ML23053A245

Transcript of the Advisory Committee on Reactor Safeguards 702nd Full Committee Meeting, February 1, 2023, Pages 1-85 (Open)

ML23053A245
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NRC-2246
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Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION

Title:

Advisory Committee on Reactor Safeguards Docket Number:

(n/a)

Location:

teleconference Date:

Wednesday, February 1, 2023 Work Order No.:

NRC-2246 Pages 1-59 NEAL R. GROSS AND CO., INC.

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

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

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1 2

3 DISCLAIMER 4

5 6

UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7

ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8

9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.

15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.

19 20 21 22 23

1 UNITED STATES OF AMERICA 1

NUCLEAR REGULATORY COMMISSION 2

+ + + + +

3 702ND MEETING 4

ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5

(ACRS) 6

+ + + + +

7 WEDNESDAY 8

FEBRUARY 1, 2023 9

+ + + + +

10 The Advisory Committee met via 11 teleconference at 8:30 a.m., Joy L. Rempe, Chairman, 12 presiding.

13 14 COMMITTEE MEMBERS:

15 JOY L. REMPE, Chairman 16 WALTER L. KIRCHNER, Vice Chairman 17 DAVID A. PETTI, Member-at-Large 18 RONALD G. BALLINGER, Member 19 VICKI M. BIER, Member 20 CHARLES H. BROWN, JR., Member 21 VESNA B. DIMITRIJEVIC, Member 22 GREGORY H. HALNON, Member 23 JOSE A. MARCH-LEUBA, Member 24 MATTHEW W. SUNSERI, Member 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

2 ACRS CONSULTANT:

1 DENNIS BLEY 2

3 DESIGNATED FEDERAL OFFICIAL:

4 WEIDONG WANG 5

6 7

8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

3 CONTENTS 1

Page 2

Call to Order..................

4 3

ACRS Chairman Opening Statement.........

4 4

ACRS Chairman Agenda 6

5 NRC Staff Introductory Remarks 6

Bill Jessup, NRR 7

7 Kairos Topical Report on Graphite Materials 8

Margaret Ellenson.............

9 9

Staff Comments 10 Alex Chereskin

.............. 26 11 Public Comments (None)

............. 37 12 Kairos Topical Report on Metallic Materials 13 John Price

................ 38 14 Dr. George Young

............. 42 15 Staff Comments 16 John Honcharik

.............. 48 17 Public Comment (None).............. 59 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

4 P-R-O-C-E-E-D-I-N-G-S 1

8:30 a.m.

2 MEMBER REMPE: Good morning. It's 8:30 on 3

the East Coast, and this meeting will now come to 4

order. This is the first day of the 702nd meeting of 5

the Advisory Committee on Reactor Safeguards. I'm Joy 6

Rempe, Chairman of the ACRS.

7 Other members in attendance are Ron 8

Ballinger, Vicki Bier, Charles Brown will be here 9

soon, there were some delays on the road, Vesna 10 Dimitrijevic, Greg Halnon, Walt Kirchner, Jose March-11 Leuba, Dave Petti and Matt Sunseri. So we do have a 12 quorum today.

13 Today the Committee is meeting in-person 14 and virtually.

15 The ACRS was established by the Atomic 16 Energy Act and is governed by the Federal Advisory 17 Committee Act. The ACRS Section at the U.S. NRC 18 public website provides information about the history 19 of this Committee and documents such as our charter, 20 bylaws, Federal Register notices for meetings, letter 21 reports and transcripts of all full and subcommittee 22 meetings, including all slides presented at the 23 meetings.

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

5 safety matters to the Commission through its publicly 1

available letter reports.

2 The Federal Register notice announcing 3

this meeting was published on December 27, 2022, and 4

this announcement provided a meeting agenda as well as 5

instructions for interested parties to submit written 6

comments or written documents or request opportunities 7

to address the Committee.

8 The Designated Federal Officer at today's 9

meeting is Mr. Weidong Wang.

10 The communications channel has been opened 11 to allow members of the public to monitor the open 12 portions of the meeting. The ACRS invites members of 13 the public to use the MS Teams link to view slides and 14 other discussion materials during these open sessions.

