ML19317C747
| ML19317C747 | |
| Person / Time | |
|---|---|
| Issue date: | 09/16/2019 |
| From: | Weidong Wang Advisory Committee on Reactor Safeguards |
| To: | |
| Wang, W, ACRS | |
| References | |
| NRC-0570 | |
| Download: ML19317C747 (108) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Thermal-Hydraulic Phenomena Subcommittee Docket Number: (n/a)
Location: Rockville, Maryland Date: Monday, September 16, 2019 Work Order No.: NRC-0570 Pages 1-84 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005 (202) 234-4433
1 1
2 3
4 DISCLAIMER 5
6 7 UNITED STATES NUCLEAR REGULATORY COMMISSIONS 8 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 9
10 11 The contents of this transcript of the 12 proceeding of the United States Nuclear Regulatory 13 Commission Advisory Committee on Reactor Safeguards, 14 as reported herein, is a record of the discussions 15 recorded at the meeting.
16 17 This transcript has not been reviewed, 18 corrected, and edited, and it may contain 19 inaccuracies.
20 21 22 23 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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1 1 UNITED STATES OF AMERICA 2 NUCLEAR REGULATORY COMMISSION 3 + + + + +
4 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5 (ACRS) 6 + + + + +
7 THERMAL-HYDRAULIC PHENOMENA SUBCOMMITTEE 8 + + + + +
9 OPEN SESSION 10 + + + + +
11 MONDAY 12 SEPTEMBER 16, 2019 13 + + + + +
14 ROCKVILLE, MARYLAND 15 + + + + +
16 The Subcommittee met at the Nuclear 17 Regulatory Commission, Two White Flint North, Room 18 T2B10, 11545 Rockville Pike, at 1:00 p.m., Joy Rempe, 19 Chair, presiding.
20 21 COMMITTEE MEMBERS:
22 JOY L. REMPE, Chair 23 RONALD G. BALLINGER, Member 24 MICHAEL L. CORRADINI, Member 25 WALTER KIRCHNER, Member NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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2 1 JOSE MARCH-LEUBA, Member 2 HAROLD B. RAY, Member 3 PETER RICCARDELLA, Member*
4 MATTHEW SUNSERI, Member*
5 6 DESIGNATED FEDERAL OFFICIAL:
7 WEIDONG WANG 8
9 ALSO PRESENT:
10 STEVE BAJOREK, RES 11 JOSH BORROMEO, NRR 12 MIRELA GAVRILAS, NRR 13 PAUL KLEIN, NRR 14 JANE MARSHALL, NRR 15 SCOTT MOORE, Executive Director, ACRS 16 BENJAMIN PARKS, NRR*
17 DAVID RUDLAND, NRR 18 ASHLEY SMITH, NRR 19 STEVE SMITH, NRR 20 21 *Present via telephone 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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3 1 P R O C E E D I N G S 2 (1:07 p.m.)
3 CHAIR REMPE: This meeting will now come to 4 order. This is a meeting of the Thermohydraulic 5 Phenomenon Subcommittee of the Advisory Committee on 6 Reactive Safeguards. I'm Joy Rempe, Chair of today's 7 subcommittee meeting. Members in attendance are Mike 8 Corradini, Ron Ballinger, and Harold Ray.
9 We also have Matt Sunseri and Pete 10 Riccardella, who have joined us on the line, and we 11 expect Walt Kirchner to arrive later during this 12 meeting. Members Matt Sunseri and Pete Riccardella 13 are connected using a public line, so they are on 14 mute, but I will try hard to remember to periodically 15 ask that that line be opened so they have an 16 opportunity to ask questions.
17 Weidong Wang of the ACRS staff is the 18 designated Federal official for this meeting. During 19 today's meeting, the subcommittee will review a staff 20 technical report, technical evaluation report of in-21 vessel debris effects. The subcommittee will hear 22 presentations by and hold discussions with the NRC 23 staff and other interested persons regarding this 24 matter.
25 This subject was first reviewed in our NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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4 1 April 2019 subcommittee meeting, and this meeting is 2 a follow-up for additional information. The rules for 3 participation in all ACRS meetings, including today's, 4 were announced in the Federal Register on June 13th, 5 2019.
6 The ACRS section of the U.S. NRC public 7 website provides our charter, bylaws, agendas, letter 8 reports, and full transcripts of all our full and 9 subcommittee meetings, including slides presented at 10 such meetings. The meeting notice and agenda for this 11 meeting were posted there, and we've received no 12 written statements or requests to make an oral 13 statement from the public.
14 Today's meeting is open to public 15 attendance. If necessary, part of the meeting will be 16 closed in order to discuss information that is 17 proprietary, pursuant to 5 U.S.C. 552b(c)(4).
18 Attendance at all portions of the meeting that deal 19 with such information will be limited to the NRC staff 20 and those individuals and organizations who have 21 entered in to an appropriate confidentiality 22 agreement.
23 Consequently, we'll need to confirm that we have 24 only eligible observers and participants in the room 25 for any closed portion of the meeting, if we decide to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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5 1 close it. During this meeting, our subcommittee will 2 gather information, analyze relevant issues and facts, 3 and formulate proposed positions and actions as 4 appropriate for deliberation by the full committee.
5 The rules for participation in today's 6 meeting were included in the June 13th, 2019 notice 7 published in the Federal Register, and a transcript of 8 the meeting is being kept and will be made available, 9 as stated in that Federal Register notice.
10 Therefore, we request that participants in 11 this meeting use the microphones located throughout 12 the room when addressing the subcommittee, and the 13 participants should first identify themselves and 14 speak with sufficient clarity and volume so that they 15 may be readily heard. And we'll now proceed with the 16 meeting, and I'd like to start by calling upon the NRR 17 staff.
18 MS. MARSHALL: Thank you, Chairman. Good 19 morning. My name is Jane Marshall, I'm the acting 20 director of the Division of Safety Systems, and we're 21 here to present the final staff technical evaluation 22 report on the safety significance of in-vessel 23 downstream effects in operating PWRs.
24 As you noted, this is a follow-up to the 25 April meeting where we presented the draft TER, and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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6 1 the subcommittee asked staff to return when the TER 2 was final, so that's our meeting here today. At that 3 meeting in April, the subcommittee members also made 4 some comments and asked questions about the TER, and 5 we appreciate the feedback and will discuss the 6 changes that we made to the TER in response to some of 7 those questions today.
8 The staff does not expect a letter from 9 ACRS on this TER. We also would like to note that 10 this topic is an indication of the way that the staff 11 is being asked to transform and use more risk-informed 12 approaches to regulation. So it may seem a little bit 13 different than some of the things we've done, 14 historically. We appreciate your interest and your 15 feedback on this issue.
16 CHAIR REMPE: And just to be clear, you've 17 not asked for a letter on this, right? And you don't 18 expect to have any sort of letter from us as you 19 continue to go through and evaluate each plant's 20 compliance --
21 MS. MARSHALL: Correct.
22 CHAIR REMPE: -- with it?
23 MS. MARSHALL: Correct.
24 CHAIR REMPE: Okay.
25 MS. MARSHALL: We do not expect.
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7 1 CHAIR REMPE: Okay. Thank you.
2 MS. MARSHALL: Thanks.
3 MEMBER CORRADINI: Can I get something 4 clear? In the executive summary, the final sentence 5 is, the staff is evaluating compliance in an effort to 6 separate from the TER. So, there is a slide in the 7 slide packet, is that final figure the one piece of 8 information on how compliance is to be met from a 9 logic standpoint?
10 MS. MARSHALL: I think that's probably the 11 only thing we have in there.
12 MEMBER CORRADINI: Okay. So we'll just 13 wait until then?
14 MS. MARSHALL: The flow chart?
15 MEMBER CORRADINI: Yes.
16 MS. MARSHALL: Yes.
17 MEMBER CORRADINI: The yes/no diamonds?
18 MS. MARSHALL: Yes.
19 MEMBER CORRADINI: Okay.
20 MS. MARSHALL: That's right.
21 CHAIR REMPE: So since we're kind of going 22 out of order and this is in the backup, I know you had 23 a meeting with the PWR owners group recently. How are 24 they receiving this guidance document and the 25 information in the technical report? Do they think it NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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8 1 provides a good pathway?
2 MS. MARSHALL: It does, and they seemed 3 very energized by it and very eager to move forward 4 and close out the issue, and they're moving forward 5 with this guidance. We've discussed it with them on 6 a couple of occasions.
7 CHAIR REMPE: Okay, good.
8 MS. MARSHALL: Yes.
9 CHAIR REMPE: Thank you. Go ahead.
10 MR. SMITH: All right, so we'll get 11 started. I'm Steve Smith, I'll be starting off the 12 presentation. This is just basically an informational 13 briefing. The other presenters are Ashley Smith and 14 Paul Klein. We do have one important member of the 15 team on the phone, Ben Parks. I just want to be sure, 16 Ben, can you hear us?
17 MEMBER CORRADINI: He might be muted.
18 MR. SMITH: Oh, he's muted?
19 CHAIR REMPE: So he can't talk?
20 MR. SMITH: The public --
21 CHAIR REMPE: Why don't you go ahead and 22 open it?
23 MR. MOORE: This is Scott Moore. The 24 public line is muted right now, so nobody on the 25 public line can respond.
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9 1 CHAIR REMPE: Let's go ahead and open it 2 and let him respond, just to make sure he's there and 3 then also, I'll give Pete and Matt a chance to speak 4 up. Okay?
5 MR. MOORE: Okay.
6 MR. SMITH: All right. Ben, can you speak 7 to us?
8 MR. PARKS: This is Ben, I can hear you.
9 MR. SMITH: All right, good, we can hear 10 you, too. Great. Thank you.
11 MR. RICCARDELLA: This is Pete. Why don't 12 you check and see if anybody else besides Matt and Ben 13 and I are on the public line, and if not, just leave 14 it open?
15 CHAIR REMPE: Is anyone else on the public 16 line, other than the three individuals?
17 MS. SMITH: It says there's nine. We're 18 getting an indication there are nine.
19 CHAIR REMPE: There are nine people, so I 20 think we are going to have to mute it, but we're going 21 to try and open it periodically for you guys, okay?
22 MR. RICCARDELLA: All right, thanks.
23 CHAIR REMPE: Okay.
24 MR. SMITH: All right, thanks for the help 25 with that. We also had input from other staff and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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10 1 NRR, particularly the MLR, DSS, and DRA, and of 2 course, research helped us out with the TRACE work 3 that you heard about before, and also with some work 4 in xLPR that we had talked about last time.
5 MEMBER CORRADINI: So let me ask the 6 question here, and you don't have to answer here, but 7 I'm looking -- I'm trying to understand the basis of 8 the low safety significance finding. Is it the RES 9 calculations that are sensitivities on the base? Is 10 it using the Westinghouse submittal in appropriate 11 engineering judgment calculations? What's the essence 12 of the technical basis for the finding?
13 MR. SMITH: Do you want to?
14 MR. KLEIN: I would say the essence is all 15 information compiled, including the WCAP that was 16 submitted, independent research work, plus the 17 combined experience and judgment of the staff that 18 have been working the issue for, you know, 10 to 15 19 years.
20 MEMBER CORRADINI: Okay, but it's not the 21 Westinghouse submittal, because you use some numbers 22 from the submittal within a context, but as I see it, 23 you're talking through a story. And once you talk 24 through the story, you do some sensitivities, and 25 given all of that, you feel good. So it's really the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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11 1 judgment of the staff given the pieces?
2 MR. KLEIN: I believe so. I think the 3 argument that we presented in April was that when you 4 look at the combined evidence, we don't believe that 5 you can block the core inlet, and although we didn't 6 write a CT evaluation on the WCAP, itself, we felt 7 very comfortable using that information as a defense 8 in depth argument that should the staff judgment be 9 wrong and you do block the core inlet, there are 10 alternative flow paths that could provide sufficient 11 cooling -- long-term cooling.
12 MEMBER CORRADINI: Thank you.
13 MR. SMITH: Specifically, I don't know if 14 you're asking about the risk values, the order of 15 magnitude values. Those are all calculated just based 16 on break frequency and certain pipe break sizes.
