ML24178A236
| ML24178A236 | |
| Person / Time | |
|---|---|
| Issue date: | 05/01/2024 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-2828 | |
| Download: ML24178A236 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Open Session Docket Number:
(n/a)
Location:
teleconference Date:
Wednesday, May 1, 2024 Work Order No.:
NRC-2828 Pages 1-68 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com 1
1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 UNITED STATES OF AMERICA 1
NUCLEAR REGULATORY COMMISSION 2
+ + + + +
3 715TH MEETING 4
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5
(ACRS) 6
+ + + + +
7 OPEN SESSION 8
+ + + + +
9 WEDNESDAY 10 MAY 1, 2024 11
+ + + + +
12 The Advisory Committee met via hybrid In-13 Person and Video-Teleconference, at 8:30 a.m. EDT, 14 Walter Kirchner, Chairman, presiding.
15 16 COMMITTEE MEMBERS:
17 WALTER L. KIRCHNER, Chair 18 GREGORY H. HALNON, Vice Chair 19 DAVID A. PETTI, Member-at-Large 20 RONALD BALLINGER, Member 21 VICKI M. BIER, Member 22 VESNA B. DIMITRIJEVIC, Member 23 JOSE MARCH-LEUBA, Member 24 ROBERT P. MARTIN, Member 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
2 THOMAS E. ROBERTS, Member 1
MATTHEW SUNSERI, Member 2
3 DESIGNATED FEDERAL OFFICIAL:
4 KENT HOWARD 5
7 ACRS CONSULTANT:
8 DENNIS BLEY*
9 STEPHEN SCHULTZ*
10 11 ALSO PRESENT:
12 ASHLEY BIRDETT, Vistra*
13 LARRY BURKHART, ACRS 14 JEREMY DEAN, NRR*
15 MATTHEW DOMKE, R-III 16 JOHN ELLEGOOD, R-IV*
17 TODD EVANS, Vistra 18 NATHAN FRENCH, Xcel Energy 19 LAUREN GIBSON, NRR 20 RAMIZ GILADA, Vistra*
21 SHAWN HAFEN, Xcel Energy 22 ZACH HARPER, Westinghouse 23 KEVIN HELLER, NRR 24 AUSTIN IM, NRR 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
MARIELIZ JOHNSON, NRR 2
EVAN JONES, Vistra 3
AMIT KALIA, Vistra 4
JEFF KOBELAK, Westinghouse 5
SCOTT KREPEL, NRR 6
JAMES LAIRD, Westinghouse 7
JOHN LEHNING, NRR 8
JAY LLOYD, Vistra 9
EDWIN LYMAN, Public Participant*
10 SHIATTIN MAKOR, NRR 11 CHUCK NORTON, R-III*
12 BRIAN SMITH, NSIR 13 TAYLOR SMITH, Vistra 14 STEPHEN SOLLOM, Xcel Energy 15 NICHOLAS TAYLOR, NRR 16 DARIUSZ SZWARC, R-III 17 BRANDON WISE, NRR 18 JOHN WISE, NRR 19 ON YEE, NRR 20 MARK YOO, NRR 21 22 23
- present via video-teleconference 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
4 P-R-O-C-E-E-D-I-N-G-S 1
8:29 a.m.
2 CHAIR KIRCHNER: Good morning. The meeting 3
will now come to order, this is the second day of the 4
seven hundred fifteenth meeting of the Advisory 5
Committee on Reactor Safeguards.
6 I'm Walt Kirchner, Chairman of the ACRS.
7 Other members in attendance are Ron Ballinger, Vicki 8
Bier, Vesna Dimitrijevic, Greg Halnon, Jose March-9 Leuba, Robert Martin, David Petti, Tom Roberts, and 10 Matt Sunseri.
11 We also have our consultants, Dennis Bley 12 and Steve Schultz, with us today virtually. I note 13 that we have a quorum.
14 Similar to yesterday, the Committee is 15 meeting in person and virtually. Our communications 16 channel has been opened to allow members of the public 17 to monitor the Committee discussion.
18 Zena Abdullahi is the designated federal 19 officer for today's meeting. It is requested that the 20 speakers identify themselves and speak with sufficient 21 clarity and volume, so that they may be really heard.
22 Additionally, participants should mute 23 themselves when not speaking, including your cell 24 phones.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
5 During today's meeting, the Committee will 1
consider the following topics: The Westinghouse 2
Topical Report on Incremental High Burnup Extension, 3
and Committee deliberations on the research topic, 4
Non-Light Water Reactor Co-Development.
5 So, with that, unless there are comments 6
from members before we proceed, I am going to turn to 7
Ron Ballinger to chair our first session. Ron?
8 MEMBER BALLINGER: Thank you, Chair 9
Kirchner.
10 I think we had a subcommittee meeting in 11 April, not that long ago, and I think most of the 12 members were there. So, we can be brief on this.
13 The proposal is for incremental burnup 14 allowance for Westinghouse and some CE fuel. This, at 15 least in my personal opinion, is the beginning of what 16 amounts of a bit of a bow wave related to FFRD and 17 other kinds of issues. So, there's importance for 18 this proposal here as well.
19 And by the way, we have a non-concurrence, 20 which we'll speak a little bit through the staff.
21 We'll talk a little bit about that as well, and its 22 resolution.
23 So, I think, Scott, you want to make a 24 statement?
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
6 MR. KREPEL: Yes, good morning. This is 1
Scott Krepel, speaking through a sign language 2
interpreter.
3 I am the branch chief for the Nuclear 4
Methods and Fuels Analysis Branch, and my staff are 5
the individuals who reviewed this particular topical 6
report.
7 We have had a good engagement with 8
Westinghouse. And I think overall, it was a 9
successful review, and as well as the findings.
10 Like Dr. Ballinger mentioned, this is a 11 bit of a bow wave for high burnup, as well as FFRD.
12 And so, it's a bit of a stepping stone, if you will, 13 to where Westinghouse is going to be going with their 14 technology.
15 Eventually, we will see more full ambition 16 from the industry by the end of this decade. So, with 17 that being said, I look forward to hearing all the 18 presentations today, as well as the staff. I will be 19 presenting myself as part of the non-concurrence.
20 Thank you.
21 MEMBER BALLINGER: Thank you. The 22 Westinghouse folks want to make an introductory 23 statement?
24 MR. HARPER: Yes, good morning. My name 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
7 is Zach Harper at Westinghouse.
1 Just want to thank the ACRS for reviewing 2
the topical report and we look forward to a good 3
discussion. Also, thank the NRC for their review.
4 And with that, I think --
5 MEMBER BALLINGER: Yeah, I might add by 6
the way, that we will have an open and closed session.
7 So, the first presentations will be in the open 8
session, then we'll give people a bit of a time to 9
switch over and verify things, then we'll go into the 10 closed session. So, Zach, the floor is yours. Or 11 whoever is presenting, the floor is yours.
12 MR. KOBELAK: All right, thank you very 13 much. So, my name is Jeff Kobelak and I work in the 14 safety analysis area at Westinghouse.
15 And I think the opening comments were 16 really spot-on to where I'm going to begin this 17 presentation.
18 So, Westinghouse is pursuing burnup 19 extension as a two-step process. I think that's 20 unique compared to the approach that some of the other 21 fuel vendors are taking.
22 As Scott said, the incremental burnup for 23 us really is kind of a stepping stone as we go to high 24 burnup.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
8 So, the concept for incremental burnup was 1
that we would limit the core interior to the current 2
burnup limit of 62 gigawatt days per MTU, but we would 3
allow rods that are in peripheral assemblies to go to 4
a higher burnup level.
5 And that would set us up for step two of 6
our burnup increase, where we would allow the entire 7
core to go to some burnup value above 70 gigawatt days 8
per MTU, maybe 75-ish gigawatt days per MTU.
9 And for that second step, that would 10 require an enrichment increase that is not required 11 for the incremental burnup extension.
12 So, I kind of wanted to start this to 13 speaking to where incremental burnup falls within 14 Westinghouse's approach to high-energy fuel and 15 accident-tolerant fuel. And when I say high-energy 16 fuel, I'm referring to high burnup and higher 17 enrichment. So, I do think that the term bow wave was 18 used.
19 As you can see from this diagram, 20 incremental burnup is kind of on the leading edge of 21 a number of submittals that we expect to make to the 22 NRC supporting these programs.
23 So, if we look from left to right, left is 24 already approved. So, that's the things that were 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
9 started early. And then we moved to things that are 1
under review, which is kind of where we're at today, 2
and then looking forward a
little bit to 3
underdevelopment and long-term concepts.
4 So, the ADOPT fuel pellets, which is the 5
Westinghouse scope fuel product, that is something 6
that has already been submitted to and approved by the 7
staff. And same thing with our AXIOM cladding.
8 So, those are topical reports that have 9
gone through approval process. And I think both of 10 those were presented previously to the ACRS.
11 What we're talking about today is our 12 incremental burnup program. And also under review is 13 our higher enrichment topical report. So, there was 14 actually an audit several weeks ago, and we know that 15 review is progressing on that topical report.
16 The next one is the EPRI alternate 17 licensing strategy, which I think has also been 18 presented to the ACRS and there's more presentations 19 expected on this later on in June. And that one has 20 actually just slipped from underdevelopment to under 21 review.
22 So, Westinghouse made a submittal to the 23 staff with a methodology to perform cladding rupture 24 calculations that supports EPRI ALS, and really kind 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
10 of builds off a lot of the work we've done for 1
incremental burnup.
2 That was submitted for review back in 3
February. And just yesterday, I was informed by EPRI 4
that the submitted the remaining three topicals that 5
support EPRI --
6 MEMBER BALLINGER: -- this morning.
7 MR. KOBELAK: Oh, it that right? Okay, 8
so, yeah, I believe that has just ticked under review 9
right now.
10 And then looking
- forward, so, 11 underdevelopment, we're still working on our chromium-12 coated cladding product. That's something that I 13 think we expect to submit later this year or early 14 next year, and that will lead us to our full core high 15 burnup extension.
16 And that's expected to be a number of 17 submittals. So, we'll likely have a submittal for our 18 fuel performance-coded method to support high burnup, 19 then our LOCA-coated method will be submitted 20 separately.
21 And finally, we will have a high burnup 22 topical report, which will cover all the different 23 elements of high burnup which aren't captured in those 24 prior two submittals.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
11 And I think that's probably the vast 1
majority of what we'll be submitting in the more near-2 term for high energy fuel and ATF.
