ML21321A165
| ML21321A165 | |
| Person / Time | |
|---|---|
| Issue date: | 11/03/2021 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| Brown, C.; Widmayer, D., ACRS | |
| References | |
| NRC-1734 | |
| Download: ML21321A165 (178) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Docket Number: (n/a)
Location: teleconference Date: Wednesday, November 3, 2021 Work Order No.: NRC-1734 Pages 1-132 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W., Suite 200 Washington, D.C. 20009 (202) 234-4433
1 1
2 3
4 DISCLAIMER 5
6 7 UNITED STATES NUCLEAR REGULATORY COMMISSIONS 8 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 9
10 11 The contents of this transcript of the 12 proceeding of the United States Nuclear Regulatory 13 Commission Advisory Committee on Reactor Safeguards, 14 as reported herein, is a record of the discussions 15 recorded at the meeting.
16 17 This transcript has not been reviewed, 18 corrected, and edited, and it may contain 19 inaccuracies.
20 21 22 23 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 UNITED STATES OF AMERICA 2 NUCLEAR REGULATORY COMMISSION 3 + + + + +
4 690TH MEETING 5 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 6 (ACRS) 7 + + + + +
8 WEDNESDAY, NOVEMBER 3, 2021 9 + + + + +
10 The Advisory Committee met via Video 11 Teleconference, at 9:30 a.m. EDT, Matthew W. Sunseri, 12 Chairman, presiding.
13 COMMITTEE MEMBERS:
14 MATTHEW W. SUNSERI, Chairman 15 JOY L. REMPE, Vice Chairman 16 WALTER L. KIRCHNER, Member-at-large 17 RONALD G. BALLINGER, Member 18 VICKI M. BIER, Member 19 DENNIS BLEY, Member 20 CHARLES H. BROWN, JR. Member 21 VESNA B. DIMITRIJEVIC, Member 22 GREGORY HALNON, Member 23 JOSE MARCH-LEUBA, Member 24 DAVID A. PETTI, Member 25 PETER RICCARDELLA, Member 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 1 DESIGNATED FEDERAL OFFICIAL:
2 DEREK WIDMAYER 3
4 ALSO PRESENT:
5 TIMOTHY DRZEWIECKI, NRC NRR 6 GEORGE FLANAGAN, US Department of Energy 7 JORDAN HOELLMAN, NRC NRR 8 DAVID HOLCOMB, US Department of Energy 9 STEVEN LYNCH, NRC NRR 10 MICHAEL ORENAK, NRC NRR 11 MIKE POORE, US Department of Energy 12 CHRIS VAN WERT, NRC NRR 13 14 15 16 17 18 19 20 21 22 23 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
3 1 AGENDA 2 Draft NUREG-2246 on Advanced Reactors Fuel 3 Qualification (Open) (DP/DW) . . . . . . . . . . 6 4 ORNL Report on Molten Salt Reactor 5 Fuel Qualification . . . . . . . . . . . . . . . 85 6
7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 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 1 P R O C E E D I N G S 2 9:30 a.m.
3 CHAIR SUNSERI: All right, this is the 4 second day of the 690th meeting of the Advisory 5 Committee on Reactor Safeguards. The meeting will now 6 come to order.
7 I'm Matthew Sunseri, Chair of the ACRS.
8 I'll call the roll to verify a quorum and make clear 9 communications exist, and I'll start with Ron 10 Ballinger?
11 MEMBER BALLINGER: Here.
12 CHAIR SUNSERI: Vicki Bier?
13 MEMBER BIER: Here.
14 CHAIR SUNSERI: Dennis Bley?
15 MEMBER BLEY: Here.
16 CHAIR SUNSERI: Charles Brown?
17 MEMBER BROWN: Here.
18 CHAIR SUNSERI: Vesna Dimitrijevic?
19 MEMBER DIMITRIJEVIC: Here.
20 CHAIR SUNSERI: Greg Halnon?
21 MEMBER HALNON: Here.
22 CHAIR SUNSERI: Walt Kirchner?
23 MEMBER KIRCHNER: Here.
24 CHAIR SUNSERI: Jose March-Leuba?
25 MEMBER MARCH-LEUBA: Here.
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5 1 CHAIR SUNSERI: Dave Petti?
2 MEMBER PETTI: Here.
3 CHAIR SUNSERI: Joy Rempe?
4 VICE CHAIR REMPE: Here.
5 CHAIR SUNSERI: And myself, so we have all 6 in attendance, thank you, and clear, so we have a 7 quorum and the communications were clear.
8 The designated federal officer for this 9 meeting is Mr. Derek Widmayer. During today's 10 meeting, the committee will be considering the 11 following topics.
12 We will hear presentations on and start a 13 draft, or, I'm sorry, a letter of report on draft 14 NUREG-2246 on advanced reactor fuel qualification.
15 Secondly, we will hear a presentation and 16 report on molten salt reactor fuel qualification, and 17 which we will prepare a letter report on that topic, 18 and we will get into a review of a letter report on 19 the biannual report on the agency research program.
20 The communication link has been opened to 21 allow members of the public to listen in on the 22 presentations and community discussions. We have 23 received no written comments or requests to make oral 24 statements from members of the public regarding 25 today's session.
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6 1 There will be an opportunity for public 2 comment and we have set aside time in the agenda for 3 comments from members of the public attending or 4 listening to our meeting. Written comments may also 5 be forwarded to Mr. Derek Widmayer, the designated 6 federal officer.
7 A transcript of the open portions of the 8 meeting is being kept and it is requested that 9 speakers identify themselves and speak with sufficient 10 clarity and volume so they can readily be heard. And 11 just as a reminder, participants should mute 12 themselves when not speaking.
13 So, that is the agenda for today. Once 14 again, we have full topics, so we will be marching 15 through the agenda pretty deliberately, but we want to 16 take time to thoroughly review the topics, but not 17 overly do that.
18 I'll turn to the members now to see if you 19 have any questions regarding today's agenda or any 20 comments that you want to make, members?
21 All right, then, so we will start with the 22 first item on the agenda and I'll turn to Member Petti 23 for the discussion on the draft NUREG on advanced 24 reactor fuel qualification. Dave, the floor is yours.
25 MEMBER PETTI: Thank you, Matt. Good 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 1 morning, everyone.
2 Just to refresh my colleagues' memories, 3 we heard about this in subcommittee back in February, 4 and since then, I believe the staff's gone out and got 5 public comments and addressed those comments, and 6 we'll hear about all of that today, but first, we'll 7 hear from NRR management, Mike Orenak?
8 MR. ORENAK: Yeah, thank you, Dr. Petti.
9 Good morning. I'm Mike Orenak. I'm the Acting Chief 10 of the Advanced Reactor Technical Branch 1 in NRR.
11 The staff of my branch and I are pleased to introduced 12 the draft NUREG-2246 fuel qualification for advanced 13 reactors.
14 In accordance with the requirements of the 15 Nuclear Energy Innovation and Modernization Act, this 16 NUREG represents an important step in closing the gaps 17 in our guidance for advanced reactor fuels to support 18 transparent, efficient, and thorough safety reviews.
19 The fuel qualification assessment 20 framework contained within this NUREG includes an 21 innovative top-down methodology with a well-defined 22 nexus to safety.
23 This guidance is technology inclusive. It 24 clearly identifies NRC's expectations and incorporates 25 feedback from external and internal stakeholders, and 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 1 external stakeholders including those from the 2 international community.
3 As Dr. Petti mentioned, the staff 4 presented the majority of this guidance to the Future 5 Plant Design Subcommittee on February 2. However, 6 this guidance was simply a draft NRC white paper at 7 the time.
8 Also, the staff has converted this white 9 paper into a draft NUREG, incorporating comments from 10 industry's Accelerated Fuel Qualification Working 11 Group, and issued the draft NUREG for public comment 12 in June of this year.
13 Recently, the staff has been working 14 diligently to respond to all received public comments.
15 These proposed staff responses were discussed at the 16 periodic advanced reactor stakeholder meeting on 17 September 29, which was a little over a month ago.
18 As part of our presentation today, staff 19 will discuss the comments and associated proposed 20 revisions to the NUREG with a specific focus on 21 proposed changes to adding a new Section 2.5 for first 22 core applications, clarifying the language related to 23 general design criteria and advanced reactor design 24 criteria and the relationships to the principal design 25 criteria, and also note ongoing work to exercise this 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 1 proposed framework on non-light water reactor fuel 2 designs, specifically those for metal and TRISO fuel.
3 We're looking forward to receiving the ACRS's feedback 4 today.
5 The staff speaking after me will be the 6 project manager for the NUREG, Jordan Hoellman, who 7 will provide some additional background. Afterward, 8 the lead author, Tim Drzewiecki, will lead the 9 technical discussions on the proposed revisions in 10 response to the public comments. I'll now turn my 11 presentation over to Jordan.
12 MR. HOELLMAN: Great, thanks, Mike. Good 13 morning, everyone. Can you all hear me okay?
14 MEMBER PETTI: Yes.
15 MR. HOELLMAN: Okay, great. I'm going to 16 move to slide two. Again, my name is Jordan Hoellman.
17 I'm a project manager in the Advanced Reactor Policy 18 Branch in NRR and I've been the project manager for 19 this NUREG.
20 So, this slide just provides an outline of 21 what we're planning to discuss today. I'll provide a 22 little bit more background information and some, you 23 know, recap the purpose and considerations of the 24 NUREG, and then I'll turn it over to Tim to really 25 walk through the bulk of the technical stuff and the 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 1 results of the public comment period and proposed 2 revisions to the NUREG.
3 So, moving to slide three, so this slide 4 provides an overview of the history of the work that's 5 contributed to getting us to where we are with the 6 NUREG.
7 We discussed the overall framework at the 8 periodic advanced reactor stakeholder meeting in May 9 of 2020, and we developed the draft white paper 10 incorporating some feedback we received at the May 11 stakeholder meeting to support a discussion on October 12 1 of last year.
13 The draft white paper we discussed at the 14 public meeting was the same draft white paper that we 15 presented to the ACRS subcommittee in February of this 16 year.
17 In this same sort of time period, we were 18 also involved with the Nuclear Energy Agency's Working 19 Group on the Safety of Advanced Reactors or WGSAR, 20 where we interacted with a number of foreign 21 regulators.
22 The foreign regulators saw similar issues, 23 and so we thought that this was a topic that we could 24 work on, and we began working on a paper through that 25 working group, so there is a sister paper that's 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 1 internationally, I think, issued. Tim can correct me 2 if I'm wrong, but I believe that that's been issued.
3 MR. DRZEWIECKI: It's approved, but it's 4 awaiting -- yeah, it's still, yeah, in the process of, 5 you know, being published, but it was approved back in 6 January.
7 MR. HOELLMAN: Okay, thanks, Tim. Yeah, 8 so our draft NUREG is an iteration of the draft white 9 paper with adjustments to address feedback received at 10 stakeholder meetings.
11 As Mike mentioned, we addressed some 12 voluntary comments received from the Accelerated Fuel 13 Qualification Working Group and to address 14 international input as well. So, I'll move to slide 15 four.
16 So, I'll talk a little bit about the 17 purpose of the NUREG, and that is to provide a 18 framework for evaluating an advanced reactor nuclear 19 fuel design.
20 The framework enables an efficient, 21 transparent, and thorough review process by setting 22 clear staff expectations for how the staff would reach 23 the overall finding of fuel is qualified for use.
24 I'll note here that while the guidance is 25 geared towards power reactors, the staff believes that 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 1 the concepts in the NUREG are also applicable to non-2 power reactors as well.
3 The considerations in the NUREG have been 4 informed by staff experience gained from licensing 5 solid fuel reactor designs. That's mainly light water 6 reactor designs, but it also includes considerations 7 from non-light water reactor fuel testing performed to 8 date and considerations from the accelerated fuel 9 qualification or AFQ.
10 And just for everyone's information or if 11 you're not aware, AFQ is a methodology for the 12 development and qualification of new nuclear fuels in 13 an accelerated time frame as compared to the current 14 conventional methodology of fuel qualification.
15 And its goal is to significantly reduce 16 the time to qualify new fuels from what historically 17 has taken more than 20 years to an ultimate duration 18 of as few as five years.
19 The framework focuses on areas where 20 irradiated fuel tests have been required, and the 21 staff continues to believe that the ultimate 22 demonstration of the final fuel design fabricated 23 according to specification, testing at scale, and 24 tested under prototypical conditions will continue to 25 be a necessary step in fuel qualification. So, I'm 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 1 going to move to slide five.
2 PARTICIPANT: I think we have a question.
3 VICE CHAIR REMPE: I have a question.
4 MR. HOELLMAN: Yes, sure. I'm sorry. I 5 can't see hands raised with presenting. Go ahead.
6 VICE CHAIR REMPE: That's okay. I was 7 going to interrupt you, but I wanted to wait until the 8 end of the slide. I was curious about the decision 9 process the staff makes on deciding to do something as 10 a NUREG versus a reg guide. Is there an intent to 11 someday turn this into a reg guide?
12 And then we'll be talking later today 13 where an approach or a methodology is just a NUREG/CR 14 report, and what's the logic used by the staff for 15 selecting the mechanism or the type of document in 16 which information like this is published?
17 MR. HOELLMAN: Yeah, thanks, Dr. Rempe.
18 I guess I'll take a shot and let other people chime in 19 if they want.
20 I think for this one, our thought process 21 was, you know, we thought that the information 22 contained in the draft white paper also included 23 information and things that would be considered by the 24 staff in their review and not just maybe something 25 that we would put in a reg guide that would say this 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 1 is an approved or if you do it this way, it's 2 acceptable. We thought it had a little bit more of 3 acceptance criteria.
4 And this is one thing that sort of got 5 brought up during our internal reviews, and we're 6 going to continue to look at how to make it more clear 7 in the document where guidance may be provided to a 8 potential applicant or where guidance may be sort of 9 provided to the staff in performing a review.
10 So, that's kind of where we landed on this 11 one. I think, you know, as we move into slide five 12 here, we talk about some additional activities to 13 exercise the framework in the NUREG and, you know, the 14 outcomes of those may prompt us to develop something 15 more like a reg guide to sort of put everything 16 together and whatnot, but I think that's --
17 MR. LYNCH: So, this is Steve Lynch, the 18 acting chief for the Advanced Reactor Policy Branch.
19 One thing I can maybe add on to this 20 question is, you know, part of our decision to prepare 21 a NUREG is when the staff is looking to develop new 22 guidance that may not already exist and provides 23 additional details and a methodology that it include, 24 in this case, acceptance criteria and ultimate 25 findings that we're looking to make as part of a 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 1 review where, in some cases, using a reg guide may be 2 more appropriately when we are endorsing preexisting 3 methodologies as acceptable use.
4 So, that's one distinction that is kind of 5 to what extent are we developing new guidance for 6 someone to follow that is looking to prepare 7 information to be reviewed by the NRC.
8 And with this particular activity that 9 we're doing for this framework for fuel qualification, 10 we are developing more information as a methodology 11 for preparing information that sort of augments the 12 already existing standard review plans we have for 13 power reactors and non-power reactors that are 14 prepared as NUREGs.
15 So, this is sort of augmenting those 16 already content of application and standard review 17 plan documents that we have for reactors already.
18 VICE CHAIR REMPE: Okay, that makes sense 19 since the SRP is a NUREG if that's the intent is to 20 augment the standard review plan. Thank you.
21 MR. HOELLMAN: Okay, thanks, Dr. Rempe.
22 So, I'll continue on slide five here. The NUREG 23 contains a technology-inclusive framework for fuel 24 qualification composed of a top-down approach where 25 the top level goal of fuel is qualified for use is 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
16 1 supported by lower level supporting goals.
2 The lower level supporting goals continue 3 to be broken down until they can be satisfied with 4 clear, objective, direct evidence, and then they are 5 considered base goals and identified by the use of 6 gray boxes in the NUREG.
7 The NUREG attempts to identify criteria 8 applicable generically to reactor fuel designs, but 9 the staff recognizes that the role of the fuel in the 10 protection against the release of radioactivity for a 11 specific reactor design may vary.
12 Therefore, some of the criteria may not be 13 applicable in all cases, and in some cases, may not be 14 sufficient, and so the staff has initiated additional 15 activities to exercise the framework for metal fuel 16 and TRISO fuel.
17 And there are also efforts ongoing as Dr.
18 Rempe just mentioned with Oak Ridge National 19 Laboratory related to a NUREG/CR on molten salt 20 reactor fuel qualification.
21 MEMBER PETTI: Jordan, this is Dave, 22 question. I thought in the February briefing, there 23 was also a discussion of picking a really low maturity 24 fuel. I thought General Atomics was working on a 25 carbide fuel, a silicon carbide clad system that you 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 1 would exercise against 2246. Is that still happening?
2 And I thought they even got money from DOE for it.
3 I just worry that picking the more mature 4 fuel system is you won't really run AFQ through its 5 paces, if you will, and I thought, if this is what I'm 6 remembering right, I thought taking a low maturity 7 fuel through it is certainly worth thinking about.
8 MR. DRZEWIECKI: I can speak to that a 9 bit. And so, we did some of that, but it was not 10 exhaustive.
11 And you're right, General Atomics 12 submitted a white paper for NRC staff feedback, and we 13 had provided them written feedback and that feedback 14 was based on comparing it against this draft NUREG.
15 However, that was a lower resource effort, 16 so it's not as exhaustive as these other two are going 17 to be. For what it's worth, we're giving them that 18 feedback. We're meeting with them, I think, on 19 Thursday.
20 MEMBER PETTI: Okay, good.
21 VICE CHAIR REMPE: This is Joy and I have 22 another question and it's related to schedule. As we 23 discussed earlier today, we started off like last 24 February looking at a white paper, and it was about, 25 I don't know, 35 pages, 36 pages long, and then the 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
18 1 June 21 version was 55 pages long.
2 And then, well, I guess last week late, 3 you sent our staff, our designed staff official, our 4 federal official a copy with the markups that went to 5 like 88 pages with all of the markup.
6 So, you know, we're kind of at a process, 7 and I've gone through it and I guess I am okay with 8 all of these changes, although I have some other 9 comments I'll be sharing with you later today, but I'm 10 just wondering, you know, what's driving the schedule 11 to get this meeting out, or have this discussion today 12 versus later when we've had like a full month to 13 review the changes you made, and is it because of 14 these other ongoing activities or what's the rush 15 here?
16 MR. HOELLMAN: This is Jordan. I guess 17 I'll take a shot at that one. So, I think the 18 initial, I think, schedule was driven by the Nuclear 19 Energy Innovation and Modernization Act, which in 20 there, sort of put us in a sort of time frame within 21 two years of the enactment to develop guidance for 22 fuel qualification.
23 So, that's sort of the genesis of how that 24 draft white paper became available and sort of how we 25 started on that sort of process.
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19 1 I would note that the version we provided 2 last week does include the comment, the public comment 3 response, or the public comments received and the 4 responses, so it does add a number of pages just 5 because we're reproducing the public comments and 6 responding to them in the actual document.
7 But the other, what we released in June, 8 I think, from what you've seen in the draft white 9 paper in February, including, you know, some changes 10 to address some comments volunteered from the 11 accelerated fuel qualification community and just 12 other changes, you know, from the internal review 13 processes to get a final, or a draft version issued.
14 VICE CHAIR REMPE: So, the schedule is 15 being driven because of Congress, and are you guys 16 comfortable that you're having adequate time to do the 17 job? You know, are we getting pushed too much by the 18 NEIMA Act and stuff or something? I guess I'm a 19 little concerned about that.
20 MR. LYNCH: This is Steve Lynch, acting 21 chief for the Advanced Reactor Policy Branch. So, 22 with the deadlines that have been provided by NEIMA, 23 you know, we have worked to develop schedules that we 24 believe that the staff can support for developing, you 25 know, the various pieces in response to that, and in 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 1 certain cases, I think we're actually pursuing more 2 aggressive timelines than were prescribed by NEIMA.
3 And one thing I do want to emphasize with 4 this particular effort with NUREG for fuel 5 qualification is that, you know, what you are seeing 6 today, while there has been some evolution over the 7 last several months, you are seeing, you know, the 8 staff having taken into full consideration all of the 9 feedback received from the public and incorporating 10 that into a document that we believe is now 11 technically complete and, you know, represents our 12 best position for moving forward.
13 I do want to, you know, make sure that 14 that is communicated, that, you know, we aren't 15 pushing forward a document to discuss with the ACRS 16 that we believe is still in flux or needs, you know, 17 additional technical consideration.