17 MEMBER CORRADINI: I was going to get back 18 to that, but I was trying to get a bigger picture 19 about -- microphone, please? Sorry, excuse me, I 20 apologize. I was trying to get a bigger picture of, 21 is it the totality of everything, or if there are 22 individual pieces you sit on. So it sounds like it's 23 the totality of all the pieces with a judgment call 24 from the staff?
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12 1 purely based on break frequency. Everything else is 2 integrated decision making.
3 MEMBER CORRADINI: Okay.
4 MR. SMITH: Yes.
5 MEMBER CORRADINI: Thank you.
6 MR. SMITH: So we can move to slide two, 7 and I just want to express our appreciation for our 8 continued interactions on this, and the input you've 9 given us, I think, has definitely improved our 10 product, in this case and in other cases.
11 The TER, when we came to you, it seemed 12 like there was a lot of lack of clarity. People 13 didn't really understand it. So we revised it based 14 on ACRS member and peer review comments to make it 15 more readable, and to clarify its intent, and to 16 clarify the information that was used and the extent 17 of each information source that was used.
18 And also to try to clarify the logic used 19 by the staff to reach the conclusions. We don't have 20 a lot of time. I guess we might have more time than 21 I thought we had, but we're not going to try to repeat 22 too many of the details that we went through last 23 time. And the first nine slides are just kind of 24 background on what we talked about before.
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13 1 that were made as response to some of the questions, 2 and peer review, and ACRS member comments that came 3 up. And if you have any questions, it appears that 4 you will feel free to ask them at any time.
5 MEMBER CORRADINI: I'm sorry, I'm just 6 asking all sorts of starting questions. Is this going 7 to be -- let me put it in a historical context. So 8 when I first started, which was a while ago, this was 9 talked about, literally the same topic. So I assume 10 the commission has been briefed on this, or they will 11 be briefed, so they understand the context of this?
12 The reason I'm asking the question such as 13 that is, it's a story, and I'm still struggling in the 14 current TER to see how the pieces of the story fit 15 together, whether it be a graphic, a walk through.
16 The closest thing is why I asked the question about 17 slide 22, because in some sense, your thinking about 18 compliance actually leads to some sort of logic thing.
19 MR. SMITH: Right.
20 MEMBER CORRADINI: So is this going to be 21 presented to the commission, or does it stop at the 22 NRR director?
23 MR. SMITH: From a high level, we brief 24 the commission every six months, the commission TAs, 25 on --
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14 1 MEMBER CORRADINI: Okay.
2 MR. SMITH: -- our path forward, and in 3 our last meeting, we did discuss with them what we're 4 doing with the TER, and they're comfortable at a high 5 level. Not in the amount of detail that we've gone 6 into with you, but they were comfortable with what we 7 did, and they didn't ask a lot of pointed questions at 8 the time.
9 MEMBER CORRADINI: Okay, fine. Thank you.
10 MR. SMITH: All right. So we're going to 11 move on to slide three. This is just a recap of what 12 we talked about in April. In that meeting, we talked 13 about actions that were taken by NRC and industry to 14 address the effects of debris over the last several --
15 many years.
16 We provided discussion of our TER, and we 17 took feedback from the ACRS members to help us make 18 improvements with the TER. On slide four, the first 19 bullet, we discussed this a little bit in April. The 20 NRR goal is to align NRC and industry resources with 21 the safety significance of issues.
22 The TER was an attempt to evaluate the 23 overall safety significance of in-vessel downstream 24 effects, and we took into account a lot of new 25 knowledge that we've gained over the past couple of NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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15 1 years, and a lot of knowledge that's been around for 2 quite a long time.
3 And the one thing that we think is 4 important, and we'll have another slide on this, 5 defense in depth is maintained even if the core inlet 6 becomes blocked.
7 CHAIR REMPE: Just, again, to help me make 8 sure I understand, TRACE doesn't ever predict 9 blockage. You've just assumed blockage?
10 MR. SMITH: That's correct.
11 CHAIR REMPE: Okay.
12 MR. SMITH: TRACE assumed, you know, 13 various amounts of blockage, starting at a relatively 14 high amount, and then actually blocking the core and 15 let off completely.
16 CHAIR REMPE: But that's a user defined 17 input to do that?
18 MR. SMITH: Yes.
19 CHAIR REMPE: Okay.
20 MR. SMITH: Yes. I don't think it would 21 be -- I don't think we have the modeling capabilities 22 CHAIR REMPE: That's what I thought, but 23 I just wanted to make sure, because sometimes in the 24 TER, I got a little confused. So thanks.
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16 1 debris is going to go where in the core, and when it's 2 going to block, you know, that would -- that's 3 something that's probably beyond our ability.
4 CHAIR REMPE: That's what I thought.
5 Thanks.
6 MR. SMITH: Okay. Slide five, this slide 7 provides just a scope of what the TER evaluation was, 8 and as Jane talked about, it was atypical for really, 9 two reasons. Instead of using deterministic methods, 10 which is what we're used to using when we talked about 11 5046, we used integrated decision making.
12 And we also divorced the consideration of 13 compliance from the safety significance determination.
14 And I think that the TER was confusing. It may still 15 be confusing because of such a change in the way that 16 we do things and the way we think about things. But 17 since the TER came out, GSI-191, the GSI was closed, 18 and there has been a lot of confusion, both inside and 19 outside the NRC.
20 The GSI was closed basically because it 21 was determined that the important technical issues 22 associated with it were well enough understood that we 23 didn't really need to study them anymore, and it fell 24 out of the GSI program. The GSI program said, okay, 25 you can exit, you can take this out of the GSI NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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17 1 program.
2 Some people think that because the GSI was 3 closed that there's no further action needed on this 4 issue, and that's not what the case is. There's 21 5 plants that have closed the issue. They don't have to 6 take any more action. But the rest of the PWRs have 7 to close the generic letter 0402 by providing specific 8 responses to the NRC.
9 Actually, they don't have to, but that's 10 what we've requested them to do, a generic letter.
11 You know, we've just asked them to provide us 12 information. They don't have to if they don't want 13 to, but they're doing that. We're working to develop 14 guidance, which we talked about a little bit earlier, 15 on how they can respond to the in-vessel part.
16 The strainer part of the issue, nothing 17 has changed. They still have to treat the strainers 18 the same as they've always been treated in the past.
19 We have existing guidance that's been accepted for a 20 long time, and that's what they're using to address 21 the strainers. And then once these plants provide the 22 information, then we'll close them out on a plant 23 specific basis, one by one.
24 MEMBER CORRADINI: So let me ask about the 25 second bullet. Is there a document or a process that NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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18 1 one follows for integrated decision making? In other 2 words, if I go to Reg Guide XYZ, there is a process 3 flow? Or is this a new thing within the staff to try 4 this approach?
5 MR. SMITH: This is new. We did use a lot 6 of guidance out of Reg Guide 1.174.
7 MEMBER CORRADINI: Okay.
8 MR. SMITH: That's kind of the way we 9 thought about this, using defense in depth safety 10 margins, thinking about those sort of things.
11 MEMBER CORRADINI: Because I'm not against 12 it. I like the fact that you actually don't use 13 numbers only, but you actually have judgment. I just 14 was looking for some connection, because in section 15 whatever it is, you go through a series of steps, and 16 I'm trying to decide were those steps predetermined, 17 or did you organize these thoughts because of this 18 issue?
19 MR. SMITH: I guess we would have to see 20 what you're talking about, but I think we're doing a 21 lot of new kind of thinking when we did this.
22 MEMBER CORRADINI: Okay. Well, the reason 23 I'm saying that is not that I disagree with it, more 24 the fact that it would be good to then document the 25 fact that you've developed a process of thinking about NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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19 1 this that might be useable in other venues, where 2 something has, pardon the word, lingered, and --
3 MR. SMITH: We did think about that, and 4 I think that we and higher levels of management 5 understand that we need to get our processes caught up 6 with the way we're trying to do things.
7 MEMBER CORRADINI: Okay.
8 MR. SMITH: And I think there's other 9 people who are doing that at more generic of a level.
10 MEMBER CORRADINI: Thank you.
11 CHAIR REMPE: Okay. At this time, let's 12 just stop for a second and get the line open. Thank 13 you for the reminder. Is it open? Okay, can everyone 14 but Pete and Matt put your phone on mute? And Pete or 15 Matt, can you both chime in and say, do you have a 16 question, and say what it is if you do?
17 MEMBER SUNSERI: This is Matt, I don't 18 have any questions.
19 CHAIR REMPE: Thank you. Pete?
20 MEMBER RICCARDELLA: This is Pete. I 21 don't have any questions, either.
22 CHAIR REMPE: Okay. Please, everybody, 23 let's mute it again. Okay, go ahead.
24 MR. SMITH: All right, we're going to move 25 along to slide six, and this is a slide that NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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20 1 highlights the primary reasons why the ECCS design 2 flow path won't be blocked. So the core inlet's not 3 going to become blocked at the following LOCA.
4 This was discussed in more detail in 5 April, and I'll just go through. We think that the 6 uniform bed formation is unlikely. There's very few 7 breaks that generate enough debris to cause a core 8 blockage. Long-term core cooling has been shown using 9 TH analyses, long-term core cooling is maintained with 10 a high level of blockage at the core inlet.
11 And then, we have some testing that shows 12 that if you don't have chemical precipitants, you can 13 incur a lot of fiber and particulate loading at the 14 fuel inlets without blocking the core and still being 15 able to get enough flow through. And then there's 16 other things that are done, like switch over for most 17 of the plants.
18 Some of the plants, like the BNW plants, 19 do a little bit different. BAT mitigation strategies, 20 and those are -- those have been well established in 21 there in all the plants' emergency operating 22 procedures that would bypass that BAT that would --
23 could occur at the core inlet.
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21 1 that are putting in chromium coated, accident tolerant 2 fuel or other types of accident tolerant fuel with 3 coatings that may not be qualified from testing 4 previously?
5 MR. SMITH: Right. So we didn't do 6 anything about that. I think that a plant who does 7 something like that would have to evaluate it using 8 the 5059 process when they do install those kind of 9 fuel assemblies in the core.
10 CHAIR REMPE: But not for a lead test 11 assembly, I guess, because that's already being 12 approved? So it'll be when they try to do a core 13 loading, that will need to be documented that they 14 need to consider this somewhere?
15 And it would be in -- what's going on with 16 the accident tolerant fuel people, the staff, not you 17 guys with this -- it would fall under the statement 18 about unqualified coatings and you look for --
19 MR. KLEIN: Well, ultimately, the plant's 20 responsible, if they make a change in the plant, to 21 evaluate the potential impact. So I think they will 22 have programs that are designed to consider blockages, 23 a strainer blockage of the core inlet, and any change 24 to the plant, our expectation would be that it's 25 evaluated in terms of those two issues.
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22 1 CHAIR REMPE: Okay.
2 MS. MARSHALL: If I may, Chairman, this is 3 Jane Marshall, that phenomenon was considered in the 4 first panel, the coating, and what would happen with 5 the coating. And for the lead test assemblies, given 6 the small number of lead test assemblies, there's not 7 that much material.
8 CHAIR REMPE: So it'll come in when you 9 start doing the core loading? Okay.
10 MS. MARSHALL: Yes. And that was 11 considered, and it has been valid.
12 CHAIR REMPE: Okay.
13 MEMBER CORRADINI: But there will be 14 testing required by the proposers to show there's no 15 flaking?
16 MR. SMITH: Right.
17 MS. MARSHALL: Right, and adhesion is one 18 of the phenomenon, yes --
19 MEMBER CORRADINI: Okay.
20 MS. MARSHALL: -- and they are testing.
21 MEMBER CORRADINI: Thank you.
22 MR. SMITH: All right, on slide seven, 23 this is a slide that we saw in April, but we thought 24 it was an important concept, and we feel that the 25 defense in depth that is available is significant for NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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23 1 this issue.
2 On the left side in the red, when you hit 3 the red left side of the thing there, that means that 4 our assumption that the core is not going to become 5 blocked is wrong, okay? So from thereon out, we need 6 defense in depth. We didn't credit the alternate flow 7 paths from the WCAP in our evaluation of whether the 8 core would become blocked or not, but we did believe 9 that the alternate flow paths would provide a good 10 means to get coolant into the core.
