ML22013B256
| ML22013B256 | |
| Person / Time | |
|---|---|
| Issue date: | 12/01/2021 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| Burkhart, L, ACRS | |
| References | |
| NRC-1775 | |
| Download: ML22013B256 (132) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Docket Number:
(n/a)
Location:
teleconference Date:
Wednesday, December 1, 2021 Work Order No.:
NRC-1775 Pages 1-95 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W., Suite 200 Washington, D.C. 20009 (202) 234-4433
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 UNITED STATES OF AMERICA 1
NUCLEAR REGULATORY COMMISSION 2
+ + + + +
3 691ST MEETING 4
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5
(ACRS) 6
+ + + + +
7 WEDNESDAY 8
DECEMBER 1, 2021 9
+ + + + +
10 OPEN SESSION 11
+ + + + +
12 The Advisory Committee met at the Nuclear 13 Regulatory Commission, Two White Flint North, Room 14 T2B1, 11545 Rockville Pike, at 8:30 a.m., Matthew W.
15 Sunseri, Chairman, presiding.
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
2 COMMITTEE MEMBERS:
1 MATTHEW W. SUNSERI, Chairman 2
JOY L. REMPE, Vice Chairman 3
RONALD G. BALLINGER, Member 4
VICKI M. BIER, Member 5
DENNIS BLEY, Member 6
CHARLES H. BROWN, JR., Member 7
GREGORY H. HALNON, Member 8
VESNA B. DIMITRIJEVIC, Member*
9 DAVID PETTI, Member 10 11 ACRS CONSULTANT:
12 STEPHEN SCHULTZ 13 14 DESIGNATED FEDERAL OFFICIAL:
15 ZENA ABDULLAHI 16 17 18 19 20 21 22 23 24
- Present via teleconference 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 CONTENTS 1
2 Call to Order and Opening Remarks........
4 3
Research Information Letter (RIL) for Fuel 4
Fragmentation, Relocation and Dispersal 5
During LOCA...................
9 6
Remarks from the Subcommittee Chairman 9
7 Presentations and Discussion with 8
Representatives from the NRC Staff
.... 10 9
Kimberly Webber........... 10 10 Michelle Bales
........... 12 11 Presentations and Discussion with NEI... 78 12 Public Comment Period........... 86 13 Committee Deliberation
.......... 87 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 P R O C E E D I N G S 1
8:34 a.m.
2 CHAIRMAN SUNSERI: The meeting will now 3
come to order.
4 This is the second day of the 691st 5
meeting of the Advisory Committee on Reactor 6
Safeguards. I'm Matthew Sunseri, the Chair of the 7
ACRS.
8 Members in attendance are Dave Petti, Ron 9
Ballinger, Greg Halnon, Vicki Bier, Joy Rempe, Walt 10 Kirchner, Dennis Bley.
11 Let me ask, is Vesna Dimitrijevic on the 12 line yet?
13 (No response.)
14 We expect Vesna to be joining remotely.
15 And Steve Schultz, our consultant, is also 16 in the room with us.
17 There is an accident out on the highway 18 that's preventing some members from getting here.
19 Charles Brown will be here as soon as he is safely 20 able to do so, and Scott Moore, our Executive 21 Director, and Elisha Ballinger (phonetic) are also in 22 traffic trying to get here.
23 The Designated Federal Officer for this 24 meeting is Ms. Zena Abdullahi.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
5 During today's meeting, the Committee will 1
consider the following:
2 The first topic is the Research 3
Information Letter on Fuel Fragmentation, Relocation, 4
and Dispersal During LOCA. This will be a 5
presentation followed by report preparation by the 6
Committee.
7 Secondly, we will continue with the report 8
preparation on Draft Guide 5061, which deals with 9
10 A phone bridge line has been opened to 11 allow members of the public to listen in on the 12 presentations and Committee discussions. We have 13 received no written comments or requests to make oral 14 statements from members of the public regarding 15 today's session.
16 There will be an opportunity for public 17 comment. We have set aside time in the agenda for 18 comments from members of the public attending or 19 listening to our meetings. Written comments may also 20 be forwarded to Ms. Zena Abdullahi, the Designated 21 Federal Officer.
22 A transcript of the open portion of the 23 meeting is being kept. It is requested that speakers 24 identify themselves and speak with sufficient clarity 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
6 and
- volume, so they can be readily heard.
1 Additionally, participants should mute themselves when 2
not speaking.
3 And just as a note to our agenda topic, 4
Research Biennial Review is schedule for 1:00 to 2:30 5
today, but that topic has been taken off the agenda 6
because we completed that work at our last full 7
Committee meeting. So, we will redirect that time 8
allotted for that topic to report preparation.
9 All right. This is the second day of our 10 use of what we'll call hybrid meeting format. And 11 yesterday was really, really a good experience. I 12 think we had a very good meeting. We effectively 13 demonstrated how to use this technology, but we did 14 learn some things. So, let me just cover a couple of 15 highlights from yesterday.
16 First off, for the speakers around the 17 table here, it is very difficult to hear you talk in 18 the room. Ironically, if you're outside of this room, 19 you're crystal clear. All right?
20 (Laughter.)
21 So, what we're going to ask you to do --
22 and we're working on the issue; in fact, there will be 23 some technicians behind the scenes trying to adjust 24 the gain on these microphones today. They need the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
7 full room in place to do that and the dynamics. It's 1
a balancing act between these mics and the feedback of 2
the main system. So, we do acknowledge that problem.
3 We do acknowledge that it's being worked on, and we 4
appreciate your patience as we work through that.
5 However, what I'm going to ask you to do 6
as the speakers around the table, to not only use your 7
mic here, but use your playground voices if you're 8
talking to the other kids out on the playground to 9
help us hear you until we get this fixed. All right?
10 The second thing is, I had asked all 11 participants in the room and remotely to provide 12 feedback to us, and I did get some feedback yesterday 13 from remote presenters that said, you know, they were 14 getting static or sounds of people not muting their 15 microphones, or whatever. And as it turns out, that's 16 a problem with the room microphone setup. They're 17 shuffling the papers or people are getting up and 18 moving around. These speakers are very sensitive and 19 may pick that up, and it's a distraction to the people 20 speaking remotely.
21 So, I'm going to be aware of that, and if 22 I see jostling in here, I can mute the system and cut 23 that out. We will still be able to hear them, but 24 they won't be able to hear us.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
8 But what I'm going to ask you to do is 1
let's try to minimize that distraction. And, also, as 2
a reminder, since the speakers are on all the time, 3
when you see this green light on, anything, any 4
background noise, any sidebar conversations are being 5
picked up. All right. So, just be aware that there 6
is an open mic as long as this green light up here is 7
on. All right?
8 So, I think that is it. Anybody else have 9
anything they want to share as far as lessons learned 10 from yesterday's hybrid?
11 We did fix the lights in the room.
12 MEMBER BLEY: Kudos to all who made that 13 happen. There was a temporary fix yesterday, but 14 until Maintenance comes back and puts the bulbs in, we 15 should be okay.
16 CHAIRMAN SUNSERI: Yes, our great staff 17 did a wonderful job of responding.
18 One last thing, you'll note in the room up 19 here there's this display over the main console that 20 says, "Open Right Now." That's a designation of what 21 type of meeting we are in. So, we are in an open 22 session right now. When we go to closed session, that 23 will be change to "Closed." All right? And the 24 alternation between the session and the time, if you 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
9 don't like the alternating, we can stop the time and 1
we can adjust that display. But I think it's fine the 2
way it is.
3 All right. Anything else?
4 (No response.)
5 Thank you. We will now get started with 6
the first topic, and I'll turn to Member Ron Ballinger 7
for opening remarks or introductions of the Research 8
Information Letter topic.
9 MEMBER BALLINGER:
Thank
- you, Mr.
10 Chairman.
11 Today's meeting will be a summary, I 12 believe -- actually, an expanded summary in some cases 13
-- of the Subcommittee meeting that we had on November 14 the 17th, at which point we had a fairly spirited 15 discussion of the topic and we had some spirited 16 comments from stakeholders; namely, NEI.
17 So, today's presentation, we will have a 18 presentation from the staff first, and then, NEI has 19 asked for time for a presentation. So, they will give 20 a presentation after the staff.
21 And so, with that, I think, is it 22 Michelle?
23 VICE CHAIRMAN REMPE: Ron, if you don't 24 mind, I need to interrupt for just a minute?
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
10 MEMBER BALLINGER: You can interrupt, 1
anything you want.
2 VICE CHAIRMAN REMPE: Oh, you're so kind.
3 Okay. I need to just state that I'm going 4
to have to limit my participation in some of this 5
discussion because of what might be perceived as a 6
conflict of interest on this topic. And I need to put 7
that on the record, and thank you.
8 MEMBER BALLINGER: And I add that's not an 9
advantage.
10 (Laughter.)
11 So, who is going to do the presentation?
12 Okay, Kim, the floor is yours.
13 MS. WEBBER: Okay. Good morning, Chair 14 Sunseri and Subcommittee Chair Ballinger. It's a real 15 pleasure to be in this room with you today rather than 16 in a separate or at our homes, in the offices. So, 17 I'm glad that we're part of the inaugural ACRS 18 meetings back in this room. It's really a great 19 chance to see all of you in person.
20 MEMBER BALLINGER: Yes, but I don't know 21 what kind of an advantage that is.
22 (Laughter.)
23 MS. WEBBER: My name is Kim Webber. I'm 24 the Director of the Division of Systems Analysis in 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
11 the Office of Nuclear Regulatory Research.
1 On November 17, the staff briefed the 2
Metallurgy and Reactor Fuel Subcommittee on the 3
Research Information Letter, or FIL, related to Fuel 4
Fragmentation, Relocation, and Dispersal, or FFRD. We 5
are pleased to brief the rest of the ACRS members 6
today on this important topic.
7 As you know, industry is very interested 8
in pursuing licensing of current fuel designs to 9
higher burnups. Under conditions described in the RIL 10 which include high burnup, FFRD has been observed.
11 And understanding of the mechanisms that lead to FFRD 12 represents one part of a larger analysis to evaluate 13 the safety of reactor operations using high burnup 14 fuel.
15 As you know, an assessment of the 16 thermohydraulic behavior of the reactor coolant under 17 loss of coolant accident, or LOCA, conditions and the 18 consequences of any potential fuel dispersal following 19 a LOCA are two other really important parts of the 20 safety analysis.
21 The purpose of the RIL is to document and 22 communicate to NRR the research that exists to date on 23 the mechanisms of FFRD, and it provides insights 24 regarding the basis for the empirical limits. It does 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
12 not include a LOCA analysis or an assessment of the 1
consequence of the potential for fuel dispersal into 2
the coolant.
3 In the past, RILs have been used to 4
support the development of regulatory guidance. In 5
this
- case, the determination to develop that 6
regulatory guidance, or any guidance associated with 7
high burnup or FFRD, lies with NRR. My staff have 8
been working very close with their NRR counterparts, 9
and we do have staff from NRR in the audience today.
10 So, they've discussed the body of research that is 11 currently available, and they continue to monitor the 12 research activities, and through their involvement in 13 many of the different international programs involving 14 high burnup.
15 So, unless there's any questions, I'd like 16 to turn the presentation over to Michelle Bales.
17 MS. BALES: Thank you, Kim.
18 My name is Michelle Bales. I work in the 19 Office of Research, and I will be presenting, along 20 with my colleague Lucas Kyriazidis, the Research 21 Information Letter 2113.
22 Next slide.
23 CHAIRMAN SUNSERI: Yes, and if you could 24 bring this (referring to the microphone) as close to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
13 you.
1 MS. BALES: Okay.
2 CHAIRMAN SUNSERI: It's got a little bit 3
of a cord. You can bring it a little closer.
4 MS. BALES: Is that better?
5 CHAIRMAN SUNSERI: Yes.
6 MS. BALES: Okay.
7 CHAIRMAN SUNSERI: But turn it on.
8 (Laughter.)
9 MS. BALES: Oh, man, this thing is very 10 sensitive.
11 CHAIRMAN SUNSERI: It's sensitive.
12 MS. BALES: Can you touch anywhere to --
13 CHAIRMAN SUNSERI: The green light, or red 14 light.
15 MS. BALES: There.
16 CHAIRMAN SUNSERI: There. Thank you.
17 MS. BALES: Hopefully, that will be the 18 biggest stumbling block here.
19 CHAIRMAN SUNSERI: Hopefully, yes.
20 (Laughter.)
21 MS. BALES: Okay. So, the presentation 22 today will start with history of FFRD. I'll go into 23 programs that are cited in the RIL, as well as the 24 peer review process that we used. I'll speak to the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
14 outcome of the RIL; in other words, how the RIL could 1
be used, and then, dive into the basis for the 2
empirical limits, and then, finish with some other 3
matters.
4 So, first, the history.
5 I actually want to warn Kim there is a lot 6
of animation here. So, I might be telling you to 7
click again.
8 MS. WEBBER: Yes.
9 MS. BALES: So, this is the slide, 10 correct?
11 Our Research Information Letters have been 12 used for a variety of purposes. I want to spend just 13 one minute explaining why we chose a Research 14 Information Letter for this set of information.
15 They're a tool, and as our public website 16 explains, they are a tool that is used for internal 17 communication from the Office of Research to a 18 licensing office to provide a concise summary that 19 makes it easier for the regulatory offices to process 20 and utilize complex information. That seemed to fit 21 the mold in this case.