15 This link information was placed in the Federal 16 Register notice and the agenda on the ACRS public 17 website.

18 We've received no written comments or 19 requests to make oral statements from members of the 20 public regarding today's session. Periodically, the 21 meeting will be open to accept comments from 22 participants listening to our meetings.

23 Written comments may be forwarded to Mr.

24 Weidong Wang, today's Federal Officer.

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

6 During today's meeting, the Committee will 1

consider the following two topics, the Kairos Topical 2

Report on Graphite Materials and the Kairos Topical 3

Report on Metallic Materials.

4 Note that portions of these Kairos topic 5

discussions may be closed as stated in the agenda. A 6

transcript of the open portions of the meeting is 7

being kept, and it is requested that speakers identify 8

themselves and speak with sufficient clarity and 9

volume so they can be readily heard. Additionally, 10 participants should mute themselves when not speaking.

11 Before we begin today's meeting, I do have 12 one announcement I would like to make. On December 9, 13 2022, it was publicly announced that President Biden 14 appointed Member Ballinger to the Nuclear Waste 15 Technical Review Board. So please join me in 16 congratulating Member Ballinger for this appointment.

17 And so at this time, I would like to ask 18 other members if they have any opening remarks.

19 Seeing no one, I would like to ask Dave Petti to lead 20 us in our first topic in today's meeting. Dave?

21 MEMBER PETTI: Okay. We're going to talk 22 about the draft safety evaluation of graphite material 23 qualification for Kairos fluoride high temperature 24 reactor. To start is Bill Jessup on the line to give 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

7 opening comments?

1 MR. JESSUP: Yes, sir. And thank you, 2

Member Petti and thank you, Chairman Rempe, for the 3

opportunity to present to the Committee today.

4 I am Bill Jessup, Chief of Advanced 5

Reactor Licensing Branch 1 here in the Division of 6

Advanced Reactors in Non-Power Production and 7

Utilization Facilities, or DANU, in the Office of 8

Nuclear Reactor Regulation, or NRR.

9 Today the staff will be providing brief 10 presentations on our reviews and the safety 11 evaluations for two Topical Reports from Kairos Power.

12 The first Topical Report on the 13 qualification of graphite materials to be discussed 14 this morning describes the testing required to qualify 15 the structural graphite materials used in the safety 16 related components of Kairos Power's fluoride-cooled 17 high-temperature reactor or KP-FHR designs.

18 The second Topical Report on the 19 qualification of metallic materials to be discussed 20 this afternoon focuses on the testing and modeling 21 required to qualify the structural alloys that will be 22 used in the safety-related portion of the KP-FHR 23 designs.

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

8 ACRS Kairos Subcommittee on January 12, 2023. And 1

today's presentations are going to highlight key areas 2

from the staff's reviews and relevant limitations and 3

conditions associated with the future use of each 4

Topical Report.

5 As mentioned during last month's 6

subcommittee meeting, the staff is currently reviewing 7

the construction permit application from Kairos for 8

its non-powered Hermes test reactor that would use the 9

KP-FHR technology.

10 And the two Topical Reports that we're 11 going to be discussing today would apply to both the 12 non-power and power reactors that are currently under 13 development by Kairos. Therefore, the reviews of the 14 Topical Reports we are going to talk about today will 15 need to be finished before we can complete the 16 construction permit application review.

17 We're looking forward to today's 18 discussions. Always appreciative of the Committee's 19 insights and comments on these topics. And with that, 20 I'll turn it back over to you, Member Petti and 21 Chairman Rempe.

22 MEMBER PETTI: Okay. Thank you, Bill.

23 With that, Kairos? Margaret, are you ready to get 24 your slides up?

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9 MS. ELLENSON: Yes, I am. Can you hear me 1

all right?

2 MEMBER PETTI: Perfectly. Thank you.

3 MS. ELLENSON: Okay. Great. Thanks. I 4

increased the noise reduction so hopefully that will 5

help a little bit.