11 The next three columns are just operator 12 actions that can be taken if the core inlet was to 13 become blocked, and then the last column talks about 14 containment integrity. The strainer evaluation is 15 separate from the in-vessel evaluation and the 16 deterministic strainer evaluations, and the staff's 17 opinion show that the strainers will function under 18 all design basis accident conditions.
19 So we expect that they would still 20 function to allow containment spray to function, and 21 you would still have your containment function -- your 22 containment cooling function intact. And this is the 23 end of my presentation. Ashley's going to take over 24 with the next slide.
25 MS. MARSHALL: Chairman, that might be a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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24 1 good point.
2 CHAIR REMPE: Okay. Actually, before I 3 open up the line, or while you're opening up the line, 4 didn't you used to have this defense in -- my notes 5 indicated you used to have this defense in depth 6 discussion in the executive summary, but in the most 7 recent version, I didn't find it. Is there a reason 8 that that was -- or did I just miss it, my notes 9 aren't correct?
10 MR. SMITH: We did change the executive 11 summary quite a bit, and I don't remember the reason 12 that we would've taken defense in depth out of there.
13 CHAIR REMPE: Okay. I just was curious.
14 Anyways, I think the lines are open. Pete, Matt, do 15 you have any questions?
16 MR. RICCARDELLA: No questions here. This 17 is Pete.
18 CHAIR REMPE: Not hearing anything from 19 Matt, we'll close the line and move on here. Okay?
20 MEMBER CORRADINI: So, let me ask a couple 21 questions at this point, before we go to the TRACE 22 analysis.
23 CHAIR REMPE: Thank you. Go ahead.
24 MEMBER CORRADINI: Okay. So here's where 25 I'm looking for some sort of story board that takes me NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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25 1 through the physical events with some sort of timing, 2 and you don't have to do it, but if I were not 3 embedded in this for a dozen years, I don't think I'd 4 follow this stuff.
5 So, that's why I go back to the final 6 slide. The way you talk through this picture, it's 7 fine, but I think you've got to have something that 8 actually talks through the accident. You've got three 9 different -- approximately three different plant 10 configurations, cold leg, hot leg, and then UPI, and 11 then you've got different plans on how they might 12 quantitatively change.
13 This strikes me that you want to go 14 through that in some sort of fashion, otherwise, I 15 would not understand if I was somebody that -- let me 16 put it in a different way. If I didn't believe that 17 the staff had thought this through, I'd challenge this 18 until I saw some sort of logical talking through the 19 points that, on a conservative basis, you still are 20 okay, because as you said here, if the core is 21 blocked, because I have a series of steps that occur, 22 I then have alternative defenses.
23 But I still don't see that initial talking 24 through, relative be to the time to block, the time to 25 switch -- or, sorry the time for switchover, the time NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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26 1 for blockage, the time for, then I want to call hot 2 leg switchover, the time for chemical precipitation, 3 which in some sense, you have assumed times that are 4 on the early end of each of those to give you margin.
5 And yet, I kind of have to still dig. It 6 seems like a picture, a talking picture along with 7 this sort of story board would be very helpful to the 8 general public understanding the reason why you have 9 so much margin. Because I think there is margin, it's 10 just hard to extract it from the TER.
11 MR. SMITH: I can understand that. I 12 think maybe the people who worked on it have been 13 working on it so long, it maybe is more apparent to us 14 what we were doing.
15 MEMBER CORRADINI: I'm kind of surprised 16 the commission staff doesn't ask you to explain it in 17 simple form.
18 MR. SMITH: I guess we could consider 19 doing that. I guess we'll have to talk about --
20 MEMBER CORRADINI: All right, and I'm not 21 trying to add work to what you have. If everybody 22 understands it within the staff, that's fine, but I'm 23 thinking about not the staff, but the general public 24 understanding the decision relative to the reasons 25 that there is significant margin at each stage of the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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27 1 process. If you see where I'm going with this.
2 MR. SMITH: Yes, I think in the last 3 meeting we did go through the scenarios for the 4 various types of plants, but probably didn't explain, 5 you know, in detail how the margins apply to each one 6 of those --
7 MEMBER CORRADINI: Okay.
8 MR. SMITH: -- types of plants.
9 MEMBER CORRADINI: Okay, fine.
10 MR. KLEIN: I think one of the biggest 11 things, and maybe we didn't communicate it well in the 12 TER, but it's clear that the first WCAP owners group 13 program that just assumed precipitate for them, and 14 then they tried to use bounding parameters in order to 15 run the tests.
16 When they went to the WCAP 17788 and did 17 the actual tests in the enclave and followed the time 18 dependent temperature profiles, it became clear from 19 the results that chemical effects for, except maybe 20 one or two plants, would come well after the point 21 where a bed would get disrupted at the core inlet.
22 And I think that was one of the big 23 changes in the owners group program that we saw, and 24 it gave us confidence that -- but it sounds like we 25 could've communicated that whole timeline better in NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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28 1 the TER.
2 MEMBER CORRADINI: Okay, thank you.
3 MS. SMITH: Okay, we're on slide eight, 4 for those following along. So various sensitivity 5 studies were completed by the Office of Regulatory 6 Research to support the conclusions in our TER. Some 7 were completed prior to the TER effort, and some were 8 to support the TER effort, and we presented specific 9 details of all those analyses in our April meeting.
10 Overall, we wanted to highlight a couple 11 of the conclusions we had that boric acid 12 precipitation was not found to inhibit long-term core 13 cooling, and ultimate flow paths are a viable option 14 to maintain long-term cooling -- long-term core 15 cooling for both cold and hot leg breaks.
16 CHAIR REMPE: So during our discussion at 17 the prior meeting, there was a table given to us where 18 you had comments from industry as well as the staff, 19 and the staff apparently had some concerns about the 20 applicability of TRACE for these analyses. And I know 21 you've modified the TER to talk more about the 22 applicability of TRACE, but I guess it wasn't obvious 23 to me still, what were the models this particular 24 staffer or staffers were concerned about, and how did 25 you address it?
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29 1 Because again, I asked the question at the 2 prior meeting, it was like, well, this came from the 3 staff and we're addressing it, but I wasn't sure what 4 the concern was and where the staffer was concerned 5 about it.
6 MS. SMITH: What I remember is the concern 7 was how we were relying more on TRACE than maybe the 8 industry was, and we made it more clear in the TER 9 that we were using TRACE to support our conclusions 10 and not necessarily saying TRACE shows the conclusion.
11 CHAIR REMPE: Okay, so they didn't have 12 concerns about the models just not being applicable 13 for particular phenomenon? Because that's kind of how 14 the comment read, and so --
15 MS. SMITH: That wasn't my understanding.
16 CHAIR REMPE: -- okay, so maybe I 17 misunderstood what was written in the table. Okay, 18 thank you.
19 MEMBER CORRADINI: Let me ask the 20 question, maybe you're going to get to it later. So, 21 how was the TRACE scenario developed so that -- is it 22 a best estimate? Is it a bounding? Or is it just 23 something to look at? Because there are certain 24 timings it's assumed relative to switchover, to 25 ramping up to complete blockage, to where the blockage NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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30 1 is, to et cetera, et cetera, et cetera. So how does 2 one characterize the TRACE calculation?
3 MS. SMITH: We had the idea to do the 4 TRACE calculation as a sensitivity study, so we tried 5 to use a lot of the same inputs that we had from 6 industry codes. I don't know if Steve wanted to chime 7 in on any of that, but that -- we had the same inputs 8 as far as timing, some switchover, the things that you 9 had mentioned, so that we could show that our results 10 were -- we could compare to what the industry had.
11 MR. BAJOREK: This is Steve Bajorek, 12 Office of Research. I characterize the TRACE 13 calculations as being more bounding. One of the first 14 things we did, I think in consultation with the owners 15 group, is we picked out a plant class that we thought 16 would be conservative with respect to the alternate 17 flow paths.
18 We picked the Westinghouse plant that had 19 originally been down-flow converted to up-flow, so you 20 didn't have communication from the barrel baffle 21 region to the core. This would be something that 22 would tend to starve the core. We picked areas, flow 23 areas, and these are something that you can change in 24 a user-defined function.
25 That gave us a way of bounding the K over NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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31 1 A squared, the net resistance to the bottom of the 2 core, in order to be more conservative than what we 3 thought industry should be. Now, for decay heat, we 4 were -- best estimate, we used 79 decay heat, but we 5 also did sensitivities to go back to a 73 decay heat 6 to show what would happen if we were to add more power 7 in the reactor.
8 And actually, with respect to boric acid 9 precipitation, the higher power actually helps you.
10 It increases the entrainment and helps you to, you 11 know, flush out the core for a longer period of time.
12 But other than that, these calculations were well on 13 the conservative time.
14 And when we started this, I think that the 15 time at which we initiated blockage of the core was 16 conservative with respect to what we thought it was 17 going to be. The ramp up time about consistent with 18 what it would.
19 CHAIR REMPE: So I want to understand what 20 you said. First of all, this entrainment phenomena 21 with the decay heat effects, is that validated 22 anywhere, or is it just, oh, this is common sense, but 23 you didn't notice it until you saw it in TRACE?
24 MR. BAJOREK: Well, no, I mean, TRACE has 25 been validated for large and small break, and at NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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32 1 entrainment carryover, very important for us.
2 CHAIR REMPE: Okay.
3 MR. BAJOREK: Okay, so we've used tests 4 like FLECHT, FLECHT-SEASET, RBHT, in order to show 5 that our entrainment models are approximately correct 6 for carrying over, and --
7 CHAIR REMPE: But it's not the boric acid, 8 per se, it's just the --
9 MR. BAJOREK: I'm not aware of any test 10 where you --
11 CHAIR REMPE: Right.
12 MR. BAJOREK: -- orated things to try to 13 do that, but one of the things that we did before we 14 did the TRACE calculations is, we updated our 15 thermophysical properties so that when you got high 16 concentrations of boric acid, it was appropriately 17 reflected in the fluid density, which can increase 18 about 10 percent greater than pure water. And the 19 viscosity, which is approximately 30 percent greater 20 once you get to the precipitation of it.
21 CHAIR REMPE: Okay.
22 MEMBER CORRADINI: Let me just make sure 23 I understand. So I'm not sure I should mention 24 numbers, but there's a number assumed in the TRACE 25 calculation for switchover from clean water to recirc NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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33 1 out of the sum. Then, there's another ramp up time 2 from the K-loss being normal to the K-loss being 3 essentially infinite over some other time window.
4 How are those determined? Because I don't 5 know how one gets those numbers, so I'm trying to 6 understand -- I mean, they might be conservative, I'm 7 just trying to understand where'd they come from?
8 MR. SMITH: I think the time at which the 9 resistance started ramping up was around 20 minutes, 10 which is when most plants would -- that's the earliest 11 time for most plants to switch over. So that's the 12 conservative time, and then the value used, I think it 13 was -- I forget how many seconds it was to ramp 14 from --
15 MEMBER CORRADINI: I'm not sure I can say 16 it, but it was --
17 MR. SMITH: -- zero to --
18 MEMBER CORRADINI: -- longer.
19 MR. SMITH: -- you can say that. So that 20 was just something that we thought was a reasonable 21 time to get the debris out of the pool and either 22 collect it on the strainer or in the --
23 MR. BAJOREK: This is Steve Bajorek again.
24 We did vary that. We looked at what we thought would 25 be a best estimate time for the ramp up, and we also NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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34 1 did calculations where we made it much, much shorter 2 than what it was going to be, and it didn't really 3 affect things that much.
4 MEMBER CORRADINI: Okay.
5 MR. BAJOREK: We also looked at the hot 6 leg switchover time. I went to the extreme, and he 7 said what happens if it doesn't occur, ran the 8 calculations out for I think it was something like 36 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> that basically showed that by the time you --
10 your real concern is keeping the core covered, okay?
11 By the time you precipitate, you would be 12 uncovering the core. That would be more of your 13 concern. So even within the absence of hot leg 14 switchover, you have lots of time and lots of time 15 relative to typical assumptions from when hot leg 16 switchover's going to occur.
