISSUES
***
PUBLIC MEETING
***
Nuclear Regulatory Commission
Room 1F-16
One White Flint North
11555 Rockville Pike
Rockville, Maryland
Tuesday, March 25, 1997
The Commission met in open session, pursuant to
notice, at 10:04 a.m., the Honorable SHIRLEY A. JACKSON,
Chairman of the Commission, presiding.
COMMISSIONERS PRESENT:
SHIRLEY A. JACKSON, Chairman of the Commission
KENNETH C. ROGERS, Member of the Commission
EDWARD McGAFFIGAN, JR., Member of the Commission
. 2
STAFF AND PRESENTERS SEATED AT THE COMMISSION TABLE:
JOHN C. HOYLE, Secretary
KAREN D. CYR, General Counsel
JOE CALLAN, EDO
DR. CARL PAPERIELLO, Director, NMSS
THOMAS KING, Deputy Director, Division of Systems
Technology, RES
GARY HOLAHAN, Director, Division of Systems Safety and
Analysis, NRR
RALPH MEYER, Senior Technical Advisor, RES
HAROLD ORNSTEIN, Reactor Analysis Branch, AEOD
. 3
P R O C E E D I N G S
[10:02 a.m.]
CHAIRMAN JACKSON: Good morning. I am pleased to
welcome members of the Staff to brief the Commission on
high-burnup fuel issues.
Greater economic competitiveness is causing the
nuclear power industry to pursue various changes. Among
those are longer fuel cycles and high burnup fuels. This
morning the Staff will discuss its activities in the high-
burnup fuel area and describe any safety concerns raised by
information derived from reactivity insertion experimental
test results in other countries including France, Russia,
and Japan.
The Staff will describe how these experiments are
being followed up and what impact they have on issues of
safety in U.S. nuclear reactors.
The Commission is interested in hearing how the
Staff is integrating information from research including the
results of tests and analysis done by the international
community and domestic operating experience and how this
information is being used to ensure that plants are
operating safely and in conformance with their licensing
basis.
The Commission is also interested in hearing about
the appropriateness of our current fuel damage criteria for
. 4
reactivity insertion events.
My understanding is that the Staff will discuss
the status of the research program on high-burnup fuel and
the adequacy of our codes to account for high-burnup
effects.
The research program to date has focused on high-
burnup fuel response to reactivity insertion accidents, but
there are other considerations. For example, high burnup
fuel response under design basis analysis, loss of coolant
accident operational transients and shortcomings in
criticality and reload analysis for cores using high-burnup
fuels.
The Staff should describe progress being made in
these areas as well, so we look forward to your briefing
today and I understand that copies of the viewgraphs are
available to the entrances to the room.
Mr. Callan, please proceed.
MR. CALLAN: Thank you, Chairman. Good morning.
Good morning, Commissioners.
The last communication with the Commission on
issues surrounding high-burnup fuel was a memorandum to the
Commission dated November 25th, 1996.
Today's briefing will pick up from that November
memorandum and summarize NRC work related to high-burnup
including our plans for the resolution.
. 5
At the table with me are representatives from all
four major technical offices, since the high-burnup fuel
issues impact activities in all four offices.
To my left are Tom King and Ralph Meyer from the
Office of Research. Their presentation summarizes the NRC
research program designed to obtain the relevant data to
assess the behavior of high burnup and MOX fuels.
To my right is Gary Holahan, representing the
Office of Nuclear Reactor Regulation. Their presentation
summarizes the U.S. operating experience in NRC regulatory
action.
Also to my right is Hal Ornstein, representing the
Office for Analysis and Evaluation of Operational Data. The
AEOD summarizes international operating experience.
Also to my right is Carl Paperiello, representing
the Office of NMSS, the Nuclear Materials Safety and
Safeguards Office. Their presentation summarizes emerging
issues relating to fabrication and transportation of fresh
fuel and storage and transportation of spent fuel.
The Office of Research has played a prominent role
in preparing this presentation and overall in addressing
some of these issues, so I want to turn this meeting over to
them to introduce the technical presentations and to
summarize the overall status at the end. Tom?
MR. KING: Thank you, Joe.
. 6
If I could have Slide 2, please.
[Slide.]
MR. KING: Slide 2 shows the outline of our
presentation this morning. As Joe mentioned, the purpose is
to update the Commission on issues related to high-burnup
fuel performance and the Staff activities to address those
and this is a followup to the November 25th, '96 memorandum.
That memorandum focused on two prominent issues, primarily
the control rod insertion issue and the fuel performance
related to reactivity insertion accidents.
However, high-burnup affects a lot more than those
two areas and today we intend to take a more comprehensive
look at the issues and the activities that are underway to
address those issues.
Accordingly, that is why we have all four offices
involved, because we are -- it is an integrated activity and
we want to --
CHAIRMAN JACKSON: Who is integrating? Who is the
point person? I mean who has the responsibility to ensure
that the activities in fact of the different offices
properly inform each other and are integrated?
MR. KING: Well, I think we have been trying to do
that at the division level. Certainly, within Research our
counterpart is Gary Holahan and his people and we work
closely with them --
. 7
CHAIRMAN JACKSON: No, I understand what you are
telling me but I guess what I am really asking you is is
there a lead individual with respect to the activity so
that, you know, everything informs everything else?
I mean I understand that you have been looking at
international, you have been looking at domestic, you look
at specific fuel issues, and I am probably somewhat more
familiar with what you have been doing in the research area,
but a concern is to have some coherence, so is there an
individual identified who has the lead in this?
MR. KING: At this point I don't think we have one
individual identified.
CHAIRMAN JACKSON: Okay, so it is kind of an
emerging activity?
MR. KING: It is an emerging activity. As I said,
we are trying to integrate it at the division level among
the offices.
CHAIRMAN JACKSON: Okay.
MR. CALLAN: Chairman, we will look at that. That
is both good and an obvious thing that we ought to be
looking at and we'll make a recommendation.
MR. MEYER: Could I jump in here and say --
CHAIRMAN JACKSON: Sure.
MR. MEYER: -- we do have this generic issues
management system.
. 8
It is identified as a generic issue and I am the
Manager for the generic issues so there is some coherence at
least at the working level right now.
CHAIRMAN JACKSON: I understand that. That is a
separate question.
MR. KING: Okay.
CHAIRMAN JACKSON: But anyway, good, Joe. That
keeps me from having to put it in my closing remarks.
MR. KING: Okay. The handout is a fairly thick
package. What we intend to do today is not show every
viewgraph. Some are provided here for information, so we
will be skipping over some and just hitting the highlights.
If I could have Slide 3, please.
[Slide.]
MR. KING: What I want to talk about for the next
few minutes on the next three slides is provide an overview
of the issues and then a little bit of background as to what
led up to these issues.
We have broken down the fuel performance issues
into two basic categories, in-reactor and out-of-reactor we
have labelled them. However, qualitatively many of the
issues are the same. For example, cladding integrity is
important in-reactor and out-of-reactor.
As you mentioned, Chairman Jackson, high-burnup
fuel represents a trend in the industry to reduce costs of
. 9
electricity production and it is being done in conjunction
with things like longer operating cycles, reducing storage
costs, and also things like power operating.
To achieve improved fuel performance the industry
is pursuing several things. They are looking at new
cladding materials. They are looking at higher enrichments.
They are reducing some of their operating margins and they
are radiating materials for longer periods of time.
High-burnup was also leading to certain changes in
certain fuel characteristics. Among these are higher
cladding oxidation which leads to embrittlement of the
cladding, higher fission gas release which leads to higher
pin pressure and higher source term fission gas release
source term component.
We are seeing different thermal and physical
characteristics of the fuel, for example, fuel
conductivities changing. We are seeing fuel fragmentation
take place as the burnups get higher. We are seeing a shift
in some of the failure modes of the fuel. We are seeing
certainly the higher radionuclide inventory as decay heat
builds up with higher burnup.
These things have led to some unexpected results,
some of which you are aware of -- the failure at low energy
inputs from the French tests and Japanese tests on
reactivity insertion accidents, control rod insertion
. 10
problems at some plants in the U.S. as well as overseas.
We are seeing some different failure modes, as I
mentioned, cladding, brittle cladding failures, and fuel
expulsion in some of the tests, and we are seeing larger
fission gas released from fuel, higher than had been
expected.
All of these things indicate that we need to look
at our codes and criteria to update them and evaluate their
current applicability to high burnup and all of these things
also affect a number of areas. They affect normal
operation. They affect anticipated operational occurrences
and design basis events and analysis that we do in the
severe accident area.
These things are shown on Slide 3, if I could have
Slide 3, please.
[Slide.]
MR. KING: Traditionally fuel cladding has been
the first barrier in what we call defense-in-depth and the
criteria we had developed many years ago to deal with fuel
integrity had generally kept the risks from fuel failure low
during normal operation, anticipated operational
occurrences, and design basis events.
[Slide.]
MR. KING: The criteria, on Slide 4, we have shown
the criteria pictorially. They have been established
. 11
basically for normal operation and anticipated operational
occurrences. The intent of the criteria are to maintain
cladding integrity and basic -- and allow, provide for safe
shutdown of the reactor and basically they correspond to no
release of fission products to the environment.
For postulated accidents, which include reactivity
insertion events, loss of coolant accidents, the criteria
are directed toward maintaining safe shutdown, coolable
geometry and the applicable criteria are the Part 100 dose
guidelines that have to be met during those accidents.
For severe accidents we don't have any limits on
fuel integrity but clearly the fuel performance affects the
source term and the core melt progression. That is assumed
in risk assessment.
CHAIRMAN JACKSON: Let me ask you this question.
Of the postulated accident conditions that you have on Slide
3, which are the greatest contributors to risk?
MR. KING: It's somewhat plant-dependent. In some
cases we see LOCAs as the biggest -- as larger than the
others in contributing to risk. In other cases we see a
contribution from ATWS. Never have I see the rod drop or
rod eject accidents be a prominent contributor to risk.
MR. HOLAHAN: And the contributions are not from
the design basis ATWS or LOCA, which is a mitigated event,
but it is the related severe accident.
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CHAIRMAN JACKSON: Right, severe accident, and
where have we been focusing our attention to this point?
MR. KING: Our attention from the experimental
programs that are underway have been on the rod drop and rod
ejection accidents. We are now shifting that focus to LOCAs
and the ATWS.
Of the criteria that have been developed and are
currently in place, developed a number of years ago, based
upon data from primarily tests with fresh fuel and fresh
cladding or cladding and fuel that had achieved low burnup.
It had also been based upon zircalloy and zirlo cladding,
and with the new cladding that is being developed by the
industry, some of the properties are clearly going to be
different than what has been used in the past to establish
our criteria, so the goal of our work is to continue to
assess our criteria and our codes so that we can assure that
the risk remains low from fuel performance issues.
We don't think there is immediate safety concern
in this area for several reasons.
One, the accidents remain low probability.
Two, it takes time to achieve high-burnup.
Three, we think from the data that we have
received to date and the direction we feel the criteria are
going to go, we feel that plants will be able to -- like be
able to meet these criteria once we get the revisions made
. 13
and get them in place.
CHAIRMAN JACKSON: This is kind of a curve ball,
but is it true that there was an observation with MOX fuel
in Europe that at low-burnups then what we consider to be
high-burnups with uranium dioxide based fuel, that there was
some fuel damage for, you know, an energy insertion where we
wouldn't have expected it?
MR. KING: Yes, there was a recent test in France,
I believe. Maybe Ralph could --
MR. MEYER: Can I take this? This was a test in
the test series in the CABRI reactor in France.
The fuel rod did have a fairly high-burnup. It
was 55 gigawatt days per ton. What they have been testing
to in that same test series has been a little higher, up
around 60-63 gigawatt days per ton.
I personally thought that the failure that
occurred in this test was totally expected. It failed
around 110 or 120 calories per gram during a reactivity
transfer, which is exactly where I think the rest of the
data are telling us the failure should occur.
What did happen was that there was a larger
pressure pulse generated in this test than in other tests
but it had a total energy deposition that was higher than
the other tests they had performed so there is some concern
that the microstructural changes in the pellet due to having
. 14
more plutonium in there may lead to additional fragmentation
and some increase in this fuel-coolant interaction that
leads to the pressure pulses, but at this point I think that
remains to be seen.
I thought it was a pretty normal test but I know
even the people that performed it were a little surprised at
the energetics of it.
CHAIRMAN JACKSON: Thank you.
MR. HOLAHAN: I think what all of this experience
has at least taught me is it's really the condition of the
clad before the test or before an accident that's the
primary driver of whether it fails or doesn't fail during
the test. And then I think there are other contributing
considerations like where the energy is being generated in
the fuel pellet and the fact that MOX fuel has a little bit
different reactivity characteristics. I think largely what
we're seeing here, the low-energy failures are because of
the condition of the cladding. That's the primary issue.
CHAIRMAN JACKSON: Okay.
COMMISSIONER McGAFFIGAN: Could I ask just in a
clarification, when you use numbers like 6 -- 60 gigawatt
days per metric ton, is that batch average, peak, rod,
what -- just so you all stay on the same language all
through the briefing.
MR. MEYER: When we talk about an individual test,
. 15
it's the actual burnup in the test section that's being
tested. These test sections are a little over a foot long,
and they come from locations in the rod where the burnup
profile is pretty uniform. So when we talk about a specific
test it will be for the fuel in that test. It's fairly
constant. You'll see that requirements are often quoted in
different units, and it makes a pretty big difference. The
French, for example, talk about their limit at 47 gigawatt-
days per ton. This is an assembly average number, whereas
we talk about our limit at 60 gigawatt-days per ton, and
that's the average for the peak rod. There's about a 10-
percent difference in the unit.
CHAIRMAN JACKSON: Okay. Tom.
[Slide.]
MR. KING: Okay. Slide 5 summarizes the out-of-
reactor fuel issues, and as I said earlier, qualitatively
many of these are the same as the in-reactor issues.
Cladding integrity is important in the outer
reactor area, the higher decay heat, you'll need the higher
cladding temperatures, clearly the higher oxidation that
occurs in the reactor is an important consideration out of
reactor.
The higher pin pressure that occurs due to higher
burnup is a consideration in any out-of-reactor issues.
The source term is another common issue due to the
. 16
higher radionuclide inventory, the potential for fuel
dispersal upon cladding rupture, shielding issues.
Criticality is an issue, both in the fabrication
and the transportation and storage side.
So even though qualitatively many of the issues
are similar, when you get out of reactor you're also talking
about differences in time scales at which you're looking at
the performance of the fuel as well as the descriptions of
the types of accidents that need to be considered.
If we could go on now to --
COMMISSIONER ROGERS: When you say something's an
issue, what do you really mean by that? Do you mean that
it's something that we don't have adequate data on or
adequate data don't exist, or it's just something that has
to be carefully included as one moves into higher
enrichments but that basically what needs to be known is
already known?
MR. KING: It could be some of both. Basically
when we identify things as issues in the beginning, they are
areas that we feel are affected by higher burnup that we
need to look into. In some cases we find there are data,
sufficient data to upgrade a code or revise criteria. In
other cases we find out there aren't and we need to figure
out a plan or a strategy to get that data.
COMMISSIONER ROGERS: Well, I wonder -- excuse me.
. 17
CHAIRMAN JACKSON: That's all right.
COMMISSIONER ROGERS: During your presentation at
some point before we all go home whether you couldn't touch
upon those issues where really additional data or research
are needed that just simply doesn't exist.
MR. KING: Yes. We're going to cover that as we
get to the -- Ralph covers the research program, Gary covers
the NRR activities, and Carl the NMSS activities. So we'll
cover that.
COMMISSIONER ROGERS: Right.
MR. KING: We can go to slide 7.
[Slide.]
MR. KING: Slide 7, you know, in a box diagram
shows the major components of the fuel research program that
exists today. It's broken out into three main areas that
deal with reassessing the criteria, updating the codes, and
getting experimental input to support these activities.
We also have another activity in the criticality
area looking at extending the criticality codes that are
used for fuel fabrication to higher enrichments.
And then up in the upper left-hand corner of the
slide I have a little item called mixed oxide fuel white
paper. That's an initiative we're undertaking in house in
research to do some homework in case we get involved in
reviewing applications for mixed oxide fuel, and basically
. 18
it's to look at what do we know from past work, what do we
know from what's going on overseas, and what are the issues
that we need to deal with if we get into a mixed oxide
review.
That's all we're really going to say about mixed
oxide. The rest of the presentation is going to concentrate
on the activities under way dealing with the operating
reactors today, and I'm going to turn it over to Ralph to
talk about --
CHAIRMAN JACKSON: Before you do that, if you look
at these boxes on page 7, does that cover the full scope of
issues that --
MR. KING: That research is looking at; yes.
CHAIRMAN JACKSON: Right. No, not that you're
looking at, but that have been identified.
MR. KING: I think the one area that we're looking
at that's really not in the research program --
CHAIRMAN JACKSON: Okay.
MR. KING: Is the difficulty with incomplete
insertion of control rods, and we're dealing with that
through operating experience with the vendors, not really
through a research program.
CHAIRMAN JACKSON: Okay, so you're going to talk
about that.
MR. KING: Yes.
. 19
CHAIRMAN JACKSON: Okay.
MR. KING: I think there may be some things that
come out of NMSS that may expand the scope of research
activities as well, and we'll talk about that.
CHAIRMAN JACKSON: Okay. Thanks.
MR. KING: Ralph will now describe the research
program.
MR. MEYER: Let's stay with slide 7 for just a
minute, because these are the main elements of the program,
and let me just touch on each of these before going on.
First of all, look at the center box at the bottom
of the page where it talks about updating our analysis
tools. We actually started this work before we had results
from CABRI or the control rod sticking problem came up, so
we had begun to modify the codes, and I'll give you some
additional details on the code work on a later slide.
CHAIRMAN JACKSON: You are going to address the
question of whether NRC codes can adequately predict fuel
and clad behavior at the burnups now being used by --
MR. MEYER: Yes, I can do that. I can do that
right now and say that the three codes that the NRC uses
that specifically deal with fuel behavior are the three
listed here. The first one is a steady-state fuel behavior
code. FRAPCON is an evolution of an older code, GAPCON,
that many people have used.
. 20
This code and its predecessor are used routinely
in licensing reviews because one of the main outcomes of
these reviews depends critically on something you calculate
here, that is, the loss-of-coolant accident analysis, the
ECCS behavior is very strongly dependent on the stored
energy that's in the fuel rod at the beginning of that
accident. That's calculated in detail with this code, each
of the vendors has a reviewed corresponding code, and this
code is used as an audit tool to check their work.
This code has been updated to handle burnups up to
at least 65 gigawatt-days per ton. That work has recently
completed -- the final peer-review meeting on that code is
next week, and the release of the code will follow as soon
after that as we can respond to any things that come up in
the meeting next week.
The transient code is not used routinely in
licensing but it's used from time to time for special
studies, and also particularly for analyzing experimental
results. We are just under way in making revisions to that
code. We kind of have to do these one after another because
it is the same contractor and we don't have many people
working in this area these days. So that work is under way
and will take a year or so. But we're still able to use the
code during this time if we know exactly where its
deficiencies are and can keep an eye on them.
. 21
The RAMONA code, transient neutronics code, has
been used for our high-burnup calculations, and it does have
some significant uncertainties associated with high-burnup
applications, and we have looked into those uncertainties.
We have not made any adjustments yet to the code for that.
CHAIRMAN JACKSON: So that's the third in a row?
You said you had one contractor.
MR. KING: No, I'm sorry. You can't read my mind.
No, we actually have two contractors. We have one
for the thermal mechanical fuel behavior codes, and a
different one for the neutronics code. That work has been
going on simultaneously.
CHAIRMAN JACKSON: Okay.
