ML22060A133

Transcript of the Advisory Committee on Reactor Safeguards 692nd Full Committee Meeting, February 3, 2022, Pages 1-58 (Open)

ML22060A133
Person / Time
Issue date:	02/03/2022
From:	Advisory Committee on Reactor Safeguards
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Abdullahi, Z, ACRS
References
NRC-1833
Download: ML22060A133 (58)

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Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION

Title:

Advisory Committee on Reactor Safeguards Docket Number: (n/a)

Location: teleconference Date: Thursday, February 3, 2022 Work Order No.: NRC-1833 Pages 1-44 NEAL R. GROSS AND CO., INC.

Court Reporters and Transcribers 1716 14th Street, N.W.

Washington, D.C. 20009 (202) 234-4433

1 1

2 3

4 DISCLAIMER 5

6 7 UNITED STATES NUCLEAR REGULATORY COMMISSIONS 8 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 9

10 11 The contents of this transcript of the 12 proceeding of the United States Nuclear Regulatory 13 Commission Advisory Committee on Reactor Safeguards, 14 as reported herein, is a record of the discussions 15 recorded at the meeting.

16 17 This transcript has not been reviewed, 18 corrected, and edited, and it may contain 19 inaccuracies.

20 21 22 23 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com

1 1 UNITED STATES OF AMERICA 2 NUCLEAR REGULATORY COMMISSION 3 + + + + +

4 692ND MEETING 5 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 6 (ACRS) 7 + + + + +

8 THURSDAY 9 FEBRUARY 3, 2022 10 + + + + +

11 The Advisory Committee met at the Nuclear 12 Regulatory Commission, Two White Flint North, Room 13 T2B1, 11545 Rockville Pike, at 8:30 a.m., Joy L.

14 Rempe, Chairman, presiding.

15 16 COMMITTEE MEMBERS:

17 JOY L. REMPE, Chairman 18 WALTER L. KIRCHNER, Vice Chairman 19 DAVID A. PETTI, Member-at-Large 20 RONALD G. BALLINGER, Member 21 VICKI M. BIER, Member 22 CHARLES H. BROWN, JR., Member 23 VESNA B. DIMITRIJEVIC, Member*

24 GREGORY H. HALNON, Member 25 JOSE A. MARCH-LEUBA, Member NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

2 1 MATTHEW W. SUNSERI, Chairman 2

3 ACRS CONSULTANT:

4 STEPHEN SCHULTZ 5

6 DESIGNATED FEDERAL OFFICIAL:

7 HOSSEIN NOURBAKHSH 8

9 10 11 12 13 14 15 16 17 18 *Present via teleconference 19 20 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

3 1 P R O C E E D I N G S 2 (8:30 a.m.)

3 CHAIRMAN REMPE: Okay, this meeting will 4 now come to order. This is the second day of the 5 692nd meeting of the Advisory Committee on Reactor 6 Safeguards. I'm Joy Rempe, Chairman of the ACRS.

7 Members in attendance are Ron Ballinger, Matt Sunseri, 8 Dave Petti, Walt Kirchner, Vicki Bier and Jose March-9 Leuba. We are expecting to soon be joined by Charlie 10 Brown, Greg (Pause.)

11 MR. NGUYEN: Chairman Rempe, I think we 12 lost you after Greg. (Pause.) Can anyone externally 13 confirm my assertion?

14 MR. SNODDERLY: Yes, Quynh, we can't hear.

15 (Simultaneous speaking.) We cannot hear the ACRS 16 members though in the room.

17 MR. NGUYEN: (Pause.) I texted the 18 chairman, letting her know when we lost her.

19 MR. SNODDERLY: Thanks, Quynh. This is 20 Mike. Did you want me to text Larry or Scott and let 21 them --

22 MR. NGUYEN: Sure. Thanks, man.

23 MR. SNODDERLY: All right, I'll do that.

24 (Pause.) There we go.

25 MR. NGUYEN: Thank you. (Pause.) Good NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

4 1 morning, I've been notified that Headquarters has 2 lost internet capability, so --

3 UNKNOWN FEMALE: Who's talking?

4 UNKNOWN MALE: Quynh.

5 UNKNOWN MALE 2: That's Quynh that's 6 talking.

7 UNKNOWN FEMALE: I know, but who's got 8 their computer on?

9 UNKNOWN MALE 2: Me.

10 UNKNOWN FEMALE: Okay, tell them that 11 we're trying.

12 UNKNOWN MALE 2: All right.

13 MR. NGUYEN: Yes, we can hear you now.

14 UNKNOWN MALE 3: We got you.

15 CHAIRMAN REMPE: So we're going through 16 (Simultaneous speaking.) Matt's computer, should we 17 go ahead and finish the intro if you can hear me?

18 MR. NGUYEN: Yes, we lost you after you 19 were announcing Greg.

20 CHAIRMAN REMPE: Okay. (Simultaneous 21 speaking.) So, Matt, should I just come over there by 22 you?

23 MEMBER SUNSERI: Yes, yes, sure.

24 CHAIRMAN REMPE: This isn't good.

25 (Pause.)

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5 1 UNKNOWN MALE 3: Okay, so one is the boss 2 and one is the rest? Okay.

3 CHAIRMAN REMPE: Okay, so this is Joy 4 Rempe again. I apologize that we lost internet 5 connectivity. We still do not have it on the main 6 computer. We're going through an individual member's 7 computer and (Simultaneous speaking.) we'll just cope 8 with this as we can. But, I believe, Quynh, you said 9 we lost the connectivity when I was announcing that 10 Greg Halnon, Vesna Dimitrijevic, and Charles Brown 11 will be joining us later and they have been excused 12 from the initial part of the meeting. But we do have 13 a quorum.

14 Similar to yesterday, the committee is 15 primarily meeting in person with some ACRS staff, NRC 16 staff and participants attending virtually.

17 The ACRS was established by the Atomic 18 Energy Act and is governed by the Federal Advisory 19 Committee Act. The ACRS section of the US NRC public 20 website provides information about the history of the 21 committee and documents, such as our Charter, bylaws, 22 Federal Register notices for meetings, letter reports 23 and transcripts of open portions of our full and 24 subcommittee meetings, including all slides presented 25 at these meetings.

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6 1 The committee provides its advice on 2 safety matters to the commission through its publicly 3 available letter reports. The Federal Register notice 4 announcing this meeting was published on December 28, 5 2021. This announcement provided an agenda and 6 instructions for interested parties to provide written 7 documents or request opportunities to address the 8 committee. We have received no written comments or 9 requests to make oral statements from members of the 10 public regarding today's session.

11 A communication channel has been opened to 12 allow members of the public to listen in on the 13 committee discussion and we periodically open the 14 meeting to accept comments for participants listening 15 to our meetings. Written comments, if not previously 16 provided, may still be forwarded to Dr. Hossein 17 Nourbakhsh, the designated federal officer for today's 18 meeting.