17 MEMBER CORRADINI: Okay. And then to kind 18 of get back to Joy's question, TRACE can track 19 concentration of boron in the water, and that's about 20 as far as it goes. You essentially then look, if you 21 get close to the precipitation point, but you don't 22 model precipitation, nor do you model the debris.
23 MR. BAJOREK: We don't model the debris, 24 okay? When you get to the precipitation limit, TRACE 25 will take the excess boric acid and play it out on a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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35 1 structure.
2 MEMBER CORRADINI: Okay.
3 MR. BAJOREK: And we saw that in the 4 calculations when you dried out -- like, in the upper 5 head, TRACE would say, hey, you're going to deposit a 6 film of boric acid. Now, if you recovered that region 7 with water, it would just go back into solution.
8 So as you get up to precipitation, TRACE 9 is not getting the dynamics correct, at that point.
10 It's just telling you that hey, this is the point in 11 time when precipitation is likely to occur.
12 MEMBER CORRADINI: Okay. So I have a 13 couple more questions. So you arbitrarily increase 14 the K-loss such that it looks like it was blocking, 15 and then at something like -- and I can't remember, in 16 the document somewhere, it's something around, as I 17 think one of the slides said, 99 percent -- you're 18 still okay.
19 Is there a physical reason why it doesn't 20 go to 100 percent? Because there used to be a member 21 here that always believed it would go to 100 percent 22 like a felt hat (phonetic).
23 MR. BAJOREK: Well --
24 MEMBER CORRADINI: You know what I'm 25 getting at.
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36 1 MR. BAJOREK: -- some sensitivities, that 2 was just a sensitivity that was done. Actually, some 3 increased the blockage to 100 percent. I don't 4 remember that --
5 MEMBER CORRADINI: But then you have to 6 rely on alternative flow paths?
7 MR. BAJOREK: That's right.
8 MEMBER CORRADINI: Okay. What I guess I'm 9 getting at is, so that was your -- that was how you 10 essentially evaluated margin was essentially take it 11 as a series of parametric steps, then assume 100 12 percent, and then show that alternative flow paths 13 would provide you enough?
14 MR. BAJOREK: That's correct.
15 MEMBER CORRADINI: Okay. And the reason 16 the alternative flow paths don't clog?
17 MR. BAJOREK: Because they're too large.
18 MEMBER CORRADINI: So are we allowed to 19 say what's large and what's not large? Is there a 20 boundary between large and not large?
21 MR. BAJOREK: The --
22 MEMBER CORRADINI: We can go to closed 23 session, if you want.
24 MR. BAJOREK: Yes, I don't know if we can 25 say this on --
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37 1 MEMBER CORRADINI: That's fine.
2 CHAIR REMPE: Okay.
3 MEMBER CORRADINI: That's fine. That's 4 fine.
5 MS. SMITH: It's based on testing.
6 MR. BAJOREK: It's based on testing.
7 MEMBER CORRADINI: So it's actually --
8 there was testing where there was -- there were 9 certain gaps --
10 MR. BAJOREK: Yes.
11 MEMBER CORRADINI: -- and then as the gaps 12 grew, there was no way to block them?
13 MR. BAJOREK: Right, and as we reviewed --
14 as we did a review of the WCAP, we actually came back 15 and said, hey, we don't think you should be crediting 16 some of these, and they took them out of the 17 calculations.
18 MEMBER CORRADINI: I see. Okay.
19 MS. SMITH: We asked do you have testing 20 to show this opening size would be a viable option for 21 debris to pass through? And they said we don't have 22 testing to sort of show that, so we'll take it out, 23 and they revised their conclusions.
24 MEMBER CORRADINI: Okay.
25 MR. KLEIN: I think another point to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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38 1 mention, too, is that the amount of fiber per time 2 continues to decrease dramatically. So as you get to 3 a point where the core inlet may become more blocked, 4 you also have a strainer that's being covered and 5 allowing much less fiber to pass through it.
6 MEMBER CORRADINI: Okay. Okay, thank you.
7 MS. SMITH: All right, and then next, on 8 slide nine, this is just a reminder from our April 9 meeting that the staff conclusion in the TER is that 10 in-vessel downstream effects are of low safety 11 significance, based on our current state -- based on 12 our current knowledge state.
13 All right, next slide. All right, so this 14 is really the new information that we're presenting 15 the next few slides. They're items that we wanted to 16 highlight based on comments from ACRS members at the 17 April meeting, as well as peer review and Peter 18 Barrano's (phonetic) comments. The first item here is 19 the definition of safety significance criteria.
20 We added this chart that's from the side 21 into the TER as a revision based on ACRS member 22 comments. Instead of using risk values from just Reg 23 Guide 1.174 and new Reg 0058, we looked at a variety 24 of NRC programs to ensure the definition of risk we 25 were using to define safety significance within the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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39 1 bounds of our available guidance.
2 And you can see as indicated at the arrow 3 at the bottom, the staff determined the order of 4 magnitude of the occurrence frequency that can 5 challenge on control flowing would be 1 times 10 to 6 the -6 per year or less.
7 MEMBER CORRADINI: So help me out. I know 8 the last one, since one of our members has been 9 educating us about 0058, and I know the first one.
10 What are the two in the middle?
11 MR. SMITH: The significance determination 12 process, that's something the region gets into more 13 when they --
14 MEMBER CORRADINI: So this is at the 15 region level?
16 MR. SMITH: -- they look back at scenarios 17 that occurred at a plant, and they do a PRA, and they 18 use that. And then the other one is LIC-504, which 19 that's a -- one of the management directives that we 20 use to -- or one of the procedures we use to evaluate 21 this and similar kinds of occurrences.
22 MEMBER CORRADINI: So the blue arrow is 23 supposed to tell me what?
24 MS. SMITH: That's just where we ended our 25 evaluation. It's just a --
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40 1 MR. SMITH: That's the order of magnitude 2 or break frequency that we estimated would be -- could 3 cause adequate fiber to be generated to block the core 4 inlet.
5 MEMBER CORRADINI: And that corresponds to 6 the pipe size that you use in the table one --
7 MR. SMITH: Yes.
8 MEMBER CORRADINI: -- as a break point?
9 MR. SMITH: Yes.
10 MEMBER CORRADINI: Okay. All right, I 11 understand now. Thank you.
12 MS. SMITH: All right, next slide.
13 MEMBER CORRADINI: Do you want to ask the 14 folks out in the -- I'm assuming that Dr. Riccardella 15 cares about break size, so this might be a good chance 16 to see if he cares.
17 CHAIR REMPE: Can we open the line?
18 MEMBER CORRADINI: Because I don't know 19 break size -- yes.
20 CHAIR REMPE: Do you have any questions --
21 MEMBER RICCARDELLA: This is Pete --
22 CHAIR REMPE: -- do you have any 23 questions, Pete?
24 MEMBER RICCARDELLA: I do. Can you hear 25 me?
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41 1 CHAIR REMPE: Yes, we can.
2 MEMBER RICCARDELLA: Okay. So the blue 3 arrow, what break size are we talking about for that 4 blue arrow?
5 MR. KLEIN: All right, so the blue arrow, 6 it's not just for a single break size. It's for a hot 7 leg break, and the actual break size that we evaluated 8 was for a six-inch pipe, so it's a 5.19 inch break, 9 and that's for a hot leg break. And then the cold leg 10 break, we assumed anything smaller than 12 inches 11 would not generate adequate debris to cause a blockage 12 of the core inlet.
13 MEMBER RICCARDELLA: So anything smaller 14 than what?
15 MR. KLEIN: A 12-inch break.
16 MEMBER RICCARDELLA: Okay. And, you know, 17 another question I have is, the metric isn't actually 18 RISP or CDF, it's Delta CDF. Would you explain that, 19 please?
20 MR. KLEIN: Yes, so the Delta CDF, 21 basically, we assume that if the break occurred, it's 22 sort of a conditional --
23 MEMBER RICCARDELLA: Yes.
24 MR. KLEIN: -- we assume that if that 25 break occurs, that you would go to core damage. So NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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42 1 the Delta CDF is between a plant that could generate 2 enough debris at that size break, so a plant that 3 would have no potential debris effects.
4 MEMBER RICCARDELLA: No debris at all, 5 okay.
6 MR. KLEIN: Yes.
7 MEMBER RICCARDELLA: Okay. Got it. Thank 8 you. I'll be interested, Joy, in talking later when 9 we get into discussion of the risk analysis and later 10 slides.
11 CHAIR REMPE: Is this the xLPR slide, or 12 is it --
13 MEMBER RICCARDELLA: Yes.
14 CHAIR REMPE: -- okay. I'll try and 15 remember. And then Matt, do you have any questions?
16 MEMBER SUNSERI: I don't, but can you hear 17 me?
18 CHAIR REMPE: Yes, we can. Thank you.
19 MEMBER SUNSERI: Okay, thanks.
20 CHAIR REMPE: Go ahead.
21 MS. SMITH: Okay, we'll go to slide 11.
22 We already talked about this a little bit, but we had 23 comments about how TRACE was used to inform 24 conclusions in our TER. Edits were made in the 25 document like Joy had mentioned to clearly state what NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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43 1 TRACE is used for in the model. We're confident that 2 the results support our conclusions.
3 We also had details of the various 4 sensitivity studies added in a table. That was the 5 same table that we presented to ACRS in April, and 6 that showed the purpose of each study and more 7 descriptive things about each study. Okay, I'm going 8 to turn it over to Steve to talk about another thing 9 we wanted to highlight.
10 MR. SMITH: Okay, so one of the ACRS 11 members, or maybe more than one, requested that we do 12 a sensitivity on the fuel assembly fiber amount that 13 could be accommodated. They said, well, suppose you 14 couldn't use the WCAP 17788 numbers, which shall not 15 be named, and you used the 15 gram per fuel assembly 16 value from WCAP 16793, which is what we know is 17 conservative, and that included chemicals and all 18 that.
19 So, we went back and looked at the data 20 that we had from a high fiber plant in South Texas, 21 and we didn't really have enough data on how much 22 debris is generated from these break sizes. There was 23 the four-inch breaks, there was only one break that 24 generated enough debris to cause the 15 gram per fuel 25 assembly value to be exceeded.
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44 1 So there was actually one four-inch break 2 that -- four-inch pipe break which would be a little 3 bit smaller, 3 point -- I forget what the 3 point --
4 what the wall thickness is there. So there was one --
5 and the majority of the debris for those breaks comes 6 from latent debris. So latent debris kind of 7 dominates the term at these really low fiber levels.
8 Anyway, what we did instead -- so we 9 looked at it that way, and then we looked at it from 10 another perspective is that if the fiber penetration 11 value, we used a -- the most conservative for our 12 initial. We had a few sets of fiber penetration data 13 that we could use.
14 If we used the most conservative value, 15 15 percent, and we did exceed the 15 gram per fuel 16 assembly limit, and if we used the second most 17 conservative value from the fiber penetration testing, 18 which was 12 percent at that particular amount of 19 debris, it would be below -- you would end up below 20 the 15 grams per fuel assembly, even with the 6-inch 21 break.
22 So that's the couple different ways we 23 looked at it. We really didn't have enough data to do 24 a good sensitivity study on exactly what pipe size you 25 would have to reduce to. So we couldn't really NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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45 1 calculate a frequency. It's probably confusing.
2 MEMBER CORRADINI: Well, I was going to 3 ask you if you could repeat some of that, because I 4 don't get it. So what you did was to vary the pipe 5 size, and then with a particular plant, look at what 6 the fiber generation would be and then what was 7 captured on the sum screens versus what's passed 8 through?
9 MR. SMITH: That's correct.
10 MEMBER CORRADINI: Am I understanding this 11 correctly?
12 MR. SMITH: That's correct, and we only 13 had information from one plant, that was South Texas.
14 MEMBER CORRADINI: Right, because the 15 RoverD analysis that they did.
16 MR. SMITH: Yes.
17 MEMBER CORRADINI: But their approach to 18 this -- I'm not sure if we can say it. Their general 19 approach to it -- let me try it that way -- their 20 general approach to it was alternative flow paths 21 after a certain point, if I remember correctly. That 22 is, their RoverD approach to a deterministic in-vessel 23 debris evaluation was essentially alternative flow 24 paths got them past the point of concern.