18 We think we've got what we need to move 19 forward so that we can provide greater certainty to 20 applicants that are moving forward with developing new 21 fuel forms that need to be reviewed by the NRC in the 22 coming months and years.
23 VICE CHAIR REMPE: Are you seeing a lot of 24 applicants begging for this document in the next month 25 or two?
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21 1 MR. HOELLMAN: I would note that the U.S.
2 Nuclear Industry Council's annual survey noted fuel 3 qualification as one of the highest priority 4 regulatory guidance documents that should be 5 developed, but in addition to that, I mean, we do have 6 applicants that are, you know, planning on --
7 MR. LYNCH: Yeah, I would --
8 (Simultaneous speaking.)
9 MR. HOELLMAN: Go ahead, Steve.
10 MR. LYNCH: -- love to receive an 11 application from Kairos Power for their non-power 12 facility and, you know, that includes fuel that we are 13 going to need to take a look at as part of our review 14 of that, and making sure that we've got information 15 that is adequate to support not only the application 16 that we have today from them for the Hermes project, 17 but also for their future full scale facility. So, 18 this is guidance that will be used for current reviews 19 and will support future actions.
20 VICE CHAIR REMPE: Okay, thank you.
21 MR. HOELLMAN: Okay, thanks again, Dr.
22 Rempe. So, I'll move to slide six, and this slide 23 just really provides the links to the draft NUREG that 24 we published in June, as well as links to the three 25 public comment submittals we received.
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22 1 In addition, maybe to address Dr. Rempe's 2 comment, we did get requested to hold a public meeting 3 based on NEI's comment submittal, so that, you know, 4 in addition to responding to public comments and 5 trying to get you guys a document.
6 And I do apologize that we were not able 7 to get you something with, you know, maybe more 8 adequate time for your review, and we certainly 9 understand that this is not, you know, typical or 10 maybe preferred.
11 So, but we have been working hard over the 12 past, you know, two months to get this available and 13 to support this meeting, so I just wanted to mention 14 that again.
15 So, with that, I turn it over to Tim to go 16 through the fuel qualification assessment framework 17 and the results from our public comment responses.
18 MR. DRZEWIECKI: Thanks, Jordan. So, 19 before I go into the comments, I just wanted to give 20 a brief overview of what this framework actually looks 21 like, and before I do that, I have a couple of high 22 level comments I wanted to make.
23 One was to kind of answer the question of 24 who is this for, and I think that kind of also helps 25 to inform why we chose the format of a NUREG that we 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 1 did, and it's for the fact that it's --
2 I mean, certainly it's for people or for 3 any stakeholders, you know, that want to qualify their 4 fuel, but it was also written, you know, for the staff 5 for themselves.
6 So, I want to also, you know, highlight 7 the other authors here, Jeff Schmidt, Chris Van Wert, 8 and Paul Clifford.
9 And so, when we wrote this guidance, we 10 were thinking also of ourselves and how do we 11 structure a safety evaluation in such a way where, you 12 know, we can be efficient and comprehensive and 13 transparent.
14 I do want to point out that, you know, we 15 did share our red line strikeout and there has been 16 lots of changes to the language, but I do want to 17 highlight that the actual logical framework itself, 18 that has been stable.
19 There's been some changes to words, which 20 is important, but the framework itself has not changed 21 really since our draft NUREG was issued.
22 The one thing I do want to highlight, if 23 you compare this NUREG to the white paper, there is 24 one goal that looks different and that would be Goal 25 2.3.1 which is coolable geometry, and that's discussed 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 1 in Section 3.2.3.1.
2 The reason that changed is previously it 3 had three supporting goals, and during an internal 4 review, it was seen as maybe two of them were 5 redundant and should be combined, so we took that 6 feedback and combined it into one, but outside of 7 that, it's been a stable framework.
8 So, with that, I do want to go -- so, next 9 slide, please? So, this framework starts with our top 10 level goal that fuel is qualified for use, and for 11 that, we took a definition that the reasonable 12 assurance exists that fuel, fabricated in accordance 13 with its specification, will perform as described in 14 the safety analysis.
15 And so, from that top level goal, that 16 gets broken down into two separate goals, the box on 17 the left, which is Goal 1, that you have a fuel 18 manufacturer specification that controls the key 19 fabrication parameters, and then the goal that we have 20 on the right is that safety criteria can be satisfied 21 with high confidence.
22 For this abbreviated presentation, I want 23 to go right into Goal 2 on the next slide, please, and 24 this gets broken down into three separate boxes in 25 terms of what are the safety criteria that we're 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 1 talking about. These criteria are coming from our 2 regulations.
3 So, Goal 2.1, the box on the left, that we 4 have margin to design limits can be demonstrated under 5 conditions of normal operation, including AOOs, Goal 6 2.2, that's the box in the middle, margin to 7 radionuclide release limits -- I'm sorry, and the box 8 on the right, Goal 2.3 is the ability to achieve and 9 maintain a safe shutdown can be assured.
10 And so, these are coming from, you know, 11 our regulations. I'm going to talk more about the 12 role of GDC and ARDC here when we go into the 13 comments. Could you confirm that you hear me?
14 VICE CHAIR REMPE: We can hear you.
15 MR. DRZEWIECKI: Okay, thank you. Okay, 16 can we move to the next slide, please? So, now that 17 box that was on the left, that Goal 2.1, I'm going to 18 go into that a little more.
19 And so, that gets broken down really into 20 two items, which is the box on the left, fuel 21 performance envelope, effectively knowing where you're 22 going to be, and then the box on the right, having an 23 evaluation model that can assess the fuel there, 24 effectively, you know, knowing, basically knowing 25 where you're going to be and have a tool that can 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 1 assess you there.
2 Obviously, these get broken down more, but 3 I want to highlight that Goal 2.2.1, having a fuel 4 performance envelope, as Jordan has indicated, that 5 box is gray, meaning we think that is a base goal and 6 it's not broken down any more. We think that that can 7 be specified without any further abstraction of 8 breaking it down more.
9 And then the box that's on the right, Goal 10 2.1.2, that one is blue because that gets broken out 11 into a separate assessment framework specifically for 12 evaluation models because that actually model gets 13 called a few times within this framework. I see a 14 question?
15 VICE CHAIR REMPE: It's Joy again, but go 16 ahead and finish the slide. I just wanted to make 17 sure you didn't go to the next slide, okay?
18 MR. DRZEWIECKI: No, I think I'm good on 19 this slide unless you want me to go through the note, 20 but --
21 VICE CHAIR REMPE: Okay, so this is a 22 little different topic, but during our February 2021, 23 subcommittee meeting, I commented about the disconnect 24 between the Part 53 fundamental safety functions or 25 the critical safety functions sometimes we refer to 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 1 and the fact that this document, which was just the 2 white paper back then, emphasized Reg Guide 1.233.
3 And again, Part 53 always talks about an 4 overarching critical safety function of control 5 radionuclide release, and then there's this 6 acknowledgement about that the supporting critical 7 safety functions may vary depending on the technology.
8 But you'll have controlled radioactivity, 9 controlled heat removal, et cetera, but the et cetera 10 needs to include controlled chemical reactors at least 11 as a consideration because some technologies may not 12 need to worry about it, but other technologies will.
13 And I think it's very important to have 14 that kind of discussion in this document because, as 15 we've mentioned previously today, there's this Oak 16 Ridge molten salt reactor fuel topic coming up where 17 it is important, and corrosion is important.
18 Oxidation is important for different fuel 19 technologies, and to have this document right now --
20 I did a word search in the latest version and I did 21 not find corrosion or chemical attack except for a 22 place in the comments where that phrase was removed.
23 In the complete version, it will no longer 24 have that as the main text, and how that as you're 25 thinking about what the goals are, what you should 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
28 1 think about for the critical safety functions.
2 And I know when I brought it up at the 3 earlier meeting, Amy Cubbage spoke up and said, you 4 know, that's a good point. We'll think about it and 5 get back to you on it. So, I'm here today asking, you 6 know, did you think about it and why wasn't it 7 included?
8 MR. DRZEWIECKI: Yeah, so where this would 9 show up is in terms of -- so I don't have it in these 10 slides, but if you go into the framework and you look 11 at the evaluation model assessment framework, one of 12 the criteria there is going to be do you have the 13 appropriate physics model and in terms of how do you 14 inform that? How do you show that?
15 And so, we didn't go into specific failure 16 or degradation modes there. We do understand that, 17 you know, like, you know, corrosion, or hydrogen 18 pickup, or in this case, chemical attack, could be 19 those physical phenomena.
20 We could add things in there to add those 21 as examples, but we think that that's where it's going 22 to show up. We think within this framework, it makes 23 sense to basically say if you think that a chemical 24 attack or, you know, whether it is or it's not, you 25 should have some kind of basis to explain why you are 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 1 or are not including that as a degradation mechanism.
2 And what I mean by that is, is that model, is that 3 physics actually captured by your evaluation model?
4 So, it was not added specifically because 5 we didn't necessarily think we needed to add that item 6 specifically, but we think that was already addressed 7 by this model, but if you think that it should be 8 called out, that's an easy edit to make.
9 VICE CHAIR REMPE: Well, again, I'm just 10 one member, and as we --
11 (Audio interference.)
12 VICE CHAIR REMPE: -- we'll be proposing, 13 I'll be trying to convince my colleagues that it's 14 important, but again, it's inconsistent with Part 53 15 about the way the critical safety functions should be 16 considered.
17 So, the emphasis on Reg Guide 1.233 is 18 omitting that discussion, and then we see it later on 19 in this Oak Ridge NUREG/CR report where they again go 20 back to 1.233, and then having this guidance for the 21 staff as well as other stakeholders and not calling 22 that out explicitly to me seems omitting a point that, 23 you know, you may know that it's supposed to be 24 considered, but if you don't write it down in the 25 document, I'm not sure that the staff will be all 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 1 thinking the same way as you are today.
2 MR. DRZEWIECKI: Okay, so let me make sure 3 I have this, okay, because, all right, so the note 4 that I'm taking is a chemical attack is not called out 5 specifically in the Section 1.233, nor did you see it 6 in the discussion on the evaluation model assessment 7 framework.
8 VICE CHAIR REMPE: Correct, both places --
9 MR. DRZEWIECKI: Okay.
10 VICE CHAIR REMPE: -- I think it's 11 missing.
12 MEMBER PETTI: And well, and Tim, I 13 actually, I think it's a little bit more subtle. In 14 some cases, the chemical attack would fall here in 15 terms of the performance envelope being defined, 16 right? I mean, if the environmental conditions makes 17 thing, make corrosion an issue, then you better have 18 data, right, and you better have a model.
19 But then if you look at the next one which 20 is the, you know, I think it's the goal that talks 21 about the radionuclide release under accident 22 conditions, there are some accident events, right, 23 that challenge the fuel's ability to retain the 24 radionuclides, one of them being potentially chemical 25 attack.
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31 1 So, it might be worth just, you know, some 2 sentences in both places to cover that.
3 MR. DRZEWIECKI: Okay, so to be clear, 4 that was associated to address both, okay, so both 5 under the goal. Maybe go up one slide, please, just 6 back one slide to slide nine? So, are you saying to 7 have it address both under Goal 2.1 and 2.2?
8 MEMBER PETTI: Yeah, because, I mean, in 9 some cases, it's a normal operating issue, and in 10 another case, it's an accident issue --
11 MR. DRZEWIECKI: Okay.
12 MEMBER PETTI: -- when you just talk about 13 that safety function at that high a level.
14 MR. DRZEWIECKI: Okay, okay, thank you so 15 much.
16 VICE CHAIR REMPE: But I would also like 17 to see something in what your current discussion is of 18 2.2.3 where you talk about Reg Guide 1.233, and 19 although Part 53 is not a done deal yet, I think that 20 a paragraph there talking about what's being thought 21 about and the acknowledgement that there's a different 22 hierarchy would be helpful.
23 Because you see the same problem occurring 24 with this NUREG/CR Oak Ridge report where they only 25 refer to 1.233, and they did talk a little bit about 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 1 some interactions, but I think if you're going to be 2 going through and using this for all these different 3 fuel types, this is the place to start putting it as 4 a first place, okay?
5 MR. DRZEWIECKI: Absolutely, okay, yeah, 6 so I have an idea of what I would do there and I think 7 it would really be largely to expand that discussion 8 on chemical attack to really in the, you know, 9 evaluation model framework, and also add language into 10 these other sections to make it clear that it's 11 discussed there, but I'll have to see, you know, what 12 it all looks like, but, yeah, I have these notes.
13 VICE CHAIR REMPE: Although I guess Dave 14 and I are now in concurrence on this suggestion, we're 15 just two out of the whatever number of members that 16 will be helping with the letter today, so you should 17 probably just wait until the letter comes out and then 18 address it.
19 MR. DRZEWIECKI: Yeah, well, I mean, it 20 makes sense either way, so, okay.
21 MEMBER PETTI: Yeah, because Tim, at least 22 in the draft, I've got a number of just really minor 23 ones, but I've got to go back because I think you may 24 have addressed actually some of them in the public 25 comments, so.
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33 1 MR. DRZEWIECKI: Okay.
2 MEMBER PETTI: The final letter, you know, 3 we'll try to capture things that we think should be 4 changed or comments that should be addressed in the 5 letter.
6 MR. DRZEWIECKI: Okay, sounds good, okay, 7 okay. So, could we just go to -- okay, so, all right, 8 so where we left off, I had gone through this Goal 2.1 9 and how that was broken down, and so I'm not going to 10 go into much more detail on the framework here. Could 11 I go to the next slide, please, slide 11? I'm sorry, 12 may I have --
13 MR. HOELLMAN: Are you seeing it okay, 14 Tim?
15 MR. DRZEWIECKI: I am seeing slide 10 16 right now, yeah. I want to get slide 11.
17 MR. HOELLMAN: Well --
18 MR. DRZEWIECKI: Oh, there is it.
19 MR. HOELLMAN: -- I guess on my screen, 20 I'm seeing slide 11.
21 (Simultaneous speaking.)
22 MR. DRZEWIECKI: Okay, all right, so these 23 tables are in -- this is at the end of the NUREG 24 Appendix A, and this is the list of all the goals in 25 the framework, and so, it comes out to be just over 60 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
34 1 if you had, you know, to address everything in there.
2 Just again, you know, the goal is to, the 3 intent is to make findings on all the gray boxes with 4 the understanding that, you know, if you satisfy 5 those, you can satisfy higher level goals and so on 6 and so forth. So, okay, next slide, please?
7 MEMBER MARCH-LEUBA: Hey, Tim, don't --
8 can we go back to 11?
9 MR. DRZEWIECKI: Yeah, yeah, sure.
10 MEMBER MARCH-LEUBA: This is Jose March-11 Leuba. I love this Appendix A because it's a very 12 concise summary of the whole methodology and you can 13 see everything in one, I mean, in a single slide, so 14 this is really good.
15 So, one thing I see missing here at this 16 high level is the burnup limit, which is typically, 17 when one thinks about fuel qualification, is up to 18 which burnup limit is your fuel good?
19 So, if you were -- I don't know. I would 20 have liked to see here either a test envelope or 21 burnup limit somewhere, just as a comment.
22 I'm going back to Section 3.4.2 where it 23 talks about the testing envelope. You have a 24 paragraph in which you guys mention the extended use 25 of lead test specimens. Could you amplify on that 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 1 concept?
2 MR. DRZEWIECKI: I can to an extent 3 because, okay, so I do want to address the first 4 comment first in terms of a burnup limit, and I think 5 that if you look here and you look at Goal 2.1.1, and 6 that shows up actually in two spots, that is where we 7 include the burnup limit. That's where it would be.
8 So, and that's going to inform, you know, 9 where you're going to need, you know -- okay, so 10 actually that's going to inform where you need an 11 evaluation model, and the validation of that model is 12 going to inform where you need your data, and that 13 includes your burnup data.
14 The expanded use of lead test specimens, 15 what we're talking about there is generally in a light 16 water reactor, that's being governed by what you have 17 in your technical specifications, and you normally can 18 only put, you know, like your LTAs, only just lead 19 test assemblies, only a few of them in a few spots.
20 We do recognize that getting integral data 21 for these non-LWRs can be a challenge, and so we don't 22 necessarily have the exact answer right now, but we've 23 put forth a couple of things.
24 Ultimately, we think that we can be more 25 flexible with the lead test specimen or lead test 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 1 assembly program with non-LWRs than we have been 2 traditionally with the light water reactor fleet, 3 provided that you have a safety analysis that shows 4 that it's okay.
5 And we also included some examples of 6 performance-based approaches that can help with that, 7 things like -- the example that we gave was gas 8 tagging such that you would get some kind of early 9 indication if you saw a problem in your fuel, but 10 things like that.
11 So, we can't have a generic solution. I 12 just wanted to highlight that we are trying to be 13 open-minded about what we can do with the lead test 14 specimen program in order to provide the flexibility 15 that we need.
16 One other idea is possibly to have, you 17 know, perhaps load a reactor with, you know, some fuel 18 that maybe it was pre-burned in, you know, a test 19 reactor or somewhere else, and then, you know, and 20 then to monitor that.
21 These are just ideas, but to have a 22 specific -- you know, that whole idea is not fleshed 23 out though.
24 MEMBER MARCH-LEUBA: So, basically this is 25 yet to be determined? That's basically what you're 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 1 saying?
2 MR. DRZEWIECKI: Yes, yes, I mean, I'll 3 say yeah. We don't have an answer, but we do want to 4 be flexible, yeah.
5 MEMBER MARCH-LEUBA: Yeah, because that 6 data, I mean, if you wanted to go to high burnup, it's 7 difficult, and expensive, and time consuming, so.
8 MR. DRZEWIECKI: True.
9 MEMBER MARCH-LEUBA: This makes sense.
10 Okay, thank you.
11 MR. DRZEWIECKI: Yeah, sure, okay. Okay, 12 next slide, please? Oh, Dr. March-Leuba, your hand is 13 still up unless you had any more comments. Anyway, 14 okay, so now --
15 MEMBER MARCH-LEUBA: It's no longer up.
16 MR. DRZEWIECKI: Okay, thanks. Okay, all 17 right, so now I'll go, yeah, all right, so I'll go to 18 potential comments as well as discuss our next steps.
19 So, we received, you know, over 40 20 comments or about there, and so what I'm going to 21 highlight here are these 13. I just kind of 22 paraphrased them or just gave them a title.
23 The ones that are here in bold, as we get 24 to them, there will be a star on that slide. It's 25 ones that I thought were a little more significant 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 1 either due to activity that we're doing or due to our 2 engagement with industry there, so I will flag them 3 when I get to them. So, next slide, please?
4 Okay, as I go through these slides, I was 5 going to try just to paraphrase what the comment was 6 and then go on to staff's response. If you want me to 7 change my style of whether to read the comment 8 completely or to pause so that you can read the 9 comment, just let me know so I can adjust as we go.
10 But as far as this first comment, and we 11 got several in this area, it, you know, seemed to 12 indicate -- so, it stated that this NUREG appears to 13 be based on LWR fuel, traditional LWR fuel, and it 14 asked for examples in terms of, you now, in terms of 15 our criteria in terms of how that could be satisfied 16 for non-LWR fuels.
17 And so, we do acknowledge that this NUREG 18 is informed by our lessons learned from experience 19 with LWR fuel, but we disagree that it's actually 20 based on LWR fuel designs.
21 We did try to be as flexible and 22 technology neutral as possible, but, you know, we have 23 experience in LWR fuel and that made its way into 24 here.
25 The scope does state, you know, the 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 1 criteria also draws from advanced reactor fuel testing 2 performed to date, as well as AFQ considerations or 3 auxiliary fuel qualification considerations.
4 As Jordan has mentioned, we do have 5 contracts placed and we are working both with Idaho 6 National Laboratory and with Pacific Northwest 7 National Laboratory to do a generic assessment of 8 metal fuel and for TRISO fuel.
9 And I want to state that that work has two 10 purposes, one to give us a generic assessment of those 11 fuel types and the second is to actually look at this 12 framework to see, you know, where are our 13 shortcomings. Are there things in there that need to 14 be expanded upon? Are there goals that are extraneous 15 and things like that?
16 One last point I wanted to make on this 17 slide is the fact that we have just signed, the U.S.
18 NRC has signed an agreement with the Canadian Nuclear 19 Safety Commission to do a joint assessment on TRISO 20 fuel, so that's going to overlap with this work with 21 PNNL.