19 During today's meeting, the committee will 20 consider the following topic: Holtec Spent Fuel Pool 21 Heat Up Calculation Methodology Topical Report. A 22 transcript of the meeting is being kept and I request 23 that speakers identify themselves and speak with 24 sufficient clarity and volume so that they can be 25 readily heard. Additionally, participants should mute NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

7 1 themselves when not speaking.

2 At this time, I'd normally ask Hossein 3 Nourbakhsh to lead us through the discussion, but we 4 have an internet connectivity issue and so I'm going 5 to reboot the system and rejoin the meeting. We hope 6 we get internet connectivity, but we do not have it on 7 the main system at this time. So, stay tuned and 8 we're going to have a bit of a break, okay?

9 MEMBER MARCH-LEUBA: So, we are on recess?

10 CHAIRMAN REMPE: Yes (Simultaneous 11 speaking.).

12 MEMBER MARCH-LEUBA: You're talking to 13 this microphone that helps.

14 CHAIRMAN REMPE: Yes. Okay so, we will 15 officially have a recess while we try and figure out 16 what's going to happen here.

17 (Whereupon, the above-entitled matter 18 went off the record at 8:36 a.m. and resumed at 8:44 19 a.m.)

20 CHAIRMAN REMPE: Thank you all for your 21 help remotely. Let's turn the meeting over to Member 22 March-Leuba to lead us through the Holtec discussion.

23 MEMBER MARCH-LEUBA: Thank you, Chairman 24 Rempe. I was going to start the meeting by saying 25 that, of course, we are going to be talking about the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

8 1 Holtec Spent Fuel Pool Methodology, and I was going to 2 tell Holtec and the staff that I maliciously told them 3 to prepare for a 20-minute presentation so I can now 4 graciously give them 50 percent over time, which we 5 already have used so I'll stick to the original 20 6 minutes.

7 Without further adieu, Ekaterina from the 8 staff is going to give us some opening remarks.

9 MS. LENNING: Good morning, Full Committee 10 Chairman, Full Committee members and staff. My name 11 is Ekaterina Lenning, Division of Operating Reactor 12 License and Office of Nuclear Reactor Regulation. I 13 am project manager for the Holtec International HI 14 2200 750, revision zero, Holtec Spent Fuel Pool Heat 15 Up Calculation Methodology Topical Report review.

16 Presenting today for the staff will be 17 Josh Kaizer, who is the lead technical reviewer for 18 this topical report, and Adam Rau, Division of Safety 19 System NRR.

20 I would to thank you for the opportunity 21 to present this staff review and evaluation of 22 Holtec's topical report and spent fuel pool heat up 23 calculation methodology. We look forward to today's 24 meeting and thank you again for the opportunity to 25 present.

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9 1 MEMBER MARCH-LEUBA: Thank you. I believe 2 we also have some introductions from Holtec management 3 or the staff and then we will move straight to the 4 technical presentation. Go ahead.

5 MR. TRICE: Good morning, my name is Kelly 6 Trice. I'm the President of Holtec Decommissioning 7 International.

8 We appreciate the opportunity to address 9 the ACRS Full Committee regarding the Holtec topical 10 report on the method for determining the spent fuel 11 assembly heat up during a theoretical drain down event 12 of a spent fuel. This topical report is important to 13 Holtec and our decommissioning process as it 14 measurably enhances nuclear safety by providing an 15 innovative, yet simple to calculate, methodology for 16 arranging the spent fuel in the pool, such that the 17 risk of zirconium fire reaction is eliminated sooner 18 than the traditional methodologies currently being 19 utilized in the industry.

20 We thank you for your time this morning 21 and look forward to a constructive discussion. Ms.

22 Andrea Sterdis and Dr. Stefan Anton will be our 23 presenters for both the open and closed sessions.

24 Thank you.

25 MEMBER MARCH-LEUBA: Dr. Anton, yes, go NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

10 1 ahead. Are you going to share your slides?

2 DR. ANTON: Yes, just a second. We will 3 be sharing the slides momentarily.

4 MEMBER MARCH-LEUBA: Excellent, thank you.

5 We see them now.

6 CHAIRMAN REMPE: So actually just to 7 interrupt real quick, I just want to confirm the court 8 reporter did start recording when we came back. I 9 forgot to say that we're back on the record. Could 10 the court reporter confirm that we are. (Non-verbal 11 response.) Thank you. Sorry about that, Jose, go 12 ahead.

13 MEMBER MARCH-LEUBA: Okay, Stefan.

14 DR. ANTON: Yes, thank you very much.

15 This is Stefan Anton. I'm the Vice President of 16 Engineering at Holtec International and I'm the author 17 of the topical report, where we will present some 18 details and the background here. Second slide, 19 please.

20 Okay, on a high level what is the purpose 21 of the topical report? It is to develop and provide 22 a methodology to proactively determine the best 23 overall spent fuel pool arrangement so that the risk 24 of a zirconium fire is eliminated as soon as possible 25 after a permanent defueling of a plant. This NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

11 1 methodology that can be then used, if it's 2 implemented, to gain a significant and real safety 3 benefit by reducing the time that such an event of a 4 zirconium fire would be feasible.

5 MEMBER MARCH-LEUBA: Doctor, just for the 6 benefit of the public --

7 DR. ANTON: Yes?

8 MEMBER MARCH-LEUBA: What you mean by as 9 soon as possible is this is a spent fuel pool and we 10 are putting spent fuel from the core into the pool.

11 You refer as the number of years that have passed 12 since the last time you loaded fuel from an active 13 core, that's correct?

14 DR. ANTON: That is correct. There is 15 basically the time in months or years after the fuel 16 has been loaded into the spent fuel from the core into 17 the spent fuel pool that has to pass before it can be 18 considered that a zirconium fire is no longer 19 feasible. That is the time that we are talking about 20 and our methodology will be allowing to minimize that 21 time compared to what is being used in the past. The 22 next slide.

23 A little bit more about what kind of 24 problem we are actually addressing here. If there is 25 a theoretical beyond design basis event of a drain NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

12 1 down of a spent fuel pool, so the loss of water then 2 of course, the cladding of the spent fuel assemblies 3 would heat up due to the fact that we don't have any 4 water cooling in the spent fuel pool.

5 Now we are concerned there about the 6 cladding temperature, that is our main concern, not 7 the fuel itself. If the cladding temperature exceeds 8 a certain value, there is the possibility of an 9 exothermal reaction with the air that is now replacing 10 the water and that possibly can result in what is 11 commonly called a zirconium fire or zirc fire. That 12 is at the heart of it and that is what we are trying 13 to show that it's not feasible after a certain period 14 of time. Next slide, please.

