ML21223A034
| ML21223A034 | |
| Person / Time | |
|---|---|
| Issue date: | 07/23/2021 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| Snodderly, M, ACRS | |
| References | |
| NRC-1599 | |
| Download: ML21223A034 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Radiation Protection & Nuclear Materials Docket Number:
(n/a)
Location:
teleconference Date:
Friday, July 23, 2021 Work Order No.:
NRC-1599 Pages 1-111 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005 (202) 234-4433
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com 1
1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 UNITED STATES OF AMERICA 1
NUCLEAR REGULATORY COMMISSION 2
+ + + + +
3 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 4
(ACRS) 5
+ + + + +
6 RADIATION PROTECTION & NUCLEAR MATERIALS 7
SUBCOMMITTEE 8
+ + + + +
9 FRIDAY 10 JULY 23, 2021 11
+ + + + +
12 The Subcommittee met via Video 13 Teleconference, at 9:30 a.m. EDT, David Petti, 14 Chairman, presiding.
15 COMMITTEE MEMBERS:
16 DAVID A. PETTI, Chairman 17 RONALD G. BALLINGER, Member 18 DENNIS BLEY, Member 19 CHARLES H. BROWN, JR. Member 20 VESNA B. DIMITRIJEVIC, Member 21 GREG HALNON, Member 22 WALTER L. KIRCHNER, Member 23 JOSE MARCH-LEUBA, Member 24 JOY L. REMPE, Member 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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2 MATTHEW W. SUNSERI, Member 1
2 ACRS CONSULTANT:
3 MIKE CORRADINI 4
STEVE SCHULTZ 5
6 DESIGNATED FEDERAL OFFICIAL:
9 ALSO PRESENT:
10 GREG BROADBENT, Entergy 11 JERRY DOZIER, NRR 12 MIKE FRANOVICH, NRR 13 KEVIN HSUEH, NRR 14 STEVE JONES, NRR 15 SCOTT MOORE, Executive Director, ACRS 16 JOHN PARILLO, NRR 17 FRANCES PIMENTEL, NEI 18 SHILP VASAVADA, NRR 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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3 CONTENTS 1
Opening Remarks.................
4 2
Discussion of Draft Final Interim Staff Guidance 6
3 Comments on Draft Final Guidance
........ 98 4
Opportunity for Public Comment 107 5
Adjourn....................
111 6
7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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4 P R O C E E D I N G S 1
9:30 a.m.
2 CHAIR PETTI: Okay, so I have 30 minutes 3
after the hour so let's have the meeting come to 4
order.
5 This is a meeting of the Advisory 6
Committee on Reactor Safeguards, Radiation Protection 7
and Nuclear Materials Subcommittee. I'm Dave Petti, 8
chairman of today's subcommittee meeting.
9 Members with us today are Charlie Brown, 10 Dennis Bley, Greg Halnon, Jose March-Leuba, Walt 11 Kirchner, Consultant Mike Corradini.
12 MEMBER REMPE: Dave, this is Joy. I'm 13 also here.
14 CHAIR PETTI: Yes, Member Joy Rempe, 15 Consultant Steve Schultz, Member Ron Ballinger, Member 16 Vesna Dimitrijevic, and Member Matt Sunseri.
17 Mike Snodderly is the Designated Federal 18 Official for this meeting. The subcommittee will 19 review the staff's draft interim staff guidance 20 entitled Supplemental Source Guidance for Radiological 21 Consequence Analysis Using Alternative Source Term.
22 We also have members of the NRC staff and NEI to brief 23 the subcommittee.
24 The ACRS was established by statute and 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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5 it's governed by the Federal Advisory Committee Act, 1
FACA. The NRC implements FACA in accordance with its 2
regulations found in Title 10 of the Code of Federal 3
Regulations, Part 7. The committee can only speak to 4
its published letter reports. We hold meetings to 5
gather information, perform preparatory work to 6
support our full deliberations at a full committee 7
meeting.
8 The rules for participation in all ACRS 9
meetings were announced in the Federal Register on 10 June 13, 2019. The ACRS section of the U.S. NRC 11 public website provides our charter, bylaws, agendas, 12 letters, of course, and full transcripts of all full 13 subcommittee meetings including slides presented 14 there. The agenda for this meeting was also posted 15 there.
16 As stated in the Federal Register notice 17 and in the public meeting notice posted to the 18 website, members of the public who desire to provide 19 written or oral input to the subcommittee may do so.
20 You should contact the Designated Federal Official 21 five days prior to the meeting as practicable.
22 We've set aside 15 minutes for comments 23 from members of the public, attending or listening to 24 our meetings. We have not received written comments 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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6 or requests for time to make oral statements for 1
members of the public regarding today's meeting.
2 A transcript of the meeting is being kept 3
and will be made available on the ACRS section of the 4
NRC public website.
5 It is requested that speakers identify 6
themselves and speak with sufficient clarity and 7
volume so they can be readily heard. Additionally, 8
participants should mute themselves when not speaking.
9 A telephone bridge line has been established for the 10 public to listen to the meeting. To minimize 11 disturbance, the public line will be kept in a listen 12 in only mode.
13 With that, we will now proceed with the 14 meeting. I call upon Mike Franovich, Director of the 15 Division of Risk Assessment in NRR to begin today's 16 presentations. Mike?
17 MR. FRANOVICH: Good morning, Chairman 18 Petti. If we could have Slide 2, please.
19 Good morning, Chairman Petti and good 20 morning, ACRS Subcommittee members. I am Mike 21 Franovich and I serve as the Director of the Division 22 of Risk Assessment in NRR. Thank you for the 23 opportunity today for the staff to share advances in 24 our regulatory reviews of radiological consequence 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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7 analysis using the alternate source term.
1 To set the stage, let me highlight a few 2
of the more recent regulatory transformations and the 3
performance shaping factors improving our efficiency 4
and reliability as regulators.
5 A key theme is that our licensing, other 6
regulatory decisions, and backfit/forward fit actions 7
must be risk informed and there are two particular 8
staff requirement memoranda that have been directing 9
those items here noted on the slide.
10 The Commission's recent direction reminded 11 the staff that we are enabled to use risk-informed, 12 performance-based approaches in our work. This 13 direction in 2019 also serves as an accelerant for 14 transformation become a more modern risk-informed 15 regulator.
16 The SRM, commonly referred to as the 17 NuScale Block Valve SRM, draws upon long standing 18 practices and in particular, a 1999 Commission paper 19 that states succinctly a risk-informed, performance-20 based approach is one of risk insights, engineering 21 analysis, and judgment including the principle of 22 defense in depth and the incorporation of safety 23 margins including performance history are used in 24 decisions.
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8 In 2018, we also received additional 1
clarifications from the Commission regarding 2
regulatory backfits and proper treatment of forward 3
fits. This Commission direction serves as a regulatory 4
stabilizing applying the reliability principles of 5
good regulations in our license amendment reviews.
6 Secondly, improved realism evaluation 7
techniques and additional information are applied to 8
improve risk-informed decision making.
9 As noted in a 2019 memo to the Executive 10 Director for Operations on applying risk-informed 11 principles, the NRC's application of risk-informed 12 decision making continues to evolve, as improved 13
- realism, evaluation techniques, and additional 14 information are applied to improve our decisions.
15 What that means to the staff when it comes to review 16 of applications to allow for possible increases in 17 leakage from BWR main steam isolation valves is that 18 there are tremendous opportunities to apply 19 engineering and risk insights. This mosaic of 20 information includes plant operating experience, as 21 well as our experiences from post-Fukushima activities 22 to make more realistic and ultimately better decisions 23 while abiding by the Commission's backfit and forward 24 fit expectations.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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9 And third, cultural realignment is needed 1
to ensure that we identify and resolve challenges and 2
roadblocks for the appropriate and consistent 3
integration of risk insights. Two important agency 4
activities address NRC internal cultural realignment 5
needs that are detailed in the previously mentioned 6
memo to the EDO. Most recently, the Be riskSMART 7
Initiative is driving agency-wide practices for a 8
uniform risk and reward mindset and use of graded 9
approaches in our safety, security, corporate support 10 and other agency business.
11 This concept is also applicable as we 12 assess licensees' request to allow for increased 13 leakage while satisfying overall plant performance 14 objectives, limiting potential consequences during 15 hypothetical accidents. For BWR MSIV leakage, here is 16 once again an opportunity to be mindful of radiation 17 dose ALARA objectives for workers who maintain these 18 MSIVs in terms of their performance.
19 Lastly, NRR continues to implement the 20 after actions of our 2018 risk-informed decision 21 making action plan and a key insight out of that plan 22 is promoting greater use of integrated review teams.
23 Today, you will hear from a diverse team 24 consisting of management, systems and component 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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10 experts, risk analysts, seismic experts, and accident 1
dose analysts supporting this Draft ISG.
2 And with that said, I will turn it over to 3
Kevin.
4 MR. HSUEH: Thanks, Mike. Good morning, 5
everyone. I am Kevin Hsueh, Branch Chief, Radiation 6
Protection and Consequence Branch in NRR, Division of 7
Risk Assessment.
8 I'll cover Slides 3 and 4 and we are 9
currently on Slide 3. In 2019, we received four 10 license amendment requests to increase MSIV leakage 11 allowed by tech specs for BWR. Traditionally, this 12 type of amendment requests were reviewed using 13 deterministic review methods.
14 In the SRM that might mention the NuScale 15 Block Valve SRM, the Commission directed the staff to 16 apply risk-informed principles in any licensing review 17 or other regulatory decision when strict, prescriptive 18 application of deterministic criteria is unnecessary 19 to provide for reasonable assurance of adequate 20 protection of public health and safety.
21 In response to this and other previous 22 risk-informed related SRMs and soon after we received 23 this amendment request, we started to look for ways 24 where we can increase use of risk insights to perform 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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11 this review.
1 After several months of efforts and a 2
number of meetings among NRR staff for more support 3
(phonetic) the regions staff developed a technical 4
assessment and followed NRR office instructions LIC-5 206 process to integrate this insight with these types 6
of traditional decommissioning reviews.
7 CHAIR PETTI: It looks like Member Rempe 8
has her hand up. She has a question, I think.
9 MR. HSUEH: Oh, okay. All right. Go 10 ahead.
11 MEMBER REMPE: Sorry, Kevin. I have a 12 question that is a bit off topic and it's probably due 13 to me not being fully informed on what the staff did 14 with these reviews, but again, we only saw the 15 Fitzpatrick and the ISG, but if the staff is going to 16 be using risk insights for design basis actions source 17 terms, I'm wondering if other risk insights were also 18 considered such as the impact on operator actions if 19 they allow increased leakage from the MSIVs.
20 As I think about how the operators would 21 know if the MSIV closed, there is probably differences 22 in temperature or radiation, monitor readings or 23 something like that, but again, they're used to seeing 24 increased leakage. And so I'm wondering if their 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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12 ability to detect that it really closed or if it 1
failed to close would be impacted.
2 Did the staff consider that as they risk 3
informed this process? Because I didn't see anything 4
about operator actions in what the staff sent back on 5
the Fitzpatrick request.
6 MR. HSUEH: Thank you for the question and 7
please hold that thought and maybe later on we can 8
touch base on that and we have the staff can answer 9
that question if it's okay with you.
10 MEMBER REMPE: Sure. It was something 11 that crossed my mind when I was reading this and 12 again, perhaps the staff did something and it just 13 wasn't in the documentation you were given. But I am 14 curious about that. To meet holistically, consider 15 risk insights, not just pick and choose things that 16 are going to address the consequences is what my 17 thought was.
18 MR. HSUEH: Okay. Thank you. So we will 19 answer -- respond to that at the staff's presentation 20 and I think that the staff is prepared to respond to 21 that question.
22 MEMBER REMPE: Great.
23 MR. HSUEH: All right, so I continue the 24 Slide 3. So during our review, we overcame many 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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13 changes and completed all four safety evaluations with 1
risk and engineering insights to support our 2
reasonable assurance finding. And to document our 3
reasonable assurance finding each of the four safety 4
evaluations includes new risk and engineering insight 5
section summarizing the finding and conclusion of a 6
technical assessment.
7 All four safety evaluations received OGC's 8
no legal decision (phonetic) individually prior to 9
staff approval of this amendment request.
10 Mike mentioned the November 2019 NRC memo, 11 agency's efforts in implementing the NuScale Block 12 Valve SRM. The memo highlights the staff's efforts 13 and staff's challenges and continuous efforts in 14 applying risk-informed principles in our decision 15 making and making the progress one decision at a time.
16 Consistent with the implementation of that 17 SRM and to memorialize our practice and experiences, 18 we developed this interim staff guidance or ISG. This 19 ISG serves as an example of our continuous effort in 20 working toward being a more modern and risk-informed 21 regulators.
22 Next slide.
23 We are now on Slide 4. In addition to the 24 ISG developments, there has been a separate on-going 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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14 effort to revise Reg Guide 1.183 in parallel.
1 Specifically, staff has restarted its efforts to 2
revise Reg Guide 1.183 since late last year to update 3
the current Rev. 0 which was issued in 2000.
4 A working group and a steering committee 5
were established with a step-by-step project plan to 6
keep the project moving efficiently and effectively.
7 So far, we have held three public meetings to seek 8
stakeholders' input and feedback on a variety of 9
proposed changes to Rev. 0 and completed a threat 10 revision.
11 The threat revision is currently being 12 processed by the Office of Research and the 13 subcommittee meeting on the threat revision is 14 scheduled in fall of this year.
15 So for today's meeting, we're trying to 16 focus our discussion on the threat ISG and how we use 17 the recent engineering insight to support our 18 reasonable assurance findings. With that, I'll turn 19 it over to Jerry to start that presentation.
20 MR. DOZIER: Hello. My name is Jerry 21 Dozier. I'm a Senior Risk and Reliability Analyst 22 from the Radiation Protection and Consequences Branch 23 in the Division of Risk Assessment.
24 In this presentation today that we'll 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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15 have, as Mike said, diverse skilled members of staff 1
will provide a presentation which will basically give 2
a background of the ISG, the basis for the ISG. We 3
were requested to provide about the difference between 4
this ISG and the Reg Guide as Kevin just mentioned, 5
and also how we use this ISG in the LARs. And then 6
we'll finish with a few takeaways.
7 MEMBER KIRCHNER: Jerry, this is Walt 8
Kirchner. May I just ask you for a little background 9
or context from you and your team about the BWR LARs?
10 The way the viewgraphs are written might lead the 11 public to -- might mislead the public into thinking 12 there's an issue with the performance of the main 13 steam isolation valves.
14 So could you just give us some context for 15 the record as to what the issues are? Again, the way 16 the viewgraphs actually read, kind of just on the 17 surface, is that you're allowing increased leakage 18 from valves. And it suggests that that might be 19 actually a problem. And of course, you've used your 20 risk-informed approach to determine that it is not.
21 But could you just provide a little more 22 context about the LARs and the issues with the main 23 steam isolation valves in BWR?
24 MR. DOZIER: Sure. Sure, I can. And also 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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16 basically for -- we have one of the reviewers of the 1
LARs toward the end of the presentation actually 2
talking about some of the challenges that were in the 3
LARs, how this was used to resolve that. However, 4
that will come a little bit later.
5 MEMBER KIRCHNER: Okay, I'll wait until 6
then. I just thought up front it might provide more 7
context for the public.
8 MR. DOZIER: Okay, and what I would like 9
to say that as far as the leakage, what the theme of 10 these LARs were, was basically it was the licensees 11 asking for an increase in allowed leakage in their 12 technical specifications. So it was -- that was the 13 whole purpose of the LAR was to ask for this increase 14 in the leakage. And of course, the reviewer has to 15 use our guidance to review this. And there was some 16 challenges even within our guidance that we resolved.
17 We'll talk about it in detail, talk about the slides, 18 if that's okay.
19 MEMBER BROWN: Did we lose the presenter?
20 MR. DOZIER: I'm still here. I was just 21 saying if that's okay with you.
22 MEMBER KIRCHNER: I'll wait.
23 MR. DOZIER: Okay.
24 MR. FRANOVICH: Thank you. This is Mike 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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17 Franovich, Director of Risk Assessment, NRR. I think 1
it's important to note here, as the staff will explain 2
further in the presentation. I'm sorry, I hear a 3
little bit of feedback on the line. I'm not sure all 4
the lines are muted.