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46 1 analysis, you're correct.
2 MEMBER CORRADINI: Okay. Okay. So --
3 MR. SMITH: They assumed that the core 4 inlet was blocked at a very early time.
5 MEMBER CORRADINI: Much earlier than --
6 MR. SMITH: Yes.
7 MEMBER CORRADINI: Okay. Okay. All 8 right, I think -- I don't remember who made this 9 comment, but I'm just trying to understand what you 10 did. Okay, so South Texas was, in some sense, a 11 calculational example?
12 MR. SMITH: That was the only place that 13 we had --
14 MEMBER CORRADINI: Enough information?
15 MR. SMITH: -- fiber generated per break 16 size, but they only did it for six-inch pipes and then 17 four-inch pipes, and two, you know? So between six 18 and four, we just didn't have enough data to come up 19 with some sort of a frequency, you know, a meaningful 20 frequency number.
21 MEMBER CORRADINI: Okay. All right, thank 22 you. Okay.
23 MR. SMITH: Okay, we'll move on to slide 24 13 and xLPR a little bit more about pipe break 25 frequency.
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47 1 MR. KLEIN: All right, I'll take this one.
2 So, during the April subcommittee meeting, we were 3 asked if the staff could use xLPR and try to benchmark 4 the new Reg 1829 break frequency that was assumed in 5 the staff TER.
6 So we had several members of the NRC staff 7 run the xLPR code investigate the effects of pipe 8 size, degradation mechanisms, how things like 9 mitigation of susceptible wells and leak detection 10 would affect some of the numbers, and we have some 11 preliminary results that suggest the local frequencies 12 in 1829 are conservative, but we consider those 13 preliminary.
14 And I think that the effort was useful in 15 terms of the lessons learned with the xLPR code, as 16 well. So there's additional studies that are in 17 progress, and we can take questions. We have the 18 right people in the audience to address detailed 19 questions.
20 CHAIR REMPE: So before I open the line 21 for Pete's detailed questions, what are you going to 22 do with these sensitivity study results? I mean, the 23 TER is done, you're issuing -- you've already issued 24 guidance to the owners groups. What are you going to 25 do with it?
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48 1 MR. KLEIN: I don't think that xLPR 2 results are going to affect the TER. Like you 3 mentioned, it's already issued and on the street, we 4 don't feel a need to modify it based on the xLPR work 5 that's been done to date.
6 CHAIR REMPE: Okay. Is the line open?
7 Pete? Okay.
8 MEMBER RICCARDELLA: This is Pete. Is 9 there openly going to be a report, or white paper, or 10 something prepared on this study?
11 MR. KLEIN: I'm going to ask Dave Rudland 12 to maybe step up to the mic and address that.
13 MEMBER RICCARDELLA: That would be great.
14 Hi, Dave, how are you doing?
15 MEMBER CORRADINI: So since you're doing 16 it -- since Pete asked about this one, I was going to 17 ask about the TRACE one, so we might as well just get 18 it all out on the table.
19 MR. RUDLAND: Hey, this is Dave Rudland, 20 Senior Technical Advisor for Materials and the 21 Division Materials License Renewal. Pete, right now, 22 I don't know. We don't really have any large plans.
23 We're kind of continuing this study to look at both 24 these effects and those questions that came out of the 25 new scale DCD review, also. I'm going to be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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49 1 presenting some of these results at our PFM workshop 2 at the end of October.
3 MEMBER RICCARDELLA: Oh, okay.
4 MR. RUDLAND: And we'll probably put 5 together some kind of report, but we haven't really 6 discussed what that would be at this particular time.
7 MEMBER RICCARDELLA: Okay, I wasn't aware 8 of that workshop. What's the date of that workshop?
9 MR. RUDLAND: It's the third week of 10 October. October 21 to 23, I believe. I don't have 11 my calendar with me.
12 MEMBER RICCARDELLA: Okay, a three-day 13 workshop.
14 MR. RUDLAND: Yes, it's a three-day 15 workshop, and held here in D.C.
16 MEMBER RICCARDELLA: At headquarters?
17 MR. RUDLAND: Yes, we're actually having 18 it at an off-site location, but in Rockville.
19 CHAIR REMPE: You can make a trip back the 20 third week of October, right Pete? It's a joke.
21 MEMBER RICCARDELLA: Yes, that's the week 22 we don't have subcommittee.
23 CHAIR REMPE: That's right, but you can 24 make the flight back. There was a question Matt had?
25 Matt, you got interrupted, did you --
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50 1 MEMBER SUNSERI: I have no questions, just 2 still following along. Thanks.
3 CHAIR REMPE: Okay.
4 MEMBER RICCARDELLA: Okay, thank you.
5 MEMBER CORRADINI: So can we pick up the 6 question about the TRACE sensitivities?
7 MS. SMITH: Yes, so the TRACE --
8 MEMBER CORRADINI: Is there going to be --
9 MS. SMITH: -- the TRACE sensitivities 10 were done as part of a user need that we had for the 11 boric acid precipitation studies, and then we just did 12 follow on studies to help us support conclusions in 13 the TER. Right now, there's no intention for a white 14 paper, but the report given to NRR, I have opposite 15 research for that user need I'm sure we could make 16 available if you're interested.
17 MEMBER CORRADINI: Okay.
18 MR. SMITH: It actually ought to be one of 19 the references in the paper.
20 MEMBER CORRADINI: There is a reference?
21 Did I miss it? I apologize.
22 MR. SMITH: It should be there. If it's 23 not, we probably messed up.
24 MEMBER CORRADINI: Okay. Well, to the 25 extent that it's available, I'd be interested.
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51 1 MR. SMITH: Okay.
2 MS. SMITH: Yes, we'll be sure to get it 3 to you, and I know it's in references. I don't know 4 offhand which number it is.
5 MEMBER CORRADINI: Well, I didn't look, so 6 --
7 MS. SMITH: Yes, we'll find out.
8 MEMBER CORRADINI: -- to be honest, I 9 didn't -- okay, thank you.
10 MS. SMITH: And provide it.
11 MR. SMITH: All right, we'll go to --
12 MEMBER RAY: Wait, I'm going to ask a 13 question. Are these studies of LOCA frequencies used 14 elsewhere, other than this work that we're talking 15 about today?
16 MR. KLEIN: The new Reg 1829 studies?
17 MEMBER RAY: Well, I guess. I'm really 18 talking about the reference to 1829, it says, are 19 conservative. I'm asking about the results that we're 20 talking about in this meeting, which are preliminary 21 results as it's described there on the third bullet.
22 Are they going to be used for anything else, other 23 than what -- GSI-191 related?
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52 1 characterized it as preliminary. So I think xLPR 2 still may need a few tweaks in order to optimize it 3 and the work that was done to do this evaluation is 4 helping that effort.
5 So I don't think the end goal with the 6 xLPR effort was really to have a grand result, but 7 it's more to look at the 1829 assumptions and say, 8 could the staff have erred on the LOCA frequencies?
9 And the preliminary results suggest that that's not 10 the case, that those frequencies are probably 11 conservative.
12 MEMBER RAY: Well, I'm thinking about risk 13 informing consideration of future plant designs, that 14 sort of thing. And I'm just wondering if these -- if 15 this work leads, ultimately, to some update or input 16 basis, whatever you want to say, that we may be using 17 and thinking about future plant designs.
18 MR. KLEIN: Dave, I'll defer to you for 19 long-term plans on xLPR.
20 MR. RUDLAND: Yes, this is Dave Rudland 21 again. The study we did was kind of focused here, 22 right? Just to kind of give us a feel for the 23 conservative nature of 1829, and in order to do the 24 job correctly, to really confirm all of the results 25 according to plan would be a much more expansive NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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53 1 effort. Now, I think it's a doable effort, but I just 2 think right now, we don't have the plans to expand it 3 all that far.
4 MEMBER RAY: Okay, well that really gets 5 to my point, is that this isn't something that once 6 done, it gets picked up and used elsewhere?
7 MR. RUDLAND: Yes, it would need to be 8 expanded much further if it were going to be used 9 generically.
10 MEMBER RAY: Thank you.
11 MEMBER RICCARDELLA: This is Pete, can you 12 guys still hear me?
13 MR. RUDLAND: Yes.
14 CHAIR REMPE: Yes.
15 MEMBER RICCARDELLA: I'd like to, you 16 know, at some point, I'd like to see almost a 17 statement. I was one of the co-authors, or one of the 18 experts on the new Reg 1829 extra panel, and I recall 19 we had tables of break sizes with kind of ranges of 20 frequencies for each size.
21 I just would like to see just from your 22 preliminary results what those -- how the xLPR ranges 23 compare. I mean, were they an order of magnitude?
24 You said they were conservative. Were they an order 25 of magnitude lower, a couple orders of magnitude?
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54 1 MR. RUDLAND: So this is --
2 MEMBER RICCARDELLA: Did the uncertainty 3 ranges overlap?
4 MR. RUDLAND: So this is Dave Rudland.
5 Pete, again, we didn't do an exhaustive enough search 6 to be able to really give ranges of uncertainty on the 7 failure frequencies. What we did was we did a 8 sampling of several different pipe sizes and 9 degradation mechanisms, from select cases from 1829, 10 just to look at that.
11 And again, you know, the numbers were 12 based on our assumptions of crack initiation 13 frequencies, and they turned out to be a couple of 14 order of magnitude below those that were in 1829. And 15 again, the details, I think, would be more -- the 16 details of the analyses and the results would be more 17 informative than just a table of frequencies.
18 MEMBER RICCARDELLA: Okay. And you said 19 that workshop is the week of the 23rd?
20 MR. RUDLAND: What I'll do, Pete, is I'll 21 take an action to send you the flier for the workshop.
22 MEMBER RICCARDELLA: Thank you, I 23 appreciate that. That's all I have.
24 CHAIR REMPE: Okay, thank you. Go ahead.
25 MR. KLEIN: All right, move to slide 14.
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55 1 Okay, I'll take this one, too. This is the final 2 slide in our regular scheduled program here. So, the 3 purpose of the TER, as we mentioned, was to evaluate 4 the CET significance of in-vessel downstream effects.
5 Based on the current knowledge base and 6 the TER, the NRC was able to close GSI-191, and Steve 7 explained the difference between closure of GSI-191 8 and licensee resolution, which will be addressed 9 separately as part of the generic letter process. I 10 think we're really, at this point, ready to address 11 any additional questions.
12 There's an ML number listed for the NRC 13 staff review guidance, and that review guidance is 14 intended to help the staff address licensee responses 15 as they're submitted to the NRC staff. And we have 16 tried to develop that guidance with both a number of 17 internal NRC staff and also external stakeholders.
18 And most of the core team that worked on 19 the TER was also involved in the staff guidance, and 20 we have a schematic, if you'd like us to put that up 21 and begin discussions on the staff guidance, if that 22 would be helpful.
23 CHAIR REMPE: I would like to see it.
24 This is slide 22, right? Have you discussed it? It's 25 in the guidance, which is publically available, so NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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56 1 let's go for it.
2 MR. KLEIN: So, I'll start this, Steven, 3 and maybe you, and Ashley, and Ben can jump in, but in 4 terms of just the philosophy of how to do review 5 guidance, I think the general staff philosophy was we 6 wanted to try to design a flow chart that would allow 7 the plant with the least challenges to work through 8 the process and maybe get the NRC staff closure in the 9 most direct manner.
10 So we tried to set it up so that those 11 plants with the most favorable attributes were able to 12 pursue one of the early passed resolution, maybe one, 13 two, or path three, which path one would include the 14 plants that were able to close out under a previous 15 WCAP because the staff understands what that amount of 16 fiber that it's just extremely difficult to block the 17 core inlet, including chemical effects.
18 And then paths two and three were designed 19 for plants that have very favorable attributes in 20 terms of alternate flow paths, or alternate ways to 21 get flow into the core. So we felt the plants that 22 were of the BNW plant design or upper plenum injection 23 plants, if they met the fiber limits that were within 24 WCAP 17788, that would lead to a direct closure path 25 for those type of plants.
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57 1 MEMBER CORRADINI: So let's just, if we 2 could, so take box one. So box one says, go find a 3 spectrum of break sizes that by 1829 are of high 4 enough frequency and show -- and therefore show that 5 you're less than 15 grams. If your answer is yes, 6 then you go to the right, if the answer's no, then you 7 go down and ask the next question?