3 We are working on uranium nitride and 4
silicon carbide as longer-term concepts. But I don't 5
think right now that we're viewing those as things 6
that are needed to support high burnup and higher 7
enrichment.
8 Okay, so, I have a slide on the 9
incremental burnup extension benefits, and then I'll 10 elaborate a little bit more on this in the closed 11 session.
12 But the primary benefit we see to this is 13 improved fuel utilization. So, if we're able to 14 enable higher discharged burnup for some of these 15 peripheral assemblies, it will allow utilities to load 16 assemblies on the core periphery, that otherwise, they 17 would be precluded from loading, because they would 18 exceed the current burnup limit by the end of cycle.
19 So, with this, utilities could reduce the 20 number of fuel assemblies they have to load, thereby 21 improving the fuel utilization.
22 And of
- course, there's also a
23 corresponding backend cost. So, if you're loading 24 less fuel assemblies, there's less waste that has to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
12 be disposed of at the end of operation.
1 So, a little bit better utilization of 2
spent fuel capacity, less storage in the spent fuel 3
pool, and eventually in dry cask and permanent 4
storage.
5 And at this stage, we actually have 6
contracted with customers to implement these first 7
kind of products I talked about. So, the ADOPT fuel 8
pellets, the AXIOM cladding, and the incremental 9
burnup extension once it's approved.
10 This is a slide that shows the box that we 11 drew around incremental burnup. So, basically, the 12 applicability of this methodology, it does allow fuel 13 rod average burnup greater than 62 on the core 14 periphery.
15 It's limited to the current fuel rod 16 enrichment, so we're still limited to five weight 17 percent enrichment. It will only be for rods in core 18 peripheral assemblies. It does apply to all of the 19 Westinghouse and C fuel designs, as was mentioned 20 earlier, and it applies to pretty much all of our 21 current cladding and fuel pellet materials.
22 So, that would be ZIRLO
- cladding, 23 optimized ZIRLO cladding, and AXIOM cladding, and then 24 standard U02 and ADOPT fuel. And in the future, we 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
13 would intend to also be able to apply this with 1
chromium-coated cladding, once that becomes a product.
2 And the graphic here just speaks to the 3
many different functional areas that were tied into 4
this topical report. So, whereas a lot of times we'll 5
submit a topical report that's focused to one area, 6
like full-spectrum LOCA, which we presented many times 7
in the past, this is more of an umbrella topical 8
report. It covers many different areas.
9 CHAIR KIRCHNER: Jeff, can I interrupt you 10 here?
11 MR. KOBELAK: Yes, please.
12 CHAIR KIRCHNER: How much fuel is out 13 there with ZIRLO cladding, versus optimized ZIRLO, 14 versus AXIOM? Is the bulk of what you're considering 15 for peripheral assembly locations, AXIOM clad?
16 MR. KOBELAK: I'm going to give you some 17 estimates. I don't know the exact numbers. But I 18 would estimate that probably over 90 percent is 19 optimized ZIRLO cladding today.
20 There are very few utilities that are 21 still loading ZIRLO cladding, and the ones that are, 22 I think are looking to move the optimized ZIRLO or 23 AXIOM cladding in the near future.
24 AXIOM is a newer cladding product. We 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
14 just licensed it fairly recently. So, we haven't 1
really had the time yet to propagate that product so 2
much. But there are a number of utilities that are 3
actively transitioning from off ZIRLO to AXIOM. So, 4
over the next several years, I would expect that AXIOM 5
percentage to go up and the optimized ZIRLO percentage 6
to go down.
7 CHAIR KIRCHNER: Okay, when you show data 8
later -- I guess this will be in the closed session --
9 can you just try and distinguish the data versus 10 cladding materials?
11 MR. KOBELAK: Yeah, I think there's kind 12 of one plot that we'll show, that is a really good 13 illustration of the differences between optimized 14 ZIRLO, ZIRLO, and AXIOM, in terms of normal operation.
15 In terms of like the LOCA response and the 16 method that we have, there's very limited differences 17 between those cladding materials. They all tend to 18 perform quite similarly. But I can certainly 19 differentiate as applicable.
20 CHAIR KIRCHNER: Thank you.
21 MEMBER BALLINGER: I had a bit of a 22 thought. Should this increased burnup be approved, 23 are there currently plants operating that have fuel 24 that would then alter their fuel management scheme on 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
15 the fly, so to speak?
1 Put bundles in periphery areas where they 2
wouldn't have earlier.
3 MR. KOBELAK: So, I think there's probably 4
plants that have assemblies that are being stored in 5
the spent fuel pool, that could not be reinserted that 6
this would potentially allow for reinsertion, so long 7
as, of course, all of the safety analysis limits are 8
met for the assemblies that they're looking to 9
reinsert, so there's more than just what's required 10 under incremental burnup. All the other analysis 11 limits also have to be met.
12 MEMBER BALLINGER: Thank you.
13 MR. KOBELAK: Okay, so, next I wanted to 14 just provide a brief overview of what this topical 15 report looks like.
16 So, we did write this topical report, I 17 would say, for clarity, and to ensure that if 18 approved, we could efficiently implement this topical 19 report.
20 So, to that end, a number of the things 21 that we did, we very clearly spelled out which 22 limitations associated with previously approved 23 topical reports were being superseded. Those are all 24 explicitly identified in Section 1.4 of this topical.
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16 And then at the end of the topical report, 1
we wrote a number of limitations for applicability in 2
Section 7.1, which I think -- and the staff can 3
elaborate on this -- I think that formed a starting 4
point for many of the limitations that they wrote, and 5
then, of course, they had some additional ones that 6
they added to that and made some modifications to the 7
ones we wrote.
8 But the idea there is upon approval, both 9
Westinghouse and the staff very clearly understand 10 what's expected for implementation of this topical 11 report.
12 And we also included a number of licensee 13
- actions, the primary options required for 14 implementation in Section 7.2 of our topical report.
15 So, within the middle sections two through 16 six, what we did was really go through and assess the 17 impacts of incremental burnup on the various codes and 18 methods for all of the different functional areas that 19 are impacted by this burnup extension.
20 So, Section 2 covers the mechanical design 21 that's all the fuel assembly design bases, the 22 components and the materials. Section 3 is one of the 23 bigger sections that covers all core and fuel rod 24 performance.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
17 So, for fuel rod design, the primary 1
activity there was justifying that Tag 5 is applicable 2
within this incremental burnup regime.
3 For the nuclear design area, which we'll 4
talk about more in the closed session, the codes were 5
actually already approved through the burnup range 6
that we needed. So, there, it's really just 7
application of those things to incremental burnup.
8 And in the thermal hydraulic design, what 9
we found is that the DMB methods and the determination 10 of DMBR remain applicable within incremental burnup.
11 And we also looked at, relative to rod 12 bow, we credit a reduction in power within increasing 13 burnup to ensure that the higher burnup rods remain 14 non-limiting. And that's what we found for 15 incremental burnup, primarily owing to the fact that 16 these rods are limited to the core, which operates at 17 relatively low power.
18 Section 4 is the loss of coolant accident 19 analysis. So, this is an area where we did actually 20 have to update our codes to add new phenomena to 21 analyze higher burnup fuel rods -- and we'll talk a 22 little bit more about that in the closed session --
23 and we also had some updates that we made to our 24 method for analyzing those higher burnup fuel rods.
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18 And the key here was to address the 1
potential for fuel dispersal for rods in the 2
incremental burnup regime. So, we've committed to 3
demonstrating that the rods in the periphery do not 4
rupture during the LOCA, thereby ensuring that they do 5
not contribute to any potential fuel dispersal.
6 Transient and containment analysis, this 7
was primarily assessing and updating the decay heat 8
models, to ensure that they remain bounding or 9
conservative for the higher burnup fuel rods, and also 10 addressing phenomena for high burnup fuel rods related 11 to rod ejections, so all the considerations in Reg.
12 Guide 1.236.
13 And then the radiological consequence 14 analysis assessing all the various accidents and 15 transience to ensure that we have an appropriate 16 method accounting for the higher burnup fuel rods.
17 So, I think the big piece that really was 18 the reason why we went with this incremental burnup 19 approach is FFRD.
20 At the time we submitted incremental 21 burnup, we did not have all of the tools available to 22 us that we needed to fully resolve that FFRD for all 23 of the assemblies in the core.
24 But we did realize that for the lower 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
19 power assemblies, we had a pretty strong case that 1
they would not contribute to fuel dispersal. So, that 2
was really what predicated the approach for 3
incremental burnup.
4 We did not go further with this first step 5
because we did not feel like we could adequately 6
resolve FFRD at that time. That's what we're working 7
to in step two of our burnup extension.
8 MEMBER MARCH-LEUBA: Even if FFRD gets 9
resolved on that probabilistic basis where the 10 analysis or probability, whatever, how would it get 11 resolved? This approach of putting the high burnup 12 fuel where it doesn't matter if you have an accident, 13 should be maintained. It really is -- it's a good 14 approach.
15 We can make an argument FRD, believe me, 16 it's not going to happen. It's important high burnup 17 fuel is very, very --
18 MR. KOBELAK: Yeah, I agree. And I don't 19 think that our new topical reports will supersede 20 this. I think they will be an alternative to this, or 21 used in conjunction.
22 MEMBER MARCH-LEUBA: And you should use it 23 in conjunction to encourage that type of core design.
24 MR. KOBELAK: Okay, so this is the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
20 schedule of where we've kind of come through the 1
incremental burnup topical report review. We 2
submitted it back in December 2020 to the staff, and 3
the staff completed their acceptance review in March 4
of 2021. We received our first round of REIs in 5
December of 2021, and responded to that in several 6
sets, which was completed in June of 2022.
7 There was a number of open questions that 8
the staff still had after our first round of 9
responses. So, there was a second round of REIs 10 issued September of 2022, and we responded to those in 11 February of 2023. That led to a draft SER, which the 12 staff sent out back in March of this year.
13 As Dr. Ballinger mentioned in the opening 14 remarks, we presented to the ACRS subcommittee I think 15 for materials back in April, and that had led us to 16 today and our presentations today, and assuming that 17 this proceeds forward, we would expect the final SER 18 in June of this year.
19 So, that was everything I had in the open 20 session. Any other questions for me?
21 MEMBER BALLINGER: Thank you.
22 MR. KOBELAK: Thank you.
23 MEMBER BALLINGER: Westinghouse folks 24 ready to go? Excuse me.
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21 PARTICIPANT: Staff.
1 MEMBER BALLINGER: Staff. They went.
2 They went.
3 (Simultaneous speaking.)