6 Hi. I'm Margaret Ellenson. I'm with 7

Kairos Power. And I'm the lead for this graphite 8

material qualification for KP-FHR Topical Report.

9 We presented to the subcommittee back in 10 January, and we're excited to be able to speak to the 11 full Committee today. Thank you for your time.

12 Kairos is a mission centered organization.

13 And our mission is to enable the world to transition 14 to clean energy with the ultimate goal of dramatically 15 improving people's quality of life while protecting 16 the environment. Along the path, there will be many 17 steps to bringing this clean technology to the market 18 and qualifying graphite is one of those steps.

19 This is a general background on the 20 Graphite Topical Report. Our purpose in submitting 21 this report to the NRC is to present the methods for 22 qualifying structural graphite for the use in a KP-23 FHR. And by structural graphite, we really mean the 24 reflector structure in the core, not the pebbles.

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

10 The secondary purpose there is to align 1

with the NRC staff on the methods for qualifying 2

structural graphite. Because this is -- while 3

graphite is not a new material in the nuclear space, 4

it is relatively new in the licensing space. So we 5

were interested in aligning early on what the methods 6

can be to close data gaps.

7 The scope of the report is applicable to 8

both a test in a power reactor as was previously 9

mentioned. The graphite that we're going to be 10 qualifying is ET-10, which is a super fine grain 11 graphite with nearly isotropic properties.

12 The reflector structure serves two 13 different safety functions. It provides that physical 14 pathway for maintaining core cooling, and it provides 15 a physical pathway for reactivity control insertions.

16 However, the reflector serves that safety function 17 simply by maintaining its integrity. It's a pretty 18 simple safety function there.

19 And I wanted to take a moment to take note 20 of our quality assurance program. So the ASME Section 21 III, Division 5, code, which we will talk more about 22 in a minute, states specifically to use an NQA-1 based 23 quality assurance program.

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

11 expect to fully meet the code. So any information 1

that we rely on for a power reactor application would 2

be under an NQA-1 based program.

3 However, the NRC does not require an NQA-1 4

based program for test reactors. So for a test 5

reactor application, you're going to take a deviation 6

from the code by using instead the more commonly used 7

code for QA for a non-power reactor, which is the 8

ANSI-15.8-1995.

9Property "ANSI code" (as page type) with input value "ANSI-15.8-1995.</br></br>9" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process. So I wanted to make sure that point was 10 clear before we move on. And I'll pause here in case 11 there are any questions.

12 MEMBER PETTI: So let me just be clear.

13 Then any data developed for the test reactor will be 14 not used for the power reactor. There will be two 15 separate data sets because they are under two 16 different quality programs.

17 MS. ELLENSON: So there are methods -- so 18 the data is the data, right? The NQA program -- or 19 sorry, the quality assurance programs are different 20 methods for being able to evaluate how that data was 21 generated.

22 So we could use the same data for both.

23 I actually don't think we will be. I think actually 24 all of the data that we will be generating will be 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

12 either for the test reactor or the power reactor. But 1

just to be clear about, you know, what is involved in 2

an NQA or an ANSI 15.8, the differences are 3

procedural, not necessarily in testing protocol if 4

that makes sense.

5 And I will, in case Darrell is on the line 6

and would like to weigh in, I'd like to give him that 7

opportunity as well. Darrell, are you on the line?

8 MR. GARDNER: Sure. So this is Darrell 9

Gardner, Senior Director of Licensing for Kairos 10 Power. And I think it's a good question.

11 What I would point out is that NQA-1 has 12 provisions for using data from various sources. And 13 so I can't remember the -- it's a non-mandatory 14 appendix. And I just don't recall the number offhand.

15 But the point we want to make is that we 16 will comply with the NQA-1 revisions in that appendix 17 to evaluate our inputs, one of which would be data.

18 So that allows the use of evaluation of equivalency of 19 QA programs. It evaluates legacy data. There are 20 several pathways in that appendix to NQA-1 for data 21 use.

22 MEMBER BALLINGER: This is Ron Ballinger.

23 Now to be clear on this, are we to assume or could I 24 assume that if it's NQA-1 qualified it's automatically 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

13 qualified according to the ANSI?