22 So, we're going to try to write a joint 23 report in the next 18 months with interim reports 24 coming out approximately every quarter to highlight 25 our progress, and that work is being supported by this 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 1 contract with PNNL. Next slide, please?
2 Okay, this next comment had to do with the 3 role of research literature, and in our draft NUREG 4 and, in fact, in our previous versions of this report, 5 it had started off with a quote from a 2007 Journal of 6 Nuclear Materials paper that had pretty much stated 7 what the objective of fuel qualification was.
8 And it seemed like that gave the wrong 9 impression to industry in the sense that some 10 commenters thought that we were using it as a more 11 regulatory basis for fuel qualification.
12 So, we disagree with the characterization 13 that a technical paper served as the primary basis for 14 this NUREG, but we do acknowledge that, you know, that 15 that work did have an impact on our judgment of what 16 to use as a definition for qualified fuel.
17 But ultimately, we thought that that 18 definition of qualified fuel that we use accurately 19 reflected, you know, what the regulatory requirements 20 are, as well as what we've learned from our 21 experience, you know, from light water reactor fuels 22 and advanced reactor fuel testing.
23 MEMBER PETTI: So, Tim?
24 MR. DRZEWIECKI: Yes?
25 MEMBER PETTI: Are you done on that?
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41 1 MR. DRZEWIECKI: I'm done. Well, just 2 wanted -- yeah, I mean, I can. I just wanted to say 3 that, you know, we did make changes to better 4 characterize the role of that paper, so we effectively 5 rewrote Section 1.1, which is the purpose, but that's 6 it.
7 MEMBER PETTI: Yeah, so I look at this 8 comment and it seems contradictory to the previous 9 comment. The previous comment says you guys did this 10 all from an LWR mindset, and then you pick a paper 11 that it's all advanced reactor based, and the comment 12 is no, that shouldn't be used either, and so I 13 chuckled.
14 The other thing is, I mean, just as a 15 point of comment as an author of the Crawford paper, 16 those guys came to me and said let's write this paper, 17 and independently, we had the same set, the same 18 approach.
19 So, the gas reactor community had an 20 approach, the fast reactor community had an approach, 21 and there's a light water reactor approach. These 22 things, you know, I mean, they are amazingly similar, 23 and what I like about this NUREG is that it kind of, 24 you know, puts it all in a framework.
25 This idea that things are different, I 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 1 don't necessarily agree with when you get to these 2 higher levels, that papers like this could be written 3 and you can pull out the technology neutral 4 requirements if you will. So, I just chuckled when I 5 read these comments. Thanks.
6 MR. DRZEWIECKI: Thank you for that.
7 Okay, so then with that, I'll go onto the next slide 8 unless there are any more comments.
9 Okay, this comment was associated with the 10 actual regulatory basis, and the one thing I do want 11 to highlight is that this comment was made associated 12 with the section that was, I believe, on purpose or 13 scope, but it was on the very first page.
14 And the comment was that fuel 15 qualification itself is not required for any of the 16 mentioned licensing approvals, which is design certs, 17 combined licenses, manufacturing, or standard design 18 approvals, also operation license should be there too.
19 And our response to that is that, you 20 know, we do recognize the term fuel qualification is 21 not explicitly defined or used in NRC regulations.
22 However, you know, there are regulatory 23 requirements generally applicable to licensing that 24 are generally associated with nuclear fuel behavior 25 and its role in preventing the release of radioactive 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 1 material under conditions of normal operations, AOOs, 2 and accident conditions.
3 We felt as though those ties between the 4 regulations and this framework, that that was 5 described in the section on the reg basis, so we 6 didn't make changes based on this comment.
7 We also highlighted the fact that, yes, 8 this is guidance, and so, you know, you're not 9 required to follow it. Can I have the next slide, 10 please?
11 Okay, this is just a small change in 12 wording, and so in our scope statement, we had used 13 the term that this is focused on fuel failure and 14 damage mechanisms due to irradiation, and the 15 commenter just pointed out that, you know, irradiation 16 isn't the only thing that we're worried about.
17 So, we've approached this change from due 18 to irradiation to due to irradiation and irradiation-19 assisted phenomena. We agree, you know, that there 20 are degradation mechanisms beyond irradiation.
21 However, we think the primary obstacle of 22 qualifying fuel has generally been showing fuel 23 performance at the desired exposure, and most fuel 24 degradation phenomena are impacted by irradiation, and 25 I would highlight the ones cited by the commenter 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 1 generally are impacted by irradiation.
2 MEMBER BALLINGER: This is Ron Ballinger.
3 I think it actually should be expanded further, 4 primarily because for some of these fuels, and some of 5 these environments, the radiation is irrelevant.
6 MR. DRZEWIECKI: Can you clarify?
7 MEMBER BALLINGER: Well, you know, some of 8 these molten salt fuels, for example, or molten salt 9 cooled systems. It's possible that there can be 10 corrosion related degradation that is irrespective of 11 the presence of radiation.
12 And, what do you think, Dave?
13 MEMBER PETTI: Yes, you know, as I read 14 it, I kept thinking of more environmental degradation.
15 I mean hydrogen pickup for instance, is not due to 16 radiation. I mean it is because the hydrogen comes 17 from radiolysis of the water.
18 MEMBER BALLINGER: Right.
19 MEMBER PETTI: But, you know, you can put 20 it, you know you can just put it in a hydrogen 21 atmosphere and it's going got pick it up.
22 So, something about more of the 23 environment, the environment might more capture a 24 comment better. Or might more address the comment 25 better.
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45 1 MEMBER BALLINGER: We need to avoid 2 constructing a box that somebody will, like an idiot 3 savant, adhere to it.
4 MR. DRZEWIECKI: Okay, let me look at my 5 note here. All right.
6 MEMBER KIRCHNER: Take for example, 7 corrosion in LWRs. I mean, that's it may be enhanced 8 by a radiation, but in general, it's more of a water 9 quality issue than control.
10 And, so the, as Dave said, the idea of the 11 environment might be a more expansive way to look at, 12 to pick up these other mechanisms that are mentioned 13 in the comment.
14 MR. DRZEWIECKI: Okay, all right. Okay, 15 I took that note. That makes sense.
16 Okay, thanks, Ron.
17 Next slide, please.
18 MEMBER BALLINGER: By the way, I mean, I 19 think that the table in Appendix, I guess A, when it 20 talks about degradation, it covers pretty much 21 everything in general. But comments by members 22 suggesting that there should be examples is a very 23 good one.
24 MR. DRZEWIECKI: Okay, thanks.
25 Okay, can I get slide 18, please?
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46 1 Okay, so this one we'll start because we 2 saw that this was a significant topic. And, what this 3 comment was really after is basically stating that the 4 general of design criteria, and the advance, design 5 criteria, or the GDCs and ARDCs, that they're not 6 requirements for non-LWRs.
7 And, that, you know, you can develop the 8 principle design criteria, which are requirements by 9 some other method.
10 And, so they were requesting an update to 11 basically show that, you know, it may not be necessary 12 to meet these requirements if fuel is not relied upon 13 as a safety feature.
14 So, we did --
15 (Simultaneous speaking.)
16 MEMBER PETTI: So, could you, do you have 17 a little more insight in that comment? I mean, were 18 they specifically thinking about salt systems?
19 Because I mean, if the fuel is in a safety 20 feature, do you have to assume all the fission 21 products are in the coolant? I mean, it doesn't, I 22 don't understand. That doesn't make technical sense 23 to me.
24 MR. DRZEWIECKI: Yes, so I will say on the 25 next three slides we kind of, you know, we kind of 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 1 touch on this because we think by the very nature that 2 it's fuel, it's going to have an impact on what 3 opposite of the fundamental safety functions of heat 4 removal, reactivity control, and, you know, 5 confinement of radioactive material.
6 So, we will hit on those.
7 So, in terms of the context, I can't say 8 I know exactly where they were coming from. I don't 9 believe that they were talking about molten salt 10 reactors. That I'm not sure about.
11 But, I just thought maybe it was, you 12 know, related to perhaps maybe they don't think that 13 they credited explicitly. But I'm not sure.
14 MEMBER KIRCHNER: Well, it's hard to 15 imagine any advanced reactor that doesn't rely on the 16 fuel form as a safety feature. I'm perplexed by where 17 NEI is going with this.
18 Not to personalize it, but can someone if 19 we put the liquid fuel reactors out of the discussion 20 for the moment and just think about fixed fuel, it's 21 hard to imagine the fuel not having a safety function.
22 It's just I'm.
23 MEMBER PETTI: Well, in fact, Walt, the 24 entire framework is built from you know, what are your 25 safety functions, and how does the fuel influence 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 1 those safety functions?
2 So, yes, it may not be explicit, but it's 3 certainly implicit.
4 (No audible response.)
5 MEMBER PETTI: And, even the salt stuff 6 that we'll hear about later. I mean that's how they 7 start.
8 So, you know, again, I find the comment 9 odd as well, Walt.
10 MR. DRZEWIECKI: So --
11 (Simultaneous speaking.)
12 MEMBER KIRCHNER: It's like I can't, well, 13 I don't want to personalize it. I just, this one more 14 time we see this oh well, the GDCs aren't requirements 15 for non-LWRs, and I don't know where the logic train 16 is going on this.
17 It seems to me that the fuel is always 18 going to have as you said, an implicit safety 19 function, unless they're not going to take any credit 20 for the fuel operating. Which is just not credible 21 approach to a reactor design.
22 So, this is baffling.
23 MR. DRZEWIECKI: So, I mean, yes. So, I 24 don't want to read too much into this, but you know, 25 we did work with our policy branch, and with the 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
49 1 Office of General Counsel, and we do agree that you 2 know, as far as the GDCs and ARDCs are not necessarily 3 requirements for non-LWRs but are instead, considered 4 guidance for non-LWRs in the development of the 5 principle of design criteria, which again, are 6 requirements.
7 However, the ones cited in this NUREG, 8 they are associated with safety functions that 9 generally involve fuel. And furthermore, those safety 10 functions are not otherwise captured in NRC 11 regulations. And, that's things like fuel design 12 limits, maintaining the coolable geometry.
13 And, we do expect that those safety 14 functions would be addressed as part of a fuel 15 qualification.
16 And, so we did make changes to this 17 section in order to accurately reflect the 18 requirements on the associated PDC. But, you know, we 19 do still have them cited.
20 Because I can say that there are certainly 21 some GDCs and ARDCs that have regulatory requirements 22 in other areas, in Part 50. But ones associated with 23 the fuel generally don't.
24 These are captured by the GDC and ARDC and 25 we think that they should be addressed.
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50 1 Next slide, please.
2 Okay, so this is going, okay so this 3 comment is going to go back of the fundamental safety 4 functions that we had discussed earlier.
5 So, this is the section 2.2.3, which is 6 the reference to Reg Guide 1.233, or you know, which 7 endorses NEI 18.04, which is licensee modernization 8 project.
9 And, you know, and this goes back to you 10 know, please clarify the role of fuel qualification as 11 is necessary only if being relied up and/or credited 12 in the safety analysis, some designs may not.
13 So, our response to that was you know, we 14 do recognize that the role of the fuel and the 15 protection against the release of radioactivity, that 16 can vary based on the reactor design. I think one 17 thing, you know, for example, if you compare 18 traditional LWR fuel say to TRISO fuel, how you have 19 some of the barriers in the fuel itself in TRISO fuel, 20 that obviously has an impact.
21 But at the same time, we did make an 22 update to this section in order to clarify that 23 nuclear fuel by the very nature that it's fuel, it 24 contributes to the reactivity balance. There's a 25 source of heat generation and fission products.
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51 1 Therefore, fuel is generally recognized as 2 impacting the fundamental safety functions of 3 reactivity control, heat removal, and confinement of 4 radioactive material.
5 Could I have the next slide, please?
6 Okay, so this is a section that was added 7 and as we discussed before as far as you know, trying 8 to have an expanded use the lead test specimen 9 program. The commentor here had highlighted that that 10 only helps if we you know, have reactors that are 11 operating. So, what are the other alternatives?
12 And, so we added this section first core 13 applications, to try and address this comment. And, 14 what it goes after, these are the high points in terms 15 of the requirement 50.43(E), which means that you, you 16 know, have to demonstrate what that the safety 17 features of your plant in order to get a license.
18 We think that that applies generally 19 because of fuel impacting the functions of your 20 activity control heat removal and confinement 21 radioactive material.
22 Data may be obtained from test reactors.
23 We gave some examples there, ATR, TREAT, provided that 24 you can show you know, if the associated data are 25 appropriate for assessing your evaluation models.
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52 1 And, where I'm going to there is that we 2 have that assessment framework for data and some of 3 those, one of those criteria are you know, is test 4 distortions. Can you justify that that test data 5 represents your actual prototypical environment?
6 Just at the comment again that we do 7 accommodate the use of elite test specimen program 8 beyond what has been used traditionally.
9 However, if we can't make, if it was 10 findings that we have of that data, which is you know, 11 50.43(E)(1), then there is the option to do a 12 prototype plant. And, we have separate guidance for 13 that.
14 MEMBER PETTI: So Tim, what I was 15 confused. I always think of LTAs as when one has 16 let's call it evolutionary fuel design. So, you've 17 got to sort of a database out there. I changed some 18 things, I do an LTA, I mean that's what largely many 19 of the accident tolerant fuel concepts are. And, that 20 kind of makes sense to me. Even allowing expanded 21 use.
22 But I'm worried about does this comment 23 mean that potentially, a fuel that has never seen any 24 irradiation, the first time it will be is when you 25 build the reactor and that somehow, reactor's a lead 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 1 test assembly?
2 I mean that's not what you're proposing 3 could be the case? You still need some data before 4 the reactor is built, right?
5 MR. DRZEWIECKI: That is true, yes. We 6 need enough data to show, or to have confidence, that 7 you know, you can assess evaluation models. So, that 8 we have confidence in that.
9 And, the thought of the expanded LTA 10 program would still require a safety analysis to show 11 that you're still safe.
12 If you have no data at all, and you know, 13 if you're first plant is going to be your first use of 14 that fuel, that would fall under the category of the 15 prototype plant.
16 And, you know, we haven't done that to 17 date, but we have guidance on how that could be done.
18 And, that may you know, require other limitations 19 perhaps on citing, or you know, of other safety 20 features of that plant. Can't say exactly what it 21 would be, but I can say it's allowed under the 22 provisions of the prototype plant.
23 MEMBER PETTI: Okay.
24 MEMBER BROWN: Can I ask a question 25 relative to Dave's comment?
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54 1 MR. DRZEWIECKI: Yes.
2 MEMBER BROWN: In terms of the 3 qualification if you don't have any data, I'm just 4 harkening back to the very early days of the Naval 5 Nuclear Program when we first built the prototypes.
6 And, obviously there was no data in terms 7 of any type of plant when we were building the initial 8 cores. For instance, the first Nautilus core 9 prototype, et cetera.
10 But those cores were short lived relative 11 to what the anticipation is, at least in some of the 12 discussions that have been had for these advanced 13 reactors. And, we're talking a year and a half, maybe 14 a year. Now, they might have lasted longer, but we 15 had, we started accumulating data in that manner.
16 And even then when we first there was 17 several years worth of I'm not a metallurgist, but 18 there as I was taught when I got there in '65, they 19 had a number of laboratory tests where they set stuff 20 up and saw what its behavior might be like.
21 But yet they didn't have a reactor that 22 lasted very long. We took the cores out, and we built 23 the cores even in the operating plant like that with 24 removable assemblies so we could examine the fuel 25 periodically during its light off.
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55 1 Is there anything in this that tries to 2 prescribe, not prescribe, that's the wrong word, 3 identify how a program ought to be laid out to get 4 this fuel data before somebody makes a commitment, or 5 tries to say hey, we're going to go in this direction?
6 MR. DRZEWIECKI: Not in this guidance. We 7 don't have that specifically. So, but I believe what 8 you're talking about.
9 So it sounded like what you were saying is 10 that you had effectively lead test specimens that 11 would be taken out, such that you could ensure that 12 your actual plant was always lagging behind your test 13 data?
14 MEMBER BROWN: Exactly. Yes --
15 (Simultaneous speaking.)
16 MR. DRZEWIECKI: Okay.
17 MEMBER BROWN: -- there was an S1W 18 prototype for the Nautilus.
19 MR. DRZEWIECKI: Okay.
20 MEMBER BROWN: And, there were samples in 21 ports that we went in, and we pulled those samples out 22 periodically to determine how was it degrading? What 23 was, but they look like the fuel that was being, you 24 know, being used to generate the power.
25 MR. DRZEWIECKI: Uh huh.
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56 1 MEMBER BROWN: And, that seems, in all of 2 these advance reactor applications that we've been 3 talking about, I haven't heard anything relative to 4 how we get these initial swatches of data.
5 And, it would seem to me that it would be 6 up to the regulator, or somebody like you, you guys.
7 Because the vendors are going to take advantage of 8 every step they can avoid. I mean it just costs a lot 9 of money.
10 And, you know, the development of the 11 fuels for the Naval Nuclear Program were, took a lot 12 of time to develop that confidence that they would 13 last, and last, and last.
14 It seems someplace you got to start 15 talking about that.
16 MR. DRZEWIECKI: Yes. I mean --
17 MEMBER BROWN: And, this seemed like a 18 good place to do it, but.
19 MEMBER PETTI: So Tim, you know, the 20 concern that I have in all of these is, we are almost 21 perfect in thinking the fuel is going to be great.
22 You know, they did not know about void 23 swelling in the stainless steel clad until after it 24 was actually working, you know, and fuel was in the 25 reactor.
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57 1 They didn't know about clad creep-down in 2 early light water reactors cores. There's in all the 3 fuel systems, there are things that they just didn't 4 see.
5 And, this I don't, I think people who 6 develop fuel understand that, and understand how 7 sobering that is when you have to think about how to 8 develop, you know, and qualify a fuel.
9 But I think there's other people who just 10 think yes, this looks good so let's just put it in the 11 reactor and get going.
12 That's not the history of fuel development 13 across all reactor concepts. There's no reactor 14 concept that hasn't had a mistake that's forced them 15 to go in the wrong direction, you know, go backwards 16 instead of forwards in terms of fuel development.
17 So again, I just worry about the sort of 18 what's behind the comments. They seem to not 19 appreciate what it really takes.
20 MR. DRZEWIECKI: Yes, yes.
21 MEMBER BALLINGER: This is Ron again.
22 I'll give you an example of what happened 23 with Phenix where they literally had to at some point, 24 because of the swelling, shut the reactor down and go 25 in and rotate the fuel because the fuel handling 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 1 machine was programmed to go to position X and the 2 handle on the fuel was at position Y, which was a 3 problem.
4 But I look at this section as very 5 important, primarily because prototype reactors while 6 maybe necessary, are extremely expensive and it takes 7 a long time. The advances in modeling and simulation 8 have been pretty extensive over the last who knows how 9 many years, decades?
10 And, so being able to extend, put that in 11 quotes I guess, the range of usefulness of data 12 combined with modeling and simulation, I think that's 13 where they're coming from here.
14 And, I think that's going to be a bone of 15 contention forever because most of us beyond the age 16 of 50 are, and have spent time in the Navy, know what 17 prototypes are required for. And, know about the bad 18 experience ruining cores and things like that.
19 So, this is a very important comment 20 because I think they're trying to allow for the use of 21 modeling and simulation to compensate and avoid, if 22 necessary, a full blown prototype plant, which is, 23 which would foreclose, pretty much foreclose on 24 building any of these things. It's just too darned 25 expensive.
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59 1 MR. DRZEWIECKI: Yes. I do want to 2 highlight, and I don't want to get sidetracked, but I 3 do want to highlight that there have been some 4 discussions, especially with the AFQ community and 5 then, you know, in looking at the general atomics AFQ 6 white paper.
7 That there has been some consideration of 8 these accelerated fission testing test techniques, 9 things like the mini fuel fission acceleration steady-10 state testing. And I think that there's been some 11 consideration in trying to use those.
12 I will state that I don't think that that, 13 at least we haven't seen data to show that that is 14 representative of something that is prototypical, or 15 that there could be some kind of distortions from that 16 data.
17 And, so we are still in a spot where we 18 are seeking integral data to support validation, 19 unless it can be otherwise justified.
20 We haven't seen justification to date --
21 (Simultaneous speaking.)
22 MEMBER BALLINGER: Yes, I mean there may 23 be a need to make a distinction between being sure 24 that the fuel, and Dave probably knows this much, I'm 25 sure knows it much better than I, where the fuel, fuel 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 1 issues that might compromise safety, might be 2 different from fuel issues that just make the thing 3 uneconomical.