4 MEMBER BALLINGER: Okay, before you get 5
started, John is actually doing double duty, I think.
6 He's not only presenting the staff presentation, but 7
also discussing the non-concurrence.
8 So, for members of the public, they're 9
waiting for that. That discussion will be here, not 10 in the closed session. Okay, thanks.
11 MR. HELLER: All right, hi. I'm Kevin 12 Heller, I'm with the Nuclear Methods and Fuel Analysis 13 Branch and with my colleagues here, Brandon Wise and 14 John Lehning.
15 We're thankful for you guys taking time 16 out of your busy schedules to hear what it is that we 17 have to present.
18 So, I know we're short on time a bit, so 19 why don't we just jump right into this. Next slide, 20 please.
21 Just a presentation outline here, kind of 22 breaking down how the various topics we're going 23 through. Next slide.
24 So, I think a good place to start be to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
22 provide some background regarding the incremental 1
burnup methodology, to kind of serve as a starting 2
point for our discussion today.
3 So, from the staff's perspective, this 4
topical report is effectively an umbrella topical 5
report serving to do two things, the first of which is 6
to justify extending the approved range of 7
applicability of a large host of Westinghouse codes 8
and methods.
9 And then the second thing is to define a 10 methodology by which those codes and methods can be 11 applied to analyze core designs with incremental 12 burnups.
13 And one of the key points of this 14 methodology is that it intends to demonstrate no 15 dispersal for fuel that is within that incremental 16 burnup range. Next slide, please.
17 So, here's a timeline of the review. I'm 18 going to go over this quickly, just hit the high 19 points.
20 So, the topical report was submitted in 21 December of 2020. The acceptance review was completed 22 in March of 2021.
23 In May of '21, Westinghouse provided a 24 voluntary supplement with additional information. The 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
23 staff issued one primary round of REIs, and there was 1
a second smaller follow-up set that more or less 2
focused on clarification and expansion of some of the 3
responses from the first one.
4 In May of 2023, Westinghouse provided a 5
voluntary supplement, to include the AXIOM cladding 6
within the scope of this topical. And after the 7
completion of the initial draft SE, the non-concurring 8
staff generated a non-concurrence and filed it in 9
December of 2023.
10 So, as was mentioned earlier, there is a 11 non-concurrence associated with this review, and this 12 topic will be covered in a separate presentation 13 shortly, later today. Next slide, please.
14 So, this is a list of the key regulatory 15 requirements and guidance documents the staff used 16 during the course of the review.
17 I'm really not going to go into this for 18 too much time since we've all seen it before, but I do 19 want to just point out a couple of the key ones for 20 each one of the various areas.
21 So, for the fuel performance, or the fuel 22 and core performance, of course, NUREG-0800, the 23 standard review plan. Next slide.
24 Loss of coolant accident with its 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
24 requirements in 10 CFR 50.46, and Reg. Guide 1.203.
1 Next slide.
2 Or not loss-of-coolant accidents. Again, 3
NUREG-0800, and Reg. Guide 1.236. Next slide.
4 For containment analysis portion, the GDC 5
- 50. Next slide, please?
6 And, okay, so with that, I'll turn it over 7
to Brandon to talk about the fuel assembly mechanical 8
design.
9 MR. WISE: Thank you, Kevin. The 10 Westinghouse fuel assembly mechanical design 11 evaluation is broken down into three parts, those 12 being a set of design criteria to evaluate fuel up to 13 the incremental burnup extension, a method of 14 evaluating against that criteria, and the results for 15 a specific design.
16 The NRC staff determined that the proposed 17 design criteria and evaluation methods are acceptable 18 and do not result in a significant increase in fuel 19 assembly damage or defamation in the incremental 20 burnup range.
21 The design-specific evaluation was for the 22 17 x 17 OFA design, and the staff determined that the 23 design met all the approved design criteria.
24 Therefore, the 17 x 17 OFA design was approved on a 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
25 generic basis for the incremental burnup extension.
1 Other assembly designs will need to be 2
approved in a separate submittal for LNC-1. Next 3
slide, please, where Kevin will discuss the core and 4
fuel rod performance.
5 MR. HELLER: Thanks, Brandon. So, with 6
the core and fuel rod performance portion of the 7
topical, presented therein were discussions across 8
three separate phenomenological areas of Westinghouse 9
codes and methods, to justify extending the rod 10 average burnup limit. And you can see the three areas 11 here.
12 During the review, the NRC staff assessed 13 each of these areas in turn, but the first of these, 14 the fuel rod performance, I'll only touch on briefly 15 here in the open session. I'll go into more detail on 16 that in the closed. Next slide, please.
17 So, to briefly touch on this fuel rod 18 performance, the fuel rod performance phenomenological 19 models are within the PAD-5 fuel performance code.
20 Westinghouse provided justifications for 21 the applicability of those models associated with each 22 one of the fuel rod design bases at the incremental 23 burnups, and the NRC staff assessed the models and 24 found them to be acceptable.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
26 However, the staff concluded that some of 1
the models are applicable to the incremental burnup 2
range only within the incremental burnup methodology 3
itself. And we'll talk a little bit more about that 4
in the close. Next slide, please.
5 So, for the nuclear design, Westinghouse 6
proposed to continue using their existing nuclear 7
design codes, and Westinghouse indicated that these 8
codes are applicable to the increased burnup 9
conditions within the existing five percent enrichment 10 limit.
11 The NRC staff examined the overall 12 performance of these codes, but also assessed two 13 areas that will proceed to be most likely stressed by 14 application, to the extent of burnup range, and that 15 would be the production and depletion of major uranium 16 and plutonium isotopes, as well as modeling of the 17 increased critical boron concentrations.
18 Through these particular assessments, the 19 NRC staff found that Westinghouse's nuclear design 20 codes are applicable to core nuclear designs within 21 the scope of the methodology that was submitted. Next 22 slide, please.
23 For the thermal hydraulic
- design, 24 Westinghouse proposed that no modifications are 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
27 necessary to their existing methods for analyzing the 1
departure from nuclear boiling. You can see a couple 2
of the particular methods here.
3 The NRC staff assessed Westinghouse's 4
justifications and concluded that Westinghouse's 5
thermal hydraulic codes and methods are applicable up 6
to the requested rod average burnup extension limit.
7 And John?
8 MR. LEHNING: Thank you, Kevin. So, this 9
is John Lehning from the staff. And most of the 10 information, we'll go into more detail on the loss-of-11 coolant accident in the closed session. But just as 12 a high-level summary here in the open session, the 13 objective of the methodology is to demonstrate no 14 cladding rupture for fuel that is within the 15 incremental burnup range, and by preventing cladding 16 rupture, clearly we don't have fuel dispersal going 17 on.
18 The method that Westinghouse has proposed 19 to use is based on the full spectrum LOCA methodology 20 and the W-COBRA track TF2 code.
21 Westinghouse looked at whether impacts of 22 increased burnup would affect any of the methods that 23 they used, and evaluated several different parts in 24 doing that.
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28 In cases where model updates were needed 1
-- and we have some examples on the slide -- they 2
updated those models; or if they were not needed, the 3
provided justification for that.
4 And in general, the staff found this 5
acceptable. We'll go into more details again in the 6
closed session.
7 So, I'm going to turn it back over to 8
Kevin to go over non-LOCA.
9 MR. HELLER: Thanks, John. So, for the 10 non-LOCA accident analysis methods, when it comes to 11
- these, Westinghouse separates these into two 12 categories of events, those events that are dependent 13 upon core average effects, and then those that are 14 analyzed to assess the local fuel rod behavior.
15 For events depended upon the core average 16 effects, Westinghouse indicated that the existing 17 codes and methods can readily accommodate any impacts 18 that the incremental burnup may have.
19 So, the NRC staff went and assessed 20 potential impacts to relevant parameters in these 21 methods, and concluded that this assertion was 22 reasonable.
23 For the second category of events, 24 Westinghouse did not propose any changes to acceptance 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
29 criteria for these events, or any changes to the 1
parameters. And the NRC staff concluded that the 2
codes used to analyze the events have been 3
individually approved for use in the incremental 4
burnup range, either generically prior to this review, 5
or within the scope of this topical itself. So, for 6
example, the PAD-5 methodology. Next slide, please.
7 For the reactivity insertion accidents, 8
Westinghouse discussed its conformance with the fuel 9
cladding failure criteria thresholds in Reg. Guide 10 1.236. You can see, in particular, the four that are 11 listed here on the slide.
12 The NRC staff went and assessed the 13 discussions of conformance with the cladding failure 14 thresholds, and examined the code applicabilities, and 15 the NRC staff determined that Westinghouse's 16 evaluation of control rod ejection analyses is 17 acceptable because of those discussions, and because 18 the codes used to analyze the control rod ejection 19 have been shown to maintain adequate predictive 20 capability within the incremental burnup range. Next 21 slide, please.
22 With regard to the containment integrity, 23 Westinghouse provided discussion for the containment 24 integrity analyses for both LOCA and the main steam 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
30 line break scenarios.
1 Because Westinghouse's justifications and 2
the staff's conclusions are largely the same for both 3
of these, I'm just going to be speaking about both of 4
them side-by-side.
5 So, for the short-term mass and energy 6
release, these are really dominated by system 7
conditions, not fuel conditions.
8 And so, the NRC staff's conclusion was 9
that changes in core design to allow for changes in 10 cycle length at incremental burnups would not impact 11 these analyses.
12 For the long-term releases, the NRC staff 13 concluded that the computer codes and methods approved 14 to perform these analyses, were made applicable 15 because of the conservative decay heat modeling, and 16 because any impact from an incremental burnup increase 17 could be readily accommodated by these codes. Next 18 slide, please.
19 MR. LEHNING: And the next slide is John 20 Lehning speaking again on radiological consequence 21 analysis. We have a few slides here in the open 22 session. We'll cover it a little more in detail in a 23 few points in the closed session.
24 So, Westinghouse addressed three different 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
31 types of accidents for the radiological consequences:
1 the loss-of-coolant
- accident, certain non-LOCA 2
accidents, as well as a fuel-handling accident.
3 And on the next slide, I'll cover, just in 4
brief, the LOCA and non-LOCA accidents, for both of 5
which Westinghouse concluded that applicable guidance, 6
its codes and methods used to conform there too, 7
remain applicable.
8 For fuel in the incremental burnup range, 9
that depends a little bit on some of the information 10 we'll give you in the closed session. But just at the 11 high level right now, the partial explanation of that 12 is that the LOCA, the radiological consequence 13 analysis, that's typically done with one of two 14 regulatory
- guides, depending on whether the 15 alternative source term is used, or the traditional 16 TID source term.