8 MR. KLEIN: I think box one was intended 9 to be a deterministic path based on WCAP 16793. Since 10 the staff already had a CT evaluation written 11 independent of that --
12 MEMBER CORRADINI: The size of the hot leg 13 break. The worst break.
14 MR. KLEIN: Yes, worst break.
15 MEMBER CORRADINI: Excuse me, I 16 misunderstood. I assumed you already had started 17 chopping it with size. No?
18 MR. KLEIN: No consideration of size under 19 path one. It would be the bounding break, can you 20 meet that amount, and that would be the path that --
21 what we had turned to option one plants had taken to 22 reach closure.
23 MEMBER CORRADINI: Okay. I misunderstood.
24 MR. SMITH: So this is the reason why it 25 becomes confusing, because for all of these, because NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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58 1 this is more of a compliance thing than a safety 2 significance thing, these plants all have to evaluate 3 the worst possible break for how much fiber can get to 4 the core, including single failure and all that. So 5 all these fiber amounts that are calculated in here 6 are more of a compliance thing. 5046 says you've got 7 to calculate the worst scenarios.
8 MEMBER CORRADINI: Well, you've lost me 9 now. I thought I had you, but now --
10 MR. SMITH: Okay.
11 MEMBER CORRADINI: -- I'm --
12 MR. SMITH: Sorry.
13 MEMBER CORRADINI: -- I'm decoupling.
14 MR. SMITH: I should have not said 15 anything.
16 MEMBER CORRADINI: You could've just 17 nodded and just let me go on my merry confused way.
18 So box one is the largest break, not the largest break 19 given a frequency?
20 MR. SMITH: No, it's the largest break.
21 It's not necessarily the largest, but the biggest 22 debris -- the one that generates and transports the 23 most debris to the core.
24 MEMBER CORRADINI: Okay. Okay. All 25 right, so this is almost a filter before -- excuse the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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59 1 word, but it's a filter before you go through 2 everything we just discussed? I'm having trouble.
3 MS. SMITH: It's separate. I think you're 4 getting confused because the TER had frequency 5 evaluation in it. When we did the compliance added, 6 that was kind of separate.
7 MEMBER CORRADINI: Well, I'm concerned 8 about inconsistency if I go through a compliance set 9 of logic, I'm going to find myself in trouble, even 10 though by the TER, it's of low safety significance.
11 That's what's confusing, so help me.
12 MR. SMITH: Right. The TER, we wrote to 13 determine the safety significance of the issue. We 14 determined the safety significance of the issue was 15 low, especially if the plant showed that they met the 16 key parameters in the -- that we considered when we 17 looked at that.
18 So then, after that, that kind of guided 19 us into how we would develop our staff review 20 guidance. Since it's a low safety significance thing, 21 how much detail do we really have to look at? And so 22 this is where Paul said, you know, we have to look 23 harder at some plants, but every plant has to consider 24 not based on what their break frequency is, unless 25 they come in and get an exemption and do a risk NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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60 1 informed evaluation like STP did. Every plant has to 2 consider the largest amount of debris that could reach 3 the core under 5046 rules, basically.
4 MEMBER CORRADINI: Okay, all right. Do 5 you want to add to this?
6 MR. LEHNING: Yes, this is John Lehning 7 from the NRR staff, too, and I just wanted to say, 8 where the risk part comes in is potentially on the 9 bottom, the lowermost yellow box there, the plant 10 specific evaluation.
11 So that is still an option, but basically, 12 the rest of this flowchart is based on the compliance 13 part, and for some plants that are able to show 14 compliance that way without an exemption, that may be 15 the easiest thing.
16 But it's not to say that we're throwing 17 away the TER. That may still be a part of the basis 18 for some of the plants that may not be able to do it 19 for the whole spectrum.
20 MEMBER CORRADINI: So can I say what you 21 just said differently? That is, by compliance, you 22 assume 5046 rules all the way through, and you get to 23 the yellow box, and then you might be able to apply 24 the risk significance to let them off the hook?
25 MR. LEHNING: Yes.
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61 1 MEMBER CORRADINI: To put it bluntly.
2 MR. LEHNING: Yes. If they wanted to use 3 a risk informed argument, they would have to come in 4 with a LAR and an exemption.
5 MEMBER CORRADINI: Uh-huh, but they could 6 reference the risk -- excuse me, they could reference 7 the TER and that calculational logic to show they fit 8 within that box? That's what I'm still trying to --
9 MR. LEHNING: They could use a similar 10 kind of logic. I mean, it's a little bit more -- when 11 you do a plant specific calculation, we determine an 12 order of magnitude when we came up with that 10 to the 13 -6, right? They would actually use their PRA, they 14 would come up with plant specific, you know, delta CDF 15 numbers --
16 MEMBER CORRADINI: Okay.
17 MR. LEHNING: -- based on, you know, 18 whatever break size they chose to -- or whatever 19 breaks they chose to put in the risk informed bucket.
20 MEMBER CORRADINI: Okay. Well, I thought 21 I had it. Let me say it differently. You're saying 22 that in some sense, the TER is a guide to how they 23 might have to do it if they find themselves in the 24 yellow box?
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62 1 things for them to look at.
2 MR. KLEIN: I think the TER also informs 3 path four, because if you go through the first three 4 paths and you hit the red box, then the question is, 5 you know, do you do something to disrupt an inlet bed 6 before chemical affects four?
7 And then if the answer is yes, then you go 8 into more of a WCAP 17788 analysis. So you might be 9 given more credit for that analysis and being within 10 the -- all the key parameters of the staff TER in that 11 block four, as well.
12 CHAIR REMPE: So the TER isn't just the 13 yellow box, it's the -- how you created box four? Is 14 that a true statement? Because the TER helps you 15 confirm that those parameters could get you out of 16 there? Or --
17 MS. SMITH: I don't know if Ben had some 18 examples that helped the implementation when we talked 19 with the group. In the plant specific evaluation box, 20 he talks about how plants may be able to make a plant 21 specific evaluation if they didn't meet boxes one, 22 two, three, and four. So that's why I'm wondering if 23 Ben has some insights that --
24 CHAIR REMPE: Okay.
25 MS. SMITH: -- may answer your question.
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63 1 FEMALE: And you opened the bridge line?
2 CHAIR REMPE: I think it's open, because 3 I hear noise, but Ben, are you there?
4 MR. PARKS: Yes, this is Ben Parks with 5 the staff. Can you hear me?
6 CHAIR REMPE: Yes.
7 MR. PARKS: Okay. So this whole flowchart 8 and the staff guidance document is all purely 9 deterministic. There's no risk consideration here.
10 In fact, I think we have a paragraph in the guidance 11 document that says it can't align with these 12 deterministic evaluations, you can't show that, you 13 know, if you get a core inlet blockage, you're still 14 okay, then you need to pursue a different approach.
15 And that's what Steve was talking about 16 with the risk informed LAR and the exemption to the 17 1546 requirement. So if you get down to path four and 18 you find that you don't meet the alternate flow path 19 evaluations that were in WCAP 17788 plane four, then 20 you need to do an evaluation to show, you know, that 21 you have a lower core power level than might have been 22 analyzed in 17788 for, you know -- you are much 23 greater than 20 minutes when you stopover.
24 Basically kind of, like, one approach or 25 one strategy there is you'd be chasing down and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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64 1 showing that you have less decay heat than the 2 industry's analyzed, and so a much less severe event 3 than it may seem. And that way, you have assurance 4 that even if you have a core inlet blockage, you don't 5 have core damage follow it.
6 MEMBER CORRADINI: So let me say it back 7 to you. We're following a deterministic set of 8 questions, and I get to box four, and we haven't 9 looked at 17788, it's too darn big. So therefore, 10 there's something within 17788 that says the core 11 fiber limit is above some set of numbers we don't need 12 to discuss, and the switchover point is greater than 13 20 minutes. And what's RTP?
14 MS. SMITH: Rate of terminal power.
15 MR. SMITH: Rate of terminal power.
16 MEMBER CORRADINI: Oh, okay, thank you.
17 Less than evaluated, and the flow resistance is by the 18 other holes in the core are -- the resistance are 19 less, you're okay, you go to the right, and you've 20 essentially succeeded. If I don't and I go down to 21 the yellow box on plant system evaluation, that tells 22 you you're in a state of uncertainty, and the staff --
23 the licensee could use the TER as a roadmap to do a --
24 its own sort of plant specific evaluation?
25 MR. SMITH: That's correct.
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65 1 MEMBER CORRADINI: So have I essentially 2 said it about right?
3 MR. SMITH: That's correct, and the only 4 time they --
5 MR. PARKS: Yes.
6 MR. SMITH: -- the only time they would 7 get into any kind of a risk evaluation is if they 8 couldn't show, you know, that actually, our 9 thermopower is low, so, you know, we had an early 10 switchover time. So we would actually be below the 11 value that was calculated in the WCAP 12 MEMBER CORRADINI: Okay, fine.
13 MR. SMITH: They could use those to 14 evaluate against each other, and if they couldn't do 15 that, then they might get into the point where they 16 have to come ask for an exemption and say, okay, 17 certain breaks, we can't mitigate.
18 CHAIR REMPE: But you never proved the 19 WCAP, but your evaluations that you did in support of 20 the TER gave you confidence that the criteria in four 21 were acceptable. So that's why I'm saying I thought 22 that basically, you wouldn't even have box four if you 23 hadn't have done all of this work for the TER. Is 24 that a true statement?
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66 1 report up to a certain point, and there were some 2 areas that we felt was going to take a significant 3 amount of time and effort to resolve, so we were given 4 direction to go with this other path. So it's not 5 that we never agreed with what was in the top report.
6 We didn't finish our evaluation.
7 CHAIR REMPE: Right.
8 MS. SMITH: And this allowed us to show 9 box four, okay, it sounds pretty good.
10 CHAIR REMPE: So if you had not done all 11 this work for the TER, you could've made the 12 conclusion for box four and said it was fine, it was 13 just there were other things that you couldn't. So 14 you didn't need all this, the trace calculations even 15 do say those questions would let you go to a yes. I'm 16 trying to understand and I'm asking both questions 17 both ways to see what you say.
18 MS. SMITH: Yes, TRACE helps us support 19 the conclusion that in box four, we think is okay.
20 CHAIR REMPE: So my first statement was 21 correct? Granted, the TER will inform the yellow box, 22 but the work you did for the TER also gave you 23 confidence that box four was -- could be accepted and 24 you could go directly to yes? So it did help you 25 confirm the adequacy of box four?
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67 1 MS. SMITH: Yes.
2 CHAIR REMPE: Okay.
3 MEMBER CORRADINI: Okay. So after all of 4 that, now I am confused. Table two of the document we 5 were supposed to read has a set of numbers, which we 6 don't need to talk about what they are. Are those the 7 numbers in box four?
8 MS. SMITH: The debris less than 17788 9 core inlet, yes.
10 MEMBER CORRADINI: Okay.
11 MS. SMITH: Yes.
12 MEMBER CORRADINI: But those were -- as I 13 understand it, were calculated using a set of 14 calculational procedures that was not exactly 17788?
15 I thought there were -- my reading of the document was 16 that you actually went through a set of what I'll call 17 conservative assumptions that were not necessarily the 18 same as 17788 to get those numbers. Am I wrong?
19 MR. SMITH: These numbers in that chart 20 all came from 17788.
21 MEMBER CORRADINI: Oh, and that is what is 22 being used as reference in the box four question?
23 MS. SMITH: Right.
24 MR. SMITH: Yes.
25 MEMBER CORRADINI: Got it. Okay.
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68 1 MR. SMITH: These numbers assume, you 2 know, a uniform debris bed at the core inlet and all 3 that, so --
4 MEMBER CORRADINI: Yes, yes, yes.
5 MR. SMITH: -- that's why we think there's 6 margin.
7 MEMBER CORRADINI: But that's what leads 8 you to the next step about having to then evaluate the 9 alternative flow paths with some empirical determined 10 resistance or size that you must be below?