22 If you would go to click one more time?
23 In addition, in the fuels area, RILS have 24 been used a couple of times. First, in 2004, there 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
15 was a RIL written to summarize a large body of 1
research relating to reactivity-initiated accidents.
2 And then, in 2008, there was a RIL written for the 3
large radio research on cladding embrittlement under 4
LOCA conditions. In both cases, guidance for proposed 5
rulemaking followed.
6 And if you click one more time? Right.
7 The RIL, as I said, there's a lot of 8
information that is summarized in the RIL. It's broad 9
in scope. It's difficult to understand the 10 experiments on their face value, and it would be very 11 time-consuming to digest all of it. So, all of the 12 images sort of just represent the complexity of the 13 information that is presented.
14 And one more click.
15 MEMBER HALNON: Michelle, why not a NUREG 16 or something to that effect that is a report and a 17 process more attuned to passing complex information?
18 MS. BALES: I think a NUREG certainly 19 would have been an acceptable choice. A Research 20 Information Letter is a particular tool to communicate 21 the regulatory context to a program office or to a 22 licensing office. So, it seemed to fit in this case.
23 They've been used for a variety of 24 applications the same way NUREGs have. To be honest, 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
16 I think some of it came from the fact that they have 1
been used in the fuels area in the past, as I 2
mentioned, in 2004 and 2008.
3 MEMBER BALLINGER: For one reason or 4
another, I don't have this presentation. Does 5
everybody else have it?
6 MS. BALES: There are three new slides 7
relative to the Subcommittee presentation. So, this 8
is one of them. During the Subcommittee discussion, 9
there were some questions, I think, about what a RIL 10 was and why it was chosen. So, I added this slide to 11 help that discussion.
12 MEMBER BALLINGER: Can we make sure that 13 Zena gets a copy of this?
14 MS. BALES: Absolutely, yes.
15 MEMBER BALLINGER: And I have a question.
16 Normally, Research does work in response to a user 17 need.
18 MS. BALES: Uh-hum.
19 MEMBER BALLINGER: And I've asked for the 20 user need, but we haven't got it. Is there a user 21 need for this? And if there is one, can we get it?
22 MS. BALES: Okay. So, Research often does 23 work in response to user needs, but it's not the only 24 occasion that research is conducted. In the case of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
17 the information that's contained in the RIL, the SCIP, 1
Cladding Integrity Program, for example, it is not 2
mentioned in a user need. We participated in that 3
program, that international joint project, as part of 4
the research -- what do you call it? I guess it's 5
just a research plan, but it's, in general, the Office 6
of Research participates in a lot of international 7
programs outside of specific user need requests.
8 Having said that, as we got further along, 9
and particularly, in preparation for high burnup 10 applications, there was a user need created for high 11 burnup issues specifically, and the RIL was mentioned 12 as a tool to support that effort. And so, there is a 13 user need that we can provide which identifies the 14 Research Information Letter.
15 MEMBER BALLINGER: That would be great.
16 MS. BALES: I just want to say that the 17 body of work that it refers to itself is not any user 18 need. Our participation in this program was a 19 commitment that Research made outside of that.
20 MEMBER HALNON: But is the RIL a public 21 document?
22 MS.
BALES:
- Yes, RILS are public 23 documents.
24 MEMBER HALNON: Okay. Real time? I mean, 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
18 I guess what I'm asking is, is it issued, and then, 1
the industry gets it real time, as opposed to a year 2
or two down the road after it's digested by the NRR?
3 MS. BALES: So, right now, a copy of the 4
Research Information Letter is available in draft to 5
support this meeting, because it's a public meeting 6
and all of the materials for ACRS meetings are public.
7 Once it's signed and concurred on, and transmitted 8
officially from the Office of Research to NRR, it is 9
public that moment. There's no digestion period from 10 the program office.
11 MEMBER HALNON: So, when it gets through 12 the process?
13 MEMBER BLEY: I think you can also get a 14 RIL out much quicker than a NUREG, I believe. And 15 there was something of a sense of urgency in getting 16 this out, I think, from what you talked about at 17 Subcommittee.
18 MS. BALES: Yes, there's high burnup 19 applications that are coming in through the licensing 20 office right now. And we wanted to put information in 21 the staff's hands that would allow them to review that 22 information in the context of what we know about these 23 phenomenon. And so, we wanted to make that available 24 as soon as possible.
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19 MEMBER BLEY: And I'm going to say this a 1
little wrong, but it strikes me from what I heard at 2
this Subcommittee there's a lot of knowledge gaps 3
remaining here. And I guess having this in the hands 4
of NRR is important, so that they know what went on 5
and what we don't know before they have to decide on 6
an application.
7 MS. BALES: Yes.
8 MEMBER BLEY: I mean, I assume that's 9
what's driving that.
10 MS. BALES: Yes, and I also want to say 11 that this is all public information. So, there could 12 be proprietary information that would supplement this, 13 and it could appear in a license application. So, 14 even the gaps that are existing in the RIL may be 15 filled with nonpublic information, and that would be 16 something that the licensing office would have access 17 to, once an application actually came in. I'm not 18 saying that that exists, but just to point out that 19 the RIL only refers to data that is public, and a 20 large amount of it, we actually requested to be made 21 public for the publication.
22 MEMBER BLEY: Okay. Thanks. That helps 23 me.
24 VICE CHAIRMAN REMPE: So, just for 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
20 information purposes, on the user need, could you 1
elaborate what they said they would do with the RIL?
2 What would be the next step? Because I would like to 3
better understand what this would lead to, what their 4
intent is.
5 MS. BALES: So, that is, unfortunately, 6
not identified in the user need. The user need just 7
says what products the Office of Research will 8
produce. It doesn't define the next steps.
9 VICE CHAIRMAN REMPE: What's typically 10 then?
11 MS. BALES: It varies. It sometimes can 12 be a Regulatory Guide. So, I'll say in the case of 13 04-01, regulatory guidance was updated, because the 14 limits for RAA are located in regulatory guidance. In 15 the case of 08-01, a proposed rulemaking was initiated 16 because the findings in 08-01 called into question 17 50.46 criteria. So, it really depends on what the 18 conclusions of the research are.
19 FFRD is currently not addressed in 20 guidance, and it's currently not explicitly identified 21 in regulations. And so, it's not obvious that either 22 of those actions would be required as a prompt from 23 this.
24 MEMBER BALLINGER: Did 08-01 result in 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
21 NUREG-2240, whatever the number is? The last version 1
of
- fuel, that described fuel dispersal and 2
fragmentation?
3 MS. BALES: So, let me go to the next 4
slide because the last point on here is just to say 5
that Research Information Letters do not provide 6
guidance, and I think we've kind of covered that. I 7
don't want to forget to mention it, though.
8 As we go to the next slide, NUREG-2121 is 9
a literature review that the staff produced. Okay.
10 So, I start with 08-01. I mentioned that its primary 11 purpose was to establish new embrittlement criteria 12 relative to 50.46 rulemaking. At that time, we 13 already had seen the first example of fuel dispersal 14 in a test that had taken place at Halden on a rod that 15 was 92 gigawatt days, far above the license burnup 16 limits. Because we had that information in RIL 08-01, 17 we identified dispersal as a potential issue and said 18 that we would continue working on it. So, RIL 08-01 19 will mention it.
20 Following that RIL, there were additional 21 tests that were run, and it really prompted the staff 22 to go and do a literature review and see, for 90 tests 23 in over 30 years, what have we ever observed with 24 respect to fragmentation, relocation, and dispersal?
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
22 NUREG-2121 is, basically, a literature 1
review, and it reviews the past information. And the 2
conclusion drawn at the end of that review was that 3
fragmentation, relocation, and dispersal could not be 4
excluded, and that, at the time, the current burnup 5
limits were likely to prevent significant dispersal, 6
and therefore, there was no safety concern at that 7
time.
8 Additional research became available, and 9
in 2015, the staff also conducted an analysis that 10 looked at thermohydraulic conditions typical for 11 specific power histories and operating regimes and did 12 an analysis to determine how much fuel dispersal might 13 be expected in a nominal LOCA condition. And that 14 SECY-15-0148 concluded that, again, current licensing 15 limits were sufficient to prevent significant 16 dispersal. But, even in that SECY, we acknowledged 17 that that conclusion was heavily reliant on the 18 assumptions about burnup limits and how high burnup 19 fuel was operated; specifically, whether high burnup 20 fuel was located in low power regimes and, basically, 21 experienced a more benign LOCA because of its low 22 power.
23 And then, finally, now -- one more click 24
-- we have the Research Information Letter, which is 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
23 sort of a continuation of these documents and says 1
everything that we know as of today.
2 MEMBER BALLINGER: Do we know what the 3
status of 50.46(c) is?
4 MS. BALES: It is still up with the 5
Commission for a decision.
6 Okay. So now, I want to get into the 7
programs that are cited in the RIL and the peer review 8
process. The main thing I want to communicate about 9
the data sources is that we learned a lot since 2015, 10 when the staff last wrote about FFRD. The Studsvik 11 Cladding Integrity Program, Phase III, was conducted 12 completely after the 2015 SECY. Oak Ridge ran a small 13 hot cell program that added a few additional tests, 14 and one or two Halden tests were conducted after 2015.
15 The size of the circles represents the 16 number of tests, and the transparency of each circle 17 represents whether that information was publicly 18 available. So, prior to the RIL, the SCIP-III data 19 was not publicly available, and this RIL represents 20 the first time that this team disseminated. The Oak 21 Ridge and NRC LOCA tests were documented in public 22 journals and NUREGs.
23 On the next slide.
24 Because the data coming out of these 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
24 programs is relatively new and there is not a full 1
mechanistic understanding of the phenomenon, we wanted 2
to do a purity process. It's not a requirement for a 3
Research Information Letter, but we chose to do it 4
because we were committed to having outside opinion 5
and ensuring that we hadn't missed research that was 6
relevant, and that the basis for our conclusions in 7
the RIL were well supported.
8 So, we identified five individuals who 9
already had extensive familiarity with FFRD research, 10 either because they are conducting research themselves 11 or through their participation in programs like SCIP 12 and Halden. So, the names are listed here and a 13 little bit about their background.
14 Going on to the next slide, I want to now 15 talk about the outcome of the RIL. And again, I'm 16 talking about how the RIL could be used, before I talk 17 about the specific basis for each limit.
18 And as I talk about that, I want to 19 explain a little bit about the testing that forms the 20 basis for the RIL, because understanding how the tests 21 were conducted is going to be important for 22 understanding some of the conclusions that we drew.
23 And I'm wondering if, because I have added 24 so much animation and when I'm presenting it's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
25 convenient to do that, I wonder if I could just --
1 thank you. I don't want to cause a distraction.
2 But the testing that was done, almost 3
exclusively, except for Halden, all of the other three 4
programs that we cite in the RIL were tested on 5
prototypic irradiated fuel, irradiated in a commercial 6
reactor, typical fuel and cladding materials, but the 7
tests were conducted in a hot cell. The heat was 8
provided with a clamshell furnace. So, in the image 9
on the lower left, you see the furnace open, and the 10 orange square is encircling the fuel rod, a single 11 fuel rod. And there are four heating elements that 12 surround the fuel rod when the clamshell furnace is 13 closed.
14 MEMBER BALLINGER: So, I have experience 15 with this kind of experiment, with quad-elliptic 16 furnaces.
And is this plot an average of 17 temperatures? Is there a detailed report that shows 18 the individual temperatures around the fuel rod during 19 the test? Is this an average?
20 MS. BALES: The plot that's shown on the 21 lower right is the thermocouple that was used to 22 control the furnace. So, it's located just above the 23 center. And prior to the testing, there was an 24 extensive qualification program done by Studsvik about 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
26 the furnace. And in that report, you can find 1
discussion of the circumferential variation, the axial 2
variation.
3 MEMBER BALLINGER: So, there is a 4
quantification of the uncertainty?
5 MS. BALES: Yes.
6 MEMBER BALLINGER: Do you know what it 7
was?
8 MS. BALES: You mean the uncertainty in 9
the temperature at that location or --
10 MEMBER BALLINGER: Every 15 degrees sees 11 a factor of two. So, it doesn't take much.
12 MS. BALES: Yes. So, when we're looking 13 at oxidation, it is very important; small deviations 14 can have a huge impact on oxidation, especially as you 15 get to high temperature.
16 For the phenomenon that we're looking at 17 here, 15 degrees plus or minus, so basically, when 18 burst occurs and what the peak temperature is, I don't 19 think it's as significant as if you're looking at the 20 oxidation.
21 MEMBER BALLINGER: These tubes have a 22 helical texture.
23 MS. BALES: Uh-hum.
24 MEMBER BALLINGER: Which means the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
27 strength of the creep resistance is a function of 1
where you are on the fuel rod. And in that case, the 2
creep rate and the interaction between the creep rate 3
and the time of the test can make a difference as to 4
where the burst begins. So, has anybody done a look, 5
a careful look, at that?
6 MS.
BALES:
The microstructure is 7
hexagonal close-packed, and they are non -- I'm 8
forgetting the word. They have --
9 MEMBER BALLINGER: Plus or minus 45, 40-10 degree or 45-degree texture, but it rotates because of 11 the way the tubing is rocked or fabricated.
12 MS. BALES: So, as far as burst behavior 13 and the phenomena that we're looking at here, I don't 14 see that that is going to have an impact. Like I 15 said, the properties in each direction are different 16 because of the texture of the cladding, but not in a 17 way that should vary significantly over the axial 18 length.