17 And then, the third bullet here explains 18 that for non-LOCA accidents where the release of 19 coolant that has a slight amount of radioactive 20 contamination, where that comes in as part of the 21 dose, those technical specification limits control 22 that.
23 And so, this topical report wouldn't 24 change those limits. And so, that helps understand 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
32 why this conclusion was reached. But again, we'll 1
cover a little bit more information about this in the 2
closed session.
3 For the fuel-handling accident, this is an 4
event that's a little bit different, and we'll go into 5
some more detail again on this one in the closed 6
session.
7 But the impacts of fuel dispersal for non-8 LOCA accidents, that's not generically addressed in 9
existing regulatory guidance. And so, Westinghouse 10 had to consider impacts of certain key factors here, 11 which we'll cover more later.
12 But the bottom line conclusion here is 13 that licensees would be justifying the way that 14 they've addressed fuel handling accidents in their 15 license amendment request, where they're proposing to 16 implement this topical report and the staff would be 17 able to review those at that time.
18 And so, the next slide, Brandon will give 19 about applicability to adopt in AXIOM.
20 MR. WISE: Hey, John. The scope of the 21 incremental burn extension includes both adopt field 22 clads and AXIOM cladding. Both of these topical 23 reports were previously approved up to current burnup 24 limits.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
33 The staff determined that the methodology 1
for the incremental burnup extension is applicable to 2
these two technologies, and that the design-specific 3
models are acceptable up to the requested burnup 4
limit.
5 Furthermore, the AXIOM cladding and ADOPT 6
fuel pellets are subject to the same restrictions as 7
standard U2 and other cladding designs. Next slide, 8
please, where John will discuss the material 9
applicability conditions.
10 MR. LEHNING: Okay, and this slide 22, 11 these limitations and conditions, these were ones that 12 actually were self-proposed by Westinghouse. And 13 basically, they just limit the scope of applicability 14 to a reasonable scope that gives them the ability to 15 use the fuel designs that they wish with topical 16 report and prevent us from trying to review it for 17 other purposes, where it's not a useful part of the 18 review.
19 And so, should, in the future, there be a 20 desire to extend it, that review could take place in 21 the future. But this is the set, at least for the 22 near-term, that Westinghouse was looking for.
23 So, Kevin will give the next slide on 24 limitations and conditions.
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34 MR. HELLER: All right, thanks. So, the 1
NRC staff's draft safety evaluation contains fourteen 2
limitations and conditions that licensees adopting the 3
methodology must address.
4 Incorporated within those fourteen are 5
nine limitations that Westinghouse proposed within the 6
submittal, and in the REI responses, and there's a 7
smaller subset of those several -- probably three, 8
maybe four -- that the NRC staff modified during the 9
course of the review.
10 So, although we have not explicitly spoken 11 to all the limitations and conditions in our verbal 12 presentation here today, eight of them have been noted 13 on the previous slides that we've gone through, and 14 the remaining six will be noted within the closed 15 presentation.
16 So, then in conclusion, the staff found 17 that the WCAP-18446 incremental burnup methodology 18 provides an acceptable approach for the comprehensive 19 evaluation of fuel operating within the requested 20 extended burnup limit. And it was addressing the fuel 21 assembly mechanical design, core and fuel rod 22 performance, non-LOCA and LOCA safety analyses, and 23 radiological consequences.
24 So, of course, the staff's conclusions are 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
35 predicated upon the methodology being used within the 1
approved range of its applicability, and the licensees 2
acceptably addressing the limitations and conditions.
3 That's what we have for you.
4 MEMBER MARCH-LEUBA: For the transcript, 5
if somebody doesn't go and read the full Committee 6
transcript, at the end of the subcommittee, I mention 7
that almost fourteen limitations and conditions sound 8
terrible. So, if you found fourteen bad things with 9
the methodology, and indeed when you review them one-10 by-one, they're more like documenting the range of 11 applicability of methodology.
12 It's not problems with the methodology, 13 but just being precise. So just for the record, you 14 want to see more, go to the subcommittee.
15 MEMBER BALLINGER: I would term most of 16 them administrative.
17 MR. HELLER: I think we would agree with 18 you on that.
19 MEMBER BALLINGER: Other questions from 20 the Committee or consultants?
21 This then will be the end of the open 22 session. I think we need to go off for the public.
23 MEMBER MARCH-LEUBA: Are we going to have 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
36 MEMBER BALLINGER: Oh, I'm sorry.
1 (Simultaneous speaking.)
2 MEMBER BALLINGER: I looked at who's 3
presenting, I saw conclusions, I said, well, this is 4
the end of this. Okay, go ahead. I'm sorry.
5 MR. LEHNING: Okay. So, no more questions 6
on this. I'm going to stop sharing this, and then 7
move to the other presentation on the non-concurrence.
8 Okay, so, good morning. So, I think we're 9
ready to talk about the non-concurrence that two 10 individual staff -- myself, John Lehning, and Kevin 11 Heller -- had on the staff's safety evaluation for 12 WCAP-18446, and we thank you for the opportunity to 13 present this.
14 We went in more detail at the 15 subcommittee. We'll go a bit briefer here in the full 16 Committee.
17 The first slide summarizes the non-18 concurrence. The original safety evaluation that was 19 drafted by the technical staff during the detailed 20 review, included a limitation and condition that would 21 have required licensees implementing WCAP-18446 to 22 assess the potential for fuel dispersal from fuel rods 23 within the current burnup limit, and justify that the 24 estimated quantity of fuel that would disperse would 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
37 not result in non-compliance with the 50.46 acceptance 1
criteria.
2 Agency management removed that proposed 3
limitation and condition, and they will speak to the 4
rationale for that decision.
5 But absent that limitation condition that 6
the staff who did the review thought was necessary to 7
find the methodology acceptable, the non-concurring 8
staff could not find sufficient basis to conclude that 9
plants implementing the method would comply with 10 existing regulatory requirements.
11 And then given that the Commission's 12 regulations set the bar for adequate protection of 13 public health and safety, it at least opens up the 14 question of that conclusion as well.
15 So, we'll go over just three of the key 16 contentions here in this non-concurrence. The one is, 17 first, is whether fuel dispersal is a safety question 18 or not.
19 The modified safety evaluation has a 20 pretty strong conclusion that fuel dispersal is not a 21 significant safety issue within existing burnup 22 limits.
23 But it doesn't go into a lot of 24 experimental and analytical basis for why that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
38 conclusion is justified, whereas the technical staff 1
who did the review, when we look at some recent 2
experimental evidence and analytical calculations that 3
we stepped through with the subcommittee, that could 4
be the Research Information Letter 2021-13, that has 5
this threshold for fragmentation dispersal being well 6
within the existing burnup license limits.
7 And then also, some of the analyses 8
completed by the staff that shows that we could have 9
hundreds, maybe even into the thousands of pounds of 10 dispersed fuel, at least opens up a question that 11 there could be something substantive here that should 12 be resolved.
13 On this slide 4, this question I think 14 sharpens a little bit too when we think about that 15 existing evaluation models for the loss-of-coolant 16 accident and existing analyses for that event don't 17 address fuel dispersal and its impacts.
18 If we read some words that are in the 19 modified safety evaluation -- licensees may use 20 current approved methodologies to evaluate the fuel 21 assemblies within the current burnup limits -- we 22 might think that this is sort of reasonable. It 23 sounds reasonable.
24 But if we realize that, again, that these 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
39 methods don't include the effects of dispersal, then 1
I think it becomes clear that these types of 2
calculations wouldn't really give us any additional 3
confidence that there's compliance with respect to a 4
coolable geometry, or other relevant limits, from 5
doing this analysis that neglects that phenomenon.
6 And then to the most key contention of all 7
in the non-concurrence, the staff who did the review 8
and non-concurred, concluded that absent further 9
effort -- and this could be experiments to better 10 define the phenomenon associated with fuel dispersal, 11 or analyses to quantify how much occurs and where that 12 dispersed fuel goes and what its impacts are -- we 13 could not conclude with a high level of probability --
14 and those words come directly in 50.46 in paragraph A 15 that the relevant regulatory requirements, 16 including maintaining a coolable core geometry, would 17 be satisfied.
18 And so, where the non-concurring came out, 19 was that we should assess and resolve this well-20 founded safety question regarding fuel dispersal, 21 before licensing higher limits for burnup that could 22 result in exacerbating this question that is out there 23 on fuel dispersal.
24 So, to be clear, the non-concurring staff 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
40 are not saying that plants are definitively out of 1
compliance, nor are we saying that corrective actions 2
necessarily need to be taken, but rather than existing 3
NRC processes, which I'll touch on in a few slides, 4
that these processes be used to address the safety 5
question and come to a reasoned outcome.
6 And so, this slide 6, it just explains 7
really quickly, what are the factors that have 8
hindered, or made it difficult to come up with a clear 9
regulatory determination on fuel dispersal.
10 And one of the two, the first of the two, 11 is that they're large on certainties. I mentioned 12 that dispersal could be tens, or hundreds, maybe 13 thousands of pounds of fuel.
14 And then where does it go? Those are 15 still, those are being resolved. We're working on 16 those things, but we don't have a firm grasp on them 17 at the current time, to really precisely define those 18 things.
19 And then the second point is that even if 20 we could, we wouldn't know exactly, as we do like for 21 pre-cladding temperature, we know 2200; if it's 2199, 22 that's acceptable; if it's
- 2201, that's not 23 acceptable.
24 But we don't have a clear threshold at 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
41 which we could say and make efficient regulatory 1
decisions for dispersal, because we don't know exactly 2
where to set the bar at this time. We need to do more 3
work to be able to do that, in the non-concurring 4
staff's opinion.
5 And we touched a little bit on what is the 6
intent of existing regulations. And this is important 7
to the non-concurring staff because we feel it's our 8
duty to ensure that the regulations are satisfied.
9 It's not within our purview or authority 10 to come to a decision that, okay, we think this is 11 acceptable, but for a different reason than complying 12 with the regulations.
13 That's up to the Commission to set the 14 regulation and the staff regulates that.
15 And so, when we talked about what are the 16 existing criteria in 50.46, paragraph (e), what are 17 they trying to ensure?
18 Even on the hottest rod, this rad rod here 19 on the hottest -- know that a hottest rod, the idea is 20 that when reflooding of the core occurs, we should not 21 shatter that cladding, and then disperse pellets.