11 MR. SMITH: Right.
12 MEMBER CORRADINI: Or the resistance must 13 be below, or the size must be above?
14 MR. SMITH: Yes.
15 MEMBER CORRADINI: Okay. All right. Got 16 it. I think I got it.
17 CHAIR REMPE: So let's open up, I think 18 the line's still open, but Pete or Matt, do you have 19 any more questions?
20 MEMBER RICCARDELLA: This is Pete. I just 21 had one. So do I understand you to say that if a 22 licensee gets into the yellow box at the very bottom, 23 that that requires a license amendment?
24 MR. SMITH: It may.
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69 1 would only do that if they couldn't evaluate the key 2 parameters and show -- say there's some switchover 3 really came at the earliest potential switchover 4 actually came at 30 minutes, and their rated thermal 5 power was lower than what was evaluated, they could 6 show that their decay heat was below the value that 7 was evaluated in the WCAP.
8 And that would be a relatively simple 9 calculation, and in that case, you know, the plant 10 specific evaluation would be relatively simple. Now, 11 if they couldn't do that, and they had to say, okay, 12 it's going to -- we have x number of breaks that won't 13 get us below this core fiber limit, and we're going to 14 have to take those out, then they would have to use a 15 risk informed LAR.
16 MEMBER RICCARDELLA: Oh, I see, you have 17 to take those out, or you just have to assume --
18 MR. KLEIN: Assume core --
19 MEMBER RICCARDELLA: -- so an overall risk 20 informed -- or risk based approach would require a 21 license amendment?
22 MR. KLEIN: Yes.
23 MEMBER CORRADINI: But an individual 24 calculation to show on any one of the things that 25 brought you down to the no question might be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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70 1 calculable on a case by case basis?
2 MR. SMITH: Right.
3 MR. KLEIN: Correct.
4 MEMBER RICCARDELLA: So that would be 5 effectively a yes to four then, really.
6 MR. SMITH: Yes.
7 MEMBER RICCARDELLA: In effect.
8 MR. SMITH: Yes.
9 MEMBER RICCARDELLA: Okay. Yes.
10 MR. KLEIN: So the thought was that 11 licensees that enter block four, the further out of 12 bounds they were, the more likely they might get into 13 a situation that required an LAR. But if they were 14 slightly out of bounds, they might be able to show 15 that they really are inbounds by taking credit for 16 other features of the plant.
17 MEMBER RICCARDELLA: So refresh my memory.
18 Did South Texas do a license amendment?
19 MS. SMITH: Yes.
20 MR. SMITH: Yes.
21 MEMBER CORRADINI: We reviewed that. It's 22 called RoverD, Rover.
23 MR. SMITH: RoverD.
24 MEMBER RICCARDELLA: Yes. Understand. I 25 remember reviewing it, I just didn't remember if it NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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71 1 was part of a license amendment or not.
2 CHAIR REMPE: Okay. Do any of the members 3 or the -- here in the room or members on the phone 4 have any more questions or comments? We do need to 5 also go to public comments before we might possibly 6 close the meeting.
7 So at this point, too, could members speak 8 up and say if they think they need to have a closed 9 meeting? Looking around the table and it's pretty 10 quiet. What about Pete and Matt, do you guys have any 11 additional questions or comments for a closed meeting?
12 MEMBER RICCARDELLA: Nope, nothing further 13 from me.
14 CHAIR REMPE: Okay.
15 MEMBER SUNSERI: This is Matt. I don't 16 have any additional questions. I thought the 17 flowchart and the technical evaluation report were 18 quite helpful, actually. Thanks.
19 CHAIR REMPE: Okay. Thank you. So at 20 this point, let's see if any of the public in this 21 room have any questions or comments. And with that, 22 I'm not hearing any, I'll go around and ask members if 23 they have any final closing comments.
24 MEMBER CORRADINI: People on the line?
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72 1 members on the line that want to speak up and make a 2 comment? So not hearing anything, I guess we'll go 3 around the table for closing comments, starting with 4 Member Ballinger.
5 MEMBER BALLINGER: No further comment.
6 CHAIR REMPE: Harold?
7 MEMBER RAY: No, I don't think so.
8 CHAIR REMPE: Mike?
9 MEMBER CORRADINI: So, I guess I have a 10 number of comments. Since you've been doing this for 11 a long time, it's kind of not going out with a bang, 12 but a whimper, and that worries me, for two -- for 13 three reasons. One, you have an integrated decision 14 making process which is not standard operating 15 procedure.
16 You have essentially developed something 17 which could be beneficial, so it seems to me some sort 18 of documentation of that integrated decision making 19 processes would be beneficial for the rest of the 20 staff, because there are going to be other things that 21 linger that could be transformed to use at the 22 technique, right?
23 But I think you've got to somehow at least 24 talk through the process, because I thought the 25 process, as you walked through in terms of what were NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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73 1 the safety margin -- or what were the set of 2 assumptions, what were essentially the defense in 3 depth measures, what was the safety margins in each of 4 the defense in depth was a way to get you to the final 5 end state that I thought was good, so that's the first 6 thing.
7 My second thing is documentation of the 8 pieces -- Pete talked about xLPR. I don't know enough 9 to appreciate that, but at least with the TRACE 10 calculations, if they truly are conservative, even 11 though it's a small community, I think some sort of 12 documentation of that would be useful.
13 MR. SMITH: It's reference 21.
14 MEMBER CORRADINI: It's reference 21. So 15 there is something out there we can look at?
16 MS. SMITH: Yes, I don't know if that's 17 public, though, so --
18 MEMBER CORRADINI: Yes, I'm sure it isn't.
19 MEMBER RAY: Mike, I'm going to just 20 interject into your question. You used the word it, 21 and you said it was going out with a whimper. What do 22 you mean by it, because --
23 MEMBER CORRADINI: GSI-191.
24 MEMBER RAY: Well, all right, but that 25 doesn't end the ongoing process, that closure.
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74 1 MEMBER CORRADINI: No. The evaluation for 2 the generic letter is going, but what I guess I'm 3 getting at is, what's bothering me is, you have a 4 technical basis document that strikes me as 5 incomplete. It's incomplete because the decision 6 making process is not -- incomplete because I would 7 think there are pieces of the calculation that ought 8 to be properly documented.
9 And the third part of it, to me, is that 10 if this was the public and the public just by 11 weariness is not around to listen to it, would be 12 confused as to why it's significantly conservative.
13 I mean, I really do think you guys have a case, and 14 I'm not arguing with the case.
15 I'm just not clear that the document is 16 clear so somebody can look at it and say, a-ha. We've 17 already been worrying about this for a decade when we 18 shouldn't have, or they've developed enough 19 experimental information that now, we feel confident 20 that it is a low safety.
21 So those are the three things that -- I 22 know it's more work, it takes resources, I understand 23 all that, but it just strikes me that these would be 24 beneficial for the technical basis, not for the 25 evaluation. I think now I finally understand why NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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75 1 that's different.
2 MS. MARSHALL: Okay, well, if I may, this 3 is Jane Marshall with NRR DSS. A lot of the risk 4 informed decision making processes that we use are 5 documented in other procedures in other places for 6 NRR. So they're not necessarily repeated in this 7 document.
8 CHAIR REMPE: And the staff tell us this 9 is a new way of doing things earlier in this meeting 10 today?
11 MS. MARSHALL: It's a new way, broadly, a 12 new way of looking at things across all of NRR's 13 processes, not just isolated to GSI-191 resolution.
14 We're looking at risk informing as many of our 15 processes --
16 CHAIR REMPE: Right.
17 MS. MARSHALL: -- as we can, and you know, 18 I would like to highlight, there is a difference 19 between risk informing and risk based, as long as we 20 get through. So, and I know it's easy for some of the 21 members of the public to look at those as the same 22 thing, so I wanted to highlight they are separate 23 processes. NRR has an inner office instruction and 24 some other guidance to staff on risk informing these 25 processes.
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76 1 MR. BORROMEO: This is Josh Borromeo from 2 the staff. Jane, I think the office instruction you 3 are talking about is LIC-206. It's recent formed 4 decision making for LARs.
5 MEMBER CORRADINI: And this followed that 6 procedure?
7 MR. BORROMEO: Probably not, because it 8 was released in June, I think, of this year. June 9 2019.
10 MS. MARSHALL: It follows the ideas, but 11 not the processes.
12 MR. SMITH: This isn't a LAR.
13 MS. MARSHALL: Yes.
14 MEMBER CORRADINI: This is what?
15 MR. SMITH: The TER isn't a LAR, either.
16 So a lot of the license amendment requires --
17 MEMBER CORRADINI: Oh, oh, I'm sorry.
18 MR. SMITH: -- and that's the same with 19 Reg Guide 1.174. It's written for license amendment 20 requests, but we still use the ideas from these things 21 --
22 MEMBER CORRADINI: Okay.
23 MR. SMITH: -- when we did the evaluation.
24 MEMBER CORRADINI: What I guess I'm 25 getting at, to put it in a simple thing, I think this NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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77 1 is a good piece of work. It kind of is now going to 2 sit somewhere quietly, but I do think since when I 3 started with the committee, this was a lot of 4 discussion --
5 MR. SMITH: Right.
6 MEMBER CORRADINI: -- in 2005 and 2006.
7 And it just strikes me you essentially put a cap on it 8 technically, and it would be good to essentially wrap 9 it up in these three areas. But I think the staff has 10 done a very good job, personally.
11 CHAIR REMPE: I can come back to your 12 comments, but let me let Matt and Pete have a chance 13 to give their final comments, and then I'd like to 14 discuss what you're saying a bit more, Mike, okay?
15 MEMBER CORRADINI: Mm-hmm.
16 CHAIR REMPE: Matt, do you have any final 17 comments?
18 MEMBER SUNSERI: No, I don't have anything 19 else to add, Joy, thank you.
20 CHAIR REMPE: Okay. Pete, do you have any 21 comments?
22 MEMBER RICCARDELLA: Nope, nope, I don't.
23 I just, I'm happy to see the staff actually making use 24 of the xLPR work. Preliminary as it might be, it's 25 important.
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78 1 CHAIR REMPE: So I know you just joined 2 us, but Walt, did you have any comments you wanted to 3 make while you're on the table?
4 MEMBER KIRCHNER: No, thank you.
5 CHAIR REMPE: Okay. So you've listened to 6 what Mike has said. Does the staff -- I mean, he's 7 made discussion a couple of pretty good suggestions, 8 such as documenting the cases and how much margin 9 there is, and to provide someone who's less familiar 10 with the topic an easier to understand path of what 11 occurred here, and to better justify your approach and 12 why it's valid.
13 Does the staff have the opportunity they 14 might consider these suggestions? Or you're saying, 15 nope, we're done and that's it, we've already got the 16 guidance document out, the industry's happy with it, 17 they said it's going to be easy to follow?
18 MR. SMITH: I see Mirela's stepping up to 19 the table, so I'm going to let her answer.
20 MS. GAVRILAS: So this is Mirela Gavrilas 21 of the staff. I think the points that you guys are 22 raising are very important, because it is a paradigm 23 shift. It's not happening in a vacuum, though. I 24 mean, all the principles that have been involved in 25 this decision making are related to 1174.
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79 1 What is new is the fact that we actually 2 used them for decision making for a decision that's 3 other than a licensing action, and while it didn't 4 occur to us for this -- in this specific context that 5 we should take the next step and see what we can 6 document so that it becomes a generally useful tool 7 for the -- for future decision making, I think you're 8 making a very good point, and we'll certainly consider 9 that.
10 With regard to the margins that actually 11 gave the staff the confidence to call this a low 12 safety significance scenario or phenomenon, we will 13 want to document that, as well. So I think that 14 you're right. We'll go back and see in the context of 15 knowledge management if we can document the various 16 margins that actually led to the elements of 1174 that 17 actually led us to conclude that this is low safety 18 significance. So we will do that, because it is of 19 value to do. Folks are going to be using this similar 20 approach in the future.
21 CHAIR REMPE: Because as Mike emphasized, 22 GSI-191 was a pretty hot topic there for a lot of 23 years, and again, you may appreciate having that 24 documented now before staff may retire or move to 25 other topics that they're interested in.
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80 1 MS. GAVRILAS: And let me give credit to 2 Vic Cusumano, who is not here today, but what Vic 3 always says is, we got here because we worked very 4 hard for the past -- not just the staff, but industry 5 and everybody worked very hard to understand what's 6 going on so that we can make a conclusion that we've 7 presented to you today.
8 So, and we do want to make sure that we 9 actually document that knowledge in a manner that's 10 transparent and easy for others to follow and easy for 11 the public to understand. It's a very good comment, 12 we'll hear you.
13 CHAIR REMPE: Okay.
14 MEMBER RAY: Let me interject here, 15 though, then, because, you know, I went through the 16 AP1000 design certification as the secondary chair.
17 Another reason it occurs to me for doing what Joy and 18 Mike have discussed is, the logic associated with 19 closure of GSI-191, isn't it potentially relevant to 20 future applications for design certification, or 21 standard design approval, or whatnot?
22 In other words, if it -- the only thing, 23 as I understand it, that we're doing today is closing 24 GSI-191. If I'm a licensee, I've got to do the same 25 thing I've always had to do. I follow the flowchart NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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81 1 up there and do what I'm obligated to do.
2 But if I'm a potential applicant for a 3 design certification, for example, isn't there 4 information here that I would want to draw upon, 5 whether I was staff or applicant, in the future?
6 MS. GAVRILAS: I just want to be careful, 7 because we have the standard review plan for 8 applications, in general. We have an effort right now 9 to revise the standard review plan to consider risk 10 information.
11 In other words, what findings must the 12 staff make before they have reasonable assurance of 13 adequate protection in any of the regulations? So I 14 want to be careful to not convolute this effort with 15 what's going on there. We have to give some thought 16 where to put it.
17 We have a lot of risk initiatives going on 18 right now in the agency, and to put them all in a 19 cohesive structure is not trivial, it's not easy.
20 This is one of them, and I think we need to figure out 21 where it fits, but we're hearing you that we need to 22 figure out how we can take it beyond what it means to 23 closing GSI-191 and how we can apply what we learned 24 here to other type of regulatory decision making, 25 whatever that decision making may be.
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82 1 MEMBER RAY: That's fine, and also, as 2 they say, perhaps make it accessible by a potential 3 applicant, not just buried in some staff.
4 CHAIR REMPE: So is there a way we can 5 help you make sure that this gets done? I mean, we 6 aren't requested to write a letter on this, and we 7 probably won't get into the technical details of the 8 process, but to say some of the aspects that we feel 9 are important and should be documented in a letter.
10 Again, I'm a member speaking in a 11 subcommittee meeting, and it would have to go through 12 the full ACRS, but if we were to do something like 13 that, does that make this a little more concrete so 14 what we're asking gets done for those members who feel 15 like it should be done?
16 MS. GAVRILAS: So, we talk about it 17 amongst ourselves that it's, you know, the committee's 18 provocative to ask us to come in front of the 19 committee, and so we've given you the overview to the 20 subcommittee. And if the committee feels that it 21 would be of value to come and talk to the full 22 committee, and the committee wants to write the 23 letter, then by all means, we'll support it.
24 CHAIR REMPE: Okay, but does it help make 25 sure something gets done is what I'm asking. Yes, we NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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83 1 can do this, but does it matter as far as you feel 2 like, eh, we're going to do it no matter what, you 3 guys -- it's a waste of our time to come down and have 4 to do this --
5 MS. GAVRILAS: We are committed to 6 basically implicate risk in agency decision making to 7 the maximum extent possible. So this will be one of 8 the things that we will consider. Am I going to say 9 100 percent? I'm not quite sure what's on their to-do 10 list, so how quickly it gets done --
11 CHAIR REMPE: Yes.
12 MS. GAVRILAS: -- may depend, but I think 13 we'll strike the iron while it's hot, and we are 14 committed, the management in NRR is committed to 15 utilizing all the good lessons to have them share 16 about with internal and external stakeholders.
17 CHAIR REMPE: Do any members want to speak 18 up and say something we should do before we close 19 this, or just --
20 MEMBER CORRADINI: I'm out. I'm not going 21 to say a word.
22 CHAIR REMPE: Ron or Harold?
23 MEMBER RAY: No, I'm just thinking about 24 this for the first time. I would need some more time 25 to reflect on it.
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84 1 MEMBER CORRADINI: Can I ask Mirela a 2 slightly different way of the question? So have you 3 already thought down the line, you've done a TER, 4 which has shown a -- which has a technical basis for 5 the conclusion.
6 You now have compliance evaluation 7 guidance, which is being approved, or has been 8 approved, or whatever, right, and it's out on the 9 street. Except for what I'll call knowledge 10 management, which I think is important, are you 11 committed to that, regardless?
12 MS. GAVRILAS: To the knowledge 13 management?
14 MEMBER CORRADINI: Yes.
15 MS. GAVRILAS: Yes.
16 MEMBER CORRADINI: Okay, fine. That's 17 what I thought you said. I wanted to make sure.
18 Okay.
19 CHAIR REMPE: So I'm going to close this 20 meeting, unless I hear anything else from Matt and 21 Pete. Going, going, gone, and with that, I'll close 22 this hearing.
23 (Whereupon, the above-entitled matter went 24 off the record at 2:40 p.m.)
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Technical Evaluation of In-vessel Closure Based on Low Safety Significance for Generic Safety Issue - 191 ACRS Subcommittee Meeting September 16, 2019 Steve Smith, NRR/DSS/STSB Paul Klein, NRR/DMLR/MCCB Ashley Smith, NRR/DSS/SRXB
Presentation Outline
- Recap from April 2019 meeting
- Staff technical evaluation (TER) of in-vessel downstream effects (IVDEs) (ML19178A252)
- Comment/resolution since April 2019 meeting
- GL 2004-02 staff review guidance development 2
Recap from April 2019 Meeting
- Provided background
- Described industry and NRC actions related to Generic Safety Issue (GSI) - 191 and Generic Letter (GL) 2004-02
- Described the approach to address IVDEs
IVDE Safety Significance Approach
- Align agency/industry resources in accordance with safety significance of issue
- Staff TER - evaluate the overall significance of IVDEs, considering new and existing knowledge
- Safety significance criteria determination used various sources of information
- Defense in depth is maintained assuming complete blockage of core inlet 4
Technical Evaluation (TER) Scope
- Evaluation of IVDE safety significance only
- Integrated decision-making:
- Engineering judgment, qualitative, quantitative, and risk information used
- Not evaluating regulatory compliance
- TER provided supporting information to close GSI-191
- TER will be considered in closing GL 2004-02 5
Primary Flowpath Maintained
- Uniform bed formation is unlikely
- Breaks that reach core blockage debris threshold are very low frequency
- Long-term core cooling (LTCC) maintained with core inlet 99% blocked
- WCAP-16793 single fuel assembly tests - tolerate high quantities fiber/particulate without precipitates
- WCAP-17788 chemical effects timing - almost all plants go to hot-leg switchover (HLSO) (or equivalent) before precipitation, debris bed disruption expected 6
Overview - Defense-in-Depth Defense-in-Depth Measures Operator Core Inlet Blocked Refill Alternate Flow Action: Start Hot Leg Containment RWST/Direct Paths (AFPs) Reactor Coolant Switchover Integrity Injection Pumps Cleaner Provides AFP may injection water Disrupts and additional provide Disrupts debris may provide bypasses debris fission product adequate bed adequate bed barrier if fuel cooling cooling cladding fails Defense-in-Depth Outcomes 7
TRACE Analyses Various sensitivity studies completed by RES result in the following conclusions:
- Boric acid precipitation (BAP) was not found to inhibit LTCC with significant blockage at the core inlet
- AFPs are a viable option to maintain LTCC for both cold-leg breaks (CLBs) and hot-leg breaks (HLBs) 8
Staff Technical Evaluation Conclusion
- Staff concluded that IVDEs are of low safety significance for plants that address the key parameters identified in the TER 9
Safety Significance Criteria Used available guidance to determine definition of risk Frequency of LOCAs to challenge LTCC via IVDEs 10
Use of TRACE
- Clarified how TRACE was used to inform conclusions
- Added a table to describe various TRACE sensitivity studies performed 11
Break Size Sensitivity
- Compared WCAP-17788 most conservative limit to lower 15 g/FA limit from WCAP-16793
- The 15 g/FA value can be met using the same break size and other inputs except:
- Fiber penetration value is reduced from the most conservative value (15%) to the second most conservative value (12%)
- Penetration values from plant specific testing 12
LOCA Frequencies -xLPR
- Parametric study was conducted using xLPR Version 2 to estimate LOCA frequencies
- A variety of pipe sizes, degradation mechanisms, inspection schedules, and leak detection credit were investigated
- Preliminary results suggest that LOCA frequencies in NUREG-1829 are conservative
- Further sensitivity study is underway to investigate impacts of uncertainties in key variables (e.g., weld residual stress, loads, and cracking frequency)
GL 2004-02 Staff Review Guidance
Purpose:
Provide guidance to the NRC staff to evaluate licensee demonstration of compliance with 10 CFR 50.46(b)(5) for addressing debris impacts
- Status: Issued September 4, 2019 (ML19228A011) 14
BACKUP SLIDES 15
Comment/Resolution ACRS
- Clarified use of TRACE
- Staff verified 15 g/FA and 6-inch minimum break size
- Additional information added to clarify brine testing
- Clarified TER safety significance statement
- Clarified HLSO based on BAP is in emergency operating procedures
- Clarified tblock, tchem, and Kmax
- Clarified why the CLB bounds the HLB
- Clarified the use of STP assumption for lowest fibrous debris limit
- Additional language added regarding uniform resistance calculations
- Clarified that the use of risk numbers developed to define safety significance for use in the TER to define IVDEs only applies to this review 16
Comment/Resolution Staff Peer Review and PWROG
- TER was revised to address both staff peer review and PWROG comments, some of which are listed below:
- Clarity
- Purpose
- Safety significance threshold
- Reliance on TRACE
- Correction to description of how flows, break size and debris generation are related
- Applicability to new reactors
- Loss-of-coolant accident deposition model (LOCADM) as key parameter
- Sump switchover timing 17
Plant LOCA Response Spray nozzles Fuel Assemblies Tank RWST Heat exchanger Valve Strainers CSS SIS Sump Safety Injection Containment Spray System (CSS)
(SIS) 18
Overview - Safety Margin LOCA Size for Recirculation Coating Chemical Hot Leg Debris Fiber Core Inlet Attribute Debris Swapover Failure Effects Swapover Transport Penetration Fiber Generation Time Unqualified Timing Timing 100% Fines 24 Hours Assumption 6-inch 20 minutes 100% Fine 15% Uniform 6 Hours Transport Maximum
<15%,
<100%
Most Some fines Decrease Plant
<6-inch >30 minutes Time Non-Uniform 24 Hours Probable trapped with break Specific dependent size More debris Core inlet settles More debris unblocked Consider Less debris is before Some fail as Depends on Margin <100% required to w/o actual plant likely reaching Chips Plant Design block core Chemical timing sump, Lower Effects decay heat Time in Initial Switchover and Early Recirculation Long-Term Effects Transient Recovery 19
TRACE Analyses CLB BAP HLB BAP/AFP HLB AFP CLB AFP Purpose Evaluate effects of Evaluate Evaluate PWROG Evaluate debris buildup at effects of conservatisms PWROG core inlet on BAP debris buildup conservatisms at core inlet on BAP and LTCC Model DEG, 4-loop W upflow, mid-peaked DEG, CE, top-peaked axial, ANS axial, ANS 79 79 Cases/ 99.9% blocked - 99.5-100% -Decay heat -Base case Sensitivities LCP blocked core -Bypass only 100% blocked inlet -Blockage timing nozzle -Rate of blockage
-HLSO time, decay -HPI flow heat, axial skew 20
Key Parameters
- Initiating event frequency
- Fibrous debris
- HLSO (or equal) to dilute amounts debris, chemicals, BAP
- Minimum ECCS flow
- Chemical timing vs. AFP
- FA debris capture timing characteristics
- Chemical effects
- AFP resistance value methodology
- CLB driving head
- SSO timing
- RCS liquid mass
- Particulate debris amounts
- LOCADM 21
Staff GL 2004-02 Evaluation 22