19 MEMBER BALLINGER: These bursts are 20 notoriously difficult to interpret.
21 MS. BALES: So, there was a lot of 22 discussion about this at the Subcommittee. So, I 23 actually added a slide on this topic as well to kind 24 of expand on the impact of experimental conditions on 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
28 the things that we are measuring. I'm going to get to 1
that next.
2 I'll just finish by saying that the 3
segments are cut from full-length rods. They're about 4
30 to 50 centimeters in length. And they are 5
repressurized. There is a pressure line that is 6
integrated into the system and can vary the pressure, 7
and in many cases the test conditions included 8
variability in the pressure because that was a 9
parameter that we wanted to investigate.
10 MEMBER BALLINGER: Once you go above the 11 phased transformation, all that stuff goes away.
12 MS. BALES: Yes.
13 MEMBER BALLINGER: So, you know, depending 14 on where the burst occurs.
15 MS. BALES: So, as I said, I wanted to 16 expand on the influence of the experimental methods 17 because the tests that were done in all of the hot 18 cell programs had -- as I said, they are prototypic 19 materials; they're prototypic cladding and fuel, but 20 there are non-prototypicalities.
21 So, for example, if we look at the axial 22 length, the variability of heat is going to have a big 23 influence on the strain behavior. And so, on this 24 image, we see a very sharp increase in strain centered 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
29 in the middle of the furnace, and there is quite a 1
large strain. This axial profile, this strain 2
profile, is probably not prototypic of anything you 3
would see in a reactor. You would have a much more 4
uniform heat applied on a length of this -- of this 5
length --
6 (Internet connectivity problem.)
7 CHAIRMAN SUNSERI: It's the internet 8
connection.
9 MS. BALES: Okay. We're back.
10 So, the strain profile and, most likely, 11 the max strain are not prototypic. In addition, as I 12 mentioned, we have short segments, and it's not 13 obvious how to scale the short portion of the fuel rod 14 that's going through these LOCA conditions to a full-15 length rod.
16 So, on this image, I have the X-axis burn 17 up and the Y-axis is the mass of fuel, like the actual 18 amount of fuel that was collected. We can't multiply 19 that mass by any ratio of the segment length to a 20 full-length rod. That wouldn't be meaningful to do.
21 And finally, the burst opening size varied in the 22 test, and it's not obvious that these burst opening 23 sizes are prototypic.
24 Nevertheless, as I start to describe how 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
30 the experiments were used to derive empirical limits, 1
I want to make the case that the empirical limits are 2
derived in such a way to be independent of any 3
experimental non-protypicalities. We don't use the 4
mass of fuel collected and multiply it by the full 5
length. We don't use the length of the cladding that 6
experienced greater than 3 percent strain in any of 7
our empirical limits.
8 So, I will return to this concept as I 9
walk through the empirical limits, but I want to argue 10 that they are based on the physical constraints of the 11 cladding and diverse opening and not a skilled 12 interpretation of the quantities measured in the 13 tests.
14 MEMBER PETTI: So, just a question on the 15 burnup. That's fairly uniform over the sample 16 because --
17 MS. BALES: In these short samples, it's 18 fairly uniform. So, in a full-length rod it would 19 vary, but the samples of 30 to 50 were relatively 20 flat.
21 MEMBER PETTI: So, to extrapolate that 22 burnup to a reactor core, it's the peak burnup on the 23 rod most likely or the center portion of the rod?
24 MS. BALES: So, what we've described, the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
31 empirical limits would be pellet averages. And then, 1
through an analytical tool, you would determine what 2
the local burnup would be, and then, you would define 3
a limit.
4 MEMBER PETTI: So, it's burnup, but it's 5
the local burnup?
6 MS. BALES: Yes.
7 MEMBER BALLINGER: I've got to assume that 8
I have the wrong slides.
9 MS. BALES: This slide is also new.
10 There's three new slides. We've gone through two of 11 them. There's only one more to go.
12 (Laughter.)
13 Like I said --
14 CHAIRMAN SUNSERI: Your assumption is 15 confirmed.
16 VICE CHAIRMAN REMPE: Tell us before --
17 MEMBER BALLINGER: We all have the wrong 18 slides.
19 MS. BALES: I apologize. Yes. So, like 20 I said, after the Subcommittee meeting, there was sort 21 of three areas that I felt deserved some time, and I 22 added slides to facilitate that discussion. And I 23 will get the presentation that includes those slides 24 after this, all of the slides, except for this one at 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
32 the end.
1 MEMBER PETTI: So, just another question 2
before you go. The stain profile that's shown, given 3
that it's a short segment, the gradient with respect 4
to distance is probably steeper than is seen in a 5
reactor.
6 MS. BALES: Yes. Yes.
7 MEMBER PETTI: Okay. From an analytical 8
perspective, can they can calculate anything close to 9
this?
10 MS. BALES: That is discussed in the 11 limitations of this RIL at the end. We acknowledge 12 that the limits are based on local conditions, and 13 that the tools that we have right now are really 14 catered to calculating the max strain. They haven't 15 really been calibrated to calculate the length of the 16 (audio interference) event.
17 So, creep models are well-informed. And 18 so, there's not exactly a reason to believe that we 19 have no understanding of that, but it's behind 20 something that deserves some further validation.
21 MEMBER BALLINGER: Yes, I took the liberty 22 after the Subcommittee meeting of contacting a 23 modeler, whose name shall remain anonymous, and asked 24 that person, what's the strain at burst in these tests 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
33 calculated? And he says, "What do you want it to be?"
1 (Laughter.)
2 So, it's very uncertain, very uncertain.
3 MEMBER PETTI: Well, you know, I mean, 4
creep, especially the time --
5 MEMBER BALLINGER: Yes.
6 MEMBER PETTI: -- I mean, there's just so 7
many variables; it's always difficult -- always.
8 MS. BALES: Yes, and I think as we get 9
into the information in the RIL, you know, Kim already 10 mentioned it and it's really important to drive home.
11 The RIL outlines what I call the on/off switches, like 12 when do these phenomena start and stop? It is not the 13 full picture. In order to really use those, there's 14 a whole lot of analysis that has to happen.
15 What you're both describing in terms of 16 what are the fuel rod conditions and exactly what is 17 the (audio interference), but prior to that, looking 18 at the LOCA conditions and understanding what kind of 19 hydraulic bounding conditions these rods are being 20 subject to, whether they actually reach the 21 temperatures that are required -- this RIL is really 22 just a piece of a much bigger puzzle. And I think 23 it's important to keep that in mind when looking at 24 what it is and what it is not.
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34 MEMBER HALNON: Well, given that, that the 1
picture is not clear yet, why the RIL now? I mean, 2
what's the urgency in getting this?
3 MS. BALES: So, in order to do any of that 4
analysis that would follow from this, you have to know 5
the on/off switches. That is a key part of a more 6
complete analysis. You have to know when the 7
phenomenon occurs in order to say what are the 8
implications; when is it occurring? And so, the 9
RIL --
10 MEMBER HALNON: It's just puts the 11 regulatory piece in a very precarious situation, 12 because now you have these on/off without the full 13 picture. What do you do with it? I mean, do you 14 start backfitting and start setting limits? Do you 15 come back? What is NRR going to do with this, given 16 the fact that it's just on/off?
17 MS. BALES: I see our colleague in NRR 18 stepping to the microphone.
19 MR. DONOGHUE: Good morning.
20 CHAIRMAN SUNSERI: Please state your name.
21 MEMBER BALLINGER: By the way, before we 22 get started, I've been informed that, in Cinderella 23 fashion, your time is going to be up in 20 minutes.
24 MS. BALES: I'd better get moving.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
35 MEMBER BALLINGER: So, we'd better get 1
moving.
2 MR. DONOGHUE: And I'll be brief.
3 My name is Joe Donoghue. I'm the Division 4
Director of Safety Systems in NRR, working closely 5
with Kim and her staff.
6 We expect to use the RIL to guide our next 7
steps, and we haven't decided what they are because 8
the RIL is not quite final, but, as Michelle has 9
mentioned, it could be the basis for guidance. In the 10 past, that's what we've done. But, as you're all 11 realizing here, there is a lot of uncertainty in the 12 information, a lot of gaps.
13 And what prompted us to talk about actions 14 that we could take to update our knowledge is that 15 industry has made it clear that high burnup fuel, you 16 know, batches of high burnup fuel, is something that 17 they want to pursue in license. So, we felt like we 18 needed to update the information, the understanding 19 that we had from 2015. I think you had a slide up 20 there, Michelle, to show that SECY paper. And then, 21 decide what has changed, what do we know. Do we have 22 a basis to go further than burnup? What do they want 23 to propose? Do they want to go higher in high 24 burnups, then, that would be licensed by a Topical 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
36 Report?
1 So, what we're going to do is review the 2
RIL, work with Research, and as Michelle pointed out, 3
usually vendors, when they submit it, they might have 4
information that would help fill some of the gaps, 5
would help us understand better what we can allow to 6
be licensed.
7 Until we see all that laid out, it's hard 8
for me to say that we're going to change any of the 9
current limits that are out there, okay, one way or 10 the other. Okay?
11 So, another point, and then, I'll stop, 12 is -- and I think you're going to get to this, 13 Michelle. In your presentation, which was very good, 14 I thought it made clear that the concerns about FFRD, 15 it's not just the "FF," the fragmentation; it's the 16 relocation and dispersal, which depends on other 17 factors. I think you all know that.
18 So, we have to understand all that better 19 before we make a decision about exactly what we're 20 going to do in a regulatory framework. Does that 21 help?
22 MEMBER HALNON: Yes, it does to some 23 extent, which basically says that the increased burnup 24 discussions are on hold until we get the full picture.
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37 MR. DONOGHUE: Yes.
1 MEMBER HALNON: That's what I heard.
2 MR. DONOGHUE: Well, I'll say that we felt 3
it was premature to try to set down guidance, because 4
without an update to the information, it could be very 5
conservative guidance.
6 MEMBER HALNON: Right. That's what I'm 7
trying to see.
8 MR.
DONOGHUE:
We'll still having 9
presubmittal meetings with vendors on their proposals.
10 So, that's why I didn't want to just say yes, because 11 there are discussions that are continuing, but they're 12 presubmittal; we're not doing extended high burnup 13 with views over 75.
14 MEMBER HALNON: Okay. So, the timeline 15 for -- and I'll let you go after this -- the timeline 16 to get this full picture is important, because if 17 you're having presubmittal meetings, somewhere at some 18 point they're going to collide and you're going to say 19 "No," until they get the full picture. So, okay.
20 MEMBER BALLINGER: Now I'll violate my own 21 previous statement. We have a case here where we have 22 actual data, but it's highly uncertain in terms of its 23 effect and the relationship between that data and the 24 real world, and what one member has called "Chapter 15 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
38 hell," where you end up with a very stylized analysis 1
that must be done.
2 MR. DONOGHUE: Right.
3 MEMBER BALLINGER: And when you tack on 4
the uncertainty
- here, which results in very 5
conservative assumptions, with the Chapter 15 6
analysis, it can be difficult.
7 MR. DONOGHUE: Understood. And that's why 8
I'm tiptoeing around so much and saying I don't want 9
to prejudge the staff's conclusions, until we've heard 10 from the RIL and from all these sources, to understand 11 how to best come to reasonable assurance/conclusion 12 based on all these uncertainties. I mean, there's 13 other areas, you're aware, where we've dealt with 14 uncertainties before. This is, yes, definitely 15 difficult.
16 MEMBER BALLINGER: You've got to move.
17 CHAIRMAN SUNSERI: Yes. I'd like to ask 18 one question, though. Joe, you can stay for this one.
19 I just want to understand. I missed the Subcommittee, 20 and I apologize if this is a redundant question.
21 But it sounds to me like, and I heard 22 Michelle say, that this is a compilation of publicly 23 available information compiled to present to NRR to 24 aid your knowledge and your decisionmaking when it 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
39 comes to this topic. So, it seems to me that -- is 1
that the way NRR is planning to use this, as 2
information to help them understand whatever their 3
gaps in their knowledge are, and when they review 4
applications, what questions they should be asking, 5
based on public information, available information, 6
and help make sure you get the in-depth review that 7
you need to do versus a definitive limitation on what 8
you can approve and not approve?
9 MR. DONOGHUE: Yes.
10 CHAIRMAN SUNSERI: That's not a very well-11 organized question, but --
12 MR. DONOGHUE: It could be -- I'm sorry.
13 CHAIRMAN SUNSERI: Go ahead.
14 MR. DONOGHUE: It could be used to put 15 down definitive guidance, but I'm not ready to say 16 that's exactly what we're going to do, because it may 17 just help us inform the reviews, as you said, to 18 understand what questions to ask, and then, we may 19 have to somehow account for these uncertainties with 20 conservatisms.
21 In other areas, you may remember a couple 22 of years ago the coated cladding ISG that went out.
23 It was, I think, much more solid information. The 24 staff, we felt confident being able to issue guidance 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
40 on that that applicants could use.
1 In this case, right now, this is what's 2
happening. This is what's happening right now.
3 Vendors see the challenge and they're approaching it 4
in different ways. We're not ready to say that, 5
because it would be prejudging this, that one approach 6
is better or worse than another. So, at some point, 7
though, we think we could know enough -- and I'm not 8
saying the RIL is it by itself -- but at some point we 9
would have enough information that we should be able 10 to put some guidance together. I'm just not ready to 11 say when and how we do that.
12 CHAIRMAN SUNSERI: Yes, and, no, I'm not 13 asking for that. It was just how this information 14 might be utilized. You answered my question. Thank 15 you.