22 And so, if that logic holds for the 23 hottest rod, it holds for the rest of the core, and 24 then in this idealization, we have a picture that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
42 looks like all the fuel is within the core, it's 1
within this geometry as coolable.
2 So, that's what the criteria ensure right 3
now, the numerical criteria, like the cladding 4
temperature.
5 The Commission also, in issuing 50.46 way 6
back in 1973, it made the statement of, what do we 7
want to avoid? And it was this situation where the 8
core geometry's lost, there's a pile of pellets that 9
were later fused into an uncoolable mass. This is 10 clearly severe accident and complete core damage.
11 And so, where does fuel dispersal, if we 12 talk about substantial mass of fuel dispersal, where 13 does that fall?
14 Obviously, it's neither one of these more 15 boundary cases. So, we can see the geometry of the 16 core remains there, but there also is potentially this 17 pile of fragments in the bottom of the vessel, and 18 maybe some of it escapes out into the containment, it 19 needs to be quantified.
20 But I would call this somewhat as maybe a 21 partial core damage. It's certainly something 22 different than what the regulation is trying to --
23 currently, the way it's been understood.
24 And so, the staff doesn't have clear 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
43 guidance on how to handle this case, at least at the 1
present time. And so, that's a part of why we're here 2
in the non-concurrence on this particular view.
3 So, slide 8, it sort of gives the non-4 concurrence staff's perspective on why do we need to 5
maintain defense in-depth margin? Why do we need to 6
continue to resolve these issues and get them 7
addressed?
8 And we strive for reasonable assurance of 9
safety, not absolute, 100 percent assurance of safety.
10 Even though we make our best decisions, 11 there's always the potential for things to arise that 12 we didn't quite understand at the time.
13 And so, the last time we increased burnup 14 limits, I would say didn't realize fuel dispersal or 15 thermal conductivity degradation, and we know that 16 these issues, resolving them takes time. We're still 17 very much in the throes of fuel dispersal, thermal 18 conductivity degradation.
19 We've technically, pretty much I think, 20 resolve it, but in the regulatory process it's still 21 working its way through. There's still a limitation 22 and condition on that in this topical report.
23 And so, clearly, we need to continue to 24 make progress in resolving these issues, so that when 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
44 we do make future decisions and there are further 1
increases in burnup -- as we were talking about the 2
bow wave and stepping stones -- that we have the 3
margin there for reasonable assurance, but not 4
absolute assurance.
5 In slide 9, it explains how can the NRC 6
address emergent safety questions.
7 There are two primary ways that that could 8
be done. One would be voluntary, forward-looking 9
licensing basis changes.
10 For example, like the limitation and 11 condition the staff proposed in this topical report 12 safety evaluation. That would have been a way of 13 getting the licensees implementing that to resolve the 14 issue.
15 There's also the possibility that under 16 50.109, that there could be a mandatory generic 17 backfit. And the non-concurring staff would feel 18 comfortable with either one of those approaches.
19 But management didn't feel that they were 20 warranted, and so that, again, is part of why we're 21 here with the non-concurrence.
22 Slide 10 here -- and almost done, just one 23 more slide after this. But this goes into what is the 24 timeline for resolving fuel dispersal at operating 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
45 plants?
1 And so, as I was just saying, there isn't 2
a clear timeline because the pathways that we could 3
use to address the issue aren't currently being 4
exercised.
5 There is some research going on. Clearly, 6
the NRC has long been sponsoring research on this 7
topic and we are coming to a better understanding.
8 But in the timeline for when the staff get knowledge 9
get implemented, if necessary, or demonstrated not to 10 be necessary -- no implementation necessary on 11 operating plants -- that's the part of the timeline I 12 think that is very much less clear, even as there are 13 clear timelines to go to higher burnup, or go to ATF, 14 and we see near-term concepts by maybe even 2027.
15 And so, a lot of these timelines are very 16 short, or fairly near-term, for increasing the burnup.
17 But we don't have a clear timeline or a clear 18 indication that this is definitely going to be 19 addressed, this issue of dispersal, before that, let's 20 say.
21 So, just to conclude. Again, I appreciate 22 everyone's attention. I'm just going to recap a few 23 of the messages.
24 So, the agency intends to issue a 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
46 management-modified safety evaluation on WCAP-18446 1
because that safety evaluation that was modified in 2
the non-concurrence staff's eyes does not assure that 3
the non-concurrence staff's valid safety question 4
concerning fuel dispersal would be addressed, it does 5
not ensure compliance with existing NRC regulations 6
for core cooling.
7 And because that's the bar for adequate 8
protection of public health and safety, there's also 9
a question about that.
10 The agency has existing processes to 11 address emergent safety questions, which we talked 12 about forward-looking and backfit, but they are not 13 presently being used for the fuel dispersal issue, 14 even though there is some research going on that 15 hopefully will eventually help us make a good decision 16 on this topic in the future.
17 The NRC as an agency doesn't have a 18 comprehensive and definitive plan for resolving the 19 fuel dispersal safety question, even as there are 20 plans to go forward with higher burnup and ATF and 21 other things.
22 This may be something that gets addressed 23 in the future, increased enrichment rulemaking. But 24 again, we are not here to sort of anticipate and guess 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
47 what that might turn out, or what that might become, 1
or when that might happen.
2 We're here as a staff. We're only 3
empowered to enforce the regulations that are on the 4
books right now. That's our job. It's not to come up 5
with something as an alternative to that.
6 And so, that is why Kevin, again, and 7
myself, we're not comfortable and could not concur 8
upon the modified safety evaluation.
9 So, again, thank you for everyone's time.
10 And any questions, we're happy to address them.
11 MEMBER BALLINGER: Thank you. Because 12 we're in the open session and I want to make sure that 13 we have this on the record, that my personal opinion 14 is that the increased enrichment rulemaking process, 15 which is a train that's really quite accelerated 16 compared to other staff processes in the past, like 17 Light Speed, will directly assess this issue.
18 And while it may not resolve the issue, it 19 certainly would produce the plan that you're saying we 20 need.
21 So, I want to be sure that that's on the 22 record. Thank you.
23 MR. LEHNING: Sure. And I'll just respond 24 to that. I mean, that was one option that we 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
48 considered as an alternative to non-concurring. But 1
at least from our perspective, there's uncertainty, 2
and there may be, like with 50.46(c), that was a 3
rulemaking, it was returned to the staff, eventually 4
-- I don't necessarily think that this is going to 5
follow that same track -- but again, we're not here 6
necessarily to anticipate or try to guess what might 7
happen, but we're tasked with trying to enforce what 8
is on the books now. But I understand your point.
9 VICE CHAIR HALNON: John, can you go back 10 to slide 7? To the three pictures?
11 Now, that center picture, can you explain 12 how the TMI-2 accident -- which is our classic 13 empirical example of FFRD, if you will, even though 14 the EFPY wasn't there, but that doesn't matter, we 15 ended up with relocation, fragmentation -- we were 16 able to obviously show that 50.46 was fine.
17 We had a coolable geometry and we did 18 relocate. There was no problem with long-term 19 cooling. How did that factor into your comfort zone 20 or discomfort zone, relative to this issue?
21 MR. LEHNING: That's a good question. And 22 I think the staff would first acknowledge that in the 23 end it turned out that TMI was able to be cooled in 24 the geometry.
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49 And so, I think it's clear that the left 1
side of this figure, the 50.46 acceptance criteria, 2
they are conservative to the physical reality of where 3
that actual coolability boundary is.
4 And I think part of the difficulty with 5
TMI and trying to credit coolability at a different 6
threshold than what's in the current regulations, is 7
that in general, it's difficult to analytically make 8
predictions.
9 And so, we'd like to be able to use 10 methods that are validated and that we have high 11 assurance of. Because what was it exactly about TMI?
12 If it were changed in some other way, would it still 13 be coolable? Or if it happened in a different way?
14 These are difficult questions in general 15 to address. And so, I would just again acknowledge 16 the point that there is a significant amount of margin 17 between the acceptance criteria and TMI.
18 And so, some of those would be risk-19 informed ways to look at it. Maybe that would go into 20 things like whether a backfit might be justified. But 21 again, from the forward-looking perspective, the way 22 the staff are trained to look at this would be that 23 we're trying to address this issue relative to what 24 the actual regulatory requirements are.
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50 And then if the Commission at some point 1
wants to relax those and say, because of TMI, it's 2
acceptable to come up with some other alternative, 3
then we would regulate to that instead.
4 VICE CHAIR HALNON: Okay. Not to put 5
words in your mouth, but is that margin you talked 6
about with the 50.46 part of the reason it's not 7
termed an immediate safety issue at this point? This 8
FFRD?
9 MR. LEHNING: I think that might be fair.
10 I mean, I would let maybe the management speak a 11 little bit more to that point.
12 But I think that that could be part of it.
13 There could also be things with the initiating event 14 frequency. Maybe just how frequently does a large 15 break occur? I've heard that used before.
16 And then I think there may also be an idea 17 that some of the interpretations in the research that 18 the staff here has cited -- on slide 2 I think it was 19
-- that there's some conservatisms in the way that 20 those experiments were done.
21 And so, I say those would be three things 22 that someone who was arguing the counter might bring 23 up as to why it's not an immediate safety issue.
24 VICE CHAIR HALNON: Okay. One last 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
51 question, the 55 number that we talked about, the 1
limit. How absolute is that? I mean, how much margin 2
or uncertainty is that on the top end, versus how much 3
-- maybe it could be even lower.
4 I mean, give me a sense of where we are 5
with that. Because my sense is that it was a point on 6
a graph that someone showed, it said, kind of looks 7
like it's dropping off here. Could be a little bit 8
less, a little bit more, but probably a little bit 9
more.
10 MR. LEHNING: I think you're right to ask 11 that question. And where I think you're going, I 12 think there is still a bit of uncertainty about where 13 that threshold is, and that's threshold, the staff did 14 attempt to define that in a conservative way, and 15 that's sort of the incipient threshold for where we 16 believe, based on a limited -- I mean, a reasonable 17 number, but still somewhat limited. It's not as if we 18 had hundreds of thousands of data points.
19 And so, I would say that there is some 20 uncertainty there. And then there are also, there's 21 uncertainty, but because defining the threshold, just 22 as a function of burnup, is also somewhat of a 23 simplification. There are power history effects that 24 likely, very likely, influence this as well.
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52 VICE CHAIR HALNON: Okay, thank you.
1 MEMBER BALLINGER: I might add that we 2
wrote a letter on the RIL in which some of that 3
language we related.