4 In other words, not a safety related 5 problem, but just an oversight which invalidates the 6 use of fuel from an economic point of view.
7 MR. DRZEWIECKI: Okay.
8 MEMBER BROWN: Can I make, this is Charlie 9 Brown again.
10 Just to springboard off of Dave's again 11 another earlier comment about how you learn.
12 Why, in your all's mind, wouldn't you try 13 to develop some type of a program approach that the 14 vendors would be able to utilize to do this step-wise, 15 accumulate data, but you've identified what they have 16 to demonstrate, so that you have something to work 17 with as opposed to just, I mean I hate to admit it, 18 I'm not a great fan of depending on modeling this 19 early in any of the development programs because you 20 have no data to model with.
21 You're basing it on applications that 22 don't duplicate what you're designing. Or what they 23 are proposing to design.
24 And, it would seem to me that instead of 25 going after it full bore, you ought to lay out an 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 1 expected program.
2 And, there's a model for that that was 3 used for light waters. I'm not saying it has to be as 4 long, or anything like that. I'm not trying to go 5 backwards if that's the case, because we do know a lot 6 more now.
7 But it seems to me making sure there's a 8 program to put fuels in place and it's going to take 9 some time, should be under the purview of the NRC to 10 try to lay out and make sure you all know it's safe.
11 And, it seems this, I don't know where you 12 do that, whether it's in this document or an 13 associated document of some kind.
14 That's just a thought process, that's all.
15 I don't know whether I'm off base, Dave.
16 It just seems to me that in all the conversations 17 we've had, this is the first time I've heard this 18 really discussed in any detail. So.
19 MEMBER PETTI: So, my view Charlie, is 20 that again this document is a what document, not a how 21 document, which is very typical, right? We run into 22 this from lots of other venues. So, this is the first 23 step.
24 But I think it's difficult to talk about 25 how across the different fuel systems. They all end 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 1 up implementing things differently.
2 And, frankly when you look at the two 3 cases they're looking at, metal fuel and TRISO fuel, 4 they're very mature. You know, we've had both those 5 types of reactors operating.
6 So, it's just very, very different when 7 you're looking at that than taking you know, a brand 8 new, I've got this really brand new fuel idea and I've 9 got to mature that. That's a very different thing.
10 And, that's where it takes a lot of time 11 is if it's a brand new fuel.
12 MEMBER BROWN: I understand the TRISO 13 thing. I'm not trying to throw a wet blanket. But 14 you know, the molten fuels, is there a wide 15 application of those molten fuels?
16 MEMBER PETTI: Yes, no, again, I didn't 17 talk about the liquid fuel though.
18 MEMBER BROWN: I mean, well, that's --
19 (Simultaneous speaking.)
20 MEMBER PETTI: Just talking about the 21 solid fuels, so.
22 We'll hear about that this afternoon.
23 MEMBER BROWN: I know. All right. Thank 24 you.
25 MEMBER PETTI: Okay, let's keep going here 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
63 1 so we don't fall too far behind, Tim.
2 MR. DRZEWIECKI: All right, okay.
3 May I have slide 21?
4 Okay, this one I'll go through pretty 5 quickly. This is just you know, this is a comment 6 basically just you know, should we note in the text 7 that TRISO is you know, is an example of fuel that has 8 insensitivity to manufacturing process.
9 We didn't necessarily want to go that far 10 but you know, we did make comments. We did make edits 11 to this NUREG to reflect, which actually in the EPRI 12 TRISO topical report, and the associated safety 13 evaluation, which you know, kind of highlighted key 14 and state parameters that have to be controlled.
15 So, that's all we did with that comment.
16 MEMBER KIRCHNER: Tim, this is Walt.
17 MR. DRZEWIECKI: Yes.
18 MEMBER KIRCHNER: This one, I just want to 19 make an observation.
20 Yes, we have a TRISO report that's been 21 reviewed from EPRI, that provides for specifications 22 and such. But this comment insensitivity to 23 manufacturing processes? It's the manufacturing of 24 the TRISO fuel that is everything.
25 So, that means you need a quality 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 1 assurance program that guarantees that you follow the 2 spec. So, I, this one I just, I don't understand.
3 It's extraordinarily important to have a 4 QA program when you manufacture this TRISO fuel, so 5 that you guarantee you stay within this spec and 6 therefore, can avail yourself of all the past work 7 that's been done by the labs and the DOE.
8 So, it raises a question in my mind: where 9 does QA fit into this equation for this, for this 10 NUREG?
11 MR. DRZEWIECKI: Well, okay, so --
12 MEMBER KIRCHNER: How are you addressing 13 QA? Because it's if you're not doing something 14 equivalent to NQA-1, and when you're running your 15 manufacturing of TRISO fuel, I'm at a loss how you 16 guarantee this insensitivity to manufacturing 17 processes.
18 MEMBER BALLINGER: Yes, this is Ron.
19 This thing got me laughing, too, because 20 they're guaranteeing that it's insensitive to the 21 manufacturing process by doing this huge program, to 22 find out all the parameters that you have to adhere to 23 so that you can make a proper fuel.
24 So, of course its insensitivity to the 25 manufacturing process after they've guaranteed that if 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 1 you manufacture it, it's insensitive to that 2 manufacturing process.
3 MEMBER PETTI: It's a really poor choice 4 of words, I believe. Because it doesn't exactly say, 5 it's not very precise in terms of what, you know, 6 what's important.
7 MR. DRZEWIECKI: So, I get to the point as 8 far as you know, how does QA fit in to this. It is 9 called out explicitly. In fact, I'll have a slide on 10 it in terms of you know, the actual test program. We 11 do expect there to be you know, a QA program there.
12 It doesn't necessarily have to be NQA-1 13 but you know, we do want our test program there.
14 And, but other than that, in terms of 15 manufacturing, we did not call out that that has to be 16 done. We understand that that's implied. We think 17 that that's covered by you know, other rules that 18 should apply to the whole facility.
19 So, we didn't call it out explicitly here.
20 MR. LYNCH: One thing I'll add, this is 21 Steve Lynch again with the NRC.
22 As far as quality assurance goes, this is 23 something that's been important that we have talked to 24 with perspective applicants as they consider 25 demonstrating the adequacy of fuel, especially at a 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
66 1 maybe small scale testing facilities. Or even just 2 collecting data in non-nuclear facilities, that they 3 need to think about what their end licensing goal is.
4 And, if they are looking at eventually 5 licensing a nuclear power plant, they need to make 6 sure that the data that they collect is done so under 7 a quality assurance program that is going to 8 ultimately meet the NRC's regulations.
9 Now, for example, using NQA-1 and 10 satisfying the requirements in 10 CFR Part 50, 11 Appendix B.
12 So, that is a message that we communicate 13 for any sort of data that is being collected, is for 14 these perspective applicants to think about their 15 long-term licensing goals to ensure the quality of the 16 data that they collect.
17 MEMBER KIRCHNER: Well, it's just not the 18 data, is the actual manufacturing process.
19 So, we skipped over that left hand side of 20 the original chart, but as a person who did this, I 21 actually bought fuel under contract, TRISO fuel.
22 This is the, I can't, you have to be able 23 to demonstrate that the batches of fuel that you make 24 meets the spec.
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67 1 and control. And I just, this, I find this thing 2 baffling, this whole comment.
3 But it does raise the issue in my mind 4 that you have to have a very, if it's not NQA-1, then 5 I'd like to know what the other QA program is that's 6 substituting, if you're going to make batches of TRISO 7 fuel and put it in a reactor.
8 So I'm not talking about test data 9 anymore. We already have a lot from Idaho. I think 10 that was done under a good program, so I think the 11 resulting specs that are in the EPRI report based on 12 that program, are sound. Those have been reviewed by 13 you, we've had a chance to look at that.
14 But now going forward with an actual 15 application, you've got to make this TRISO fuel under 16 a, under a quality assurance and control program that 17 is really tidy.
18 And, otherwise, you're not going to have 19 competence that the actual product that goes into this 20 first reactor meets the spec.
21 MR. DRZEWIECKI: Agree completely, and 22 just speaking anecdotally from some of the recent 23 experience we've had from some facilities under 24 construction and doing procurement of manufactured 25 items.
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68 1 And, there is an expectation as part of 2 our inspection process that the QA programs that a 3 licensee establishes, that are acceptable to the NRC, 4 are being applied to any sort of contractor that is 5 manufacturing or providing materials that will go into 6 a licensed facility. So, that is an expectation we 7 have, too.
8 So, agree completely that having all of 9 this manufactured under a robust quality assurance 10 program is important, and is something that the NRC 11 staff will look for.
12 MEMBER KIRCHNER: I'll repeat myself.
13 It's not just important, it's critical because in the 14 case of using TRISO fuel, we're using it as the 15 functional containment.
16 So, this is absolutely essential. It's 17 not important, it's essential. I've been there; trust 18 me.
19 I'll stop.
20 MR. DRZEWIECKI: Thanks.
21 Okay, so I got a few more comments to get 22 through so if I can go to the next slide, please, 23 slide 22.
24 This one, we also flagged as important.
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69 1 this did not result in any changes, but we do want to 2 explain ourselves here.
3 But the comment was that should we have a 4 goal in the structure that pretty much says that you 5 have to show that you can get to a safe shut down, 6 subcritical.
7 And, the comment was that not all reactors 8 must be subcritical to be safe, and therefore, it is 9 not necessary for all fuel types to be subcritical, 10 and the industry wanted to see a change from safe shut 11 down to a safe, stable end-state.
12 And, so first I'm going to explain where 13 we see where they're coming from, but also why we 14 disagree.
15 And, the first is that we have written 16 some recent policy papers, that have clarified that 17 maintaining subcriticality with only safety related 18 SSEs may not be required. This is SECY-18-0099.
19 This was the SECY that was associated with 20 the GDC 27 exemption in support of the new scale of 21 design certification application. And, so with that, 22 there was, you know, an exemption requested that was 23 needed.
24 So, there we did kind of lay out that it 25 may be okay to get to an accident condition that can 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
70 1 become recritical using only safety related equipment.
2 However, we do think it's important that you be able 3 to shut down some time.
4 And, that's where this goal is after.
5 And, so our statement is that staff 6 expects that nuclear fuel be designed such that forces 7 on the fuel, resulting from internal or external 8 events, will not preclude the eventual achievement of 9 a subcritical state.
10 So, we didn't make any changes based on 11 this comment.
12 MEMBER BROWN: How in the world can we, 13 what does that mean? Six months, a year? Three 14 months? My lifetime?
15 I mean that's, how in the world can we end 16 up with something so generic like doesn't have to be 17 subcritical to be safe?
18 We've probably been down this road a 19 little bit already, but isn't this like opening the 20 barn door and just telling all the horses to leave?
21 I mean this is, there is no limit on 22 anything. If you'd said something like a couple of 23 days, or an hour, maybe that would make some sense.
24 But when it's you're going to debate this 25 forever? It's unbelievable to me to sit there and 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
71 1 have a reactor be subcritical, I mean be critical, and 2 perking away and having a great old time no matter 3 what the cooling means is, for months.
4 And, that's what you're going to have to 5 fight to say no, you can't do that unless you 6 establish some requirements or goals before.
7 MR. DRZEWIECKI: Yes.
8 MEMBER BROWN: I just --
9 MR. DRZEWIECKI: We agree with you.
10 MEMBER BROWN: -- can't buy that. I 11 cannot buy that at all. I apologize. I'll be quiet.
12 I've said this before, so.
13 MEMBER MARCH-LEUBA: This is Jose. I 14 wanted to support Charlie on this one.
15 MR. DRZEWIECKI: Thanks.
16 MEMBER KIRCHNER: Well, this is an area 17 too, where Tim and your colleagues, are you working 18 with Bill Reckley and his colleagues, and comparing 19 notes on 10 CFR 53?
20 I'm going a little off topic here, but --
21 MR. DRZEWIECKI: Yes --
22 MEMBER KIRCHNER: -- I agree with your 23 statement here, but we're not necessarily seeing this 24 reflected in 10 CFR 53 drafts, particularly this 25 business about reactor subcritical. Control 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
72 1 reactivity. It's just essential.
2 So, I agree with Charlie and Jose that I 3 would not change this to some safe stable end-state.
4 That's too vague.
5 MR. DRZEWIECKI: Yes, I agree with you and 6 you know, it's my understanding that in Part 53, that 7 that was also going to be you know, a requirement that 8 you can get to a subcritical state.
9 It may not be necessary to do that with 10 safety related equipment, but that would be retained 11 as a requirement.
12 I can't, I don't know of specific language 13 that says that, but it's important to recognize you 14 know, Bill works in a policy branch. Jordan is in a 15 policy branch. So we are, you know, so they are 16 engaged in this NUREG, and they have actually helped 17 us address some of the comments. Especially the ones 18 on GDCs, ARDCs.
19 MEMBER BROWN: Walt, do you remember this 20 from the Part 53? I don't remember something that 21 insubstantial being part of the Part 53 discussions.
22 Either that or I've forgotten it.
23 I don't think I would have let that slide 24 by based on my past comments on that issue.
25 MEMBER BLEY: There was a discussion about 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
73 1 it, Charlie.
2 MEMBER BROWN: Pardon?
3 MEMBER BLEY: I don't think, Dave can help 4 me. I don't think we've seen specific language on 5 this yet, but we might have. I don't remember.
6 But I know what was just said is 7 essentially what we heard from the staff.
8 MEMBER BALLINGER: I mean I think the SECY 9 is all related to NuScale.
10 MR. DRZEWIECKI: That's right.
11 MEMBER KIRCHNER: Yes, I would not, the 12 SECY is an exemption for a specific design, not, well, 13 it's for the NRC to interpret, not myself, it's my 14 personal view. But the SECY is specific to NuScale 15 and an exemption to GDC 27.
16 But in our conversations with your 17 colleagues on this topic in a more generic sense, like 18 when the advance reactor design criteria were 19 presented, I thought we had assurances from the staff 20 that that would not, that the effect of GDC 27 would 21 be retained in the advance reactor design criteria.
22 MEMBER BROWN: Well, that's one of the 23 reasons we've been trying to make sure in Part 53 we 24 have some general design criteria. We've talked about 25 that and how expensive would that be.
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74 1 MR. DRZEWIECKI: Yes, so in terms of what 2 we have and you know, of ARDC 26, I don't want to, but 3 because yes, I was involved in that, and we did think 4 that the ability to get to a you know, safe, stable 5 state was actually safety related.
6 I don't recall if we required the ability 7 to get to a safe shut down, to get to a subcritical 8 state to be a safety related aspect of that.
9 But I would need to go back and verify.
10 MEMBER PETTI: So, I just think this is 11 somewhat of an aside, a different discussion. Let's 12 try to stay focused.
13 MR. DRZEWIECKI: Yes.
14 MEMBER PETTI: Because we should be in our 15 break time and we're not going to be able to go there, 16 we're going to keep pushing forward, I think.
17 MR. DRZEWIECKI: Okay, all right.
18 MEMBER PETTI: Keep going.
19 MR. DRZEWIECKI: Okay, may I have the next 20 slide, please?
21 Okay, all right, so this was a comment 22 just, you know, just trying to ask for specific 23 examples of what coolable geometry is.
24 And, so in the examples given here for 25 molten salt reactors.
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75 1 And, so in our section we do provide some 2 examples of what could cause a loss of coolable 3 geometry, which was derived largely from our 4 experience in light water reactors. But we didn't 5 feel comfortable providing criteria generically for 6 all fuel types.
7 And, so we didn't make any changes based 8 on this.
9 We do clarify in the scope that this 10 guidance may not apply to all fuel forms, especially 11 molten salt reactors, and so we have separate guidance 12 being developed for that.
13 Next slide, please.
14 Okay, this comment was --
15 (Simultaneous speaking.)
16 MR. DRZEWIECKI: -- I'm sorry.
17 MEMBER BROWN: Yes, before you leave, Dave 18 you might need to help me on the molten salt thing.
19 That's kind of an interesting thought about a coolable 20 geometry. I was probably going to ask you that 21 question later.
22 I'll just leave it for later. Excuse me.
23 MR. DRZEWIECKI: Okay, thanks Jordan.
24 Okay, so this comment was associated 25 control element insertion. It was about you know, for 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
76 1 designs that do not have neutron control element 2 insertion. For example, control drums, having 3 criteria to insert control element insertion paths 4 would not be necessary.
5 So, we did make changes because and so, we 6 did change the term control element insertion to 7 negative reactivity insertion because we do recognize 8 that in some criteria, it may not apply to all fuel 9 types or reactor designs.
10 However, we did call out that that we 11 don't think the use of drums necessarily ensure the 12 ability to insert negative reactivity.
13 So, the only change made based on this was 14 the change from control element insertion to negative 15 reactivity insertion.
16 Next slide, please.
17 Okay, this one was associated about you 18 know, trying to expand a performance envelope without 19 the use of lead test specimens, and it kind of hits on 20 I think topics that we hit on before.
21 We didn't feel comfortable providing 22 generic guidance to address all scenarios, where fuel 23 use beyond its performance envelope may be requested.
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77 1 or findings that we have make.
2 We do have some guidance in here in terms 3 of the use of evaluation models outside of its 4 restricted domain. Typically, the use of a computer 5 code or evaluation model is limited by its validation, 6 and the data over which it is used.
7 We do talk about how if you have a 8 physics-based model, it may be possible to give an 9 argument or justification to extrapolate that model 10 outside of the range where you have data, if you can 11 make a convincing argument that it's actually 12 conservative there.
13 I don't have specific examples of what 14 that would look like for fuel.
15 Next slide, please.
16 Okay, this is going back to the quality 17 assurance discussion. In terms of the data, so in 18 terms of having an assessment framework to address 19 data, we had called out, you know, having an 20 appropriate quality assurance program there.
21 We had highlighted NQA-1, and we gave an 22 example of work that was done at Argonne National 23 Laboratory that had, they have a methodology really 24 based on provisions of NQA-1 to bring up legacy data 25 to NQA-1 standards.
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78 1 And, the commentor you know, accurately 2 reflected that that's also NQA-1, and there's things 3 beyond NQA-1.
4 So, we did make a change in order to 5 clarify approaches other than ASME NQA-1. We said 6 including commercial grade and dedication, which I 7 think is also part of the NQA-1, may be acceptable 8 with just a finding that data is collected under an 9 appropriate QA program.
10 And --
11 MEMBER PETTI: So Tim, here I guess I'm a 12 little confused because the example is more of a 13 historical problem, right?
14 There's all this data that was developed 15 at Argonne for metafuel, and now you really want to 16 kind of use it in a going forward, in a maybe a 17 licensing application.
18 And, so you do a commercial grade 19 dedication sort of, because it wasn't really developed 20 under an NQA-1 program.
21 But it would seem to me that when you get 22 to, at the very beginning you talked about having you 23 know, real fuel off of a real production line 24 undergoing tests, you know, a proof test if you will.
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79 1 of the entire product.
2 So, I just see gradations here in terms of 3 exactly what, how, you know, how important is some of 4 this data to the overall qualification in allowing 5 commercial dedication alternative methods for some of 6 it may be, you know, acceptable.
7 But for that final piece, which is really 8 what you'll rely on heavily, it would seem to me that 9 you'd want to know that that's of greater importance, 10 and so the quality is more important there.
11 MR. DRZEWIECKI: Okay. Yes, I mean what 12 we were thinking about here, in terms of you know, 13 some, we do expect some use of legacy data, and you 14 know, some of that data it was collected under non-15 NQA-1 programs. And, that's what we're trying to get 16 to here.
17 And, so if there was a way, we're just 18 trying to give it some flexibility.
19 MEMBER PETTI: Yes, and I don't have any 20 problem. Legacy data I understand that. But it 21 shouldn't mean they have carte blanche in today to 22 decide okay, I've got a commercial vendor and we're 23 just not going to use NQA-1 because don't need to.
24 To me, there's a difference there in those 25 two activities.
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80 1 MR. DRZEWIECKI: Okay.
2 So those are all the comments I was going 3 to go through today. The remaining comments I thought 4 were less significant. Some of them were just you 5 know, editorial or perhaps covered by something here.
6 So, with that I was going to hand it back 7 over to yes, back to Jordan unless I see a comment, 8 I'm sorry, I see a question.