5 The proposed amendments that came in 6
doesn't suggest or at least we're not aware of any 7
suggestion that they are some type of industry trend 8
issue with the performance of MSIVs. We've had other 9
plants that have requested increased allowables for 10 leakage. And so this is not necessarily a reflection 11 of issue with the components as an industry wide type 12 of issue in terms of trends. I just want to set that 13 out there for members of the public.
14 MEMBER KIRCHNER: That's what I was 15 thinking, Mike. You know, because just like I said, 16 a superficial reading of the viewgraphs would suggest 17 there's problems with the valves and now they want to 18 have a more allowance for leakage, et cetera, so thank 19 you.
20 MR. FRANOVICH: And if I can also add --
21 no, that's very fair. I appreciate you giving us the 22 opportunity to explain that because the other 23 tempering factor that the licensees are challenged 24 with is managing ALARA. And these are not small, low-25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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18 dose type of activities to overhaul our maintenance on 1
these types of valves. So there is a balancing there 2
between that of the needs for radiation protection for 3
the rad workers versus what would be an acceptable 4
increase in allowables for these hypothetical type 5
scenarios that we look at for consequence analysis.
6 MEMBER KIRCHNER: So just thank you. Just 7
one recommendation, when this comes before the full 8
committee, I think it would be important for that --
9 that context and background to be up front in the 10 presentation. Thank you.
11 MR. DOZIER: Slide 6. So for the overview 12 of the ISG, basically, this ISG was published in the 13 Federal Register on June 21, 2021. We did get 14 comments from NEI, as well as also some anonymous 15 comments. There was 13 from NEI, 20 anonymous 16 comments.
17 We'll have an ACRS full committee briefing 18 that's scheduled for November 2021. OMB approval 19 would be after that and we expect final FRN for this 20 to be February of 2021.
21 Slide 7.
22 MEMBER REMPE: I think you meant 2022, 23 right?
24 MR. DOZIER: Yes, as the slide --
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19 MEMBER REMPE: It's what's on the slide, 1
but, yeah, I can't do it in --
2 (Simultaneous speaking.)
3 MR. DOZIER: Thank you. Slide 7.
4 This ISG is expected to be transitioning 5
into SRP Section 15.0.1. Section 15.0.1 will include 6
a reference to the revised Reg Guide 1.183 that we are 7
working on as a separate project as was explained 8
earlier. Then the ISG will be closed after transition 9
to this section.
10 So this is kind of the high level primary 11 insights. We had many insights, but this is really 12 the primary insight that we're taking from this look 13 and that is that there's a high probability that doses 14 will be lower than those estimated strictly using 15 traditional deterministic methods and by using this 16 we're using all of the accepted assumptions that's 17 already in the guidelines. We're not changing those.
18 And what we're saying is that do not credit hold-up 19 and retention of the Main Steam Isolation Valve 20 leakage within the power conversation system.
21 So big picture. Piping and components 22 downstream of the MSIVs sees significant pressure, 23 temperatures, and vibrations 7 days a week, 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 24 a day while the reactor is operating. If the plant 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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20 does not ask for formal credit for hold-up in the 1
condenser, Reg Guide 1.183 assumes that the piping and 2
components disappear with a safe shutdown earthquake 3
and the MSIV leakage goes directly to the environment.
4 This is all that stuff after the second MSIV.
5 For plants requesting an increase in the 6
tech spec allowable MSIV leakage and they do not 7
credit the condenser, the staff may recognize that 8
there's a high likelihood that this robust, high 9
pressure pipe, and components is available for hold-up 10 instead of it being rubble on the floor to support the 11 staff's reasonable assurance.
12 And that was kind of the simple way of 13 maybe I could say these formal words.
14 MEMBER HALNON: So Jerry, this is Greg 15 Halnon. When you credit and make that assumption, 16 what is the condition of the piping downstream of the 17 second MSIV to a condenser that you're assuming that 18 it's all intact and then there's no additional leakage 19 or that there's a -- so that's one thing we don't do 20 in BWRs. We don't necessarily measure the leakage, 21 but we do have leakage.
22 You can just look at the amount of leak 23 repairs that are done on line through the power 24 conversion systems, MSRs, and other extraction, steam, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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21 steam trap and other things that are releasing it, not 1
realizing BWRs that's a lot more evident because 2
you'll have the radiological measurement of those 3
types of things, but there are quite a lot of leaks 4
that the industry deals with as they operate these 5
plants in those U.S. conditions.
6 So how did you assume that piping was 7
intact enough even in normal operation to get that 8
leakage to the condenser to have that hold up?
9 MR. DOZIER: Well, actually, you know, if 10 those valves -- okay, so those valves are the money 11 makers for the utility, okay? You know, so they're 12 very important valves for the plant.
13 We're going to go into detail on this 14 later in the presentation, but even if there is no 15 hold up, I mean especially if those valves close, you 16 know, there's really, as far as leakage to the control 17 room, you know, it's not any leakage, because 18 everything held up in that large PCF volume that we'll 19 get into.
20 MEMBER HALNON: Okay, well, if you're 21 going to get into more detail, we can hold the 22 question.
23 MR. DOZIER: Yes, I'll let the expert on 24 that one answer it.
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22 MEMBER HALNON: Okay. I can hold the 1
question, so we'd be -- start looking at full diagrams 2
and what not.
3 MR. DOZIER: Now I'm on Slide 9. In this, 4
as I said, this ISG is to make a formal footprint.
5 That's really what the objective is. The staff will 6
use this to offset uncertainties and input parameters 7
for deterministic calculations and supports -- and the 8
main thing is it supports the staff's reasonable 9
assurance finding during reviews and it will be 10 transitioned.
11 Now the most -- a very important caveat to 12 this is it does not change the licensee's 13 responsibility to demonstrate compliance within 10 CFR 14 50.67.
15 It also -- since we're using something 16 that probably 50 percent of the plants formally 17 credited earlier, and now we're doing for these LARs 18 that did not ask for this credit, we are not changing 19 acceptable methods for demonstrating compliance with 20 10 CFR 5067. So we're not changing things upstream 21 from these MSIVs or any of those assumptions.
22 As even in the opening remarks, now I'm on 23 Slide 10, given in the opening remarks, we're 24 basically trying to be a modern, risk-informed 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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23 regulator as we're directed. And the documents we 1
spoke about before, we had those four license 2
amendments submitted to us and they were asking for 3
increased MSIV leakage in 2019. We had some challenge 4
that we'll talk about later and since we had those 5
challenges, we invoked LIC-206 which is basically for 6
risk informed decision making that we do in reviews.
7 So this was a new process that we would follow.
8 We got an integrated review team --
9 MR. CORRADINI: Excuse me. This is 10 Corradini. Can you just remind people of what LIC-206 11 is? Maybe I'm the only one that doesn't remember.
12 MR. DOZIER: It's risk-informed decision 13 making and reviews, license amendment reviews.
14 MR. CORRADINI: Thank you.
15 MR. DOZIER: So it's specific to license 16 amendment reviews.
17 MEMBER BLEY: This is Dennis Bley. For 18 everybody else, maybe who hasn't been around a long 19 time on this, LIC-206 is worth reading. It's really 20 good background and you understand how people are 21 implementing some of the risk-informed activities.
22 MR. DOZIER: Dr. Vasavada, who will be 23 speaking
- later, was one of the contributors, 24 significant contributors to that document.
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24 Okay, it identified that risk insights 1
support consideration of holdup into PCS and ability 2
to -- okay, so we had that group and we looked at many 3
risk insights. There was many things we looked at. We 4
focused on just the condenser because we wouldn't have 5
to change up a lot of the very conservative 6
assumptions that was in Reg Guide 1.183. So we 7
focused on this holdup, okay? And we (unintelligible) 8 those insights and that technical assessment which you 9
basically see in the basis portion of the ISG. It was 10 talked about internally, multi-division, multi-people.
11 It was a team approach. It was lots of insight.
12 So we --
13 MEMBER REMPE: LIC-206 does say you need 14 to have a holistic approach, so are you the right 15 person to ask my question about did you consider the 16 impact on what the operators would see and if there's 17 some penalties associated with allowing increased 18 leakage. And I'll mention that at TMI, they changed 19 the tech spec for the core and they did see increased 20 leakage and that may be one of the reasons the 21 operators didn't detect that they had a small break 22 LOCA. So my question -- are you the right person or 23 is that going to come up later?
24 MR. DOZIER: I'm kind of waiting for the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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25 team to see if someone in the team wants to jump in on 1
that.
2 MR. JONES: This is Steve Jones. I'll be 3
speaking next and I can try to address that issue with 4
how testing and tech spec limits on the testing relate 5
to what operators would see and conditions that they 6
would respond to.
7 MEMBER REMPE: Great. Thank you. Again, 8
sorry, to keep bringing it up, but I am curious about 9
it.
10 MR. DOZIER: Okay, with that, we'll get 11 right into Steve's presentation to hopefully address 12 those, Dr. Rempe.
13 MR. JONES: Good morning. I'm Steve 14 Jones, a Senior Plant and Safety Systems Engineer from 15 the Containment and Plant Systems Branch in the NRR 16 Division of Safety Systems.
17 As Jerry went over the current guidance in 18 Reg Guide 1.183, specified the assumption of a direct 19 ground level release at the downstream MSIV when no 20 seismically qualified main steam piping downstream of 21 that MSIV is present.
22 In part, to address those issues, the BWR 23 owner's group developed a topical report and the staff 24 approved that in 1999 to allow computational credit to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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26 consider holdup and deposition within the main steam 1
piping and the main condenser as kind of indicated by 2
the dash line in the diagram to the right.
3 Roughly half of the operating boiling 4
water reactors have adopted this methodology which 5
significantly reduces the effect of mainstream 6
isolation valve leakage on the calculated dose 7
consequences as evaluated for the control room and the 8
site boundaries.
9 However, again, as Jerry mentioned, even 10 without a
thorough evaluation of the seismic 11 robustness of the main steam lines and the remainder 12 of the power conversion system, the staff determined 13 that there's significant evidence supporting the main 14 steam system and other parts of the power conversion 15 system would contribute to holdup and potential 16 deposition of fission products when not formally 17 credited in the dose calculation.
18 Slide 13, please.
19 Okay, this diagram shows the configuration 20 of the main steam system in a typical boiling water 21 reactor. The curved gray wall represents the dry well 22 or primary containment and the second straight gray 23 wall represents secondary containment boundary.
24 So the downstream main steam isolation 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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27 valves are the ones to the -- between the two gray 1
barriers, the air operated valves with the mushroom-2 shaped actuator depicted in this diagram. And then 3
this diagram indicates that there are several paths 4
once there's flow beyond the main steam isolation 5
valves and these paths include main steam piping 6
drains and turbine bypass valves that lead directly --
7 both of which lead directly to the main condenser.
8 In addition, there are other flow paths 9
through the main turbines, potentially steam driven 10 main feedwater turbines that could provide additional 11 holdup volumes for any main steam isolation valve 12 leakage.
13 Slide 14, please.
14 Going into just a little bit more detail 15 on our approach, the staff developed this overall 16 assessment considering the risk triplet for releases 17 beyond the main steam isolation valves. We considered 18 operating experience related to the ruggedness of 19 piping systems and other components and that operating 20 experience included the events at Fukushima, North 21 Anna earthquakes, and other events that demonstrated 22 the robustness of secondary plant system components 23 through earthquakes.
24 We also considered the pathways available 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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28 to the leakage without operator efforts or operator 1
actions to redirect flow to any specific location and 2
assessments of seismic capacity that Dr. Vasavada will 3
address in the later slides.
4 MR. DOZIER: Dr. Rempe had a question.
5 MEMBER REMPE: It's a different question 6
this time.
7 MR. JONES: Okay.
8 MEMBER REMPE: I'm curious about anchorage 9
of the piping and the condenser. And again, the 10 documentation we were given was very limited in that 11 area. But what assurance do you have that the 12 anchorage is similar, because that was one question 13 that I've seen raised in other forums about what can 14 we learn from the events at Daiichi and if the way 15 that the components were anchored were similar. And 16 did you investigate that?
17 And then I noticed you mentioned Onagawa 18 in your documentation. But you didn't mention what 19 you saw at Daiichi or Daini. And was there a reason 20 for that?
21 MR. JONES: No. I'm sorry. We were just 22 generally considering the operating experience 23 developed from the Great Tohoku Earthquake. And we 24 did consider the experience at some of the other sites 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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29 where we found documented information about, for 1
instance, the seismic damage that resulted from plants 2
that did not experience core damage events to the --
3 MEMBER REMPE: But --
4 MR. JONES: -- secondary system.
5 MEMBER REMPE: But Daini had no core 6
damage and yet it might've had a more -- did you see 7
any damage where the earthquake occurred too in the 8
condenser? Why just Onagawa?
9 MR. JONES: I guess I did not note any 10 documentation of specific damage states at that site.
11 MEMBER REMPE: Okay. And then also, do we 12 know at Anchorage at all of the plants for the 13 condensers and the piping is similar, not only in 14 Japan versus a U.S. plant but also even at North Anna 15 versus other U.S. plants?
16 MR. JONES: I guess from my perspective, 17 we're not really worried about quantitative credit.
18 We're just looking at, is there a volume for this to 19 go to and will there be some level of delay in the 20 release of the radioactive material that may propagate 21 through the system? Looking at these assessments, the 22 design-basis leakage rate would be on the order of a 23 couple -- a few hundred standard cubic feet per hour 24 or just a few cubic feet per minute. And even if the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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30 condenser loses structural integrity, it would still 1
provide an area or a volume that would retain the 2
fission products for a while until they find whatever 3
openings may have developed as a result of loss of 4
integrity. And Shilp -- Dr. Vasavada will be going 5
over a little bit more about the fragilities and how 6
a generic determination of structural stability was 7
established for the condensers in the next part of the 8
presentation.
9 MEMBER REMPE: Okay, thanks.
10 MR. HSUEH: Dr. Vasavada raised his hand.
11 I just wonder if you want to respond at this time.
12 MR. VASAVADA: Thanks, Kevin. This is 13 Shilp. I think Steve covered it, and I'll go in more 14 detail. And I can answer additional questions.
15 Steve's overarching point that you're not 16 giving quantitative credit and you're not trying to 17 draw exact comparisons but get just insights from 18 earthquake experience where plants have exceeded their 19 safe shutdown earthquakes and what that means for the 20 seismic capacity of the ECS components. That's what 21 we are trying to draw other than exact comparisons or 22 numerical credit. And I can talk in further detail or 23 answer any further questions when I go over that.
24 MR. HSUEH: Thank you.
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31 MR. JONES: Okay. Slide 15, please.
1 Okay. This slide gets into a little bit more detail 2
of the technical assessment. And it primarily looks 3
at the undesirable outcomes considered in the staff's 4
evaluation which reflect the default assumption of a 5
direct ground level release at the downstream main 6
steam isolation valve. Absent these undesirable 7
outcomes, the release would be maintained within the 8
main steam system and other attached piping systems 9
and components.
10 And these systems and components establish 11 a boundary for fission product holdup under conditions 12 where there's a very low differential pressure to 13 drive any release out. So just having the volume 14 present certainly delays the release and provides the 15 opportunity for additional deposition. Sorry. Slide 16 16, please. From the operational insights, the staff 17 determined that the typical steam system design used 18 the Power Piping standard and would be designed and 19 fabricated to augmented quality standards which 20 include consideration of a seismic load, design 21 verification, and establish our use of volumetric non-22 destructive examination techniques to verify the 23 fabrication and construction of the system.
24 The latest boiling water reactors have 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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32 fully safety-related main steam systems designed to 1
withstand the safe shutdown earthquake and design to 2
the ASME boiler and pressure vessel code out to the 3
turbine stop valves or, in some plants, the 4
intermediate stop valves which are located within the 5
turbine building. The main steam isolation values 6
themselves are angled globe valves that are designed 7
to seat more firmly with pressure from the reactor 8
side. The inboard valve may be tested in the opposite 9
direction of its normal seating design.
10 That is pressure could be applied between 11 the two MSIVs. And therefore, you might see higher 12 than actual leakage during the test. But you still 13 need to maintain test values within the technical 14 specifications.
15 Another testing methodology may rely on 16 steam line plugs where you test the inboard valves and 17 the outboard valves separately. But again, you're 18 subject to increased leakage because the plugs 19 themselves may be the source of leakage. So I just 20 wanted to address that from the standpoint of 21 conservatism with respect to the overall testing 22 program relative to the technical specification 23 leakage limits.