4 Also, one last thing. Again, a personal 5
opinion, this Committee is well aware and has been, of 6
FFRD for some time, partially because of the non-7 concurrence. So, it's a good thing.
8 And then I'm -- again, personal opinion --
9 I believe that we will follow this carefully and in a 10 timely way, so that the time schedule will not become 11 50.46(c) dash infinity.
12 MR. LEHNING: Appreciate that.
13 MR. HELLER: So, this is Kevin Heller with 14 the staff. I just wanted to kind of make a comment, 15 because I know this comes up in various conversations.
16 But the 55 gigawatt day metric ton number that gets 17 thrown around from that RIL, is actually a local 18 pellet burnup number, it's not a rod average.
19 The only reason I point that out is 20 because if we were to consider rod average equivalent 21 of that, then we're talking somewhere in the high 22 40's.
23 And so, in some conversations, we may have 24 a tendency to take a look at that 55 and say, well, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
53 that's not too far removed from the current licensing 1
limit. But actually, it's more toward the high 40's.
2 And so, maybe it's not as narrow as we perceive.
3 MEMBER BALLINGER: Thank you. Scott, 4
would you like to make a comment?
5 MR. KREPEL (through Interpreter): Hi.
6 Yes, this is Scott. Sure. I will provide the 7
management response and talking points, and Kate is 8
going to be sharing the slides for me, I believe.
9 So, I would like to say, first, it was a 10 bit challenging to summarize the slides. I had five 11 slides previously for the subcommittee, and I feel 12 like it was trying to extract water from uranium 13 dioxide.
14 But I have three slides now so I did my 15 best. And the first thing that I will say is that I 16 wanted to emphasize that management does totally 17 understand the staff's concern. And we hear them.
18 And we also don't disagree with them. The 19 reason for moving forward with them on concurrence 20 though, with regards to how the CT evaluation is 21 written -- and first and foremost, I will briefly 22 cover this in the next few slides, but I do want to 23 recognize that management is addressing this through 24 other activities throughout the agency.
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54 And this topical report specifically, the 1
staff reviewed it and agreed that there is an 2
acceptable methodology to analyze the fuel rod average 3
burnup above 62.
4 Additionally, Westinghouse provided 5
sufficient information to suggest that there would not 6
be any significant changes in how the core currently 7
operates, which could potentially lead to more FFRD.
8 So, from the view of the management, and 9
putting in the scope of this topical report for all of 10 those issues -- give me one second. I'm actually 11 going to go to the next slide.
12 Okay. So, I wanted to touch on a few 13 points here, and I can open it up to questions if you 14 want to get into more details.
15 But the current position with the current 16 license burnup, up to 62 gigawatt days per MTU rod 17 average burnup, is not necessarily a current safety 18 issue, as there has been some studies that have 19 previously looked at this and they did use the 55 as 20 the threshold, and it was estimated to be about 200 21 kilograms of uranium dioxide.
22 However, those analyses do have a lot of 23 conservatisms built into the them, and a lot of 24 assumptions that all of the fuel fragments within the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
55 region would leave the rod, which isn't necessarily 1
what would happen, based on experimental data.
2 Additionally, those limits do not include 3
ballooning, and the ballooning that is included is 4
only looking at the rod spacer grid, which is 5
something that has been demonstrated through 6
experimental analysis and a limited amount of 7
ballooning. So, the actual number is significantly 8
lower than 200 kilograms, which is what we believe at 9
this point.
10 So, when we get to that point -- and we're 11 really talking about worst-case scenario at the end of 12 the cycle here -- so if we're looking at dozens, maybe 13 a few more kilograms of FFRD material.
14 And that's enough to fill a few coffee 15 cups perhaps the size of the one that Kevin has 16 sitting next to him.
17 So, that dispersal in the area, in a big 18 core, really becomes difficult to determine from 19 engineering judgment to say, well, this would 20 definitely be a problem for core coolability.
21 We also have the RIL here. And the RIL 22 doesn't really significantly impact the conclusions 23 that we previously had, and that we did consider.
24 And we did consider those kinds of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
56 situations in the RIL as upper bounding from previous 1
analysis. Next slide, Kate?
2 MEMBER PETTI: Can I ask a question?
3 MR. KREPEL: Of course?
4 MEMBER PETTI: I'm confused. The SECY '15 5
said what it said about FFRD. Why was the RIL issued 6
in 2021, if not to raise a flag, by the research staff 7
at least, I think, felt compelled to say, hey, look, 8
the data's here. This looks like an emerging issue.
9 Yet, you just said that the RIL didn't 10 really change what was in the SECY 2015. So, that's 11 just surprised me. We've spent a lot of time on the 12 RIL.
13 MEMBER BALLINGER: Yeah, I was present at 14 the creation, as you were, with the RIL. And it did 15 say exactly what you're saying. It did raise the 16 question.
17 And the back-and-forth that we had with 18 respect to reconciliation and things like that 19 reflected our views on the importance.
20 MR. KREPEL: Okay, I would like to 21 respond to that comment. So, with the SECY that 22 you're referencing, at that time we did have a variety 23 of ranges of analyses.
24 And the RIL then gave us more information.
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57 With that more information, we had a better 1
understanding, probably on the worst end of the 2
spectrum, of what we were considering back then.
3 With that being said, the RIL is something 4
that does help inform how we plan to move forward and 5
where we need to look more into, and what have you.
6 It still did not really change our basic conclusion 7
from 2015 though.
8 Okay. With that being said, I am going to 9
continue. So, in this last slide, I wanted to 10 summarize where we're going with FFRD and how we're 11 moving forward.
12 As you know, we do have a pert, which I 13 know you're also very interested in, that would be 14 published within the next month or so. And I do think 15 that as needed, we can identify gaps in the knowledge, 16 and we can address those gaps and do some follow-up 17 research.
18 Additionally, we have the increased 19 enrichment rulemaking. As you see, I have the dates 20 here on the slide, so we have the draft rule, as well 21 as the final rule. And this is the current schedule 22 as it stands.
23 I do expect that we will establish some 24 sort of regulation or regulatory framework to address 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
58 FFRD, because we're not going to be able to address 1
all of the technical issues.
2 And this is going to put us in a space to 3
address those technical issues and be able to address 4
how this applies to the core coolability and FFRD.
5 We also have parallel efforts that are 6
happening, like the ALS topical report, which is a 7
potential alternative to the technical basis, or FFRD.
8 And so, I want to really quickly address 9
the forward look and backfit, specifically, that was 10 mentioned today.
11 So, for future looking or forward fit did 12 not previously seem appropriate for this particular 13 topical report, because they did not intend to apply 14 the certain items that we had discussed today. So, we 15 were looking at just above 62. And so, it did not 16 make things worse for below 62.
17 Additionally, we could move forward with 18 a backfit if the NRC believes it to be necessary.
19 However, in my view, the backfit evaluation, as per 20 the 109 evaluation that is done to justify the 21
- backfit, right now we don't have sufficient 22 information to support that type of evaluation.
23 If we were to get to the point where we do 24 identify sufficient information to support something 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
59 like that, then of course, we would pursue it at that 1
time, as regulators.
2 MEMBER PETTI: Another question. I'm sure 3
we'll be able to look at the draft rule, and the final 4
rule will be in there somewhere that's still a ways 5
off. It'd be interesting just to hear about the pert 6
results, if possible.
7 (Simultaneous speaking.)
8 MR. KREPEL: We've been asking for the 9
pert --
10 MEMBER PETTI: Yeah, I just want to get it 11 on the record, given it's almost there. Not to wait 12 until there's a regulatory driver. Earlier, just I 13 think because there's a lot of interest in the issue, 14 to get it on our schedule.
15 MEMBER ROBERTS: Scott, you made the point 16 that this particular topical report actually is kind 17 of safety-neutral, because the licensee did some look 18 to make sure that there was no increased exposure in 19 the range of burnups under 62 that were thought to be 20 possible with FFRD.
21 And I think I heard last month that the 22 non-concurring staff agreed with that conclusion. I 23 guess I wanted to clarify that's the case that the 24 licensee did enough work to at least confirm that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
60 there was no increase in the FFRD risk from this 1
section.
2 MR. LEHNING: I think in the closed 3
session, the staff can address that a little bit more.
4 But I would say that it is definitely true and able to 5
be said in the open session, that for the fuel in the 6
incremental burnup range, we would not see dispersal 7
from that fuel. So, hopefully, that goes some ways to 8
answering that question.
9 MEMBER ROBERTS: Right, but the risk could 10 have an increase if the action led to more fuel in the 11 higher burnup range that's currently allowed, the 55 12 to 62, or whatever the right number is, up to 62.
13 I think your conclusion was that was not 14 the case that there was no increase in risk in the 15 area below the expanded burnup region.
16 MR. LEHNING: Yeah, your point about the 17 potential for it to become worse, that is definitely 18 a possibility, and staff reviewed that and thought 19 about that. But our conclusion in that regard is 20 something that we will cover in the closed session.
21 MEMBER ROBERTS: Right. So, in the open 22 session, just want to see if you would -- for the 23 record, you didn't think there was an increase in 24 safety risk based on the work you did, that you'll 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
61 fully describe in the closed session?
1 That it's still a risk, is it, in your 2
view, because the FFRD issue hasn't been resolved 3
below 62, but in this particular case, that you 4
thought there was enough work done to stress there was 5
no increase in safety risk by the strategy for the 6
assemblies above 62?
7 MR. LEHNING: Just because I'm not exactly 8
sure where the boundary is of proprietary vs. non-9 proprietary, I'm going to withhold, again, from 10 answering that.
11 But in the non-concurrence document 12 itself, it does talk about the add-up. Clearly, our 13 next presentation is going to talk about that too.
14 If Westinghouse wants to speak in the open 15 session here about what their rationale is for their 16 topical report, I would let them do that. But I just 17 want to be respectful of what the boundaries are.
18 MEMBER BALLINGER: Okay, thank you. Are 19 there any other questions?
20 (Simultaneous speaking.)
21 CHAIR KIRCHNER: I think one thing in the 22 open session that I hope isn't lost, is that -- this 23 is a useful discussion, first of all. So, thank you.
24 But from the technical standpoint, what I 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
62 believe the applicant is proposing and the staff 1
basically has reviewed and approved, is a new figure 2
of merit that goes beyond the existing 50.46. And 3
that is that they're not going to have clad failure.
4 And that becomes more limiting, and that is well 5
below, for example, 2200 degrees Fahrenheit.
6 And I just want to point that out, that 7
this is a new parameter, so to speak, figure of merit 8
that's being applied that actually is below some of 9
the other already currently accepted figures of merit.