16 MR. DONOGHUE: Yes.
17 MS. BALES: Given the time constraints, 18 I'm going to skip a couple of slides.
19 CHAIRMAN SUNSERI: Don't feel overly 20 constrained. I mean, you know, don't load your time, 21 but take whatever time you need to get your points 22 across.
23 MS. BALES: Well, I think, based on the 24 interest that I'm hearing, there's a couple of slides 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
41 that we've prepared that will address some of this 1
topic. And how about I go through that? And then, 2
I'm going to skip some of it. But if there's 3
questions based on either followup from the 4
Subcommittee or reading the RIL, I can definitely go 5
back to it. I just want to make sure that, before I 6
really do run out of time, that I've made a couple of 7
key points. So, I'm going to appear to be skipping 8
through the slides, but --
9 CHAIRMAN SUNSERI: But just so I make 10 sure, since I'm moderating this, you're the last 11 presenter or there's more?
12 MEMBER BALLINGER: No, NEI.
13 CHAIRMAN SUNSERI: Well, NEI, they have 14 seven slides, right. Okay, I've got it.
15 MS. BALES: The slides that we've 16 presented here are all that the staff has prepared.
17 CHAIRMAN SUNSERI: Okay.
18 MS. BALES: So, I'll be speaking to a 19 couple more slides.
20 CHAIRMAN SUNSERI: Okay. Great. And how 21 far along are you into that?
22 MS. BALES: Not very far.
23 (Laughter.)
24 CHAIRMAN SUNSERI: Okay. Go ahead.
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42 MEMBER BALLINGER: Think about 9:40.
1 MS. BALES: Okay, I'm going to wrap up at 2
9:40.
3 So, I put all of these images on the slide 4
because I wanted to kind of give you the impression 5
that, if you just open up a bunch of these reports 6
that have documented FFRD research, you could look at 7
this and say, wow, there's a lot of fragmentation 8
there. There is a lot of phenomena that we don't 9
really understand. Why is it happening in this circle 10 pattern in that image? How do we make sense of all of 11 these fragments? And you can come away thinking that 12 this is sort of an intractable problem.
13 And with the RIL, I really want to argue 14 that it's not an intractable problem; that, in fact, 15 we know quite a bit about when FFRD occurs and, most 16 importantly, when it does not occur. And with that 17 information, we've presented the RIL to really allow 18 for a focus of fuel safety analysis on only the rods 19 and portions of the rods that matter. And I think 20 that's really the mean outcome of the RIL, is to focus 21 safety analyses.
22 So, we've addressed these five elements.
23 I won't go through them because I'll have to speak to 24 them in the next slide. I'm going to walk through 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
43 this outcome of the RIL talking about the focused 1
analysis using this cartoon stylized image.
2 What this represents is a depiction of 3
each assembly in the core relative to its burnoff and 4
its operating power at a single point in life. And I 5
use this because it will help illustrate how the RIL 6
helps to focus the analysis from all of these rods and 7
the full length of these rods to just a handful that 8
actually are vulnerable to FFRD.
9 So, the RIL lays out fine fragmentation is 10 not occurring in fuel rods below about 55. That means 11 that during steady-state operation there is some 12 pellet cracking and there is some large fragments that 13 you will observe at the end of life, but that this 14 transient phenomena where the fragments become more 15 fine has only really been seen when you're getting to 16 burnoffs above 55. So, every rod below that does not 17 need to be examined for its susceptibility to fine 18 fragmentation.
19 When you look at relocation, this is where 20 a fuel pellet falls axially into the balloon region.
21 This also has not been seen unless you have fine 22 fragmentation, and it requires ballooning, which is 23 temperature-dependent. So, only rods that are 24 operating at a high enough power during operation, and 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
44 therefore, will see high temperatures during the 1
transient, are vulnerable to fuel relocation. So, 2
again, a limited number of rods that are of concern.
3 MEMBER BALLINGER: Is there any thought 4
that the fine fragments may come from the rim?
5 MS. BALES: We have examined that, and 6
there was some work done, sponsored by NRC, and then, 7
followed up by SCIP, to look at the origin. For rods 8
between 50 and 60, we see that the fine fragments are 9
almost exclusively from the rim region. But, as you 10 go up in burnup above 70, there's evidence that those 11 fragments come from the entire radius, even from the 12 center.
13 Dispersal is also limited. Physically, 14 you can only disperse fuel if you have burst, and you 15 can only disperse fuel that has moved from another 16 part of the rod into the burst region. And so, a 17 dispersal is also limited by the boundaries of fine 18 fragmentation and relocation.
19 I forgot to mention why I put the image on 20 the lefthand side. We've seen that relocation 21 requires local cladding strain. If the cladding is 22 still tightly binding the fuel, you don't have axial 23 relocation. So, even where I'm drawing this box 24 around rods with high enough power and the right 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
45 burnup, we're still not talking about the full length 1
of the rod. We're only talking about the region above 2
and below the burst which has strained to around 3 3
percent.
4 So, this dispersal zone is relatively 5
small. The area, the fuel rods that have a concern 6
that need to be examined for their vulnerability and 7
quantity of dispersal is probably small and it is 8
affected by the core loading pattern. And depending 9
on your ECCS response, your plant design, loading 10 pattern, and even fueling cladding designs, you may 11 have a core that has no rods operating in this 12 dispersal box.
13 The RIL also addresses transient fission 14 gas release, and the reason is that transient fission 15 gas release -- in other words, fission gas release 16 that occurs during the transient, not during (audio 17 interference) elaboration -- will increase the rod 18 internal pressure during a LOCA event. And rod 19 internal pressure is a key determinant for whether the 20 rod bursts. So, accurately predicting rod internal 21 pressure is essential to accurately predicting burst, 22 which is essential to accurately predicting dispersal.
23 So, accounting for transient fission gas release is 24 required in order to correctly estimate how much 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
46 dispersal a certain core might experience.
1 MEMBER BALLINGER: Might we be getting the 2
cart before the horse? Excuse me. Might we be 3
getting the cart before the horse a little bit? At 4
high burnup, the fission gas is mostly located on 5
grain boundaries, I think, and if it's in the rims, 6
for sure. And if you have a very high temperature, 7
fast temperature transient, that fission gas may form 8
instant bubbles and blow and cause the fragmentation, 9
the fines.
10 MS. BALES: So, there is a hypothesis that 11 the fine fragmentation has something to do with 12 trapped fission gas release and cleaving of the pellet 13 to further fragment it. What I'm referring to here, 14 though, has been seen experimentally, that when a 15 modeler is trying to predict burst or non-burst, and 16 they don't account for transient fission gas release, 17 they have gotten the prediction wrong. When they tune 18 their model to account for a transient fission gas 19 release, they can better identify the moment of burst.
20 So, here I'm not talking about the 21 mechanism for fine fragmentation. I'm just simply 22 saying that accounting for transient fission gas 23 release is important to predicting burst.
24 MEMBER BALLINGER: You used the word 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
47 "tuning," and I use the word "fudge factor."
1 (Laughter.)
2 MS. BALES: Yes, that is fair.
3 VICE CHAIRMAN REMPE: All modelers use 4
fudge factors.
5 (Laughter.)
6 MEMBER BALLINGER: In this case, we're 7
serious.
8 MS. BALES: Well, you know, no, and to 9
take the point seriously, these are empirical limits.
10 They are not mechanistic models. And we have to be 11 aware of that when we're applying them, not only just 12 in the case of uncertainty, but just in the case of we 13 can't apply this information beyond what it was 14 measured against. We can't apply it to new 15 conditions. These are highly empirical.
16 MEMBER BALLINGER: Which means, in 17 layman's terms, you can't extrapolate.
18 MS. BALES: Exactly. Exactly.
19 The last item that the RIL addresses is 20 packing fraction, and I talked about axial fuel 21 relocation before and the possibility of fuel from 22 above the burst opening to fall into the burst area.
23 In non-burst rods, we care about how much fuel is 24 located in that region because it affects the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
48 temperature. That additional fuel needs to be 1
accounted for when you are determining the decay heat 2
load in that region, and that's essential for 3
identifying the cladding temperature, which is our 4
deterministic metric for LOCA success. Heat cladding 5
temperature is the limit, one of the key limits for 6
loss of coolant.
7 MEMBER KIRCHNER: May I ask a question?
8 Yes, I'm looking at this -- I'll take off my mask for 9
a moment. Isn't temperature much more important than 10 linear heat generation rate? I'm just curious why 11 you're applying it against linear heat generation 12 rate.
13 MS. BALES: So, temperature during the 14 transient is the key determinant. And this is really 15 depicting the power of the operating rod prior to the 16 transient.
17 MEMBER KIRCHNER: Yes.
18 MS. BALES: And so, it's imperfect, but I 19 use this cartoon just to kind of depict the population 20 of rods in the core to emphasize the point that we're 21 not talking about the entire core. But if we're 22 actually determine whether each of these rods 23 experiences the phenomenon, you're
- right, the 24 temperature during the transient is the key 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
49 determinant. This is just the stylized illustration 1
to kind of scoop the situation more than it is to --
2 MEMBER KIRCHNER: Thank you.
3 MS.
BALES:
kind of (audio 4
interference) the on/off switch.
5 MEMBER BALLINGER: I keep coming back to 6
the prototypicality, if that's a word. The heat 7
generation rate that results from nuclear heating 8
results in a temperature profile that's way different 9
from a furnace. No matter what you do, you can't 10 reproduce that. And the first time you heat the fuel 11 up, it's going to crack in real life. Has anybody 12 done any work to see if they just do one cycle of 13 parabolic heating that cracks the fuel, and then, runs 14 a balloon test to see if you get any dispersal from 15 just the fact that the fuel is cracked due to the 16 thermal gradings?
17 MS. BALES: So, there were tests done in 18 the SCIP program at 40 gigawatt days per metric, for 19 example. So, those rods would be irradiated in the 20 reactor. They had protypical end-of-life cracking 21 that you would expect from steady-state operation, the 22 thermal --
23 MEMBER BALLINGER: Right, but they were 24 cracked at.1 gigawatt days per metric.
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50 MS. BALES: Right. What I'm saying is 1
that those rods experienced a transient, and we did 2
not observe fine fragmentation in --
3 MEMBER BALLINGER: I don't mean by fine 4
fragmentation. What I'm saying is you've got cracked 5
fuel.
6 MS. BALES: Yes.
7 MEMBER BALLINGER: And then, you have a 8
ballooning problem and you rupture the fuel. You 9
rupture the cladding. Do you get dispersal of those 10 fragments, not fine, but those fragments?
11 MS. BALES: So, in this RIL, we're only 12 proposing that rods with fine fragmentation are the 13 ones that are concern for dispersal. So, the large 14 fragments of a lower burnup would not be --
15 MEMBER BALLINGER: Okay. I'm just trying 16 to center myself on where this -- what happens when 17 and where.
18 MS. BALES: Right.
19 MEMBER BLEY: This is more of a question 20 for Ron, but for you folks, too. We've got empirical 21 evidence of when we've had bursts. But if you get 22 fuel fragmentation and begin to rearrange things a 23 bit, you're kind of packing tighter. So, even if they 24 didn't get bursts, if you go through any thermal 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
51 cycles, you may be really stressing that clad in 1
unexpected ways. I don't know if anybody has played 2
with that.
3 MEMBER BALLINGER: If you're not careful, 4
in the very early days, they had basically zero -- I 5
mean, in the early days, they had --
6 MEMBER BLEY: I remember.
7 MEMBER BALLINGER: -- basically zero gap.
8 MEMBER BLEY: That's what got me thinking 9
about that, yes.
10 MEMBER BALLINGER: Which that was not a 11 good thing.
12 MEMBER BLEY: And they broke a lot, yes.
13 MS. BALES: In the RIL, there is a 14 reference to some work done at the National Labs to 15 look at the comparison of Halden's temperature profile 16 to the hot cell tests. So, just to kind of address, 17 I think, the underlying concern that these hot cell 18 tests are not simulating the temperatures -- I should 19 get closer, yes; sorry -- the initial portion of the 20 transient will look different when you're looking at 21 the radial temperature profile across the pellet in 22 the two tests. But, after about 27 seconds -- I'll 23 say after about 30 because 27 is too -- that the axial 24
-- sorry -- the radial temperature profile in both 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
52 Halden-style tests and hot cell tests is actually the 1
same.
2 And so, while the irradiated effects --
3 sorry -- the effects of nuclear heating are not 4
negligible -- sorry -- they are not non-existent; they 5
are there, especially at the beginning, as the 6
transient continues, there's been some analysis to 7
show that the radial temperature profile is very 8
similar, and it's that radial temperature profile, the 9
differences in the temperature across the pellet, that 10 we believe have something to do with the 11 fragmentation. So, the fact that they're similar 12 suggests that the fragmentation might be similar as 13 well.
14 So, given the amount of time and the 15 suggestion to wrap up at 9:40, I'm going to skip the 16 discussion of the specific basis for each of these 17 limits. That does not mean that -- obviously, if 18 there are questions, I am going to go through it.
19 So, this is not a suggestion that we skip 20 the material. I just want to make sure to address the 21 third new slide. Sorry, Mr. Ballinger, that there's 22 one more slide that I think speaks to what questions 23 have been asked today and really the questions that 24 started to come up on the Subcommittee about where the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
53 RIL fits into the bigger picture. So, if it's okay, 1
I'm going to skip to that slide, and then, I'll take 2
feedback as far as whether I should come back into 3
these technical details. The material in here is 4
really explaining -- there's some good videos, but, 5
again, I can come back to this.
6 Okay. I want to present this slide to 7
come back to some of the discussion that we were just 8
having. So, when making a determination of whether 9
fuel dispersal is a problem, I think we have to kind 10 of go at the very highest level of what is the 11 likelihood of a LOCA event in the first place. We 12 understand that this is a design basis accident. So, 13 from a regulatory perspective, it must be analyzed.
14 LOCAs are a design basis event. We recognize that 15 it's a low probability event, but, nevertheless, it's 16 a required analysis.
17 Then, if you are predicting a loss-of-18 coolant accident, there are a variety of loss-of-19 coolant accidents of varying severities. The testing 20 that was done predominantly is designed to simulate 21 double-ended guillotine large break LOCA. And so, we 22 recognize that the technical basis that we're 23 pointing to here is a particular type of LOCA. And 24 so, informing this section above of which LOCA 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
54 conditions will actually prompt the conditions that 1
we've observed FFRD is an important step.
2 Then, once you know the conditions that 3
you are subjecting your rod to, then you ask yourself, 4
well, what is the fuel response to those conditions?
5 When do the phenomenons I'm concerned about occur and 6
when do they not occur? And really, that is what the 7
RIL does. It's just this one piece.
8 After you've determined that you 9
experience relocation and potentially dispersal, then 10 you want to know how the system responds. Where does 11 that fuel go? Is there a recriticality? Are there 12 other unanalyzed conditions that arise from fuel in 13 the coolant that wasn't expected to be there? That 14 happens outside of the RIL; that's after the RIL.
15 And then, finally, there's a lot of 16 conservatism in the licensing basis. So, even when 17 you're predicting some fuel dispersal or other 18 consequences of a LOCA, we may find that the licensing 19 basis is conservative enough to account for that, and 20 the licensing basis isn't challenged by that new 21 information. That, again, is outside of the scope of 22 the RIL, but is an important step to understanding the 23 scope.
24 MEMBER BALLINGER: I would very much --
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55 oh, okay, you haven't completed the slide. Okay.
1 MS. BALES: I love animation.
2 (Laughter.)
3 So, it keeps going.
4 MEMBER BALLINGER: But I'll say it anyway 5
because it's getting to the end. I would have liked 6
to see on this slide a line between Research and NRR 7
and a box somewhere below the line, I assume, that 8
says, "Consequences."
9 MS. BALES: Right.
10 MEMBER BALLINGER: In other words, we 11 observe it --
12 MS. BALES: Yes.
13 MEMBER BALLINGER: -- undeniable. We 14 don't know -- we have a very large amount of 15 uncertainty in what's going on, but unless that gets 16 translated into consequences --
17 MS. BALES: Yes. So, the green box should 18 say, "Consequences." That is what I meant.
19 MEMBER BALLINGER: All right.
20 MS. BALES: The green box is like the 21 system response. It's, can the system and the MRC 22 core cooling system accommodate fuel dispersal? Said 23 another way, that is the consequences.
24 And what I want to communicate is that, in 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
56 order to do that analysis, you must have the 1
boundaries of the box. The RIL establishes those.
2 And so, you cannot possibly do the consequences 3
analysis without knowing when you get the 4
consequences.
5 And so, I am very --
6 MEMBER BALLINGER: But, again, I'll hate 7
to cut you off, but I would maintain that you need to 8
estimate the consequences first, because that gives 9
you direction on how detailed you have to go; aka how 10 much money you have to spend, or to force the 11 suppliers to spend --
12 MS. BALES: Yes.
13 MEMBER BALLINGER: -- to go after this 14 problem.
15 MS. BALES: You know, I think that's a 16 fair point, and I think that others have argued that 17 you could kind of do it either way. You could either 18 identify where the cutoffs are, and then, determine if 19 you can accommodate that kind of response, or you're 20 what is the amount of fuel that I can accommodate, and 21 then, work backwards to create your design limits to 22 prevent that.
23 MEMBER BALLINGER: I just wonder whether 24 we get ourselves trapped in what I call the Rockwell 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
57 effect. Rockwell was critical of our industry because 1
we had a habit of piling piles and piles of 2
conservatisms on something that was unneeded. And 3
then, when the time came to backtrack and get rid of 4
some of that conservatism, it became a non-technical 5
problem, aka a political problem that was very 6
difficult to solve.
7 MS. BALES: You know, I'm very empathetic 8
to that argument. I think that that is an important 9
consideration, especially in an issue like this.
10 What I will say, though, it that, at this 11 moment, we live in a deterministic world. The 12 regulations are set up to be what they are. We have 13 criteria that say you must show compliance with 50.46; 14 you must show that you're below this oxidation limit; 15 you must show that you're below this PCT limit.
16 So, it's a fundamental shift. It's not 17 something that you can just wrap around at the end and 18 say, well, yes, technically, the regulations say this, 19 but here's how we're going to make sense of it. It 20 has to be done with rigor. It is definitely possible 21 to really scale out and look at the bigger picture, 22 and the RIL is part of that also, because in order to 23 do that, I said you still have to know when the 24 phenomenon occurs to do all of that work. So, the RIL 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
58 does not preclude an approach that would kind of work 1
the problem backwards, and it doesn't preclude an 2
approach where you have sort of risk information 3
wrapping around the phenomena.
4 At this moment at this day, though, the 5
criteria that are in place for loss-of-coolant 6
accidents are deterministic, and we have to 7
acknowledge that.
8 It is 9:42. This is the point that I 9
wanted to make.
10 MEMBER BALLINGER: I look to the Chairman.
11 CHAIRMAN SUNSERI: We're going to be 12 writing a letter on this. So, we want to be well-13 informed.
14 MS. BALES: Okay.
15 CHAIRMAN SUNSERI: Get your points across.
16 MEMBER PETTI: Can I ask just a question?
17 You know, you put these extra sides to help us 18 understand the context.
19 MS. BALES: Yes.
20 MEMBER PETTI: I worry that others don't 21 understand the context. This document will come out.
22 It will be public.
23 MS. BALES: Yes.
24 MEMBER PETTI: It says 55 megawatt days.
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59 People say, what does that mean for the current fleet, 1
which is not really what your issue is.
2 MS. BALES: Uh-hum.
3 MEMBER PETTI:
But it could be 4
misinterpreted to be that.
5 MS. BALES: Yes.
6 MEMBER PETTI: I think you need like a 7
foreword in the document --
8 MS. BALES: I totally agree.
9 (Laughter.)
10 MEMBER PETTI: -- that puts this context 11 in place, so that people don't run off -- if we're 12 going to do it, lots of people will do it is my sense.
13 MS. BALES: I think that's an excellent 14 idea. And in fact, that is definitely the conclusion 15 we came away with from the Subcommittee meeting.
16 Sometimes, you know, I have to say, like writing this 17 document, I've been working with this data for a year.
18 I've been in it, and I didn't see the potential until 19 the Subcommittee like I did during that meeting. And 20 I came away thinking, you know, there's some context 21 missing. And so, at Kim's suggestion, we are going to 22 add a foreword. I've already drafted it. We've 23 reviewed it. And I think it's incredibly important, 24 and I think that it's possible that this RIL did not 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
60 stand on its own the way I thought it did, and we're 1
going to address that.
2 MEMBER HALNON: That would satisfy me with 3
the NRR interaction I had relative to, what do you do 4
with this?
5 MS. BALES: Right.
6 MEMBER HALNON: So, that would be 7
excellent.
8 MS. BALES: Yes.
9 VICE CHAIRMAN REMPE: I think this is a 10 great idea. Again, I'm just wondering, I mean, is 11 this still the right time for the letter? Or should 12 we see the foreword? I mean, you're going to get 13 comments about that, and I'm just wondering about 14 timing. But, again, I'm just one member and I'm just 15 listening to this going, man, it sounds like some 16 major improvements can be made.
17 MS. WEBBER: This is Kim Webber.
18 Yes. So, that's a good question. So, we 19 have like a working draft. We haven't completed the 20 draft for the foreword, but I think it's a good idea 21 because a lot of what I said in my opening remarks, 22 and what Michelle has talked about, is in that 23 foreword. So, actually drafting the foreword helped 24 us put the context into words for this presentation.
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61 So, I don't know what your timing is for writing the 1
letter, but we can definitely work on it, you know, 2
probably over the next week or so. We want to make 3
sure that our partners in NRR have a chance to weigh 4
in and take a look at it as well.
5 VICE CHAIRMAN REMPE: So, we don't have 6
January full Committee meeting. We have February and 7
it's very packed, and things like that. But I'm 8
listening to this going, man. I mean, we're here to 9
help the agency in writing a letter with a lot of 10 concerns versus a letter that says, hey, we've 11 assessed this --
12 CHAIRMAN SUNSERI: We write letters all 13 the time on things that aren't final. We say I think 14 it would be a good idea to have a foreword. That 15 could be a recommendation coming from us, and you do 16 it. So, it sounds like we're in agreement on that 17 topic already.
18 MS. BALES: Yes. Okay.
19 MEMBER BALLINGER: You know, I hate to 20 what is going to be amounting to beating a dead horse, 21 but -- sorry about the dead horse part. But the fact 22 that you get fuel fragmentation and dispersal, if you 23 want to call it that, at 55, that does not mean that 24 it makes any difference. And that's why the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
62 consequence thing becomes very, very important.
1 Because we've been doing -- we've got a lot of fuel 2
out there that's above 55, without having a LOCA, by 3
the way.
4 And so, I think the foreword that you're 5
talking about would be very informative, but something 6
else might be also informative. And that is, there's 7
been very little -- you know, I understand the 8
difference or the distinction between NRR and 9
Research. But this is one case where Research 10 produces a document that has the data analysis in it, 11 but the immediate use is for NRR.
12 And so, I wonder -- and I don't know how 13 the RILs actually work -- whether or not there should 14 be some NRR input, a little feedback, with respect to 15 the foreword that you do. Maybe I'm using the 16 wrong words --
17 MS. BALES: No.
18 MEMBER BALLINGER: -- but there's a very 19 immediate interaction here.
20 MS. BALES: Absolutely. So, the RIL 21 itself was reviewed by NRR staff and we had extensive 22 involvement with ensuring that the language in the RIL 23 made sense and was in the right context for NRR. The 24 foreword would be the same. We've drafted it and we 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
63 would show it --
1 MEMBER BALLINGER: My guess is that NEI 2
could have written the foreword. Their concerns are 3
with the use.
4 MS. WEBBER: Well, no. This is Kim 5
Webber. No, NEI cannot write the foreword.
6 MEMBER BALLINGER: I didn't --
7 MS. WEBBER: It's an NRC document.
8 (Laughter.)
9 It's a Research document.
10 MEMBER BALLINGER: No, no. It's the wrong 11 PhD thesis supervisor. Okay.
12 But my point is, the industry's concerns 13 would be addressed in a foreword, would likely be 14 addressed in a foreword.
15 MS. BALES: It could be. I mean, really 16 the foreword in my mind was really coming out of the 17 concerns that the ACRS members asked and the kind of 18 questions that we got in this forum.
19 But it's not even just that. I think the 20 more eyes that got onto the RIL, the more that we 21 became aware of the things that weren't said and that 22 needed to be said. So, it's really just a fact of 23 dissemination. The more people that see it, the more 24 views that we can collect, and to the extent that we 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
64 are aware of potential concerns, we hope that the 1
foreword addresses it.
2 It may not address all concerns. It's not 3
designed to address all concerns. It's designed to 4
put the RIL in context, because we started to see, as 5
we presented it, that some of that context was missing 6
and it was critical and it led to misunderstandings.
7 VICE CHAIRMAN REMPE: Can a foreword 8
suggest this might be a great place to use a risk-9 informed approach, or something like that? I mean, 10 are you allowed to do something like that, like they 11 did with GSP-191?
12 MS. BALES: I think that is something we 13 should talk more about.
14 VICE CHAIRMAN REMPE: I'm just curious.
15 Yes, I'm not sure how far you can go with a foreword.
16 MS. WEBBER: Yes, I mean, quite honestly, 17 you're talking about a whole different set of 18 analysis.
19 VICE CHAIRMAN REMPE: Yes.
20 MS. WEBBER: You know, that's much broader 21 than just the RIL.
22 VICE CHAIRMAN REMPE: It is, but knowing 23 that this is a design basis type of thing, and there 24 have been other examples in the agency where, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
65 suddenly, people wills start thinking about the low 1
likelihood, and things like that. This issue, it's a 2
way for Research -- and again, it's your perspective, 3
and whatever comes out of the letter that other 4
members are going to be writing -- but it just seems 5
like this would be a good forwarding-thinking 6
suggestion for Research, that even though it's a 7
design basis event -- and it was just a thought.
8 MEMBER BALLINGER: Yes, one last thing, I 9
guess. When I read through the RIL, I was looking at 10 all the data and everything, and then, I got to the 11 appendix.
12 MS. BALES: Uh-hum.
13 MEMBER BALLINGER: And that struck me as 14 ordering on guidance. Well, it is guidance, actually.
15 There's a suggestion of the model to use. And so, 16 that's what got me a little bit worried that it's not 17 information; it's guidance.
18 MS. BALES: So, I think we had to be 19 really careful with the language that we chose, and I 20 think we made an effort to scrub things that smelled 21 like guidance. I think the disclaimer at the 22 beginning of the RIL has to stand in for any 23 interpretation. It clearly says this is not guidance.
24 And if the language is received that way, then, you 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
66 know, we can look at it again, but I think that the 1
disclaimer at the beginning of the document should 2
supersede it.
3 MEMBER BALLINGER: Yes, I'm not a lawyer.
4 So, I don't know what magic words get interpreted. I 5
looked at it as guidance.
6 MS. BALES: So --
7 CHAIRMAN SUNSERI: I'm kind of thinking of 8
this as the Committee has delved into deliberation at 9
the same time we're getting your presentation.
10 MS. BALES: Yes, I was just going to say, 11 I'm kind of locked up --
12 CHAIRMAN SUNSERI: I'll be lenient with 13 the time because we have a
whole hour for 14 deliberation. We have some other things that we need 15 to do during that time, but, please, just go ahead 16 with your presentation. Get the points you want.
17 We'll have time for NEI. Even if it's after 10:00, 18 we'll accommodate them. But more than accommodate 19 them, we want to hear from them. But go ahead with 20 your presentation and give your key points.
21 MEMBER PETTI: I suspect, Matt, at this 22 point, I think we can still write a letter.
23 CHAIRMAN SUNSERI: So, can you talk more 24 into the mic?
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67 MEMBER PETTI: I still think we can write 1
a letter in this meeting. We're delaying, you know, 2
we know what February and March is.
3 CHAIRMAN SUNSERI: Yes, yes.
4 MEMBER PETTI: It's just we're making our 5
own -- I trust them to write a credible foreword to 6
put this in context.
7 CHAIRMAN SUNSERI: Yes, yes, yes.
8 VICE CHAIRMAN REMPE: And we can offer 9
suggestions on what's in it.
10 MEMBER PETTI: Right. We can put some in 11 the letter, but I don't --
12 CHAIRMAN SUNSERI: Yes, I think they're 13 getting what they want out of this, a lot of feedback 14 from this Committee --
15 MS. BALES: Uh-hum.
16 CHAIRMAN SUNSERI: -- and we'll formalize 17 it in our letter, but there's other informal stuff 18 that you're already probably going around as well.
19 So, please continue, Michelle.
20 MEMBER BALLINGER: So, that's new slide 21 No. 4.
22 MS. BALES: No, no, no, this was in there 23 before.
24 MEMBER BALLINGER: Oh.
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68 MS. BALES: I promise you there's only 1
three new slides, and we've now covered them all.
2 This was very briefly discussed at the 3
Subcommittee meeting, and I'm only briefing going to 4
acknowledge it here. The RIL doesn't discuss 5
consequences. It simply acknowledges the technical 6
disciplines that could need to be analyzed for 7
consequences and points to the mention of those same 8
topics that have been in our documents since 9
NUREG-2121 and 2015. There's nothing new there.
10 I mentioned before --
11 MEMBER BLEY: I'm sorry.
12 MS. BALES: Yes?
13 MEMBER BLEY: Is somebody actively at work 14 on considering those issues, and are we going to hear 15 about that at some point?
16 MS. BALES: So, I think coming to the 17 concept of working the problem backwards, and 18 understanding where does the investment need to be 19 made --
20 MEMBER BLEY: Uh-hum.
21 MS. BALES: -- there was a point where I 22 think we believed that many of the licensing 23 approaches would use a demonstration of no burst --
24 MEMBER BLEY: Okay.
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69 MS. BALES: -- as a path forward to 1
disposition fuel dispersal. So, basically, they, you 2
know, the vendors, could introduce sort of operating 3
limits for high burnup fuel that ensured that they 4
were not operated in a manner that would eventually 5
burst.
6 If that is a licensing approach taken, 7
there's no need to look at consequences because those 8
consequences only arise in the event of dispersal.
9 The research that would be needed --
10 MEMBER BLEY: Well, I guess I hang on that 11 one a little bit from what we talked about a little 12 while ago, which is if we do get internally, because 13 of all this cracking, you'll actually get some 14 reconfiguration so we're highly packed, it might not 15 be the burst phenomena we've seen so far; it might be 16 something more akin to what we saw 50 years ago. Yes.
17 MS. BALES: So, when I talk about the 18 consequences on that slide, I'm talking about, 19 specifically, the consequences of dispersal, but 20 you're right that relocation and packing fraction are 21 also addressed are also addressed in the RIL.
22 There are models already in some fuel 23 performance codes that predict fuel relocation and 24 actually have packing fractions, and those could be 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
70 further validated with existing data or new tests.
1 MEMBER BLEY: Okay.
2 MS. BALES: So, I don't think of the hill 3
as as high to climb in that area. The assessment of 4
consequence analysis I think is going to be really 5
challenging because a lot of analytical tools that 6
could be brought to bear are not based on the exact 7
conditions that are occurring here.
8 MEMBER BLEY: Right.
9 MS. BALES: Whether they're actually valid 10 for this type of analysis is not obvious to me. So, 11 that seems like an analytical exercise that warrants 12 a lot of scrutiny.
13 MEMBER BLEY: Yes, I agree, and back to my 14 question, is anybody at Research working on that 15 already and under some support?
16 MS. WEBBER: So, this is Kim Webber.
17 MEMBER BLEY: And if they see something 18 happening, we'll hear from them?
19 MS. WEBBER: You know, we've talked a lot 20 about that, quite honestly, about using some of our 21 thermohydraulic codes to assess that, but the 22 challenge, as Michelle said, is there's no way to 23 validate what goes on in the code. So, it's not like 24 we haven't -- so, we've talked about it. I'm not sure 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
71 we have talked with our partner office about the 1
extent of doing that kind of analysis or calculation.
2 So, it's something that we have discussed, but we 3
haven't moved forward on it.
4 MEMBER BLEY: It's good you're thinking 5
about it.
6 MS. WEBBER: Yes.
7 MEMBER BLEY: So, that part is good. And 8
I suspect if you do modeling and you see something 9
that's interesting, that would suggest how we might 10 get experiments to help out.
11 MS. WEBBER: Correct.
12 MEMBER BLEY: Okay.
13 MS. WEBBER: Yes, thanks, Dennis.
14 MS. BALES: So, I'll spend a couple of 15 minutes talking about limitations, because this has 16 also already come up. In a highly empirical document 17 like the RIL, we already talked about it's not 18 possible to extrapolate beyond where the experiments 19 have gone.
20 Two that come to mind particularly are 21 doped fuel and coated claddings. It's physically 22 possible that doped fuel, which has advertised as 23 different transient fission gas retention behavior, 24 could have an impact on FFRD, and coated claddings 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
72 have been shown in some cases to have different 1
ballooning and burst behavior. And we've seen that 2
ballooning and burst behavior as key to the phenomena 3
that we're concerned about here.
4 Today, the RIL would not cover doped fuel 5
or coated cladding, and the RIL states that. But we 6
imagine that this would be an area that, with some 7
additional information, could be addressed in perhaps 8
a revision to the RIL.
9 We already talked about the second one a 10 little bit here. The prediction of cladding strain is 11 a key factor in using the limits presented in the RIL, 12 and I think more work should be done to validate 13 models for balloon length, for example.
14 Burst opening size. We didn't get into 15 this. It's in the slides and we covered it in the 16 Subcommittee. But burst opening size is a key 17 determinant for how much fuel dispersal that you would 18 expect, and models today are not calibrated to burst 19 opening size. Work that could develop such a model 20 would be incredibly valuable to reduce the 21 conservatism on dispersal quantities. That's for them 22 in the RIL.
23 The first point on this slide about 24 burnup, I didn't talk about it too much here, but I 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
73 think we talked about it in the Subcommittee, that all 1
of the empirical limits are presented as a function of 2
burnup, but even though we don't have a fully 3
mechanistic understanding, it's very reasonable to 4
expect that burnup is not the primary determinant for 5
these phenomena. It's probably something like 6
porosity or other sort of local, microscopic fuel 7
pellet features.
8 And if further research really delved into 9
some of those parameters, we may be able to derive a 10 function, some of these limits as a function parameter 11 other than burnup that reduces the scatter that we've 12 seen in the burnup plots.
13 So, SCIP-IV is a continuation of the 14 SCIP-III program. We expect that that program may 15 address some of these limitations that we've already 16 identified.
17 And we talked a little bit about analysis.
18 We pointed to the work that was done in 2015. There 19 is work to revisit the approach that was used in 2015 20 to draw the conclusion that this wasn't an immediate 21 safety issue. We want to be able to replicate that 22 kind of calculation easily and perhaps for NRR on a 23 confirmatory basis as applications come in. So, we're 24 building our tools to allow for that. And those are 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
74 the two main things that we're going to be active on 1
in the next year or so.
2 But I think to pull back when I think 3
about the RIL as a foundation for the next step, I see 4
it as this is what we know today. It identifies some 5
of the gaps. It explains what we know, but also a 6
little bit about what we don't know. And I fully 7
expect that some of those gaps will be filled in.
8 And if there's a
more mechanistic 9
understanding, there could be a point in the future 10 where the RIL is completely superseded by a better 11 understanding. That would be completely acceptable.
12 That does not negate the value of the RIL today. What 13 it does is prompt a conversation that's meaningful, 14 that's looking at what really matters.
15 And so, when I think about the RIL as a 16 foundation for the next steps and a potential for the 17 building that grows on top of it to be really more 18 relevant than the foundation itself, I think that 19 helps to put the RIL in context. It's what we know 20 today, and it should form the basis for ongoing 21 discussion about where there is value.
22 And as I mentioned also, licensing 23 approaches have a huge role to play. What licensing 24 approaches require will vary, and where the investment 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
75 needs to be made in order to do additional research, 1
additional analysis, kind of all comes from how far 2
the RIL, how close the RIL gets to serving the 3
licensee needs. And to the extent that it doesn't get 4
all the way there to a licensing approach, it defines 5
the work that needs to be done in a way that I don't 6
think is being done right now.
7 MS. WEBBER: Can I also add, so in terms 8
of what's next also, you know, because we did hear the 9
comments that NEI made at the Steering Committee 10 meeting, you know, we're also aware that there is 11 interest in providing feedback on the RIL. And, yes, 12 so we've talked internally about, when there is new 13 research that is available that will help understand 14 or expand the understanding of this phenomenon, we can 15 always revise the RIL to include whatever research is 16 going to be made available over the next several 17 years, especially with SCIP-IV.
18 The other thing that we did talk about is 19 that, beyond the RIL with the development of any kind 20 of regulatory guidance, there's always opportunities 21 for stakeholders to express their views and opinions 22 on whatever regulatory guidance may be developed as a 23 result of that.
24 Additionally, because this is such a high 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
76 visibility topic with industry, we have frequent 1
engagements with industry on topics such as this. And 2
I know that Joe Donoghue is leading the charge to plan 3
a high burnup workshop. So, that will be a public 4
engagement where NRC and the industry will make 5
presentations on various topics associated with high 6
burnup.
7 Additionally, there are technical meetings 8
between the staff and international counterparts, 9
including EPRI, where this topic will be discussed in 10 further detail.
11 So, I just wanted to put that kind of 12 wrapper around some additional notions of what's next.
13 CHAIRMAN SUNSERI: All right. Is that 14 concluding your remarks?
15 MS. BALES: Yes, at this point, the only 16 material that would kind of go into the technical 17 basis is if there are specific questions. But I think 18 all of the key points have been made in --
19 CHAIRMAN SUNSERI: I think you all 20 thoroughly did that during the Subcommittee remarks.
21 Okay. Good. Well, thank you. That was 22 very, very informative.
23 Ron, do you have other --
24 MEMBER BALLINGER: Yes, now we have NEI.
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77 I think they're still on standby.
1 DR. CSONTOS: Yes, all set.
2 MEMBER BALLINGER: And Al is in.
3 Since we've gone a ways over, should we 4
take a five-minute break?
5 CHAIRMAN SUNSERI: We can take a five-6 minute transition.
7 MEMBER BALLINGER: So, then, NEI get their 8
slides and --
9 CHAIRMAN SUNSERI: Yes, get their slides 10 up.
11 MEMBER BALLINGER: -- make sure everything 12 works?
13 CHAIRMAN SUNSERI: Yes, that would be 14 fine.
15 MEMBER BALLINGER: So, we'll take a five-16 minute break.
17 CHAIRMAN SUNSERI: We'll resume at 10 18 after.
19 MEMBER BALLINGER: Yes, 10 after, five 20 more minutes, 4 minutes and 49 seconds.
21 (Laughter.)
22 CHAIRMAN SUNSERI: Did I read that wrong?
23 Okay, we'll make it 15 after then.
24 MEMBER BALLINGER: Make it 15.
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78 CHAIRMAN SUNSERI: You know, there's three 1
clocks in here. Sorry.
2 Fifteen after.
3 MEMBER BALLINGER: Fifteen after.
4 (Whereupon, at 10:05 a.m.,
the 5
foregoing matter went off the record and went 6
back on the record at 10:15 a.m.)
7 CHAIRMAN SUNSERI: Hey, welcome back.
8 I will reconvene the ACRS meeting at this point 9
and I'll transfer it back to Member Ballinger, 10 who will go to the NEI presentation.
11 MEMBER BALLINGER: Thank you, Mr.
12 Chairman. Thank you, Mr. Chairman.
13 I guess we just turn it over to Al 14 Csontos and go with the presentation.
15 DR. CSONTOS: Okay. Can you hear me 16 okay?
17 MEMBER BALLINGER: We can. I can.
18 DR. CSONTOS: Okay. Thank you.
19 Yes, I wanted to say thank you to the 20 Committee for providing us this opportunity to 21 present our industry comments and perspectives on 22 the RIL.
23 CHAIRMAN SUNSERI: Keep going.
24 DR. CSONTOS: We're good?
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79 CHAIRMAN SUNSERI: I'll silence.
1 Please hold on for me.
2 DR. CSONTOS: Good to go?
3 CHAIRMAN SUNSERI: Okay. All right.
4 Go ahead.
5 DR. CSONTOS: Okay. Thanks.
6 So, I just want to say thanks again 7
for providing the opportunity to provide our 8
comments and our perspectives on the RIL.
9 Really, the comments that we're going 10 to have here and the concern really is an echo of 11 both the Subcommittee and the full Committee 12 (audio interference) with the staff. Really, 13 it's we're rehashing much of the same questions 14 and comments that you have provided.
15 We will start with two slides on general 16 overarching comments, two slides or three slides on 17 specific technical comments. And these are just three 18 that we picked. We have numerous more comments that 19 we could provide, but in the time allotted, we thought 20 providing you these three specific comments would 21 suffice. Okay?
22 So, yes, we just heard the concerns of the 23 extension of the RIL to regulatory application. And 24 the industry agrees with that question. And we also 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
80 agree with the staff position in the SECY letter in 1
2015, 0148, with respect to the FFRD research not 2
indicating a
need to require additional new 3
requirements in the 50.46 rulemaking.
4 And I just want to say that we heard the 5
concept of the foreword. That's a great -- you know, 6
I fully support the concept of the foreword. I do not 7
support the notion that we're going to write the 8
foreword, but folks are on to say no. We do not 9
anticipate -- we're hoping to see that ahead of time 10 as well, so we can comment on that.
11 But, really, ultimately, the bottom line 12 is that we believe there are significant benefits for 13 taking the time to consider and incorporate a broader 14 technical review and comment period, like other NRC 15 documents, NUREGs or similar to RIL-1101, which 16 provided multiple rounds of review and comment periods 17 from the broader technical community, including 18 industry technical experts.
19 In fact, yesterday, we got an email from 20 an international technical fuel expert asking how they 21 can provide comments to the RIL because of the concern 22 that we're going to highlight in the next slide, which 23 is the significant amount of conservatisms that they 24 see in the RIL. And so, we asked them to participate 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
81 or to call into the meeting, but we're not sure if 1
they are, if they made it and will provide comments 2
here.
3 But, anyway, this is slide 3, and a bit 4
more general comment. As written today, the draft RIL 5
is a conservative application to certain thresholds 6
and models from specific datasets. And this draft RIL 7
may be incomplete, in the absence of appropriate 8
assessments of certainly the levels of conservatisms 9
and, also, to assess the complexity of the technical 10 topic. There just seems to be that there's an 11 excessive conservatism in the RIL.
12 Secondly, the RIL does not offer an 13 interpretation of the uncertainties or conservatisms 14 within the experimental database -- experiments using 15 nuclear heating versus experimental electrical (audio 16 interference) heating, for example.
17 And again, we just want to reiterate that, 18 per the past person I talked about, the RIL-1101, we'd 19 like to have an opportunity to provide our technical 20 comments prior to the publication, just the broader 21 technical consensus.
22 Next slide.
23 So, the specific examples now. We've 24 identified a couple of inconsistencies in the report, 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
82 and we thought we'd just highlight them here, and 1
maybe the staff can take a look at them and maybe 2
revise or do what they will with it.
3 But the RIL references Argonne National 4
Lab Test ICL No. 2 as a primary basis for establishing 5
the fragmentation critical pellet average burnup of 55 6
gigawatt days per MTU. And those tests, though, used 7
BWR, so the rod average burnup between 55 to 57, which 8
would imply higher local burnup throughout the middle 9
section of the rod. And we confirmed this through 10 email correspondence with Mike Malone, that that's 11 probably around 64, approximately 64. Okay?
12 So, figure 3 in the report shows two data 13 points near 60 gigawatt days per MTU with fine 14 fragmentation near zero. And those PWR rods were 15 tested within the FISA program, with a rod average of 16 55.2 gigawatt days per MTU, and showed no fuel loss 17 during the LOCA test.
18 The SCIP-III results at the segment formed 19 of 50 gigawatt days per MTU in figure 3 indicates a 20 relatively small degree of fine fragmentation compared 21 with the test with second burnup exceeding 65. The 22 specific test was a BWR rod. And while some smaller 23 fine fragments were observed, the majority of the 24 fragments were greater than 2 millimeters, contrary to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
83 figure 3 in the draft RIL. And in the SCIP-III 1
program, it states that 90 percent of the fragments 2
were larger than 1 millimeter.
3 So, based on the test data, the onset of 4
the measurable fine fragmentation so, the 5
conclusion could be altered based upon some of these 6
discussions of the dataset. And based on that test 7
dataset, the onset of measurable fine fragmentation 8
appears to be near 50, not 55. So, I just want to 9
bring that out to you.
10 Next slide.
11 So, the RIL states that the staff 12 recommends a model that will predict the mass of the 13 fuel dispersal to be -- you know, I don't want to read 14 it to you, but this approach right here we see as 15 having several unnecessary conservatisms. It ignores 16 the effect of the burst opening area. These are 17 comments, you know, in a lot of ways they're very 18 similar to the comments that were made by the ACRS 19 Subcommittee and full Committee, but we're going to go 20 into specifics there.
21 The burst
- area, you
- know, that's 22 demonstrated in SCIP-III shows a strong influence of 23 the amount of dispersed, but that goes to some of the 24 comments about the consequences. It ignores the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
84 effect of fragment size distribution, which has also 1
been demonstrated in SCIP-III to be important. And it 2
ignores the core-wide average in effect of individual 3
rod uncertainties in terms of the conduct of the fuel 4
dispersal analysis with respect to large, you know, 5
over 100 number of rods. And in this case, we're just 6
saying that these are more accurate ways to possibly 7
look into some of these areas.
8 Next slide.
9 And we wanted to highlight that there are 10 other interpretations of FFRD-related phenomena with 11 the same datasets. And so, here are three examples.
12 I remember in the Subcommittee there was a lot of 13 discussion about the Capps paper. We threw in two 14 more. Now these reports and these papers were cited 15 in the RIL, and they acknowledge the complexity of the 16 phenomena. Michelle just talked about the complexity 17 of the phenomena and the different database.
18 But the question here about going to 19 conservative interpretations with the draft RIL is 20 really, you know, it's limiting, we think, the benefit 21 and the value of the RIL.
22 So, last slide. You know, in summary, 23 three major points that we just want to make.
24 We believe this is a
conservative 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
85 treatment of a highly complex technical topic. We 1
talked about this or the ACRS talked about this just 2
before me with Michelle's presentation. A lot of 3
dependencies.
4 We are concerned with the extension of 5
this draft RIL to regulatory application. The 6
foreword does help, but having a broader technical 7
consensus or a broader technical community review and 8
comment on the draft RIL, like the NRC did with the 9
RIL-1101, we think will provide benefits to NRC and 10 subsequent application to the regulatory domain by 11 providing a broader technical consensus and more 12 technical, I guess you could say robustness in terms 13 of getting the broader community to speak to it.
14 But, you know, I think I'll end up with I 15 think one of the ACRS members mentioned, asked the 16 question of why the rush. And I think that's what 17 we're wondering, too. And we would really like to see 18 about getting a broader consensus here by going 19 through at least a round of review of our comments to 20 be updated or to be revised in the current draft RIL, 21 because the RIL is still draft.
22 And that's our concluding remarks.
23 MEMBER BALLINGER: Thank you.
24 Let's see, how should we proceed? Should 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
86 we have a little period of Q&A from the Committee?
1 CHAIRMAN SUNSERI: We do, but I don't want 2
to overlook the public comments.
3 MEMBER BALLINGER: Yes, I'm just trying to 4
-- which comes first? Maybe we should have public 5
comments first?
6 CHAIRMAN SUNSERI: I think we should call 7
for public comments now.
8 MEMBER BALLINGER: Okay. I'm assuming 9
that there are people listening, and that if they 10 would like, if the members of the public would like to 11 make a comment, is it still *6?
12 CHAIRMAN SUNSERI: *6.
13 MEMBER BALLINGER: *6, and make your 14 comment, please. There's a lot of phone numbers 15 there.
16 CHAIRMAN SUNSERI: So, just let me restate 17 that clearly. Members of the public, if you wish to 18 make a comment, you can do so at this time by unmuting 19 your line and using *6, state your name, and provide 20 your comment.
21 Additionally, if you like, you can send us 22 written comments as well. Send them to the Designated 23 Federal Officer, Zena Abdullahi.
24 (Pause.)
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87 Any comments?
1 (No response.)
2 All right. That's the public.
3 I would also extend the courtesy to 4
anybody on the Teams invite, if they want to make a 5
comment.
6 (No response.)
7 All right. I'm not hearing any. So, Ron, 8
I guess you can take it back and facilitate any 9
questions from the Committee now.
10 MEMBER BLEY: Yes, I have a question about 11 process, I guess. I'm definitely unfamiliar with the 12 RIL, and we have never, as far as I can remember, had 13 a presentation of a RIL before the Committee. I don't 14 think so.
15 MEMBER BALLINGER: That's --
16 MEMBER BLEY: Am I wrong?
17 MEMBER BALLINGER: Yes.
18 (Laughter.)
19 MEMBER BLEY: Well, I'm sometimes wrong, 20 but never in doubt.
21 MEMBER BALLINGER: But that's not really 22 relevant to our discussion.
23 MEMBER BLEY: Okay, but another part of 24 this might be that, were this to be used to produce a 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
88 guidance document, would the review process by the 1
public comment process of a guidance document, would 2
that be one way to do it? I mean, what Al is 3
proposing is that you have, in effect, a review 4
process of a RIL. I'm just curious.
5 MEMBER HALNON: One thing, I'm concerned 6
if you get to the guidance portion, we're so far down 7
the road that --
8 MEMBER BLEY: Yes.
9 MEMBER HALNON: -- to effect a significant 10 change or eliminate the guidance is going to be almost 11 difficult. There's got to be something before that.
12
- And, Kim, you mentioned a
lot of 13 interactions, but it sounded like they were kind of 14 anecdotal interactions as opposed to physically, I 15 mean specifically on this RIL and the conclusions, you 16 know, interim conclusions being made by the RIL.
17 MS. WEBBER: Yes. So, the interactions 18 that I was speaking about are really to talk about the 19 information in the RIL in a public setting. So, 20 that's the intent of the public interactions as we 21 envision them today.
22 I don't know if that clarifies your --
23 MEMBER HALNON: Do you see a GSI coming 24 down the road from this? Or is it too early to tell?
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89 MS. BALES: So, I didn't mention it in 1
this presentation, but there was a Generic Issue 2
Opinion for fuel dispersal sort of in parallel with 3
the rulemaking activity. And there was --
4 MEMBER HALNON: That's 50.46(c)?
5 MS. BALES: Correct. Sorry. A 50.46(c) 6 rulemaking. And the disposition of that was closely 7
linked to 50.46(c). So, that's sort of a different 8
subject, whether that conclusion would still be valid.
9 But it was already envisioned that this could be 10 something that needed to be addressed and --
11 MEMBER HALNON: So, that GS is still open 12 then?
13 MS. BALES: It's been closed, based on, at 14 the time, plans with the rulemaking.
15 MEMBER HALNON: So, I guess I would 16 encourage some specific discussion, since this has got 17 such wide-ranging impact down the road. And it sounds 18 like the industry is coming in with kind of an 19 opposing view, saying that we can go bigger. You're 20 saying we can go smaller. You know, it's he says; she 21 says at this point, but somewhere we've got to come to 22 a meeting of the minds, so there's not a lot of 23 resources wasted on both sides trying to get a limit 24 that no one is going to be able to buy into because of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
90 incomplete information.
1 MS. BALES: So, there's a lot of ways that 2
we can answer the question. I think what I'd say is 3
that the RIL is a summary of existing information.
4 Should new information become available, especially 5
information that contradicts or expands the limits in 6
a different direction, we would have to review the 7
RIL.
8 Without new information, if it's really 9
just a matter of interpreting and discussing how to 10 view the existing information, I think that that is a 11 totally valid thing to happen within the guidance 12 development process. The guidance development process 13 with public meetings and public comment periods would 14 allow for that interaction.
15 I don't think that the existence of the 16 RIL and statements in the RIL would overly restrict 17 the discussion that could come from a guidance.
18 Because, really, in guidance, you start to examine how 19 the information will be applied; where uncertainties 20 would be treated.
21 And so, I think one of the reasons that 22 it's convenient to use a RIL is there is some 23 flexibility in the process. I mentioned that ACRS is 24 not required; peer review is not required. In this 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
91 case, we elected to do both because we felt that that 1
was something that would enhance the value of the RIL.
2 So, I don't want to say that, you know, 3
it's a really rigid process, but it's something that 4
we should understand where fits in this bigger 5
picture, and guidance has its own process that allows 6
for some interaction that I think is what industry is 7
pointing to, the need to understand how it's applied.
8 MEMBER HALNON: Okay.
9 MS. BALES: I'm not sure that going into 10 the RIL and massaging what it says is really going to 11 get there.
12 MEMBER HALNON: Yes. No, I'm not 13 suggesting changing the RIL, because you're right, it 14 is what it is from the standpoint of the data. The 15 foreword that you write, though, should probably 16 recognize that whenever you put a number out there, it 17 gets legs --
18 MS. BALES: Uh-hum.
19 MEMBER HALNON: -- and it tends to start 20 becoming normal language to people, and it becomes now 21 a brighter and brighter line that's impossible to 22 cross because it's out there.