24 We also considered the potential -- sorry, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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33 I'm still on Slide 16 -- the potential for stem 1
leakage. But that is considered small and believe 2
would be addressed promptly by operators. Again, 3
we're not looking at specific credit for this 4
particular control, but we don't believe that would be 5
a significant contribution to offsite dose as it would 6
be a release to the steam tunnel in the boiling water 7
reactor. The main steam -- therefore, we concluded 8
the --
9 (Simultaneous speaking.)
10 MR. JONES: Yes.
11 MR. VASAVADA: So this is Shilp again. I 12 think what Steve provided for the ACRS members is 13 considered an answer to the question by Member Hanlon 14 about -- sorry, Halnon, about the leak tightness.
15 Essentially, the ISG, and as Steve pointed out, there 16 is no assumption that it is being bottled up.
17 We are considering the fact that there can 18 be leakage. It's a comparison against the situation 19 where the downstream piping and the PCS is not 20 considered at all and how that factors into the staff 21 decision. Just wanted to make that point. Thanks.
22 MR. JONES: Right. And I was going to 23 continue that the main steam and attached systems are 24 there, therefore available to collect this leakage.
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34 There would be leakage potentially directly to the 1
main condenser through the turbine bypass, active 2
drain lines through an orifice, or drain lines where 3
the isolation valves leak. In addition, there's 4
potential for leakage through other paths to the 5
remainder of the power conversion system.
6 (Simultaneous speaking.)
7 MR. JONES: But I'll touch on that the 8
next slide.
9 MEMBER HALNON: Yeah, this is Greg Halnon.
10 Just so I understand, you're saying that the -- it was 11 assumed that the -- any rate of leakage that's 12 typically not measured which is other valves, other 13 steam traps, other areas in this main steam system 14 that maybe have leaked by that that is going to be a 15 small contribution and it was negligible to the 16 overall calcs. Is that essentially what you're 17 saying?
18 MR. JONES: I guess what I'm saying is 19 that we're only looking for maybe a reduction by a 20 factor of two or three of the release of the full 21 volume of the tech spec limit of leakage from these 22 values to be held up or delayed in such -- well, what 23 I should say, it's not a fraction of the amount. But 24 the effect of a delay, the holdup in these volumes, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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35 and potential for some deposition -- some limited 1
deposition on some surfaces, particularly if it gets 2
to the main condenser, would result in maybe a factor 3
of two or three reduction in what is actually 4
represented in the calculations. And that is 5
intended. One of the other presenters, John Parillo, 6
will be getting into exactly how that was used and 7
what specific assumptions and uncertainties he was 8
trying to address in his evaluation of those 9
consequences.
10 MEMBER HALNON: Okay. I'll take it all 11 in. And if I don't understand it at the end, I'll ask 12 the question again. But I think I'm getting it. So 13 continue on. Thank you.
14 MEMBER KIRCHNER: Greg, this is Walt. It 15 seems to me, Steve, with the cubic feet per minute 16 leakage assumption, what effectively is the pressure 17 in the power conversion system? With a condenser, is 18 the condenser just is it slightly above 19 atmospheric? In the case where the MSIVs shut, you 20 have some leakage as the tech spec's amount of 21 leakage. Then the pressure in the power conversion 22 system is what, pretty low, isn't it? I mean, so --
23 MR. JONES: Right, yes.
24 MEMBER KIRCHNER: -- where I'm going with 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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36 this, Greg, is that the leakage compared to normal 1
leakage at operating conditions would be much less if 2
the pressure of the system is significantly reduced 3
which I expect.
4 MR. JONES: Right. I should probably get 5
into that. The whole dose evaluation process occurs 6
at a delayed time and not at the instant of the 7
accident. But Reg Guide 1.183, I don't have the exact 8
timing in my mind. I believe it's two hours.
9 But the -- so there's a delayed release.
10 By that time, the containment is at accident pressure.
11 And that's what's acting against the MSIVs. You have 12 an assumption of one failed open MSIV. So the 13 remaining valve is leaking at its tech spec limit for 14 that steam line --
15 MEMBER KIRCHNER: Okay.
16 MR. JONES: -- which is on the order of a 17 few cubic feet per minute in these cases. And then 18 the other MSIV lines are also leaking at some reduced 19 rate.
20 MEMBER KIRCHNER: Okay.
21 MR. JONES: So that rate does not maintain 22 the main steam system or anything at any significant 23 pressure. It's very close to atmospheric --
24 MEMBER KIRCHNER: Okay.
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37 MR. JONES: -- by that time because you've 1
had the condensation cool down.
2 MEMBER HALNON: That helps. Thanks, Walt.
3 I guess my background is biasing me thinking, how do 4
I maintain a tech spec value given a leakage in one 5
cart given the fact I know I got leakage throughout in 6
the system that I'm crediting for some kind of holdup?
7 So I understand now that they're apples and oranges at 8
this point. So you can continue on. Appreciate it.
9 MR. DOZIER: This is Jerry Dozier. On 10 that -- and I'm only talking from an operations 11 standpoint. But you was asking about the pressure 12 downstream of the second MSIV.
13 If you look at what the leakage is and 14 compare the leakage as being requested, as one of the 15 team members indicated, that leakage is about what a 16 kitchen fan -- that the flow rate, which is in a cubic 17 feet per hour standpoint, is about the level of a 18 bathroom fan. So picture that bathroom fan kind of 19 going into that downstream piping. And so that's why 20 you would see such a low leakage. So it's low 21 pressure down there that's beyond a second MSIV.
22 MR. PARILLO: Jerry, this is John Parillo.
23 I just want to mention that a bathroom fan is usually 24 about one to two hundred cubic feet per minute, the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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38 allowable. It may seem an isolation valve limits that 1
we're talking about here are on the order of 200 2
standard cubic feet per hour, per hour. So I just 3
wanted to make that clarification.
4 MR. DOZIER: Thank you for that.
5 MR. VASAVADA: This is Shilp Vasavada from 6
the staff. I just wanted to also, I don't know, 7
clarify one item. I think we have been talking about 8
calcs and credit. And I think Steve mentioned factors 9
of two and four. So I just wanted to make it very 10 clear that as you will see later on, especially in 11 John's presentation, what this ISG and the work that 12 was done that I think was -- that was used by the 13 staff simply as a decision making input to achieve 14 confidence to reach a reasonable assurance finding.
15 It did not, in any way, shape, or form, 16 change the licensee's calculation. So no factor was 17 applied. No calculations were changed. No number was 18 put into a calculation, no quantitative credit was 19 taken. So I just wanted to make that fact clear.
20 Thanks.
21 MEMBER MARCH-LEUBA: Sorry. This is Jose.
22 You just confused me. Were calculations performed on 23 the holdup on what pressure? Or are you saying there 24 was no calculation, no deterministic number 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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39 calculated?
1 MR. VASAVADA: So -- go ahead, Steve.
2 MR. JONES: Okay. Yes, that's correct.
3 There is no deterministic evaluation of this holdup or 4
deposition. It's just considered as a factor in 5
addressing uncertainties with respect to other inputs 6
to those calculations. There are several points where 7
removal of the fission products is modeled by 8
different physical mechanisms at different points in 9
the system. And this is just a consideration in 10 resolving uncertainties with those values. And again, 11 John Parillo will be getting to that later in the 12 presentation. I did want to --
13 MEMBER MARCH-LEUBA: I would have --
14 sorry. Keep going.
15 (Simultaneous speaking.)
16 MR. JONES: So --
17 MEMBER MARCH-LEUBA: So this is Jose. I 18 honestly would have liked to see a deterministic 19 calculation because you get surprises when you start 20 modeling things. Clearly if this PCS piping is not on 21 the floor and is still intact, it's good for leakage.
22 I mean, I can't deny that.
23 But what the pressure is doing there as 24 you're losing cooling in the condenser and everything 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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40 is -- whatever atmosphere you had in the PCS before 1
the leak started is going to heat up as you lose 2
condenser cooling. And then you're adding this cubic 3
feet per hour, however much, you get surprises.
4 That's why we do the calculations with good codes and 5
figure out what the output is. I would have liked to 6
see the calculations. Thank you.
7 MR. JONES: I see. Okay. I did want to 8
touch back on issues that Dr. Rempe raised and Mike 9
Franovich discussed, I guess, with respect to the 10 testing and indication of the main steam isolation 11 valves and the issue with, I guess, balancing their 12 safety performance post-accident with the maintenance 13 and operational dose consequence issues with 14 maintaining these valves that are very high leak type 15 condition at low pressure. So as I mentioned that the 16 valves are intended for -- to seat with pressure at 17 very high normal operating pressure for the boiling 18 water reactors, near 1,000 psi.
19 During the accident, we're addressing 20 conditions closer to 40 to 60 psi inside the main 21 containment. And evaluating leakage, I guess the 22 operators can -- or the operating companies that 23 maintain these valves have provided a suitable basis 24 to demonstrate that leakage on the order of a few 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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41 hundred cubic feet per hour is commensurate with very 1
good operation of these valves. So we have very 2
little concern with the valves not operating properly 3
or not seating.
4 And we expect that this does not impact 5
the operation of the valves with respect to their 6
performance as a primary reactor coolant pressure 7
boundary valve or a containment isolation valve. And 8
again, we were not really modifying any operating 9
procedures or any inputs to the dose analysis with 10 this evaluation, just considering what the real world 11 impacts of the downstream power conversion system 12 would be on the dose consequences and how that could 13 be used to address uncertainty. All right. Our last 14 slide is Slide -- the last slide I'm discussing --
15 MEMBER REMPE: This is Joy. Then if 16 that's the answer to my question, maybe I didn't make 17 my question clear enough. And again, I'm not an 18 expert on operator response during a BWR event. But 19 if the -- again, valves sometimes just fail to close.
20 That's why they have reliability numbers.
21 And if the valve failed to close, how 22 would the operators detect the leakage that's 23 occurring versus the higher leakage rate allowed by 24 the revised tech spec? And are there any actions that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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42 they have to take? And if there's no actions they 1
take, then the answer to my question is it doesn't 2
matter. But typically, you detect whether a valve is 3
open or closed by temperature or radiation readings 4
usually is my understanding.
5 And are there any actions that suddenly 6
they don't detect that the thing failed to close 7
because it leaks more is my point. And are there any 8
actions that should be considered, because we're going 9
to use some more realistic risk-informed insights to 10 have a lower release to the environment. And I'm 11 wondering if there's other concurrent risk insights 12 that we're forgetting about. Does that make sense 13 what I'm trying to get to?
14 MR. JONES: Yes, but I'd just point out, 15 I guess, the MSIV leakage detection -- I mean, the 16 leakage detection systems and things in a boiling 17 water reactor are designed to detect ruptures in the 18 main steam system so that the high temperature would 19 be outside in the steam tunnel. And we wouldn't 20 expect any of that to result when these are operating 21 per the assumptions. I mean, this is a very stylistic 22 calculation design to test primary containment 23 performance. It's not really reflective of the most 24 likely outcome of -- or likely configuration that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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43 would exist following a core damage event. So I mean 1
2 MEMBER REMPE: But I mean, if it fails to 3
close, don't you really have a containment bypass?
4 It's open, right? And --
5 (Simultaneous speaking.)
6 MR. JONES: You would. And for that 7
reason, I mean, these valves are designed to be 8
redundant and very reliability in their closing. And 9
there is an assumption that one of them does not 10 close. In fact, does not close --
11 (Simultaneous speaking.)
12 CHAIR PETTI: Right. Isn't that part of 13 the calculation is to assume that one does not --
14 MEMBER KIRCHNER: Yeah, single failure.
15 CHAIR PETTI: And so I think I'm still 16 struggling understanding. There's leakage from all 17 the others. But then there's one that didn't close.
18 It seems like the one that didn't close is going to 19 dominate what's going on.
20 MR. JONES: Well, there's --
21 (Simultaneous speaking.)
22 MR. JONES: -- because there's two valves 23 in a series, the overall leakage is still limited.
24 It's just that line would have maybe higher pressure 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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44 acting on the one remaining valve. So you would see 1
-- there's an assumption that there's higher leakage 2
down one particular steam line than the other three.
3 But the other three still contribute some factor to 4
the dose consequence. And again, I think John Parillo 5
is the best one to address that when he gets --
6 MR. DOZIER: Dr. Vasavada wanted to 7
contribute, I think.
8 MR. JONES: Okay.
9 MR. VASAVADA: No, I think -- this is 10 Shilp from the staff -- Steve covered it. But I think 11 the point I was going to make is as Steve said. This 12 is a postulated scenario with certain stylized -- in 13 some cases in my personal opinion -- unphysical 14 assumptions about, like, for example, how long you 15 have choke flow, et cetera.
16 And those inputs remain unchanged by all 17 the work for the ISG. So the fact -- I mean, it's 18 already assumed that multiple redundant protection 19 systems have failed and you have achieved core damage.
20 And then there is a single failure of one of the MSIVs 21 that's already part of the analysis.
22 And then the other one leaks at a 23 particular rate which is being requested. And the 24 dose consequence analysis is considered in that rate.
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45 So just wanted to give that background. Nothing about 1
that is being changed by the ISG. Those postulated 2
assumptions remain as they are.
3 MEMBER KIRCHNER: Thank you. I think also 4
I would've answered Joy -- Joy, this is Walt. On the 5
highly low -- I'm not saying correctly. In the very 6
low probability of two isolation valves on the same 7
steam line failing to close, you would see pressure on 8
the secondary system. So I think the answer to your 9
question, how would you know that the valves didn't 10 seat, it would be a high pressure would build up in 11 the -- to whatever the containment pressure is in the 12 secondary system. So indirectly, you could check on 13 how well the valves seated by monitoring the pressure 14 in the power conversion system.
15 MEMBER REMPE: Okay. You're getting to my 16 point that, yes, there are ways they could detect 17 this. And again, there's this unusual situation 18 because we did design-basis calculations with a 19 stylized calculation. But then there are the real 20 world.
21 And in the real world, you're going to 22 allow higher leakage. The tech spec is going to be 23 changed. And so my point is, is that when you allow 24 that, it seems like somebody ought to be thinking 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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46 about the real world and a scenario that's not just a 1
design-basis calculation.
But should you be 2
considering about the instrumentation?
3 Now again, Vesna has been sending me 4
emails and she said, I don't think there's anything 5
the operators. There's no actions. And that would've 6
been also a good response to my question. But I'm not 7
hearing that anybody has thought about, is there 8
something that should be done or not?
9 And again, I'm just curious because I 10 think if we're going to do risk-informed stuff, we 11 ought to -- and a make a change with the tech spec, we 12 ought to think about what the operator should or 13 should not do. And there's no actions they take, oh, 14 well, I guess that's it. But if there are other 15 instrumentations that should be giving them insights, 16 then we ought to think about the difference between a 17 leaky valve versus an open valve. Maybe that ought to 18 be done. Does that kind of explain where I'm coming 19 from a bit more?
20 MR. JONES: Yes, I think I understand.
21 We're getting a lot more into the detail of how the 22 MSIVs operate. They are spring powered to close, and 23 they do have a pilot system that increases the 24 pressure to close the valves once they're actuated.
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47 And there would be an indication that the 1
valve is fully closed. So the operators would be 2
looking for that. If they did not fully close, they 3
could verify that the air was released or maybe taken 4
action to release air.
5 But other than the actual -- I'm sorry, an 6
indication of the valve position, there wouldn't be 7
anything for the operators to indicate that there's a 8
problem with the valve because, I mean, under normal 9
operating conditions, you have obviously full steam 10 flow going through these valves and it's very high 11 temperature. So where we're seeing the temperature 12 just gradually falling off in the system and as one of 13 the other members mentioned, there would be 14 potentially secondary system pressures holding up at 15 higher than expected values. But other than that, I 16 wouldn't expect to see anything from excessive leakage 17 beyond the --
18 MEMBER REMPE: Is there an operator action 19 that would be done? Or would they just say, hey, the 20 thing didn't close? And they'd see it more slowly 21 because they have to figure out whether there's 22 pressure, there's increased leakage that they're 23 allowing because it -- from a much lower leakage. And 24 I just am curious about it. And did somebody think 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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48 about this when they were saying, yeah, we're going to 1
let them increase the tech spec?
2 MR. DOZIER: Dr. Rempe, what I could 3
propose, okay, I was an STA at Grand Gulf, okay? And 4
if you visualize this stylized accident that is done 5
basically for calculation purposes, you would have --
6 you basically have core damage here -- I mean, an 7
assumed core damage. You have an assumed drywell 8
pressure at that maximum level.
9 I mean, at the point of especially the 10 initial leakage or whatever, the operator is focused 11 on getting water in the core. They're focused on 12 protecting other containment, things like that. So 13 it's hard. It's very difficult to put this into a 14 realistic situation. But we have done that with some 15 of our risk studies, with SOARCA, and also the 16 original report that was one on this to talk about the 17 releases to the environment.
18 MR. JONES: I guess what I can say is that 19 we've considered the effect of the increased allowable 20 leakage on valve operation and we see no effect. With 21 respect to operator action, it would be driven again 22 by position indication on these valves. And that 23 would be unaffected by this action as well. If the 24 valve does not close, I'm certain there are actions in 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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49 the EOPs, although I can't confirm right now, to 1
address that condition.
2 MEMBER REMPE: Yeah, if the EOPs take care 3
of it, those are the kind of things I wanted to hear.
4 Yeah, we thought about it and the increased leakage.
5 And it doesn't matter or something, that it's been 6
taken care of in the EOPs. And I just didn't see it.
7 But I may not have seen all the information that's 8
available. I only saw one document from FitzPatrick.
9 MR. JONES: Right. Okay.
10 MR. VASAVADA: This is Shilp from the 11 staff. I just also wanted to point out that all of 12 what Steve said and the EOPs, et cetera, that is true 13 for MSIV leakage, increased LARs and reviews and 14 decisions whether the ISG exists or not. So the 15 question about valve closure and indications, the ISG 16 doesn't either change it, improve it, or reduce it.
17 It's the same. It does not change anything from 18 whether the ISG is used or not.
19 MEMBER REMPE: That's also true. I was 20 more concerned when I was seeing tech specs change for 21 the actual plants. And I only, again, saw one of 22 them. But it's a related topic, and that's why I 23 wanted to bring it up because maybe Daiichi should 24 mention that you are changing a tech spec.
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50 I don't know. Maybe it's a separate 1
topic. And I did start off my discussion that this is 2
a bit off topic. But I was curious about what was 3
going on.
4 MR. JONES: Okay. I guess we can move on 5
to Slide 17, just again discussing a realistic 6
transport pathway. I did want to clarify a 7
distinction from the BWR topical report. In this --
8 for this ISG, the staff does not assume any operator 9
action to align a specific path to direct main steam 10 isolation valve leakage to a particular location like 11 the main condenser.
12 Drain lines and turbine bypass lines lead 13 directly to the main condenser. And if they leak, 14 that would be one way that any leakage release would 15 get to the main condenser. Other leakage paths 16 primarily through the stop and governor valves on the 17 high pressure turbine would go to the high pressure 18 turbine area.
19 There is definitely less holdup and 20 deposition in the main condenser. But there's still 21 a volume there. And the additional -- those valves 22 are designed again to be fairly reliable and leak 23 tight.
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51 there would be an easy flow path even to the steam 1
chest and the -- of the main turbine. But if they did 2
get there, then there would be a release path via the 3
high resistance path through the shaft seals -- the 4
main turbine shaft seals since there would not be 5
steam pressure to provide the ceiling steam. There 6
would still be kind of a torturous path for the 7
release to follow to get to the turbine building at 8
that point.
9 But I just want to point out that we're 10 not necessarily considering complete holdup or that 11 all the flow gets to the main condenser. But there 12 are places that would delay and otherwise reduce the 13 dose consequences from the event when realistically 14 considering the transport pathways through the power 15 converting system. That's all I have.
16 (Simultaneous speaking.)
17 MR. VASAVADA: Yeah, this is Shilp. I 18 just wanted to also point out to what Steve said and 19 support that. They're not considering, like, bottling 20 up that if you are to compare that -- again, this is 21 no credit was given. This is a decision making input.
22 If we are to compare that with the actual 23 quantitative credit for the condenser in Reg Guide, 24 the disparity there because the quantitative credit in 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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52 the condenser does not mean that the holdup -- I mean, 1
the deficient part of the water in the condenser.
2 There is a defined, you can say, leakage rate from the 3
condenser. So the condenser is considered, quote, 4
open, end quote. So the disparity there to restart as 5
if the condenser is leak tight if quantitative credit 6
using Reg Guide is used.
7 MR. JONES: Okay. And with that, that was 8
the end of my section with this presentation. And I'd 9
like to hand it over to Dr. Vasavada to go over the 10 seismic considerations.
11 CHAIR PETTI: Yeah, so maybe this is a 12 good point. We usually take a break around 9:00 13 o'clock before we get into the seismic stuff. Is that 14 okay with you guys?
15 And we take about a 15-minute break and 16 then reconvene at the top of the hour to start the 17 seismic.
18 (Whereupon, the above-entitled matter went 19 off the record at 10:46 a.m. and resumed at 11:00 20 a.m.)
21 CHAIR PETTI: Okay. I have top of the 22 hour2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />, so let's reconvene and start with the seismic 23 slides. Thank you.
24 MR. VASAVADA: Okay. Thank you. This is 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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53 Shilp Vasavada. I hope you can hear me.
1 CHAIR PETTI: Yes, we can.
2 MR. VASAVADA: I'll start. Good morning 3
to everyone. As I said, my name is Shilp Vasavada.
4 I'm in the Division of Risk Assessment in NRR, and 5
I'll be discussing the seismic capacity evaluation for 6
the SSCs in the power conversion system or PCS that is 7
documented in the technical assessment for the ISG.
8 As many of you may know, the SSCs in the 9
PCS do not need to be seismically qualified primarily 10 because they are not safety related. Therefore, the 11 context for the seismic capacity evaluation, if you 12 think about the risk triplet for the ISG is to 13 understand the risk of gross failure of the SSCs in 14 the PCS, especially the safe shutdown earthquake of 15 the plants. The intent is not to, again, provide a 16 factor for reduction of the dose.
17 It is to see whether the SSCs in the PCS 18 have a high confidence of surviving the safe shutdown 19 earthquake in a realistic scenario or considering 20 realism, provide holdup volume that the staff can use 21 that's realism in its decision making. It will --
22 overcoming any challenges with uncertainties in other 23 parameters. Before I provide an overview of the 24 evaluation, I'll just go over a primer on some seismic 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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54 capacity-related terms that you will be hearing.
1 They may be new to you. But they are 2
meant to help with common understanding and the 3
communication. I'm on Slide 18, and the terms over 4
here, I'll give a caveat. They're not textbook 5
definitions, please don't hold me to that.
6 Firstly, fragility, it's the conditional 7
probability of failure of an SSC as a function of 8
seismic acceleration. And one of the common ways of 9
expressing fragility is what's known as median 10 fragility, also known as A sub m. This is a seismic 11 acceleration at which there is a 50 percent 12 probability of failure.
13 And along with A sub m, there are two 14 uncertainty parameters, beta r and beta u as they are 15 called, to which together define the median fragility 16 of an SSC. These uncertainty parameters characterize 17 the, again, uncertainty in the median fragility or the 18 fragility of an SSC. The seismic acceleration is the 19 measure of the strength of an earthquake.
20 It is usually expressed in terms of 21 multiples of the gravitational acceleration. So 22 you'll hear terms like 0.1g, 0.2g where g is the 23 gravitational acceleration.
And peak ground 24 acceleration is a commonly used term -- or commonly 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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55 used acceleration level for seismic analysis.
1 It corresponds to the acceleration of a 2
100 Hertz oscillator. A lot of times, a lot of 3
analyses are so to say anchored to the peak ground 4
acceleration to provide a common language for 5
comparison and use. Next slide, please. So I'm on 6
Slide 19.
7 And this slide, basically, the figure over 8
here brings all the terms that we discussed in the 9
previous slide together and pictorially. You can see 10 the curves which are the cumulative fragility curves, 11 the 95th percentile, the 50th percentile, and the 5th 12 percentile. As previously explained, the fragility is 13 a function of the seismic acceleration and peak ground 14 acceleration in this case which is the commonly used 15 acceleration value.
16 In this example, so the median fragility 17 is 0.8g -- 0.87g. So you have a 50 percent 18 probability of failure of this example, SSC at that 19 particular acceleration. One concept that I wanted to 20 also share is that a higher median fragility value 21 implies a more robust or a higher seismic capacity 22 SSC.
23 The reason being that a higher median 24 fragility value shifts all those curves to the right.
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56 So you have -- for the same seismic acceleration, 1
you'll have a lower failure probability. Next slide, 2
please. So I'm on Slide 20.
3 To evaluate the seismic capacity of the 4
PCS components, we looked at several diverse sources 5
of information that compiled fragility data to get an 6
idea of where the fragility is of different components 7
that may exist in the PCS line. We also looked at 8
insights from both earthquake walkdowns. And we 9
performed representative risk calculations to estimate 10 the risk of gross failure of the SSCs in the PCS.
11 For the fragility data, we looked at the 12 various NUREGs and industry reports, including EPRI 13 reports as well as information we recently submitted, 14 a seismic probabilistic risk assessments or PRAs, that 15 were submitted in response to the Agency's post-16 Fukushima's actions. As many of you may know, seismic 17 PRAs usually don't model PCS components or balance of 18 plans components as they are called. However, the 19 seismic PRAs do carry information related to the 20 fragility of several other components which exist in 21 the PCS like welded and bolted piping, valves.
22 And they also provide information about 23 the extent of seismic risk accelerations up to the 24 plant safe shutdown earthquake. All of that is 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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57 relevant to this evaluation. In terms -- Jerry, can 1
you go to the next? I'm still on Slide 19.
2 We also reviewed the post-earthquake 3
walkdown experience for North Anna in the U.S. and 4
Kashiwazaki-Kariwa in Japan and Onagawa also in Japan 5
following the Great Tohoku Earthquake of 2011. All 6
these plants experienced earthquakes that exceeded 7
their respective safe shutdown earthquakes and 8
equivalent in Japan. And we focused our observations 9
over there for the PCS components and the impacts --
10 post-earthquake impacts that were observed or not on 11 those components.
12 As I think in response to a question, I'll 13 just mention it over here. And I can additional 14 detail if that's necessary. The ISG nearly mentions 15 that the purpose of the reviewing the walkdowns was 16 not to draw one is to one comparisons.
17 We recognize it's plant-specific, it's 18 design-specific, and location-specific and also maybe 19 operating practices-specific. The reason for doing 20 the evaluation of the post-earthquake walkdowns was to 21 identify insights related to the behavior of PCS 22 components in general: were there any gross failures 23 that were observed, were there any issues that we need 24 to consider in our evaluation, and to take it in 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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58 conjunction with the data as a body of evidence which 1
then was used to determine and lower bound median 2
frigidity value which we believe encompasses the 3
seismic failure modes for the SSCs in the PCS and then 4
use the representative risk to determine what would be 5
the representative risk of gross failure of the SSCs 6
in the PCS. Next slide, please. I'm on Slide 21.
7 So the insights that we gathered from all 8
of that evaluation was that welded piping, bolted 9
piping, as well as valves have high median fragility 10 values which as we talked about implies that they have 11 high seismic capacity. In addition, the main 12 condenser is usually -- I mean, as all of you may know 13
-- a huge structure which is bolted to the floor of 14 the turbine building. It's usually a seismic Category 15 II structure, so the anchorage is designed to avoid 16 failure at design-basis loads to prevent what's called 17 a Seismic II or I interaction.
18 In addition, all the post-earthquake 19 walkdowns of plants in the U.S. and Japan demonstrated 20 that the PCS components have high seismic capacity.
21 No gross failures or major issues were identified for 22 even the nonsafety-related PCS components at any of 23 those post-earthquake walkdowns. And finally, the 24 seismic PRAs demonstrated that the seismic risk from 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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59 acceleration at accelerations below -- at and below 1
plant safe shutdown earthquake is small.
2 The contribution to the overall plant risk 3
-- seismic risk from those acceleration levels is a 4
very small fraction. Next slide, please. So based on 5
all of that, the information, we determined a lower 6
bound median fragility parameters for the use in our 7
evaluation. These parameters as displayed over here 8
are the median fragility value of 0.4g and the beta r 9
and beta u of 0.22.
10 They are based on the fragility of an 11 expansion joint connecting the circulating water 12 piping to the condenser. And based on, again, the 13 evaluation and the survey of data and the walkdown 14 information, we believe that it encompasses all the 15 failure modes for the relevant SSCs in the PCS piping, 16 et cetera, and valves. And it supports the low 17 likelihood that the gross failure of the SSCs in the 18 PCS would not occur.
19 For context, as I mentioned, the --- but 20 for parity, when the actual quantitative credit for 21 holdup in the condenser is taken, the condenser is 22 considered code open with a specified leakage rate 23 from the condenser. So using this lower bound is also 24 actually conservative because it is essentially 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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60 treating the entirety of the PCS at a very lower 1
fragility to see what would be the failure and release 2
if this fragility were to be exceeded as compared to 3
just considering a small level of leakage which is 4
anyways allowed or considered when the credit is taken 5
-- quantitative credit is taken. Next slide, please.
6 So I'm on Slide 23.
7 Using that lower bound fragility value, 8
what we did was we, it was called a range of seismic 9
hazard curves with that condition failure probability 10 from the median fragility values to determine what is 11 the -- you can say frequency of release due to the 12 gross failure of the SSCs in the PCS. And we used a 13 range of recently developed seismic hazard curves 14 which are developed in response to the Agency's post-15 Fukushima actions. And our results -- estimates 16 showed that the risk is low from -- the risk of 17 release from a gross failure of the SSCs in the PCS is 18 low.
19 And even if you consider the entire 20 seismic hazard curve, if you were to consider only up 21 to the safe shutdown earthquake as is necessary for 22 the purposes of this -- I mean, this entire MSIV dose 23 calculation, the risk would be even lower. So next 24 slide, please. So Slide 24 talks about the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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61 uncertainty, how we considered the uncertainty for the 1
seismic capacity evaluation. In terms of the 2
uncertainty, the --- in the selected parameter, that, 3
I mentioned, is already included explicitly to the 4
beta r and beta u parameters and used in the 5
calculation of the representative risk estimates. In 6
order to address the conservatism in the selection of 7
the median fragility parameter, that is, is 0.4 8
sufficiently lower bound? Or it should be 0.3 or 9
should be 0.5?
10 We looked at the conservatisms that 11 already exist brought in our evaluation as well as in 12 the overall MSIV calculation to address that 13 uncertainty. So we are using a lower bound region 14 fragility as we mentioned to kind of encompass all 15 potential failure modes in spite of the fact that 16 several of the SSCs show much, much higher median 17 fragility values. And it is not necessary to have a 18 leak tight approach for the decision making that the 19 ISG provides.
20 As we have noted, there'll be low pressure 21 conditions because of the postulated scenario. So the 22 piping and the SSC in the PCS are designed for high 23 pressure and high temperature. So the margin that is 24 in that design is not explicitly being accounted for, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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62 especially with the choice of the lower bound 1
fragility parameters.
2 We are considering the safe shutdown 3
earthquake occurring concurrent with a postulated 4
accident that results in complete core damage. So 5
that's an additional level of conservatism. And as we 6
have said multiple times, the important assumptions, 7
parameters, guidance, boundary conditions that go into 8
the actual dose calculation remain unchanged by this 9
ISG. So that's additional conservatisms in there 10 which we have not changed or taken advantage of.
11 MEMBER KIRCHNER: Shilp, this is Walt 12 Kirchner. On a previous slide, you identified the 13 weak link in your analyses -- seismic analyses as the 14 expansion joint for circulating water to the main 15 condenser. But that's not a leak path unless you have 16 massive tube rupture in the condenser. So was there 17
-- what was the second most fragile component in the 18 PCS systems that actually are forming the holdup 19 volume?
20 MR. VASAVADA: All right. So we didn't --
21 or at least I didn't go line by line through all that 22 exists in the PCS in order to determine the next --
23 sorry, Steve, did you want to say something?
24 MR. JONES: Yes, sorry to interrupt. But 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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63 I mean, just to clarify, the expansion joint is the 1
boot between the bottom of the low pressure turbine 2
and the condenser, not -- I mean --
3 MEMBER KIRCHNER: And it wasn't explained 4
5 MR. JONES: -- there's still an expansion 6
7 MEMBER KIRCHNER: And it wasn't explained 8
9 MR. JONES: -- joint there.
10 MEMBER KIRCHNER: -- correctly in the 11 viewgraph.
12 MR. JONES: Okay.
13 MR. VASAVADA: Sorry about that, yeah.
14 And again, to --
15 (Simultaneous speaking.)
16 MEMBER KIRCHNER: Okay.
17 MR. VASAVADA: -- that question, if --
18 MEMBER KIRCHNER: That's part of a leak 19 path then? Okay. Thank you. That answers my 20 question.
21 MR. VASAVADA: Okay. Thank you. All 22 right. So that was basically an overview -- I'm still 23 on Slide 24 just closing up -- overview of the seismic 24 capacity evaluation that is included in the technical 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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64 assessment. And in summary, in the context of the 1
ISG, the seismic capacity evaluation supported the 2
case that the SSCs in the PCS have a high seismic 3
capacity. And the risk of release, because of the 4
gross failure, especially at the safe shutdown 5
earthquake level, is low.
6 And taken together with the other elements 7
of the assessment that were described by Steve and 8
Jerry, it supports the insights and the recommendation 9
that the ISG provides to the staff to consider this 10 realism in their decision making if they are 11 challenged because of any uncertainty in input 12 parameters in the rest of the dose calculation.
13 Again, I'd like to reiterate the seismic capacity 14 evaluation or the ISG evaluation does not change the 15 dose calculations. They remain the same.
16 As submitted by the licensee, the margin 17 to the acceptance guidelines remains the same. It's 18 just a decision making input to provide staff the 19 confidence to reach reasonable assurance if there are 20 challenges with uncertainty in a parameter or the 21 other. Next slide, please. I'm on Slide 25.
22 And I wanted to, again, put this ISG in 23 the context -- a different holistic context of the 24 entirety of the MSIV evaluation to kind of represent 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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65 the fact that it's a small sliver in the entirety if 1
you consider the whole dose calculation approach. So 2
first of all, the licensee's calculations will start 3
with the assumption of core damage arising from a 4
postulated scenario with failure of multiple redundant 5
protection systems. In addition to that, there is a 6
single failure of the inboard MSIV which is assumed.
7 In addition to
- that, there are 8
conservatisms in the analysis -- in the guidance which 9
include acceptable assumptions and parameters. I'll 10 give an example that, for example, choked flow is 11 assumed for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> so that the leakage flow can be 12 at the tech spec limit for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as part of the 13 analysis. That conservatism remains in the guidance.
14 It remains unchanged.
15 As I mentioned, we assume that a safe 16 shutdown earthquake concurrent with this postulated 17 scenario. And we use a lower bound median fragility 18 value to kind of see what is the risk of gross 19 failure. So in the context of the entirety of the 20 evaluation, this ISG forms what I would call a small 21 sliver of realism in a universe of conservatism.
22 And again, the purpose was not to change 23 the dose calculations. The purpose was to provide the 24 staff with additional confidence to reach the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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66 reasonable assurance if there was talk about whether 1
X acceptable value is okay for a particular parameter 2
or Y is okay. Next slide, please. I'm on Slide 26 3
now.
4 So before I pass it on to John for more 5
details, I wanted to provide a kind of comparison 6
between what the ISG intends to do and what the 7
proposed or planned revision to Reg Guide 1.183 is 8
intended to achieve. And this slide attempts to 9
clearly differentiate between the two. The ISG 10 obviously is directed to the staff to support their 11 decision making whereas the Reg Guide will be directed 12 to the licensees and provides acceptable means of 13 showing compliance with regulations.
14 The ISG, again, as I've been repeating it 15 again and again, provides staff additional confidence 16 to reach its reasonable assurance finding. It is not 17 the only reason that the staff would reach the 18 finding. It is providing additional confidence.
19 The Reg Guide provides acceptable methods, 20 including it would provide the method and the guidance 21 for getting quantitative credit for holdup in the main 22 condenser which the ISG does not provide any 23 quantitative credit. So the ISG, because of that 24 reason, does not change the dose calculations of the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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67 analysis of record that the licensee has submitted and 1
that the staff uses for its reasonable assurance 2
finding. The Reg Guide revision, if the licensee were 3
to take -- follow that guidance for quantitative 4
credit, does change the dose calculations.
5 It does introduce if -- I believe the term 6
is decontamination factor which does reduce the dose.
7 The ISG does not do that. So for that purpose, the 8
ISG does not need information from the licensee. It's 9
a decision making tool for the staff. It is expected 10 that the revision to Reg Guide 1.183 for quantitative 11 credit in the condenser would be requesting docketed 12 information from the licensee for that purpose. I see 13 Member Corradini's hand up for a question.
14 MR. CORRADINI: Just for clarification, so 15 the licensing basis calculation -- dose calculation 16 would not be -- would be changed. But this is an 17 internal document the staff would use for any 18 subsequent LAR or similar LARs? Am I -- I'm still not 19 clear about the use of the ISG. That's where my 20 question is coming from.
21 MR. VASAVADA: Sure. So I'll give, you 22 can say, an answer. And it will be maybe fleshed out 23 in more detail by John as he goes through the details.
24 I'll give -- let's start with an example.
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68 MR. DOZIER: Mike Franovich has his hand 1
up.
2 MR. VASAVADA: Okay.
3 MR. FRANOVICH: I don't think I did, 4
Jerry, but --
5 MR. DOZIER: Oh, I'm sorry. Another 6
Michael, I think, had their hand up. I'm sorry. Or 7
Dr. Kirchner?
8 MEMBER KIRCHNER: Yes, thank you. Just to 9
be precise here, I'm presume that the using in the 10 spirit a holistic approach provides guidance for 11 quantitative credit for holdup in the power conversion 12 system, not just the main condenser, albeit the main 13 condenser is probably the largest volume. The turbine 14 is probably the second largest volume. The piping, I 15 don't know where that all -- how much volume that adds 16 up to. But it would be for the full PCS, right?
17 MR. VASAVADA: So I'll address that one 18 first and then go back to Member Corradini's question.
19 In that context of Reg Guide 1.183 for quantitative 20 credit, it is the condenser. It is not the PCS 21 because over there, the way it works is that a pathway 22 to the condenser has to be opened up.
23 And that pathway is given credit with, you 24 can say, numerical decontamination factor which 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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69 decreases the dose because of the decay in the 1
condenser. So it was just the condenser. And 2
obviously, yeah, the lines that need to be opened up 3
to -- for example, the drain lines that need to be 4
opened up to get to the condenser. Does that help?
5 MEMBER KIRCHNER: Yeah. Well, unless the 6
-- well, I'm trying to think through a BWR response to 7
an accident. I guess the main turbine stop valve 8
probably closes so that -- and doesn't have -- usually 9
have a direct path into the turbine itself which is a 10 significant volume, although the leakage paths from 11 turbine are minimal. But okay.
12 MR. VASAVADA: So that is the --
13 MEMBER KIRCHNER: I assume you would just 14 let the applicant assess his or her particular design 15 and the line -- what would be the configuration of the 16 PCS under the accident condition that's assumed?
17 MR. VASAVADA: That's correct. And what 18 you just said about the configuration you're thinking 19 about is the thought process we used for the ISG. But 20 it does not provide quantitative credit. It is a 21 realistic kind of decision making input using 22 insights, operation and seismic insights, to support 23 the staff that in reality this is what will happen.
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70 assumptions, you use this to get confidence in your 1
decision that using accepted assumptions that doses 2
are just calculated by the licensee would likely be 3
lower if you were to think about it realistically.
4 And you can still go out and make your conclusions.
5 For the context of taking quantitative credit by the 6
licensee to actually make a numerical change in their 7
dose calculations, the guidance would be in 1.183.
8 And that just talks about opening a path 9
to the condenser and credit for the condenser. And 10 that would be a licensee's decision if they want to 11 take credit or not. So I'll go back to Member 12 Corradini's question.
13 MR. CORRADINI: You know what? I don't 14 think you have to. The way you answered Walt helped 15 me out. So I'm fine. Thank you.
16 MR. VASAVADA: Okay, thanks. And I'll 17 continue on this slide. Again, to repeat, the ISG 18 does not change the licensee's responsibilities to 19 show compliance or to -- it does not change the 20 acceptable methods to demonstrate compliance for the 21 guidance. I think that ends my portion of the 22 presentation. I'll turn it over to John Parillo to 23 discuss how the content of the ISG was actually used 24 to support the staff's reviews of recent LARs. John?
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71 MR. PARILLO: Thank you, Shilp. This is 1
John Parillo speaking. I am a member of the Radiation 2
Protection and Consequence Branch in the Division of 3
Risk Assessment. I was a contributor to the review of 4
the James A. FitzPatrick license amendment requesting 5
an increase in their allowable main steam isolation 6
valve leakage limits.
7 The FitzPatrick plan had the lowest MSIV 8
leakage limits in the USBWR fleet and requested 9
leakage limits more in line with the rest of the 10 operating fleet. Slide 27 includes excerpts from 11 Section 50.67, accident source term, and highlights 12 that the rule states, the NRC may issue the amendment 13 only if the applicant's analysis demonstrates with 14 reasonable assurance that specific dose acceptance 15 criteria will be met. Slide 28. Slide 28 contains 16 information pertaining to challenges that the NRC 17 staff has encountered when reviewing applications, 18 requesting increases in main steam isolation valve 19 leakage limits.
20 Regulatory Guide 1.183 does not contain an 21 aerosol deposition model suitable for the evaluation 22 of the dose consequences from main steam isolation 23 valve leakage. In addition, the staff has concerns 24 with the settling velocities used and researches 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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72 accident evaluation branch AEB-98-03. Due to the lack 1
of a main steam line aerosol deposition model in Reg 2
Guide 1.183 and issues with some of the assumptions in 3
AEB-98-03, the NRC staff has issued many requests for 4
additional information, questioning the aerosol 5
deposition models submitted for NRC review.
6 Many licensees have incorporated concepts 7
from AEB-98-03 with additional conservatisms in their 8
licensing basis. Slide 29. The 2006 regulatory 9
information summary included general concepts that 10 licensees should consider when modeling main steam 11 line deposition. However, the RIS did not provide an 12 acceptable model or a reference to one that licensees 13 could follow to provide some level of confidence in 14 gaining staff acceptable of their license amendment 15 requests. Slide 30.
16 Shortly after publishing of AEB-98-03, the 17 staff identified concerns with the methodology used in 18 this document. In spite of these concerns, the RIS 19 stated that it is acceptable for licensees to continue 20 to reference AEB-98-03 but that their deposition model 21 needs to reflect individual plant characteristics. As 22 evidenced by the continuing numerous requests for 23 additional information pertaining to main steam line 24 deposition modeling, the RIS did not resolve the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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73 ongoing issues encountered when licensees submitted 1
license amendment requests for increasing MSIV leakage 2
limits. In 2009, the --
3 CHAIR PETTI: This is Dave. I have a 4
question, just a clarification. As I recall reading 5
in FitzPatrick, is it the aerosol modeling in the 6
steam line or in the drywell or both that have been 7
the concern?
8 MR. PARILLO: Well, primarily in the main 9
steam line. And specifically, we will discuss the --
10 there's a particular uncertainty we had in trying to 11 evaluate the combination of the aerosol deposition in 12 the drywell due to drywell sprays and then that 13 subsequent deposition in the main steam line which was 14 the primary uncertainty in this review. And in fact, 15 it was the primary uncertainty in all of the four 16 recent MSIV leakage license amendment requests.
17 CHAIR PETTI: Okay. Thank you.
18 MR. PARILLO: Thank you. Let's see.
19 Where was I? In 2009, the NRC published Draft Guide 20 DG-1199 for public comment as a proposed revision to 21 Reg Guide 1.183. Draft Guide 1199 provided a model 22 for assessing MSIV leakage. However, the approach 23 described in this Draft Guide provided very 24 challenging for licensees and has never been 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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74 implemented in a license amendment request.
1 The proposed model in DG-1199 did not 2
credit safety-related equipment to distribute the 3
deterministic source term for the first two hours of 4
the evaluation. This assumption has been determined 5
to be inappropriate for design-basis assessments as 6
described in the case file for differing professional 7
opinion, DPO 2020-2, and is being eliminated in the 8
proposed revision to Reg Guide 1.183. Slide 31.
9 Slide 31 summarizes a
significant uncertainty 10 encountered in the review of the recent MSIV leakage 11 license amendment request.
12 The interaction between aerosol removal by 13 drywell sprays and the subsequent aerosol removal due 14 to main steam line deposition as modeled by the 15 licensees was questioned. Sensitive analyses were 16 submitted that indicated that if the power conversion 17 system is assumed to be intact providing a pathway to 18 the condenser, the dose reduction would be 19 substantial. The effectiveness of an intact power 20 conversion system providing a pathway to the condenser 21 is acknowledged by the NRC staff as evidenced by 22 assumptions in Appendix C to Reg Guide 1.183 for the 23 evaluation of the boiling water reactor rod drop 24 accident.
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75 Due to model limitations and for 1
additional conservatism, licensees only credit a 2
deposition in two of the four main steam lines. This 3
conservatism alone accounted for an approximate 30 4
percent increase in the calculated dose consequences.
5 And in addition, licensees did not credit mixing 6
between the drywell and the wetwell air space for the 7
first two hours of the accident. This assumption has 8
also been determined to be inappropriate for design-9 basis assessments as described in the previously 10 mentioned DPO case file. Slide 32.
11 Slide 32 describes the licensees' accident 12 analyses of record and how the NRC staff use the 13 insights described in the ISG to reach its conclusion 14 of reasonable assurance. As stated, the key points 15 are that, one, the licensees' sensitivity analyses are 16 not part of their licensing basis, two, a pathway to 17 the condenser was not credited in the analyses of 18 record, three, the licensees provided analyses which 19 met the acceptance criteria in 10 CFR 50.67, and most 20 important for this discussion is that the staff's 21 determination of reasonable assurance was supported by 22 the recognition that there is a high probability that 23 doses will be significantly lower than those estimated 24 by the licensees using deterministic methods that do 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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76 not credit holdup and retention of the main steam 1
isolation valve leakage within the power conversion 2
system.
3 This essential concept explains the 4
relationship between the review of the four license 5
amendment requests and the concepts presented in the 6
ISG. I'm looking to see if there are any questions.
7 Oh, well. No hands raised. So now Jerry will review 8
the key takeaways from today's presentation.
9 MR. DOZIER: Okay. So as we've 10 demonstrated
- today, the ISG will result in 11 consideration of large holdup volume in future MSIV 12 leakage LARs. It offset some of the certainty and 13 input parameters for deterministic calculations, 14 supports the reasonable assurance findings during 15 reviews, and is only applicable if quantitative credit 16 is not included in the licensee's calculations. As 17 we've emphasized, the ISG does not change the 18 licensee's responsibility to demonstrate compliance 19 with 2 CFR 50.67.
20 Acceptable methods for demonstrating 21 compliance remain unchanged. ISG is expected to be 22 transitioned to the standard review plan. And we've 23 got more work to do because formal condenser holdup 24 credit for licensees is being considered in the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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77 revision to Reg Guide 1.183. That concludes our 1
presentation.
2 CHAIR PETTI: So question, it's being 3
considered or it will be incorporated?
4 MR. VASAVADA: This is Shilp. If I can 5
answer, I think -- this is Shilp Vasavada from the 6
staff. First of all, I mean, being considered may not 7
be the right words because it's already there in 8
Revision 0 of Reg Guide 1.183. What I think we are 9
trying to say over here is the insights that we gained 10 from the development of the technical assessment for 11 the ISG will be leveraged to see how we can streamline 12 the credit -- getting the credit in the revision to 13 1.183.
14 CHAIR PETTI: Okay. Thank you.
15 MR. DOZIER: And in other words, it might 16 change it because realize that if you look at that old 17 topical report, it actually goes to looking at fossil 18 plans. With this new approach that we're looking at, 19 we're looking at a wide range of more modern 20 information, for example, the Fukushima operating 21 experience, all these lessons learned that we've 22 gotten from Fukushima. So we're looking at in the 23 update, maybe we could use these insights to change, 24 I want to say, our archaic way that we had done 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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78 before.
1 CHAIR PETTI: Okay. Thank you.
2 MEMBER REMPE: Dave, this is Joy. Can I 3
ask a question again?
4 (Simultaneous speaking.)
5 MEMBER REMPE: I just want to confirm what 6
I heard from Shilp earlier. Shilp, did you tell me 7
that all the BWRs do have positive indication of 8
closure for the MSIVs?
9 MR. VASAVADA: I think -- I believe it was 10 maybe Steve. But Steve, can you --
11 MR. JONES: Yes, this is Steve. The 12 indication would be from the stem position of MSIVs.
13 But in that sense, there's indication of closure.
14 MEMBER REMPE:
So my question is 15 irrelevant because it would not -- you can immediately 16 detect closure. So the fact that you have higher 17 leakage does not matter. Is that the answer to my 18 question then?
19 MR. JONES: Well, I think the higher 20 leakage is really independent. We're talking about 21 very small leakage still. And the indication of valve 22 closure is really just greater than 90 percent closed.
23 And you have the valve being spring actuated would 24 drive it to full closure. So --
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79 MEMBER REMPE: Okay.
1 MR. JONES: -- in that sense, I don't see 2
a lot of follow-up. If you get the indication of 3
closure, there would not be a need for operator 4
action.
5 MEMBER REMPE: So there would not be any 6
change? Okay. I just wanted to make sure I fully 7
understood it because it is just something that was 8
concerning me. So thank you.
9 MR. JONES: Okay. Thank you.
10 MEMBER HALNON: This is Greg. I get a 11 little bit confused. First of all, Joy, there's other 12 indications, steam tunnel temperatures and other 13 things that the operators would expect to see upon 14 closure versus not. So it's not just based on 15 indication. But back on Slide 26, we talk about that 16 the licensee from Reg Guide 1.183 provides guidance 17 for quantitative credit for holdup in main condenser.
18 And then this last slide was that there's no credit 19 for holdup and condenser.
20 And I guess I lost the bubble here 21 somewhere. What are licensees taking credit for in 22 their deterministic calculation, just the general PCS 23 deposition rates? Or was it always predetermined that 24 they could just redo their -- take out some 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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80 conservatisms or add some depositions such that they 1
could get a higher leakage rate anyway without any 2
other conservatisms being taken off?
3 I kind of just lost that last statement 4
that said you don't take credit for the holdup. I 5
think I lost the overall concept. So help me with 6
that. Just reconcile the two statements, the one on 7
the last slide and the one on Slide 26.
8 MR. VASAVADA: John, do you want to take 9
that? Or do you want me to start?
10 MR. PARILLO: Yeah. If I understood your 11 question, we have a bit of a discontinuity in the 12 existing Reg Guide. Appendix C which is for the 13 control rod drop accident for boiling water reactors, 14 that provides assumptions that licensees use which 15 implicitly assumes that a pathway to the condenser and 16 that allows for a certain deposition in the condenser.
17 But more importantly, it allows you to release the 18 effluent one percent per day.
19 Now that accident is only evaluated for 24 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. But that, for a long-term release, would be 21 very, very significant reduction. But for Appendix A 22 which deals with -- well, currently, it's referred to 23 as the loss of coolant accident. But we prefer to use 24 the term, the maximum hypothetical accident, or, the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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81 accident that's described in the regulation in a 1
footnote.
2 And for that evaluation, Reg Guide 1.183 3
allows you to credit systems downstream of the second 4
MSIV leakage -- MSIV valve, excuse me, main steam 5
valve -- isolation valve, providing that they -- words 6
to the effect that they could survive a safe shutdown 7
earthquake. So there's a difference in the guide.
8 We're applying a more strict interpretation for the 9
MHA than is applied for whatever you wanted to call 10 lesser accidents.
11 So the credit now does exist for a pathway 12 to the condenser in the current guide. What we're 13 anticipating -- and of course, this is all pre-14 decisional. But what we're working on is to provide 15 some guidance that could be followed for the maximum 16 hypothetical accident which could -- we would have 17 reasonable assurance of a pathway to the condenser.
18 And we will also provide certain removal coefficients 19 that could be used for that particular evaluation.
20 MEMBER HALNON: Okay. That reconnected 21 the dots. Thank you. I appreciate it.
22 MR. PARILLO: Thank you.
23 MEMBER REMPE: So Greg, now you're getting 24 back into the, oh, well, yeah, but then they also 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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82 confirm it. Well, will the confirmatory information 1
be less distinct is what I'm trying to say. And 2
again, is the flow rate so big that there are no 3
needed changes in the EOPs, because there's no mention 4
of this at all in the FitzPatrick response from the 5
staff.
6 And so again, were there -- and I heard 7
earlier, well, I think there might've been some 8
changes in the EOPs, I believe from Steve. Were there 9
some changes in the EOPs? And is that something 10 that's always done? Or it's just, no, this does not 11 matter?
12 MR. PARILLO: Well, maybe I should take 13 it. This is John Parillo again. I think a key to 14 understanding what went on with FitzPatrick, I mean, 15 they -- like I said before, they -- prior to this 16 recent amendment which was granted, FitzPatrick had 17 the lowest MSIV leakage limit in the fleet, 46 18 standard cubic feet per hour.
19 Now they -- by virtue of this amendment, 20 now they will have a leakage limit, total leakage of 21 200 standard cubic feet per hour. Now I'm not an 22 operator. But if you think -- I think what you're 23 asking is what does that change -- what does the 24 impact of that change and is that going to have a 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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83 significant impact on operator actions?
1 And I would say that you're going from an 2
incredibly --- to a very low leakage. And I don't 3
think offhand that there would be any perceptible 4
difference downstream. But I would defer to an 5
operator to verify that. But my gut feeling is that 6
it's not something that would require any kind of a 7
change in an emergency operating procedure. But 8
that's --
9 MEMBER REMPE: And this was a plant that 10 had very low leakage valves. And again, this is going 11 on with the operating -- some of the operating fleet.
12 MR. PARILLO: Yeah, well --
13 MEMBER REMPE: I'm just curious. Would it 14 be too much to ask if you could pull the string and 15 say, yeah, it was considered even if the staff didn't 16 do it in their review of the LAR by the actual plants 17 and they did not need to make any changes to EOPs or 18 they did but they thought about it? That's what I'm 19 trying to ask today.
20 And it's not -- again, maybe I'm slow.
21 I'm also not an operator. But I just am curious 22 because it's of interest. It could be a safety issue.
23 I just am curious.
24 MR.
DOZIER:
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84 consideration, of course the things that the licensee 1
would need to do is being considered in the Reg Guide 2
update. So certainly, I think we could -- we would be 3
asking those questions, what would need to be done?
4 So I think the answer to your question, Dr. Rempe, is 5
yes.
6 MEMBER REMPE: Yes, you are asking that 7
question and so it is being done. That's what I 8
wanted to hear today.
9 MR. JONES: This is Steve Jones. I think 10 just to clarify, there is an evaluation that's 11 included in the BWR topical report dealing with credit 12 for this type of main steam isolation valve, leakage, 13 holdup, and deposition. And one of the main concepts 14 is that these higher level leakages do not represent 15 any condition that's outside what you would expect 16 from a good or a very well performing main team 17 isolation valve.
18 In other words, as John said, we're just 19 going from extremely low leakage to very low leakage 20 to get these type of leakage limits. Three cubic feet 21 per minute at 45 psig is still a very tight valve for 22 this size. We're talking about nearly a foot diameter 23 of the seat. So it's just, again, balancing how 24 frequently these valves are reworked and the operator 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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85 dose associated with that versus how well they perform 1
in the absolute containment of fission products post-2 accident.
3 MEMBER REMPE: So I'll try and paraphrase 4
again. You're saying that there is some sort of BWR 5
topical report where the staff does -- or a Reg Guide 6
that would guide the staff to ask that question. Are 7
there any changes that need to be made to the EOPs if 8
there were a need to verify that the MSIV has closed 9
in light of the increased leakage?
10 MR. JONES: Well, what there is, is 11 there's a statement from industry. And the staff has 12 accepted that the -- that in the leakage -- in the 13 range of leakage limits we're discussing here, there's 14 very high confidence that the valve would continue to 15 perform as designed. There's no degradation or any 16 change in response that's expected from this change.
17 MEMBER HALNON: So Joy, this is Greg. I 18 have never put my eyes on it, but I am pretty sure 19 that there's, in EOP, the symptom-based EOPs were 20 increasing, radiation increasing heat in the steam 21 tunnel, other things that would drive you back to 22 verify that the MSIVs are closed.
23 MEMBER REMPE: I would think so too. And 24 then the question is with the increased leakage, is it 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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86 harder for them to detect it, is what I'm kind of 1
asking. And again, I'm kind of -- I'm not getting a 2
real strong answer that I expected to get when I 3
raised the issue. Maybe it's because I don't 4
communication very well.
5 MR. JONES: The steam tunnel temperature 6
monitoring and things like that is outside the -- I 7
mean, it's in the steam tunnel. But it's not touching 8
the piping or anything like that. So you're not going 9
to see that response at the type of leakage limits 10 we're referring to here. Again, it's very low. And 11 in terms of mass, a very, very low leakage rate.
12 MEMBER HALNON: Yeah, the point is --
13 MR. JONES: And they can't transfer much 14 energy.
15 MEMBER HALNON: The point is the operators 16 are trained on scenarios that MSIVs have either failed 17 to close or have increased leakage through. And I 18 think what Joy is looking for is some validation, one, 19 was that already there, and two, was there any 20 additional actions they may need to take based on the 21 fact that we're increasing the leakage limit? So 22 that's the --
23 MEMBER REMPE: And actually, it's only the 24 latter point. I'm pretty confident too it's there.
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87 But the question is does it need to change? And 1
that's what I am trying to get to. And --
2 (Simultaneous speaking.)
3 MR. JONES: Yeah, the value was just too 4
low to be significant with respect to the valve 5
performance or the effect it would have on the 6
downstream --
7 (Simultaneous speaking.)
8 MEMBER REMPE: And I would buy that. If 9
that's the answer, that makes sense to me and so I'd 10 buy that. What I -- I guess I didn't hear that till 11 this last time, and I know I kept berating it. But 12 again, if that's the case and you're confident that 13 that is the case, it's just too low, it would not 14 matter, that would be fine. I just was curious when 15 I saw that.
16 MEMBER KIRCHNER: Yeah, Joy, this is Walt.
17 I would second Steve's answer. Basically, the 18 inventory of the PCS, for these low leakage rates, 19 you're not going to pressurize the power conversion 20 system with these low rates of leakage. There's so 21 much -- there's so many thermal -- there's so much 22 thermal loss in the system that with this low leakage, 23 it's unlikely you can pressurize the volume that the 24 PCS occupies. So you're not going to see a 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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88 significant difference within the bands that the staff 1
has been talking about in terms of increased leakage 2
from a shut main steam isolation valve.
3 MEMBER REMPE: Again, that answer makes 4
sense, but it took a while to get to that answer. And 5
that's what I -- again, I just wanted to make sure 6
that either it was thought out or it was thought about 7
and dismissed. But I didn't hear that as clearly 8
until this last time. So thank you for your tolerance 9
of me bringing it up.
10 MEMBER KIRCHNER: I have a question to the 11 staff. On the viewgraph in front of us, you talk 12 about holdup. Does holdup include deposition? Does 13 this allow -- if the licensee, the applicant can 14 demonstrate a credible deposition model, does -- is he 15 or she allowed to take credit for that as well? You 16 seem to use the term, sometimes, interchangeably. But 17 I think holdup means something different to me than 18 deposition.
19 MR. PARILLO: This is John Parillo again.
20 I could refer you to Appendix C of Reg Guide 1.183.
21 I believe it provides a deposition of -- I believe 22 it's 10 percent for iodine. And then the holdup is 23 addressed by a leakage of one percent per day.
24 (Simultaneous speaking.)
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89 MEMBER KIRCHNER: And that was my second 1
question, John. That leakage is based on one percent 2
per day. Is that the venting of the air ejector 3
condenser? Or is that just a cumulative estimate of 4
what a PCS would --
5 (Simultaneous speaking.)
6 MR. PARILLO: It's just applied to 7
whatever the source term is that reaches the condenser 8
in that particular accident.
9 MEMBER KIRCHNER: But where did you come 10 up with the number?
11 MR. PARILLO: The volume -- the leakage 12 goes into the condenser volume, and then it leaks out 13 of that volume at one percent per day.
14 MEMBER KIRCHNER: And that's based on the 15 venting of the air ejector condenser or just leakage 16 17 MR. PARILLO: No.
18 MEMBER KIRCHNER: -- in the system?
19 MR. PARILLO: No, no. I'll let --
20 MR. JONES: This is Steve Jones. I guess 21 I can address some of the systems aspects of this.
22 MEMBER KIRCHNER: Yeah, please, Steve.
23 MR. JONES: I mean, we're talking about a 24 rod drop accident. So you'd have as the source a 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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90 localized high power within several rods -- maybe more 1
than several -- but anyway, a high power condition 2
that results in cladding rupture. And then that's 3
diluted throughout the rest of the RCS and comes out 4
in the steam system. The -- so it would be 5
transported through the turbine to the condenser 6
pretty rapidly. Once it's in the condenser, there are 7
high radiation monitors that would close and isolate 8
the vacuum pumps that are connected to the main 9
condenser. So --
10 MEMBER KIRCHNER: Okay. So then it's just 11 12 (Simultaneous speaking.)
13 MR. JONES: -- we'd just be talking about 14 leakage.
15 MEMBER KIRCHNER: Okay. Does that take on 16 then -- do you then require additional quality 17 assurance requirements on that function of isolating 18 the air ejector condenser?
19 MR. JONES: We --
20 (Simultaneous speaking.)
21 MR. JONES: I mean, that is a safety-22 related instrumentation function to isolate. But the 23 pressure boundary itself is not.
24 (Simultaneous speaking.)
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91 MR. JONES: I mean, there's a -- there is 1
also a high radiation trip, primary containment 2
isolation that goes with that. So I mean, all these 3
things are happening at once. So you're going to get 4
just a part of that source term is going to get into 5
the power --
6 MEMBER KIRCHNER: Right.
7 MR. JONES: -- conversion system. And 8
then it's going to leak out over a period of time.
9 That's really what you're modeling. And so the 10 distinction between holdup and deposition is holdup is 11 there's just a volume there that --
12 MEMBER KIRCHNER: No, I understand that.
13 MR. JONES: -- retains --
14 (Simultaneous speaking.)
15 MEMBER KIRCHNER: I just wanted to 16 distinguish whether you also allowed credit for 17 deposition because your viewgraph just talks about 18 holdup. Okay. I get it. Thank you.
19 MEMBER BROWN: Dave, this is Charlie. Can 20 I ask a question?
21 CHAIR PETTI: Sure.
22 MEMBER BROWN: This is definitely not my 23 bailiwick, okay, BWRs in particular since I was a PWR 24 person. But correct me if I'm wrong. But it sounds 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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92 like the whole reason for this, the ability to get to 1
this alternate source term, is the deposition and the 2
holdup in the condenser.
3 And all I heard was model, model, model 4
all the way through the presentation. So I'm not 5
objecting to that. But has there ever been any 6
experimental basis for what expected deposition rates 7
would be in these materials or holdup in the condenser 8
based on the conditions that are there? Or is it just 9
analytically developed based on analysis?
10 CHAIR PETTI: This is Dave. My view is 11 there's tons of data. Billion dollars was spent in 12 severe accident research --
13 MEMBER BROWN: Okay. I didn't hear that.
14 I'm sorry.
15 CHAIR PETTI: -- looking at deposition in 16 different systems, the effect of water as a way to 17 wash out aerosols.
18 MEMBER BROWN: Okay. All right. I'm good 19 with that. I just didn't hear anybody refer to that 20 21 CHAIR PETTI: Yeah.
22 MEMBER BROWN: -- for the modeling 23 calculations. Okay. Thank you very much. This has 24 been enlightening, for me anyway.
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93 CHAIR PETTI: Any other comments from 1
members? If not, we'll move on to the NEI. I see 2
Steve Schultz had a question. Steve?
3 MR. SCHULTZ: Yes, this is a question for 4
Mike and then also probably for John Parillo as well 5
because it looks at it from two different ways. The 6
discussions we've had today talks about the 7
opportunity to use a risk-informed approach with the 8
first stab to look at this particular set of license 9
amendment requests and help with the decision making 10 associated with it. And then at the end, John and 11 others have talked about making an application of this 12 or expanding the thinking associated with Reg Guide 13 1.183 modifications, moving from just to consideration 14 in control rod drop to the design-basis event 15 evaluation. And my question is, is this type of 16 evaluation, the diverse approach, risk-informed 17 approach, can we expect to see this in other areas in 18 the revisions that are being proposed and evaluated 19 for the Reg Guide 1.183? Is the staff adopting this 20 type of an approach for that Reg Guide modification 21 evaluation?
22 MR. FRANOVICH: This is Mike Franovich.
23 I think Shilp actually might be in a better position 24 to address that. But the extent of the proposal here, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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94 there is a symmetry of sorts between the ISG which is 1
focused on the staff's evaluation, particularly when 2
the licensee has results that may be close to a limit 3
and where you start grading your level of effort, 4
versus the Reg Guide revision which is, again, focused 5
on what the licensee might be taking credit for and 6
perhaps more modernized approaches than relying on 7
trying to use the -- what's been referenced already as 8
the BWR Owners Group topical report that's been -- was 9
reviewed now over 20 years ago. And so that sort of 10 modernization is the extent of the -- the risk-11 informing part, it's the primary part. But maybe 12 Shilp or John can amplify further.
13 MR. SCHULTZ: Thank you, Mike. Yeah, for 14 Shilp, one of the things that certainly has been 15 evaluated here which wasn't done 20 years ago was the 16 association of the conservatisms that are in other 17 pieces of the evaluation and analysis. And in other 18 words, the focus was on the dose evaluation and that 19 particular evaluation and not conservatisms that play 20 into that from other areas, like seismic, for example.
21 MR. VASAVADA: Yeah, so this is Shilp.
22 That's correct. In this case, the -- as I mentioned 23 in one of my slides, we just looked at a sliver of the 24 entirety of the dose calculations in the context of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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95 the challenges that we were facing because of 1
uncertainty in a parameter in the licensee's dose 2
calculations. And what Mike mentioned had more 3
granularity to that. Using what we've done in the 4
technical assessment for the ISG, what we are planning 5
to do or we're trying to do is see if we can 6
streamline some of the information that the licensees 7
have to provide to take formal quantitative credit to 8
approaching the Reg Guide for the condenser.
9 In the previous case that the BWR topical 10 from 20 years ago, the topical is from '93, I believe, 11 or safety evaluation is from '99 that has nine 12 limitations and conditions which the licensees have to 13 meet to take credit using the latest and greatest 14 information that we have in 20-plus years of operating 15 an earthquake experience. We are looking to see how 16 we can streamline those information needs and kind of 17 order the amount of information that the licensee has 18 to offer, maybe on a tiered approach based on how 19 significant their seismic hazard is at a particular 20 site. So those are some of the thoughts how we are 21 trying to use what we developed for the ISG into the 22 Reg Guide development.
23 MR. SCHULTZ: Thank you very much.
24 Appreciate that.
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96 MR. VASAVADA: So this is Shilp Vasavada 1
again. If Kevin Petti can allow me, I just wanted to 2
go back to one of the items I had a note from Member 3
March-Leuba's comments. If I can just speak to that.
4 CHAIR PETTI: Sure.
5 MR. VASAVADA: All right. So Member 6
March-Leuba mentioned something about needed a 7
calculation or would like to see a calculation. I 8
just wanted to, again, put it in the context of the 9
purpose of the ISG. The purpose was not, again, to 10 give or for the staff to introduce which we cannot, 11 quantitative credit in a licensee's calculation.
12 The point was to see, okay, if we were to 13 think about this realism in our decision making, can 14 we overcome challenges in the uncertainties and some 15 parameters in the licensee's calculations? So it was 16 hard to come up with a factor. And yes, you're right.
17 Things can heat up and there can be revolatilization 18 of aerosols.
19 But again, the comparison is against a 20 case where the PCS is not even considered. There's a 21 direct release as Steve pointed out, the ground cover 22 release and then it goes to the control room.
23 Compared to that, if one were to realistically think 24 about the PCS, even with revolatilization -- I can't 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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97 ever say that -- there would be in reality holdup 1
volumes which would lead to a decay of even those 2
aerosols and a reduced dose compared to the 3
calculation of the licensee.
4 And this is on record that the licensee 5
has provided which does not consider any of that. So 6
that was the context and that's the reason why we did 7
not see the need to have a factor developed. So I 8
just wanted to go back to that. Thank you for the 9
time.
10 CHAIR PETTI: Okay. Unless I hear other 11 questions from members, I think we should turn to NEI 12 at this point.
13 MR. BROADBENT: So this is Greg. Frankie, 14 did you want to say anything to begin with?
15 MS. PIMENTEL: No, I mean, other than we 16 appreciate the opportunity to provide industry 17 feedback during this discussion of the ISG. Other 18 than that, we can get started with our presentation.
19 MR. BROADBENT: All right. Let me go to 20 the start. So can everybody see the presentation?
21 CHAIR PETTI: Yes.
22 MR. BROADBENT: All right. I'm Greg 23 Broadbent. I work for Entergy. I'm a senior staff 24 engineer in the corporate office. And we have Frankie 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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98 on the call as well from NEI.
1 I've been working for most of my career at 2
Grand Gulf. So I'm familiar with BWRs a lot more than 3
PWRs. And so this is a radiological analysis as well.
4 So this is a topic that I think I'm prepared to 5
discuss. Go to the next slide.
6 Talking about in general starting with 7
risk-informed regulation, we certainly support the 8
NRC's efforts to risk inform all regulatory 9
approaches. With regard to this, I'll mention -- with 10 regard to the MSIVs, going off script a little bit 11 here, the MSIVs are some of the biggest valves that we 12 have in our plant. The ones at Grand Gulf, I think 13 the steam lines are, like, 28 inches.
14 And we've got eight MSIVs that need to 15 close very quickly. And they have some of the lowest 16 leakage requirements of all the valves in the plants.
17 So this is -- you need to take that in context that 18 these are very, very low leakage to begin with and 19 very big valves and that there are ALARA issues 20 associated with this.
21 Going in and having to rework those valve 22 seats does incur a lot of dose. And that's described 23 in the BWR Owners Group report. And I think they may 24 actually have some numbers in there.
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99 It's also an outage length issue. We 1
could -- we'd have to extend the outage because these 2
valves can't be worked online. So we have to be shut 3
down before we can actually do anything with regard to 4
these valves.
5 We're only talking about small increases 6
in this already small leakage rate allowance that we 7
have in our tech specs. And by risk informing this, 8
it allows us to spend our resources in areas that are 9
most important to safety. So if it's not important 10 that we incur personnel doses, real doses to people by 11 allowing a little higher leakage rate on these valves, 12 then we feel that's a good allowance to -- a good 13 balance to allow us to increase these leakage rates.
14 And we've also seen some recent successes 15 with GSI-191 resolution with a risk-informed approach.
16 And 50.46 has recently taken some statistical 17 approaches as well. So we feel like this ISG is the 18 first step in risk informing the radiological 19 analyses.
20 We feel that there may be other areas.
21 And we'd certainly like to discuss that with the 22 staff. But we're really just talking about the ISG 23 here.
24 I'll quote Shilp from just about 30 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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100 minutes ago where he talked about this ISG is just a 1
small sliver of realism in a universe of conservatism.
2 And I think we would agree with that certainly. And 3
the industry supports including these approaches in 4
Revision 1 of the Reg Guide, and we know that the 5
staff intends to do that.
6 We also recognize that the power 7
conversion system is likely to remain intact post-8 accident. It is built to very high standards. And we 9
do have confidence that the SSCs in the power 10 conversion system will provide sufficient volume for 11 holdup and retention of the fission products like the 12 ISG concluded and also recognize that the power 13 conversion system is an important system for plant 14 operation, not just post-accident.
15 But that is really where we make our 16 money. And we have to keep that system operational 17 and generally leak free in order to get steam to the 18 turbine and turn the generator so that we can stay in 19 operation. Within Entergy, we've had some plants that 20 weren't able to stay in operation because they weren't 21 able to make the financial numbers we needed.
22 So it is a system that we keep in 23 operation. And we can -- in the event that there are 24 issues with it or any sort of failures, they're 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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101 clearly evident in a BWR plant. Steam plumes, high 1
radiation in certain areas would alert us to any 2
leaks, maybe some drain flows, also even things like 3
trouble with people exiting the radiologically 4
controlled area due to contamination of some noble gas 5
isotopes that stick to people's clothes.
6 So as we mentioned, approximately half the 7
plants have already demonstrated that the structural 8
integrity would be maintained using the BWR Owners 9
Group report that's currently out there. And we feel 10 that this ISG also validates the current regulatory 11 credit that we take for the power conversion system 12 and other accident analyses like the control rod drop.
13 I think that was previously discussed. Going to the 14 next slide.
15 And we feel that the ISG does incorporate 16 a good amount of operating experience, certainly the 17 post-Fukushima seismic risk insights. The Owners 18 Group report done back in the 1990s used earthquake 19 experience data. Obviously, there's more now than 20 there used to be. So that's incorporated in here.
21 And we do like the fact that the NRC is 22 including explicit credit for at least these 23 conclusions in the upcoming Reg Guide. And we also 24 recognize that the LARs that were previously approved 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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102 really didn't use Rev. 1. They used Rev. 0 of the Reg 1
Guide. So we've also like to have credit for plants 2
that are applying Rev. 0 to be able to use the 3
conclusions in this ISG.
4 And with regard to steam line deposition 5
credit, there is some parts of the steam line that are 6
credited in the analysis, even if we're not crediting 7
the power conversion system, for example, the volumes 8
between the MSIVs where they're isolated. And we want 9
to make sure that there's realistic modeling 10 associated with a deposition in the steam line. And 11 that's important to us.
12 That's a release pathway that's directly 13 coupled to the reactor vessel currently modeled to be 14 released directly to the environment. So it can be a 15 very significant release pathway and a contributor to 16 doses due to some of the conservative assumptions that 17 are in that analysis. And I think it was previously 18 discussed from the staff's side that there were --
19 that there's been a lot of history associated with 20 this.
21 There was an Owners Group report back in 22 the 1990s. AEB-9803 came out for the Perry Plant.
23 And then there's been some concerns about using AEB-24 9803 and the applicability to other plants. So from 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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103 our perspective, there's been a lot of significant 1
regulatory uncertainty regarding what models are 2
acceptable for steam line deposition.
3 And as the staff pointed out that there is 4
no specific discussion in Revision 0 of the Reg Guide.
5 And we do like the fact and want to work with the 6
staff to provide an approved model for deposition in 7
Revision 1. And I'm sure that it's flexible enough to 8
apply to all BWRs and even the advanced plants. And 9
I think that was it for our presentation, yes.
10 MEMBER HALNON: Greg, this is Greg Halnon.
11 Just a quick question. Since we're talking about 12 higher depositions in the secondary side of the plan, 13 is there any impact on control room dose or any other 14 impact with time operator studies as you have to 15 respond to other things in the turbine buildings and 16 areas that the doses may be higher?
17 MR. BROADBENT: Well, and the answer to 18 that is there's really nothing that we respond to in 19 the turbine building. The turbine building is not a 20 safety-related building. So we can't put anything 21 important in there. So the fact that maybe with these 22 increase the leakage allowances that the doses may 23 increase a little bit on that side of the building.
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104 equipment, if it's not an area where the operators 1
have to transit through to get to some safety-related 2
equipment or some action they need to take post-3 accident, then it's really not an issue for us.
4 MEMBER HALNON: How about actually 5
changing a shift of operators? I know that some of 6
the plants, you don't go through their turbine 7
buildings or near. But I don't know all the designs.
8 MR. BROADBENT: Yeah, I'm not changing a 9
shift early, or --
10 MEMBER HALNON: Yeah, this could go on for 11 a while, though. So anyway, I guess you answered the 12 question. There's no required actions that could be 13 affected by dose.
14 I'm assuming that the control room doses 15 have been checked and no issue on that. So everything 16 else would be a site-specific issue that might have 17 people transit through an area of higher dose. But I 18 think you answered my question. That's fine.
19 MR. BROADBENT: Yeah, that's right. And 20 any impact on control room dose, if there's any sort 21 of shine or anything from the turbine would be 22 included in a control room dose if that was really a 23 significant pathway for dose to the operators.
24 MEMBER HALNON: Okay. Thank you.
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105 MR. BROADBENT: Any more questions for me?
1 MEMBER MARCH-LEUBA: Yes, this is Jose.
2 I just wanted to make a comment that you triggered my 3
thought process. I found argument on ALARA very 4
convincing. It really makes sense. Unless I'm 5
mistaken, during risk-informed evaluations, we don't 6
consider that.
7 I'm thinking -- I'm just putting it out on 8
the record -- that maybe we're using the wrong cost 9
functions, thinking like a mathematician, that the 10 reason that we need to minimize is not only the risk 11 to the public but also the risk of the facility 12 workers. It's a combination of the two with proper 13 waiting. Just put it out there that you make a good 14 argument that why am I going to give 10 drams for a 15 couple of operators for something that doesn't really 16 produce a significant benefit.
17 MR. BROADBENT: And that argument was the 18 Owners Group report back in the 1990s came up with.
19 And that's right. Why take dose that is specifically 20 from -- or 100 percent certain we're going to get 21 because we're going to go out and work those valves 22 and compared to an accident dose that we would receive 23 or the operators would receive and maybe some offsite 24 would receive for a very, very low probability 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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106 accident. So that was the Owners Group approach.
1 CHAIR PETTI: And frankly, Jose, it's one 2
of the reasons I thought we should hear this in 3
subcommittee. This is a very subtle but interesting 4
result. And I just thought that all the members, as 5
we think about risk-informed regulation, would like to 6
understand this tradeoff that we've heard today.
7 (Simultaneous speaking.)
8 MEMBER REMPE: -- we've got this other 9
situation where we have some design developers who do 10 not want to consider ALARA in Part 53, but just 11 throwing it out there, right?
12 CHAIR PETTI: But it's required in Part 13
- 20. And they have to live to Part 20.
14 MEMBER REMPE: Yeah, I know. It's just 15 something to think about where it goes, but anyway.
16 CHAIR PETTI: Okay.
17 MEMBER MARCH-LEUBA: And then with respect 18 to -- to comment about control room dose, I missed the 19 plans where you have to run by the feedwater pump to 20 get into the control room. And the path to control 21 room goes by the turbine and all the secondary. So I 22 assume those plants would consider increased leakage 23 to -- we did consider the dose to the control room 24 operators.
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107 But if you have to get there, you have to 1
walk by a contaminated area. It should incorporate 2
analysis. That was just a rhetorical comment.
3 CHAIR PETTI: Any other comments from 4
members?
5 Okay. So at this point, Scott and Thomas 6
are going to try to fix the public line. So Scott, 7
before we take public comment, he's going to --
8 (Simultaneous speaking.)
9 MR. MOORE: Yes, thank you, Chairman. So 10 for all the members on the phone, we're going to reset 11 the phone line now. And so you're going to drop off 12 as we reset, and you need to call back in immediately.
13 And this will take just a couple minutes, 14 and then we'll go to public comments. Thanks, 15 everyone. Thomas, you can reset the public line at 16 this point. Thank you.
17 MR. SNODDERLY: Excuse me, Chairman Petti.
18 This is Mike Snodderly. While we have some time, I 19 just wanted to make one comment.
20 CHAIR PETTI: Go ahead.
21 MR. SNODDERLY: So I just wanted to remind 22 the members and the staff that as was mentioned in the 23 slides, the staff has received public comments on the 24 ISG. And the staff is currently -- or has resolved 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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108 those comments. But we did not hear about them today 1
because of the very full agenda and making sure that 2
everyone clearly understood the precedent that had 3
been set through the LARs. But the staff does plan to 4
address the resolution of those public comments when 5
we have the full committee meeting right now currently 6
scheduled for November. So I just wanted to remind 7
the staff and the members and also get on the record 8
that we will go over the final resolution of the 9
public comments received in November.
10 CHAIR PETTI: Thank you, Mike.
11 MR. MOORE: Thomas or Makeeka, are either 12 of you on?
13 (Pause.)
14 MR. DASHIELL: Public bridgeline has been 15 reestablished.
16 MR. MOORE: Thomas, you said it has been 17 reestablished?
18 MR. DASHIELL: That is correct, Scott.
19 MR. MOORE: Okay. Thank you.
20 CHAIR PETTI: And I assume all those beeps 21 are people calling back in, right?
22 MR. MOORE: Yes, sir.
23 CHAIR PETTI: Okay. Let's give them 24 another minute, and then we'll ask for if there's any 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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109 public comments.
1 (Pause.)
2 CHAIR PETTI: Okay. I'm not hearing any 3
more beeps. So hopefully, everybody is back on. Are 4
there any comments from members of the public? If so, 5
please state your name and your comment.
6 Again, any comments from the public?
7 Okay. Not hearing any, we're going to 8
turn to the staff -- I mean to the members. Any other 9
comments on presentations today and the topic at hand?
10 MEMBER KIRCHNER: Dave, this is Walt. I 11 have one general comment going back to the questions 12 I asked of the staff. When this is presented at full 13 committee, I really strongly feel that more context is 14 needed up front because on the surface, it could be 15 misinterpreted by the public that we're using these 16 risk-informed measures to relax requirements. And 17 that's not really the case.
18 But it sounds like it on the surface 19 because we're talking about increasing leakage of 20 valves. So that sounds like a problem. And as the 21 NEI presentation made clear, we're not necessarily 22 relaxing protection of the public. We're actually 23 doing a more physically accurate representation of 24 what happens and demonstrating that the public is 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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110 probably more protected when you analyze the problem 1
in that manner.
2 And then obviously, LARs cost money. So 3
the industry does an LAR often because there's an 4
economic gain that offsets the cost of the LAR in 5
terms of the operation of the plant and the safety of 6
the plant. So I just think more context would be 7
useful up front in an abbreviated presentation to the 8
full committee, especially if the NEI doesn't 9
participate in that presentation. Thank you.
10 CHAIR PETTI: That's a good point, Walt.
11 I'm sure NRR is listening. Thanks.
12 MEMBER BALLINGER: This is Ron. We often 13
-- we always make a distinction between members of the 14 public and workers at the plant. But as soon as the 15 worker goes home for supper, he or she becomes a 16 member of the public. And so radiation dose is 17 radiation dose. And it's useful to save it, period.
18 CHAIR PETTI: Anyone else?
19 Okay. Well, I want to thank the staff and 20 NEI. Very informative presentations today. Members, 21 of course I have a draft letter. I will place it on 22 your NRC emails. And you can hack it at will and add 23 any comments that you feel need to be there.
24 We've got a little bit of time since full 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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111 committee won't be now till November. If I recall, 1
this was going to be an October thing, but things are 2
moving around. But I'll at least get it out there for 3
you to think about it before you forget your thoughts 4
before the November full committee.
5 And with that, we'll adjourn the meeting.
6 And I guess we come back at 2:00 o'clock Eastern for 7
the afternoon session. Thank you, all.
8 (Whereupon, the above-entitled matter went 9
off the record at 12:34 p.m.)
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1 Presentation to ACRS Subcommittee on Draft Interim Staff Guidance for Radiological Consequence Analyses Using Alternate Source Terms Mike Franovich, Director, NRR/DRA Kevin Hsueh, Branch Chief, NRR/DRA Jerry Dozier, Senior Reliability and Risk Analyst, NRR/DRA Steve Jones, Senior Safety and Plant Systems Engineer, NRR/DSS Shilp Vasavada, Branch Chief (Acting), NRR/DRA John Parillo, Senior Reactor Engineer, NRR/DRA July 23, 2021
2 Introductory Remarks A changing regulatory environment:
- Licensing, other regulatory decisions, and backfit/forward fit actions must be risk-informed. (SRM-SECY-19-0036, SRM-SECY-18-0049)
- Improved realism, evaluation techniques, and additional information are applied to improve risk-informed regulatory decision making (ML19319C832)
- Culture re-alignment is needed to ensure that we identify and resolve challenges and roadblocks for the appropriate and consistent integration of risk insights.
3 Introductory Remarks (Contd)
- Integrated Review Team process (LIC-206) was used in the staffs approval for BWR LARs to allow for increased MSIV leakage.
- All four MSIV reviews were completed using a team approach.
- Each SE includes a section on risk and engineering insights to support staffs reasonable assurance finding.
- ISG is being developed to memorialize staffs practice.
4 Introductory Remarks (Contd)
- Draft RG 1.183 Rev. 1 (DG-1389)
- Staff efforts have restarted using an integrated team to revise RG 1.183, Alternative Radiological Source Terms for Evaluating DBAs at Nuclear Power Reactors.
- An ACRS meeting is being planned for Fall 2021, prior to issuance of DG-1389 for public comment.
5 Outline
- Overview of the Interim Staff Guidance (ISG)
- Background of ISG
- Basis for ISG - Technical Assessment
- Overview
- Details
- Difference between ISG and Regulatory Guide 1.183 Revision
- Takeaways
6 Overview of ISG - Timeline
- Published in Federal Register for public comment day comment period closed on June 21, 2021
- 13 comments received from NEI, 20 anonymous comments
- ACRS full committee briefing scheduled for November 2021(tentative)
- OMB approval - January 2022(tentative)
- Final FRN - February 2022(tentative)
7 Overview of ISG (Contd)
The ISG is expected to be transitioned into SRP Section 15.0.1 (Radiological Consequence Analyses using AST) in conjunction with the separate RG 1.183 revision effort.
Section 15.0.1 will include a reference to the revised RG 1.183.
ISG will be closed after transition to Section15.0.1.
8 Overview of ISG - Primary Insight
- High probability that doses will be lower than those estimated strictly using traditional deterministic methods, which include accepted assumptions, that do not credit hold-up and retention of the Main Steam Isolation Valve (MSIV) leakage within the power conversion system (PCS)
9 Overview of ISG - Objective and Expectation
- Objective: Near-term formal regulatory footprint for staffs use of risk insight
- Expectations:
- Used by staff to offset uncertainty in input parameter(s) for deterministic calculations
- Supports staffs reasonable assurance finding during reviews
- Transitioned to Standard Review Plan Section 15.0.1
- Caveat:
- Does not change the licensees responsibility to demonstrate compliance with 10 CFR 50.67
- Does not change acceptable methods for demonstrating compliance with 10 CFR 50.67
10 Background of ISG - Genesis
- Commission direction to become a modern, risk-informed regulator (e.g., SRM-SECY-19-0036; ML19183A408)
- Four license amendments were submitted to allow for increased MSIV leakage in 2019
- Challenges due to uncertainty in input parameter values in dose calculations
- LIC-206 (ML19031C861) invoked for multi-disciplinary risk insights
11 Background of ISG - Genesis (Contd)
- Integrated review team approach following LIC-206 guidance
- Identified that risk insights support consideration of holdup in PCS
- Ability to offset challenges without changing calculation methods and assumptions
- Documented insights in technical assessment
- Internal reviews and deliberations
- Included in all four safety evaluations for the LARs to allow for increased MSIV leakage (ML20140A070; ML20150A328; ML20241A190; ML20265A240)
12 Basis for ISG - Technical Assessment
- Formal credit for condenser through safety evaluation on BWROG Topical Report -
approximately half of BWRs have adopted this method.
13 Large Holdup Volume in PCS
14 Technical Assessment - Overview Technical Assessment Problem Formulation using Risk Triplet Operational Insights Realistic Transport Pathway Seismic Capacity
15 Technical Assessment - Risk Triplet Formulation
Operational Insights 16
- Main Steam System Piping:
- Large internal volume
- Typically designed to B31.1.0, "Power Piping"
- Constructed with augmented quality
- BWR 5 and BWR 6 designed to B&PV Code - safety-related
- Typically, large globe valves that seat with pressure
- Stem leakage from outboard valve considered a small fraction of measured seat leakage
- Passive features provide hold-up volume for MSIV seat leakage
17 Realistic Transport Pathway
- Consideration of piping attached to steam lines
- No alignment of specific leakage path
- Reliability of complete isolation; larger valves leak more
- Functional drain lines flow to main condenser
- Turbine bypass valves also flow to main condenser
- Other leakage, primarily through stop and governor valves to high pressure turbine, provide for less holdup and deposition than main condenser
18 Seismic Capacity: A Primer
- Fragility: Conditional failure probability as a function of seismic acceleration; Analytically determined; Lognormally distributed
- Median fragility (Am): Seismic acceleration at which there is 50%
probability of failure
- Lognormal uncertainty parameters (r for randomness; u for uncertainty): Parameters characterizing the uncertainty in the fragility
- Seismic acceleration: Measure of strength of earthquake in terms of multiples of gravitational acceleration (e.g., 0.1g, 1g)
- Peak ground acceleration: Commonly used acceleration level for seismic analysis; corresponds to acceleration of 100 Hz oscillator
19 Seismic Capacity: A Primer Source: Electric Power Research Institute Report 1025287 (also known as SPID; ML123330282)
Higher Median Fragility Value
20 Approach for Seismic Capacity Evaluation in Assessment Lower Bound Median Fragility to Encompass Seismic Failure Modes Fragility Data
- Multiple and diverse sources
- Recent seismic probabilistic risk assessments (PRAs)
Operating Experience - Walkdowns
- North Anna
- Kashiwazaki-Kariwa
- The Great Tohoku Earthquake of 2011 Representative Risk Estimation
21 Seismic Capacity Insights
- Welded piping, bolted piping, and valves have high median fragilities
- Main condenser is usually a seismic Category II structure
- Anchorage designed to avoid failure at design-basis seismic loads
- Seismic risk from accelerations at and below plants safe shutdown earthquake (SSE) is small
22 Seismic Capacity Insights
- Lower bound median fragility parameters
-Am = 0.4g; r = 0.22; u = 0.22
-Based on fragility of expansion joint connecting circulating water piping to condenser
-Encompasses failure modes of relevant SSCs
-Supports low likelihood of gross failure of SSCs in PCS
23 Representative Risk Estimation
- Convolution of range of hazards with lower bound median fragility parameters
-Provides estimate of risk of gross failure of SSCs in PCS
-Uses latest seismic hazard curves
- Estimates demonstrate low risk of gross failure
-Even lower if contribution only until SSE is considered
24 Uncertainty Consideration for Seismic Capacity Evaluation
- Uncertainty in median fragility is explicitly included
- Conservatisms exist that address uncertainty in selected median fragility
- Use of lower bound median fragility
- Low pressure conditions for high pressure piping
- Consideration of SSE concurrent with the accident postulated for dose calculations
- Conservatisms in remainder of dose calculation guidance are unchanged
25 Holistic Context for ISG
- Requirements in 10 CFR 50.67
- Initial condition assumes failure of multiple redundant engineered protection systems and core damage
- Single-failure of inboard MSIV
- Conservatism in analysis
- Use of acceptable assumptions and parameters
- Concurrent SSE
- Lower bound median fragility parameters
26 Difference between ISG and RG 1.183 Revision ISG RG 1.183 Revision Directed at NRC staff Directed at licensees Provides additional support for the staffs reasonable assurance determination Provides guidance for quantitative credit for holdup in main condenser Does not change the licensing basis dose calculation Quantitative credit changes the licensing basis dose calculation Information needs from licensees are not required Identifies docketed information needs for quantitative credit Licensees responsibility to demonstrate compliance unchanged Acceptable methods for demonstrating compliance unchanged
27
§ 50.67 Accident source term.
- b) Requirements. (1) A licensee who seeks to revise its current accident source term in design basis radiological consequence analyses shall apply for a license amendment under § 50.90. The application shall contain an evaluation of the consequences of applicable design basis accidents previously analyzed in the safety analysis report.
- (2) The NRC may issue the amendment only if the applicant's analysis demonstrates with reasonable assurance that..
28 RG 1.183 Rev 0 MSL Pathway Challenges
- RG 1.183 Rev 0 does not contain an aerosol deposition model for the main steam lines (MSL).
- Instead, many licensees have utilized the leakage pathway model described in the staff assessment entitled, Assessment of Radiological Consequences for the Perry Pilot Plant Application using the Revised (NUREG-1465) Source Term, (AEB-98-03).
- Following multiple BWR license amendment requests to revise their source term to implement an AST under 50.67, the NRC staff published, Regulatory Issues Summary 2006-04, NRC Regulatory Issue Summary 2006-04, Experience with Implementation of Alternate Source Terms.
29 RG 1.183 Rev 0 MSL Pathway Challenges (Contd)
- The purpose of RIS 2006-04 was to discuss the more frequent and significant issues encountered by the NRC staff during its review of AST submittals and to provide information for licensees to consider when developing submittals for implementation of an AST.
- A frequent point of contention between licensees and the NRC staff was the deposition of gaseous iodine in the main steam lines.
30 RG 1.183 Rev 0 MSL Pathway Challenges (Contd)
- For calculation of aerosol settling velocity in the main steam line piping of boiling water reactors, the staff reaffirmed the modeling approach in AEB 98-03 [emphasis added] but emphasized the report was written based on the parameters of a particular plant and, therefore, the removal rate constant is specific to that plant.
- Any licensee who chooses to reference these AEB 98-03 assumptions would need to provide appropriate justification that the assumptions are applicable to their particular design.
- AEB-98-03 has been utilized for more than 20 years when implementing 10 CFR 50.67.
31 MSIV Leakage LARs Submitted Using RG 1.183 Rev. 0
- LARs included drywell spray removal and main steam line (MSL) deposition in their MSIV leakage models consistent with RIS 2006-04 and past precedent.
- Staff questioned how the drywell sprays would impact subsequent MSL aerosol deposition.
- Licensees provided a sensitivity analysis examining the impact of several parameters.
- Of the parameters evaluated, a pathway to the condenser provided a substantial dose reduction.
32 MSIV Leakage LARs Submitted Using RG 1.183 Rev. 0 (Contd)
- The licensees sensitivity analyses are not part of their licensing basis.
- A pathway to the condenser was not credited in the analyses of record (AOR).
- The licensee provided an analysis (the AOR), which met the acceptance criteria in 10 CFR 50.67.
- The staffs determination of reasonable assurance was supported by the recognition that there is a high probability that doses will be significantly lower than those estimated by the licensee using deterministic methods (the AOR) that do not credit holdup and retention of the MSIV leakage within the PCS.
33 Takeaways
- Offsets uncertainty in input parameter(s) for deterministic calculations
- Supports reasonable assurance finding during reviews
- Applicable if quantitative credit is not included in licensees calculations
- ISG does not change licensees responsibility to demonstrate compliance with 10 CFR 50.67
- Acceptable methods for demonstrating compliance remain unchanged
- Formal condenser holdup credit for licensees is being considered in revision to RG 1.183
Backup Slides 34
35 Risk Insight References
- U.S. Nuclear Regulatory Commission, NUREG/CR-7110, Volume 1, Peach Bottom SOARCA, May 2013, ML13150A053
- U.S. Nuclear Regulatory Commission, PRAB-02-01, Assessment of BWR Main Steam Line Release Consequences, October 2002, ML062920249
Iodine Pathway in SOARCA 36
Cesium Pathway in SOARCA 37
RG 1.183 Source Term (Rev. 0) 38
Increased Containment Leakage has Small Impact (SOARCA) 39
Realistic SOARCA releases much less than earlier studies 40
ACRS Meeting on DRA-ISG-2021-XX Greg Broadbent, Entergy Frankie Pimentel, Sr. Project Manager - Engineering and Risk July 23, 2021
©2021 Nuclear Energy Institute 2 Industry supports NRC efforts to risk-inform regulatory approaches
- Risk-informing allows licensees to spend resources in areas that are most important to safety
- Recent successes include GSI-191 resolution and 50.46 using risk-informed or statistical approaches This ISG is the first step to risk-informing deterministic radiological analyses Industry supports including these approaches in Reg Guide 1.183, Rev. 1 Risk-Informed Regulation
©2021 Nuclear Energy Institute 3 Power Conversion Systems (PCS) highly likely to remain intact post-accident
- PCS is built to high standards
- High confidence in the SSCs in the PCS to provide sufficient volume for holdup and retention of fission products
- Important system for plant operation Approximately half of plants have already demonstrated structural integrity with rigorous analyses
- Validates current regulatory PCS credit for other accident analyses Control Rod Drop Accident ISG Conclusions
©2021 Nuclear Energy Institute 4 ISG incorporates relevant operating experience as well as recent post-Fukushima seismic risk insights and walkdowns
- NEDC-31858P used earthquake experience data, primarily from nonnuclear facilities
- Include explicit credit for the conclusions of this ISG approach in Reg Guide 1.183, Rev. 1 Allow credit for plants applying Rev. 0 ISG Conclusions
©2021 Nuclear Energy Institute 5 Realistic modeling of the deposition in the steamline is important for BWRs
- Directly coupled to the reactor vessel
- Calculated dose for MSL is significant due to very conservative assumptions Significant regulatory uncertainty regarding acceptable models in RG 1.183 Revision 0
- Revision 0 of RG 1.183 does not contain an aerosol deposition model for the main steam lines
- Revision 1 should provide an approved model of deposition that is flexible enough to apply to all BWRs including advanced plants Steamline Deposition Credit
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