15 So what are the acceptance criteria and 16 what is generally the principle approach that is used 17 to evaluate that. The acceptance criteria is a 18 combination of a temperature and a time. The criteria 19 is namely that a cladding temperature, again, we're 20 talking about the fuel cladding does not exceed 900 21 degrees Celsius within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> from the start of the 22 drain down event. This is not something that we 23 developed within the topical report. This is a common 24 acceptance criteria that has previously used numerous 25 times, been accepted by the NRC and there are numerous NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

13 1 publicly available documentations that show where this 2 comes from and what the basis for this is. But just 3 in very short, the 900 degrees Celsius is one of the 4 temperature levels where certain reactions between the 5 air and the fuel cladding can occur and the 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> 6 that is based on the assumption that within a certain 7 period of time, there would be some remedies available 8 to limit the temperature so it is assumed that within 9 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, you can actually initiate some kind of a 10 cooling to the spent fuel pool. Again, that was not 11 developed as part of the topical report, this is 12 generally accepted acceptance criteria that you need 13 to meet.

14 MEMBER MARCH-LEUBA: May I stop you here 15 and have some discussion? We have some deliberations 16 after our Full Committee. That's why I asked the 17 question earlier to clarify in the mind of the public 18 the time you were talking two slides before was two or 19 three years after you unload the fuel from the core.

20 This time, this 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> that you are talking to now, 21 is time from the accident that made the pool drain.

22 So these are completely different times scale, hours 23 versus years.

24 DR. ANTON: That is correct. This is 25 different. This 10 hours would be in case you NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

14 1 actually have a drain down event that within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> 2 after that drain down initiated, that the cladding 3 does not reach 900 degree Celsius. The previous time 4 that we talked about is how long you have to wait 5 after loading spent fuel into the pool until you would 6 make sure that you don't reach 900 degrees Celsius 7 after 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.

8 MEMBER MARCH-LEUBA: Yes, so I had an 9 opportunity to educate myself a lot more deeper on 10 NUREG-1738, which is where these numbers are reports 11 of the criteria. The way I read that 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> is the 12 time necessary for evacuation of the personnel or the 13 public around the plant. It's not clear which 14 evacuation they are talking about. Not time to 15 restore the level.

16 MS. STERDIS: So this is Andrea Sterdis.

17 You're correct, Jose. What that is, is that's the 18 time that if you read in the NUREG-1738, it's been 19 concurred that if you have 10 hours from an 20 instantaneous drain down to the time that the fuel 21 would reach 900 degrees C, there's plenty of time for 22 alternate methods to get water into the pool to 23 prevent the zirc fire and then there's also sufficient 24 time that if the state and local officials determine 25 there's a protective action they want to implement, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

15 1 then there's time there to do that as well, so you're 2 correct.

3 MEMBER MARCH-LEUBA: Okay, so the NUREG 4 also has a sentence that says, I mean this NUREG is 5 difficult to read, I mean it took me several tries to 6 go over it. It's very noncommittal. Defined 7 temperatures of 800 and 900, 1,000, 1,200 depends on 8 the atmosphere, like if you have steam the temperature 9 is much higher than when you have only oxygen. But 10 there seems to be an agreement on the 900 degrees as 11 being a good cutoff. However, the NUREG warns that 12 the criteria should be judged based on the 13 application, so we'll go through that with the members 14 in the letter the way I wrote it. My recommendation 15 is going to be that this SER from the staff is 16 approving the methodology to calculate a temperature 17 at a given time. Whenever you want to apply it for a 18 license amendment request, you will have a different 19 license amendment and we will expect the staff to 20 review the criteria for applicability to the 21 particular application.

22 CHAIRMAN REMPE: Could I ask, tell me a 23 little more about what sites were considered? Did 24 they go through some sort of bounding site parameters 25 to come up with this time for mitigating that?

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16 1 MEMBER MARCH-LEUBA: There is no 2 description of the 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. Basically it is the 3 customary time we have been using forever.

4 MR. KAIZER: This is Josh Kaizer, NRC 5 staff. I was actually having discussions this morning 6 and I have a nice little document, but a lot of this 7 discussion started with a Maine Yankee backfit 8 contention. There was a SECY on it. The NUREG 9 followed it and there was another SECY after that.

10 So, I did want to provide that there is more detail 11 about the specific acceptance criterion and my 12 understanding is that 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> was kind of an estimate 13 of either getting a mitigation system into place or 14 doing evacuation and it's depending on whether you're 15 looking at like the SECY or the NUREG, depending on 16 which one they focused on.

17 MEMBER MARCH-LEUBA: Okay, so we'll ask 18 you again in about half an hour when it's your time.

19 CHAIRMAN REMPE: So while you're thinking 20 about what you're going to answer to us, you know, 21 sometimes people will use a bounding set of parameters 22 from the EPRI study of 95 percent of the plants or 23 something like that or did they just pick one plant, 24 like Maine Yankee, because that's what was under 25 discussion?

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17 1 MR. KAIZER: I am not sure and I can tell 2 you my answer will probably be a further explanation.

3 I'd say because of that uncertainty of where this 4 acceptance criterion came from, the staff tried to 5 make it very clear in SSE that they were focusing 6 solely on that acceptance criterion. We didn't say it 7 in the SE, we're not saying that this acceptance 8 criterion is acceptable for satisfying a particular 9 regulation or anything like that in the topical report 10 SE, we're just saying that if staff. I think this is 11 kind of what Jose was saying earlier with his LARS, if 12 an applicant comes in or licensee comes in and says, 13 hey I want to use this acceptance criterion, if the 14 staff finds this acceptance criterion acceptable, for 15 lack of a better term, for a specific licensing 16 request, then the Holtec method is an acceptable way 17 to demonstrate that the specific criterion has been 18 met.

19 CHAIRMAN REMPE: Again, I appreciate 20 whoever came up with these additional details, Member 21 March-Leuba, but, yes that's an interesting little 22 tidbit.

23 MEMBER MARCH-LEUBA: Yes and from my point 24 of view, I think the methodology and the intent from 25 Holtec is excellent. It is to be commended. What I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

18 1 want to get the concurrence from the members when we 2 discuss the letter is that we have a warning in the 3 body of the letter saying that the SCR only approves 4 the methodology. It does not approve the acceptance 5 criterion and it is application dependent. They will 6 have to review it. I would like to give an 7 opportunity now during the presentation for Holtec and 8 the staff to correct me if I'm wrong. My statement is 9 the SCR approves the methodology with an understanding 10 of the timing for the methodology. We are talking 11 about 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for heat up because it will change the 12 methodology if it was 10 seconds, but you do have an 13 understanding of what the application is likely going 14 to be, but you don't approve a particular criterion 15 today. That will be reviewed later. If I'm mistaken 16 in my statements, please you have time now to do it.