1 MR. GARDNER: One could certainly make 2

that argument, right? If you have data developed 3

under an NQA-1

program, it would bound any 4

expectations under the ANSI/ANS standard.

5 MEMBER PETTI: So, Darrell, my concern, 6

and again, I'm not a quality expert, but I ran an NQA-7 1 program of a gas reactor. And I asked my quality 8

experts sort of the same question, like, why can't I 9

just do good science and good quality and publish it 10 and then it becomes legacy data? And I don't need all 11 the extra costs from NQA-1.

12 And they told me that's not the intent, 13 you know, of what's meant, you know, that part of NQA-14 1 when one is allowed to bring in legacy data.

15 So it's probably a gray point, right? If 16 95 percent of your data was sitting out there not 17 under an NQA-1 program, that's a different situation 18 than if 95 percent is in the NQA-1 program then I got 19 to bring in 5 percent. So that's how I mentally 20 rationalize it.

21 (Simultaneous speaking.)

22 MEMBER BALLINGER: I'm a little bit 23 confused. You were saying -- I always assumed that if 24 you had an NQA-1 program for which the data qualified, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

14 then it was automatically qualified for ANSI.

1 MEMBER PETTI: Yes, I'm talking about the 2

opposite --

3 MEMBER BALLINGER: Okay, okay. That's 4

what --

5 MEMBER PETTI: -- the opposite situation 6

where they use --

7 MEMBER BALLINGER: If you use NQA-1, 8

you're good.

9 MEMBER PETTI: Yes, you're good, the best.

10 MEMBER BALLINGER: Yes.

11 MEMBER PETTI: But if you use ANSI -- so 12 it's a matter of, I think, how much of the data will 13 be under ANSI and potentially be brought in.

14 CHAIRMAN REMPE: Have you talked about 15 this with the staff and said, hey, we may be bringing 16 in some data for the test reactor in trying to qualify 17 it under NQA-1?

18 MR. GARDNER: So to be -- this is Darrell 19 Gardner again. To be clear, we're jumping ahead into 20 a particular license application question as opposed 21 to the methodology.

22 But we have not yet discussed what I would 23 argue is -- the question you're asking is about an 24 FSAR application in the actual qualification program 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

15 that was used for the graphite we're going to install.

1 With that in mind, we do have plans to discuss many 2

things about the actual FSAR application when we start 3

pre-application engagements with the staff.

4 CHAIRMAN REMPE: So for this application, 5

we are to assume what Margaret said. You're going to 6

use the ANS methodology for the test reactor and then 7

you'll have a separate set of data for the power 8

reactor and that's what we should assume that is being 9

proposed.

10 MR. GARDNER: I don't think we're saying 11 that. I think what we're saying is we will comply 12 with NQA-1 and all the provisions that it has for 13 processing data. That's a different question from 14 whether it's the exact same data set.

15 My point is I think, you know, we don't 16 want to leave a conclusion that use of these two 17 programs automatically requires independent data sets.

18 We don't believe that's the case for NQA-1.

19 MEMBER PETTI: I think this is a question 20 we can get back to when the staff talks because I 21 recall reading a limitation condition around this 22 issue, but we'll wait for the staff so.

23 MS. ELLENSON: And it might be helpful 24 also I'll just kind of quickly walk through what are 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

16 these data sets that we're talking about. Like the 1

historical data that's out there that we would be 2

using that would be non-NQA-1 for the test reactor 3

would be things like the historical data from Ibiden 4

about lot-to-lot variation, the historical data about 5

a variation in material properties over time, that 6

kind of thing.

7 That would be -- the new data that we 8

would generate for the test reactor would be under the 9

15.8 for those types of data. The data that we would 10 be using for irradiation properties was originally 11 generated under an NQA-1 program so it's kind of moot 12 for that.

13 So really when we're talking about future 14 data being collected, we're talking about power 15 reactor application data. And in that case, you're 16 talking about again the data that we would be 17 generating for the material properties of unirradiated 18 graphite, the lot-to-lot variation data that, again, 19 is historical.