23 MS. BALES: Uh-hum.
24 MEMBER HALNON: So, I would suggest that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
92 the foreword be very specific to that point, that this 1
is not meant at this point to be any kind of 2
regulatory limit or suggest a limit or, you know, be 3
used going forward with guidance without additional 4
information, whatever the -- your language, not mine.
5 But I'm just concerned that, you know, having it -- we 6
all love a number.
7 MS. BALES: Yes.
8 MEMBER HALNON: We all love bright lines, 9
and we tend to equate those two together when we see 10 it.
11 MS. BALES: Yes.
12 CHAIRMAN SUNSERI: Any other member 13 comments, questions?
14 MEMBER BALLINGER: Other comments?
15 MEMBER PETTI: Yes, just one. I was a 16 little concerned on the NEI's technical comment about 17 the burnup. I think we should run that through Al.
18 When I first saw the 55, what struck me in 19 Subcommittee was it's based on a photomicrograph.
20 That's all we have. But it sounds like there's more 21 than that. There's no quantitative, because it was 22 done, I guess, a while ago, before, let's say, we had 23 the protocols in place that they have now for SCIP 24 and --
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
93 MS. BALES: Right. So, I agree with you 1
that -- you know, I saw that comment this morning and 2
looked up in the NUREG, and we need to clarify that in 3
the RIL because it is accurate to say that the value 4
for that was the right average, where the rest of the 5
reported results are segment averages.
6 What I'll say, though, is a few points.
7 One, SCIP-IV is looking at the range between 40 and 60 8
because there's so little data --
9 MEMBER PETTI: That was my other question.
10 So, great.
11 MS. BALES: Yes. No, it's something that, 12 I mean, the whole SCIP community has been scrutinizing 13 these results, too, and recognizes that we really 14 don't have a good picture of the transition because 15 our last known fine fragmentation is at 45, and then, 16 we don't get anything until 60 in some cases that 17 there has been fragmentation observed.
18 And you're right that the SCIP protocol 19 quantifies the fragment size and micrograph does not.
20 And that makes it a mismatch in the robustness of 21 that, to anchor the point. But I expect that, with 22 SCIP-IV data, we'll learn more.
23 But, also, the trendline that we would 24 have drawn, if we only had the SCIP data, would have 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
94 intersected at 55 anyway. Because, as I said, where 1
we know that there was no fine fragmentation was at 2
45, and then, at 60, there was already some. It was 3
small, but there was some. And so, it's somewhere 4
below 60.
5 MEMBER PETTI: That's probably worth a 6
footnote in the document, I think. You know, that, 7
hey, if you take that out, you're --
8 MS. BALES: No, I think that that's --
9 yes.
10 MEMBER PETTI: That's all.
11 MS. BALES: Yes.
12 CHAIRMAN SUNSERI: Anybody else?
13 (No response.)
14 All right.
15 MEMBER BALLINGER: No others? Okay, I'll 16 turn it back to you.
17 CHAIRMAN SUNSERI: Well, okay. Thank you, 18 Ron. Thank you, Staff. Thank you, NEI, for the 19 presentations. I found them to be all informative.
20 I think the Committee did as well, based on the 21 questions I heard asked here. So, thank you for 22 taking the time to put that together.
23 So, at this point, we do have a draft 24 report letter, a letter report, that we are preparing.
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
95 And I'd ask Ron, if you want to pull that up, we'll do 1
an initial read-through and see if we can get 2
Committee major comments on that. We can go to 11:00, 3
maybe a little after, but not much more.
4 MEMBER BALLINGER: That's fine.
5 (Whereupon, at 10:37 a.m., the Advisory 6
Committee went into closed session.)
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
Research Information Letter 2021-13:
Interpretation of Research on Fuel Fragmentation, Relocation, and Dispersal at High Burnup Briefing of the Advisory Committee for Reactor Safeguards December 1, 2021
This presentation will address FFRD history at NRC The programs cited in the RIL and the peer reviewers used The outcome of the RIL The basis for empirical thresholds included in the RIL Other Matters
This presentation will address FFRD history at NRC The programs cited in the RIL and the peer reviewers used The outcome of the RIL The basis for empirical thresholds included in the RIL Other Matters
Why a RIL?
RILs have been used in the fuels area:
RIL-0401, An Assessment of Postulated Reactivity-Initiated Accidents (RIAs) for Operating Reactors in the U.S.
RIL-0801, Technical Basis for Revision of Embrittlement Criteria in 10 CFR 50.46 A Research Information Letter does not provide guidance.
FFRD history at NRC RIL 2008-01, Technical Basis for Revision of Embrittlement Criteria in 10 CFR 50.46 NUREG-2121, Fuel Fragmentation, Relocation, and Dispersal During the Loss-of-Coolant Accident SECY-15-0148, Evaluation of Fuel Fragmentation, Relocation and Dispersal under Loss-of-Coolant Accident (LOCA) Conditions Relative to the Draft Final Rule on Emergency Core Cooling System Performance during a LOCA (50.46c)
RIL 2021-13, Interpretation of Research on Fuel Fragmentation, Relocation, and Dispersal at High Burnup
This presentation will address FFRD history at NRC The programs cited in the RIL and the peer reviewers used The outcome of the RIL The basis for empirical thresholds included in the RIL Other Matters
Data Sources for RIL 2000 2020 2010 SCIP-III, Hot-cell NRC
@Studsvik, Hot-cell
- ORNL, Hot-cell S
E C
Y
- Halden, In-Pile
Peer Review Group
- Ad hoc, issue-focused group. Reviewers selected with extensive familiarity of FFRD research
- Nathan Capps, ORNL - Author of two significant publications on FFRD, extensive experience modeling aspects of FFRD and collaborator in ORNL FFRD experimental program
- Tatiana Taurines, IRSN - Extensive experience modeling aspects of FFRD and leader in SCIP program review group discussions
- Fabiola Cappia, INL - Collaborator in FFRD publications, lead for INL PIE campaigns of HBU fuel, extensive work examining evolution of fuel microstructure with burnup
- Ken Yueh, EPRI - Designed and led FFRD research campaigns at Studsvik for EPRI and NSUF at ORNL/INL, leader in SCIP program review group discussions
- Daniel Jderns, Studsvik - Collaborator in SCIP experimental design and expert in SCIP results
This presentation will address FFRD history at NRC The programs cited in the RIL and the peer reviewers used The outcome of the RIL The basis for empirical thresholds included in the RIL Other Matters
Hot-cell testing to simulate Loss-of Coolant Accident condition 30-50 cm refabricated fueled segment from commercially irradiated rod Pressure line establishes segment pressure 4 heating elements in furnace
Influence of experimental methods Empirical limits are derived in such a way to be independent of any experimental non-prototypicalities.
Outcome of the RIL:
Identify when FFRD occurs Segment from NRCs ANL LOCA program at 55 GWd/MTU before and after testing
Address five elements of the RES staffs interpretation of FFRD research and describe the technical basis for these elements:
1.
Fine fragmentation threshold 2.
Fuel relocation threshold 3.
Model to quantify dispersal 4.
Document transient fission gas release 5.
Quantify packing fractions in the balloon region Outcome of the RIL:
Identify when FFRD occurs
Outcome of the RIL:
Identify which rods are a concern for FFRD Burnup Power (LHGR) 1st cycle 2nd cycle 3rd cycle Fine fragmentation requires ~55 GWd/MTU Relocation requires balloning Dispersal requires fine fragmentation, relocation and burst
Burnup Power (LHGR) 1st cycle 2nd cycle 3rd cycle Dispersal requires fine fragmentation, relocation and burst For the dispersal zone, some core loadings may result in no region of overlap Overlap influenced by:
- ECCS response
- Plant design
- Loading pattern
- Fuel and cladding design This information is prototypical of PWR. BWRs will have few if any rods susceptible to dispersal due to different operating practices, system pressure, etc.
Burnup Power (LHGR) tFGR influences burst probability 1st cycle 2nd cycle 3rd cycle Transient Fission Gas Release - Increasingly important at higher burnup; Important to accurately predict burst Dispersal requires fine fragmentation, relocation and burst
Relocation packing fraction - Important to accurately predict burst and peak temperature for non-burst high burnup rods Assume the balloon region is 70-85% fuel (15-30% void) by volume for calculating rod behavior Burnup Power (LHGR) 1st cycle 2nd cycle 3rd cycle
- Fine fragmentation
- Not seen below 55 GWd/MTU
- Fuel axial relocation
- Not seen in cladding with less than 3% strain
- Fuel dispersal
- Fine fragmentation and relocation are prerequisites; Therefore, dispersal requires burnup > 55 GWd/MTU, strain > 3%
- Doesnt happen unless theres rupture
- Transient Fission Gas Release
- Increasingly important at higher burnup
- Relocation packing fraction
- Important for non-burst high burnup rods The RIL supports targeted FFRD analysis
This presentation will address FFRD history at NRC The programs cited in the RIL and the peer reviewers used The outcome of the RIL The basis for empirical thresholds included in the RIL Other Matters
Element 1: Empirical threshold at which fuel pellets become susceptible to fine fragmentation Research supports a pellet-average burnup limit of 55 GWd/MTU as the onset of fine fuel fragmentation Segment from NRCs ANL LOCA program at 55 GWd/MTU before and after testing FFRD
Element 2: A local cladding strain threshold below which relocation is limited Research suggests fuel relocation is limited in regions of the fuel rod experiencing less than 3% cladding strain.
NRC test #
Strain threshold, top (%)
Strain threshold, bottom (%)
189 6.0 3.0 191 6.0 4.0 192 5.0 4.0 193 1.0 4.0 196 3.0 5.0 198 4.5 9.0 FFRD
What do dispersal measurements look like?
Element 3: A conservative value for the mass of dispersible fuel as a function of burnup Dispersal during the test
What do dispersal measurements look like?
Element 3: A conservative value for the mass of dispersible fuel as a function of burnup Dispersal during shaking
Element 3: A conservative value for the mass of dispersible fuel as a function of burnup FFRD
Recommend a model to predict the mass of fuel dispersal to be all fuel above the burnup threshold of 55 GWd/MTU in the length of the rod with greater than 3% cladding strain to disperse.
Difference between dispersal predicted by the model and all mobile fuel observed in the experiment SCIP test Mass (g)
Prediction/Measured OL1L04-LOCA-2 125 250%
N05-LOCA
-19 76%
VUR1-LOCA-1 15 109%
WZR0067-LOCA
-16 83%
VUL2-LOCA1
-7 94%
VUL2-LOCA3 8
105%
VUL2-LOCA4 5
102%
ALL collected fuel Element 3: A conservative value for the mass of dispersible fuel as a function of burnup FFRD
Element 4: Provide evidence of significant tFGR that may impact ballooning and burst behavior of high burnup fuel under LOCA conditions Data shows increasing transient fission gas release with burnup. However, many other factors besides burnup impact tFGR (e.g., fuel temperature, stresses in fuel).
Licensees will need to address tFGR in their LOCA evaluation models. Some models exist for tFGR, but more validation of those models is needed.
Element 5: Establish a value for the packing fraction of relocated but non-dispersed fuel in the balloon region It is reasonable to use packing fraction values between 70 to 85 percent for fuel susceptible to fine fragmentation. (Fuel at lower burnup would likely have a lower packing fraction).
To determine the impact on ballooning and burst, it is important to examine a range of packing fractions to account for these effects.
This presentation will address FFRD history at NRC The programs cited in the RIL and the peer reviewers used The outcome of the RIL The basis for empirical thresholds included in the RIL Other Matters
Discussion of Consequences and Consequence Modeling
- Refers to SECY-15-0148 and NUREG-2121
- Reiterates potential safety concerns associated with FFRD:
- energetic fuel-coolant interactions
- recriticality of dispersed fragments
- core coolability and long-term decay heat removal
- radiological impacts, including control room dose and equipment qualification*
- Being addressed outside of the RIL, as part of an update to Regulatory Guide 1.183, Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors.
Limitations of the Empirical Database
- Limits are not applicable to doped fuel or coated cladding.
- Additional research could demonstrate that the limits in the RIL apply or are bounding
- Note doped fuels have different FGR behavior, so it would be important to understand implications on FFRD
- Note coated claddings have been shown to have less strain and smaller burst openings, which could mean better performance with respect to FFRD
Limitations of the Empirical Database
- Limits are simplistic, derived as a function of burnup only.
- Burnup is likely a surrogate for more direct variables such as porosity, stresses within the fuel pellet, grain growth and subgrain formation. These features are likely influenced by operating history
- Additional research to allow for more mechanistic treatment of these variables could allow for refinement of the limits
- Limits anticipate accurate prediction of cladding strain along the axial length of a fuel rod. Burst opening size is presumed to be stochastic and therefore limits assume large opening size.
- Additional research to validate balloon height, axial strain profile and burst opening could allow for refinement of the limits
RIL Whats next?
- Participating in SCIP IV
- Includes testing of non-standard fuel
- Additional testing to characterize tFGR
- Testing in the mid-level burnup range
- Refining analysis tools to improve core-wide FFRD analysis
- Building from 2015 and MELLLA+ experience
- Enhancing resolution and realism
- Utilizing new modeling features
RIL Whats next?
- RIL will establish foundation for next steps
- Industry can build from the RIL based on their licensing needs, justifying design specific limits
- Researchers can build programs from the RIL that produce the information needed to go further
RIL in context LOCA initiating event frequency LOCA cond. 1 LOCA cond. 2 LOCA cond. 3 LOCA cond. 4 Fuel response to LOCA conditions System response to dispersed fuel Comparison of safety analysis to licensing basis RIL
Questions?