17 DR. ANTON: This is Stefan Anton, let me 18 first apologize for not characterizing that correctly.

19 I was focusing more on the development of the 20 methodology and I'm glad that my colleague, Andrea, 21 here could clarify that. She said yes, that that's 22 also our understanding. We are just developing the 23 methodology and the acceptance criteria could 24 potentially be site specific, if I may say it that 25 way. Is that correct?

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19 1 MS. STERDIS: Yes.

2 DR. ANTON: Yes, okay.

3 MR. KAIZER: And I will also confirm that 4 that was the intent of the staff safety evaluation.

5 Jose said it well and I would even go so far as to say 6 I think that that is what is written clearly in the 7 staff safety evaluation.

8 MEMBER MARCH-LEUBA: Excellent, thank you.

9 We are in violent agreement. Let's continue with the 10 presentation.

11 DR. ANTON: Yes, okay, very good. I'm 12 still on the previous slide. How do I know, what is 13 the principle approach to actually show that the 14 acceptance criteria is met. Since there is a 15 temperature involved and there is a time involved, 16 this, from a technical perspective, could be a 17 transient thermal analysis that needs to be performed 18 to see how the temperature would start rising after 19 the beginning of such an event. Then out of that 20 calculation, you would see under certain conditions if 21 the 900 degrees is met or not met within the 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.

22 Now the certain conditions would be the 23 heat, the decay heat of the fuel assemblies, that's 24 basically your variable that you have in there. So 25 you would determine what is the maximum decay heat of NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

20 1 the fuel assembly that would assure that the 900 2 degrees or whatever it is, let's stay with the 900 3 degrees in 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, is not reached.

4 Now the decay heat of the fuel assembly is 5 linked to the cooling time of the fuel assembly. Once 6 the fuel assembly comes out of the core and goes into 7 the spent fuel, the decay heat of the fuel assemblies 8 is very high and then it goes down over time. Once 9 you determine the decay heat limit, that you would 10 provide as a criteria, you then back calculate and 11 find out what is the minimum cooling time of the fuel 12 assembly. So the minimum time that has to pass after 13 the fuel is placed out of the core into the spent fuel 14 pool. That is the time that we talked about in the 15 previous slides where we see that this time with our 16 methodology we can show that a shorter time limit can 17 be applied there and show that even after a shorter 18 time, the zirc fire is no longer feasible.

19 Any comments on here before I continue?

20 MEMBER MARCH-LEUBA: Nothing from me.

21 DR. ANTON: Okay, thank you. Then let me 22 basically say we make an improvement compared to what 23 was done in the past and what was reviewed and 24 approved by the NRC for certain site specific 25 applications. There was a standard approach that has NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

21 1 been used. It is using a transient thermal 2 calculation with a number of conservative assumptions.

3 I listed the five principle and relevant assumptions 4 here.

5 Number one, the transient thermal analysis 6 was only done for a single fuel assembly out of the 7 pool. You use the bounding fuel assembly, the one 8 with the highest decay heat of all assemblies that are 9 in the spent fuel pool at a certain time. That is 10 number one and two. The other three basically say you 11 look at this fuel assembly in perfect thermal 12 isolation. You do not assume that the fuel assembly 13 can transfer any of the heat to the surrounding fuel 14 assemblies. You do not consider any air flow through 15 the rack at the assembly, so it's basically completely 16 isolated and you don't consider any other heat loss of 17 this single fuel assembly with the high heat flow.

18 Basically, all the decay heat that is in the assembly 19 is used to basically increase the heat load of that 20 assembly. That's then how you come up with the 21 temperature over time to see if 900 degrees is reached 22 or not reached within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.

23 This methodology, these assumptions, make 24 the calculations very simple. You can almost do it 25 with a simple analytical calculation approach on a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

22 1 piece of paper, just a few formulas or you can use a 2 simple spreadsheet. That has always been the 3 advantage of this. This is kind of the previously 4 used approach. So let's go to the next slide.

5 The difference in our approach, let me 6 just mention that the disadvantage of this previous 7 approach is that it doesn't give you any indication of 8 what would be a good or not so good configuration of 9 fuel assemblies in your spent fuel pool to actually 10 minimize the temperature at a given time of your 11 cladding. Your spent fuel pool has a mixture of high 12 and low decay heat assemblies so using this 13 methodology it doesn't really tell you what to do 14 there. That is one of the major disadvantages.

15 What we do, the principle difference of 16 our methodology is now that we consider limited heat 17 transfer between the assemblies. A hot assembly in 18 our methodology is allowed to exchange heat with 19 surrounding assemblies and they could be of a lower 20 heat load and so they could partially absorb some of 21 the heat from the hot assembly. With this 22 methodology, we can actually develop a thermally 23 optimized loading pattern throughout the spent fuel 24 pool, so we can basically say okay if you move fuel 25 assemblies in a certain way and put them in certain NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

23 1 locations, you can actually get in a better situation 2 with respect to the feasibility or the possibility of 3 a zirc fire.

4 At the same time, I was talking about the 5 conservative assumptions, we still keep the 6 conservative assumption that overall there is no heat 7 transfer from the assemblies to the outside. The fuel 8 assemblies, as a whole, are assumed not to exchange 9 any heat to the environment. Most importantly, we 10 keep still the assumption that there is no air flow 11 through the vents. This is quite a significant or 12 dramatic simplifying assumption because it basically 13 assumes that fuel assemblies that sit in the 14 individual rack cells and we basically assume that the 15 rack cell is basically closed both at the top and at 16 the bottom so that we have no air flow through there.

17 There could be situations where that would be the 18 case, if somebody is lying on top of the rack or if 19 there is still water at the bottom, but it is a very 20 extreme assumption in that respect. To say that 21 again, we are not changing that assumption.

22 MEMBER MARCH-LEUBA: This is Jose. I 23 agree with you that that feels like a very 24 conservative assumption. My question is different, 25 can you answer this in a non-proprietary setting; if NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

24 1 not, just tell me no, that's proprietary. Has Holtec 2 performed a scoping analysis for a particular spent 3 fuel pool and can you tell us how much benefit you get 4 from this analysis. I mean do you gain one month of 5 decay time or do you gain 10 years of decay time? If 6 you can do it in a non-proprietary setting.

7 DR. ANTON: Yes, let me just double that 8 here with my colleagues. I'll just for a second go on 9 mute if we can discuss this here. (Pause.)

10 MEMBER MARCH-LEUBA: This is only for our 11 benefit. This information is not necessary, so if you 12 have any problems whatsoever, please don't feel 13 obliged to do it.

14 DR. ANTON: (Pause.) Yes, I can actually 15 confirm that, I discussed that here. We have 16 performed some informal calculations just to see what 17 the effect would be. They indicate to us that if 18 there would be air flow allowed through the fuel 19 assembly, even after an infinite amount of time, it 20 would not reach the 900 degrees Celsius, so this is 21 quite a dramatic assumption. If we find out the 22 criteria that meets the 900 degrees after 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 23 at the same time if you would let the air flow in 24 there, you could leave it there indefinitely and you 25 would not reach the 900 degrees Celsius.

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25 1 MEMBER MARCH-LEUBA: Thank you for that, 2 but just for the record, I'm suggesting you supplement 3 to this topical report, you are not getting air flow 4 allowed in your calculation. Your current topical 5 report says no air flow.

6 DR. ANTON: That is correct.

7 MEMBER MARCH-LEUBA: Yes. You may want to 8 submit a supplement, but it would a different review.

9 Thank you. Continue.

10 DR. ANTON: Yes.

11 MEMBER BALLINGER: This is Ron Ballinger.

12 The way I read it, what your analysis does is simply 13 change the slope of the heat up rate. This changes 14 the slope. It extends the time, but the relaxation of 15 the air flow thing is so dramatic, I still wonder 16 whether that makes any difference at all because 17 everybody has to assume basically no air flow, then 18 changing the slope looks good from a stylized point 19 of view, but the conservatism is so large that it's 20 just a stylized calculation.

21 MEMBER MARCH-LEUBA: The concern with 22 allowing air flow is they will have to demonstrate 23 that when you're blowing on a fire, you don't increase 24 it, that's the concern. I don't think it is a real 25 concern because you never reach the ignition point, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

26 1 but that's probably why they didn't.

2 DR. ANTON: Yes.

3 MEMBER MARCH-LEUBA: I cannot wait until 4 the supplement to review it. Keep going.

5 DR. ANTON: Okay, yes, good. That's why, 6 if we would try to take credit for that, and we have 7 discussed that, it would get significantly more 8 complicated. That's why we stayed with the current 9 approach that we actually would not take any credit 10 for that because we were aware of the complication 11 that this would create.

12 That gets me on my slide to the last 13 bullet there because we did not want to have a 14 complicated calculation in this. We wanted to have 15 this approach, this methodology to more or less 16 straightforward and not to be too complicated. And we 17 wanted to be still consistent in our assumption with 18 the previously approved methods. That already then 19 gets me to the summary. We submitted the topical 20 report that improves on the method to determine if a 21 zirc fire is possible or not in a spent fuel pool and 22 that allows us to come up with certain criteria. But 23 at the same time, we still focus here on the 24 significant conservatism of the air flow not being 25 there, which was done to keep it simple, but also to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

27 1 keep it consistent with the previous analysis and make 2 it actually easier for the implementation and also for 3 the approval.

4 That gets me to the end of our 5 presentation. Any other questions here or discussions 6 that we need?

7 MEMBER MARCH-LEUBA: Members, anybody want 8 to add something? Okay so in the interest of time, I 9 want to thank you, Stefan and Holtec, for a very 10 organized and well presented topic, which I know is of 11 value to the nuclear industry.

12 DR. ANTON: Thank you very much.

13 MEMBER MARCH-LEUBA: Thank you very much.

14 Josh, we'll give you 20 minutes now.

15 MR. KAIZER: Okay. Thank you very much.

16 My name is Joshua Kaizer. I, along with Adam Rau, 17 were the reviewers for this topical report. Next 18 slide, please, Kate.

19 So they've already talked about the drain 20 down methodology and we've already spent a while to 21 talk about the acceptance criterion. There are two 22 other points about that I wanted to bring up.

23 The first was this 900 degrees C for at 24 least 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> is a bit fuzzy. Jose alluded to it.

25 If you go back and you read NUREG-1738, it actually NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

28 1 lists a number of temperatures. It can be 900 and all 2 air, it could be 1,200 in steam. The question is 3 which environment is it. It's probably going to be a 4 mixture of air and steam. How much, we don't know.

5 So most people and I think pretty much everyone says 6 the conservative thing of, okay, we'll just go with 7 the lower temperature.

8 There is, even in the acceptance criterion 9 itself, there is some built in conservatism and you're 10 saying, okay 900 not any more than that, for following 11 the spent fuel pool drain down.

12 The other thing I wanted to kind of get up 13 and talk about, because I know Dr. Rempe kind of 14 mentioned it, was the acceptance criterion itself, 15 where it actually comes from. I'm currently viewing 16 this as kind of an acceptance criterion that the 17 applicant proposes to the NRC and then the NRC 18 accepts. We do have a number of acceptance criterion 19 that are, I'd say, enshrined in our guidance documents 20 and SRPs, but a lot of those acceptance criterion that 21 are even in SRPs were initially proposed by applicants 22 to satisfy a regulation.

23 One of my favorites because I deal with 24 CHF a lot, is this 99.9 percent of fuel rods in the 25 core will not experience a boiling transition. That NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

29 1 number was not a number the NRC generated. That 2 number came from an old publically available GE 3 document and they said, hey NRC, we think this 4 acceptance criterion is good to satisfy this 5 regulation. So I wanted to highlight that to say that 6 when an applicant gives us something, it is not out of 7 scope for them to say we think this acceptance 8 criterion can be used to satisfy this regulation and 9 the NRC agrees to that. So I want to provide that 10 background.

11 We know the acceptance criterion and the 12 methodology goal here was Holtec's method should be 13 able to perform the analysis of the spent fuel pool 14 after drain down and demonstrate that, or predict a 15 peak clad temperature, and demonstrate that hey, for 16 at least 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, that temperature doesn't go above 17 900 degrees C. Next slide, please, Kate.

18 All right, so our review goal was 19 basically determine is Holtec's method credible.

20 Credible is a new term really old concept. It's just 21 can we trust their computational model. Credibility, 22 I think, I like the word because it's nice to have a 23 specific word that means can we trust this 24 computational model for its intended purpose. I think 25 it comes from one of the first uses was like a NASA NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

30 1 paper from 2000s. There I give a picture of a recent 2 ASME standard that started to talk about credibility.

3 While the NRC has been focused on this area, I'd say 4 even before it's inception in 1975, we call it 5 credibility now. So we're really looking at is 6 Holtec's method credible, i.e., can we trust it to 7 predict the peak clad temperature following a spent 8 fuel pool drain down, in order to demonstrate that 9 that temperature remains below the 900 degrees.

10 The review challenge in this area, there 11 was very limited validation data. Normally when we 12 look at a model's credibility for a computational 13 model, you are going to base that credibility decision 14 on verification and validation. Certainly 15 quantification activities, I think, we tend to much 16 great weight the validation, the experimental data you 17 have to prove that your model is predicting reality 18 and, in this case, there is limited data, but honestly 19 in many cases there is limited data. So when you do 20 have that limited data, you default to demonstrating 21 that the methods are conservative. There are a lot of 22 conservatisms in this method. This is not out of 23 scope. I would even argue that if you go back and you 24 read Appendix K, that's what Appendix K was doing.

25 When you don't know how physics behaves, you try to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

31 1 figure out okay, well I don't know the exact behavior 2 of this, but can I come up with a number that bounds 3 what we believe the uncertainties are to be. That was 4 the challenge. Next slide, please.

5 MEMBER MARCH-LEUBA: Josh, no, stay on the 6 slide three for a moment.

7 MR. KAIZER: Yes, sure.

8 MEMBER MARCH-LEUBA: First you have 9 Appendix K's similarity is a very good example. I 10 appreciate you wrote it to the record. I wanted to 11 ask you another question. You wrote a NUREG KM0013, 12 which we reviewed, but you are now referencing the 13 ASME standard, I have not been able to find the final 14 version of KM0013. Is it still in that form?

15 MR. KAIZER: It is. That is my fault. I 16 actually owe someone to review it. I have, I think, 17 two more things to finish off and not much has 18 changed. It is basically just getting that final 19 thing out, but because --

20 MEMBER MARCH-LEUBA: Okay.

21 MR. KAIZER: Of some other work, it keeps 22 getting piled up.

23 MEMBER MARCH-LEUBA: I hate to have a 24 reference in our letter to our draft report, but it's 25 basically final draft, right?

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32 1 MR. KAIZER: Yes, it is. I really 2 apologize and I appreciate, I won't say yelling at me, 3 but I'll call it yelling at me because this way I can 4 justify to my bosses, hey, I really need to get this 5 done. ACRS is yelling at me for it. So that is 6 helpful to me. (Laughter.)

7 MEMBER MARCH-LEUBA: You can count on our 8 yelling.

9 MR. KAIZER: Thank you.

10 MEMBER MARCH-LEUBA: Keep going.

11 MR. KAIZER: All right, next slide, 12 please. So the safety evaluation mirrors SRP 1502, 13 now SRP 1502 is the staff's guidance on how to review, 14 it's basically transient accident analysis methods.

15 I would argue it's really any computational model. If 16 you're doing modeling for aircraft seat design or 17 small medical devices, whatever, you would follow 18 pretty much the same criteria.

19 Based on, I'd say, it kind of started with 20 a CSAU, which was a document from the 1980s and then 21 developed further in through MDAP, which was from the 22 late '90s, but it is basically if you're going to 23 trust a simulation, you would need to kind of fill out 24 all these steps. The only difference between the SE 25 and what's in the SRP is we've just kind of rearranged NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

33 1 things a little. Same criteria are all there, but we 2 just rearranged them in what we think is a more 3 logical process.

4 The other thing I wanted to stress on the 5 safety evaluation was Appendix A, which was the 6 staff's confirmatory analysis. A lot of times there's 7 confusion on what role a confirmatory analysis plays.

8 The NRC staff can't base its regulatory conclusion on 9 the confirmatory analysis because that analysis is not 10 done under Appendix B program. A lot of times it's 11 done by the staff. The staff makes their own 12 decisions, but that analysis is there to confirm the 13 staff's regulatory conclusion. I think the analysis 14 for our case was extremely helpful. It made things 15 a lot clearer and it did play a very important role, 16 but I did want to stress that we didn't base any of 17 our safety conclusions on the analysis, but we did use 18 that analysis to confirm those conclusions.

19 MEMBER MARCH-LEUBA: You know, I brought 20 this -- this is Jose again, I brought this up in 21 previous meetings that code to code benchmarks are to 22 be relied upon for confirmation, but not exclusively.

23 Here we are almost crossing the boundary, but I 24 believe your approval of this methodology is based 25 more on physical conservatisms.

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34 1 MR. KAIZER: Yes.

2 MEMBER MARCH-LEUBA: And not exclusively 3 on your code to code comparisons, right?

4 MR. KAIZER: I agree with that. I have 5 seen it written in papers. I feel very proud that I 6 actually have written in the paper not only why code 7 to code is not good, but give like a specific equation 8 that shows you the error of why it's not good. I do 9 agree with that. I think that it is important to note 10 that confirmatory analysis can confirm what the staff 11 is saying, but if the staff reaches a regulatory 12 conclusion, it has to be for other reasons. I mean I 13 would even argue saying that code to code comparisons 14 by the applicant, the level that you can trust those 15 comparisons is not nearly the same as if you can trust 16 validation data and also I think not nearly the same 17 as if you can trust a good conservative judgment on 18 something.

19 MEMBER MARCH-LEUBA: Thank you. As I said 20 before, I think we are in violent agreement.

21 MR. KAIZER: Yes.

22 MEMBER MARCH-LEUBA: I just want to keep 23 bringing it into the record that are many new reactors 24 with esoteric fuels that are coming into review that 25 are going to have very little data available. We need NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

35 1 to keep the code to code comparisons in mind for other 2 applications. This one doesn't have any problem in 3 this regard. Thank you.

4 MR. KAIZER: Understood. All right, next 5 slide, please. All right, this is my last slide. The 6 staff believes that the conservatisms of the method 7 more than outweigh the uncertainties. If I've said 8 that in the, I'd say a more formal speak, the NRC 9 staff believes, this is the second bullet, the NRC 10 staff believes that there is reasonable assurance that 11 the method will conservatively or accurately predict 12 peak cladding temperature following spent fuel pool 13 drain down. I did want to provide a little bit more 14 detail about what do I mean by reasonable assurance 15 because that is something that we get the language 16 from the regulation but it is not necessarily clearly 17 and explicitly defined.

18 In this sense, when I say we have 19 reasonable assurance that this method will 20 conservatively or accurately predict the peak clad 21 temperature, what I mean is there is always a balance 22 between uncertainties in the method, things you don't 23 know, things that have a variance and the 24 conservatisms of the method and you need those 25 conservatisms to kind of outweigh those uncertainties.

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36 1 The balance between the two here is very similar to 2 the balance in other models and simulations, where the 3 staff has also decided yes, we can trust this 4 simulation for safety analysis purposes.

5 That is the open summary of the review.

6 Any other questions or comments?

7 MEMBER MARCH-LEUBA: Members, this is the 8 conclusion of the presentations. We will not have a 9 closed session, because we do not have time. Any 10 comments?

11 MEMBER BROWN: Can I ask a question?

12 MEMBER MARCH-LEUBA: Yes. Speak into the 13 microphone.

14 MEMBER BROWN: My command voice is not 15 enough? This is, when I looked at this, I tried to 16 get a handle on why they feel it's credible, but why 17 isn't it, is my opinion and I listened, even though I 18 missed a bit of the first part, I did go through it.

19 What's the complicating thing that's different, other 20 than the single assembly being analyzed from a physics 21 and heat transfer standpoint that makes, I guess, 22 people not saying hey, this is okay? I mean this is 23 convected heat flow, boundary conditions. You've got 24 to know what your temperature is in the spent fuel 25 pool, you know, the elements themselves, you know, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

37 1 what their decay level is, I guess, to find out how 2 much heat. What is the piece that makes the 3 difference from what we did before and now we have to 4 question why the model -- the new way of being able to 5 do a bunch of assemblies and arrange them as opposed 6 to basing it on one assembly? (Simultaneous 7 speaking.) I didn't get that out of the report.

8 MEMBER MARCH-LEUBA: Yes, I am afraid that 9 that might be a proprietary answer.

10 MEMBER BROWN: Oh.

11 MEMBER MARCH-LEUBA: I can fill you in off 12 the microphone if you want, but unless, Stefan, can 13 you give him a short answer in non-proprietary?

14 MEMBER BROWN: I was thinking when I look 15 at it, you've got assemblies, you've got them stacked 16 in various arrangements. You've got to do heat 17 transfer, convective heat flow with air moving up or 18 not moving up --

19 MEMBER MARCH-LEUBA: If you look at --

20 MEMBER BROWN: To make assumptions.

21 MEMBER MARCH-LEUBA: If you read the 22 transcript for the subcommittee, I personally said 23 that Holtec is not going to get the Nobel Prize for 24 this methodology. (Simultaneous speaking.)

25 MEMBER BROWN: Thank you.

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38 1 MEMBER MARCH-LEUBA: It's very simple and 2 adequate.

3 MEMBER BROWN: Okay, (Simultaneous 4 speaking.) that's fine then, we don't need to go.

5 (Simultaneous speaking.) I just did not see where this 6 was some great leap forward or anything like that, 7 it's basically stuff I learned in college.

8 MEMBER MARCH-LEUBA: Yes, but that's why 9 I asked earlier from Holtec how many months or years 10 they earn by using this methodology.

11 MEMBER BROWN: No, that was a good 12 question.

13 MEMBER MARCH-LEUBA: I wouldn't be 14 surprised if they earn a lot, three or four years.

15 MEMBER BROWN: Well I would think so also 16 based on the thought process. The whole approach 17 seemed to make more sense than what we did before.

18 All right, I'll stop right there. No need to mouse 19 milk this.

20 MEMBER SUNSERI: Charlie, you with 21 Joshua's picture up there, I mean the biggest 22 uncertainty is what is the heat level of the assembly?

23 (Simultaneous speaking.) And that is --

24 MEMBER BROWN: That's what I figured.

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39 1 in the model, but that's the biggest thing really in 2 going ahead and using this for optimizing a spent fuel 3 pool (Simultaneous speaking.)

4 MEMBER BROWN: Isn't there a way to 5 measure some temperatures to get some idea of what the 6 element --

7 MEMBER MARCH-LEUBA: Fortunately, we don't 8 drain spent fuel pools very often.

9 MEMBER BROWN: No, I understand that.

10 MEMBER MARCH-LEUBA: That's the problem 11 with why they don't have experimental data 12 (Simultaneous speaking.)

13 MEMBER BROWN: We understand the physics 14 of decay heat, I mean we've been calculating decay 15 heat for these plants for 70 years.

16 MEMBER MARCH-LEUBA: And one big advantage 17 is that we are not designing a spent fuel pool for 18 future loading. We already have all the fuel that 19 came out of the core. This is decommissioning. We 20 know what's in there.

21 MEMBER BROWN: Yes.

22 MEMBER MARCH-LEUBA: And they have been 23 doing the burn up in the core as it was burning so 24 they know the decay heat of each bundle (Simultaneous 25 speaking.) pretty accurately.

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40 1 MEMBER BROWN: I'm just trying to make 2 sure I didn't miss something. I was totally 3 comfortable with reading the whole thing, so it seemed 4 to make a lot of sense to me based on, and recognizing 5 I had heat transfer in college, had at NR whether I 6 liked it or not, I had to deal with it all the time, 7 so this seemed to be fairly straightforward. It's a 8 matter of what is the complicating factor. I think 9 you've answered the question for me. All right, thank 10 you.

11 MEMBER BALLINGER: This is Ron Ballinger.

12 I don't remember whether this is true or not, but does 13 the analysis, is it truly adiabatic at least the 14 conservative one or does it allow for the positive 15 feedback from the zirc water reaction?

16 MR. JONES: Yes, this is Steve Jones. I'm 17 acting chief of the containment and plant systems 18 branch. I just wanted to go back a little bit in 19 history. NUREG-1738 did look at both an air cooled 20 scenario where there's early oxidation of a fuel 21 beginning say at 565 degrees Celsius and compared that 22 with an adiabatic heat up scenario where all the heat 23 is confined to the fuel assembly itself. Then looking 24 at 900 degrees where the reaction rate, the oxidation 25 rate, greatly accelerates beyond 900 degrees in air.

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41 1 The staff determined that considering all the possible 2 scenarios and configurations that could occur 3 following, you know, extreme seismic events or other 4 events that would really challenge the structure of a 5 spent fuel pool, it was best to consider an adiabatic 6 scenario in terms of evaluating when it was okay to 7 reduce the scope of emergency planning responses.

8 MEMBER BALLINGER: Yes, that's a different 9 question.

10 MR. JONES: Okay.

11 MEMBER BALLINGER: I mean the 1738 does 12 consider the feedback from the zirc water reaction, 13 but what I'm asking is does this methodology consider 14 -- I don't think it does. I think it just --

15 MR. JONES: No (Simultaneous speaking.)

16 It's not intended (Simultaneous speaking.) to because, 17 I guess, the acceptance criteria that we've been 18 working on for the last several years is the Office of 19 Nuclear Security and Incident Response has an interim 20 staff guidance document, DPR ISG 02. I have the ML 21 number, you know, the ADAMS accession number if 22 anybody is interested, but we've been using this for 23 several decommissioning plants over the last several 24 years, since 2000 --

25 MEMBER MARCH-LEUBA: Steve, please read NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

42 1 the ML number on the transcript.

2 MR. JONES: Sure.

3 MEMBER MARCH-LEUBA: So we can follow 4 this.

5 MR. JONES: The ADAMS accession number is 6 ML14106A057.

7 MEMBER MARCH-LEUBA: Thank you. That way 8 if somebody needs to follow up, we wrote it down, too.

9 Thank you.

10 MR. JONES: Okay and that does discuss the 11 basis, how we've gone through initial proposed rule 12 making attempts in the early 2000s and just recently 13 a new rule making package was developed and presented 14 to the commission. We've maintained that 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, 15 900 degrees adiabatic heat up time was an appropriate 16 criterion to use to evaluate a transition away from a 17 coordinated emergency response between the plant and 18 civil authorities outside the plant boundary to going 19 to more of a reliance on all hazards emergency plan.

20 In addition, we're also considering the 21 abilities to mitigate that have resulted from the post 22 9/11 and the Fukushima actions to provide strategies 23 to mitigate different scenarios that might occur in 24 the spent fuel pool and apply those to prevent 25 cladding damage or in the worst case, mitigate the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

43 1 release.

2 MEMBER MARCH-LEUBA: Steve, since you 3 brought this up, do decommissioned plants have FLEX 4 equipment? Or does it not apply to them?

5 MR. JONES: Yes. During decommissioning, 6 there's a license condition that requires them to 7 maintain some FLEX type capability with respect to the 8 spent fuel pool and (Simultaneous speaking.) we retain 9 that.

10 MEMBER MARCH-LEUBA: Thank you. That's 11 reassuring, thank you very much. (Pause.)

12 MEMBER SUNSERI: My question is not that, 13 it was more procedural. Here we say we're not going 14 to go into closed session because we don't have time.

15 I would suggest that we should check with the members 16 to see if anybody has anything. Charlie had a 17 question that was borderline already and we didn't, so 18 I would ask that question before we decide not to go 19 into closed session.

20 MEMBER MARCH-LEUBA: Anybody want to ask 21 a proprietary question? (Pause.) Thank you. So are 22 you going to ask for public comments or should I?

23 CHAIRMAN REMPE: It's up to you, but one 24 of us should.

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44 1 members of the public that want to make a comment?

2 Remember these are comments, not questions, please do 3 so now and if you are calling us on a cell phone, use 4 star six to unmute yourself. (Pause.) That was five 5 seconds. We are done with the subcommittee meeting.

6 Ms. Chairman?

7 CHAIRMAN REMPE: Thank you. So you have 8 said you have a draft letter you're ready to read in.

9 Tammy, are you out there?

10 MS. SKOV: I'm here.

11 CHAIRMAN REMPE: Great. If you'll bring 12 it up. Why don't we take, let's see, I'm having 13 trouble seeing the very small numbers, it's 9:35, 14 right?

15 MEMBER MARCH-LEUBA: Yes.

16 CHAIRMAN REMPE: Yes, but it's not the 17 same. It says 9:37. (Laughter.) I've learned that 18 part. But anyway, let's take about a 15-minute break 19 and come back at 9:50 East Coast time folks, and we'll 20 read in the draft letter. Okay?

21 MEMBER MARCH-LEUBA: Okay.

22 (Whereupon, the above-entitled matter went 23 off the record at 9:37 a.m.)

24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

U. S. Nuclear Regulatory Commission Review of Holtec International Topical Report HI-2200750, Revision 0, Holtec Spent Fuel Pool Heat Up Calculation Methodology Holtecs Method for Determining Fuel Assembly Heat Up During a Theoretical Drain Down Event Joshua Kaizer, PhD Adam Rau, PhD Division of Safety Systems Office of Nuclear Reactor Regulation February 3, 2022

Drain Down Methodology Goal Acceptance Criterion Ensuring that the spent fuel temperature remains below 900 °C for at least 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> following a complete drain down of the spent fuel pool.

Methodology Goal Demonstrate that the configuration of the fuel in the spent fuel pool satisfies the acceptance criterion.

2

Review Goal Review Goal Is Holtecs methodology credible?

(i.e., is there reasonable assurance that the methodology can be used to demonstrate that the acceptance criterion has been satisfied?)

Review Challenge Validation data is very limited.

Demonstrably Conservative Methods 3

Safety Evaluation Outline SRP 15.0.2

1. Scenario Identification Process

2. Documentation

3. Evaluation Model Assessment 3.1 Model Applicability 3.2 Model Verification 3.3 Model Validation 3.4 Data Applicability 3.5 Uncertainty Quantification 3.6 Quality Assurance

4. Conclusion A. The NRC staffs Confirmatory Analysis 4

Conclusions:

Conservatisms The NRC staff believes that the conservatisms of the method, as well as the analysis performed, more than outweigh the uncertainties.

The NRC staff believes that there is reasonable assurance that this method will conservativity or accurately predict peak cladding temperature following spent fuel pool drain down. Uncertainties Conservatisms Reasonable assurance = the balance between uncertainties and conservatisms in this instances is similar to other instances where the staff has also trusted the simulation 5

www.holtec.com Topical Report: Method for Determining Spent Fuel Assembly Heat Up During a Theoretical Drain Down Event of a Spent Fuel Pool Holtec Presentation to ACRS Full Committee OPEN Session February 3, 2022

Purpose of the Topical Report Provide a methodology to proactively determine the best overall spent fuel pool arrangement to eliminate the risk of a zirc fire as soon as possible after permanent defueling.

The methodology developed by Holtec can be used to gain a significant and real safety benefit that can be recognized.

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Problem Description During a theoretical beyond design basis drain down event of a spent fuel pool, the cladding of the fuel assemblies would heat up due to the loss of water cooling in the pool.

If the cladding temperature exceeds a certain value, there is the possibility of an exothermal reaction with the air, possibly resulting in what is commonly called a zirconium fire or zirc fire.

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Acceptance Criteria and Principal Approach The criteria to evaluate if such a condition may occur, used in previous applications and reviewed and approved by NRC, is that a cladding temperature of 900 °C is not exceeded within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> from the drain-down event.

The principal approach to determine if the condition could occur or not is to perform a transient thermal analysis, and determine the parameters (e.g. cooling time of the fuel assemblies) that needs to be satisfied for the temperature to not exceed the limit within that time.

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Previously used Methodology The methodology previously used, and reviewed and approved by NRC, is a transient thermal calculation using the following main conservative assumptions

1. A single assembly is analyzed

2. Highest decay heat of all assemblies in the spent fuel pool is applied to that assembly

3. No lateral heat loss to surrounding assemblies

4. No air flow through the rack and assembly

5. No other axial heat loss through the top and bottom of the spent fuel rack Implementation is fairly simple Can be done with a simple analytical calculational approach, or a simple spreadsheet.

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Methodology proposed in Holtec Topical Report (TR)

Principal difference between the Holtec TR and the previously approved methodology is that the Holtec TR methodology considers limited heat transfer between assemblies This informs the development of thermally optimized loading patterns throughout a spent fuel pool The methodology keeps the conservative assumption that there is no heat transfer from the assemblies to the outside environment No significant increase in the complexity of calculations www.holtec.com l Page 6

Summary A topical report has been submitted that improves on the method to determine if a zirc fire is possible in a spent fuel pool after the assumed drain-down of the water in the pool.

The method still employs significant conservatisms. Specifically, it still assumes there is no air flow through the rack cell and assemblies after the drain down event.

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