10 And we don't know, for example -- I don't 11 want to open up a can of worms exactly, but at 2200, 12 that's a rather artificial number. You could probably 13 be ballooning clad below 2200, statistically. There 14 are a lot of variables, and so on.
15 So, we have in effect Appendix A6 and such 16 accepted thresholds that are used for regulatory 17 purposes.
18 My sense, from what has been presented, is 19 that this figure of merit will be more limiting, in 20 terms of preserving cladding integrity, geometry, and 21 other important variables that, for coolability 22 demonstration and coolability of the core, in effect 23 is more limiting than the existing accepted criteria.
24 I don't know that I said this very well.
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63 But it's an effect, the effect, on new figure of merit 1
for LOCA announces.
2 MEMBER BALLINGER: I mean, that's where 3
the nexus is on ALS.
4 CHAIR KIRCHNER: Well, I don't know that.
5 What I do know is that it won't get dispersed though.
6 They don't fail the cladding.
7 MEMBER BALLINGER: Well, that's true.
8 CHAIR KIRCHNER: And so, you don't have 9
dispersal, then some of the geometry considerations 10 that could be very hard to analyze with existing 11 methodologies, etc., and have large uncertainties, the 12 first order is avoided.
13 So, I see this as a more restricted figure 14 of merit than what is already out there.
15 (Simultaneous speaking.)
16 MR. LEHNING: And just for the record too, 17 I was nodding my head, but I wanted to agree with what 18 Dr. Kirchner was saying. That is more limiting for 19 those assemblies to which it would be applied.
20 MEMBER BALLINGER: Dennis.
21 MR. BLEY: Yeah, Ron.
22 MEMBER BALLINGER: I'm not sure how long 23 you've had your hand raised, but --
24 MR. BLEY: Doesn't matter. To me, the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
64 staff has made a good case for their role in staying 1
within the regulations.
2 Staff management -- and this is my 3
interpretation is going beyond
- that, but 4
essentially staying within the regulations by making 5
a judgment about how likely the situation is.
6 And the one thing that bothers me about 7
that is the pert should really precede judgments about 8
that sort of thing, until that's well-established.
9 And for some reason, it's lagging behind everything.
10 MEMBER BALLINGER: Other questions from 11 members?
12 MEMBER PETTI: I just had a question. I 13 was trying to follow the slides. What's on Sharepoint 14 is all subcommittee stuff. So, we got to make sure 15 that the full Committee slides get put --
16 (Simultaneous speaking.)
17 MEMBER BALLINGER: Yeah, not only did we 18 notice that, but the date is April 2nd.
19 MEMBER PETTI: Right, right.
20 MEMBER BALLINGER: And so, we're working 21 on that. Okay, I think, back to the chair, we should 22 go out for public comment?
23 CHAIR KIRCHNER: Yes. Yes, go ahead, Ron.
24 MEMBER BALLINGER: So, if there are 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
65 members of the public that wish to make a comment, 1
please state your name and organization, and make your 2
comment. Ed?
3 MR. LYMAN: Yes, this Edward Lyman from --
4 sorry, can you hear me? Edward Lyman from Union --
5 (Simultaneous speaking.)
6 CHAIR KIRCHNER: Yes, go ahead, Ed. We 7
can hear you.
8 MR. LYMAN: Great, thanks. Yeah, I'd just 9
like to state our support for the staff non-10 concurrence. So, I think that the non-concurring 11 staff have made a pretty devastating case that is a 12 serious problem here, a problem that the existing 13 processes have really failed to adequately address for 14 a very long time.
15 And from my perspective as a member of the 16 public, I do not have any confidence that the existing 17 burnup limits, at 62, are sufficiently protective 18 against the propagating consequences of a LOCA.
19 That burnup limit was licensed based on 20 incorrect information. For whatever reason, the 21 Commission has not solved that problem.
22 (Audio interference.)
23 CHAIR KIRCHNER: You're breaking up.
24 (Audio interference.)
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66 MR.
LYMAN:
So, it is entirely 1
appropriate, as so many people said, this topical 2
report is a bow wave. This is the perfect time for 3
this issue to be addressed. And it's simply logical 4
that Westinghouse should not be allowed to increase 5
burnup without resolving the question of whether the 6
existing burnups are already safe. So, it makes a lot 7
of sense to us.
8 Also have to look at the context, the 9
potential for power-up rates, the aging reactor fleet.
10 This isn't happening in a vacuum.
11 So, again, we think the time has come for 12 something to happen to force this issue to be 13 addressed. And so, again, I think the non-concurring 14 staff has made a very strong case for that. Thank 15 you.
16 MEMBER BALLINGER: Thank you. Are there 17 other members of the public that would like to make a 18 comment? I don't see any. Oh, I do see. Somebody 19 named Jeremy Dean?
20 MR. DEAN: Hi. Yeah, can you all hear me?
21 MEMBER BALLINGER: Yeah.
22 MR. DEAN: Okay. So, Jeremy Dean, I'm in 23 the nuclear performance and review branch with John 24 and Kevin.
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67 I was one of the sounding boards that they 1
used to decide whether or not they should go forward 2
with this non-concurrence.
3 And I guess the point that I was pretty 4
skeptical of where they were going with it until one 5
point was pretty eloquently made to me, that for the 6
higher burnup fuel, instituting new criteria, like 7
FFRD compliance, is perfectly within scope of a 8
topical report. And how can you judge whether such 9
criteria are met if you can't say that those criteria 10 would be met for the existing fuel?
11 So, the limitation and condition that they 12 came up with seemed perfect to address that question 13 and allow this topical report to go forward.
14 So, I just wanted to chime in with that 15 perspective, to say I was a pretty hard skeptic, but 16 then even though I didn't sign on to the non-17 concurrence, I do agree with it.
18 MEMBER BALLINGER: Thank you. Other 19 members of the public? I don't see any hand up.
20 Okay, Chairman Kirchner, I suggest that we take a 21 break while we transition.
22 CHAIR KIRCHNER: Yes. So, we are going to 23 take a break until 10:00 a.m., Eastern Time, while we 24 transition to closed session.
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68 And after our closed session, we, through 1
our staff, will alert the public when we are back 2
online for or deliberations and subsequent letter-3 writing.
4 MR. BURKHART: Yes, Chairman. This is 5
Larry Burkhart. I would propose that the public tie 6
back on in accordance with our internal agenda, at 7
10:50 until 11:00, to resume the public portion of the 8
meeting. That gives an hour closed session, 9
approximately.
10 So, we'll be back online once the chairman 11 stops the session, at 10:50. That's what I would 12 propose, Chair.
13 CHAIR KIRCHNER: So, we are in recess for 14 the public until roughly 11:00, Eastern Time. Thank 15 you.
16 (Whereupon, the above-entitled matter went 17 off the record at 9:49 a.m.)
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ADOPT, AXIOM, Optimized ZIRLO, and ZIRLO are trademarks or registered trademarks of Westinghouse Electric Company LLC, its subsidiaries and/or its affiliates in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.
© 2024 Westinghouse Electric Company LLC All Rights Reserved LTR-NRC-24-11, Enclosure 2 Page 2 of 15
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Open Session Jeffrey Kobelak Safety Analysis, Westinghouse Electric Company May 2024 Meeting of the Advisory Committee on Reactor Safeguards (ACRS)
Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs, Westinghouse Topical Report WCAP-18446-P/NP LTR-NRC-24-11, Enclosure 2 Page 3 of 15
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Burnup Extension Program as 2-Step Process Step 1: Increase burnup limit for rods in peripheral assemblies above 62 GWd/MTU Step 2: Increase burnup limit for entire core to above 70 GWd/MTU with enrichment increase LTR-NRC-24-11, Enclosure 2 Page 4 of 15
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Westinghouse EnCore Fuel and High Energy Fuel Programs Approved Under Review Under Development Long Term 1
2 3
Uranium Nitride (UN) Pellets SiGATM Silicon Carbide (SiC) Composite Cladding Photo courtesy of Los Alamos National Lab Chromium-Coated Zr Cladding ADOPT Pellets Product and Methods Evolution Incremental Burnup Full Core High Burnup Higher Enrichment AXIOM Cladding Chromium-Coated Cladding Timeline of Various Products EPRI Alternate Licensing Strategy 4
LTR-NRC-24-11, Enclosure 2 Page 5 of 15
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Incremental Burnup Extension Benefits
- Primary benefit is improved fuel utilization
- Enabling higher region discharge burnup improved fuel utilization
- Target is to reduce number of required feed assemblies each reload
- Improved backend cost
- Optimum utilization of spent fuel pool capacity with higher burnup fuel
- Lower dry cask storage needs with fewer fuel assemblies
- Less volume for permanent storage
- Westinghouse has contracted with customers to implement ADOPT fuel, AXIOM cladding, and the incremental burnup extension (once approved)
LTR-NRC-24-11, Enclosure 2 Page 6 of 15
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Incremental Burnup Extension Applicability
- Fuel Rod Average Burnup
- > 62 GWd/MTU
- Fuel Rod Initial Enrichment
- < 5 w/o enrichment
- Core Location
- Peripheral Assemblies
- Fuel Assembly Designs
- All
- Cladding Materials
, and AXIOM cladding
- Chromium-coated cladding (future)
- Fuel Pellets
- Standard UO2 and ADOPT fuel pellets Incremental Burnup Extension Fuel Rod Design Mechanical Design Safety Analysis Containment Analysis Dose Nuclear Design Thermal Hydraulic Design LTR-NRC-24-11, Enclosure 2 Page 7 of 15
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Incremental Burnup Extension Topical Report Overview
- WCAP-18446-P/NP was written to ensure efficient implementation of the incremental burnup extension
- Limitations associated with prior topical reports which are superseded are identified in Section 1.4
- Limitations of applicability clearly defined in Section 7.1
- Licensee actions for implementation are discussed in Section 7.2
- Impacts of incremental burnup extension addressed functional area-by-functional area
- Codes
- Methods
- Acceptance Criteria LTR-NRC-24-11, Enclosure 2 Page 8 of 15
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Incremental Burnup Extension Topical Report Overview
- Mechanical Design
- Fuel assembly design bases
- Structural components
- Materials
- Core and Fuel Rod Performance
- Fuel Rod Design
- Justify application of PAD5 to incremental burnup regime
- Nuclear Design
- Codes are already applicable to incremental burnup regime
- Thermal-Hydraulic Design
- Incremental burnup rods are non-limiting for rod bow due to low power LTR-NRC-24-11, Enclosure 2 Page 9 of 15
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Incremental Burnup Extension Topical Report Overview
- Loss-of-Coolant Accident Analysis
- Update codes and methods to analyze higher burnup fuel rods
- Address potential for fuel dispersal from fuel rods in the incremental burnup regime
- Transient and Containment Analysis
- Assess / update decay heat modeling for analysis of higher burnup fuel rods
- Address phenomena for high burnup fuel rods related to reactivity insertion accidents
- Radiological Consequence Analysis
- Account for higher burnup fuel rods in dose analyses LTR-NRC-24-11, Enclosure 2 Page 10 of 15
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Fuel Fragmentation, Relocation, and Dispersal (FFRD)
- Research regarding FFRD ongoing for the last decade
- Safety assessments were completed for FFRD relative to design basis non-LOCA and LOCA transients and accidents
- SECY-15-0148: The experimental results have continued to support the hypothesis that FFRD phenomena are primarily a high burnup fuel issue and that the current licensing limits in the U.S. are adequate to prevent dispersal of large quantities of fine fuel fragments.