MR. KING: Okay. So at about the same time we
started the code work, this was about 4 years ago, we also
started looking at the acceptance criteria that we use in
regulatory work that related to fuel behavior. I think of
these as speed limits that are related to fuel behavior.
And we'll talk more about those as well.
So that's sort of assessment work, and then we
have some experimental programs. Now most of our
experimental work at this time is brought in from overseas.
All of the work on the reactivity accidents, the recent
work, was done overseas. Of course we have a tremendous
amount of work in our historical existence on this in the
. 22
old Spartan PBF reactors. And we have in fact gone back and
looked at those data as well.
But as you saw earlier in the discussion, the
loss-of-coolant accident in our view is at least as
important, probably more important, than the reactivity
accident from a risk point of view, and so we decided that
there was not enough work, experimental work, being done on
the loss-of-coolant accidents, and is something where we
still have the expertise in the U.S. and where we can get in
the game and actually do some experimental work. So we have
initiated a program. I'll talk about that briefly on a
later slide.
The Halden program in Norway is providing sort of
baseline thermal properties for the computer code
development, and we utilize those data.
Finally then on the mixed oxides, what we plan is
in the near future to do a sort of review, a white paper, on
the effect of the mixed oxides on all of the same things
that we're looking at at high burnup. These will be I
expect modest effects rather than huge effects.
MR. HOLAHAN: If I could go back to your earlier
question, Dr. Jackson, I think it's fair to say that the
experimental data is in some sense used in developing or
verifying at least the first two codes, because the steady-
state analysis can be compared with Halden, and the
. 23
transients analysis can be compared with the tests. The 3-D
neutronics really don't have, you know, an experimental
facility to be compared to, but there are code-to-code
comparisons that are done to give you some comfort in the
capability of that code.
MR. MEYER: Okay, slide 8.
[Slide.]
MR. MEYER: Well, the objective in a word is to
maintain the technical expertise here that we need, and I'm
not going to dwell on any of this, but you'll see that in
doing this that our work is focused on the in-reactor
issues, and here we have made a distinction in the past.
We've talked about technical issues versus regulatory
issues, and -- but we've focused our work on the technical
issues where questions arise that might have a regulatory
impact is where we have turned the spotlight, and we've done
this by trying to keep our codes up to date, getting data
from other programs, as I mentioned, we have a lot of
involvement with the international programs, and we also
have some recent initiatives with industry groups and DOE to
try and get some cooperation going. We'll mention more of
that in just a minute.
CHAIRMAN JACKSON: Let me make sure I understand.
What NRC regulatory criteria, you know, fuel --
MR. MEYER: Okay.
. 24
CHAIRMAN JACKSON: Or burnup damage limits might
be affected by --
MR. MEYER: Okay. If you think about that pyramid
from slide 4 or 5, whatever it was, for each of the design-
basis accidents, and there's just a handful of design-
basis accidents that we use in licensing, the most prominent
of those is the loss-of-coolant accident. So let me talk
about the loss-of-coolant accident for a minute.
The main speed limit or regulatory criterion in
the loss-of-coolant accident is that after you go through
this big transient that you maintain the coolable geometry
of the core. And you do this by demonstrating in an
analysis that the peak cladding temperature remains below
2,200 degrees Fahrenheit and that the oxidation that occurs
during that transient remains below 17 percent of the wall
thickness being oxidized. That's the way it's laid out in
10 CFR 50.46.
Then you have models that you have to use to
calculate those things, and those models involve the
oxidation kinetics, the occurrence of rupture of the
cladding, the amount of strain, how big does the balloon
grow, and how much blockage does this cause in the core.
All of these things are affected by the ductility of the
material and its mechanical properties, which are in turn
affected by the fluents and the oxidation that it gets as it
. 25
goes to higher and higher burnups.
And all of the testing that was done to establish
the 2,200 number, the 17-percent number, the Baker-Just
oxidation kinetics that have been used extensively, and the
models that are embedded and improved and stamped and locked
in the vault for these codes were all based on tests with
fresh fuel rods back in the seventies.
CHAIRMAN JACKSON: Okay.
MR. KING: For example, the concern is you get a
lot of oxidation as you proceed to higher and higher
burnups. That tends to eat into the 17-percent criteria
that's in the regulations. The cladding becomes embrittled.
You don't get the balloon and rupture type failures anymore
with the brittle cladding. So we're looking into what kind
of failures are we going to get and do we need to change our
criteria or not.
MR. MEYER: Now, there are also criteria for the
rod drop -- rod ejection accident, there are a whole bunch
of criteria for the normal operating regime, 1-percent
cladding strain, fuel rod pressures versus the system
pressure, lots of little things, but the big one gives -- I
think characterizes the situation.
MR. HOLAHAN: There's one additional difference,
and that is for the LOCA the criteria and the methods of
analysis are pretty much in the regulations. In most of the
. 26
other areas the regulations call for some requirement, but
in most cases they don't specify what the criteria ought to
be or how to do the calculation. And so there's either a
regulatory guide or a case-by-case review to establish
those.
CHAIRMAN JACKSON: Commissioner McGaffigan.
COMMISSIONER McGAFFIGAN: Could I ask how high are
we prepared -- is our research program aimed at looking at
burnups? The DOE program that may or may not be funded by
Congress says one of its goals and objectives of the spent-
fuel minimization R&D program is to reduce the amount of
spent fuel generated in nuclear powerplants. The principal
areas of research include resolving technical issues with
current high burnup fuel at 60 gigawatt-days per metric ton,
developing fuel performances supporting 100 gigawatt-days
per metric ton burnups, and analyzing, et cetera.
Do we have anything in our codes or our research
experience that if DOE were to pursue that program we'd be
able to be comfortable with 100 gigawatt-days per metric
ton? I assume that's peak rod burnups.
MR. MEYER: We are familiar with the DOE proposal
and the degree of cooperation that would exist would provide
us with the basis for making the adjustments that we need to
make, but we are not at this time moving toward 100
gigawatt-days per ton. We are operating with peak rods in
. 27
the neighborhood of 60 to 62 gigawatt-days per ton. There's
probably a need for a little elbow room there, maybe, I
don't know, 65 or 70, and I think when you see the
underlying phenomena that take place as you accumulate
burnup that you can develop the ability to extrapolate a
little bit.
I mean, what we see is the breakaway oxidation
phenomenon that occurs around 40 to 50 gigawatt-days per
ton, and this is the culprit. This is why the earlier
requirements which were based on data out to around 40
gigawatt-days per ton didn't just work at higher burnups
because something happened. We know what happened now, and
of course there would be the question if you get up to 100,
is something else going to happen, and you would indeed need
a data base, but if, you know, if DOE goes forward with that
program, the program itself is to generate that data base.
COMMISSIONER McGAFFIGAN: But that would also as I
understand it -- what the goal, since this is called waste
minimization, would be to be able to keep for three
cycles -- three 2-year cycles -- the rods in, you know, a
fresh rod being able to stay in for three 2-year cycles in a
reactor rather than two, which is typical I guess today, and
to do that they'd have to go to 7 percent enrichment, as I
understand it, if they were going to get all the way to
that, how far are you extrapolating or how much -- if they
. 28
pursue that program, I guess I'm basically asking what do we
have to do and what costs are there going to be for us to
sort of stay abreast of it and be ready to act on it should
somebody come in and ask us to act on it?
MR. KING: We haven't sketched out the costs that
would be associated with trying to respond to the DOE
program. We currently have steady-state irradiation data
out to the low seventies in terms of burnup, and we have
transient data particularly for the RIA's out to the mid-
fifties, low sixties. If DOE is going to go up to something
like 100, we currently don't have the data, and we have --
CHAIRMAN JACKSON: Is it also based on enrichments
of 5 percent or less?
MR. KING: Yes. The French and the Japanese tests
are based on enrichments of 5 percent or less. The Halden
steady-state data that goes up to the low seventies I'd have
to check, but if it's greater than 5 percent, it's probably
not much greater.
COMMISSIONER McGAFFIGAN: Is there anyone else in
France, which is a leader in I guess this area, or at
least -- or Japan or whatever -- who's looking at trying to
get to these sorts of waste-minimization goals. This partly
comes up, Madame Chairman, because, you know, in this
convention on waste that's being negotiated at the moment,
this notion of waste minimization is in there, and we don't
. 29
have much of a -- it's not really in our regulatory
framework, and I'm trying to understand whether, you know,
there's going to be impetus as a result of this waste
convention should it be negotiated for us to do something
like this to meet a waste-minimization objective of some
sort.
MR. KING: I don't know of any overseas program
that's trying to -- has the goals of the DOE waste-
minimization program.
CHAIRMAN JACKSON: The same countries that we
might look to to get the data also happen to be ones that
reprocess, and that's also part of their waste-minimization
strategy.
MR. KING: When we get to the last slide on
concerns you'll see one of our major concerns is the impact
of this DOE waste-minimization program on --
COMMISSIONER McGAFFIGAN: Okay. I'm sorry to have
jumped the gun.
CHAIRMAN JACKSON: No, no, no; that's a good
question.
MR. HOLAHAN: I think it's also fair to say that
our experience to date has taught us that what we should be
doing if increasing burnups at all is to be doing it in
measured steps, and long before we thought about anything
like a hundred, I think we need to think about 65.
. 30
CHAIRMAN JACKSON: Why don't we let you get
through a few more viewgraphs, because I think we always
seem to preempt what you may have had in mind.
[Slide.]
MR. MEYER: Okay. Well, look at slide 9, and I
think that we already talked about almost everything on this
page as a result of some of the early questions, so we can
move on, and we're skipping 10 and 11, so that moves us
right to the schedule.
A few comments about the reactivity-initiated
accidents. These programs that we've been talking about in
France and in Japan are in my opinion at a point now where
we're on a plateau of understanding, and it's going to be 3
to 5 years before they're able to reset these programs,
revise their hardware, and get improved data. So we did an
interim assessment of all of the data, and in fact issued a
research information letter summarizing these data and
suggesting some revised criteria for this accident. That
was issued just on the 3rd of this month.
New test results are hoped for from both programs
in France and Japan. In France in particular I'm sure
you've heard talk of this water loop that they're hoping to
construct and do tests in that would be much more typical
than the current liquid sodium loop. So, you know, in about
5 years I expect that we would have a significantly improved
. 31
data base and can go back and revisit that. But I think
we've provided a technical basis for an interim position
should we decide that such an interim position is warranted.
Loss-of-coolant accidents, our work is under way.
We are working with EPRI and DOE. They intend to help us
identify and acquire specimens of fuel rods burned to high
burnup in commercial U.S. power reactors, and will share
some of the costs of acquisition of the specimens and the
shipping and initial preparation, but then of course we'll
run our own program when we get them up to the hot cells.
That work will include both loss-of-coolant
simulation tests and also some general mechanical properties
testing over a range of transient conditions that should
be -- that we intend to be applicable both to the loss-of-
coolant-type transients, the reactivity-type transients,
everything in the range of the accidents and transients that
we have to look at in our safety analysis.
Also anytime you work with irradiated fuel rods
it's kind of slow going, so this is a 3- to 5-year program
to get significant results as well.
The anticipated transients without scram, the
ATWS, there's one ATWS, the BWR power oscillation, that
we're going to look at analytically. At first we're just
going to try and size it up. It does have some rather large
power oscillations. The timing of those is quite different
. 32
than the timing in the pulse of a rod-drop or rod-ejection
accident. So at this point it's not clear whether the data
that have come from these pulse tests can be applied to the
power oscillations, and that's what we're going to try and
shed some light on with some calculations that we can do in
the near future, and we're going to do that.
CHAIRMAN JACKSON: No experimental program?
MR. MEYER: Nothing planned.
MR. HOLAHAN: We are also and over the last few
years have been working with the BWR owners' group on their
emergency operating procedures to minimize the likelihood
that unstable oscillations would occur during an ATWS, so
we're looking at prevention at the same time that we're
looking at the potential consequences of power spikes if
they would occur.
MR. MEYER: And finally the source term is this
fall we're going to begin looking carefully at source-term
issues. There will be some small changes in gap inventory,
the fuel particulate size will be different, there's some
shift in the isotopics, but in general I would characterize
our expectation as a small step change in going from the new
NUREG 1465 source term to one that accounts for a high
burnup compared to the big step that was taken between the
old TID source term and the 1465.
CHAIRMAN JACKSON: But at this point the new
. 33
source term does exclude high burnup fuel?
MR. MEYER: That's correct.
Okay, Gary Holahan from NRR is now going to talk
about the NRR activities on high burnup fuel.
MR. HOLAHAN: Slide 14, please.
[Slide.]
MR. HOLAHAN: The general industry trends have
already been mentioned by Tom in his opening remarks. I
don't think I need to go over those again.
CHAIRMAN JACKSON: Let me ask you one quick
question.
Are we able to adequately audit industry core
reload analysis for high-burnup fuels and how do we ensure
that safety margins are maintained with different fuel
designs and changes to fuel designs at high-burnup
conditions?
MR. HOLAHAN: We really have a program that has a
number of pieces to it. One is that when a new fuel design
is proposed, usually from the vendor is some sort of topical
report, the Staff does review and approve that and looks at
many of these issues -- cladding stresses, the effect of
increased burnup, lead test assembly program to demonstrate
what is included in the analysis.
In addition, the Staff will review and approve
individual reload analyses where there are changes in the
. 34
technical specifications so at that point we would review
changes in fuel design or changes in methodologies and we
would review the codes involved at that point.
What we have really been stressing in recent years
is a shift from that sort of review and approval mode into
more of an inspection type activity and so over the last few
years we have inspected all of the fuel vendors. I think
over the last approximately two years we have done about
nine major inspections at GE, Westinghouse, ABB, CE,
Siemens, and we have also --
CHAIRMAN JACKSON: Now how does that track to
actually dealing with the industry core reload analysis?
MR. HOLAHAN: In many cases -- reloads are really
done in two ways.
Some licensees do their own analysis. Many of
them rely upon --
CHAIRMAN JACKSON: The vendors?
MR. HOLAHAN: -- the fuel vendor to do the
analysis, so as part of our inspection of the fuel vendor
activities we not only look at, for example next week we are
looking at Siemens and their fuel manufacturing activities,
but last week at Siemens we were looking at their codes and
thermal hydraulic analysis.
So we look at --
CHAIRMAN JACKSON: We look at the adequacy of the
. 35
codes.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: We look at how much they are
extrapolating beyond existing data.
MR. HOLAHAN: On an audit basis, yes. Now
recognizing that for example we may only spend one week with
a few experts to go and look at a code, so we can't cover
100 percent of what is in those codes but we do try to
select those areas that seem to be significant.
We use not only experienced inspectors and QA
qualified inspectors but we also use our own thermal
hydraulic experts -- the people in this building who are
actually capable of running loss of coolant accident or
RAMONA type calculations. Those people are actually out
looking at the vendors' comparable analyses from a very
technical point of view.
CHAIRMAN JACKSON: Okay, but I guess what I am
really trying to get at is this, you know, when I was
listening to Mr. King here, I guess I am trying to get at
the issue of the adequacy of the codes as opposed to what
they do -- that is, are we really looking at the adequacy of
the codes or the regions of concern with respect to high-
burnup?
MR. HOLAHAN: Well, I have to say we do it
selectively.
. 36
We look at various codes in different ways. It's
probably fair to say that LOCA analysis gets more attention
than other areas, and so for example we do things like in
both our review and inspection activities we ask the
manufacturer, the Applicant, to compare those calculations
to LOFT experiments, for example.
So we do look for verification type activities
where it is possible.
Now there are not that many opportunities for
saying show me how your code can be demonstrated to be
useful at high-burnup, okay?
CHAIRMAN JACKSON: Right.
MR. HOLAHAN: I think as mentioned earlier we are
just beginning to do some experimental work to show how
high-burnup might affect the fuel rod performance for LOCA
activities, so the mode we tend to be in is in our review
and inspection activities we are dealing with sort of the
current state-of-the-art understanding.
Meanwhile, we are sort of pushing the state-of-
the-art with the research program, and then when we find
things that are new and different, we will go back to the
industry and say this looks like a legitimate issue that
needs attention -- what are you doing about this?
CHAIRMAN JACKSON: I appreciate what you are
saying, but I guess I am really trying to get at a specific
. 37
issue, which has to do with on what do we predicate a
regulatory decision with respect to core reload analysis,
and if, you know, what is being presented represents an
extrapolation beyond where there really is data, how does
that drive the regulatory decision?
MR. HOLAHAN: Well, I think in the past there have
been examples like that. In fact, you have heard some
examples where the original analyses were maybe based on the
35,000 megawatt days per ton and here we are allowing
licensees to go to 62.
In those cases what we are using is the vendor's
engineering analysis and our own judgment plus a lead test
assembly program which is supposed to demonstrate that their
assumptions are actually coming through in the field.
Now what we learned is that lead test assembly
programs, because they tend to be conservative -- for
example, we don't allow licensees to put lead test
assemblies which are in fact extrapolations in some way of
beyond what was done before -- we don't allow them to put
those in rodded positions, okay? Well, that is sort of a
prudent safety approach, but what it does is it eliminates
the possibility that you get any information on the
interactions of that design with a control rod in it.
So when we saw that there were a number of
difficult issues with burnup, control rod problems, issues
. 38
with the reactivity tests, we basically told the fuel
vendors more than a year ago that we would not approve any
increases in burnup until a number of these issues had been
settled.
I think that is -- the four major items I am going
to cover really are things that need to be better settled
before there are any other increases in burnup, but in the
meantime we are in the position where there are some
extrapolations from the scientific database to what is being
allowed in the field.
We are continuing to watch operating experience
and test data to make judgments about the safety of those
conditions.
CHAIRMAN JACKSON: Okay.
COMMISSIONER McGAFFIGAN: Were you expecting to
get applications for increases in burnup before that
analysis was made?
MR. HOLAHAN: Yes.
COMMISSIONER McGAFFIGAN: How high were they
likely to be asking you to go?
MR. HOLAHAN: Well, I don't know of any specific
examples but from general discussions of what the industry
is interested in, I think it would be fair to say that
65,000 megawatt days per ton and probably 70-72,000 megawatt
days per ton are things that are not too far off and to a
. 39
certain extent we have slowed down the industry's move to
those levels.
COMMISSIONER McGAFFIGAN: Was the intent to use
that fuel in this country or to use it for export to -- how
are other regulatory bodies dealing with this issue?
MR. HOLAHAN: I am not so familiar with the market
for fuel in other countries. I think at levels of 65,000-
70,000 megawatt days per ton that would be useful to U.S.
utilities in planning for a two-year cycle.
It would give, not that it is absolutely
necessary, but that it would give them additional
flexibility on how to design those reloads and it would
probably allow them to use some of the fuel more fully than
they currently can.
COMMISSIONER McGAFFIGAN: So at that level if they
want to run for two two-year cycles they could keep the fuel
in, fresh fuel rod could expect to last two two-year cycles
at that point?
MR. HOLAHAN: I think so, yes.
MR. KING: From industry papers I have read, the
numbers Gary has quoted are about what the industry is
targeting to achieve.
Overseas, France and Japan and others have set
burnup limits and utilities are trying to increase those for
economic reasons also and I think the numbers they are
. 40
shooting for are comparable to what the U.S. industry is
shooting for.
CHAIRMAN JACKSON: Do we have actual energy
deposition criteria that we use and does any of the foreign
data suggest that, you know, the energy deposition criteria
are violated at elevated fuel performance?
MR. HOLAHAN: Yes. I will address that directly.
CHAIRMAN JACKSON: Okay.
[Slide.]
MR. HOLAHAN: If I could have Slide 15 you will
see it is the first bullet on Slide 15. This is just a
summary of the four issues that I am going to cover -- clad
integrity during reactivity accidents is in fact exactly the
area where energy deposition tests is showing something
inconsistent with what is in our regulatory standard.
I also talk about the general aspects of fuel
performance with increased burnup, related topic of
oxidation buildup, or cladding oxidation during normal
operation and what we think needs to be done in that area,
and our ongoing dealing with the incomplete rod insertion.
I think we can skip 16 and go directly to the
technical issues, starting with 17.
CHAIRMAN JACKSON: Are you going to talk about
current licensing basis criteria? Are you going to come
back and talk about that?
. 41
MR. HOLAHAN: I am going to talk about it in the
context of each of these technical issues.
CHAIRMAN JACKSON: Okay. All right, and you are
going to talk about how -- what criteria you think need to
be revised?
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: Okay.
[Slide.]
MR. HOLAHAN: On Slide 17 the one -- this is the
one that we know needs to be revised, and that is cladding
integrity during reactivity accidents, rod ejection for the
PWRs or rod dropout for the boiling water reactors.
I think Tom mentioned it in his introductory
remarks. We don't consider this a significant safety issue
because of the low probability of the event and limited
consequences but we have seen in the data that our criteria
are not sufficient to prevent damage of the fuel and so what
we would like is to have good regulations based on good
scientific evidence, and what we have got now is new
information that shows that the criteria that are in our
regulatory guidance and have been used to license many of
these reactors are inconsistent with the experiments.
So we have a situation where we feel that those
criteria need to be revised. Now what we see is the
criteria need to be revised downward from something like 170
. 42
calories per gram, recommended value, interim value from the
Office of Research is 100 calories per gram. They have
recently sent NRR a letter with that and a few other
recommendations. We are in the process of dealing with
that.
We have been working pretty closely with them over
the last few years and the 100 calories per gram does seem
like a sensible interim limit.
CHAIRMAN JACKSON: Now you say it is not a
significant safety issue because of its low probability and
limited consequence, so what kind of timeline are you
operating on in terms of considering this recommendation
from Research?
MR. HOLAHAN: I think there are a couple of
aspects to it.
The recommendation relating directly to the
criteria, interim 100 calories per gram, we could be able to
make that decision relatively quickly.
There are some related recommendations with
respect to things like inspection of the fuel and I think we
need to work through that and think about the implications
of what kind of inspection. I think we don't know quite so
much about the implications on the operation of the reactor
system and what constitutes an effective inspection program
and how would it impact operation of the plant and so forth,
. 43
so we need to sort some of that out before we make a
recommendation.
COMMISSIONER McGAFFIGAN: Could I ask --
CHAIRMAN JACKSON: Please.
COMMISSIONER McGAFFIGAN: What is the effect of
going to 100 calories per gram on licensees, either fuel
cycle or utilities? Is there fuel out there at the moment
that will -- or configurations that will be affected?
MR. HOLAHAN: We don't think so.
That goes really to the fourth bullet, which is
where do get the analysis that shows that the revised
criteria are being met?
The industry has through its owners group done
some what I would call generic calculations which show that
typically both BWRs and PWRs are well below 100 calories per
gram for rod ejection or rod dropout, and that is because
they have gone to a more sophisticated analysis -- 3D
neutronics calculations.
In addition, it reflects the fact that in PWRs for
example the reactors are not run with rods in the highly
inserted positions as the reactors were originally designed
maybe two decades ago.
For improved fuel performance they are basically
run in unrodded configurations and so there is nothing to
eject really at full power and at intermediate powers it
. 44
is -- the reactivity worth available for ejection is really
lower than it was assumed in the mid-'70s when most of these
original calculations were done.
We are now in the position where we have some
generic calculations which say our revised criteria can be
met. The Staff is in the position to do some calculations
to say it is reasonably comfortable with it. But we have to
make a decision about whether from a regulatory point of
view whether that is sufficient because what we have got on
the licensee's docket is a very conservative analysis
against a non-conservative criteria.
I think that makes frankly for a sloppy regulation
and what we would like is through some mechanism to have the
licensees, hopefully through some generic calculation so
that they don't have to expend excessive resources on what
we have already said is a relatively low safety significant
issue, but I think it needs to somehow find its way into the
FSARs and into the regulatory scheme to get appropriate
analysis to show that the interim criteria are met.
I think at this stage we need to sort out what is
the best regulatory approach to doing that so technically I
think the plants can meet the 100 calories per gram criteria
but they just haven't done the analysis to show it -- so we
need to find a way to get from here to there.
That is also one of the things we are following up
. 45
on.
CHAIRMAN JACKSON: In rod insertion or ejection
events, the main ones would lead to concerns with energy
deposition?
MR. HOLAHAN: Those are the ones that have the
potential for getting close to 100 calories per gram. I
don't think there are any others.
I suspect very much that when the ATWS analyses
are done because of the shape, broadened shape, of the power
pulses there is more time available for the energy to
disperse into the coolant, and so I suspect that -- I would
say I am pretty confident that we are dealing with
delimiting cases here with the rod ejection and rod dropout.
COMMISSIONER ROGERS: What about power
oscillations?
MR. HOLAHAN: I think the BWR stability issues,
low flow or natural circulation, I think those are very
similar to what we are seeing in some of the ATWS
calculations and I think the power spikes can get very high,
but they don't tend to be -- the energy deposition is not as
limited in time as the rod dropout or rod ejection.
In addition, we have taken a number of interim
steps over the last several years so that we don't expect
to see the boilers having these problems. They have got
operating administrative controls in place and they are also
. 46
putting final solutions to these problems in place, for
example, reactor scram on the early oscillations to prevent
the larger examples.
So I think we do have delimiting cases here.
CHAIRMAN JACKSON: Might this change with MOX
fuel?
MR. HOLAHAN: I think probably there are a number
of issues with MOX fuel. The one that I am going to
speculate about, since we haven't studied it too well, we
know that the MOX fuel is more reactive in the sense that it
is -- because of the lifetimes and the prompt criticality
that you can get more energetic spikes, so I think that will
be an issue.
I think -- can you get greater than 100 calories
per gram spike with MOX fuel? I don't know but I think
there is more potential there than in the current uranium
fuel.
MR. KING: Yes, I would agree with that. I think
it is the neutron, the physics characteristics that really
need to be looked at carefully with MOX fuel.
CHAIRMAN JACKSON: Okay, thank you.
MR. HOLAHAN: If I can go on to Slide 18.
[Slide.]
MR. HOLAHAN: In terms of fuel performance, we are
talking about not just uranium fuel pellets but the whole
. 47
fuel assembly. As I mentioned earlier, we have informed the
industry that before there are additional increases, there
needs to be support for changing the burnup limits. Those
are in terms of test and analysis and taking research
information into account.
CHAIRMAN JACKSON: Where is, again, let me make
sure I understand, where is the de facto cutoff today?
MR. HOLAHAN: Well, we don't have a national
value. In effect, what the staff has done in the past is to
review each fuel design and to review the proposed burnup
limit that goes along with that design. So when a vendor
comes in and says they have identified a new XYZ type fuel
assembly, they need to propose and justify the specific
limit that goes along with that fuel. So there is a
spectrum also.
CHAIRMAN JACKSON: What is the range?
MR. HOLAHAN: The range tends to be in the 55 to
62. I think 62 is the highest. 62 gigawatt days per metric
ton uranium would be the highest, although others are 60 or
below. The 50 to 60 range, I think, is typical.
We have said, stop where you are and we need to
see -- we need to have the reactivity, LOCA and rod
insertion type issues resolved and more information on the
lead test assembly programs before we go any further.
I think one thing that is fair to say is the lead
. 48
test assembly programs have not been entirely effective in
giving us early warning of potential problems and we are
looking more closely at those. There is a tradeoff here.
Lead test assembly usually means that perhaps four
assemblies are put in among nearly 200 in a core and those
are ones that have not been tested previously so they have
some aspect of them. Either they are pushing some new
material or new design. We don't normally get lead test
assemblies pushed to limiting burnups because they are put
in nonlimiting -- they are generally put in lower power and
non-rodded positions. So the program is giving us
information on the performance of these new materials and
new designs but it doesn't really tell you a lot, in some
cases it doesn't tell you anything about how these designs
are going to perform at higher burnups.
So we need to have, in fact, a better way of
getting early information on high burnups. We may need to
change our view on lead test assemblies and to maybe have
them used in some staggered sort of way in which they are
allowed to be put into higher burnup locations because,
otherwise, you are just not going to get that information.
The third bullet on here really says in the
absence of anything else, operating experience is going to
teach us about the performance of the fuel. This is where
our information on control rod problems has come from. We
. 49
do learn about the fuel performance from looking at fuel
leakers. We do follow up on reports when there are a number
of fuel problems. We take that experience back to the
licensees and the vendors and have them deal with those
situations.
Typically, we are seeing maybe one, maybe two fuel
rods in an operating cycle which are failed for some reason
and although that number is small, in fact it is very small
compared to what was assumed in analysis and licensing of
the plants. We do want to learn from that experience. Even
if it is only one fuel rod out of 50,000 that failed, it
failed for some reason and we want to understand the root
cause. Is there some additional oxidation going on, is
there a water chemistry problem, are there vibration
problems associated with a given design?
So NRR, Research and particularly AEOD is looking
at operating experience to learn from it.
CHAIRMAN JACKSON: Now, wasn't there about a year
ago a licensee that had a fairly large number of leakers?
COMMISSIONER McGAFFIGAN: Calhoun.
MR. HOLAHAN: And I think Haddam Neck.
MR. CALLAN: But Fort Calhoun has particularly a
particularly acute problem there.
MR. HOLAHAN: I think as you go back in time, you
see the problems were more serious. I would say over the
. 50
past several years, fuel fretting and vibration has probably
been the dominant cause of failures. Ralph, you have
insights into that.
MR. MEYER: No, that's correct. The only thing I
could add is even these episodes of failures you have heard
mentioned, the numbers are still relatively small. My
recollection is that in the last four or five years the
largest single episode of fuel rod failures only involved
around 25 fuel rods.
CHAIRMAN JACKSON: Does that change the patterns
as such that it, you know, affects energy deposition at all?
MR. MEYER: I don't think so. The big reactivity
actions that we look at are very localized. The rod drop
and the rod ejection, which are the only ones that take the
reactor prompt critical, I mean, these are prompt critical
power bursts and they just happen in the vicinity of the
single rod that is ejected or dropped and I don't think the
presence of a couple leaking fuel rods in that region would
have any effect on this.
At operating temperatures, even leakers get dried
out on the inside. The moisture from the interior of the
rod is expelled so it is not present under most
circumstances to participate in some energetic reaction.
MR. HOLAHAN: Probably the primary consideration
is the physical condition of the cladding. If that fuel rod
. 51
is leaking because it is heavily oxidized or because it has
spalling on the surface or something, it is not going to
perform well during a reactivity transient but it is
probably not because it has a pin hole in it and it has been
leaking; it is probably because that particular fuel rod,
whatever is causing that fuel failure, is also causing it to
have lost its ductility and to be more likely to fail.
We are still dealing with a relatively small
number. I think it is somewhat instructive to think back to
the '70s when most of these plants were licensed. We used
to talk, and if you go back to the FSARs, they reference 1
percent fuel failures in a lot of the analyses. Well, 1
percent of 50,000 is 500. We never see 500 fuel rod
leakers. It is rare to see five and it is not unusual for
plants to shut down and remove one or two rods because it
does produce radiation and contamination in the plant and it
is a more efficient way to run the plant when it's clean.
CHAIRMAN JACKSON: If you look at the predicted
fuel fragmentation and dispersal into the coolant, how much
fuel is involved and how does that dispersal of the fuel
affect reactivity?
MR. HOLAHAN: Let me answer in two parts.
Historically, when we were concerned about fuel
fragmentation, we were talking about very high energy
inputs, 280 calories per gram. The primary issue, safety
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issue associated with that, was that energy deposition is so
high that not only will it rupture the cladding but it will
also have molten fuel and molten fuel dispersed into the
water. That not only damage that individual rod and
releases its reactivity but it can produce pressure pulses
in the system.
So that was the origin of what is the fuel
fragmentation concern. And I think we see -- I mean, there
are no designs out there that have any energy inputs that
are anywhere near 280 calories per gram.
Now, we have seen in the experiments and I think
realistically we could expect at relatively low energies to
see cladding rupture and fuel dispersal. I think there are
cases as low as 30 calories per gram, Ralph?
MR. MEYER: Yes, 30.
MR. HOLAHAN: But I think what we are seeing in
those cases is the dispersal of fuel pellets that have
already been fragmented, almost powdered. And what you've
got is hot, 600 -- well, I still do Fahrenheit. Ralph will
correct me. What you have is hot fuel but nothing near
molten fuel dispersed into the water. So we don't expect
that there are pressure pulses associated with that that are
a concern to the reactor coolant system or the vessel.
So at the relatively low energy that I think the
experimental data suggests that you can have fragmentation,
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if you had a rod ejection and you had embrittled fuel, you
could expect to get a relatively small amount of fuel
because, in fact, what you see is a rupture of the rod and
fuel from a given area dispersed into the coolant.
But I think that would make a very dirty primary
coolant system from a reactivity point of view but it
doesn't produce the pressure pulses and I think there is
very little likelihood of producing any, you know, doses
outside of the plant. But I think it will produce
contamination problems in the plant.
CHAIRMAN JACKSON: There would be doses inside the
plant. There are people inside the plant?
MR. HOLAHAN: Right. I think it would be a messy
cleanup problem.
MR. MEYER: Keep in mind, though, that the interim
criteria that we have suggested in this research letter
precludes the failure of the cladding. We believe that the
plants can meet the criterion where you can demonstrate that
the cladding won't fail, it won't crack, it won't open up
and so it would not let out any of these particulates.
CHAIRMAN JACKSON: At the recommended limits.
MR. HOLAHAN: At the 100 --
MR. MEYER: The 100 calorie per gram, with
screening to rule out the highly spalled rods that lead to
these unusually low ones like the 30 calorie.
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CHAIRMAN JACKSON: But not at the 170.
MR. KING: Yes. That is an important point. We
have recommended the number change from 170 to 100 but along
with that, we are recommending the intent of the criteria
change. Previously, the intent of the 170 was to define the
point at which cladding would rupture and you would have to
consider the source term. What we are recommending is the
100 would be the point at which the cladding maintains its
integrity and, because of fuel dispersal issues, we believe
that ought to be, the intent of that criteria ought to be to
remain below that so you don't have to worry about cladding
integrity.
MR. MEYER: It is a red line, not-to-exceed limit.
MR. KING: Then you don't have to worry about the
fuel dispersal issues, whether it is pressure pulse,
contamination, flow blockage or whatever it is. So that may
be a point that was missed before but that is part of our
recommendation.
CHAIRMAN JACKSON: Okay, so that is an interesting
one.
Commissioner McGaffigan?
COMMISSIONER McGAFFIGAN: Could you tell me the
relationship between the utilities and the fuel fabricators?
Do fuel fabricators today have guarantees in their
contracts? It is a competitive industry. Do they guarantee
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there will be no more than one per 50,000 and if so we pay
for the cost of cleanup? What is the -- how does that work
as a commercial -- I am looking for some degree of self-
regulation from the industry itself in this area, so how
does that work?
MR. HOLAHAN: I believe there are warranties. I
don't know the details of them. The staff doesn't normally
get involved in dealing with that.
MR. CALLAN: There are warranties, Commissioner,
and there is a lot of litigation. There is currently
litigation going on between Fort Calhoun and the vendor and
I am aware of others. So it is an area that the utilities
pursue through the courts.
CHAIRMAN JACKSON: Let me make sure I understand
one thing. Who has the ultimate responsibility to do the
core reload analysis?
MR. HOLAHAN: The licensee.
CHAIRMAN JACKSON: And that comes under Part 50?
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: 50 what?
MR. HOLAHAN: It depends on how they are doing it.
For example, if they are doing it within the constraints of
their existing technical specifications, I would say it is
part of their license and 50.36 defined what is in their
technical specifications, which frequently establish by name
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and version the codes that should be used and the criteria.
Where the licensee is using the vendor to do the
analysis, the licensee is still responsible. For example,
as a result of our Siemens inspection, we identified some
difficulty with one of their fuel designs which is to be
used in the Susquehanna reactor and we are meeting this week
with the licensee to say, this is a licensee responsibility.
The quality controls on that design are requirements that
derive from the licensee's quality assurance program, which
derives from Appendix B of the regulations.
So although we review and approve and inspect the
vendors, when it comes to dealing with the responsible
parties, we will go back to the licensees who are using that
fuel.
CHAIRMAN JACKSON: So 50.36 or Appendix B
completely bounds the universe?
MR. HOLAHAN: Well, we talked about LOCA analysis
and then, of course, there is a 50.46 requirement. And
probably I left something else out.
CHAIRMAN JACKSON: I am not so much trying to put
you on the spot in terms of being able to give me a list
but, rather, to know that for all licensees there is some
aspect of the regulation that bounds them.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: It is not all in license
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conditions or just tech specs.
MR. HOLAHAN: I don't think that we have
identified any issues that are not covered by the
regulations.
CHAIRMAN JACKSON: Where would it be if it is not
in the license itself?
MR. HOLAHAN: If it's not in the license, meaning
a specific license condition, those are technical
specifications, then I think it's in the general that says
the plant is going to be run in accordance with the
regulations. That is part of the license, and the
requirements are in the regulations.
MS. CYR: I mean, are the peak cladding
temperatures that are a part of 5046 in the ECCS which has
the 2,200 degrees and is specified there which has a big
impact on this, most of it as I understand it, and I can't
speak authoritatively, is in the tech specs, and it's mostly
in terms of the way their license conditions are specified
that enough criteria of various kinds which bound each
reload and then the analysis that they have to do -- deviate
from that as they move to a new one.
MR. HOLAHAN: And there are probably some examples
that are only in the FSAR and not specifically in the tech
specs.
CHAIRMAN JACKSON: Okay. I mean that's actually
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what I was trying to get at, whether some of this is in
parts of the licensing basis.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: That are not in the tech specs.
MR. HOLAHAN: Yes. I think we already talked
about slide 19 with the research work on the LOCA criteria,
and here again is as with the rod-ejection issue there's the
potential need for visual inspection if the condition of
fuel going into the reactor is going to play an important
role in how it performs later. That may or may not be the
case, but we'll deal with that as the issue is developed.
[Slide.]
MR. HOLAHAN: Slide 20 summarizes the issue of
incomplete control-rod insertions. I think recently we've
been dealing with Wolf Creek and South Texas and their
experience. We issued a bulletin back in last year to get
information from all the U.S. -- well, all the Westinghouse-
designed plants. In addition I think it's fair to say that
foreign reactor experience probably led the U.S. experience
in this area, and both we in research and AEOD have been
following that information with some of our individual
discussions with those regulators in those countries, and
also in some international-type meetings. And I think AEOD
has additional details on that if some questions arise.
In effect what we did last year was to tell plants
. 59
with a Westinghouse design that we wanted more information
to verify that their control rods were inserting as
required, and that was a bulletin that ran from I think
about the spring of last year through the end of the year.
It was a one-time bulletin that sort of had a deadline on
it. In that period 35 tests were done. Some tests were
done more than once at a given plant, so 35 tests is not
exactly 35 plants. What we found is that in all cases the
technical specifications were met, and those specifications
are on the timing of the rod insertion. But what we also
called for in the bulletin was more sensitive measures of
how the control rods were behaving, early indication of
potential problems. One thing that was looked at on the
slide is called drag criteria, which is the amount of force
necessary to pull a rod out of an inserted position. What
we found is a number of cases, and I'd be a little more
specific, what it refers to on the slide is nine tests, and
what we actually found is there are really two areas of
interest.
In the bottom of the fuel assembly, the last few
inches, there's something called a dash pot, where the area
is reduced intentionally to slow the rod down as it gets to
its final resting position. So one would expect that to be
a tighter fit than the rest of the rod, the rest of the
thimble tube where the rod goes down. In fact the thimble
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tube is the more important area because the last few inches
do not have much reactivity associated with them.
What we found from those 35 sets of tests was
three plants which were above the drag criteria in the dash
pot, and these are criteria established by Westinghouse as
part of the design of the fuel assemblies. We found another
six where there were unusually high values which I would say
were precursors to exceeding the criteria. In the thimble
tube area, that is the major part of the fuel assembly, we
saw six plants that were above the criteria and another
three where it was higher than expected. So these were
early warnings that even though that fuel is still within
the specifications and doesn't have a safety problem, we're
getting early warnings that those need to be looked at.
Recently the South Texas plant, which has 14-foot
core as opposed to the 12-foot cores in all the other
plants, and which appears to be more susceptible to
difficulties with inserting the control rods, Unit 1 did
tests in January, and Unit 2 did tests in February. The
Unit 1 tests were mid-cycle tests which were done at the
staff's request, and they had two rods stick at six steps,
which means within about 4 inches of the bottom of the fuel
assembly -- that is to say, it was completely inserted
except for the last about 4 inches. And two additional rods
which we call no-recoil, which is to say when they reached
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the bottom of the fuel assemblies, they didn't bounce, and
one thing we look for is you can tell something about the
velocity that the fuel rods -- excuse me, the control rod is
inserting by whether it bounces when it gets to the bottom.
So these are even precursors to precursors in a sense of
degraded performance. Unit 2 had four rods stuck at six
steps, and one rod stuck at 12 steps. So they are
continuing to see what I would say is degraded performance,
and the staff is requiring the South Texas plant to do
additional mid- and interim-cycle testing.
Lastly on the subject we have a followup bulletin
under review. We have a date with the CRGR in the near
future which will basically identify for rodded assemblies
we would suggest guidelines for fuel management, additional
testing and analysis, and also give the licensees the
alternative to propose some other approach to dealing with
this issue. So we would put out a letter asking them what
they are doing in this area with some suggested guidelines
that we've got.
So that's basically our plan for dealing with the
ongoing issues with the combination of research activity and
dealing directly with the licensees. I think in the spirit
of getting a little bit back on schedule --
CHAIRMAN JACKSON: It's impossible. The meeting
ended three minutes ago.
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MR. HOLAHAN: Well, not getting additionally
beyond I think AEOD volunteered to skip their presentation
unless you have questions on the foreign experience.
CHAIRMAN JACKSON: What are your big points?
MR. ORNSTEIN: Well, the most important point that
I'd like to make is the fact that a lot of the problems that
have been arising in the States have had early warnings
overseas, and basically I refer to it as the cat -- you
know, the canary in the mine. Some of the issues that we've
seen unfolding at South Texas and Wolf Creek were presaged
by events overseas. Again, there's no single one-to-one
correspondence between a particular plant and its fuel and
fuel management here versus the States.
However, there are important features that we're
able to piece together, and as a result, we try to keep up
on it and see if there are certain aspects of it that are
important, like, for example, AEOD has been present in
virtually all the meetings that have been held with
Westinghouse folk and the people with Westinghouse plants
have had problems which the Bulletin 9601 came out about.
We've been continually pushing for the interrelationship
between people in the States and plants overseas, and
Westinghouse in turn has indeed, you know, followed and
tried to be, you know, connected.
When it comes to the French fuel, we have
. 63
different issues, but still it's an important information
flow that has been very helpful in our understanding of the
events.
COMMISSIONER McGAFFIGAN: Let me just ask, and
this, maybe it goes back to Mr. Holahan, on graph 24 or
chart 24 it talks about restrictions placed overseas, and it
says U.S. guidelines presently being considered. What are
our guidelines -- I think you just were referring to them --
what are our guidelines likely to say now that I have
numbers in front of me from other countries? Are we likely
to choose a burnup limit or require mid-cycle tests or where
are we headed? If you're the one to answer it, that's fine.
MR. ORNSTEIN: Well, no, actually in the
licensing, NRR indeed is the right organization. However, I
want to caution you that, you know, the types of fuels that
we see in some of these plants are not necessarily the same.
For example, there's a French fuel that appears in the
Belgian plants. They also have a similar Westinghouse fuel
that is performing a little bit better, and it's not a one-
to-one relationship. I think --
CHAIRMAN JACKSON: No, but even saying that, I
think that there's a broader way, if I may phrase the
Commissioner's question, I mean, clearly these restrictions
fall into certain categories having to do with burnup, you
know, drop tests, et cetera, and one could ask the question
. 64
irrespective then of the specific numbers, whether we're
moving along lines in these particular areas, and to the
degree that you can give some specificity I think it would
be useful.
MR. ORNSTEIN: Well, the important thing is that
there's been an evolution at these foreign plants as to --
CHAIRMAN JACKSON: No, no, no, no. You're missing
my point. My question is really -- Mr. Holahan.
MR. HOLAHAN: I understand, in the licensing
aspects. Okay.
CHAIRMAN JACKSON: Right. That's what I'm talking
about.
MR. HOLAHAN: I understand. In our draft of the
bulletin supplement we have taken in fact what Westinghouse
has suggested as guidelines and we're considering those or a
modification of those. What we think is, at least to this
point, probably not a single value of burnup limit is
appropriate. When you go back and begin to understand the
root cause of the problem, what it looks like is a burnup
limit for 12-foot fuel and for 14-foot fuel probably ought
to be different, because the 14-foot fuel assemblies are
less rigid, and are more easily distorted.
In addition, fuel -- additional grid spacers,
which are -- make the fuel assemblies more rigid and less
capable of distorting, probably also affects the appropriate
. 65
burnup. So what I imagine is we'll come out with a
guideline or maybe three separate guidelines, or at one
point we had six separate guidelines. But I think we'll
probably be down around three, that says for a certain type
of fuel a burnup limit of x, and for a different type of
fuel, burnup limit of y and z. And I could tell you that I
think right at the moment that x, y, and z are somewhere
between 25 and 40. Okay? But as recently as yesterday I
think the numbers changed, so -- and effectively I think
this is one of those generic communications that we'll put
out for public comment.
CHAIRMAN JACKSON: When are you expecting to
propagate that generic communication?
MR. HOLAHAN: Let me ask if -- it's fairly close.
Do we have a date with CRGR?
MS. CHATTERTON: The earliest date we would meet
with CRGR is April 8.
MR. HOLAHAN: April 8.
COMMISSIONER McGAFFIGAN: Are you also thinking of
mid-cycle drop tests. You've been doing it in South Texas.
Would that become a generic refinement?
MR. HOLAHAN: Yes. I think what we're thinking
about is an integral approach that says at certain burnups
you don't need to do mid-cycle tests. At higher burnups, in
fact the numbers we've been talking about are not
. 66
necessarily absolute prohibitions, there could be some
trigger that says if you're above 30,000 megawatt-days per
ton, that triggers the need for an additional mid-cycle
test, as opposed to an absolute prohibition for that to be a
rodded position.
CHAIRMAN JACKSON: But in some sense these
specific things deal with specific issues having to do with
rod insertions.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: But there are a whole host of
other considerations that would play into --
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: Some modification in terms of
restrictions. Is that not correct?
MR. HOLAHAN: Yes, that's correct.
CHAIRMAN JACKSON: They'd be dealing with the LOCA
kinds of analyses.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: These energy deposition
considerations that we were talking about.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: Okay.
MR. HOLAHAN: I think we're going to turn to Dr.
Paperiello.
DR. PAPERIELLO: We'll jump to slide 27.
. 67
[Slide.]
DR. PAPERIELLO: Tom summarized the overall NMSS
issues. The front end of the fuel cycle with respect to
criticality for enrichments above 5 percent, and the back
end of the fuel cycle for disposal or in the storage of
spent fuel with high burnup. The current approvals for the
fuel fabricators don't exceed 5 percent enrichment in U-
235. The reason -- and of course current manufactured fuel
is not above 5 percent, and if high burnup -- to achieve
high burnup we'd have to go above 5 percent. Some of the --
we would have to amend the licenses. And the issues on
criticality is computer codes used for criticality have been
tested and benchmarked against certain critical experiments.
There are a lot of critical experiments at 5 percent and
lower. There are a lot above 80 percent. There are very
few in between.
We don't have a well-established basis to
extrapolate either. We need benchmark data at the
enrichments we want to consider, or we have to build enough
conservatisms into our criticality calculations to allow
extrapolation. That is being worked on. We have research
is looking into the availability of benchmark data,
particularly overseas. We do believe the data exist. So
that's one set of issues.
The issue of criticality goes across the whole
. 68
range of both fuel-production facilities as well as packages
to transport uranium oxide, to pellets and finished fuel
assemblies.
[Slide.]
DR. PAPERIELLO: The other issue, if we go to
slide 28, is the issues on transportation and dry storage.
The two issues, and it drives a number of things, are again
very similar to the NRR's issues, the radionuclide
inventory, because this will determine how we do the
shielding and whether shielding is adequate. The cooloff
time, typically fuel is cooled for 5 years before it's put
in a cast. They give rise to temperature and the long-term
cladding integrity. If the cladding is running at a hotter
temperature, there is the potential for creep and for
oxidation. So we do not have an effort with research
currently. We propose to get an effort at research, but in
preparing for this meeting, it was clear that the NRR issues
in this area and my issues overlap and they will be
coordinated.
COMMISSIONER McGAFFIGAN: Could I ask on this
chart, you say spent-fuel vendors applied for the average
burnups up to 65 gigawatt-days per metric ton. That's --
we're talking in terms of what actually is in reactors 60 or
62 for peak, and therefore 40 or 45 for average batch,
right, so in some sense if we've been doing -- the cask
. 69
folks are well ahead of the industry if they've been
applying at this --
DR. PAPERIELLO: Right now I'm just -- right now
we have an application in, but it's not been approved.
Right now our approvals range in the order of about 40.
COMMISSIONER McGAFFIGAN: They're in the forties.
Thank you.
CHAIRMAN JACKSON: Go ahead.
DR. PAPERIELLO: I'm finished.
CHAIRMAN JACKSON: That was your presentation?
All right.
Who's the wrap-up.
MR. KING: I'm the wrap-up.
COMMISSIONER McGAFFIGAN: Could I -- before --
what are the implications for Yucca Mountain? I mean, of
going to higher burnups in the sense -- any analyses you
have to do to license a long-term storage facility.
DR. PAPERIELLO: I don't know. In fact as I was
sitting here that was a question I asked myself. I will
have to check. I would expect it to be the thermal issue.
I think in terms of the enrichment and the effect of
radionuclide composition is going to be bounded by the
putting of either vitrified plutonium or high-enriched, you
know, the submarine reactor cores in Yucca Mountain would
certainly dominate, but the temperature issue I don't know,
. 70
but I will check. That occurred to me in this presentation.
CHAIRMAN JACKSON: Okay.
MR. KING: Let me try and wrap up in 60 seconds if
we can. Slide 32 and 33 are the summary.
[Slide.]
MR. KING: The main points I wanted to come back
to were one, there's a lot of activities under way to deal
with the high-burnup fuel issues. They cut across a number
of our criteria and they cut across the offices. We have
activities and plans to deal with the in-reactor issues.
We're working with NMSS to develop plans to deal with the
out-of-reactor issues. The risk implications of the high-
burnup fuel performance. Our work is really geared toward
trying to maintain low risk from high-burnup fuel, and we
feel that that can be achieved, although there's still some
issues that need to be verified, particularly dealing with
the new phenomena we're seeing of fuel dispersal and higher
source terms and so forth. But what we're doing is we
illustrate it with the criteria, trying to develop criteria
that deal with those issues in a way that they don't
contribute any additional risk or any new types of accidents
to the plant.
In terms of concerns on slide 33 -- maybe concerns
is maybe a little too strong a word -- we feel cooperation
with industry is important, and it's two-way cooperation.
. 71
We've got a lot of our data from foreign sources,
experimental data. A lot of the details of that are
proprietary. We've been working with our foreign partners
to try and get that released to industry. Our industry's
very interested in that data. We've done that so far
through things like having special sessions at the water
reactor safety meeting, in a special issue of the Nuclear
Safety Journal. We'll continue to try and get that data
released.
We had a concern early on that industry was not
doing any experimental work in the transient area -- they do
a lot of steady-state work -- although we now have made some
progress in that area, at least reached an understanding
with DOE and EPRI to gain access to high-burnup fuel samples
that we could use in our program at Argonne that'll be
dealing with the LOCA performance.
We also made some progress in getting access to
industry steady-state data. There's a program called the
nuclear fuel industry research program that had been kept
proprietary. We now have got an agreement from EPRI to have
access to those reports.
Finally on the horizon we talked about DOE spent-
fuel minimization program. There's potential MOX fuel. At
this point we don't have any resources budgeted to deal with
those, although in the MOX area we are trying to do some
. 72
homework, and I think in the spent-fuel minimization
program, it would probably be wise to think along the lines
of a white paper to see what the issues are and the
implications are to that.
CHAIRMAN JACKSON: Let me ask you a couple of
questions. Can we go back to this issue of the current
licensing basis vis-a-vis fuel design? How do we ensure
that it is maintained when it is not in the tech specs?
MR. HOLAHAN: Well, in some cases it's in the
FSAR, but I think we know that there are cases in which an
important part of the licensing basis is only in some
topical reports and the staff's review and approval of
those. The staff has generated a number of recommendations
based on the Maine Yankee lessons learned activity that I
think we owe to the Commission this week or the end of this
month, pretty close. That's a combination both of the
staff's internal review of the Maine Yankee lessons learned
plus the Ed Jordan's ISAT team had a number of
recommendations related to the subject.
My recollection is it is about half, 11 of the 24
staff recommendations in this area go to the point of how
are codes reviewed and approved and how do you make sure
that it is in the licensing basis.
I think we have already started to move in that
direction. But I think it is fair to say that in the past
. 73
there have been examples in which code reviews and
licensees' commitment with respect to code calculations or
some of these other issues we have been talking about today
are in letters or topical reports and they are not captured
in the FSAR. So they are lower level commitment documents.
One of the things we have identified is an
activity to assure that when we review and approve things in
the future that approval of the topical reports are clear,
that the issues are in those reports and that when licensees
use these, they get them into either license conditions or
in the FSAR.
So I can't promise that is the way they were in
the past. I think we know of examples where they weren't.
But I think we have recognized it and are moving in the
direction.
CHAIRMAN JACKSON: Given that the Commission is
considering papers coming out of the Millstone lessons
learned and 50.59, are the activities and the
recommendations in those papers going to allow us to capture
what needs to be captured relative to this issue with
respect to the codes, fuel design?
MR. HOLAHAN: Yes. I would say the combination of
the 50.59 Millstone and Maine Yankee lessons learned,
together, definitely, I think, cover this issue.
CHAIRMAN JACKSON: How?
. 74
MR. HOLAHAN: Well, there are a series of specific
recommendations which I just happened to bring with me for
things like establishing standard in format guide for
topical reports, for assuring that the staff's questions and
responses to those are put in the approved versions of
topical reports, sample applications are all --
CHAIRMAN JACKSON: These are things coming out of
Maine Yankee.
MR. HOLAHAN: Yes.
CHAIRMAN JACKSON: I am saying to you, are they
included in the actions that are before the Commission for
the Millstone lessons learned, which is focused on the
current licensing basis issues?
MR. HOLAHAN: I think they have been coordinated
and both are owed to the Commission. But they are not all
in one document but they are all in the staff's plans.
CHAIRMAN JACKSON: Well, that is not quite the
answer to the question I am trying to understand.
MR. MIRAGLIA: Madam Chairman, in terms of
capturing commitments, I think the commitment discussion in
the Millstone Part Two would cover this. The specifics on
the codes are more directly related to Maine Yankee but the
efforts that we are doing in the captured commitments is to
make sure they are reflected in appropriate places, the
licensing basis, I think, would encompass that.
. 75
CHAIRMAN JACKSON: All right.
Let me just ask a separate kind of question. Is
the fuel designed to withstand the blowdown loads for a
large break LOCA and how is that affected by some of the
embrittlement issues and so forth that we are talking about?
MR. HOLAHAN: Well --
MR. MEYER: The answer is, yes.
MR. HOLAHAN: The answer is, yes. But most of
what we have talked about is the heatup of the fuel and the
LOCA concerns are not really during the blowdown.
CHAIRMAN JACKSON: That's right.
MR. HOLAHAN: And so these are really during the
heatup phase.
CHAIRMAN JACKSON: Exactly.
MR. HOLAHAN: But, yes, the criteria we have for
the fuel, structural integrity of the fuel assemblies and
the stress and strain limits and all of that do take LOCA
loads into account.
CHAIRMAN JACKSON: Are we explicitly considering
that as we look at this issue of embrittlement and loss of
ductility, et cetera, in the high burnup situation?
MR. MEYER: We are looking at that in the research
program but I have to say that we really haven't initiated
that part of the work. We identified it almost over two
years ago --
. 76
CHAIRMAN JACKSON: Is it unimportant?
MR. MEYER: No, it is not unimportant. In the
deep, dark past there were generic evaluations done, not
only for the blowdown load but in combination with
earthquake loads and those have been documented and
have -- that seemed to relieve all concern until we get to
the point where we understand that the whole fuel assembly
will now have less ductility and it may have lower fracture
toughness and the kind of things that would come into that
analysis. We do plan to review that but we have to get the
mechanical properties from our measurements before we have a
basis for doing that assessment.
CHAIRMAN JACKSON: Well, I am not at all talking
about what has to come first. I am really specifically
asking you whether or not you are considering the issue of
blowdown loads or planning to revisit it as part of what you
are doing?
MR. KING: Yes, we are planning to do it. We
haven't gotten that far yet.
CHAIRMAN JACKSON: All right.
Commissioner Rogers?
COMMISSIONER ROGERS: I don't have any additional
comments.
CHAIRMAN JACKSON: Commissioner McGaffigan?
COMMISSIONER McGAFFIGAN: No additional questions.
. 77
CHAIRMAN JACKSON: All right.
Thank you.
I would like to thank the staff for a very
informative and long briefing. Long because of us. And I
would urge the staff to continue its cooperation in
international experiments. It seems like that is an
important source of data and information for us, in order to
establish failure limits for high burnup fuel and reactivity
insertion accidents. But operational experience, as we have
been discussing for the last two hours, clearly suggests
that high burnup fuel has effects that go beyond reactivity
insertion and I am going to urge you to do what you have
already told us you are doing, namely to ensure that you
have the appropriate research and other tools in place to
address emerging issues that relate to core and fuel designs
and plant operations.
You know, the agency's licensing criteria which,
you know, you are expecting will hold up to a certain extent
beyond the current burnups is based on 1970s experience and
to burnups that were to less than 30 gigawatt days per ton.
So you say you are and so I am saying that you should
reassess our fuel regulatory guidelines and licensing
criteria covering not only reactivity insertion accidents
but the design basis accidents we have been talking about
and LOCAs.
. 78
But the thing I would particularly encourage the
staff to do is to continue not only gathering data and
information but integrating it on as much of a real time
basis as possible and to confirm that plants are safe and in
compliance with their licensing bases.
The final comment is that I am taking off from
what Mr. Miraglia said, that all of these various lessons
learned that we have done and what the staff, the Commission
has been asked to look at and approve will ensure that we
capture what we need to capture in this area, vis-a-vis fuel
design in the licensing basis.
So if there are no further comments, we are
adjourned.
[Whereupon, at 11:50 a.m., the briefing was
concluded.]
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