9 MEMBER BIER: Yes.
10 MR. DRZEWIECKI: A raised hand?
11 MEMBER BIER: This is Vicki Bier.
12 I want to just echo the previous comment 13 about I'm wondering whether the use of legacy data 14 could be handled as an exemption, rather than writing 15 the guidance to be flexible enough that it might be 16 interpreted as allowing it going forward.
17 MR. DRZEWIECKI: Well, I, yes. I think 18 that is an option. I do expect that this will be 19 something that will just be handled on a case-by-case 20 basis.
21 Personally, I prefer you know, having the 22 flexibility. Because we've seen things before not 23 only in fuel, but in you know, say from a hydraulic 24 testing where we've seen you know, certain evaluation 25 models being supported by data from say, like 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
81 1 literature or from university research, which is not 2 NQA-1.
3 But it's gone through an internal review, 4 a commercial dedication process in order to bring it 5 up to a level that they had confidence in. So, these 6 are things that we see even in relatively recent 7 applications.
8 So it was kind of having those examples in 9 mind that we didn't necessarily want to have too high 10 a barrier to, because you know, to require NQA-1.
11 That's clearly the preferred method. It's 12 the easiest method for us to accept. But we did seek 13 flexibility there.
14 (Pause.)
15 MEMBER BIER: All right, thank you.
16 MR. DRZEWIECKI: Thank you. Jordan, do 17 you want to?
18 CHAIR SUNSERI: We need to move this thing 19 along. We're falling way behind.
20 MR. ORENAK: Yes, this is the last slide.
21 There's not much to really report on this. We're 22 really just you know, resolving comments from internal 23 reviews, and from the comments we hear today.
24 We may have additional public meeting to 25 discuss any of the proposed revisions. That's 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
82 1 something we offered to industry and stakeholders 2 after the September 29 meeting.
3 Then, we pointed that to the final NUREG 4 and future engagements on the ongoing work to exercise 5 the framework.
6 I would note that in the comments related 7 to Part 53 and the ability to obtain a subcritical 8 state, I think that is something.
9 We were trying to be convincing with the 10 Part 53 group and while we may not have seen changes 11 specific to the Part 53 language yet, that is 12 something that we've considered and are planning to do 13 in future iterations.
14 So, I just wanted to try to make that a 15 little more clear.
16 MEMBER PETTI: Okay, we are running late.
17 So, is that everything then, Jordan?
18 MR. ORENAK: That's it, yes, thanks, Dave.
19 MEMBER PETTI: Okay, let's then ask for 20 public comment.
21 Is there anybody as a member of the public 22 who has a comment? Please unmute yourself, *6, and 23 state who you are, and give us your comment.
24 Thank you.
25 (No audible response.)
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83 1 MEMBER PETTI: Okay, hearing none, then I 2 guess we're done.
3 If there's any other comments from 4 members?
5 (No audible response.)
6 CHAIR SUNSERI: Members any comment?
7 (No audible response.)
8 CHAIR SUNSERI: Actually, given that we're 9 only 40 minutes away from lunch, I'm going to suggest 10 we just roll into the deliberation topic here, which 11 is, Dave, are you have a draft letter report?
12 MEMBER PETTI: I do.
13 CHAIR SUNSERI: Okay. Well, we can take 14 a short biological break right here, 5 minutes to give 15 Sandra time to get the report up on the screen, and 16 then we'll start again.
17 So, let's take a short break, and just 18 transition break till 11:25.
19 (Whereupon, the above-entitled matter 20 went off the record at 11:19 a.m. and resumed at 21 1:00 p.m.)
22 CHAIR SUNSERI: Good afternoon, everyone, 23 this is Matt Sunseri. We will reconvene the 690th 24 meeting of the ACRS. I'll confirm a quorum by calling 25 the roll. Ron Ballinger.
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84 1 MEMBER BALLINGER: Here.
2 CHAIR SUNSERI: Vicki Bier. Dennis Bley 3 --
4 MEMBER BIER: I'm here, excuse me. Just 5 slow.
6 CHAIR SUNSERI: All right. Dennis Bley.
7 MEMBER BLEY: Here.
8 CHAIR SUNSERI: Charles Brown. Charles 9 Brown. Vesna Dimitrijevic.
10 MEMBER DIMITRIJEVIC: I'm here.
11 CHAIR SUNSERI: Greg Halnon.
12 MEMBER HALNON: Here.
13 CHAIR SUNSERI: Walt Kirchner.
14 MEMBER KIRCHNER: Here.
15 CHAIR SUNSERI: Jose March-Leuba.
16 MEMBER MARCH-LEUBA: Here.
17 CHAIR SUNSERI: Dave Petti.
18 MEMBER PETTI: Here.
19 CHAIR SUNSERI: Joy Rempe.
20 VICE CHAIR REMPE: Here.
21 CHAIR SUNSERI: Myself is present. And 22 we'll go back, Charlie Brown. Charles Brown. All 23 right, I will check and I see, I'm sure Mr. Brown will 24 be joining --
25 MEMBER BROWN: I'm here.
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85 1 CHAIR SUNSERI: Okay, good, perfect.
2 Everyone made it back from lunch, great. So we are 3 going to continue the meeting. We have our next 4 topic, which will be on molten salt reactor fuel 5 qualification, and I'll turn to Member Petti for 6 leading us through this discussion.
7 Dave, the floor is yours.
8 MEMBER PETTI: Thanks, Matt. So, 9 colleagues, this is very timely the way this has been 10 set up this morning, having heard about more generic 11 fuel qualification, and we'll hear details of a molten 12 salt fuel qualification. This was presented to us in 13 the subcommittee last month, so it's, at least for me, 14 it's fresh on my mind.
15 So let me turn then to Chris Van Wert from 16 NRR to give us any opening remarks.
17 MR. VAN WERT: All right, thank you, and 18 good afternoon, everyone. My name is Chris Van Wert, 19 and I am the acting Chief of the Advanced Reactor 20 Technical Branch Number Two in NRR.
21 We are pleased to present, along with Oak 22 Ridge, a NUREG/CR for molten fuel salt reactor fuel 23 qualification. This NUREG/CR was developed under 24 contract by Oak Ridge and leverages their extensive 25 experience with molten salt reactor size.
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86 1 This effort is a continuation of the 2 staff's efforts to develop fuel qualification guidance 3 for advanced reactors in support of the staff's 4 responsibilities under NEIMA. As this NUREG/CR is 5 also closely related to the guidance provided in draft 6 NUREG 2246, but is specific to molten salt fuel 7 reactor designs.
8 The general approach is similar to draft 9 NUREG 2246, for example, the focus is on addressing 10 fundamental safety functions. But the guidance and 11 framework is tailored to the uniqueness of the 12 synthesized molten fuel salt as compared with the 13 manufactured solid fuel found in other reactor 14 designs.
15 This guidance provided in this NUREG/CR is 16 intended for both the designer and the regulator. The 17 draft NUREG/CR has been made available under public 18 websites since early September, and we've reached out 19 to stakeholders via technical working groups and 20 molten fuel salt reactor seminars to raise awareness 21 and solicit input. We have also solicited feedback 22 from other staff members and will address all comments 23 as we receive them.
24 The next steps are still being decided, 25 but it is possible that we will decide to develop a 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
87 1 regulatory guide which will endorse this NUREG/CR. We 2 could decide to use a single reg guide to endorse both 3 NUREG 2246 and this NUREG/CR, or it might be decided 4 to keep them separate and use two regulatory guidance 5 to endorse them.
6 We thank you for the opportunity to 7 present this important work and look forward to your 8 questions. I will now turn it over to Dr. Holcomb 9 from Oak Ridge to make the technical presentation.
10 MR. HOLCOMB: Joy has already got her hand 11 up.
12 VICE CHAIR REMPE: Sorry. But Chris, what 13 you told us is a little different than what we heard 14 this morning. So when I asked, you know, why did they 15 use a NUREG for the generic fuel qualification, and 16 then I did mention this is a NUREG/CR, which is not 17 where one usually finds staff guidance, I didn't get 18 back from the staff, oh, we're going to do maybe one 19 or two reg guides.
20 Is that in the state here, are we sure 21 about that now? Because I am curious, because it 22 seems kind of strange to have guidance for the staff 23 in a contractor's report.
24 MR. VAN WERT: Right, right. Well, as I 25 was kind of alluding to, we wanted to leverage Oak 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
88 1 Ridge's specific experience with molten salt reactors.
2 That experience is not readily available within the 3 NRC staff.
4 We are developing it, we have some 5 experience, but we definitely wanted to rely and, you 6 know, build on the experience that Oak Ridge has. So 7 that's why we did reach out to Oak Ridge for MSR-8 specific guidance.
9 As far as going into the future, that has 10 not been decided whether or not we'll have two 11 different reg guides endorsing the two different 12 NUREGs or if we'll do a single one. I merely was 13 bringing it out as possibilities either way.
14 If we go through the reg guide process, 15 obviously you'll have an opportunity to view and make 16 comments and see this again at that point.
17 VICE CHAIR REMPE: Okay, again, I'm not 18 questioning why you went to Oak Ridge, I'm questioning 19 what the final end state will be, and I'm hearing from 20 you, yeah, it may be one or two, but we're definitely 21 going to make a reg guide as the end product of this, 22 of both of these efforts. Is that decided? Because 23 that wasn't clear this morning.
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89 1 in my --
2 VICE CHAIR REMPE: Okay, so it's a 3 definitely -- because I mean the staff kind of alluded 4 to that, you know, it might be incorporated into the 5 standard review plan this morning. But again, I'm 6 kind of off-topic, but I'm just trying to understand 7 where the endgame is.
8 MR. VAN WERT: Me personally, I think 9 that's probably, the reg guide route is probably the 10 cleanest. But you know, others might speak up and 11 convince me otherwise. You know, I don't want to 12 presuppose the endgame at this point.
13 VICE CHAIR REMPE: Okay.
14 MEMBER PETTI: So Chris, this is Dave.
15 But at least from my perspective is the worst possible 16 thing is you do one for one and not for the other.
17 Whatever you do should be consistent, right? Because 18 these topics are like sisters, if you will, or 19 something.
20 MR. VAN WERT: Yes, yes.
21 MEMBER PETTI: Yeah, okay, thanks. David, 22 go ahead.
23 MR. HOLCOMB: Good afternoon, folks. As 24 Chris has already indicated, this is a NUREG/CR that's 25 currently posted on ADAMS for comment. It has been 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
90 1 now since July. And Chris had indicated we are still, 2 you know, seeking comments, including from the ACRS, 3 here. And I believe he's indicated already that we're 4 intending to keep the comment period open through 5 December 15.
6 So, and my colleagues have been working on 7 this for the past few years. Myself, George Flanagan 8 and Mike Poore here at Oak Ridge. Have to say we do 9 miss the two original leads from the NRC staff, Joe 10 Williams and Stuart Magruder, both of whom are now 11 retired. Next slide, please.
12 MR. VAN WERT: I am actually attempting.
13 MR. HOLCOMB: Okay, well, the next slide, 14 it talks about the, what's the technical base -- what 15 is the definition of fuel qualification for a molten 16 salt reactor. But it -- and this is from Joe 17 Williams's presentation. Again, elements of achieving 18 sufficient understanding of fuel behavior.
19 It's a process for -- provides high 20 confidence that physical and chemical behavior of fuel 21 is sufficiently understood, that it can be adequately 22 modeled under both normal and accident conditions, 23 reflecting the role of fuel design in the overall 24 safety of the facility.
25 Uncertainties are defined so that the 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
91 1 calculated fission product releases include the 2 appropriate margins to ensure conservative 3 calculations of the radiological dose consequences.
4 The reason this is important, you know, 5 separate from the obvious, is that this is different 6 than the solid fuel, which includes -- has been 7 fabricated. Because, again, liquid fuel is not a 8 fabricated product, it's a synthesized product. And 9 we'll talk more about that in the following slides.
10 And just pictorially showing that, you 11 know, fuel qualification determines the fuel 12 performance. Or it provides understanding of what the 13 fuel performance would be, and it's a major element in 14 the overall evaluation of accident scenarios and 15 determination of what a source term would be. Next 16 slide, please.
17 All right, so we do build from the NUREG 18 2246 in the earlier versions, and it's essentially 19 trying to provide a parallel framework reflective of 20 the chemistry and physics of a liquid fuel system. So 21 again, looking at the fundamental safety functions to 22 derive the success criteria for the fuel salt 23 properties. Again, using the goal decomposition 24 process, similar to what was used in NUREG 2246.
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92 1 is that dozens of MSR designs are under consideration 2 and more are introduced every day, or every month 3 probably is better. And nearly all these have been 4 developed over the past decade.
5 And so we really can't focus on a specific 6 design, because which designs are going to be 7 presented for regulatory adequacy review over the next 8 decade is uncertain and likely to change.
9 The fuel salt qualification process, so, 10 steps back a bit and relies upon sort of the 11 fundamental chemistry and physics, which is 12 independent of the reactor configuration, to determine 13 that it's, you know, how it relates to the safety 14 adequacy. Next slide, please.
15 Fuel salt does have substantial and 16 fundamental differences from solid fuel, though. It 17 is, as you can see on the, pictorially, the liquid 18 fuel is chemically damageable and may be repairable 19 during use just by changing its composition. Solid 20 fuel, on the other hand, is mechanically damageable.
21 The composition of the liquid fuel can be 22 adjusted during use, or with the solid fuels largely 23 the composition is set prior to use. The properties 24 of a liquid fuel depend simply upon its composition 25 and its state, largely the temperature, pressure's not 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
93 1 a substantial issue.
2 The properties of the solid fuel depend 3 largely on its fabrication processes in addition to 4 the composition. The -- one of the other negative 5 things of a liquid fuel is because a small container 6 breach could release nearly all the radionuclides.
7 Essentially, bump a whole in the bucket and all the 8 liquid flows out.
9 And that's very different than a sold 10 fuel, where you crack a fuel rod and the pellets tend 11 to stay in. And so the basic thing is, however, is 12 that the liquid fuel serves both as the fuel and the 13 heat transfer media. So it's got to satisfy the 14 requirements both for the coolant and as the nuclear 15 process. Next slide, please.
16 Okay, however, as I mentioned, there are 17 common properties of any halide salt. So that enables 18 the creation of a general fuel qualification method, 19 provided it stays -- rely upon the fundamentals. The 20 specific accident sequences of any -- of a reactor are 21 design-dependent. But the basic operational and 22 fundamental safety functions are common to any nuclear 23 power plant, contain, cool, and control.
24 The halide salt characteristics are common 25 to any molten salt that's a halide. No one's 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
94 1 proposing it's not a halide seriously. These are high 2 boiling points, which results in low pressure. Low 3 Gibbs free energy, essentially it's a representation 4 of low chemical potential energy.
5 So it doesn't react chemically vigorously 6 with anything. And natural circulation heat transfer 7 properties, things like well, gee, it expands when it 8 gets hot, so it gives it a strong buoyancy. It does 9 not have really good or really high thermal 10 conductivity, but is -- has high heat capacity.
11 Fuel salt interacts with its containers by 12 a common chemical and physical mechanisms. For 13 example, thermal energy transfer, chemical reactions, 14 and mechanical processes. So they're all -- so they 15 -- we understand what are the issues involved, though 16 the specifics are dependent upon the specific salt and 17 the particular container. Next slide, please.
18 So one of the big issues is that what is 19 fuel salt on here, because we're interested in the 20 radionuclide release throughout the plants. And so 21 the fuel salt really does not come in discrete 22 elements, you know, like a rod or an assembly, and it 23 moves independently of its container.
24 So the container initially, it'd be some 25 vessel or such where it's shipped in, and it's 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
95 1 transferred to another one where it circulates around.
2 And you know, they're often things like the reactor 3 vessel, the heat exchanger, which are in direct 4 contact with their -- might be replaced, you know, 5 separately from the fuel.
6 You know, in contrast, solid fuels, the 7 cladding in the fuel assembly structures are qualified 8 as part of the solid fuel.
9 So what the method relies upon is that the 10 fuel salt includes all the material containing 11 fissionable elements or radionuclides that remain in 12 hydraulic communication, but does not include the 13 surrounding system structures or components.
14 So salt vapor are aerosols that remain 15 part of the -- remain part of the fuel salt system 16 until they become adequately trapped, so they couldn't 17 be reasonably be released with a fuel accident.
18 And contain corrosion products become part 19 of the fuel salt. As well, fresh and used fuel salt 20 in onsite storage are within scope. Once it's 21 transferred to independent spent fuel storage 22 facility, it ceases to be within scope of fuel 23 qualification. Next slide, please.
24 Functional containment is a very important 25 concept for molten salt reactors and how they provide 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
96 1 adequate radionuclide retention. Essentially, barrier 2 performance must be graded to release radionuclides 3 into the environment. And the performance degradation 4 can occur through failure or bypass.
5 So for example, if you have a brittle 6 reactor vessel and it shatters, you will get the fuel 7 salt to pour out. On the other hand, because these 8 are low pressure systems, it's fairly much more likely 9 that someone does something like leave a valve open or 10 leave a hatch open or something.
11 And so that during an accident, again, one 12 of the challenges is that a fairly -- that you can 13 lose all the radionuclides from a container layer 14 through a bypass. Fuel salt properties that stress 15 barriers cause them to be more likely to release 16 radionuclides.
17 For example, in temperature increases, you 18 know, increase the vapor, vapor pressures in the cover 19 gas, as well as decreasing the strength of the 20 container.
21 Different performance requirements will be 22 involved for the things which are normally in contact 23 with the fuel salt, things -- heat exchanger to 24 reactor vessel plumbing, versus those that only need 25 to withstand the accident.
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97 1 For example, if your -- if you use a guard 2 vessel, the guard vessel only needs to withstand the 3 properties of the coolant salt while the coolant's --
4 during the accident where the fuel salt is touching 5 the guard vessels. Next slide, please.
6 Fuel salt properties have substantial 7 impact on the containment performance. Under normal 8 operation, the salt-seeking chemical -- radionuclides 9 are chemically retained. Most of the lanthanides and 10 a number of the alkalis are -- tend to form stable 11 chlorides and fluorides.
12 Fission gasses -- fission gasses have very 13 low solubility in the liquid, and they tend to largely 14 escape. Some of them might go into the graphite in 15 thermal spectrum reactors, but frankly almost, you 16 know, effectively all of them that have half-lives 17 longer than few seconds escape.
18 The noble, which in our case means the 19 insoluble metals, largely they either plate out or 20 escape into the vapor. You get a higher vapor release 21 than you would normally anticipate because they're not 22 truly dissolved into the system, so they don't have 23 the surface tension inhibition from escaping into the 24 -- into the vapor phase.
25 The fuel salt causes stress on and 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
98 1 potentially resulting in damaged container materials.
2 Corrosion, erosion, creep. So it does -- it's just 3 part of the normal operations. And the tritium 4 behavior does depend upon the, both on the operations 5 and the redox state.
6 Because the tritium, if it's TF or, you 7 know, or TCL, mostly it's a problem in the fluoride 8 salt reactors. Then the -- it does not tend to escape 9 because it's a molecule, and till the molecule is 10 broken it doesn't -- that mostly it doesn't 11 substantially diffuse through the wall.
12 On the other hand, if it's T+ or T2, it is 13 much more likely to diffuse through the barrier. So 14 the chemical configuration depends upon the redox, 15 which is a property of the salt.
16 Under accident condition, you know, 17 mechanistic analysis of radioactive material transport 18 depends upon the fuel salt properties -- properties 19 things like how many aerosols are going on. What type 20 of heat -- what's the thermal conductivity.
21 Substantial reduction in cover gas, heat, 22 content, and radiotoxicity over the first couple of 23 days. A lot of the short-lived radionuclides are in 24 that cover gas because they're -- they got noble gas 25 precursors. You know, a lot of the computations on 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
99 1 this just to give you an idea on the order of 2 magnitude is that 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, you know, drop three 3 orders of magnitude in the radiotoxicity in the cover 4 gas.
5 So it's that large, early release that is 6 the most significant for an MSVR, and that really 7 needs to be engineered essentially out of the 8 equation. You cannot -- that would be a catastrophic 9 type release. There are high -- essentially high 10 potential consequences of large, early cover gas 11 releases. Next slide, please.
12 Fuel salt boundary breach accident 13 progression is part of a performance-based and 14 deterministic fuel qualification. So multiple spots 15 in the CFR require evaluation of possibility of 16 fission product releases from core into containment.
17 The fuel salt and cover gas can't directly 18 stress exterior containment layers without first 19 breaching an inner containment layer. So that's, you 20 know. So and then the high radiation and high 21 temperatures immediately outside the fuel salt 22 boundaries substantially circumscribe characteristics 23 of materials that are adjacent to the fuel salt 24 container.