- RIL 2021-13 issued to provide conservative interpretation of subset of FFRD-related data at the time of publication
- Incremental burnup extension considers potential for dispersal during various accidents and transients LTR-NRC-24-11, Enclosure 2 Page 11 of 15
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Incremental Burnup Topical Report Schedule
- Topical Report Submittal December 2020
- NRC Acceptance Review March 2021
- First Round of RAIs Issued December 2021
- Responses to Round 1 RAIs June 2022
- Second Round of RAIs Issued September 2022
- Responses to Round 2 RAIs February 2023
- Draft SER Issued March 2024
- ACRS Sub-Committee April 2024
- ACRS Full Committee May 2024
- Final SER to be Issued June 2024 LTR-NRC-24-11, Enclosure 2 Page 12 of 15
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Questions LTR-NRC-24-11, Enclosure 2 Page 13 of 15
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Acronyms / Codes / Labels Acronym Definition ACRS Advisory Committee on Reactor Safeguards ADOPT Advanced Doped Pellet Technology ALS Alternate Licensing Strategy (for FFRD)
DNB Departure from Nucleate Boiling DNBR Departure from Nucleate Boiling Ratio EPRI Electric Power Research Institute FFRD Fuel Fragmentation, Relocation, and Dispersal LOCA Loss-of-Coolant Accident NRC Nuclear Regulatory Commission PAD Performance Analysis and Design LTR-NRC-24-11, Enclosure 2 Page 14 of 15
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Acronyms / Codes / Labels (continued)
Acronym Definition RAI Request for Additional Information RIL Research Information Letter SER Safety Evaluation Report SiC Silicon Carbide UN Uranium Nitride LTR-NRC-24-11, Enclosure 2 Page 15 of 15
Key Regulatory Requirements and Guidance
- Non-Loss-of-Coolant Accidents and Transients
- NUREG-0800, Standard Review Plan, Chapter 15
- Regulatory Guide 1.203, Transient and Accident Analysis Methods
- Combined reactivity control systems capability
- Reactivity limits
- Regulatory Guide 1.236, Pressurized-Water Reactor Control Rod Ejection and Boiling-Water Reactor Control Rod Drop Accidents 7
Key Regulatory Requirements and Guidance
- Containment
- General Design Criterion 50, Containment design basis
- Technical Specifications
- Radiological Dose
Fuel Assembly Mechanical Design
- Westinghouse proposed a methodology for extending the burnup limit for fuel assemblies
- A set of design criteria
- A method of evaluating against that criteria
- The results of the evaluation for a specific design
- The 17x17 OFA design is generically approved for an incremental burnup extension. Other designs can be approved on a generic or plant-specific basis per L&C 1
- The NRC staff found that the proposed assembly design criteria and evaluation methods were acceptable 9
Core and Fuel Rod Performance
- WCAP-18446-P/NP presents discussions across three separate phenomenological areas of Westinghouse codes and methods to justify extending the rod-average burnup limit:
- 1. Fuel rod performance
- 2. Nuclear design
- 3. Core thermal-hydraulic design 10
Fuel Rod Performance
- Analyses will use the NRC-approved PAD5 code (L&C 7)
- Westinghouse evaluated the applicability of key models in the extended burnup range for each fuel rod design basis:
- NRC staff assessed these models and underlying phenomena and found them acceptable within WCAP-18446-P/NP (L&C 4, L&C 10) 11
- Fuel rod internal pressure
- Fuel rod cladding stress
- Fuel rod cladding strain
- Pellet-cladding interaction
- Fuel cladding oxidation and hydriding
- Fuel temperature
- Clad free standing
- Fuel cladding fatigue
- Fuel cladding flattening
- Fuel rod axial growth
- Fuel cladding wear
Nuclear Design Westinghouse proposed to continue using existing nuclear design codes
- PARAGON or PHOENIX-P for lattice transport calculations
- ANC for two-and three-dimensional nodal calculations Westinghouse asserted these codes are applicable to increased burnup conditions with existing 5% uranium enrichment limit NRC staff examined overall performance and two areas most likely to be stressed at an extended burnup range:
- Production and depletion of major uranium and plutonium isotopes
- Modeling increased critical boron concentrations Staff found these codes acceptable within the scope of WCAP-18446-P/NP 12
Thermal-Hydraulic Design
- Westinghouse proposed that no modifications are necessary to existing methods for analyzing departure for nucleate boiling
- DNB correlations
- VIPRE/W code
- Revised Thermal Design Procedure, Westinghouse Thermal Design Procedure, etc.
- DNB propagation
- Fuel rod bow
- The NRC staff found the T/H codes and methods are applicable up to the requested rod-average burnup extension limit 13
Non-Loss-of-Coolant Accident Analysis Methods
- Transient (Anticipated Operational Occurrence) Analysis
- Westinghouse divided these events into two categories:
- Events dependent upon core-average effects
- Events analyzed to assess local fuel rod behavior
- Westinghouse stated that approved evaluation models remain applicable 15
Non-Loss-of-Coolant Accident Analysis Methods
- Reactivity Insertion Accidents
- Westinghouse discussed its conformance with the fuel cladding failure thresholds in RG 1.236:
- Peak radial average fuel enthalpy (calories per gram)
- Departure from nucleate boiling
- Pellet-cladding mechanical interaction
- Fuel pellet incipient melting
- Westinghouse proposed to apply its multi-dimensional kinetics methodology (WCAP-15806-P-A) or another approved evaluation model for this event
- No fuel dispersal permitted for fuel rods in incremental burnup range 16
Non-Loss-of-Coolant Accident Analysis Methods
- Containment integrity analysis for LOCA and main steam line break (MSLB)
- Short-term mass and energy release
- Dominated by system conditions, not fuel conditions
- E.g., break area, system temperature, pressure
- Not impacted by incremental burnup extension
- Long-term mass and energy release
- Conservative modeling of decay heat and other parameters
- As supported by Limitations and Conditions 13 and 14 17
Radiological Consequence Analysis
- Westinghouse addressed the radiological consequences of three types of accidents:
- LOCA
- Non-LOCA accidents
- Steam generator tube rupture
- Main steam line break
- Reactor coolant pump locked rotor
- Control rod ejection
- Fuel handling accident
- General non-proprietary information provided in open presentation 18
Radiological Consequence Analysis:
LOCA & Non-LOCA Accidents
- Westinghouse concluded that applicable guidance, and the codes and methods it uses to conform thereto, remain applicable for fuel in the incremental burnup range
- Existing technical specifications limit activity of primary and secondary systems for certain non-LOCA accidents 19
Radiological Consequence Analysis:
Fuel Handling Accident
- Impact of fuel dispersal for non-LOCA accidents not generically addressed in existing regulatory guidance
- Westinghouse considered the impacts of key factors, including
- Behavior of key short-and long-lived radionuclides
- Expected power history for fuel in incremental burnup range
- Expected extent of fragmentation and dispersal
- Licensees will explicitly address fuel-handling accident consequences as part of license amendment requests proposing an incremental burnup extension 20
Applicability to ADOPT and AXIOM
- The Scope of WCAP-18446 includes ADOPT fuel pellets and AXIOM cladding
- ADOPT and AXIOM previously approved up to current burnup limits
- The NRC staff found that the methodology is applicable ADOPT and AXIOM and that design specific models are acceptable up to the extended burnup limit 21
Limitations and Conditions
- The NRC staffs draft safety evaluation contains 14 limitations and conditions that licensees adopting the methodology must address
- Incorporated therein are 9 limitations Westinghouse proposed in WCAP-18446-P/NP or RAI responses
- NRC staff modified several of the limitations proposed by Westinghouse
- Eight limitations and conditions have been noted in the foregoing presentation
- The remaining 6 will be discussed during the closed presentation 23
Conclusions
- The NRC staff found the WCAP-18446-P/NP incremental burnup methodology provides an acceptable approach for comprehensively evaluating fuel operation within the requested extended burnup limit, addressing
- Fuel assembly mechanical design
- Core and fuel rod performance
- Non-LOCA & LOCA safety analyses
- Radiological Consequences
- The staffs conclusions are predicated upon
- The methodology being used within its approved range of applicability
- Licensees acceptably addressing limitations and conditions in Section 4.0 of the staffs safety evaluation 24
Non-Concurrence Resolution 1
- The technical/safety issues raised by the non-concurrers are being handled within other appropriate activities by the agency.
- The specific issues regarding rod burnups below 62 GWd/MTU are not within the scope of WCAP-18446-P/NP.
Current Position on FFRD <62 GWd/MTU 2
- FFRD at burnups below 62 GWd/MTU are currently not considered to be an imminent safety issue.
- Risk limited to near end of cycle
- Conservatism of assumptions in fuel dispersal
- Limited expected quantity of dispersal
- Distributed nature of dispersal
- Conclusions in SECY-15-0148 were not impacted significantly by information in 2021 RIL.
Path Forward on FFRD 3
- Follow-up research or simple evaluations may be used to address identified gaps
- Increased Enrichment rulemaking
- Current schedule: draft rule 6/2025, final rule 12/2026
- Other parallel licensing efforts
- ALS topical report review
Abbreviations 4
ALS Alternative Licensing Strategy FFRD Fuel Fragmentation, Relocation, and Dispersal GWd/MTU Gigawatt-days per Metric Ton of Uranium IE Increased Enrichment NRC U. S. Nuclear Regulatory Commission PIRT Phenomena Identification and Ranking Table RIL Research Information Paper WCAP-18446-P/NP WCAP-18446-P/WCAP-18446-NP, Revision 0, Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs