ML22278A066
| ML22278A066 | |
| Person / Time | |
|---|---|
| Issue date: | 09/08/2022 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| Burkhart, L., Snodderly, M., ACRS | |
| References | |
| NRC-2076 | |
| Download: ML22278A066 (155) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Open Session Docket Number:
(n/a)
Location:
teleconference Date:
Thursday, September 8, 2022 Work Order No.:
NRC-2076 Pages 1-106 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com 1
1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION
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698TH MEETING ADVISORY COMMITTEE ON REACTOR SAFEGUARDS (ACRS)
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OPEN SESSION
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THURSDAY SEPTEMBER 8, 2022
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The Advisory Committee met via teleconference at 1:30 p.m., Joy L. Rempe, Chairman, presiding.
COMMITTEE MEMBERS:
JOY L. REMPE, Chairman WALTER L. KIRCHNER, Vice Chairman DAVID A. PETTI, Member-at-Large RONALD G. BALLINGER, Member VICKI M. BIER, Member CHARLES H. BROWN, JR., Member VESNA B. DIMITRIJEVIC, Member GREGORY H. HALNON, Member
2 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 JOSE A. MARCH-LEUBA, Member MATTHEW W. SUNSERI, Member ACRS CONSULTANTS:
DENNIS BLEY STEPHEN SCHULTZ DESIGNATED FEDERAL OFFICIAL:
3 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 C-O-N-T-E-N-T-S PAGE
- 5) NuScale Topical Report on Emergency Planning Zone Plume......................................4 5.1) Remarks from the Subcommittee Chairman.....5 5.2) Presentations and discussion with representatives from the NuScale and NRC staff..................................7
4 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 P R O C E E D I N G S 1
(1:31 p.m.)
2 CHAIRMAN REMPE: So good afternoon. The 3
meeting will now come order. This is the second day 4
of the 698th meeting of the Advisory Committee on 5
Reactive Safeguards.
6 I'm Joy Rempe, Chairman of the ACRS. Other 7
members in attendance are Ron Ballinger, Vicki Bier, 8
Charles Brown, Vesna Dimitrijevic, Greg Halnon, Walt 9
Kirchner, Jose March-Leuba, Dave Petti, and Matt 10 Sunseri.
11 I note we do have a quorum and similar to 12 yesterday, the Committee is meeting in person and 13 virtually. Communications channel has been open to 14 allow members of the public to monitor the Committee 15 discussion.
16 Mr. Kent Howard is the designated Federal 17 Officer for today's meeting. During today's meeting, 18 the Committee will consider the following topic: The 19 NuScale Topical Report and Emergency Planning Zone 20 Plume.
21 And if we finish early, we'll continue with 22 our report preparations. A transcript of the open 23 portions of the meeting is being kept and it is requested 24 that speakers identify themselves and speak with 25
5 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 sufficient clarity and volume so that they can be 1
readily heard.
2 Additionally, participants should mute 3
themselves when they're not speaking. And at this 4
time, I'd like to ask Walt Kirchner to lead us through 5
our first topic for the day's meeting. Walt?
6 MEMBER KIRCHNER: Thank you, Joy. Good 7
afternoon, all. Welcome. My name is Walt Kirchner.
8 I am Chair of the NuScale Subcommittee for the NuScale 9
review.
10 For the purpose of this meeting is to review 11 the NuScale Topical Report, TR-0915-17772, Methodology 12 for Establishing the Technical Basis for Plume Exposure 13 Emergency Planning Zones and the associated Staff that 14 did the evaluation.
15 Just a few comments from me right now about 16 structure of the meeting. We're going to do this in 17 two parts. The first part will be open. We will allow 18 for public comments after the NuScale and Staff 19 presentations.
20 And then we'll take a break and we'll go 21 into a closed session with NuScale and the Staff. So 22 with that, let me see, we have Mike Dudek on the line.
23 Mike, would you like to make some opening comments?
24 MR. DUDEK: Thank you, Member Kirchner and 25
6 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Chairman Rempe. So this is very exciting today for 1
the Staff to present our safety evaluation reports 2
associated with NuScale's Rev. 3 of the Topical Report 3
that you mentioned, the Methodology for Establishing 4
a Technical Basis for the Plume Exposure Emergency 5
Planning Zones for NuScale Small and Modular Reactor.
6 This is several years in the making. And 7
several revisions in the making and a lot of Staff hours 8
so this Topical Report today was very thought out by 9
all of the Staff Members that had it, bought into it 10 and via edits.
11 Several audits associated with it and came 12 to this resolution for this SER and I, as I read through, 13 I was very impressed by the level of detail and 14 transformation that was captured into it.
15 So I'm looking forward to the discussion 16 today. We're going to discuss how and why this Topical 17 Report is just applicable to NuScale. Some limiting 18 conditions that we had on it and some of the intricacies 19 behind the two RAIs, 9830 and 9828.
20 So a lot of good discussion and planned 21 for today. And with that said, I'll give my DRA 22 brethren a chance to give any opening remarks that they 23 would like to have as well. I think we have Shilp and 24 either Meena or Mr. Franovich on the line.
25
7 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. VASAVADA: Thanks. This is Shilp 1
Vasavada on behalf of the NRC Staff. I don't have any 2
additional remarks compared to what Mike side. Enjoy 3
it all. Thank you.
4 MEMBER KIRCHNER: Okay and with that, let 5
me thank you both Staff and for those who are not 6
watching this, we have the NuScale team here. So thank 7
you for your trip to the East Coast, it's nice to see 8
you again in person.
9 And with that, I'm going to turn to Liz 10 English, and you can introduce your report and your 11 team.
12 MS. ENGLISH: Thanks. My name is Liz 13 English. I am a supervisor --
14 MEMBER KIRCHNER: You need to get your mic 15 lined up.
16 MS. ENGLISH: My name is Liz English. I'm 17 a supervisor in licensing for NuScale. Pleased to be 18 here today to present the outline of our Topical Report 19 to you.
20 With me are Thomas
- Griffith, also 21 supervisor on SDA, and Jeremiah Doyle who is the EPZ 22 technical lead for NuScale. He's the brains of the 23 bunch. Glad to have him here.
24 And I'll go to the next slide. We are very 25
8 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 grateful to the DOE for the grant that we have to do 1
this work. Next slide. I'll turn it over to you, 2
Jeremiah. Ready to roll?
3 MR. DOYLE: Thanks, Liz. I'm Jeremiah 4
Doyle, the EPZ Technical Lead as Liz mentioned. So 5
this slide here is the agenda for the meeting. We'll 6
go over the purpose, introduce the Topical Report and 7
then provide an overview of the methodology and the 8
technical basis for the methodology for sizing 9
emergency planning zones. Next slide please.
10 The purpose of this meeting is to introduce 11 the methodology and the technical basis for the 12 methodology for determining the size of the plume 13 exposure emergency planning zone around NuScale plant 14 sites. Next slide please.
15 This Topical Report is applicable just to 16 NuScale small modular reactor designs. It's 17 consistent with the technical basis in the original 18 EPZ basis in NUREG-0396 and the supporting ERA technical 19 information in WASH-1400.
20 We identify a spectrum of accident 21 sequences, evaluate the source terms of those 22 sequences, compare the dose consequences of those 23 sequences to similar dose criteria as NUREG-0396 and 24 balance this quantitative evaluation with the 25
9 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 qualitative evaluation and engineering judgment.
1 And this implements the PRA methodology 2
and supporting codes that have been established in the 3
40 years since the original EPZ basis. And we designed 4
this so that any applicant could pick up this Topical 5
Report with the same information and produce the same 6
EPZ distance. Next slide please.
7 To use the Topical Report, we have two 8
conditions of applicability in the LTR. The first is 9
that this Topical Report is only applicable to NuScale 10 SMR designs and there are five overarching criteria 11 that define what it means to be a NuScale design.
12 And this is designed to capture the high 13 level safety attributes of the design while allowing 14 for some room for design improvements in the future.
15 And then the next condition of use is on the underlying 16 technical information that's input to the methodology.
17 The first condition is that the PRA that's 18 used as input needs to be full scope and capture all 19 hazards and all operating modes. And the second 20 condition is that the PRA needs to be technically 21 acceptable for this purpose.
22 MEMBER DIMITRIJEVIC: I have a question 23 there. This is Vesna Dimitrijevic. You mean that 24 technically acceptable period or just technically 25
10 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 acceptable for this purpose?
1 MR.
DOYLE:
Technically acceptable 2
overall as in it's consistent with the existing PRA 3
standards and has been peer reviewed and has 4
demonstrated as technically acceptable and that it's 5
identified as acceptable for use in the underlying 6
application.
7 MEMBER DIMITRIJEVIC: All right because 8
you know that for some applications you don't need to 9
satisfy all higher level requirements so I just wanted 10 to make sure that you mean is just generally acceptable 11 for all that, you know, required so.
12 Okay, thanks. I understood that you said 13 that it's just review and acceptable generally not just 14 for this purpose.
15 MEMBER HALNON: Yes, this is Greg Halnon.
16 And how, the peer review befuddled me a little bit.
17 How are you going to get a peer review of a design 18 that nobody else can look at?
19 MR. DOYLE: The peer reviews of the PRA 20 itself and the, their existing PRA standards for 21 technical acceptability that outline the content and 22 scope and underlying information that's part of the 23 PRA and there's different capability categories 24 supporting that and there is peer review guidance.
25
11 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 I forget the NEI document.
1 MEMBER HALNON: Yes, I understand.
2 MR. DOYLE: Yes.
3 MEMBER HALNON: Doesn't that require 4
knowledge, people knowledgeable of the plant itself 5
and some operating experience and other things? I 6
guess, have you looked at that to make sure you can 7
say that it's going to be peer reviewed in accordance 8
with that standard?
9 MR. DOYLE: We are in the process of 10 developing the peer review, of getting that information 11 in preparation for applying this report, but it is 12 understood that not everything could be met in the 13 standards or paper plan.
14 MEMBER HALNON: I think that caveat's 15 important. But just don't say it's peer reviewed 16 because it's traditionally commonly understood as 17 certain peer review has very diverse and also very 18 focused, experienced people on it.
19 And I'm not sure you're going to be able 20 to get all of that with this. So just be, as you go 21 through, keep that in mind.
22 MR. DOYLE: Thank you. Next slide please.
23 MEMBER DIMITRIJEVIC: Greg, Matt told me 24 that they don't have people with experience in that 25
12 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 design or experience with the multi-units. But they 1
also will not carry information because, you know, all 2
of the PRA work requires procedures, lockdowns and 3
things like that so they will have also limited 4
information available and experience.
5 MEMBER HALNON: Yes, thanks, Vesna.
6 That's kind of what I was thinking. That there was 7
going to be kind of a small subset of peer review 8
actually is considered at this point.
9 MR. DOYLE: Next slide please. So the 10 NuScale methodology over all is a combination of a 11 quantitative evaluation and qualitative evaluation.
12 For the quantitative portion there's a balance of 13 deterministic evaluation of the design basis source 14 term.
15 And then the probabilistic best estimate 16 with uncertainty evaluation using a PRA and its 17 quantified sequences. And then there's an evaluation 18 of any other type of releases that may lie outside the 19 design basis or Sherman PRA and we'll talk about that 20 in more detail in the spectrum of accidents slide.
21 Once the spectrum of accidents is 22 identified, then the accidents vary as identified to 23 ensure that the appropriate dose criteria are applied.
24 And once the spectrum of accidents is identified, the 25
13 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 source term, time-dependent source term of the 1
environment for each sequence is calculated.
2 And then the dose for that sequence is 3
compare it for each sequence is compared against the 4
three dose criteria from the NUREG-0396.
5 Complementing that is a qualitative evaluation of 6
defense in depth to highlight design features and 7
operational strategies to preserve layers of defense 8
in depth in the design as well as a review and 9
disposition of key assumptions and other uncertainties 10 in the underlying PRA so that they are dispositioned 11 for the purpose of EPZ sizing. Next slide please.
12 This flowchart is just a graphical 13 representation of the quantitative portion of the 14 NuScale method. It reads from top to -- all right.
15 Hello? It's, okay. Oh, okay.
16 So the flowchart reads from top down, left 17 to right and identifies the PRA spectrum of accident 18 sequence selection process over to the incorporation 19 of the design basis input as well as the uncertainty 20 analysis of the source term and dose consequences.
21 That dash line is a conditional step in 22 the process where if certain criteria of the uncertainty 23 analysis are not satisfied, the source term and dose 24 consequence evaluations are repeated.
25
14 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 And then finally, the justified source term 1
and dose consequences are applied to the three dose 2
criteria and the plume exposure emergency planning zone 3
is the largest distance from the plant at which all 4
three criteria are met simultaneously.
5 MEMBER KIRCHNER: Let me ask a question 6
about the dotted line that you just highlighted. What 7
would change when you went back and iterated, are you 8
going to get to that? I mean, you do this analysis 9
and if it's not acceptable, then you go back and do 10 the source term evaluation again?
11 That's a misinterpretation by my, on my 12 part, but --
13 MR. DOYLE: That is correct. So the idea 14 is to perform an uncertainty analysis of the most 15 probable less severe and more severe PRA sequences that 16 are evaluated using a parametric evaluation of the 17 severe accident inputs and the dose consequence inputs.
18 And any inputs that are identified as 19 important to the final dose consequence, which is 5 20 percent of the, at least 5 percent of the uncertainty 21 regression metric used than those important perimeters 22 need to be justified as best as submitted.
23 And if they cannot be justified, a 24 conservative value must be justified and that 25
15 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 conservative value would be used and the evaluation 1
would be repeated with that value.
2 MR. KIRCHNER: Thank you.
3 CHAIRMAN REMPE: So along those lines, 4
again I don't -- so just tell me to shut up if I'm getting 5
into something that's proprietary. But there was some 6
information regarding how the vessel failure assumption 7
would be invoked that to me (audio interference) more 8
thorough validation for evaluation or assessments, the 9
code that you assume for when you implement this?
10 MR. DOYLE: Part of the methodology is 11 providing some basis for consequence, for confidence 12 in the MELCOR results that MELCOR's used. And we 13 describe how to do a code to code comparison up to core 14 damage.
15 But specifically for any type of 16 containment phenomena that would be evaluated as part 17 of the underlying PRA. The EPZ methodology is not 18 modifying the underlying PRA, it's just using that 19 information and so.
20 CHAIRMAN REMPE: Yes, you're using it for 21 a different application than what was done for the 22 original. In this case, the CD, but of course, this 23 will be all for a SDA or something I suppose. But go 24 ahead.
25
16 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. DOYLE: Right. So the acceptability 1
of the MELCOR evaluations would be, would fall under 2
the peer review aspect of the underlying PRA. And if, 3
there's, again this is where the other risk section 4
also comes into play as a capture.
5 We specifically talking the methodology 6
about severe accident phenomena like a containment 7
failure and that it's expected to be evaluated in the 8
underlying PRA.
9 But if it's not and there or there's not 10 confidence, that these releases would be demonstrated 11 to either meet the dose criteria or would be bounded 12 by other sequences that are captured in the spectrum 13 of accidents from the screening process.
14 So in some form, the doses will be evaluated 15 from an intact containment or a containment bypass 16 event. And if there's uncertainty as to which, as to 17 the status of containment, the methodology requires 18 the user to evaluate both the intact containment and 19 the containment bypass version of the accident.
20 CHAIRMAN REMPE: I'm concerned about the 21 assumption about the size of the hole for containment 22 value. And it's stated that the size is conservative 23 and I, if I were viewing it either as a peer review 24 or the Staff, I'd be wanting to see the justification 25
17 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 for that.
1 MR. DOYLE: Okay. I'm not sure I 2
understand the --
3 CHAIRMAN REMPE: Can you --
4 MR. DOYLE: -- full --
5 CHAIRMAN REMPE: -- talk more specifically 6
7 MR. DOYLE: -- or hole, okay.
8 CHAIRMAN REMPE: -- or can we get into --
9 although I don't think it's in your slides, but I can 10 bring up the report --
11 MR. DOYLE: Okay.
12 CHAIRMAN REMPE: -- assumption and all 13 that, but I just am curious if there was some additional 14 validation of some of the -- in the PRA, they got down 15 below frequency and I know the Staff did not go all 16 the way with their MELCOR validation to containment 17 failure because there's, you get into a lot more 18 uncertainties.
19 And they did it for a what, up to vessel 20 failure I think or a certain point and they didn't go 21 all the way and they said, okay, it's good enough and 22 we let it go.
23 But now you're taking those results in a 24 more severe accidents and you're using them to come 25
18 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 up with your EPZ. And I just am wondering if somebody's 1
going to do some more assessment on the validity of 2
the code for that application.
3 MR. DOYLE: Okay, understood. Next slide 4
please. So the first step is the identification of 5
the spectrum of accident sequences. Consistent with 6
NUREG-0396, the design basis source term and the PRA 7
accident sequences are evaluated for inclusion in the 8
spectrum of accidents.
9 The design basis source term in the NuScale 10 design is at the core damage design basis source term 11 for offsite builds consequences is a combination of 12 intact containment beyond design basis accidents.
13 It's a
surrogate accident with 14 characteristics from multiple beyond design basis 15 accidents. This viewed accident from the PRA are 16 identified for inclusion based on sequence frequency 17 so non-seismic, single module, multimodule sequences 18 are retained in the EPZ basis if they have a core damage 19 frequency greater than ten to the minus seven per year.
20 And this frequency captures the complete 21 spectrum of accidents in the underlying basis in 22 NUREG-0396. And the use of CDF as the metric rather 23 than release frequency also adds some conservatism to 24 the screening process.
25
19 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 And additionally, following the initial 1
best-estimate screening, an uncertainty analysis of 2
the screening is performed using the 95th percentile 3
values for screened-out sequences.
4 The consistent with NUREG-1855, if a 5
sequence that initially screens out is within an order 6
of magnitude of the screening criteria, then if the 7
mean-best estimate CDF value is within an order of 8
magnitude, then the 95th percentile CDF is compared 9
to the ten to minus seven threshold.
10 And if that sequence 95th percentile value 11 is above the screening threshold, it's retained for 12 analysis in the spectrum of accident sequences. And 13 this ensures that we're not missing any cliff edge 14 sequences beyond that screening limit.
15 Following the identification of the design 16 basis, source term and PRA accidents, other releases 17 are identified. One specific example that lies outside 18 the design basis source term in PRA is an accident 19 involving failure of the single failure-proof crane 20 where the upper half of the module is dropped onto the 21 open bottom half of the module and the refueling tool.
22 In this instance, the release wouldn't meet 23 the core damage definition of the PRA because the fuel 24 is not over heating, but there is mechanical damage 25
20 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 and there is the potential for gap release from the 1
fuel.
2 And so that release would be identified 3
and evaluated as part of the EPZ method. And then 4
finally, once all the accident sequences have been 5
identified, their severity is determined consistent 6
with NUREG-0396.
7 There's two categories less severe and more 8
severe that are differentiated based on the level of 9
atmospheric release and less severe actions are 10 considered to be those with the containment intact.
11 And containment failure bypass accidents 12 are more severe. And if the containment status is 13 uncertain, you evaluate both intact containment and 14 bypass versions of the accident. Next slide please.
15 MEMBER KIRCHNER: One question on that 16 last set of bullets. So if you have a breach of 17 containment, whatever reason, do you take any credit 18 for scrubbing or do you assume that containment breach 19 is above the water level on all the gaseous fission 20 products that are released?
21 MR. DOYLE: So for the module drop accident 22 which is horizontal under the surface and we have 23 confidence that it would be under the surface, it is 24 scrubbed.
25
21 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 But for other accidents, postulated 1
accidents from an upright module, that's assumed to 2
be above the pool surface.
3 MEMBER KIRCHNER: Thank you.
4 MR.
DOYLE:
So following the 5
identification of the spectrum of accident sequences, 6
the time dependent source terms are calculated using 7
a severe accident code like MELCOR, for example.
8 And it's expected that these severe 9
accident calculations will have already been performed 10 as part of the PRA. And these source term evaluations 11 will then feed into the off-site dose consequences.
12 So for the design basis source term, it 13 would be evaluated just as the release from containment 14 to the environment with no other credit for any other 15 type of retention or hold up.
16 But for the less severe, more severe beyond 17 design basis accidents, credit for additional scrubbing 18 or retention outside of the containment like in the 19 reactor building could be credited in, through separate 20 effects models from MELCOR.
21 And then these environmental source terms 22 will be fed into MACCS for comparison against the three 23 dose criteria. Criteria A for design basis source 24 terms is that the total effective dose equivalent is 25
22 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 less than one REM or mean, meteorology conditions and 1
five REM for 95th percentile conditions for 96-hour 2
exposure.
3 The Criterion B is for less severe 4
accidents. The TEDE dose would be less than one REM 5
mean in the 95th percentile over 96-hour exposure.
6 And the Criterion C is that the more severe accidents 7
would demonstrate a reduction in early health effects 8
by comparison to a 200 REM threshold using acute 9
whole-body dose.
10 Consistent with NUREG-0396, the 11 recommended defaults for performing this modeling in 12 the methodology is that the individuals, the 13 individual, the dose receptor is located outdoors and 14 they're stationary.
15 They are in the direction of maximum 16 exposure. These receptors are located at least 50 17 meters from the reactor building and as far out as ten 18 miles to get the full spectrum of distances there.
19 And these receptors do not undergo any 20 sheltering, relocation or evacuation, no protective 21 actions and all the major short-term dose pathways are 22 evaluated.
23 And there's no shielding from these 24 different pathways with the exception of groundshine 25
23 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 which is recommended to have a 70, sorry, a 30 percent 1
shielding due to just natural variations of being 2
located on a planar surface and ground variations.
3 And that's all consistent with the 4
valuation in NUREG-0396. And then following this 5
evaluation of the source term and dose, that's when 6
we get to the evaluation of uncertainty that we 7
discussed on the flow chart slide.
8 CHAIRMAN REMPE: A good place to bring up 9
this question. Your report states that it expands on 10 the NEI methodology. Right?
11 MR. DOYLE: Correct.
12 CHAIRMAN REMPE: And one of the things I 13 like about the NEI methodology that you actually cited 14 in your report is that it mentions that the required 15 site emergency plans will provide a base for expanding 16 response efforts, if necessary, in accordance with 17 regulatory guidance so as to provide an additional layer 18 of defense and data.
19 And that away, it can, we all know that 20 PRAs do, nobody knows completely what kind of accidents 21 might occur with a first of a kind reactor. I kind 22 of felt more comfortable seeing that.
23 So how will this methodology be used to 24 or what's your vision on how you'll accommodate that 25
24 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 part of the NEI methodology? And I'm also curious on 1
how the Staff will ensure that that's done in the review 2
process.
3 MR. DOYLE: Well part of this methodology 4
is that we are just establishing the distance for the 5
emergency planning zone and outside of this plume 6
exposure distance, you know, traditionally there are 7
avenues for expanding this protection.
8 And because we're not evaluating the every 9
sequence individually, that could potentially happen.
10 But establishing a distance where it is, you know, 11 likely imprudent to have preplanned actions and having 12 the base for expansion for those.
13 So that's not something that's very 14 detailed in the methodology, but would come out of 15 implementing whatever site, whatever EPZ distance would 16 come out of the method.
17 CHAIRMAN REMPE: Some design developers 18 which may not be your organization, want to put very 19 small cladding zone site boundary. And so again I'm 20 thinking about one of the managers at SEPCO saying that 21 it's not a good time to come up with an emergency plan 22 during the middle of an accident.
23 So I really like that part of the NEI 24 methodology and I'm just kind of thinking about in the 25
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 future. I realize this is just a topical report, but 1
I'm just kind of thinking that some more acknowledgement 2
-- I'm glad it was in your Topical Report, but I'd like 3
to really make sure that somebody thinks about that 4
in the future and make sure that it gets implemented.
5 Because if you reduce the emergency 6
planning zone because you don't want to have drills, 7
I'd sure like to see that you've thought about how, 8
you know, what would need to be done. Does that make 9
sense where I'm coming from?
10 MR. DOYLE: Yes, understood. Thank you 11 for that feedback. Next slide please. So following 12 the quantitative evaluation and the establishment of 13 a specific plume exposure EPZ distance around the plant, 14 that there's a qualitative evaluation of defense and 15 depth and a review of the PRA uncertainties to provide 16 further confidence in the PRA risk numbers and the 17 qualitative or quantitative evaluation itself.
18 So the defense and depth evaluation will 19 be performed to confirm that the design meets the 20 guidance and INSAG-10 and Reg Guide of 1.174 to 21 demonstrate the five attributes in INSAG-10 and the 22 seven in Reg 1.174 of defense and depth.
23 I highlight these design features and SSCs 24 that are available and capable to prevent accidents 25
26 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 and mitigate consequences should they occur. And then 1
it confirms that these, that these attributes exist 2
and that they're functional and that they confirm the 3
low risk in sites from the PRA.
4 The review of PRA uncertainties is 5
performed consistent with, you know, really any 6
risk-informed application of the PRA to address that 7
the underlying assumptions and model uncertainty and 8
completeness uncertainty in the PRA that were evaluated 9
for the specific purpose of that application do not 10 have any impacts or those impacts are evaluated and 11 are evaluated in the context of EPZ sizing. Next slide 12 please.
13 So in summary, the NuScale Topical Report 14 presents a method for sizing emergency, new emergency 15 planning zones that's consistent with the underlying 16 basis in NUREG-0396 and WASH-1400s and it provides the 17 same level of protection to the public that the existing 18 EPZs provide around operating plants and its limited 19 applicability to a NuScale SMR designs only. And I 20 believe that's the last slide.
21 MEMBER HALNON: I just had, this is Greg 22 Halnon. I don't know if this question is valid, but 23 you know, we just went through the 50.160 Emergency 24 Planning Rule aspect. If you overlaid this on top of 25
27 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 that, could this maneuvering be used under that rule?
1 MR. DOYLE: Yes, this is designed to be 2
a stand-alone methodology outside the existing guidance 3
and, or the existing regulations and the proposed 4
regulations.
5 But overlaying our method with the guidance 6
in Appendix A for the new rulemaking, we do meet those 7
major points of that methodology, that high level --
8 MEMBER HALNON: Kind of a plug and play 9
type of thing?
10 MR. DOYLE: Right.
11 MEMBER HALNON: Thanks.
12 MEMBER BIER: One other question. Very 13 early on, I think you said that any sequence will load 14 into minus seven would not be used in the calculation 15 of the then, some of these exceptional cases. Is that 16 correct?
17 MR.
DOYLE:
That's correct for a
18 non-seismic sequences.
19 MEMBER BIER: Okay. Have you thought 20 about just what if you have so many zillion sequences 21 at ten to the minus nine that they add up to be worth 22 including overall?
23 MR. DOYLE: That point is not specifically 24 addressed in the Topical.
25
28 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MEMBER BIER: Okay. I mean it may be that, 1
you know, if your design is simple enough, maybe you 2
just don't have that many zillion sequences in the PRA.
3 I haven't looked at it but for LWR PRAs, that concerned 4
me.
5 MEMBER KIRCHNER: Jeremiah, I am just 6
looking ahead to the closed session. Give you some 7
to think about what I'm going to ask. But I think it's 8
important to share for the public.
9 We would be particularly interested in how 10 you're dealing with, as your report identifies, seismic 11 as being one of the bigger concerns and drivers in this 12 analysis.
13 And how you handle seismic event that could 14 impact all the modules up to 12 and, you know, simple 15 thinking would suggest that if a seismic event damages 16 one module, it's got a high probability of damaging 17 identical modules even that maybe ones down for 18 refueling at the time.
19 You could have a common cause failure in 20 the systems. Can you linearly sum up the source terms 21 or --? I would like to hear a little bit more about 22 how you address the multimode, multimodule source term 23 and how you deal with the uncertainty in the seismic 24 probabilities and how that impacts your results.
25
29 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. DOYLE: Okay. I can discuss the 1
multimodule portion, but I'll hold the seismic for the 2
closed portion of the meeting. But broadly, we have 3
a methodology for identifying multimodule sequences 4
from any hazard not just seismic.
5 And it involves looking at the initiating 6
event for a given sequence and then identifying does 7
that initiating event impact multiple modules, for 8
example, loss of off-site power.
9 And then would that initiating event either 10 compromise the safe shut down functions of multiple 11 modules like ECCS and DHRS or could it physically 12 propagate to other modules like a hypothetical module 13 drop that tips over and strikes another module.
14 And so in those cases where you end up with 15 a sequence where there's say six modules that are 16 experiencing the same accident sequence, in the dose 17 calculations we would evaluate six cores with the same 18 timing and release fractions.
19 In the case where one module is, for 20 example, horizontal under the pool and there may be 21 two vertical modules that are intact containment or 22 bypass, the, we require the use of the MACCS code in 23 the method.
24 And that allows for multiple difference 25
30 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 source terms to be evaluated simultaneously. And the 1
method would call for the scrubbed horizontal module 2
source term to be added to the containment bypass or 3
intact containment source terms.
4 And if there was one horizontal module and 5
two intact containments, you would evaluate three 6
cores. One core to the, or one core for the horizontal 7
and two for the intact containment. But yes, it would 8
be explicitly addressed --
9 DR. BLEY: Yes, this is Dennis.
10 MR. DOYLE: -- in this calculation.
11 DR. BLEY: Yes, this is Dennis.
12 MEMBER KIRCHNER: By the way, let me, I 13 think I hear Dennis. For the record, we have our 14 consultants, Dennis Bley and Stephen Schultz with us 15 for our meeting today. Go ahead, Dennis.
16 DR. BLEY: Yes, thanks. It sounds like 17 you've done more thinking and more work on the 18 multimodule problem than you had done at the time of 19 the design cert. Is that true and when are we going 20 to see actually some details we can read about that?
21 MR. DOYLE: So the insights I was 22 discussing are from an audit example calculation that 23 we performed for the NRC Staff in support of the review 24 of the Topical Report.
25
31 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 It's based on the multimodule PRA that we 1
submitted with the design certification. So that's 2
the extent of how we've evaluated multi-modules so far 3
and nothing new since the design certification.
4 DR. BLEY: Okay.
5 MEMBER DIMITRIJEVIC: Well that true yes.
6 Dennis, you go.
7 DR. BLEY: Well I just wanted to ask that 8
response from the audit, is that in one of the RAIs 9
that I haven't read? Is there a place we can go read 10 about that in more detail?
11 MR. DOYLE: The multimodule analysis 12 wasn't specifically part of an RAI question. And I 13 don't believe that's, that information's in an RAI.
14 It was discussed in the audit.
15 DR. BLEY: Oh, it was, just in the audit.
16 Okay. Thank you. I'm sorry, Vesna, go ahead.
17 MEMBER DIMITRIJEVIC: Well my comment was 18 that in the design certification the, you know, that 19 the accident with the unit was, you know, in the 20 horizontal were not counted for that and the latitude 21 too for larger reasons.
22 So obviously this is something different, 23 you know, since you're counting them for this smaller 24 releases I assume so. Therefore, that's a different 25
32 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 part of the difference with design period. I mean with 1
the design certification period. I mean, at least the 2
design certification PRA Level 2.
3 MR. DOYLE: In the design certification, 4
yes, we did evaluate the dose consequences of the module 5
drop and demonstrated that did not meet our larger lease 6
criteria.
7 But in that accident, the containment was 8
assumed to fail. And in the example calculation we 9
preformed, we applied that same source term but to the 10 EPZ dose criteria and not to the larger lease criteria 11 from the DCA.
12 MEMBER DIMITRIJEVIC: Well, therefore, 13 those sequences are not in the design certification 14 period. Right?
15 MR. DOYLE: Those sequences were evaluated 16 in the environmental report of the design 17 certification.
18 MEMBER DIMITRIJEVIC: I see.
19 MR. DOYLE: And the module drop did 20 contribute to the core damage frequency, but it was 21 not a contributor to the larger lease frequency.
22 MEMBER DIMITRIJEVIC:
Right.
And 23 therefore it was not counted in the core damage 24 frequency because it was not the contributor. So okay, 25
33 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 so this settle that and this analyzes from your 1
environmental report. Okay.
2 DR. SCHULTZ: Jeremiah, this is Steve 3
Shultz. Question. You mentioned as you made your 4
presentation that the methodology that you've used is 5
MELCOR methodology, but that other methods could be 6
used.
7 That an Applicant, in doing their PRA, 8
their overall evaluation, could use other methods.
9 Is that what you're implying?
10 MR. DOYLE: Yes, we did not limit the 11 methodology to one specific code. Like for example, 12 if an applicant wanted to use the MACCS code, they could 13 use that for their severe accident evaluations.
14 But since NuScale used MELCOR, we used that 15 as the example in the Topical, but it's not required.
16 DR. SCHULTZ: But then that would have to 17 be re-evaluated by the Staff of the application.
18 MR. DOYLE: Correct.
19 DR. SCHULTZ: The MACCS code though is 20 specified at least as provided by the Staff as a tool 21 that must be used in the application in the safety 22 evaluation that they performed. Is that correct?
23 MR.
DOYLE:
That's correct.
The 24 methodology requires MACCS to be used as the dose 25
34 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 consequence code.
1 DR. SCHULTZ: Thank you.
2 MEMBER KIRCHNER:
Other members?
3 Questions?
4 CHAIRMAN REMPE: Just a comment. We are 5
actually in the full committee
- meeting, not 6
subcommittee meeting. I just noticed that your slides 7
and the Staff slides say subcommittee meeting and it's 8
not a big deal, but I wanted everyone to be aware of 9
it. I know it's confusing.
10 We had originally you guys scheduled for 11 a subcommittee meeting and this is a full committee 12 meeting so.
13 MEMBER KIRCHNER: One comment I was going 14 to make on that subject is that since you have the full 15 committee, and the full committee is here, this is a 16 good time to ask especially during the closed session, 17 any of the harder questions you have because we are 18 going to look to writing a letter report on this and 19 the Staff's review in our October full committee 20 meeting.
21 If we can answer all of your questions, 22 we can have a very brief summary presentation --
23 CHAIRMAN REMPE: Or even have it. It's 24 up to you.
25
35 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MEMBER KIRCHNER: -- or possibly none for 1
the October meeting so like please fire away now while 2
we have the NuScale people here as well as the Staff.
3 So any further questions or you want to hold some 4
questions for the closed session?
5 Okay, thank you, Liz. Thank you, 6
Jeremiah. I tell you what, I think we're ready for 7
the Staff --
8 MR. VASAVADA: Yes.
9 MEMBER KIRCHNER: -- presentations.
10 MR. VASAVADA: Thank you. So I have a 11 clarification question. So this is not a subcommittee 12 meeting?
13 CHAIR REMPE: We are in a full committee.
14 Again, we had scheduled, I'm sorry --
15 MEMBER KIRCHNER: You might want to turn 16 your microphone on.
17 CHAIR REMPE: We are in full committee.
18 We had scheduled something earlier in September as an 19 extra session to accommodate your schedule and then 20 we are hoping we can accomplish all of this during full 21 committee week.
22 And so that's why we're all saying you may 23 not have to present again.
24 MR. VASAVADA: Okay.
25
36 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 CHAIRMAN REMPE: But it's up to you all.
1 MR. VASAVADA: There is --
2 MEMBER KIRCHNER: So we are going to ask 3
you to pick up speed so we can move the Staff into your 4
chairs. And thank you for your presentation.
5 MR. DOYLE: Sure.
6 (Off record comments.)
7 MEMBER KIRCHNER: I don't know if you can 8
see this, but we have a placard there for you and it 9
says you're remote.
10 MS. SCHILLER: Good afternoon. My name 11 is Alina Schiller. I am a project manager in the NRC 12 Office of Nuclear Reactor Regulation, Division of New 13 and Renewed Licenses, New Reactor Licensing Branch.
14 Thank you. Thank you, Shilp, for sharing 15 your screen. I would like to thank the ACRS 16 Subcommittee and Full Committee for NuScale Power, LLC 17 and the general public for entertaining the NRC for 18 the presentation of the Staff safety evaluation of 19 NuScale's Licensing Topical Report titled Methodology 20 for Establishing the Technical Basis for Plume Exposure 21 Emergency Planning Zones at NuScale's small modular 22 reactor plant sites Revision 3. Next slide please.
23 In August 2020, NuScale submitted Revision 24 2 of this Topical Report to the NRC. The NRC showed 25
37 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 two requests for additional information, RAIs, to 1
NuScale in April 2021.
2 Originally the Topical Report Revision 2 3
was applicable to light water small modular reactors 4
and non-light water reactors. In May 2021, in response 5
to one of the two RAIs, NuScale removed applicability 6
to non-light water reactors.
7 From November 2021 to April 2022, NRC 8
performed the regulatory audit as part of its review 9
of the methodology in Revision 2. In June 2022, NuScale 10 provided response to the 2nd RAI and submitted Revision 11 3 of the Topical Report which is applicable only to 12 the NRC design and its derivatives and which 13 incorporated the responses to the two RAIs.
14 We are here today to discuss the Staff's 15 advanced safety evaluation of the Topical Report. Next 16 slide please. The NRC Staff reviewers are Marie 17 Pohida, the lead technical reviewer with the PRA 18 Licensing Branch C in the Division of Risk Assessment 19 in NRR, Shilp Vasavada, the acting branch chief of the 20 PRA Licensing Branch C, Elijah Dickson from the 21 Radiation Protection and Consequence Branch, Raymond 22 Hoffman with the Reactor Licensing Branch in the Office 23 of Nuclear Security and Incident Response Division of 24 Preparedness and Response and Todd Smith with the 25
38 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Division of Preparedness and Response and Answer.
1 The presenters today are Marie Pohida, 2
Shilp Vasavada and Elijah Dickson. I'm the project 3
manager for this Topical Report supported by Senior 4
Project Manager Getachew Tesfaye.
5 Now I'm turning over to Marie Pohida, the 6
NRC first presenter.
7 MS. POHIDA: Thank you, Alina. First I'd 8
like to discuss the outline of our presentation.
9 First, we're going to discuss the regulatory and 10 technical basis for the Staff's evaluation.
11 Then we're going to go through an overview 12 of the Topical Report methodology. We will then 13 discuss the dose-distance criteria and figures of 14 merit.
15 We will then discuss the source term and 16 consequence assessment and then the screening of PRA 17 sequences. We will highlight the treatment of 18 uncertainty and the conditions of use for this Topical 19 Report. Next slide please, Shilp.
20 First, I'd like to discuss this, the 21 regulatory and technical basis for our valuation. Our 22 basis is 10 CFR 50.47 on emergency plans, 10 CFR Part 23 50, Appendix E, emergency planning and preparedness 24 and 10 CFR Part 20, standards for protection against 25
39 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 radiation.
1 The documents that I'm going to discuss 2
below, all the ADAMS information where the documents 3
can be found in the reference slide at the back of the 4
public presentation.
5 So our next document that we relied in is 6
NUREG-0396. It is the planning basis of emergency 7
response plans for light water reactors. And it is 8
the technical basis for the ten-mile EPZ and it is also 9
the technical basis for the draft final EP rule for 10 small modular reactors and other nuclear technologies.
11 This review was informed by the Commission 12 PRA policy statement of 1995. It was also informed 13 by the SRM SECY 98-144 and it's a white paper on risk 14 informed and performance-based regulations.
15 This review was informed by Reg Guide 1.174 16 which is an approach for using PRA in risk-informed 17 decisions on changes to the licensing basis and finally, 18 it was informed by Reg Guide 1.20 which is the, outlines 19 the technical acceptability of PRA results for 20 risk-informed activities. Next slide please.
21 I would like to discuss NUREG 0396 from 22 1978. It identifies the purpose of the emergency 23 planning zone. And it's the area within which plume 24 protected actions may be necessary to provide dose 25
40 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 savings in the event of radiological release.
1 It is the technical basis for our, the 2
current prescribed plume exposure pathway EPZ radius 3
of ten miles. And if you look at NUREG 0396, it states 4
that the taskforce reviewed the dose distance curves 5
1 NUREG 0396 and they can be found in Figure I-11.
6 And they concluded that plume accidents 7
can be severe, but the probability of large doses drops 8
off substantially about ten miles from the reactor.
9 You know, based on the review of licensing 10 basis events and, I mean, this report was based on a 11 review of licensing basis events and a spectrum of 12 accident sequences from WASH-1400.
13 And these included BWR and PWR accident 14 release categories from WASH-1400. And Elijah will 15 present details of this later in the presentation.
16 I'd like to briefly discuss the Staff's method of 17 review.
18 It's consistent with a technical basis of 19 NUREG 0396 and it's also consistent with risk-informed 20 decision making and use of PRA in current risk-informed 21 applications.
22 And our review was supported by a 23 regulatory audit where NuScale provided an example 24 calculation using their design certification PRA and 25
41 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 their SAMDA analysis which has source terms and release 1
frequencies to produce an example dose distance curve 2
demonstrating the entire methodology.
3 I would also just like to briefly discuss 4
our review of the applicability of the NuScale EPZ TR 5
methodology. It's only applicable to the NuScale 6
design and its derivatives which includes the standard 7
design approval.
8 And if you look in Section 2.5.1 of the 9
Topical Report, it provides high level design 10 characteristics that determine the applicability. You 11 know, as an example, for it, you'll see that it's 12 applicable for a small modular integral pressurized 13 light water reactor.
14 And the reactor modules are consisted, 15 composed of a reactor core, a primary coolant loop, 16 depressurizer and steam generators within a reactor 17 vessel which are housed within a containment vessel 18 that is normally operated in sub-atmospheric 19 conditions.
20 Additional characteristics like these can 21 be found in the SER. We find that these limitations 22 are acceptable because we believe these high level 23 design characteristics are capable of identifying the 24 NuScale design with features and the risk profile that 25
42 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 we considered in our review.
1 And at this, I'd like to turn over to Elijah 2
to discuss the dose distance criteria in more detail.
3 And I'll break here if there's any questions. All 4
right, thank you. Turn it over to Elijah.
5 MR. DICKSON: Thank you, Marie. So on 6
Slide 9 here, this slide discusses the Staff's approach 7
in reviewing the source term consequence portions of 8
the Topical Report which include performing review of 9
historical documents to familiarize ourselves on the 10 topic, current research analysis and results from other 11 organizations such as the NRC, NEI, EPRI as well as 12 the NuScale environmental report and other 13 organizations responsible for radiation protection 14 recommendations.
15 Specially, we paid careful attention to 16 the vintages of systems of dosimetry that were utilized 17 between NUREG 0396 and the Topical Report, the 18 radiological criteria as well as the radiological 19 consequence analysis methods and assumptions.
20 We did perform limited analyses using the 21 MACCS code, using assumptions drawn from WASH-1400 to 22 better understand the presented dose-based criteria 23 presented in NUREG 0396 and presented in the Topical 24 Report as well.
25
43 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Now before moving on to the next slide, 1
I'd like to provide some context in how the Staff 2
reviewed and compared the proposed methodologies and 3
criteria to the technical basis of the ten mile EPZ 4
described in NUREG 0396.
5 In doing so, you'll see that the Topical 6
Report is consistent with the robust analyses and 7
methods and intent of the current ten mile EPZ. NUREG 8
0396 captures the task force review analysis and 9
decision making insights in developing the planning 10 basis for a radiologically emergency response plans.
11 This includes members at all levels of 12 government, local, state and federal members. And here 13 they introduce the concept of generic emergency 14 planning zones as a basis for the planning for response 15 actions which will result in dose savings in the 16 vicinities of new purpose facilities in the event of 17 a serious accident.
18 A selection of the current ten mile EPZ 19 was chosen based on professional judgment considering 20 a variety of lines of evidence rather than being based 21 on a specific prescribed radiological consequence 22 assessment methodology.
23 The task force recommended considering 24 information from a spectrum of accidents which does 25
44 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 include design basis accidents and a range of beyond 1
design basis accidents typically referred to as Class 2
9 accidents.
3 As defined in NUREG 0396, Class 9 accidents 4
are considered to be so low in probability as to not 5
require specific additional provisions in the design 6
of the reactor facility.
7 Such accidents would include sequences of 8
successive failures of more severe than those 9
postulated for the purposes of establishing the design 10 basis for protective systems and engineered safety 11 features.
12 With that, I would like you, to point your 13 attention to in your review of the Topical Report as 14 well as reviewing NUREG 0396, is specifically to 15 Appendix I of NUREG 0396.
16 It does contain a wealth of information 17 and insights from the task force and I'll be referring 18 back to it throughout my portion of the presentation.
19 Specifically, Appendix I of NUREG 0396 describes the 20 various rationales for establishing the planning basis 21 which includes risk, probability, cost effectiveness 22 and consequence spectrum.
23 The study based the rationale for the 24 planning basis on a special with consequences tempered 25
45 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 by probability and NUREG 0396 also states that the 1
accident probability is important and does have a place 2
in the terms of evaluating the range of consequences 3
from accident sequences and setting some reasonable 4
bounds on a planning basis.
5 As such conditional probabilities of 6
various consequences were used to provide perspective 7
for critical doses of concern for emergency response 8
planners as were their probabilities.
9 Of most importance, the Staff reviewed, 10 in depth, NUREG 0396 dose distance curves that were 11 generated for design basis accidents and those are the 12 probability exceedance curves for the beyond design 13 basis accidents.
14 They also analyzed a number of other 15 important factors important for emergency planning 16 purposes such as accident progression, timing, source 17 terms and estimated arrival times.
18 With that, I'd go on to Slide 10 please.
19 Okay. This slide summarizes and presents the Topical 20 Reports of dose distance criteria and figures of merit.
21 For the most part, Topical Report follows 22 the recommendations of the Task Force for the assessed 23 design basis accidents and beyond design basis 24 accidents derived from their PRAs, the accessed 25
46 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 accident progression and timeliness.
1 They derive source terms and then perform 2
the applicable radiological consequence analyses.
3 Probably one of the primary differences between what 4
was done in NUREG 0396 back in the late '70s and with 5
being presented in the Topical Report, is that they 6
do utilize different systems of dosimetry.
7 And they do utilize updated tools and 8
analyses and updated codes and programs. So with that, 9
let me describe this table. It presents three 10 criteria.
11 Listed in each row in, it presents three 12 criteria and then listed in each row in the middle column 13 are the analyses used to derive the source term and 14 then lastly the figures of merit within each column.
15 The first row is Criterion A, specific to 16 design basis accidents, Criterion B and Criterion C, 17 rows 2 and 3 are for beyond basis accidents. As you 18 move from Criterion A to Criterion C, the analyses 19 become increasingly more mechanistic and rely on 20 additional realism.
21 So for Criterion A, I'll first discuss 22 insights from NUREG 0396. During that time when 23 they're developing the planning basis, the task force 24 had assessed already cited nuclear facilities safety 25
47 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 analysis reports.
1 Specifically, the accident analyses that 2
were performed to demonstrate compliance with the Part 3
100 citing criteria, that is the 25 REM over a two-hour 4
period, they re-analyzed a handful of those analyses 5
and they determined at what distance you would compute 6
consequences less than one REM.
7 You can review these results, these are 8
the dose distance curves or dose distance analyses in 9
Tables I-2 and Figures I-1. The title of this figure 10 would be the upper bound plume exposure pathway 11 projected doses based off of 10cc per part of Part 12 100.11.
13 And what they found was that around ten 14 miles the doses would drop down below one REM with an 15 estimated time of arrival of that plume around five 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />.
17 So this was important information in regard 18 to emergency response planning. Not only, of course, 19 knowing what the projected computed doses are at 20 different RADI from the facility, but also what the 21 estimated time of arrival of that source term or plume 22 would be at that location.
23 Now we'll talk about the Topical Report.
24 The Topical Report methodology is generally consistent 25
48 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 with NUREG 0396 in that the EPZ should encompass those 1
areas in which projected doses from design basis access 2
could exceed early phase PAGs.
3 The source term that would be derived are 4
those that you would typically see from NUREG 0800 which 5
is a standard review plan, Chapter 15 accident analyses.
6 These are very stylized analyses and 7
deterministic in nature in which you're only applying, 8
for the most part, safety related structure systems 9
and components that meet single failure criteria and 10 do not rely on offsite power to mitigate the source 11 term and they do not consider accident frequency.
12 They are deterministic in nature. The 13 criteria used, the figures of merit criteria is one 14 to five REM total effective dose over 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> which 15 is consistent with the EPA PAG manuals early phase PAGs.
16 Now on to Criterion B and Criterion C.
17 These are the beyond design basis accident sequences 18 derived from the PRA. First let's talk about some 19 insights from NUREG 0396.
20 The task force was very focused on the more 21 severe accident sequence that involved large releases.
22 Primary consideration was given to prevention of early 23 health effects.
24 Early health effects that they had looked 25
49 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 at were one to five REM which corresponded to the lower 1
range of paths. Fifty REM corresponded to doses at 2
early, which early illnesses could occur.
3 And then 20 REM whole-body acute dose is 4
a dose at which significant early injuries would occur.
5 They generated a series of probability exceedance 6
curves for critical dose values at which emergency 7
planners would be concerned with.
8 Specifically, these exceedance curves were 9
generated for the source term frequency weighted and 10 in some yield the resulting curves. The primary curves 11 that were focused very heavily on by the task force 12 in NUREG 0396 were Figures I-11, I-12 and I-13.
13 And Marie had discussed this as well. As 14 quoted in NUREG 0396, it can be seen from Figure I-11.
15 Core melt accidents can be severe, but the probability 16 of large doses drops off substantially at about ten 17 miles from the reactor.
18 Such conclusions can be reached by 19 evaluating the other critical organ and lung dose 20 values. And these are in respective figures of I-12 21 and I-13.
22 As such, the shape of the curve itself that 23 you see in these exceedance frequency curves is very 24 important in the decision-making process for the 25
50 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 current ten-mile emergency planning zone.
1 I'll now go on to Criterion B and Criterion 2
C as they presented in the Topical Report. The EPZ 3
for Criterion B, the EPZ should encompass those areas 4
in which consequences of less severe accidents that 5
is contained and intact, sequences could exceed the 6
early phase PAG.
7 In this, for this criteria, the source term 8
that would be derived would be derived from PRA specific 9
accident sequences or BINs utilizing, for instance, 10 the MELCOR code to derive source terms which would then 11 utilize additional mitigating the design features and 12 operator actions.
13 The figures of merit that they would be 14 compared to would be the one to five REM total effective 15 dose equivalent evaluated over a four-day timeframe 16 which is consistent with the EPA PAG manual.
17 On to Criterion C. The EPZ should be a 18 sufficient size to provide for substantial reduction 19 early health effects in the event of more severe 20 accident sequences.
21 The source terms that would be derived for 22 these analyses would also be PRA specific accident 23 sequences or BINs of accident sequences. In this case 24 utilizing the MELCOR code and also perhaps maybe 25
51 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 separate effects models to derive source terms which 1
would utilize additional mitigating design features 2
or phenomena and it would include operator actions.
3 The figure of merit that these would be 4
compared to would be the 200 REM acute dose metric based 5
on substantial reductions of early health effects.
6 And this too is consistent with NUREG 0396.
7 NuScale also has an acceptance criteria considered 8
proprietary and the Staff have, are still reviewing 9
this at this time for the 200 REM figure of merit.
10 It is based on analysis and discussions 11 presented in NUREG 0396. However, the Staff already 12 have reviewed this acceptance criteria and find that 13 it is within the residual risk discussed in NUREG 0396 14 Appendix I.
15 As such, I think that I'd also like to point 16 you to the bottom of this slide. We have a, we did 17 a little extra research with the Office of Research 18 in regard to providing a little more guidance in 19 producing the actual figures of merit utilizing the 20 MACCS code.
21 The MACCS code has many vintages of dose 22 conversion factors for many different ICRP 23 recommendations and so we provided a little extra 24 guidance on how one would compute the total effect of 25
52 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 dose equivalent versus the EPA's total effective dose 1
or how would you go when you compute the acute dose?
2 And that would be utilizing specific dose 3
conversion factors for lead bone marrow. So we did 4
provide the Staff report that you can see it at the 5
bottom of this screen. On to Slide 11.
6 MEMBER KIRCHNER: Elijah, before you go 7
on, --
8 MR. DICKSON: Yes.
9 MEMBER KIRCHNER: -- just to characterize 10 things, I would submit that the uncertainty between 11 the dose conversion that were used then and we use now 12 using MACCS is, they're comparable.
13 There's not a big difference there. These 14 uncertainties come in questions like Joy ask earlier.
15 So how does the system perform?
16 MR. DICKSON: Right.
17 MEMBER KIRCHNER: And you know, the 18 probability of a melt through and a containment breach, 19 how big are those breaches, et cetera, et cetera.
20 I mean, there's so much, compared to dose 21 conversion, there's so much uncertainty in the in 22 deriving that source term, --
23 MR. DICKSON: Right.
24 MEMBER KIRCHNER: -- that the dose 25
53 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 conversion is, it's an important thing too and I'm glad 1
you pointed that out, but it's not, it's not a big factor 2
in --
3 MR. DICKSON: You're --
4 MEMBER KIRCHNER: -- coming up with a 5
distance.
6 MR. DICKSON: You're right. There is more 7
of a regulatory purpose behind it.
8 MEMBER KIRCHNER: Yes.
9 MR. DICKSON: The whole system of Part 20 10 radiation protection is based off of, you know, the 11 ICRP 2630 system and those tissue weighting factors 12 from that system of dosimetry are directly codified 13 in Part 20.
14 And so if you were to compute TEDE, the 15 total effective dose equivalent which is also codified 16 by definition in Part 20, you need to use the right 17 dose conversion factors.
18 We find at times that applicants or 19 licensees may utilize the wrong dose conversion factors 20 and might compute the TED, the total effective dose, 21 so we're just trying to make that important distinction 22 here.
23 That if you're computing TEDE, you got to 24 use these dose conversion factors that way you are 25
54 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 consistent with the regulation.
1 MEMBER KIRCHNER: Thank you.
2 MR. DICKSON: Thank you. Then lastly, on 3
Slide 11 for my section of the slides, the source term 4
and radiological consequence analyses, the top of the 5
report recommends the use of MELCOR and RELAP to perform 6
design specific source terms and then requires the MACCS 7
code to perform the radiologic consequence analyses.
8 And the Staff finds that these computer 9
codes are appropriate to perform these analyses. And 10 with that, I'll go on to the next slide which Marie 11 has if there's no other questions.
12 DR. BLEY: Yes, before you go on, I have 13 one. I almost didn't ask you. I've been waiting for 14 a while. This is Dennis Bley.
15 MR. DICKSON: Hi.
16 DR. BLEY: 0396 was done 50 years ago.
17 It was done when there was one PRA in existence. In 18 the last 10, 20 years, the Staff has made a very big 19 deal about how much more they've learned and how much 20 better they can calculate than they could way back then.
21 Why, what's the justification for still 22 hanging on to 0396? Just that it's perhaps 23 conservative with respect to these issues? What's your 24 thinking on that?
25
55 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. DICKSON: It's, I think it's more the 1
process in which those individuals and organizations 2
came up with the planning basis. Not so much that very 3
specific WASH-1400 PRA, but that they went through a 4
process of considering risk information, they went from 5
a process of considering design basis type information 6
and then made that final selection.
7 That process is being echoed more or less 8
in this Topical Report.
9 DR. BLEY: Okay, well what I was really 10 getting at and I agree with what you just said. But 11 since we have learned how to calculate things better 12 and we have a lot of PDRAs since that time, not so many 13 Level 3s, but there are some, if we take that same 14 process and lay it up against what we know now, might 15 we come up with different results? It seems like we 16 ought to.
17 MR. DICKSON: Yes, that would be outside 18 I think the Topical Report review. That's more of a 19 policy type of question.
20 DR. BLEY: Yes, it is.
21 MR. DICKSON: It is.
22 DR. BLEY: You willing to talk about it?
23 MR. DICKSON: No, I'm not. I'll take that 24 one back with me. How about that?
25
56 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 DR. BLEY: Okay.
1 MR. DICKSON: Yes.
2 MEMBER KIRCHNER: I think what you're 3
suggesting, Dennis this is Walt, is that based on the 4
SOARCA analyses, you could pull back on the ten mile 5
radius of the large plants. Maybe you might be thinking 6
that.
7 DR. BLEY: You can guess.
8 MEMBER KIRCHNER: I certainly was thinking 9
that. No comment necessary.
10 MR. DICKSON: Marie, are you next?
11 MS. POHIDA: Yes, thank you. I'd like to 12 discuss now event selection for EPZ sizing and how it 13 needs to be consistent with NUREG 0396. The first point 14 that I'd like to bring up is the spectrum of accidents 15 is it's not equal.
16 It's not similar to licensing and designing 17 new nuclear power plants against the QHOs. The 18 screening of accident sequences must ensure that 19 there's an adequate spectrum of events included in the 20 EPZ technical basis.
21 And so this task is completely different 22 and distinct from the licensing and review of a new 23 reactor's design against the Commission goals for new 24 reactors. And as you know, these goals are, you know, 25
57 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 a CDF of ten of minus four, any large release frequency 1
of 20 minus six.
2 And that's stipulated in the S-REM 3
D-SECY-90-016. So the spectrum of accidents for EPZ 4
sizing has to include the characteristics of 5
radiological consequences from design basis access and 6
from a design basis, beyond design basis access.
7 So it has to include some the key 8
characteristics of more severe accidents and more 9
severe is the containment not intact with large releases 10 and it has to ensure that there's a capability to reduce 11 early severe health effects, injuries or death in the 12 event of the most severe beyond design basis events.
13 So the selection of the spectrum of 14 accidents for EPZ sizing does not, you know, alter the 15 design or operation of the plant. You know, new 16 reactors, you know, transition from large release 17 frequency to large early release frequency at or before 18 initial fuel load.
19 But emergency planning, you know, follows 20 the design and operation of the plant. Next slide 21 please. I'd like to continue this discussion of this 22 event selection on for EPZ sizing on Slide 13.
23 You know, the purpose of EPZ is dose 24 savings, not dose avoidance. And I'd like to present 25
58 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 a quote from NUREG 0396. It's while the EPZ should 1
not be solely dependent on the most severe and most 2
improbable beyond design basis event, the determination 3
of the EPZ size needs to include some of the key 4
characteristics of very large releases.
5 Now, we expected that seismic risks would 6
be a dominant contributor to the NuScale risk profile, 7
you know, and factor into EPZ sizing. Okay. If you 8
look at the results of the NuScale design certification 9
PRA in their FSAR, and it's in Table 19.1-80, NuScale 10 reduced the risk from internal events, you know, logos, 11 losses of DC power and external events such as high 12 winds, internal fires and internal floods.
13 We also realize that the timing of these 14 seismically initiated sequences would be different to 15 non-seismic events. If you look at the seismic margin 16 results from the design certification PRA, it's 17 dominated by structural failures such as seismically 18 induced failure of the reactor building crane supports 19 and seismically induced failure of the reactor building 20 exterior walls.
21 And they are, if they occur or are soon 22 to result in core damage. So the inclusion of seismic 23 events in the spectrum of accident sequences is 24 important to maintain consistency with NUREG 0396.
25
59 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 And we can go to Slide 13 please.
1 And what I would like to do is discuss these 2
two donut charts. On the left you'll see the results 3
of the NuScale design certification PRA as it's 4
documented in the FSAR in Table 19.1-80.
5 And that's without any contributions from 6
seismic core damage frequency. If you look on the 7
right, you see an example risk profile of an existing, 8
you know, operating nuclear power plant site which 9
includes seismic core damage frequency assuming that 10 a NuScale design certification plant is built there.
11 So I'm going to note again that the EPZ 12 methodology was to ensure that there's an adequate 13 spectrum of seismic events to be consistent with NUREG 14 0396.
15 Now if you look at the donut chart on the 16 right, you'll note that this site lies within the 17 NuScale certified design response spectrum. And these 18 seismic core damage frequencies were derived using the 19 seismic hazard information from NTTF 2.1.
20 And the seismic hazard was convolved with 21 the fragilities of structural components that are 22 listed in Table 19.1-35 in the NuScale design 23 certification FSAR. And they were convolved to obtain 24 core damage frequencies.
25
60 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 If you look in Table 19.1-34, you know, 1
seismically induced failure structural components were 2
assumed to lead to core damage. I will break here, 3
see if there's any question on this slide.
4 MEMBER PETTI: Just a lot of the NuScale, 5
philosophically, doesn't surprise me that a designer 6
would try to design away the internal --
7 MS. POHIDA: Yes.
8 MEMBER PETTI: -- threat. And so you're 9
left with the external so I think you're going to see 10 this over and over again with the advanced reactors 11 that are coming in where they've got inherent and past 12 features that are going to create the same dichotomy, 13 if you will, of the core damage frequencies.
14 Some may not even be able to describe a 15 core damage frequency, but upset frequencies are going 16 to be significantly different and you might want to 17 think about longer term, about as some guidance.
18 You know, in this regard that's generic, 19 you know, sort of a cross, but you know, independent 20 of a reactor technology because I think we're going 21 to, you're going to see this over and over again.
22 MS. POHIDA: We agree. And Shilp will 23 touch on this issue when he discusses seismic risks 24 and how we treat it in the methodology and how we 25
61 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 reviewed it. Is there any more questions?
1 We can go to next slide please. All right, 2
I'd like to discuss the Staff review of the non-seismic 3
single modules sequence screening. The Topical Report 4
uses a sequence screening of 20 minus 7 per reactor 5
year.
6 And that threshold would have screened in 7
all of the WASH-1400 release sequences. None of these 8
release sequences had a frequency less than 20 minus 9
7 per year. So we found this to be an acceptable 10 screening threshold.
11 May I go to the next slide. Thank you.
12 Second, I would like to discuss the Staff review of 13 the multimodule impacts for non-seismic hazards.
14 Okay. WASH-1400 did not explicitly model common mode 15 mechanisms such as fire, floods, tornadoes, which have 16 the potential to impact multiple modules in the event 17 trees and the fault trees.
18 I went and reviewed Appendix 4 of WASH-1400 19 and they, it states that these common mode mechanisms 20 were assessed as impacts when the system fault trees.
21 So the core damage sequence screening was 22 of 10, 20 minus 7 was also applied in the Topical Report 23 to multimodule core damage sequences. And once again 24 is I'll note that none of the WASH-1400 release 25
62 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 sequences had a frequency less than 20 minus 7 per 1
reactor year.
2 So the Staff found this screening threshold 3
for multimodule non-seismic hazards to be acceptable.
4 And then I'd like now to turn the discussion over to 5
Shilp so he can discuss seismic. Thank you.
6 MR. VASAVADA: All right. Thanks, Marie.
7 First of all before I start, I just wanted to make 8
sure I can be heard clearly at least on the phone.
9 I have a mask on so please let me know.
10 PARTICIPANT: Still has it.
11 MR. VASAVADA: Okay, how about now? Good?
12 PARTICIPANT: That's better.
13 MR. VASAVADA: Okay. All right, so I'll 14 start with the seismic screening threshold and then 15 go towards the end of the presentation. We have two 16 of the Topical Report proposed a seismic screening 17 threshold of 20 minus 5 per year based on the initially 18 frequency.
19 This was a long-standing open item in the 20 review. And not because the Staff decided to pay 21 excessive attention to seismic or treat it differently 22 from all the other hazards, but because 20 minus 5 per 23 year screening threshold resulted in an incomplete 24 spectrum effects.
25
63 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 This is because there's negligible, if any, 1
beyond design it is seismic risk at that particular 2
frequency. The reason is that if the, what's called 3
a ground motion response spectrum which is used too 4
for the design purposes, is determined per the guidance 5
in Reg Guide 1.208 which it usually is than the approach 6
or their results in a target failure frequency for the 7
SSCs of 20 minus 5.
8 What that basically means and this is 9
explicitly mentioned in the Reg Guide that you have 10 negligible, if any, failure property of the SSCs at 11 that particular frequency.
12 So therefore you have negligible zone 13 design with assessment risk and the spectrum of 14 accidents is incomplete as was pointed out. 0396 does 15 call for a complete spectrum of accidents for EPZ 16 sizing.
17 So you do not have risk insights from the 18 dominant risk contributor. In addition, in WASH-1400, 19 seismic risk was considered although it was considered 20 qualitative.
21 The 20 minus 5 does not even cover the 22 extent of expirations that were considered 23 qualitatively in 1400s. From that perspective, it also 24 would be inconsistent.
25
64 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 And it would be inconsistent with my view 1
from the principles of risk informed decision making 2
because you do not have risk insights from a dominant 3
risk contributor or a risk informed decision.
4 That was primary reason why the 20 minus 5
5 in Version 2 was the concern, open item, and Staff 6
found that there was gap in the spectrum of accidents 7
that was being considered and therefore the risk in 8
size are EPZ size.
9 I'll fast forward to the Topical Report 10 which provides, proposes a proprietary value for the 11 screening curve. So the value at this and the 12 acceptability of this were and is consistency with 0396 13 as well as WASH-1400.
14 What the Staff did was it doubled up an 15 upload which we call the risk gap approach. The purpose 16 of the risk gap approach is to determine whether the 17 proposed screening threshold captures insufficient 18 spectrum effects against spectrum of seismic sequences 19 for consideration EPZ sizing.
20 As I talked about it in the previous slides, 21 zero percent at 20 minus 5 per year is inconsistent, 22 but so is 100 percent, the entirety of the seismic risk.
23 As Marie pointed out, 0396 clearly states 24 you do not have to use the worst case scenario for EPZ 25
65 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 sizing. You need to have a good spectrum of facts.
1 And that's what the objective of this risk gap approach 2
was.
3 And the appropriate amount on the spectrum 4
of beyond design is -- please stop me if there are any 5
questions. I'll keep going. I'm on Slide 19 which 6
provides like an overview of the risk gap approach.
7 There are details provided in the Staff 8
safety evaluation and at this score, the approach is 9
simple to implement. It has four steps. I won't go 10 into the details, but overall, collect an ensemble of 11 hazard curves representing different sites within a 12 design and discuss most scales certifies seismic design 13 response spectrum.
14 You identify of land load fertility in the 15 mean scales marked for fertility and provides 16 additional details about sector ratios. You can wonder 17 too to get an estimate of the seismic core damage 18 frequency.
19 And you can let how much risk is being 20 essentially left off the table. And you can do sizing 21 determinations below the threshold. Either a 22 prescribed threshold or you can use this to identify 23 the property threshold.
24 And we will talk about the exact value.
25
66 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 So how often implemented this risk gap approach 1
determine if NuScale is proprietary in threshold 2
admitted and was acceptable.
3 We did this using nine of risk gap to size.
4 Let's go to the next Slide 21 to show the totally where 5
the sites are with respect to the NuScale certified 6
seismic design response spectrum of CSDRS.
7 As can be seen in the slides cover a range 8
of seismicity. They cover western and the central 9
eastern United States and they have different like 10 characteristics of the rock while back filled.
11 MEMBER HALNON: Shilp, this is Greg. How 12 did you assure yourselves that was representative of 13 any place a NuScale plant could be built?
14 MR. VASAVADA: Right, so the primary 15 reason was by selecting the site, removal of sites that 16 covered the regions, western United States, eastern 17 United States, different types of soil characteristics 18 and/or IP of seismicity from low seismicity as you see 19 the mustard line on the way to the yellow line.
20 MEMBER HALNON: Okay. But so your sample 21 was broad enough and the results close enough to have 22 you, give you confidence that was characteristic of 23 pretty much any soil types in the United States.
24 MR. VASAVADA: Right. So that --
25
67 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MEMBER HALNON: Did that include Alaska 1
as well?
2 MR. VASAVADA: So anything within the 3
NuScale's CSDRS, we did not go to Alaska.
4 MEMBER HALNON: Okay.
5 MR. VASAVADA: We did consider California.
6 Other than that, out of the NuScale CSDRS as NuScale 7
presented --
8 MEMBER HALNON: Okay.
9 MR. VASAVADA: -- and we talk about in the 10 conditions of use. This is --
11 MEMBER HALNON: A continuous --
12 MR. VASAVADA: -- only on the NuScale 13 design so it's been NuScale design.
14 MEMBER HALNON: Okay. They stayed within 15 their design.
16 MEMBER BALLINGER: Where does New Madrid 17 fit on this?
18 MR. VASAVADA: I'd have to go back and 19 check, but it would be somewhere --
20 MEMBER BALLINGER: But it's there.
21 MR. VASAVADA: Yes, it would be somewhere 22 23 MEMBER BALLINGER: Okay.
24 MR. VASAVADA: -- close to the CDCRS in 25
68 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the top. What is at the bottom is some of the cited 1
updates like for example Texas where it has low 2
seismicity. Any further question?
3 MEMBER KIRCHNER: Yes, Shilp.
4 MR. VASAVADA: Yes.
5 MEMBER KIRCHNER: Explain to the public 6
the last sub-bullet on Slide 20.
7 MR. VASAVADA: Yes, I was getting to that.
8 MEMBER KIRCHNER: Why don't you capture 9
20 to 50 percent of the seismic risks.
10 MR. VASAVADA: So --
11 MEMBER KIRCHNER: Which is not captured 12 so in lay person terms explain this convolution that 13 you've gone through --
14 MR. VASAVADA: Okay.
15 MEMBER KIRCHNER: -- to address this risk 16 gap.
17 MR. VASAVADA: All right, so basically 18 going through that particular approach often watering 19 it and getting the seismic CDF looking below how much 20 risk is left off the table with all the proposed 21 proprietary screening threshold, we determined that 22 it was around between 50 to 80 percent of the seismic 23 risks would be not included, but EPZ sizing for the 24 majority of the plants.
25
69 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 For more than half of the plants, we did 1
not include 50 to 60 percent. Does that help?
2 MEMBER KIRCHNER: It will not include what 3
50 to 60 percent?
4 MR. VASAVADA: The seismic risk and the 5
sequences that guide.
6 MEMBER KIRCHNER: Okay.
7 MR. VASAVADA: And we also looked at the 8
absolute value of the risk gap in addition to the 9
relative contribution. And all of that information 10 and the details, including the numbers are in the Staff 11 safety evaluation.
12 I'm going to Slide 22 because I talked about 13 21 in conjunction with 20. We also looked at the 14 multimodule risks impacts and I'll talk about that in 15 detail in a subsequent slide and --
16 MEMBER PETTI: Can I just take you back 17 because I'm a little confused on that. The threshold, 18 the list that it's not capturing seismic events that 19 are extremely low frequency.
20 MR. VASAVADA: I'm sorry, yes.
21 MEMBER PETTI: Okay. I mean, that's what 22 I assumed. So you had taken the more frequent seismic 23 events?
24 MR. VASAVADA: Correct. I mean that was 25
70 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 a part of the consideration in determining where the 1
property is, yes, how much is lost absolute terms, 2
relative terms. And what's the acceleration levels 3
at which we are talking about.
4 So I go to the Slide 18. At 100 percent 5
if you consider the entirety of seismic risk, you are 6
talking about like extremely unlikely accelerations 7
of 2Gs, et cetera.
8 And that was also, it would be found as 9
inconsistent with the fundamental digits in 0396. You 10 need a spectrum of accidents not designed in digital 11 in the worst case.
12 MEMBER PETTI: Fine, thanks.
13 DR. SCHULTZ: How is it that you used in 14 the, just go back to that slide, how is it -- this is 15 Steve Schultz. How is it that you used before the --
16 MR. VASAVADA: Before it?
17 DR. SCHULTZ: Yes. During the Slide 20.
18 MR. VASAVADA: Oh, got it.
19 DR. SCHULTZ: That you used the HCLPF, that 20 the NuScale high confidence low probability of failure?
21 MR. VASAVADA: So --
22 DR. SCHULTZ: It's at 95 percent values 23 so just to follow onto Dave's question.
24 MR. VASAVADA: All right, so the HCLPF high 25
71 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 confidence of low probability of failure is 95 percent 1
confidence with 5 percent failure or less. On the 95th 2
percent or what is also on the mean curve, 1 percent 3
or less failure probability.
4 And we use the values from their NuScale 5
SRA for the DCA design for this purpose, for the 6
convolution purpose.
7 DR. SCHULTZ: And when you say then the 8
threshold captures the 20 to 50 percent seismic risk 9
across the majority of nine sites, can you, can I get 10 something from the next slide that tells me what that 11 is in going to explain this to the public?
12 MR. VASAVADA: I'm sorry, if you can please 13 clarify like --
14 DR. SCHULTZ: How was HCLPF used, how was 15 that value of HCLPF used?
16 MR. VASAVADA: Okay. I can get in, so go 17 to Slide 19 for the steps. Step 2 is you determine 18 the plant level HCLPF are identified in the case of 19 NuScale.
20 You use that to provide the conditional 21 failure for the public of the plant considered as a 22 whole. And then you can roll that with the seismic 23 hazard.
24 And that convolution will give you the 25
72 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 equal, or an estimate of the seismic core down issues.
1 So that's how it was used for the purposes of this 2
evaluation.
3 DR. BLEY: Can, this is Dennis Bley. Can 4
I jump in with a kind of a question. This is an, it's 5
an interesting approach and it seems reasonable, but 6
what it's kind of telling me is that for the purposes 7
of looking at this report, nothing jumps out that's 8
truly unreasonable.
9 But eventually there will be a complete 10 plant design and a complete plant being built at a 11 particular site. And then they're going to have to 12 come and actually look at this for their site with the 13 actual seismicity at that site so that this is just 14 kind of a screen to say nothing crazy is sitting here 15 that would be bad.
16 But you get it right before you have a real 17 plant with a real, entering real operations. Is that 18 a reasonable statement?
19 MR. VASAVADA: Yes, I believe if I 20 understand you correctly, that is reasonable. And when 21 we get to the conditions of use, you will see that a 22 couple of conditions, actually three of them which I 23 believe speak to what you just provided as a comment.
24 DR. BLEY: Okay. I'd like to see. Thank 25
73 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 you.
1 MR. VASAVADA: Okay. All right, so as on 2
Slide 22, we've talked about how we looked at the 3
multimodule risk aspect on a couple of other slides.
4 But what we found based on our evaluation again, found 5
that in the risk gap approach, was that the proposed 6
proprietary seismic hazard screening threshold 7
achieves consistency with NUREG 0396 and with WASH-1400 8
in that it results in a complete spectrum of accidents, 9
includes seismic sequences in that spectrum of 10 accidents and again, seismic is the dominant or we 11 expect it to be the dominant distributor.
12 While at the same time it does not penalize 13 NuScale for its mis-profile. Yes, they have reduced 14 the other risks and that is a benefit. And it does 15 not, you can say, provide extra focus to anything more 16 than what was done in 0396 in terms of determining an 17 adequate spectrum of accidents.
18 Nor does it include that extremely unlikely 19 seismic explorations of 2Gs and beyond. The one 20 difference I would point out compared to 0396 or in 21 terms of consistency is that the methodology.
22 And we believe it's appropriate to use as 23 quantified seismic sequences compared to the 24 qualitative approach that was used in WASH-1400. We 25
74 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 believe that's, that is necessary because it is a 1
dominant interest contributor.
2 And since Revision 2, the Topical Report 3
has called for a technically acceptable seismic PI, 4
but that's never been a point of contention. And 5
remember at this point to spend a minute or so hopefully 6
on this particular slide that we think this risk gap 7
approach has broader applicability.
8 Technology clean and close of applicant 9
routines or designers and other technologies to 10 identify what will be the appropriate spectrum and 11 maintain consistency with 0396 in determining if being 12 threshold for the seismic hazard.
13 Because a single one-size-fits-all value 14 may not work, given the technologies that are expected 15 to be out there. It may be too much for cert. Some 16 cases it may be too little for others.
17 The approach as well as pointed out, uses 18 design specific information. One doesn't have to go 19 about developing anything new and it can be used with 20 the metrics of the density LERF reused or risk gap.
21 One can go all the way to consequences and 22 use a consequence gap. And finally, the authority 23 itself can provide regulatory stability. You can get 24 different numbers that are as is usually done for 25
75 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 guidance, the approach can provide a consistent highly 1
reproducible way of achieving a decision on the seismic 2
screen.
3 I'm moving on to the treatment of 4
uncertainties for the seismic hazard. We will get into 5
the details in the proprietary section, how we have 6
already reviewed which was aided by the regulatory audit 7
in term and the approach and the lower bound threshold 8
for this uncertainty evaluation are sufficient to 9
identify any new risk insights.
10 And address any potential side effects 11 because the window that is adopted by this uncertainty 12 evaluation is large enough on that potential cliff as 13 you have scantly adorned it.
14 Plus the methodology, it brings in these 15 new sequences if they are identified in the evaluations 16 if they are not lost. They're actually comparatively 17 pleasing sizes.
18 For multimodule impacts from the seismic 19 hazard, we'll start with the bottom line of one that 20 we believe the methodology appropriately identifies 21 and includes multimodule impacts on seismic events.
22 We performed the primarily qualitative 23 evaluation and some of the considerations are listed 24 on the slide so. Slide, including the fact that based 25
76 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 on our risk gap evaluation, the accelerations that were 1
being acquired or reached for at the screening special 2
included those where multimodule impacts are expected.
3 And I think NuScale talked about how 4
multimodule sequences will also be reflected in the 5
source term by amplifying the source term based on the 6
modules and pattern.
7 There's one difference in the seismic 8
multimodule consideration compared to non-seismic 9
which is that there's a screening at 20 minus seven 10 for your, or non-seismic multimodule sequences which 11 is not applied to the same sequences.
12 This is primarily because of the way 13 seismic events are screened and the value compared to 14 non-seismic sequences which can result in double 15 screening if there are, if the 20 minus 7 were to be 16 applied for the seismic hazard.
17 I'm on Slide 26. It's a pictorial of the 18 type of information one can get at different stages, 19 licensing and our FSAR Part 52. And the purpose of 20 this slide is to state that the PR calls for the use 21 of technically acceptable PRA including a seismic PRA.
22 And it's that combined license stage and 23 beyond that one would get that so this Topical Report 24 would essentially be used at the COL stage or beyond 25
77 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 and we have a condition of use to provide equal and 1
you can say treatment for an operating license under 2
operating.
3 In terms of treatment of the modeling 4
uncertainty, I think NuScale talked about it that 5
there's a section, section 3.8 in the Topical Report 6
which includes a Board discussion of more uncertainty 7
of the need to be considered and disposition.
8 And we appreciate the discussion because 9
if it doesn't overlook any important piece of the items 10 in the, and based on our review, we determined the need 11 for consistency with established guidance for 12 identification and disposition of key assumptions and 13 sources of uncertainty which is Reg Guide 1, 200 and 14 1855.
15 So the Staff has included a corresponding 16 condition of use to achieve that. Next slide. I'm 17 on Slide 28. In terms of the consideration of defense 18 and depth, we find that methodology appropriately 19 identifies the key features that are necessary for doing 20 this defense and depth including SAMGs and then those 21 reaction I went got strategies and flex guidelines.
22 It is consistent with the PRA policy 23 statement and the certain considerations in 1.174 and 24 it also looks at the five levels of defense and insight 25
78 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 and which adds a level of confidence to the defense 1
and depth evaluation.
2 The qualitative defense and depth 3
evaluation as part of this method was.
4 CHAIRMAN REMPE: What flex strategies 5
would be required for, remind me, for NuScale? I mean, 6
are you going to bring in extra water sources or, and 7
if so, to be considered if the connectors are consistent 8
with what's needed for flex strategies?
9 MR. VASAVADA: Marie, you have any idea?
10 Marie?
11 MS. POHIDA: We may have to take that back.
12 I can't remember the specific --
13 MEMBER MARCH-LEUBA: Put your microphone 14 on.
15 MS. POHIDA: -- strategies used for design 16 certification.
17 MEMBER MARCH-LEUBA: Can --
18 CHAIRMAN REMPE: I can't remember either.
19 But it's something I've been thinking about for 20 non-LWRs and what you'd do for flex and that's why when 21 I saw this, it kind of made me wonder. I don't recall 22 us --
23 MEMBER MARCH-LEUBA: Does NuScale know?
24 MR. VASADA: I mean, we have, --
25
79 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MEMBER MARCH-LEUBA: -- you need to find 1
the microphone.
2 CHAIRMAN REMPE: I'm just curious about 3
flex strategy. Sorry to just talk to the mic, but I'm 4
curious about flex strategies and I can't remember if 5
we talked about flex strategies when we were dealing 6
with the EC review. Did we?
7 And which ones would you use? The other 8
recommenders?
9 MS. ENGLISH: We have --
10 MEMBER MARCH-LEUBA: No, you need to come 11 to microphone here and borrow this.
12 CHAIRMAN REMPE: So maybe you can come up 13 here.
14 PARTICIPANT: There on the floor which 15 side I see, indeed. See this mic is all ready.
16 PARTICIPANT: Just say who you are.
17 MS. ENGLISH: Hi, this is Liz English from 18 NuScale. The DCA did cover, addressed flex although 19 it's not a requirement of the design certification.
20 But in our Chapter 20 of the DCA, bottom line, is you 21 don't need to implement other than just keeping the 22 pool water adequate.
23 CHAIRMAN REMPE: So you dump it in a pool?
24 You don't need any connectors in the --
25
80 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MS. ENGLISH: It's already in the pool.
1 CHAIRMAN REMPE: Okay. That helps, thank 2
you.
3 MS. ENGLISH: You're welcome.
4 DR. BLEY: In that -- this is Dennis. In 5
that whole area, I remember we asked if they would be 6
participating in flex and I don't think we ever got 7
an answer on that from NuScale.
8 MS. ENGLISH: Right. And I believe that's 9
because it is not the design certification function 10 to look at, I'm not going to say this the right way.
11 Flex is a requirement of the licensee or the license 12 holder and not the design center.
13 CHAIRMAN REMPE: So when you have this on 14 your slide, you thought about what was going to be dumped 15 into the stint fuel pool is what gave you confidence 16 to say that you considered consideration or are you 17 just are repeating something that was in their Topical 18 Report?
19 MR. VASAVADA: So yes, we are including 20 something that is in Topical Report, but what we're 21 trying to say is that its own features and operational 22 characteristics considered for a defense and depth 23 evaluation include MGs and flex.
24 It's not like excluded. It's the entire 25
81 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 plan defense and depth that is considered. That is 1
what we are trying to say.
2 CHAIRMAN REMPE: Okay.
3 MR. VASAVADA: Thank you, Liz. I'm going 4
to Slide 29. So I'll talk about the Staff's conditions 5
of use. Based on our review and to ensure that the 6
key importance to the methodology and our findings are 7
addressed by the user of the Topical Report, we included 8
eight conditions of use.
9 The Slide 29 summarizes them. The exact 10 language is in the safety evaluation. At this point, 11 quickly go through them. So alpha is there to ensure 12 consistency between an operating license under Part 13 50 and a COL under Part 52.
14 Currently there's a need to ensure the 15 sense of consistency. Bravo talks about consistency 16 with an NRC guidance for technical acceptability.
17 Charlie is to demonstrate the treatment of key 18 assumption sources of uncertainties consistent with 19 NRC guidance.
20 Delta and Echo are about making sure that 21 the site, actually the GMRS is bounded by the NuScale's 22 CSDRS. And that the plant level fragility is in fact 23 attuned to the value that was in the DCN that was used 24 for the Staff's evaluation.
25
82 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 And foxtrot talks about the demonstration 1
of both of those items, GMRS and HCLPF plant level for 2
duty at both application and prior dose load so I think 3
that I go and foxtrot together speak to the comment 4
that Member Bley had earlier about having a plant 5
specific demonstration that the assumptions and inputs 6
are actually valid.
7 Golf talks about the 120 degrees of the 8
200 REM dose exceedance curve as you remember Elijah 9
talked about and Marie did too, how 0396 states that 10 the consequences of severe accidents degrees 11 substantially.
12 And she informed the curve is important 13 so golf, make sure that the shape of the curve is not 14 overlooked by either the Applicant or Staff. And hotel 15 is speaking to the principle of the performance 16 monitoring in risk informed decision making so it calls 17 for a periodic evaluation to make sure that like there 18 with HCLPF.
19 It is indeed what it was at the beginning 20 of the plant's life and that the conclusions from the 21 EPZ sizing methodology conclusion remain valid as the 22 plant changes or changes are made to the plant over 23 the lifetime of the plant.
24 MEMBER KIRCHNER: Let me explore number 25
83 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 G, golf.
1 MR. VASAVADA: Okay.
2 MEMBER KIRCHNER: How do you measure, 3
obviously in 0396 their Appendix I, that curve or that 4
ten miles has a sharp drop off. But as we pull or 5
potentially as the EPZ shrinks, will we see such a steep 6
drop off?
7 I don't know, have you kind of calculated 8
that out or has the NuScale curves convinced you that 9
we'll see the same thing if the calculations suggest 10 that the 200 REM threshold, I'm just thinking, how do 11 you measure that?
12 I know what you mean by that versus Appendix 13 I 0396, that curve has a steep fall off. But I think 14 what we're going to see is people are going to use a 15 methodology like this and be pulling in the -- I project 16 that the EPZs will come in.
17 We saw this with the early site permit work 18 for Clint River, you know, within a mile or so, but 19 what I don't know and maybe you've looked at this with 20 MACCS, do you see that same kind of steep fall off?
21 Because the general take away from 0396 22 is and I'll quote, that the EPZ should be a sufficient 23 size to provide substantial reduction in the early other 24 if that's in the event of a more severe Class 9 accident.
25
84 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Now I think that's what you're getting at, 1
but gee, I'm just curious how you measure that. So 2
you're looking at the shape of a curve or are you looking 3
again at some uncertainty in the shape of a curve or 4
how do you achieve that substantial reduction?
5 In other words, it's just like the existing 6
dose ends and can see afar 50 and 52. I mean, the idea 7
is not to run up to 25 REM in two hours.
8 It's to be substantially below so how in 9
your mind do you think there's enough conservatism in 10 the methodology such that the public will be 11 substantially protected by this guidance?
12 MR. VASAVADA: I think Elijah has his hand 13 up. I'll let him go first and then I can --
14 MR. DICKSON: Yes, I, this is something 15 of considerable discussion with the Staff. The way 16 it's addressed in 0396 is rather qualitative. Right?
17 That they look at the curve and they see that it drops 18 off quite quickly.
19 Our, I think our concern was we don't want 20 to see curves that have like sawtooth-type shapes or 21 ones that kind of just asymptotically decrease. We 22 don't want to see curves that may increase.
23 You know, it's hard to say what the, I use 24 the word measure and I, it's a bit more qualitative 25
85 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 than that. You know? It's hard to perceive what types 1
of curve we would be seeing.
2 And it, if we don't, it would be a 3
collective Staff decision in regard to whether or not 4
that proposed EPZ would be acceptable if they have 5
something that differs drastically from what you're 6
seeing in 0396.
7 MEMBER PETTI: So Elijah, the decrease, 8
Appendix I, is that tied to just fall out from a plume?
9 MR. DICKSON: Yes, it's --
10 MEMBER PETTI: Yes?
11 MR. DICKSON: -- for the most parts, it, 12 for the most part, it's the meteorology and the 13 transport calculations that have a fall off that way.
14 MEMBER BIER: Yes, I have a follow up 15 question on that condition G which is can you talk about 16 which features would potentially lead to an increase 17 or saw-tooth nonmonotonic shape? How would that come 18 about?
19 MR. DICKSON: I do not know. I do not have 20 an answer for that question.
21 MEMBER BIER: So for now it's just stated 22 kind of --
23 MEMBER KIRCHNER: I can give an example 24 I think.
25
86 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MEMBER BIER: Okay, great.
1 MEMBER KIRCHNER: In answer to your 2
question. A near, if it really theoretically when you 3
calculate it came in very close, then building wake 4
effects and such will give you a different shaped curve 5
than a traditional plume description.
6 And so you may have a drop off and then 7
an increase. And then a fall off. Depending how close 8
you are so then using ARCON or something --
9 MEMBER BIER: Okay.
10 MEMBER KIRCHNER: -- near end might be an 11 important consideration. I don't know, does MACCS use 12 ARCON for close in distance or I'm trying to remember.
13 Are you just, it's just a classic plume dispersion?
14 MR. DICKSON: I do believe it's been 15 included now. I think we have one of our MACCS experts, 16 Keith Compton, on the phone on standby. He's here.
17 Keith?
18 MR. COMPTON: Yes, I, can you hear me?
19 MR. DICKSON: Yes.
20 MR. COMPTON: Yes. So yes, just so a few 21 comments. Yes, we have --
22 MEMBER KIRCHNER: Keith, just identify 23 yourself first please.
24 MR. COMPTON: I'm sorry. This is Keith 25
87 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Compton from the Office of Research.
1 MEMBER KIRCHNER: Okay.
2 MR. COMPTON: Yes, we have recently 3
upgraded MACCS to improve its near field capabilities 4
and you can include models that are comparable to the 5
ARCON model or to the full reg at 1.145 model at shorter 6
distances.
7 And that would help you as I believe one 8
of the members mentioned. Yes, if you had, if you had 9
a close-in distance and you had an elevated release 10 or plume rise or something like that, you could actually 11 have low, you know, kind of a low dose close in.
12 It would rise when you got plume impaction 13 and then it would start dropping so yes, certainly you 14 can have any number of different shapes on that curve.
15 MEMBER BIER: Yes, the high elevation 16 release is another one that occurred to me. It starts 17 out high with a low dose and it drops eventually, but 18 19 MR. COMPTON: That's right.
20 MEMBER BIER: Thank you.
21 MEMBER KIRCHNER: Thank you, Keith.
22 MR. DICKSON: Any other questions on that?
23 MEMBER HALNON: On the earlier question 24 on peer review for the PRA and the technical aspect, 25
88 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 did you all have a discuss about what, how far that 1
needs to go and how much it needs to look like the 2
traditional peer reviews?
3 MR. VASAVADA: I'll, pardon my, what we 4
did on way back along. If you look at OR, a condition 5
of use, bravo, is basically asking for consistency with 6
the established guidance for PR technical acceptability 7
which will include the peer review.
8 We do recognize that at certain stages in 9
the design, or when this article of methodology is used, 10 not every aspect of the supporting requirements as they 11 are called for the PRS standard can be excused.
12 For example, operating experience. NSRC 13 does talk about how when the results of seismic tech 14 was of a review being formed by what's called a ISG 15 028 which talks about making allowances for such cases.
16 MEMBER HALNON: Okay, --
17 MR. VASAVADA: There's nothing like --
18 MEMBER HALNON: -- depending on what stage 19 they're in. Thanks.
20 MR. VASAVADA: Anything else?
21 MEMBER KIRCHNER: Marie, I don't want to 22 cut out questions. Can you do your conclusion and then 23 I'll go around? Because we've run --
24 MR. VASAVADA: No, no, go ahead.
25
89 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MEMBER KIRCHNER: -- over.
1 MR. VASAVADA: Okay, no, no, go ahead.
2 MEMBER KIRCHNER: Okay. If you want to 3
conclude. We've run over a little bit on time.
4 PARTICIPANT: Walt.
5 MEMBER KIRCHNER: Thank you. We've gone 6
over a little on time, but that's okay. We're asking 7
questions that we might have asked later. Could you 8
just go through your conclusions and then we'll go 9
around and ask for Member questions.
10 MR. VASAVADA: Absolutely. So on Slide 11 30, this provides kind of the overarching conclusions 12 that the Staff primarily Maria, Elijah, and I would 13 support from those acute reach.
14 We found that the Topical Report 15 methodology is generally consistent with the underlying 16 basis in 0396 and it provides a reasonable assurance 17 that the methodology is adequate for assessing the plume 18 exposure causeway emergency planning zone ties.
19 Obviously, the applicants have to meet the 20 scope of applicant ready in Section 2.5 which defines 21 the characteristics for the NuScale design and it's 22 definitiveness and the conditions of use in Section 23 5 of the Staff's safety evaluation.
24 We also think that the NuScale EPZ TRA is 25
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 indeed of this conformed and reflective of the 1
underlying approach in 0396. It meets all of the 2
principles of risk informed decision making either on 3
its own or in conjunction with the Staff's conditions 4
of use.
5 And I'll end by providing some caveats.
6 I think they're important. Firstly, the methodology 7
and the Staff's findings are applicable only to this 8
TR for EPZ sizing and they do not extend to the design 9
and operation or licensing.
10 The QHOs are applicable to those and they 11 also do not cover other aspects of emergency planning 12 besides these. On the screen thresholds are only 13 applicable for this particular methodology not for the 14 underlying PR development which needs to follow either 15 endorsed PRA standards or justified alternates.
16 And finally, the Staff is not making or 17 defining what is meant by credible events or any hazard 18 through the screening thresholds for this particular 19 Topical Report.
20 That's outside the scope of the Topical 21 Report and we are not making any findings of that.
22 That I'll end and open up for any questions. Thank 23 you.
24 MEMBER KIRCHNER: So let me turn to Dave 25
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 first. Thank you.
1 MEMBER PETTI: So you know, my sense is 2
that a, this is an incredibly important topic for the 3
advanced reactors -- adding the NuScale. Others are 4
going to look to this.
5 And it seems like you guys have really 6
broken ground in terms of kind of connecting dots 7
between what was then in 0396, what the intent of 0396 8
was and how to turn that into something more 9
quantitative for today with today's tools, today's PRA 10 capabilities.
11 I just think some of these nuggets need 12 to be in guidance somewhere. That the Topical Report 13 is good, as long as you can make sure you don't, you 14 know, touch on proprietary stuff with NuScale.
15 I think what you guys have done deserves 16 a little bit more elevation in the infrastructure of 17 this. One Member's thoughts.
18 MR. VASAVADA: Thank you.
19 MEMBER KIRCHNER: Other Members?
20 MEMBER DIMITRIJEVIC: Walt?
21 MEMBER KIRCHNER: Yes, go ahead Vesna.
22 MEMBER DIMITRIJEVIC: Well I've kept 23 actually too many questions to ask so I decided that 24 are we going to have additional, I was looking at the 25
92 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 schedule, meeting on this because this is before we 1
write the letter.
2 MEMBER KIRCHNER: So what I would propose 3
here is we still need to allow for public comment.
4 If you have questions, that's good. Hold onto them, 5
Vesna, because I think we would be best served if we 6
go into a closed session and proceed then. Can you 7
hold onto those questions until then?
8 MEMBER DIMITRIJEVIC: I can hold on 9
actually which I was going to do is actually take some 10
-- because I went through all these documents except 11 that I didn't really went through the NUREG 03, you 12 know, the 396 and see how it complement to the WASH-1400 13 to see how this all fits together. So I have already 14 the question which starts with this very high-level 15 picture.
16 And then I was going to devote more time 17 in my own research before I, you know, reduced the 18 questions. So I was just wondering how own schedule.
19 But I will check on that much during the break so 20 And then I will decide when should I, you 21 know, ask my questions. All right?
22 DR. BLEY: Well, it's not, Vesna, you're 23 not going to find it on the rainbow chart.
24 MEMBER KIRCHNER: No.
25
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 DR BLEY: It's going to be the next full 1
Committee meeting. There's going to be another --
2 MEMBER KIRCHNER: In October.
3 DR. BLEY: Yes, another meeting like this 4
going a little further. Right?
5 MEMBER DIMITRIJEVIC: Well, yes, I was 6
going to check on the AWS, when do we write letter on 7
this and how --
8 MEMBER KIRCHNER: It's --
9 MEMBER DIMITRIJEVIC: -- this will look 10 like.
11 MEMBER KIRCHNER: -- in the October full 12 Committee meeting. So it would --
13 MEMBER DIMITRIJEVIC: So that's what it 14 is, okay.
15 CHAIRMAN REMPE: Vesna, there was supposed 16 to have been an extra meeting on September 1st or 2nd, 17 I forgot which day. And we moved it into this full 18 Committee meeting. Remember?
19 And we did that because of various reasons, 20 but anyhow, this is what would have been the 21 subcommittee meeting, but always this has been proposed 22 for a topic for October full committee letter writing 23 as indicated on the AWS. Okay?
24 MEMBER DIMITRIJEVIC: Okay. All right, 25
94 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 it's good to know. Okay, so I will hold on to my 1
questions to then today and then hopefully I can use 2
them myself. All right?
3 MEMBER KIRCHNER: Okay, thank you. Other 4
members?
5 CHAIRMAN REMPE: Yes, a couple of things.
6 Maybe the answers are kind of related to this adequacy 7
of the peer review and guidance, but I also believe 8
that this is like a start of something new or you might 9
have a much smaller EPZ.
10 And so the questions I raise to NuScale 11 are the kind of ones that I am interested in the Staff's 12 thoughts on this because one, to me it seems like the 13 adequacy of the MELCOR model that was used for the design 14 certification is suddenly becoming, the integrity of 15 that model might become more important since you're 16 deciding on whether you need to think about the size 17 of the EPZ.
18 And so I'm just curious if maybe in that 19 guidance you might say we need to think more carefully 20 in the peer review of what and it's just one Member's 21 comment, but I am interested if you're thinking about 22 that because suddenly if I, this is just a review of 23 the Topical Report, but someone comes in and says, I 24 want to have it to be the plant boundary and follow 25
95 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 EPZ.
1 So I don't need to worry about any sort 2
of emergency planning and they don't do what is in the 3
NEI report to think about how to expand for emergency 4
planning.
5 I might have a different view of the this 6
than I do for something that's theoretical. And have 7
you thought about where this is going and maybe this 8
is beyond the scope of your review for the Topical 9
Report, but I'm just a little concerned and I'm curious 10 to hear your thoughts on it.
11 MR. VASAVADA: Hello, this is Shilp. From 12 my point of view, I think the items that you are talking 13 about they will part of the review somewhere else, maybe 14 in the scope of the SDR or DCA or some other speaker.
15 And then they'll flow into this Topical 16 Report because I mean, at the end of the day, they have 17 to use the underlying PRA morals which have been record 18 either by the Staff or through the peer review process.
19 Which in the peer review process and PRA 20 standard, does have specific supporting requirements 21 for the containment and all methodology in the Level 22 I are kind of aspects.
23 CHAIRMAN REMPE: Okay, we were reviewing 24 this very accident phenomena when we were reviewing 25
96 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the severe accident phenomena for something that was 1
a very low frequency even though there wasn't a lot 2
of data.
3 We might have said, okay, it's a low 4
frequency, but now suddenly there's this screening 5
frequency. I've heard you talk about the non-seismic 6
hazards that though a spectrum of events and having 7
a bypass failure for a more severe accident being the 8
dictating.
9 Well maybe we might have, so maybe we need 10 more integrity in the MELCOR vessel failure model or 11 the containment vessel failure model. And I just am 12 wondering if what we thought was okay for some things 13 if we, in our mind we thought well we'd always have 14 some sort of sight emergency planning in place.
15 You get where I'm going? I'm sorry if I'm 16 too vague on what I'm trying to say here.
17 DR. BLEY: Well I think it's, Joy. This 18 is Dennis.
19 CHAIRMAN REMPE: Yes.
20 DR. BLEY: This, maybe the Staff will 21 comment on this a little bit. 0396 essentially points 22 to we got to be real careful on things that we think 23 are very low and at least have an idea that we'll be 24 able to reduce the consequences if any of those happen.
25
97 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 And I, from what you folks have said and 1
written, I think that's where you're headed. If 2
there's even a, what appears to be extremely low 3
frequency event, you want to be somehow convinced that 4
it will be possible to take steps immediately following 5
an accident to deal with those and that there's an 6
infrastructure to support that. Is that the reason 7
for --
8 CHAIRMAN REMPE: Well okay, I look and it's 9
not in the proprietary markings of the Topical Report, 10 but for the more severe accidents, they only considered 11 bypass failures. They didn't and so how big was the 12 release?
13 Did they really have a severe accident?
14 From what I recall from the DC, no they didn't have 15 the orb out of the vessel into the containment. I just 16 wondering if you, did your spectrum of accidents 17 consider that or was that just below the threshold?
18 And I again, I know that the containment 19 failure thing was very little data to support that 20 analysis. It was okay for the DC, yes, you're going 21 where I'm going, Dennis, about saying do they still, 22 will they still have the capability and will that still 23 be considered? And it's in the NEI document.
24 MS. POHIDA: I'd like to take a stab at 25
98 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 that and I recall what you're discussing. Because 1
there was a lot of discussion during design 2
certification of NuScale design regarding issues on 3
in-vessel retention.
4 So now I would anticipate that those issues 5
would be re-evaluated during, you know, the standard 6
design review.
7 CHAIRMAN REMPE: Yes, because it's a 8
higher power. I would hope so. But if this, again, 9
when we're doing this, I hope people realize that 10 someday we may need more integrity in the PRA than we 11 need if they're going to say that the emergency planning 12 zone is a site boundary.
13 MS. POHIDA: Yes, now this is the Topical 14 Report so we're reviewing the process, but when it comes 15 well not logical uncertainties like we're discussing 16 regarding in-vessel retention that were evaluated and 17 designed, you know, in design cert and I anticipate 18 it will be re-evaluated under SDA approval.
19 They will, they would be considered, they 20 could be potentially considered as sources on 21 certainty. You know, that would have to be 22 re-evaluated in this Topical Report as it impacts the 23 results.
24 CHAIRMAN REMPE: Yes, the -- again, maybe 25
99 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the SDA just like the DC would make it through that 1
hoop if we don't consider that there's this, they may 2
not have an emergency planning zone option.
3 And we might, what I'm wondering is if like 4
Dave was saying, maybe some guidance is needed for 5
accident event selection. Maybe we ought to say that 6
we get, somebody may say I want a 25 mile emergency 7
planning zone or ten mile or whatever.
8 But maybe that there needs to be some 9
guidance about and you've said that we want a spectrum 10 of events not just cut off frequency and that would 11 be a good way to address what I think is my concern.
12 And then having a peer review of the 13 phenomena for addressing that concern for this would 14 be something that would help too. But again, maybe 15 that's the ultimate answer is having some sort of 16 guidance document that say there's an additional 17 considerations because if an applicant comes in and 18 says I don't need an emergency planning zone.
19 Does that make sense and what are your 20 thoughts on something like that?
21 MR. VASAVADA: This is Shilp. I think we 22 will have to take that back. I mean, the point about 23 guidance, yes, it makes sense, but and we'd have to 24 take that back electively and make a decision of where 25
100 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 we land and how do we need this? I don't think at least 1
I can give you an answer right now.
2 CHAIRMAN REMPE: It's beyond the scope of 3
this Topical Report although we can say guidance is 4
needed in our letter if that's what the Committee wants.
5 But I just think that where this is going 6
that the Staff may want to think about it and how to 7
anticipate what could occur for something like this 8
in some cases.
9 MEMBER PETTI: I still anticipate that the 10 advanced reactors will engineer away the internal 11 events if you will. And that's why the seismic stuff 12 here is so important because it really sort of breaks 13 some new ground and it's going to dominate I think when 14 you look at the advanced reactors.
15 CHAIRMAN REMPE: But there's always the 16 unknown unknowns and then if you can have a way to say 17 18 MEMBER PETTI: It's like, Joy, but Joy, 19 we're supposed to be risk informed. The unknown 20 unknowns out there at a level, right now, was it forward 21 as a magnitude and frequency between the internal events 22 and the seismic. Okay, we're off.
23 By a factor of a hundred, by a factor of 24 a thousand and seismic still dominates. And that's 25
101 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the perspective --
1 CHAIRMAN REMPE: Right.
2 MEMBER PETTI: -- that I think we just have 3
to keep in mind.
4 CHAIRMAN REMPE: And what I believe in 5
analysis that --
6 MEMBER PETTI: Well we --
7 CHAIRMAN REMPE: -- but unplanned things 8
happen and then I want to be able to expand.
9 MEMBER PETTI: But Joy, you can't, you 10 can't in my opinion, you can't, you can't regulate 11 unknown unknowns.
12 CHAIRMAN REMPE: But you need to have the 13 take that the --
14 MEMBER PETTI: And it depends on --
15 CHAIRMAN REMPE: -- NEI said.
16 MEMBER PETTI: What do you mean, what do 17 you mean, I didn't understand what you meant by the 18 capability to expand.
19 CHAIRMAN REMPE: That's what's in the NEI 20 documents and the --
21 MEMBER PETTI: Well, tell me what that 22 means.
23 CHAIRMAN REMPE: -- Topical Report.
24 MEMBER PETTI: But I don't understand what 25
102 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 that means.
1 CHAIRMAN REMPE: Means that you make sure 2
that the outside agencies and that there's some way 3
of path even though you don't have drills, it means 4
you have a path and you've thought about it somehow.
5 What you would do --
6 MEMBER PETTI: To make sure that, to make 7
sure -- so similar to what we've already been doing.
8 CHAIRMAN REMPE: Absolutely.
9 MEMBER PETTI: Okay.
10 CHAIRMAN REMPE: That's where I'm going.
11 MEMBER PETTI: I just didn't understand 12 that logic and --
13 CHAIRMAN REMPE: That's where I'm going 14 and I -- just thinking of the future where it could 15 go. Okay?
16 MR. VASAVADA: I just wanted to add again 17 18 CHAIRMAN REMPE: Sorry we're arguing.
19 MEMBER PETTI: No, we're not.
20 MR. VASAVADA: Because you brought up 21 this, the Topical Report is only for the EPZ sizing 22 and then some EPZ that need to be met after the, after 23 we --
24 MEMBER DIMITRIJEVIC: Sorry, I cannot hear 25
103 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 you.
1 MEMBER KIRCHNER: Use your mics please.
2 CHAIRMAN REMPE: Okay. You'll have to get 3
close to your mic.
4 MR. VASAVADA: Okay. I just wanted to 5
reiterate that this Topical Report and the slide, on 6
the side this is Shilp Vasavada from the NCR Staff.
7 The Topical Report is only about EPZ size.
8 CHAIRMAN REMPE: I agree.
9 MR. VASAVADA: The other elements of EP, 10 emergency planning, are not within the scope. They 11 still have to be met, regulations still have to --
12 CHAIRMAN REMPE: But right now we're 13 looking at everybody wants to try and reduce what the 14 requirements are and I'm just looking at where it's 15 all kind of coming together and pointing toward that 16 additional review of the phenomena is also one of the 17 things that it falls into that.
18 DR. SCHULTZ: This is Steve Schultz. The 19 major requirement here is that the applicant has to 20 perform a site specific seismic PRA and use this 21 technical report to perform the evaluation to determine 22 whether they can do anything associated with the 23 emergency planning zone limits.
24 MR. VASAVADA: Not just seismic. You're 25
104 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 right. But also site specific PRA is part of the --
1 DR. SCHULTZ: Yes, and it has issues too.
2 MR. VASAVADA: -- part of the NuScale.
3 DR. SCHULTZ: But that all has to be done 4
as part of the application.
5 MR. VASAVADA: Correct.
6 DR. SCHULTZ: As you indicated in the 7
safety evaluation.
8 MR. VASAVADA: That's correct and the 9
conditions of use have to be met so an applicant has 10 to demonstrate all of that.
11 MEMBER KIRCHNER: Other questions? At 12 this point let me take a pause here and turn to the 13 public. This is an opportunity for public comment.
14 If you would like to make a comment, please state your 15 name and make your comment.
16 And I think for those of you on Teams, just 17 unmute your microphone and for those of like listening 18 in for on the bridge line, I think you have to press 19 star six to unmute.
20 We have about 15 seconds here for someone 21 to make a comment. I'm not hearing anyone out there.
22 One last time, any public comments? Okay, thank you.
23 At this point, I think we need to take a break.
24 We have from both the applicant and the 25
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Staff closed presentations. There's none, I don't know 1
if you during the time of the break and organize your 2
questions, but this will give you another opportunity 3
if you have some questions that you would like to ask 4
today before next month when we go to a letter writing 5
exercise.
6 MEMBER DIMITRIJEVIC: Yes, after I hear 7
8 MEMBER KIRCHNER: So with that --
9 MEMBER DIMITRIJEVIC: Yes. Right after 10 I hear the new schedule presentation too. Okay?
11 MEMBER KIRCHNER: Okay. So with that, let 12 us close the open session, take a break for 15 minutes 13 and then come back and we'll be in closed session for 14 those presentations and any final questions. Okay, 15 Larry, yes, I see your hand up. Thank you.
16 MR. BURKHART: Yes, I just wanted to say 17 that depending on what the Chairman and the Committee 18 decide, the Committee may go into letter report writing 19 and later on and that would be in the public. So we 20 may be back --
21 MEMBER KIRCHNER: Yes.
22 MR. BURKHART: -- on this line so I don't 23 know if the Chairman wanted to say anything about that.
24 CHAIRMAN REMPE: It depends on how long 25
106 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 it takes. I'd rather just hold off if that's okay, 1
Larry.
2 MR. BURKHART: Oh, it's totally up to the 3
Committee. There is the option of going to report 4
writing if things do --
5 MEMBER MARCH-LEUBA: Keep it open. Keep 6
the possibility open.
7 MR. BURKHART: Yes.
8 CHAIRMAN REMPE: Yes, keep the possibility 9
open.
10 PARTICIPANT: Keeps us out on that.
11 CHAIRMAN REMPE: Yes, and just somebody 12 can maybe you could get Quynh to -- or you could put 13 some messages out, Larry.
14 MR. BURKHART: We can do that. We'll do 15 that.
16 CHAIRMAN REMPE: Thank you.
17 MEMBER KIRCHNER: Thank you. We are on 18 recess for the moment.
19 (Whereupon, the above-entitled matter 20 went off the record at 3:48 p.m.)
21 22 23 24 25
1 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Emergency Planning Zone (EPZ)
Licensing Topical Report (LTR)
ACRS Subcommittee Meeting (Open Session)
September 8, 2022 Liz English, Licensing Supervisor Jeremiah Doyle, EPZ Technical Lead, PRA
2 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Acknowledgement and Disclaimer This material is based upon work supported by the Department of Energy under Award Number DE-NE0008928.
This presentation was prepared as an account of work sponsored by an agency of the United States (U.S.)
Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.
3 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Agenda
- Purpose
- Introduction
- Overview of NuScale topical report TR-0915-17772, Revision 3
- Summary
4 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Purpose
- Present content of NuScale topical report TR-0915-17772, Revision 3
- Provide a general understanding of the NuScale method to identify a spectrum of accident sequences and the associated severe accident and dose consequence analyses that form the basis for sizing plume exposure pathway (PEP) emergency planning zones (EPZs) surrounding NuScale plant sites
5 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Introduction
- Topical report provides a method for determining the size of the off-site PEP EPZ surrounding NuScale plant sites
- Applicable to NuScale small module reactor (SMR) designs only
- Consistent with the technical basis in NUREG-0396 and WASH-1400 o Identifies and evaluates a spectrum of accident sequences and potential releases o Satisfies the same dose criteria at and beyond the EPZ boundary to provide an equivalent level of protection to the health and safety of the public o Risk-informed, consequence based method based on a combination of quantitative evaluation and qualitative engineering judgement
- Implements state-of-the-art codes and methods established in the 40+ years since the development NUREG-0396 and WASH-1400
- Designed to be self-contained, consistent, and repeatable
6 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Conditions of Applicability
- Applicable to only the NuScale SMR designs o small modular integral pressurized light water reactors, o operating modules partially immersed in water that serves as the ultimate heat sink (UHS),
o the UHS is retained below grade in a structure with up to 12 reactor modules per UHS, o a safe shutdown earthquake with a peak ground acceleration of 0.5g, and o structures, systems, and components (SSCs) capable of performing their safety functions without AC electric power, DC electric power, or operator actions for at least 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following a design basis event.
o Condition 1: The PRA addresses internal and external hazards and all operating modes o Condition 2: The PRA is demonstrated to be technically acceptable for this purpose
7 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Overview of the NuScale EPZ Method
- Quantitative evaluation o Identify the spectrum of accidents sequences that form the basis of EPZ sizing Core damage design basis source term (DBST) from final safety analysis report (FSAR) Ch 15 Probabilistic risk assessment (PRA) single and multi-module sequences from FSAR Ch 19 Other radiological releases outside of the DBST and PRA o Identify accident severity o Calculate the time-dependent source term to the environment o Final EPZ distance is the smallest distance at which all dose criteria are satisfied Criterion a - total effective dose equivalent (TEDE) dose from the DBST 1 rem mean and 5 rem 95th percentile Criterion b - TEDE dose from less severe accidents 1 rem mean and 5 rem 95th percentile Criterion c - substantial reduction in early health effects, acute whole body dose from more severe accidents 200 rem
- Qualitative evaluation o Evaluation of plant-level defense-in-depth against INSAG-10 and RG 1.174 o Review and disposition of key assumptions and uncertainties in the underlying PRA Basis:
8 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Overview of the NuScale EPZ Method Quantitative Evaluation Non-Seismic Single Module Screening Process (Sections 3.4.3)
Determine severity of screened in sequences (Section 3.4.5)
Multi-Module Assessment Process (Section 3.4.4)
Source Term Evaluation (Section 4.2)
Dose Evaluation (Section 4.2)
Source Term and Dose Uncertainty Analysis (Section 4.3)
DBA and Less Severe Determine distance(s) where Dose Criteria a and b are exceeded (Section 3.2)
More Severe Determine distance(s) where Dose Criterion c is exceeded (Section 3.2)
PRA Input All Internal and External Event Sequences (Section 3.4.1)
DBA Input Design Basis Source Term (Section 3.3)
Largest EPZ radius Seismic Single Module Screening Process (Sections 3.4.2)
Other Risks (Section 3.5)
9 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Spectrum of Accidents Design basis source term (DBST) from FSAR Ch 15 Severe accidents from the site and design-specific PRA o Identify non-seismic single module and multi-module sequences with core damage frequency (CDF) 1E-07 per year Screening at 1E-07 captures a spectrum of accidents with similar frequencies to the EPZ basis in NUREG-0396 Use of CDF as the screening mechanism conservatively ignores the conditional probability of radionuclide release o Non-seismic sequence uncertainty against screening threshold considered consistent with NUREG-1855 Retain sequences with point-estimate CDF > 1E-08 and 95th percentile CDF > 1E-07 Ensures cliff-edge sequences are captured in the spectrum of accident sequences Other releases - potential radionuclide releases not captured by the DBST and PRA o For example: spent fuel pool risks or mechanical damage to the fuel o One of the following criteria are met The release meets the dose-based criteria for the appropriate accident severity The consequences of the release are bounded by the DBST and screened-in PRA sequences Accident severity o Intact containment accidents are less severe o Containment failure or bypass accidents are more severe Basis:
NUREG-0396 WASH-1400 NUREG-1855
10 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Off-site Dose Consequences
- Dose criteria provide level of protection to the public that meets or exceed the basis in NUREG-0396 o Criterion a - total effective dose equivalent (TEDE) dose from the DBST 1 rem mean and 5 rem 95th percentile o Criterion b - TEDE dose from less severe accidents 1 rem mean and 5 rem 95th percentile o Criterion c - substantial reduction in early health effects, acute whole body dose from more severe accidents 200 rem
- Modeling of dose receptors consistent with the NUREG-0396 basis o Stationary individual located:
outdoors in the azimuthal direction of maximum exposure at and beyond the site boundary distance o No sheltering, relocation, or evacuation o Cloudshine, groundshine, inhalation, resuspension inhalation, and skin deposition dose pathways No shielding from cloudshine, inhalation, and skin deposition Natural groundshine shielding due to variations in terrain o 96 hour0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> exposure for TEDE, 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> exposure for acute red marrow o Parametric evaluation of uncertainty in source term and dose calculations Basis:
11 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Defense-in-Depth Evaluation and Review of PRA Uncertainties
- Defense-in-depth evaluation using the guidance in INSAG-10 and RG 1.174 o Highlight design features and SSCs available to prevent and mitigate the consequences of postulated accidents o Confirms the existence, functionality, and capability of features and strategies to provide confidence in the acceptably low plant risk and demonstrate protection of the health and safety of the public
- Review of PRA Uncertainties o Complete a review of the assumptions and sources of uncertainty in the underlying PRA to identify and address any potential impact to EPZ sizing Key assumptions in the PRA Model uncertainty Completeness uncertainty Basis:
12 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Summary
- Topical report provides a method for determining PEP EPZs surrounding NuScale plant sites consistent with the EPZ technical basis in NUREG-0396 and WASH-1400
- Provides a level of protection to the public that meets or exceeds the NUREG-0396 EPZ basis
- Applicable to NuScale SMR designs only
13 PM-120945 Rev. 0 Copyright © 2022 NuScale Power, LLC.
NuScale Nonproprietary Acronyms CDF core damage frequency DBST design basis source term EPZ emergency planning zone FSAR final safety analysis report LTR licensing topical report PEP plume exposure pathway PRA probabilistic risk assessment RAI request for additional information SMR small modular reactor SSC structures, systems, and components TEDE total effective dose equivalent UHS ultimate heat sink
Staff Presentation to the ACRS Sub-Committee NuScale Licensing Topical Report Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones at NuScale Small Modular Reactor Plant Sites (TR-0915-17772, Revision 3)
Open Session SEPTEMBER 8, 2022
2 Topical Report Review Chronology NuScale submitted topical report TR-0915-17772, Revision 2, Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones, on August 4, 2020 NRC issued requests for additional information (RAIs) 9828 and 9830 in April 2021 Initially, TR was applicable to light-water small modular reactors (SMRs) and non-light water reactors (non-LWRs). In May 2021, in response to RAI 9830, NuScale removed applicability to non-LWRs.
NRC performed a regulatory audit as part of its review of the methodology in Revision 2, from November 2021 to April 2022 NuScale provided response to RAI 9828 and submitted Revision 3 of the TR on June 10, 2022, titled Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones at NuScale Small Modular Reactor Plant Sites, applicable only to the NuScale design and its derivatives and incorporating the RAI responses NRC issued the advanced safety evaluation on August 8, 2022
3 NRC Staff Reviewers:
Marie Pohida, Sr. Reliability and Risk Analyst, NRR/DRA/APLC Shilp Vasavada, Sr. Reliability and Risk Analyst, NRR/DRA/APLC Elijah Dickson, Sr. Reliability and Risk Analyst, NRR/DRA/ARCB Raymond Hoffman, Emergency Preparedness Specialist, NSIR/DPR/RLB Todd Smith, Sr. Level Advisor for Emergency Preparedness, NSIR/DPR Project Managers:
Alina Schiller, TR Project Manager, NRR/DNRL/NRLB Getachew Tesfaye, Sr. Project Manager, NRR/DNRL/NRLB
Outline Regulatory and technical basis for staffs evaluation Overview of TR methodology Dose-distance criteria and figures-of-merit (FoMs)
Source term and consequence assessment Screening of Probabilistic Risk Assessment (PRA) sequences Treatment of uncertainty Conditions of use 4
Regulatory and Technical Basis for Staffs Evaluation 10 CFR 50.47, Appendix E to Part 50, 10 CFR Part 20 Probabilistic Risk Assessment (PRA) Policy Statement SRM-SECY-98-144 RG 1.174 RG 1.200 NUREG-0396 (1978) 5
NUREG-0396 (1978) 6
- Identifies the purpose of the EPZ
- Area within which prompt protective actions may be necessary to provide dose savings in the event of a radiological release
- Technical basis for current prescribed plume exposure pathway EPZ radius of 10 miles
- Based on a review of licensed design-basis events and a spectrum of accident sequences from WASH-1400
7 Staffs Method of Review
- Consistent with technical basis in NUREG-0396
- Consistent with risk-informed decision making and use of PRA in risk-informed applications
- Supported by regulatory audit
- Included example calculations implementing nearly entire methodology
8 Staffs Review of Applicability of NuScales EPZ TR Methodology
- Only applicable to NuScale design and its derivatives, including Standard Design Approval
- TR Section 2.5.1 provides high-level design characteristics that determine applicability
- All characteristics must be met
- Applicability limitations are acceptable
- High-level design characteristics capable of identifying NuScale designs with the features and risk profile considered by the staff in its review
9
- Considered recent research efforts to re-assess current 10-mile EPZ technical bases in NUREG-0396
- Considered updated information from guidance, methods, models, and analytical tools
- Assessed TR methodology consistency with analyses, assumptions and considerations of NUREG-0396 and current information
- Important topic areas:
- Radiological consequence assessment modeling approaches
- Dosimetric criteria and dose-distance curves
- Considerations derived from assessments Staffs Review Approach for Dose-Distance Criteria and FoMs
10 Dose-Distance Criteria and FoMs1 Criterion Description Source Term Figure of Merit and Acceptance Criteria a
Encompass those areas in which projected dose from DBAs could exceed the early phase PAGs NUREG-0800 Chapter 15 analysis 1 rem and 5 rem TEDE over 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />, consistent with the EPA PAG Manual early phase PAGs b
Encompass those areas in which consequences of less severe accident (containment intact) sequences could exceed the early phase PAGs PRA-specific accident sequences with MELCOR analyses utilizing mitigation design features and operator actions 1 rem and 5 rem TEDE over 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />, consistent with the EPA PAG Manual early phase PAGs c
Sufficient size to provide for substantial reduction in early severe health effects in the event of more severe accident sequences PRA-specific accident sequences with MELCOR analyses and separate effects models utilizing additional mitigation design features and operator actions 200 rem red marrow dose, within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, is less than the TR specified acceptance criteria, consistent with NUREG-0396 1 - See staff report, Use of MACCS Dose Coefficient Files to Compute Total Effective Dose Equivalent, which provides information on how to compute TEDE and red marrow FOMs using the MACCS computer code. (ADAMS Accession No. ML21211A584)
11
- For source term and radiological consequence analyses, the TR:
- Recommends computational codes such as MELCOR and RELAP to develop design-specific source terms
- Requires the MACCS code to perform radiological consequence analyses
- The staff finds these computer codes to be appropriate to perform these analyses Staffs Review of Source Term and Radiological Consequence Analysis
12 Fundamentals of Event Selection for EPZ Sizing Consistent with NUREG-0396
- Spectrum of accidents licensing and design against QHOs
- Spectrum of accidents for EPZ sizing includes characteristics of radiological consequences from DBAs and BDBAs
- Includes some of the key characteristics of more severe accidents (with large releases)
- Ensures capability to reduce early severe health effects (injuries or deaths) in the event of the most severe BDBAs
- Selection of spectrum of accidents for EPZ sizing does not alter the design or operation
13 Fundamentals of Event Selection for EPZ Sizing Consistent with NUREG-0396 (contd)
- Purpose of EPZ is dose savings and not dose avoidance
- NUREG 0396: while the EPZ should not be solely dependent on the most severe and most improbable BDBEs, the determination of the EPZ size needs to include some of the key characteristics of very large releases.
- Seismic risk expected to dominate NuScale risk profile and EPZ sizing
- Design reduces the risk from internal events
- Timing of seismically-initiated sequences different compared to non-seismic events
- Inclusion in spectrum of accidents maintains consistency with NUREG-0396
14 Seismic Risk - Potential Dominant Contributor for the NuScale Design NuScale Core Damage Frequency (per year)
Profile Without Seismic Contribution Estimated NuScale Core Damage Frequency (per year) Profile for Site Within NuScale Certified Design Response Spectrum 3E-10 6E-11 1E-09 9E-10 7E-10 9E-10 9E-08 Internal Events Internal Floods Internal Fires High Winds (Tornado)
High Winds (Hurricane)
External Floods Module Drop 3E-10 6E-11 1E-09 9E-10 7E-10 9E-10 9E-08 9E-07 Internal Events Internal Floods Internal Fires High Winds (Tornado)
High Winds (Hurricane)
External Floods Module Drop Representative Seismic
15 Staff Review of Non-Seismic Single Module Sequence Screening
- TR sequence screening of 1E-7 per reactor year CDF would have screened in all the WASH-1400 release sequences
- None of these release sequences had a frequency less than 1E-7 per reactor year
16 Staff Review of Consideration of Multi-Module Impacts for Non-Seismic Hazards
- WASH 1400 did not explicitly model common mode mechanisms such as fire, flood, and tornadoes (which have the potential to impact multiple modules) in the event trees and fault trees
- Appendix IV of WASH 1400: common mode mechanisms were assessed as impacts on the system fault trees
- Core damage sequence screening of 1E-7 per reactor year was also applied to multi-module core damage sequences
- None of WASH 1400 release sequences had a frequency less than 1E-7 per reactor year
17 Staff Review of Screening Threshold for Seismic Hazard in TR, Revision 2
- Proposed threshold was 1E-5 per year initiating event frequency
- Proposed threshold did not provide spectrum of accidents consistent with NUREG-0396
- Negligible beyond design basis seismic risk
- Excluded key characteristics of more severe seismic accidents
- Risk gap in EPZ sizing insights
- Proposed threshold was inconsistent with technical basis in NUREG-0396 and consideration of seismic events in WASH-1400
18 Staff Review of Screening Threshold for Seismic Hazard in TR, Revision 3
- TR identified a proprietary screening threshold for seismic hazard
- Risk gap approach developed by staff for evaluation
- Determine appropriateness of screening threshold for seismic hazard consistent with basis in NUREG-0396 Beyond Design Basis Seismic Risk 0%
100%
1E-5/year initiating event frequency
>2.0g acceleration
19 Staff Review of Screening Threshold for Seismic Hazard in TR, Revision 3 (contd)
- Overview of risk gap approach
- Step 1: Collect ensemble of hazard curves representing different sites within the certified seismic design response spectrum
- Step 2: Identify plant-level fragility and spectral ratios
- Step 3: Convolve hazard curves with plant-level fragility
- Step 4: Calculate simple average absolute and relative risk gap below screening threshold value
20 Staff Review of Screening Threshold for Seismic Hazard in TR, Revision 3 (contd)
- Staff evaluation used risk gap approach with 9 operating reactor sites
- Within NuScale Certified Seismic Design Response Spectra
- Using NuScale high confidence of low probability of failure (HCLPF) plant-level fragility
- Threshold captures 20% - 50% of seismic risk for the NuScale design across majority of 9 sites
21 Staff Review of Screening Threshold for Seismic Hazard in TR, Revision 3 (contd)
Figure 1 in NRC staffs safety evaluation (ML22118A760)
22 Staff Review of Screening Threshold for Seismic Hazard in TR, Revision 3 (contd)
- Achieves consistency with NUREG-0396 and WASH-1400 for seismic events
- Results in a complete spectrum of accidents
- Avoids extremely unlikely seismic accelerations
- Does not penalize NuScale for its risk profile
- Addresses multi-module risk (details in subsequent slide)
- Uses quantified seismic sequences because they can be dominant contributor to plant risk and EPZ sizing
23 Technology-Inclusive Applicability of Risk Gap Approach for Risk-Informed EPZ Sizing
- Provides design-and site-specific screening threshold value(s) consistent with technical basis in NUREG-0396
- Single value across technologies and sites is difficult to defend
- Uses accessible design-specific information
- This approach provides regulatory stability
24 Staff Review of Treatment of Uncertainty in Screening Threshold for Seismic Hazard
- Sufficient to identify new insights
- Addresses uncertainty in context of identification of spectrum of accidents for EPZ sizing
- Addresses potential for cliff edge effect (i.e., large change in EPZ size decision with small change in event screening)
- New sequences included in remaining steps of methodology
25 Staff Review of Consideration of Multi-Module Impacts for Seismic Hazard
- Methodology appropriately identifies and includes multi-module impacts from seismic events
- Considerations in staff evaluation:
- Seismic events are a common-mode initiator
- Screening threshold results in inclusion of accelerations with potential multi-module impacts
- Dominant contributors to NuScales seismic large release frequency impact multiple modules
- Impact of multi-module sequences reflected in source term for those sequences
26 Information at Various Licensing Stages Under 10 CFR 52 Design Certification Combined License Fuel Load Part 52:
EPZ TR:
PRA Based Seismic Margins Analysis (SMA) Allowed Not Applicable PRA Based SMA Allowed Site-Specific Seismic PRA Site-Specific Seismic PRA Site-Specific Seismic PRA
27 Staffs Review of Treatment of Modeling Uncertainty for Seismic and Non-Seismic Hazards and Staff Review
- TR contains broad discussion of consideration of assumptions and sources of uncertainty in the underlying PRA
- Staff determined that consistency with established guidance applied for voluntary risk-informed applications is important
- RG 1.200, Revision 3 and NUREG-1855, Revision 1
- Includes a corresponding Condition of Use
28 Staff Review of Consideration of Defense-In-Depth
- Methodology identifies key plant design and operational characteristics necessary for achieving defense-in-depth
- Includes consideration of severe accident management strategies and diverse and flexible coping strategies
- Five levels of defense in INSAG-10 adds confidence in consideration of defense-in-depth
29 Staffs Conditions of Use
- Ensure user addresses key inputs for methodology and staff findings
- Eight (8) conditions of use:
A.
Consistency in use between applicant for operating license application under Part 50 and COL under Part 52 B.
Consistency of PRA technical acceptability with established guidance C.
Treatment of PRA key assumptions and sources of uncertainty consistent with established guidance D.
Limit seismic event screening threshold to sites with GMRS bounded by NuScales CSDRS E.
Limit seismic event screening threshold to NuScales HCLPF plant-level fragility F.
Demonstration of GMRS and HCLPF plant-level fragility at application and prior to fuel-load G.
Monotonic decrease of 200 rem dose exceedance curve H.
Periodic evaluation to ensure (1) E is met AND (2) conclusion on EPZ size remain valid. Periodicity consistent with 10 CFR 50.71(h)(2)
30 Staffs Conclusion
- TR methodology is generally consistent with technical basis of current 10-mile EPZ prescribed in 10 CFR 50.47 (i.e., NUREG-0396)
- Reasonable assurance that methodology is adequate for assessing plume exposure pathway EPZ sizing
- Applicants using the methodology as the technical basis for assessing plume exposure pathway EPZ sizing need to meet :
- Scope of applicability in Section 2.5 of the TR
- Conditions of Use listed in Section 5.0 of staffs SE
31 Staffs Conclusion (contd)
- NuScale EPZ TR is risk-informed and reflective of NUREG-0396 approach
- Uses risk information from design-and site-specific PRAs, with explicit consideration of uncertainty
- Explicitly addresses defense-in-depth
- Staff evaluated impact on safety margins
- Includes performance monitoring (based on corresponding Condition of Use)
32 Caveats on Scope of Staffs Findings
- Not extended to design and operation for licensing
- Quantitative Health Objectives applicable for design and operation for licensing
- Screening threshold, especially for the seismic hazard, not applicable to PRA development
- Follow applicable endorsed PRA Standard
- Does not define credible events for any hazard
33 Acronyms BDBA/E beyond design basis accident/event CDF core damage frequency CSDRS certified seismic design response spectrum DBA design basis accident EPZ emergency planning zone GMRS ground motion response spectrum HCLPF high confidence of low probability of failure LERF large early release frequency LRF large release frequency LWR light water reactor Non-LWR non-light water reactor ONT other nuclear technology PRA probabilistic risk assessment QHO quantitative health objective RG regulatory guide SMR small modular reactor WASH-1400 Nuclear Regulatory Commission Reactor Safety Study, 1975
34 References 10 CFR 50.47 Emergency Plans 10 CFR Part 50 Appendix E Emergency Planning and Preparedness 10 CFR Part 20 Standards for Protection Against Radiation NUREG-0396, Planning Basis For The Development Of State And Local Government Radiological Emergency Response Plans In Support Of Light Water Nuclear Power Plants (ML051390356)
Use of Probabilistic Risk Assessment Methods in Nuclear Regulatory, 60 FR 42622 SRM-SECY 98-144, White Paper Risk Informed and Performance-Based Regulation (ML003753601)
Regulatory Guide (RG) 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, Revision 3 (ML17317A256)
RG 1.200, Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities, Revision 3 (ML20238B871)