25 Essentially you're not going to have 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
100 1 organic materials where it can pour onto because they 2 can't withstand normal ops because of the high 3 radiation and high temperature.
4 The focus is on the fuel salt properties 5 that must be known to adequately model accident 6 progression and interaction characteristic with 7 materials within containment. So that's really where 8 most of the report is focused. Next slide, please.
9 Fuel-related advanced reactor requirements 10 are similar for liquid and solid fuel. So here's just 11 an example of 50.43(e)(1)(i) requires that performance 12 of each safety feature of the design's been 13 demonstrated either through analysis, appropriate test 14 programs, experience, or a combination thereof.
15 So fuel salt thermophysical and 16 thermochemical properties provide the information 17 necessary to model its role in enabling the plant 18 safety features to perform plant -- safety functions.
19 And the fuel salt properties vary with both 20 composition and temperature.
21 Fuel salt properties need to be determined 22 across the range of the temperatures and composition 23 that span the potential operational accident 24 conditions. Essentially we have an acceptable range 25 of properties and such, and as long as you stay within 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
101 1 the box, it is acceptable.
2 The quality of the fuel salt property 3 needs to be sufficient to enable modeling the role of 4 fuel salt and achieving the plant safety --
5 fundamental safety functions. This is one of things 6 I know quality assurance was a major topic earlier 7 this morning.
8 And it is going to be making sure that we 9 have the appropriate focus on quality and the fuel 10 salt property such that consequences of the inaccuracy 11 or the amount of unknown are the central focus to 12 this, because for many of the fuel salt property 13 measurement methods, there are not ASTM standard 14 methods for how does one acquire this data.
15 And on the other hand, the consequences of 16 inaccuracy or uncertainty in the data are very much 17 design-dependent. And in some cases, focusing on 18 trying to reduce the uncertainty does not reduce the 19 consequences of any accidents. And so we have to make 20 sure that the quality assurance is tied very much to 21 the consequences of the uncertainty. Next slide, 22 please.
23 MEMBER PETTI: So David, just a question 24 on that. Some of the stuff I wouldn't expect to be in 25 ASTM, but are there standards in the chemical world 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
102 1 on, you know, how to measure the vapor pressure like 2 a Hertz-Knudsen mass spectrometer? Are there -- is 3 there a standards organization in --
4 MR. HOLCOMB: It is not uniform, is the 5 problem. And there are different things that come 6 out, like if you follow the glass industry versus the 7 petroleum industry. There are different 8 methodologies, and there's been an awful lot of round-9 robin testing.
10 And it turns out one of the advantages of 11 having multiple national involved in them, in 12 developing this, is that they are using different 13 methods. And so we're getting cross comparison and 14 finding out, well, they're pretty close. They're not 15 perfect, but they're pretty close on there.
16 And there's -- and a lot of things rely 17 upon things like NIST standard materials. So you'll 18 take a piece of sapphire and look at the heat capacity 19 and the thermal conductivity of the sapphire at this 20 temperature and compare that to your fuel salt. And 21 there's a -- and there's a lot of active effort in 22 thing like round-robin testing.
23 But things like, you know, we know 24 dilatometry is a basic method to look a volume, you 25 know, volume which gives you density. And well, on 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
103 1 the other hand, not much has been done with things 2 like plutonium, sodium chloride, which folks are 3 interested in, and uranium sodium chloride.
4 So you know, just last week, LANCE, the 5 folks at LANL published a using neutron imaging as a 6 means of doing dilatometry to assess the variation in 7 uranium sodium chloride with temperature.
8 And yes, it's being done under the 9 appropriate -- the quality assurance program, which is 10 appropriate for LANCE data, but we have to be certain.
11 And so one of the biggest challenges is appropriately 12 assigning the uncertainties and where are the errors 13 bars that are resulting from this.
14 MEMBER PETTI: Thanks.
15 MR. HOLCOMB: All right, liquid fuel salt 16 assessment framework follows a template. Again, 17 advanced reactors, you'll recognize this from the 18 previous presentation. So essentially a top-down 19 approach is used to decompose the top-level goal of 20 fuel qualified to lower level supporting goals. And 21 then qualifying the fuel develops high confidence the 22 fuel will adequately perform its role in enabling the 23 facility to achieve its safety objectives.
24 And this is part of the main thing, is 25 that the facility achieves the safety objectives and 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
104 1 the salt -- and the fuel performs some of the roles in 2 enabling that. It does not independently perform most 3 of the safety functions. And that's -- and so a lot 4 of things is what is and -- what is and is not within 5 the scope of fuel qualification.
6 We don't want to make fuel qualification 7 the entire safety analysis report. But the lower 8 level supporting goals are further decomposed until 9 clear objectives in the goals are identified that can 10 be satisfied with direct evidence. So you can sort of 11 see the breakdown, and it's the same basis as done 12 with the other, you know, with the sold fuels. Next 13 slide, please.
14 Again, qualification is based upon 15 understanding the physical and chemical properties 16 represented in fuel salt samples. Yeah, liquid state 17 significantly changes the behavior of fuel. Liquids 18 don't accumulate internal stresses, so you don't get 19 things like history-dependent properties. It doesn't 20 matter what the irradiation was in the past or if it 21 was bent before, well, it's a liquid.
22 Fuel -- on the flow that homogenizes the 23 fuel properties. So they don't -- the position-24 dependent properties or size-dependent properties, 25 which are some of the real challenges in solid fuels.
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105 1 It doesn't bow. The chemical and physical properties 2 are set by elements in the composition temperature.
3 It's actually one of the basic parts, you 4 know, it's the see Spot run part of chemistry. You 5 don't care what the isotope is, you care what the 6 element is. Because it's the outer-shell electrons 7 that determine the physical and chemical properties.
8 So, which really helps when you can use 9 small, minimally radioactive and why it's minimally 10 radioactive is some of the heavier -- they simply 11 don't have nonradioactive species.
12 But you don't have to use, you know, when 13 you're doing cesium, you don't have to use cesium-137.
14 This is, you know, use something which is -- which is 15 nonradioactive when you're making liquid fuel salt 16 sample to provide representative physical and chemical 17 properties. Next slide, please.
18 Liquid fuel salt qualification establishes 19 acceptable composition range that maintains the safety 20 functions. Basically, fuel salt is a halide salt, 21 it's a Newtonian fluid. It doesn't have any weird 22 thixotropic things. It's a pretty standard fluid.
23 The heat transfer and fluid flow behave in 24 well known manners. You get continuous variance in 25 the physical properties with composition. It's no --
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106 1 there aren't weird inversions, they just, you know, 2 follow lines or curves.
3 You know, reasonable assurance of adequate 4 protection derives from a combination of measured salt 5 composition and the knowledge of the resultant 6 chemical and physical properties. A liquid fuel salt 7 property database then captures the relationship 8 between fuel composition and properties. Next slide, 9 please.
10 Liquid fuel salt property database relates 11 to the -- essentially relates to the composition of 12 the physical properties and aids the developers and 13 the regulators. The database development is currently 14 underway, sponsored by DOE-NE.
15 Actually, it I believe is going through 16 public release this week. This week we have gotten 17 all the approvals, it's, now it's in the mechanistic 18 parts of how do we get it through and maintain version 19 control and all the things because you -- as 20 additional data and corrections are made into that.
21 The salt property measurement program 22 continues in progress. We'll, as anticipated, 23 continue for multiple years as we add more complexity 24 to it.
25 Part of this is much like the NEEMS 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
107 1 program, we are trying to develop a very detailed and 2 advanced database that enables advanced modeling with 3 high fidelity, which may -- which -- elements of which 4 will be necessary for safety. Elements of which will 5 not be, you know, necessary for a reasonable assurance 6 of adequate protection, but would be useful to enable 7 higher performance.
8 Okay, but again, requires appropriate 9 quality assurance for both new and existing data 10 because halide salts are long and historically used 11 and some of the data comes out of existing journals 12 and existing things. The nice thing about it is 13 consistency check with adjacent materials with small 14 changes.
15 You can -- and it is in the manner of 16 understanding what is the required quality, and that 17 is put this into your accident progression and then do 18 sensitivity analysis to figure out, well, if you 19 doubled this or halved it, does it matter. And 20 database is initially sparsely populated.
21 The safety analysis and accident 22 progression models are performed with bounding values 23 to establish the acceptable performance range. And 24 additional data is added to the database over time.
25 The goal is to eventually require only composition and 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
108 1 a temperature measurement at operating plants that 2 look up the properties from the database. Next slide, 3 please.
4 MEMBER MARCH-LEUBA: Hey, Dave, comment to 5 this, and this is Jose. This morning we were talking 6 about a different program, and the issue of NQA-1 came 7 along. The de facto standard for the industry is if 8 you use NQA-1, you're okay. Have you given any 9 thought to what quality control level you need to 10 satisfy Appendix B?
11 MR. HOLCOMB: We spend a fair amount of 12 time, that is actually a number of the projects which 13 are ongoing involve things like running sensitivity 14 analyses to try to understand this better. Because we 15 are running into doing appropriate quality control to 16 maximize the performance of the measurement equipment, 17 for example, to ensure just the standard part. And 18 that is traditional quality control to ensure that 19 that is being done appropriately.
20 But the big thing is is that some of the 21 properties, the uncertainty requirements are very 22 different depending upon what the accident sequences 23 are. And the -- we don't -- and we're developing tool 24 sets to look at sensitivity of the -- for essentially 25 run MELCOR and -- with different values of fuel salt 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
109 1 properties to see how -- what is the outcome. How 2 does your source term change with that.
3 We think that certainly you will need an 4 appropriate nuclear quality assurance program, you 5 know, which is, you know, in the use of the data. And 6 however, a measurement of something where you have 7 changed one property has supporting data from all of 8 the other adjacent -- other adjacent materials.
9 For example, if you change the amount of 10 cesium in a fuel salt on this, and you add this to it, 11 there -- the internal consistency of the database, 12 because this is a continuous space in the database, 13 provides additional reassurance that this isn't a --
14 this isn't a parameter outlier. That it needs to be 15 consistent. So there is consistency checking 16 independent of the data being acquired.
17 So my answer in some ways is we don't have 18 what I call a perfectly good answer to this because 19 ideally every piece of data, both historical and 20 future, would be done under a full NQA-1 program. And 21 I'm not sure that that is absolutely necessary when I 22 look at what are the consequences of having higher 23 uncertainty than I would like to have. Which is the 24 consequences of not doing it because I have to accept 25 a higher uncertainty band. If I have --
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110 1 MEMBER MARCH-LEUBA: If you think about 2 it, for light water reactors, we use correlations for 3 water density and all the other properties for H2O 4 which were not measured under NQA-1. And we are doing 5 it today.
6 So but just keep in mind that eventually 7 an applicant is going to use all these properties.
8 And the better quality control on paper where you have 9 behind a pedigree, you have behind, the easier life 10 will be for that applicant.
11 (Simultaneous speaking.)
12 MR. HOLCOMB: Agree with you and we 13 recognize this is an issue. And we are in a modern 14 environment where essentially building the database is 15 not a pure measurements thing. The NEEMS program 16 actually is the home to the database.
17 Because we are using fairly advanced 18 modeling tools to say this is what we think it should 19 be, and here are where the key spots to make the 20 measurements are, because frankly measurements are 21 expensive and time-consuming. And so then we try to 22 validate the correlations.
23 It's much like life projection in a, you 24 know, in materials on there. Well, this is where we 25 think the strength curve is going to be. Well, now we 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
111 1 take a grab sample and say, you know, if you are 2 following that line where it should be, you have a 3 higher confidence. If you're not following it, you 4 got to do additional measurements, or refine your 5 models.
6 But I fully agree with you. It is going 7 to be -- that is part of the challenge for any 8 applicant, is to justify that they are taking a 9 conservative values for the uncertainties in the 10 properties.
11 MEMBER BIER: If I can have a quick 12 followup, this is Vicki Bier. I understand completely 13 why you want to use the historical data to reduce the 14 uncertainties where data is available. Do you see any 15 restrictions or problems with saying that all new data 16 would be collected under the, you know, applicable QA 17 requirements or whatever?
18 MR. HOLCOMB: That's the issue, is what 19 are the applicable QA requirements. I gave you the 20 example of dilatometry at LANCE being done there. We 21 -- people are performing these measurements under 22 quality assurance programs that are appropriate at 23 their facilities.
24 MEMBER BIER: Got it.
25 MR. HOLCOMB: And are being done at --
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112 1 with round-robin confirmations, because not just one 2 person is doing this. And so we are -- they're 3 working on it, but we don't have a, you know, this 4 isn't a known this is how you measure it, this is the 5 one true method, this is what the uncertainty you get 6 from doing that.
7 This -- we're still -- we're operating at 8 the state of the art, and that prevents you from 9 having a traditional NQA-1 program where it requires 10 always on how do you confirm with standards. There 11 are --
12 MEMBER BIER: Perfect, thank you.
13 MR. HOLCOMB: Yeah, you're welcome.
14 MEMBER BIER: That's the explanation I 15 needed, thanks.
16 MEMBER KIRCHNER: Dave, this is Walt 17 Kirchner. Can you just share with us a little a bit 18 more about how fission products might impact your 19 salt? You know, you're going to go through some 20 either online refueling or batch refueling.
21 You'll be taking off fission products, 22 probably at least the gaseous ones and so on. How 23 does this mix of all kinds of fission products affect 24 the salt itself?
25 MR. HOLCOMB: A lot of the properties it 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
113 1 doesn't affect it almost at all. For example, at MSRE 2 we hadn't bothered to recheck the density of the 3 viscosity because it's such small amounts of things.
4 On the other hand, things like reactivity, 5 you get a very substantial change when you add more 6 fissile material and you check -- and it again, 40% of 7 the fission products basically have got a noble gas 8 some place in their decay chain. And that's so then 9 tend to get out.
10 And then what you do with them is very 11 much a design-dependent. Some people say, well, keep 12 them in the fuel salt, that's the best place to leave 13 them and they generate heat and we want to keep them 14 there. And then you will accumulate them. They'll 15 also transmute. They'll decay towards stability.
16 And the answer is most of these things, 17 the -- because fuel in most cases is not a true 18 concentrate, and that, you know, you're diluting a 19 concentrate in. For example, at the MSRE we had 20 something like a 0.9% uranium fluoride loaded.
21 MEMBER KIRCHNER: Okay.
22 MR. HOLCOMB: And LANCE is spelled L-A-N-23 C-E, it's all caps.
24 MEMBER KIRCHNER: Yeah. Dave, what about 25 some of the fission products that are more, I'm not a 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
114 1 chemist, but I'll use the term reactive? You know, 2 that will either plate out on metals preferentially, 3 or how do you deal with that? It seems to me that 4 this database, that I get the goal of the last bullet, 5 but it seems to me this may be a very big database, 6 given the variety of --
7 (Simultaneous speaking.)
8 MR. HOLCOMB: It's -- the nice thing is 9 small, small reactions are very small on here. And 10 that fluorine is the first thing it's going to react 11 to on there. So cesium becomes cesium fluoride. It 12 just is -- and we know that cesium fluoride, well, we 13 know what the melt point of cesium fluoride, what know 14 what the vapor pressures of cesium fluoride is.
15 And if you have small quantities of a lot 16 of things, the nice thing is is it doesn't do very 17 much because the interaction, you know, minor, minor 18 constituent relationships. We know a lot about how 19 impurities in the thermochemistry of small impurities 20 impacting other small impurities. And the answer is 21 it doesn't do much on small stuff.
22 Now, as far as do we form nanoparticles 23 and the -- and then things cluster, indeed, the things 24 that are noble tend to plate out. They plate out on 25 surfaces and/or form clusters. You're going to filter 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
115 1 on there if you need to the things that don't just 2 plate out on surfaces.
3 In general, things plating out on surfaces 4 is often beneficial because you're essentially 5 depositing an insoluble layer on your reactor vessel, 6 and that's essentially you're building your own 7 protection on. On the other hand, again, many of 8 these things form aerosols and they form a mist over 9 the, you know, the salt.
10 So one of the things we're going to be 11 very interested in, for example, in a salt spill 12 accident is to -- to what extent can I actually rely 13 upon radiative cooling because I formed a mist because 14 a number of the radionucles are, you know, suspended 15 in the air, or suspended in the atmosphere above it.
16 And so that's the type of information 17 which is in some of the database and why we're 18 performing salt spill measurements, and that's why the 19 radioactive materials are in salt spill measurements 20 and why INL has got a large effort, you know, start --
21 you know, just getting cranked up on things like what, 22 you know, what do irradiating fuels have.
23 But otherwise, I mean, you know, if you 24 create another element in a liquid, well, it's going 25 to react with that liquid locally, and you will get --
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116 1 form a different thing. Essentially, the fission 2 process is oxidative, and then the decay process tends 3 to be reductive. And so you shift the redox at times, 4 and we measure the redox.
5 At MSRE, once a week they sample the fuel 6 salt -- fuel salt and determine by the ratio of the U3 7 to U4 in there, which is use that as an indicator for 8 the redox condition, and they just actually -- the 9 first thing comes out is the most oxidizable component 10 out of the container material, which turns out to be 11 chromium.
12 So they just measured the chromium content 13 as an indicator of the redox condition, and they just 14 kept adding enough metallic beryllium as a reducing 15 agent until the amount of chromium stopped going up.
16 MEMBER BALLINGER: Yeah, this is Ron 17 Ballinger. I mean, the key here is to know and 18 control the potential, and that's what you're doing, 19 right.
20 MR. HOLCOMB: Yeah, you say how do measure 21 it. It's not actually real easy to measure in most 22 case, except for by indirectly, things like the U3:U4 23 ratio. A thermodynamic reference electrode is 24 somewhat difficult because of the low signal and the 25 flow and the hot radiation area.
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117 1 However, its impact is pretty nicely 2 measurable with things like oxidizing your container 3 material or shifting the ratio of something which is 4 a -- has multiple redox states.
5 MEMBER PETTI: So Dave, but there are 6 fission products that don't respond to redox, like 7 tellurium. And tellurium --
8 MR. HOLCOMB: Tellurium does a very good 9 job. We did that very much so. It was a solid and 10 deposited on the vessel, which was a problem at MSRE.
11 MEMBER PETTI: Right.
12 MR. HOLCOMB: And when we shifted the 13 redox, it became a liquid and stayed suspended and 14 didn't deposit. That's how -- that was largely, if 15 you read the reports from the late 70s when they were 16 trying to figure out how to deal with this, they 17 basically said you shift the redox over.
18 It now stays in liquid phase, and it goes 19 -- and we no -- and it no longer deposits. And so we 20 don't have to worry about it so much.
21 MEMBER PETTI: I wanted to go back, before 22 you move on, on this whole database issue. It seems 23 like it might be worth considering a formal data 24 qualification program where one looks at all this data 25 from the different sources and a group of experts 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
118 1 blesses it. You know, yes, you know, if there's 2 something that's an outlier, you flag it as an 3 outlier.
4 You say that doesn't make it into the 5 database, you know, for whatever reasons. But that 6 you go through, because you don't have a lot of the 7 standards in everything, but you go through a 8 systematic data qualification process that provides, 9 you know, some confidence that the data have been 10 looked at, examined.
11 Not just compiled, right, by different 12 researchers, but as some sort of systematic process.
13 This has been used in the nuclear world and could be 14 useful here.
15 MR. HOLCOMB: And indeed you have just 16 described the rich man's version of what we are 17 currently doing. Ted Besmann is doing precisely that 18 for the thermochemical data on there with his group --
19 with his group at University of South Carolina. It 20 was through the NEEMS program, is really managing this 21 effort. And that is doing that.
22 The problem is frankly right now is that 23 there is -- there are not sufficient resources to do 24 the formal elements of that. So we are doing this, 25 you know, that's -- you're exactly correct, that is 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
119 1 what we're doing. But the level of formality for data 2 acceptance that I would like to see on some of this is 3 beyond the financial resources that are currently 4 available.
5 And that's -- but is it -- but we're doing 6 this as to we've got a team of the experts who are 7 looking at it and are looking at each piece of data 8 and deciding on the acceptance and seeing whether it 9 is consistent, whether it matches other expectations, 10 whether it matches the models. All that is precisely 11 how the database is currently being built.
12 It is not done in a formally nominated 13 process where you have these are the people who are --
14 where you would anticipate having a, you know, 15 designee from multiple organizations, each one of them 16 independently looking at this where you treat this an 17 independent -- as a multiple peer review process. And 18 that's just, we don't have the resources to do that.
19 MEMBER PETTI: Okay, okay.
20 MR. HOLCOMB: Fuel salt properties, you 21 know, support modeling reactor performance under both 22 normal and accident conditions. The heat transfer of 23 Newtonian fluids is determined primarily by density, 24 viscosity, and heat capacity. It's unsurprising.
25 The thermal conductivity and radiative 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
120 1 heat transfer parameters can become important in 2 specialized situations, things like stagnant channels 3 or narrow channels. You'll get -- the (audio 4 interference) become very important.
5 So here pictorially, here's the fuel salt 6 database, which, okay, you've got the composition and 7 the properties are in the database. That tells you --
8 provides the fuel performance, so you look at normal 9 conditions and the accident scenarios and say do you 10 achieve the fundamental safety functions. Next slide, 11 please.
12 Fuel salt supports the plant's system 13 structures and components in achieving the fundamental 14 safety functions and the regulatory requirements.
15 Qualification focused on identification and 16 understanding the fuel salt property degradation 17 mechanisms that occur as a result of irradiation 18 during reactor operation.
19 Essentially, the fuel salt has to survive, 20 you know, can't dissolve the material just under 21 normal ops. And so we're trying to say is it becomes 22 the fuel elements of it is what happens in the reactor 23 as a result of reactor operations.
24 One of the really distinctive things about 25 liquid fuel is that property repair, just composition 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
121 1 adjustment, might, may be incorporated into normal 2 operations. This is not for all of these, because 3 some people are planning on using, or some developers 4 have proposed having fuel salt in sealed units 5 immersed into another coolant.
6 And in which case, the fuel salt would not 7 be accessible during normal operations but might be 8 accessible prior to future use.
9 The normal operations in AOO fuel salt 10 properties much result in sufficient margin from 11 damage to safety-related SSCs, and under accident 12 condition the fuel salt properties must not result in 13 sufficient damage to safety-related SSCs to prevent 14 them from achieving their function.
15 In other words, you can't do something 16 like, you know, under an accident, the fuel salt can't 17 get so hot or some of the things that it would, you 18 know, damage the containment layers. Next slide, 19 please.
20 MEMBER KIRCHNER: David, this is Walt 21 Kirchner again. Are there, with salt fuel, fuel 22 salts, are there, when you get to off-normal 23 conditions and such, are there cliff effects that one 24 would worry about? Are there things like, let me --
25 this probably is not plausible or physical.
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122 1 But say the fission products that are in 2 circulation, not the gases but the others, precipitate 3 out or things like that. Are there cliff-like 4 phenomena that you can have with a salt system, or?
5 MR. HOLCOMB: That's really one of the 6 advantages of salts is they really are nowhere near 7 cliff-like phenomenon. The things that you start 8 doing is you get hot enough that you do things like, 9 well, the reactor vessel starts deforming on this.
10 But you need to get very hot for a very long time to 11 really, you know, exceed the creep margin that's built 12 into most things.
13 So the fuel salt properties don't really 14 do anything like that. So that's really nice about 15 the fuel salts in terms of under -- being able to 16 model what's going on, is that we -- is that the 17 containers and the materials around them are much more 18 vulnerable to things like a temperature excursion on 19 this.
20 I mean, look at the boiling point of, you 21 know, most of the fluorides is like 1400 C in this.
22 And you get higher solubilities at higher 23 temperatures. You tend to get better heat transfer at 24 higher temperatures.
25 So all the excursion directions under 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
123 1 accidents that you worry about tend to improve the 2 performance of the -- of the salts in terms of the 3 safety-related functions.
4 MEMBER KIRCHNER: So you don't have 5 phenomena like eutectics where you get somewhere on 6 the curve and all of a sudden you change things like 7 viscosity substantially, as an example? You don't, in 8 general the halide salts don't have those kind of 9 issues.
10 MR. HOLCOMB: You, certainly if you change 11 the composition of the material substantially you will 12 get changes in the property -- in the properties. You 13 -- that is why you have an acceptable window on there.
14 And if you're trying to operate in a spot 15 where, for example, gee, at my, you know, I'm going to 16 need my decay, natural circulation decay heat removal 17 to start up, you know, this fast, I'm going to need to 18 make sure that my viscosity is well known and is below 19 a threshold value on this.
20 But they don't change dramatically with 21 small compositions. This isn't, you know, adding, you 22 know, cornstarch to gravy on there. This is not --
23 this a Newtonian fluid with classical properties.
24 MEMBER KIRCHNER: Thank you. I never 25 thought of gravy-making as a non-Newtonian event, but 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
124 1 I'll pocket that comment. Thank you.
2 MEMBER BROWN: Can I ask a question? It's 3 Charlie Brown. With the molten salt flowing through 4 whatever medium you have, how does it maintain a 5 uniform consistency and/or stratification?
6 Typically, well, I don't want to say 7 typically. With other fluids you get more friction at 8 the walls and it slows down and in the middle it's 9 faster or whatever. What type of -- how do you do 10 that, how do you maintain --
11 MR. HOLCOMB: There certainly is -- there 12 certainly are recirculation pockets, and that is one 13 of the challenges, particularly in a high power 14 density reactor where you're getting a recirculation, 15 what's the recirculation ratio.
16 And you're going to be interested in the 17 design of the fluid flow so that you do not have a 18 someplace which is not getting washed out well. That 19 is an element of the thermohydraulics design in your 20 reactor. It's not really so much -- yes, the fluid 21 properties do influence, you know, what the 22 recirculation ratio is.
23 But a lot of that what does your -- what's 24 your nozzle design on the input and output on this.
25 A lot of it is also what your power density is in the 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
125 1 generation, where the bubble generations are for 2 fission gases. So there are operational constraints 3 about, you know, you will certainly get eddies on 4 this. If you're -- within the system. It is not 5 fully uniform.
6 And particularly the biggest non-7 uniformity is that the top of core is hot and the 8 bottom of the core is colder. Because that's what the 9 core does, is heat the salt up. And then the top of 10 the heat exchanger is hotter and the bottom is colder 11 if you're operating in that direction.
12 And that's actually one of the most 13 significant corrosion potential mechanisms, is the hot 14 tends to dissolve more material and the cold carries 15 less of it, so you tend to transport material from the 16 hot region to the cold region.
17 This is going to be an element of all your 18 both normal ops, you know, evaluation of the -- the 19 lifetime of the material, and of -- most of these 20 properties, things like corrosion, though, are slow 21 relative to an accident sequence.
22 They may be an accident initiator where 23 you corroded through, for example, you corrode through 24 your heat exchanger tubes. Well, you've now initiated 25 an accident. But there's not going to be significant 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
126 1 corrosion then during the accident.
2 MEMBER BROWN: Okay, does the -- the flow 3 is relatively slow in these, isn't it? I mean --
4 MR. HOLCOMB: Uh huh.
5 MEMBER BROWN: What's -- what velocity are 6 you -- or mass flow --
7 MR. HOLCOMB: Well, it depends upon, 8 again, the power density of the reactor.
9 (Simultaneous speaking.)
10 MR. HOLCOMB: You're trying to minimize 11 because fuel is expensive. They try to up the power 12 density to try to get -- power density to the extent 13 that they can. And at that point, what you're limited 14 by is your heat exchanger tube walls and how much 15 vibration you're getting, which is similar to light 16 water reactors.
17 And you can talk -- some of the designs, 18 the largest ones I've seen are about 300 megawatts per 19 cubic meter, and things are whipping at that point, 20 and you're limited by pump -- what's your pump speeds, 21 what are your tube vibrations.
22 On the other hand, the thermal spectrum 23 ones tend to be ten or 15 megawatts per cubic meter.
24 And then you're at meter or two per second, they're 25 not -- they're not huge.
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127 1 MEMBER PETTI: David, the fast systems' 2 erosion could be a concern?
3 MR. HOLCOMB: Yes, erosion is a concern.
4 That is one of the, you know, on there, it's --
5 erosion is more if you've got suspended particles, so 6 I think, which hard particles, which chlorides tend to 7 dissolve things very well. And you tend to filter 8 things. So probably less than you would think on 9 there, but it is a certainly a non-zero thing on your 10 concerns on fast systems.
11 They are really pumping these things quite 12 hard. Just basically because fuel salt's expensive, 13 and so they want to minimize the amount of volumes.
14 They want to up the power density.
15 And the designers are going to be driven 16 to maximizing the flow velocity, and that turns out 17 the heat exchanger, the ability of removing heat from 18 the fuel is one of the design limits on this, because 19 you don't want to operate on these huge temperature 20 margins, because that drives corrosion.
21 And so if you're only operating on, you 22 know, 50 C temperature -- across the core or then in 23 order to transfer that heat, you've got to flow a lot 24 of coolant. And so it's very similar to water in some 25 ways.
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128 1 MEMBER PETTI: So David these -- but is 2 anybody proposing, you know, the micro heat exchangers 3 that have, you know, small tubes or passages? I 4 always worry about for salt --
5 MR. HOLCOMB: Thus far I've seen much more 6 classical things in all proposals. On tube and shell, 7 the fanciest thing is twisted tubes because you do 8 want to enhance the turbulence within them, on there.
9 But mostly these things are classic tube and shell.
10 Part of this is just the materials, you 11 have to make a single material because dissimilar 12 material corrosion is a major corrosion thing in 13 liquid salt. So you will very much want to make all 14 of your salt-wetted stuff out of very similar 15 materials.
16 And you -- and so it is unlikely -- I 17 don't believe that small passage heat exchangers are 18 going to be likely in molten salt reactors. No one 19 has proposed one yet.
20 MEMBER PETTI: Good, okay, thanks.
21 MR. HOLCOMB: That Kairos might end up 22 with something like that. There may be a solid fuel, 23 and that still is an MSR. It's just I don't always 24 thinking just liquid fuel. It's a possibility you 25 might be able to do that with a clean salt.
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129 1 MEMBER PETTI: Keep going, Dave, then.
2 MR. HOLCOMB: Okay, next slide. Last 3 slide anyway, is just basically we, here's the ML 4 number, it's available for review and comments.
5 Providing us suggestions, you can provide at any time.
6 We really have not gotten, I'm surprised 7 that, you know, Chris can comment if he's gotten 8 anything lately. But NEI, you know, none of the usual 9 suspects have gone ahead and provided us substantive 10 comments thus far.
11 And I'm not sure if that means that 12 they're just not watching this, or, but because we 13 have been socializing this as a concept for a fair 14 amount of time that's, and we're try to listen when 15 people have suggestions, and perhaps we've addressed 16 many of the comments.
17 But that's why we're, again, there's a 18 workshop on molten salts. We're in a -- we're, next 19 week, you know, indicating please review this there.
20 We had the large MSR workshop, which had I think over 21 400 people listening to my presentation on this who 22 are part of the stakeholder community the second week 23 of October. So we are actively seeking comments on 24 this and really don't have the level of comments that 25 I saw from the last -- on the last presentation.
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130 1 I'll leave it open to Chris if he has 2 anything further to say about comments.
3 MR. VAN WERT: Yeah, I don't have too much 4 to add to that, other than we have not received any 5 from outside. We do have a few comments which, you 6 know, we've previously discussed from internally 7 speaking with Tim Drzewiecki and Alex Trusk 8 (phonetic).
9 But yeah, to date externally we have not 10 received anything. And we have been in communication 11 with EPRI and others.
12 MEMBER PETTI: Well, you'll definitely get 13 comments from us, so.
14 Well, David, thank you. I think this was 15 a nice overview. At this point before we go around 16 and give comments from members, let's open up -- get 17 members of the public comments if there are any. So 18 if there are any members of the public, unmute 19 yourself, star 6 on Teams, identify who you are, and 20 provide your comment.
21 Okay, not hearing anything. Members, any 22 other comments?
23 MEMBER BLEY: Again, this is Dennis. I'd 24 just like to thank David. It was a great 25 presentation, and for me it was pretty much a 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
131 1 tutorial. So I learned a lot today. Thanks, Dave.
2 MEMBER PETTI: Yeah, I think that the 3 subcommittee meeting where we went into great, much 4 more detail was very good, very helpful for me to put 5 the letter together in a succinct manner, so.
6 MR. HOLCOMB: All right, thank you.
7 MEMBER PETTI: Thanks. Okay, so not 8 hearing comments from members, Matt, shall we just 9 keep on going? Because I can certainly read it, we 10 can read in the letter.
11 CHAIR SUNSERI: Yes, Dave, I think that 12 would be a good approach. If we need a short 13 transition period here, we can do that. But why don't 14 you go ahead and bring -- ask Sandra to bring up the 15 letter report, we can read it in. Maybe that'll give 16 us a little bit longer break this afternoon before we 17 get into the researcher part.
18 MEMBER PETTI: Yeah.
19 CHAIR SUNSERI: And I will echo Dennis's 20 comments, I thought that was an excellent 21 presentation. So I learned so much, thank you.
22 So the next thing on my note is, is that 23 yes, dismiss the Court Reporter. So thank you, thank 24 you for prompting that. But we are done. In fact, we 25 have completed -- we won't need your services for the 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
132 1 rest of the meeting this week, so.
2 (Whereupon, the above-entitled matter went 3 off the record at 2:02 p.m.)
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Draft NUREG-2246 Fuel Qualification for Advanced Reactors Meeting with the Advisory Committee on Reactor Safeguards November 3, 2021 1
Outline
- Background
- Brief Review of Fuel Qualification Assessment Framework
- Results of Public Comment Period (Changes to NUREG-2246)
- Next Steps 2
Background
- Early Stakeholder Engagement
- Framework presented at May 7, 2020, periodic advanced reactor stakeholder meeting
- Draft white paper released in support of October 1, 2020, periodic advanced reactor stakeholder meeting
- International coordination with the Nuclear Energy Agency (NEA) -
Working Group on the Safety of Advanced Reactors (WGSAR)
- Regulatory Perspectives on Nuclear Fuel Qualification for Advanced Reactors
- Draft NUREG-2246 is an iteration of draft white paper, with adjustments to address feedback received at stakeholder meetings and NEA-WGSAR input 3
Purpose and Considerations
- NUREG-2246 provides a framework for evaluating a nuclear fuel design (power and non-power reactors) and attempts to enable a transparent, efficient, and thorough safety review
- Informed by staff experience gained from licensing solid fuel reactor designs (particularly LWR designs), advanced reactor fuel testing performed to-date, and the accelerated fuel qualification (AFQ) considerations
- Focused on areas where irradiated fuel tests have been required 4
Purpose and Considerations
- Development of a generic assessment framework for fuel qualification
- Top-down approach used to decompose the top level goal of fuel is qualified into lower level supporting goals
- Lower level supporting goals are further decomposed until clear objective goals are identified that can be satisfied with direct evidence
- An attempt was made to develop generically applicable criteria Some criteria may not be applicable to all fuel types or reactor designs Criteria may not be sufficient in some cases
- Additional activity
- Separate guidance being developed for molten salt reactors
- NUREG-2246 is being exercised for a generic assessment of metal fuel (Idaho National Lab) and TRISO fuel (Pacific Northwest National Lab) 5
NUREG-2246, Comment Submittal Received
- Draft NUREG-2246, Fuel Qualification for Advanced Reactors
- FRN published on June 30, 2021
- Three comment submittals received
- (1) Public, ML21243A353
- (2) Nuclear Energy Institute (NEI), ML21243A356
- (3) Public, ML21246A124
- Public meeting held September 29 in response to NEIs comment submittal request 6
Outline
- Background
- Brief Review of Fuel Qualification Assessment Framework
- Results of Public Comment Period (Changes to NUREG-2246)
- Next Steps 7
FQ Assessment Framework: Goal Goal: Fuel is qualified for use
= Reasonable assurance exists that the fuel, fabricated in accordance with its specification, will perform as described in the safety analysis.
Goal: Fuel is qualified for use A fuel manufacturing specification controls the key Safety criteria can be fabrication parameters that satisfied with high significantly affect fuel confidence [G2]
performance [G1]
8
G2: Safety Criteria Safety criteria can be satisfied with high confidence [G2]
Margin to design limits can be Margin to radionuclide demonstrated under conditions release limits under accident Ability to achieve and of normal operation, including conditions can be maintain safe shutdown can the effects of anticipated demonstrated with high be assured [G2.3]
operational occurrences with confidence [G2.2]
high confidence [G2.1]
10 CFR 50.34(a)(1)(ii)(D) GDC/ARDC 2 GDC/ARDC 10 10 CFR 52.47(a)(2)(iv) GDC 27/ARDC 26 10 CFR 52.79(a)(1)(vi) GDC/ARDC 35 9
G2.1: Design Limits for Normal and Anticipated Operational Occurrences Margin to design limits can be demonstrated under conditions of normal operation, including the effects of anticipated In NUREG-2246, base goals are identified by operational occurrences with the use of grey boxesevidence must be high confidence [G2.1]
provided to demonstrate that the base goal is satisfied.
An evaluation model is available to assess fuel performance The fuel performance envelope against design limits to protect is defined [G2.1.1] against fuel failure and degradation (i.e., life-limiting) mechanisms [G2.1.2]
Note: The fuel performance envelope specifies the environmental conditions and radiation exposure that the fuel is expected to encounter. The envelope is typically specified by fuel designers and provides constraints on the design of the reactor and associated systems.
10
GOAL Fuel is qualified for use GOAL Evaluation model is acceptable for use G1 Fuel is manufactured in accordance with a specification EM G1 Evaluation model contains the appropriate modeling capabilities G1.1 Key dimensions and tolerances of fuel components are specified EM G1.1 Evaluation model is capable of modeling the geometry of the fuel system G1.2 Key constituents are specified with allowance for impurities EM G1.2 Evaluation model is capable of modeling the material properties of the fuel G1.3 End state attributes for materials within fuel components are specified or system otherwise justified EM G1.3 Evaluation model is capable of modeling the physics relevant to fuel G2 Margin to safety limits can be demonstrated performance G2.1 Margin to design limits can be demonstrated under conditions of normal EM G2 Evaluation model has been adequately assessed against experimental data operation and AOOs EM G2.1 Data used for assessment are appropriate (see ED Assessment G2.1.1 Fuel performance envelope is defined Framework)
G2.1.2 Evaluation model is available (see EM Assessment Framework) EM G2.2 Evaluation model is demonstrably able to predict fuel failure and G2.2 Margin to radionuclide release limits under accident conditions can be degradation mechanisms over the test envelope demonstrated EM G2.2.1 Evaluation model error is quantified through assessment G2.1.1 Fuel performance envelope is defined against experimental data G2.2.1 Radionuclide retention requirements are specified EM G2.2.2 Evaluation model error is determined throughout the fuel G2.2.2 Criteria for barrier degradation and failure are suitably conservative performance envelope (a) Criteria are conservative EM G2.2.3 Sparse data regions are justified (b) Experimental data are appropriate (see ED Assessment EM G2.2.4 Evaluation model is restricted to use within its test envelope Framework)
G2.2.3 Radionuclide retention and release from fuel matrix are modeled conservatively GOAL Experimental data used for assessment are appropriate (a) Model is conservative ED G1 Assessment data are independent of data used to develop/train the evaluation model (b) Experimental data are appropriate (see ED Assessment ED G2 Data has been collected over a test envelope that covers the fuel performance Framework) envelope G2.3 Ability to achieve and maintain safe shutdown is assured ED G3 Experimental data have been accurately measured G2.3.1 Coolable geometry is ensured ED G3.1 The test facility has an appropriate quality assurance program (a) Criteria to ensure coolable geometry are specified ED G3.2 Experimental data are collected using established measurement techniques (b) Evaluation models are available (see EM Assessment ED G3.3 Experimental data account for sources of experimental uncertainty Framework) ED G4 Test specimens are representative of the fuel design G2.3.2 Negative reactivity insertion can be demonstrated ED G4.1 Test specimens are fabricated consistent with the fuel manufacturing (a) Criteria are provided to ensure that the means to insert specification negative reactivity are not obstructed ED G4.2 Distortions are justified and accounted for in the experimental data (b) Evaluation model is available (see EM Assessment Framework) 11
Outline
- Background
- Brief Review of Fuel Qualification Assessment Framework
- Results of Public Comment Period (Changes to NUREG-2246)
- Next Steps 12
Outline of Highlighted Comments Comment Topic Comment Topic NEI-1, NEI-24, Non-LWR examples NEI-17 TRISO manufacturing Public 3-1 NEI-5 Role of research literature NEI-18 Safe shutdown Regulatory basis for fuel NEI-7 qualification NEI-23 Coolable geometry Scope of degradation NEI-9 NEI-26 Control element insertion mechanisms NEI-10 GDCs/ARDCs Test envelope and NEI-29 Performance envelope NEI-14 Fuel safety functions NEI-30 Quality assurance NEI-16 First core applications 13
NEI Comment #1 and #24 and Public Comment 3-1, General*
There are numerous advanced reactor designs, with many different fuel designs, and each fuel design has its own unique challenges and advantages. This draft NUREG has a lot of guidance heavily based on existing LWR fuel designs, which may not be applicable to all advanced reactor designs. Please make the guidance more applicable to non-traditional fuel designs.
Please add examples for non-traditional LWR fuel designs.
Response Summary:
- Staff acknowledges that NUREG-2246 is informed by lessons-learned from experience with LWR fuel but disagrees with the characterization that it is based on existing LWR fuel designs.
- Section 1.3, Scope, states that assessment criteria draws from results from advanced reactor fuel testing performed to-date, and accelerated fuel qualification (AFQ) considerations
- On-going work to exercise NUREG-2246 framework through generic assessments of metal fuel (Idaho National Lab) and Tristructural Isotropic (TRISO) fuel (Pacific Northwest National Lab) 14
NEI Comment #5, Page 1-1 The NUREG primarily references the Crawford report when establishing the objective of fuel qualification and its corresponding basis. A technical paper (the Crawford report) does not establish a regulatory basis and is not appropriate to establish the regulatory need for fuel qualification.
Furthermore, the noted economic operation in the Crawford report is not something that NRC should be regulating on.
Please replace the reference of a technical paper with a regulatory one (when identified as a means to do so) and remove reference to economics as a regulatory goal.
Response Summary:
- Staff disagrees with the characterization that a technical paper served as a primary basis for NUREG-2246, but acknowledges that the research by Crawford, Porter, Hayes, Meyer, Petti, and Pasamehmetoglu informed their judgement on an applicable definition of qualified fuel, for use in NUREG-2246.
- Staff agrees that the referenced research can be better characterized in NUREG-2246 to prevent misunderstanding regarding the use of the research literature in the development of regulatory guidance, and corresponding changes were made.
15
NEI Comment #7, Page 1-1 The text states "this framework relies on regulatory requirements that are applicable to applications for design certifications, combined licenses, manufacturing licenses, or standard design approvals."
However, fuel qualification itself is not required for any of the mentioned licensing approvals. Fuel qualification is therefore only necessary to meet the requirements in Section 2.1 to the extent that the fuel is specifically relied upon as a safety feature.
Please clarify the connection of fuel qualification to the noted licensing approvals, or modify the text to more clearly denote more context to how potentially applicable requirements would inform what is necessary for fuel qualification.
Response Summary:
- Staff recognizes that the term fuel qualification is not explicitly defined or used in NRC regulations.
- There are regulatory requirements generically applicable to reactor licensing applications that are generally associated with nuclear fuel behavior and its role in preventing the release of radioactive material under conditions of normal operation, including the effect of anticipated operational occurrences and accident conditions.
- Regulatory requirements and connections to regulation is provided in Section 2.1, Regulatory Basis 16
NEI Comment #9, Page 1-2 and Section 3.1.1 Fuel life-limiting failure and degradation mechanisms are not just due to irradiation during reactor operation. Other degradation mechanisms, chemical attacks, hydrogen pickup, high temperature, and time at temperature during AOOs or Design Basis Accidents also impact fuel performance.
Please remove "due to irradiation" to expand the applicability of the statement to include other failure mechanisms.
Response Summary:
- Propose change from due to irradiation to due to irradiation and irradiation assisted phenomena.
- Agree that there are degradation mechanisms beyond irradiation
- Primary obstacle to qualifying nuclear fuel has generally been demonstrating fuel performance at the desired exposure
- most fuel degradation phenomena are impacted by irradiation 17
NEI Comment #10, Section 2.1*
The regulatory basis denoted is 50.43(e) and the design criteria (GDC and ARDC). However, the GDC and ARDC are not requirements for, and as guidance are not required to be met by, non-LWRs. Thus, non-LWRs may choose to develop PDCs through another method. The guidance should clarify that fuel qualification is only necessary if it is determined to be one of the PDCs for the design, based upon the fuel being relied upon as a safety feature.
Please clarify the text to indicate how fuel qualification could be used to demonstrate compliance to 50.43 but is not necessary if fuel is not relied upon as a safety feature. Additional context on how potentially applicable requirements would inform what is necessary for fuel qualification would be helpful.
Response Summary:
- Agree that GDCs and ARDCs are not necessarily requirements for non-LWRs but are instead considered guidance for non-LWR advanced reactor applicants in developing proposed PDCs.
- The cited GDC/ARDC are associated with safety functions that generally involving nuclear fuel.
These safety functions are not otherwise captured in NRC regulations (e.g., fuel design limits, maintaining coolable geometry) and are expected to be addressed as part of fuel qualification.
- Revisions made to Section 2.1 to accurately reflect requirements associated with PDCs 18
NEI Comment #14, Section 2.2.3 The following text is misleading because fuel may have safety functions as noted in the text, but it is not required to. It is possible to not credit the fuel and instead credit other mechanisms outside of the fuel matrix. Fuel qualification is therefore only necessary to meet the requirements in Section 2.1 to the extent that the fuel is specifically relied upon as a safety feature.
"Fuel qualification partially addresses the fundamental safety functions of control of reactivity, cooling of radioactive material, and confinement of radioactive material" Please clarify the role of fuel qualification and its necessity only if being relied upon and/or credited in the safety analysis as some designs may not. Additional context on how potentially applicable requirements would inform what is necessary for fuel qualification would be helpful.
Response Summary:
- Staff recognizes that the role of fuel in the protection against the release of radioactivity can vary depending upon the reactor design.
- Updated Section 2.2.3 to clarify that nuclear fuel contributes to the reactivity balance and is a source of heat generation and fission products. Therefore, nuclear fuel is generally recognized as impacting the fundamental safety functions of reactivity control, heat removal, and confinement of radioactive material.
19
NEI Comment #16, Section 2.4 and Section 3.4.2*
The text here on lead test specimen programs is applicable only if we had existing/operating advanced reactors. It does not discuss alternatives for fuel to be qualified for first core applications where lead test specimens are not possible.
Please add information on fuel qualification for first core applications.
Response Summary:
- Added a new Section 2.5, First Core Applications
- 10 CFR 50.43(e) generally applies to fuel because fuel generally impacts the safety functions of reactivity control, heat removal, and confinement of radioactive material.
- Data may be obtained from test reactors (e.g., ATR, TREAT) provided that the tests and associated data are appropriate for assessing evaluation models.
- NUREG-2246 accommodates the use of a lead test specimen program beyond what has been traditionally used for LWRs.
- 10 CFR 50.43(e)(2) allows the use of a prototype plant to comply with testing requirements.
20
NEI Comment #17, Section 3.1.3 The TRISO SER allows for manufacturing independence as long as the final product has properties that fall within the specification range. Please note TRISO as an example of "insensitivity to manufacturing processes."
Please add text to denote that the TRISO is an example of fuel that has an insensitivity to manufacturing processes and instead measurable criteria can be used to justify predicted performance.
Response Summary:
- Revise Sections 3.1 and 3.1.3 to reference the EPRI TRISO Topical Report and associated safety evaluation report, reflecting that key end-state parameters for TRISO particles have been identified that provide assurance of fuel performance during normal operation 21
NEI Comment #18, Figures 3-3 and 3-8, Section 3.2.3*
Criterion G2.3 includes a statement for the "ability to achieve and maintain safe shutdown can be assured." The NUREG further defines safe shutdown as "a state in which the reactor is subcritical, decay heat is being removed, and radionuclide inventory is contained." However, safe shutdown and safe state are not interchangeable. Not all reactors must be subcritical to be safe and therefore it is not necessary for all fuel types to be subcritical. Industry recommends aligning the NUREG with other documentation that use the phrase "a safe stable end-state" instead.
Please change criterion G2.3 to "Ability to achieve and maintain a safe, stable, end state" and revise the text throughout to be consistent with this revised criterion.
Response Summary:
- Relatively recent NRC policy papers have clarified that maintaining subcriticality with only safety-related structures, systems, and components may not be required (SECY-18-0099)
- Staff expects that nuclear fuel be designed such that forces on the nuclear fuel, resulting from internal or external events, will not preclude the eventual achievement of a subcritical state
- No changes made in response to this comment.
22
NEI Comment #23, Page 3-8 No specific criterion is set as to what the term "coolable geometry" means for non-traditional LWR fuel designs. For example, some advanced reactor fuel designs like the MSFR and the MCFR are planning on using liquid salt with fissile product as both their coolant and their fuel, which would require clarification/flexibility on the definition of "coolable geometry."
Please clarify what a coolable geometry criterion would be for fuel designs that do not have a containment (e.g., LWR fuel cladding) and how this will ensure ability to attain safe, stable, end state.
Response Summary:
- Section 3.2.3.1.1, G2.3.1(a) - Identification of Phenomena provides examples of the types of phenomena that could cause a loss of coolable geometry.
- Staff recognizes that these criteria cannot be specified generically for all fuel designs
- Section 1.3, Scope, clarifies that some criteria may not apply to liquid fuel forms (e.g., MSR fuel), and these fuel forms may require additional or alternative criteria.
23
NEI Comment #26, Page 3-10 For designs that do not have neutron control element insertion (e.g., control drums),
having criteria to ensure control element insertion paths would not be necessary.
Please revise text to indicate criteria should be specified only for designs with neutron control elements whose insertion is credited in accident response models.
Response Summary:
- Section 3.2.3, G2.3-Safe Shutdown, of NUREG-2246 was updated to replace control element insertion with negative reactivity insertion.
- Staff recognizes that some criteria may not be applicable to all fuel types or reactor designs.
- NRC staff notes that the use of control drums, as provided in the commenters example, does not necessarily ensure the ability to insert negative reactivity.
24
NEI Comment #29, Page 3-16 The text does not address methods for justifying when fuel can be used beyond its performance envelope when lead test specimens are not available.
Please add information on what adequate justification is needed to expand the performance envelope using experimental data without the use of lead test specimens.
Response Summary:
- Staff is unable to provide generic guidance to address all potential scenarios where fuel use beyond its performance envelope may be requested. However, some information related to the use of an evaluation model outside of its test envelope is provided in Section 3.3.2.2.4, EM G2.2.4- Restricted Domain
- Application of an evaluation model outside of the supporting test envelope (see Section 3.4.2) may be justified based on physical arguments (e.g., that the evaluation model provides a simplified or bounding treatment of physical phenomena). Justification for extrapolation of a model outside of the test envelope is strengthened by the use of physics-based models, such as those discussed in Section 2.3, which are informed by fundamental information about fuel evolution and behavior, as opposed to empirically derived models (Terrani, et al., 2020).
25
NEI Comment #30, Page 3-17 ASME NQA-1 is not the only way to qualify fuel data. For data collected at national laboratories, the application of this standard may not be possible, despite the national laboratories using alternative and acceptable quality assurance methods. NRC should accept data from the technical experts at national laboratories if the data was collected under the lab's QA program as noted in ML20054A297, where NRC staff determined that Argonne National Lab's quality assurance program plan is based on the method provided in ASMEs NQA-1-2008/2009 and satisfies the quality assurance requirements of Appendix B to 10 CFR Part 50.
Please either remove or modify the text to allow for data to also be qualified under the commercial grade dedication (CGD) process rather than stating data must be made compliant.
Response Summary:
- Revised Section 3.4.3.1 to clarify that approaches other than those provide in ASMEs NQA-1, including CGD, may be acceptable means for justifying that data is collected under an appropriate QA program 26
Next Steps
- Resolve comments from internal review and ACRS
- Additional public meeting(s), if needed
- Issue final NUREG-2246
- Expected to be published in February 2022
- Stakeholder/ACRS engagement on on-going work to exercise NUREG-2246 frameworkmetal fuel and TRISO fuel 27
US MSR Fuel Salt Qualification Process NRC - Advisory Committee on Reactor Safeguards David Holcomb, George Flanagan, and Mike Poore November 3rd, 2021 ORNL is managed by UT-Battelle, LLC for the US Department of Energy
Fuel Qualification is an Element in Achieving Sufficient Understanding of Fuel Behavior Fuel qualification is a process which provides high confidence that physical and chemical behavior of fuel is sufficiently understood so that it can be adequately modeled for both normal and accident conditions, reflecting the role of the fuel design in the overall safety of the facility. Uncertainties are defined so that calculated fission product releases include the appropriate margins to ensure conservative calculation of radiological dose consequences.
- NRC Presentation on Possible Regulatory Process Improvements for Advanced Reactor Designs, August 3rd, 2017 (ML17220A315) 2 ACRS Full Committee November 3, 2021
Liquid Fuel Salt Qualification Builds From Advanced Reactor Assessment Framework
- Liquid salt fuel assessment framework employs goal decomposition process parallel to NUREG-2246
- Success criteria derive from fundamental safety functions
- Dozens of MSR design variants under consideration
- Nearly all developed over the past decade
- Which designs will be presented for regulatory safety adequacy review over the next decade is uncertain
- Fuel salt qualification process based on fuel salt chemistry and physics and is largely independent of reactor configuration 3 ACRS Full Committee November 3, 2021
Liquid Fuel Has Substantial, Fundamental Differences From Solid Fuel
- Liquid salt fuel Liquid Fuel Solid Fuel
- Serves as nuclear fuel and primary heat Chemically damageable -
Mechanically damageable transfer media may be reparable during use
- Must meet requirements for both Composition may be adjustable during use Composition set prior to use purposes Properties depend on Properties depend on composition and state fabrication process Container breach could release nearly all radionuclides 4 ACRS Full Committee November 3, 2021
Common Salt Properties and Plant Functions Enable a General Liquid Fuel Salt Evaluation Method
- Specific accident sequences are design dependent
- Basic operational and fundamental safety functions are common to any nuclear power plant
- Halide salt characteristics are common to any MSR
- High boiling points (low pressure)
- Low Gibbs free energy (low chemical potential energy)
- Natural circulation heat transfer properties
- Fuel salt interacts with its container layers via common chemical and physical mechanisms - for example via
- Thermal energy transfer, chemical reactions, and mechanical processes 5 ACRS Full Committee November 3, 2021
Key Issue is What Constitutes Fuel Salt?
- Fuel salt does not come in discrete elements (rods or assemblies) and moves independently of its container during normal operations
- Cladding and fuel assembly structures are qualified as part of solid fuel
- Fuel salt includes all of the material containing fissionable elements or radionuclides that remain in hydraulic communication, but does not include the surrounding systems, structures, or components
- Salt vapors and aerosols remain part of the fuel salt system until they become adequately trapped
- Container corrosion products become part of the fuel salt
- Fresh and used fuel salt in on-site storage are within scope 6 ACRS Full Committee November 3, 2021
Functional Containment is Important to How MSRs Provide Adequate Radionuclide Retention
- Barrier performance must be degraded to release radionuclides into the environment
- Performance degradation can occur through failure or bypass
- Fuel salt properties that stress barriers cause them to be more likely to release radionuclides - for example
- Increased temperature increases radionuclide vapor pressure in cover gas and well as decreasing strength of container
- Different performance requirements for materials normally in contact with salt versus those that only need to withstand accidents 7 ACRS Full Committee November 3, 2021
Fuel Salt Properties Have Substantial Impact on Containment Performance
- Normal operations
- Salt seeking radionuclides are chemically retained
- Fission gases (with half lives more than a few seconds) largely escape
- Noble (insoluble) metals largely either plate out or escape into vapor
- Fuel salt causes stress on, potentially resulting in damage to, container materials (e.g.,
via corrosion, erosion, creep, etc.)
- Tritium behavior depends on operations and redox state
- Chemical configuration (free or bound) depends on redox
- Accident conditions
- Mechanistic analysis of radioactive material transport depends on fuel salt properties
- Substantial reduction in cover gas heat content and radiotoxicity over first couple of days - MSBR predicted 99.9% reduction after 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> (ORNL-4396)
- High potential consequences of large, early cover gas releases 8 ACRS Full Committee November 3, 2021
Fuel Salt Boundary Breach Accident Progression Part of Performance Based and Deterministic Fuel Qualification
- Multiple locations in the Code of Federal Regulations require evaluation of a postulated fission product release from core into containment
- Fuel salt or cover gas cannot directly stress exterior containment layers without first breaching an inner containment layer
- High radiation and high temperatures immediately outside fuel salt boundary substantially circumscribes characteristics of materials adjacent to fuel salt container
- Focus is on fuel salt properties that must be known to adequately model accident progression and interaction characteristics with materials within containment 9 ACRS Full Committee November 3, 2021
Fuel Related Advanced Reactor Requirements Are Similar for Liquid and Solid Fuel
- Example
- 10 CFR 50.43(e)(1)(i) requires that the performance of each safety feature of the design has been demonstrated through either analysis, appropriate test programs, experience, or a combination thereof
- Fuel salt thermophysical and thermochemical properties provide the information necessary to model its role in enabling plant safety features to perform safety functions
- Fuel salt properties vary with both composition and temperature
- Fuel salt properties need to be determined across the range of temperatures and compositions that span potential operational and accident conditions
- Quality of the fuel salt property data needs to be sufficient to enable modeling the role of the fuel salt in achieving the plant FSFs 10 ACRS Full Committee November 3, 2021
Liquid Salt Fuel Assessment Framework Follows Template Developed for Solid Fueled Advanced Reactors
- Top-down approach used to decompose top level goal of fuel is qualified to lower level supporting goals
- Qualifying fuel develops high confidence that the fuel will adequately perform its role in enabling the facility to achieve its safety objectives
- Lower level supporting goals are further decomposed until clear objective goals are identified that can be satisfied with direct evidence 11 ACRS Full Committee November 3, 2021
Qualification is Based Upon Understanding the Chemical and Physical Properties of Representative Fuel Samples
- Liquid state significantly changes the physical behavior of fuel
- Liquids do not accumulate internal stresses
- No history dependent properties
- Flow homogenizes fluid properties
- No position dependent properties
- No size dependent properties
- Chemical and physical properties are set by elemental composition and temperature
- Independent of isotopic content Small minimally-radioactive liquid fuel salt samples provide representative physical and chemical properties 12 ACRS Full Committee November 3, 2021
Liquid Fuel Salt Qualification Establishes Acceptable Salt Composition Range That Maintains Safety Functions
- Liquid fuel salt is a Newtonian fluid
- Heat transfer and fluid flow behave in well known manners
- Continuous variance in physical properties with composition
- Reasonable assurance of adequate protection derives from a combination of measured salt composition and knowledge of resulting chemical and physical properties
- A liquid fuel salt property database would capture the relationship between fuel salt composition and properties 13 ACRS Full Committee November 3, 2021
Liquid Fuel Salt Property Database Relates Composition to Physical and Chemical Properties to Aid Developers
- Database development underway sponsored by DOE-NE
- Salt property measurement program in progress
- Not currently including minor constituent transuranic elements (Am, Cm)
- Requires appropriate quality assurance for both new and existing data
- Database initially sparsely populated
- Safety evaluations / accident models performed with bounding values to establish acceptable performance range
- Additional data added to database over time
- Goal is to eventually only require salt composition and temperature measurement at operating plants and look up properties from database 14 ACRS Full Committee November 3, 2021
Fuel Salt Properties Support Modeling Reactor Performance Under Normal and Accident Conditions
- Heat transfer in Newtonian fluids is determined primarily by density, viscosity, and heat capacity
- Thermal conductivity and radiative heat transfer parameters can become important in specialized situations 15 ACRS Full Committee November 3, 2021
Fuel Salt Supports the Plant SSCs in Achieving the FSFs and Regulatory Requirements
- Qualification focuses on identification and understanding of fuel salt property degradation mechanisms that occur as a result of irradiation during reactor operation
- Property repair (composition adjustment) may be incorporated into normal operation
- During normal operations and AOOs fuel salt properties must result in sufficient margin from damage to safety-related SSCs
- Under accident conditions the fuel salt properties must not result in sufficient damage to safety-related SSCs to prevent them from achieving their function 16 ACRS Full Committee November 3, 2021
Fuel Qualification Draft NUREG/CR (ML21245A493) is Available for Review and Comment
- Suggestions for improvements to the approach can be provided at any time
- Comments and suggestions can be provided to the NRC or the authors 17 ACRS Full Committee November 3, 2021