20 So we would be using the NQA-1 program to 21 look at that historical data but then also the 22 irradiation data. And our intent there for something 23 that would be under the power reactor would be pulled 24 under that NQA-1 based program. That would be the new 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

17 data.

1 So when we're talking about what is the 2

actual data that is being talked about? Like Darrell 3

said the important part is if NQA-1 doesn't 4

necessarily require a new set of data. However, I 5

think that will actually end up being the case because 6

the only difference would be that irradiation data for 7

the power reactor.

8 Okay. All right. So the next slide here, 9

the code that we're going to use to qualify the 10 graphite is ASME BPV Section III, Division 5. We have 11 a couple of exceptions that we talked through in more 12 detail at the subcommittee. And we can revisit those 13 if you would like here.

14 Basically, that Division 5 code divides 15 qualification into three different

elements, 16 characterization of as-manufactured graphite. That is 17 mechanical and thermal properties and property 18 variation.

19 Characterization of properties under 20 irradiation, we call that basic irradiation properties 21 and irradiation creep and then evaluation of 22 environmental compatibility.

23 So qualification of unirradiated and 24 irradiated graphite, tackling the first part of that, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

18 unirradiated graphite, we will conduct testing from 1

mechanical properties, thermal properties, impurity.

2 We have a few limited departures from the code where, 3

for example, taking measurements at room temperature 4

as opposed to a variety of temperatures is actually 5

conservative from a modeling perspective.

6 We will be taking data both with grain and 7

against grain. And the final design of the reflector 8

will take into account uncertainty in property values 9

due to any anisotropy that we note. And I think we 10 noted at the subcommittee meeting that the difference 11 in anisotropy is not huge. We said it was something 12 on that order, 10 percent.

13 And we will be combining new testing data 14 and historical data like I mentioned. The data that 15 Ibiden has for property variation over time, that 16 would be the historical data and then the new testing 17 data that we would have for properties would be 18 comparing back to that historical data.

19 We will also use the Division 5 code, the 20 articles that are listed here for irradiated graphite 21 properties.

22 Applicable data exists for the operating 23 conditions for KP-FHR for basic irradiation 24 properties. And the data that's available is 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

19 applicable to both the power and the test reactor 1

application.

2 We will generate new test data for 3

irradiation creep for a power reactor application.

4 And also applicable data already exists for the 5

irradiation creep coefficients for the non-power 6

reactor application.

7 For environmental compatibility between 8

Flibe and ET-10, Kairos evaluated the available 9

Phenomena Identification Studies through technical 10 literature and identified these four items that are 11 listed in this chart.

12 First off, infiltration, we plan to 13 conduct testing that graphite mechanicals are not 14 degraded by infiltration itself. I would also note 15 here that freeze-thaw cycles are outside the design 16 basis for a KP-FHR. So that is really the only 17 mechanism that we expect would change physical 18 properties. So we don't expect to see any difference 19 in mechanical properties from infiltration alone.

20 I would also note that the test reactor 21 will be designed in such a way that the maximum 22 pressure in the vessel is going to be below the 23 threshold infiltration pressure so we don't expect to 24 see infiltration for a non-power reactor.

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20 DR. BLEY: Excuse me. This is Dennis 1

Bley. May I ask you a question here?

2 MS. ELLENSON: Sure.

3 DR. BLEY: That was well-qualified. You 4

don't expect to see any changes by infiltration alone.

5 Would infiltration compound or affect other mechanisms 6

that you're going to talk about next?

7 MS. ELLENSON: That's not what I intended 8

to imply. I was merely speaking to the effective 9

freeze-thaw cycles. That's all I meant by that.

10 DR. BLEY: Okay.

11 MS. ELLENSON: That there is literature 12 data that suggests that Flibe that has infiltrated and 13 gone through a freeze-thaw cycle could change physical 14 properties, but that is outside the design basis for 15 a KP-FHR.

16 Okay. Okay. So abrasion and erosion, we 17 have testing underway to demonstrate that there is no 18 significant abrasion or erosion under prototypical 19 operating conditions.

20 We are conducting those tests on 21 structural graphite in Flibe. And again this is 22 another thing that is more of a confirmatory test 23 because we don't expect to see a great deal of 24 abrasion or erosion effect.

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21 And one of the reasons that we have 1

confidence in that expectation is that the MSRE 2

operating data, which we spoke about at the 3

subcommittee, there was at least one full power 4

equivalent operating time, and there was no observed 5

abrasion or erosion on the graphite in that test.

6 We also looked at chemical compatibility.

7 We looked at the applicable literature. And 8

intercalation was the one phenomenon that was of 9

interest to ET-10 and Flibe. And the literature 10 studies indicate that intercalation in this 11 environment is thermodynamically unfavorable. So we 12 do not intend to do any further testing on that.

13 The last one on the list here is 14 oxidation. Oxidation is an interesting one. As you 15 can imagine with an inert environment like KP-FHR will 16 have, during normal operation, the oxidation would be 17 extremely low, if any. So what we're really talking 18 about are during postulated event conditions for 19 oxidation.

20 So Kairos will be measuring oxidation 21 kinetic parameters.

We'll be determining 22 relationships between weight loss and strength. And 23 then we'll be assessing oxidation depth profiles. And 24 that really is scenario dependent so we'll be giving 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

22 more information at a specific application time.

1 And then lastly we're going to do a 2

confirmatory test that submerged graphite doesn't 3

occur in a KP-FHR environment to a degree that would 4

affect its strength.

5 MEMBER HALNON: This is Greg. I have a 6

quick question on abrasion and erosion.

7 MS. ELLENSON: Great.

8 MEMBER HALNON: The surface roughness does 9

affect -- degrade infiltration to some extent based 10 on, well, surface roughness. If you see in your 11 confirmatory testing, is part of that testing that if 12 you see something that you didn't expect you would go 13 back and check for infiltration again or are they 14 mutually exclusive in that testing?

15 MS. ELLENSON: I think I might ask Chong 16 and Gabriel to weigh in. Are either of you on the 17 line that would like to answer that question?

18 MR. CHEN: Yeah, this is Chong Chen, and 19 I can answer some of the question. And the roughness 20 will impact infiltration in the way it may change the 21 contact angle of -- graphite slightly but not in a 22 huge amount.

23 I think the erosion and infiltration could 24 be two different mechanisms to impact the graphite.

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23 Abrasion/erosions stay on the surface. Infiltration 1

is really needed to generate damage once the flap goes 2

into the graphite, and it goes through a free cell 3

cycle.

4 Does this answer your question?

5 MEMBER HALNON: I guess to some extent.

6 When you do confirmatory testing, you look and see.

7 And if you don't have any further questions, you move 8

on. I guess the question more is if you saw something 9

you didn't expect, like, you know, more erosion or 10 abrasion than you expected, would you go back -- if 11 you had already done the infiltration confirmatory 12 test, would you go back and redo the confirmatory test 13 on that sample for infiltration as well just to make 14 sure that that contact angle didn't go -- you know, 15 make a huge, bigger weathered surface and cause 16 additional issues that you weren't actually looking 17 for at the time.

18 MR. CHEN: Infiltration actually covers 19 the weight, and the pressure ranges cover weight above 20 and in the regular operation condition. So if we see 21 something not usual in abrasion/erosion pass, I think 22 it is looking into more aware of graphite and that 23 leads to -- wear of a graphite, does not lead to 24 change of infiltration. And the pressure has more 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

24 impact.

1 MEMBER HALNON: Right, right. So are 2

those two confirmatory tests done on the same sample 3

then?

4 MR. CHEN: Would you restate again, 5

please?

6 MEMBER HALNON: Are those confirmatory 7

tests for infiltration and abrasion/erosion done on 8

the same sample?

9 MR. CHEN: No, it's not -- the same 10 material, but not same sample set.

11 MEMBER HALNON: Okay. I understand it's 12 not a real issue for the test reactor, but the power 13 reactor coolant infiltration is a potential -- I would 14 hope that the confirmatory test procedures would have 15 a brain in it that if you don't see anything -- if you 16 see something you're not expecting to see that you 17 would at least go back and see if the other 18 confirmatory tests are valid or not. That's just my 19 comment. You know, I understand the margin.

20 MR. CHEN: Yes, I agree. So if we see 21 something unusual, we will dive into it. I guess it 22 depends on what kind of things would work there.

23 MEMBER HALNON: Right. Okay. Thanks.

24 MR. CHEN: Thank you.

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25 MS. ELLENSON: Okay. Any other questions 1

there? Okay. Great. So in summary the Graphite 2

Material Qualification Topical Report describes how 3

we're going to qualify ET-10 for structure-related 4

graphite -- I'm sorry, for structural graphite for use 5

in a KP-FHR specifically.

6 The qualification plan conforms with that 7

Section III, Division 5, code. We have a few limited 8

departures that are described in the report. And 9

we'll use both existing data and data from new tests.

10 And then just a last note there, a reminder that 11 seismic qualification is outside the scope of this 12 particular Topical Report.

13 And that's all the prepared comments that 14 we had. Any last questions?

15 MEMBER PETTI: Yeah, I had a question on 16 the oxidation testing. It is your anticipation that 17 it's going to look like other graphite grades that 18 have similar veracity in grain size? I know you said 19 you have to do it because every grade is a little 20 different. But you're not anticipating something 21 different from the closest twin to ET-10?

22 MS. ELLENSON: Yes. No, we're not 23 expecting any --

24 MEMBER PETTI: All right.

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26 MS. ELLENSON: -- differences. But Chong, 1

do you want to weigh in? Are there any reasons to 2

think ET-10 would behave any differently?

3 MR. CHEN: No, I do not expect a huge 4

difference. The trend will be similar.

5 MEMBER PETTI: All right. Thanks.

6 MR. CHEN: Thank you.

7 MEMBER PETTI:

Members, any other 8

questions? Okay, if not, staff? I'll give them a 9

minute to get to the table.

10 PARTICIPANT: Can everybody see the 11 presentation?

12 MEMBER REMPE: Yes. But we need you to go 13 presentation mode, please?

14 PARTICIPANT: Yup. There you go.

15 MEMBER REMPE: All right. Thank you.

16 MR. CHERESKIN: Good morning, everyone.

17 This is Alex Chereskin from the NRC staff. I'm here 18 in the room today, but I am joined by my colleagues 19 Rich Rivera, Matt Gordon and Meg Audrain. So I will 20 be giving the presentation for the NRC staff's 21 evaluation of the Kairos Power Graphite Material 22 Qualification Topical Report.

23 And can I have the next slide, please? So 24 for the introduction, Kairos had requested the staff 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

27 review and approve this Topical Report. And this 1

Topical Report provides the methodology of Kairos to 2

qualify their ET-10 graphite for use in either the KP-3 FHR non-power or power reactor designs.

4 In general, the methodology proposes to --

5 MEMBER PETTI: Alex, could you move the 6

mic closer to you?

7 MR. CHERESKIN: Sorry about that.

8 MEMBER PETTI: I think everybody else can 9

hear, but in the room it's a little hard.

10 MR. CHERESKIN: Oh, sorry. Is that 11 better?

12 MEMBER PETTI: That's better, yeah.

13 MR. CHERESKIN: Okay. I'll find somewhere 14 else to put my notes, I guess.

15 Okay. So in general the qualification 16 methodology follows the ASME Code Section III, 17 Division 5, requirements, with certain deviations that 18 were reviewed and approved by the staff as we 19 discussed in the subcommittee meeting.

20 The NRC's staff's review focused on the 21 overall qualification framework. And this includes 22 the use of existing data, unirradiated testing 23 together with graphite properties or radiation 24 testing, oxidation testing and environmental testing.

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28 That includes testing in molten sale that Kairos 1

described in their presentation.

2 Next slide, please. So the regulatory 3

basis for this review includes portions of 10 CFR 50 4

and 54 that are related to information that is 5

required to be submitted in licensing applications and 6

information related to graphite material properties 7

will need to be supplied as part of a license 8

application.

9 And so the staff also evaluated the 10 Topical Report against several Kairos PDC that were 11 previously reviewed and approved by the NRC staff in 12 the referenced Topical Report.

13 The principal design criteria include PDC 14 1, quality standards and records, which requires that 15 system structures and components that are safety 16 significant be designed to quality standards 17 commensurate with safety significance.

18 PDC's 34 and 35, which are similar, 19 contain removal requirements. And the graphite 20 components will be needed to maintain structural 21 integrity and maintain physical geometry at the core 22 in order to support adequate heat removal.

23 And PDC 74, which requires the design of 24 the reactor vessel system to support the integrity of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

29 the graphite during postulated accidents to ensure 1

geometry for passive heat removal and allow sufficient 2

insertion of neutron absorbers, and the graphite will 3

be required to maintain its integrity in order to 4

achieve these functions.

5 Next slide, please. This slide is a 6

condensed version of what was discussed previously 7

over the course of several slides at the ACRS 8

subcommittee meeting. The staff's evaluation focuses 9

on a couple of specific areas, the first one being the 10 qualification of unirradiated graphite properties.

11 And the staff had found that the proposed 12 testing plan will satisfy the requirements of Section 13 III, Division 5, specifically the article listed here 14 for properties of as-manufactured graphite. In 15 addition, the Kairos Power Topic Report proposed to 16 evaluate the intra-billet and lot-to-lot property 17 variations of graphite.

18 The staff also evaluated the method to 19 qualify the irradiated properties of the ET-10 20 graphite. And, again, this is consistent with code 21 requirements for irradiated material properties for 22 graphite, which requires measurements of certain 23 irradiated properties.

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

30 presentation, this includes the basic irradiated 1

properties and the irradiation creep properties that 2

will require additional irradiation testing for the 3

power reactor design.

4 Finally, the NRC staff reviewed the 5

environmental effects testing proposed by Kairos 6

Power. This includes the molten salt infiltration 7

testing, oxidation testing and the testing for 8

abrasion and erosion. And the staff had reviewed 9

these and found them acceptable as noted in the staff 10 safety evaluation.

11 Next slide, please. So in conclusion, the 12 staff had reviewed the Topical Report and concludes 13 that the graphite material qualification program is 14 acceptable for the ET-10 graphite to be used in the 15 non-power or power reactor designs of KP-FHR as 16 described in the Topical Report and subject to NRC 17 staff limitations and conditions.

18 This Topical Report will in part meet the 19 applicable PDCs. For example with principal design 20 criteria number one, the graphite components will be 21 qualified to the ASME Code, which is, you know, 22 commensurate with the safety function of the graphite 23 components.

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

31 will help to ensure that graphite components maintain 1

their integrity, need to achieve the heat removal 2

functions of PDC 34 and 35 as well as the functions of 3

PDC 74 related to maintaining geometry, permit 4

sufficient insertion of neutron absorbers and also to 5

maintain adequate core cooling in a postulated 6

accident.

7 The NRC staff also includes certain 8

limitations and conditions on the use of this Topical 9

Report. They fall into a few broad categories. The 10 conditions are there to ensure that the data collected 11 by Kairos bounds the anticipated qualification 12 envelope for their reactor, ensure that certain future 13 actions stated in the Topical Report are reviewed and 14 approved by staff, ensure that as certain design 15 aspects change, they are appropriately addressed, for 16 example, the use of potentially an incompatible 17 intermediate coolant. That's just one example of what 18 I mean here.

19 And as Member Petti noted before, there is 20 a condition related to the use of quality insurance 21 requirements. That one was geared specifically to the 22 power reactor as stated in the condition. And that 23 was to show that the data meets code requirements for 24 the power reactor design. So there is a condition 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

32 there for the power reactor as you noted earlier.

1 Are there additional questions?

2 MEMBER MARCH-LEUBA: Yes, a qualification.

3 You just said the data must meet the Code, the ASME 4

Code requirement. Have you guys considered the 5

discussion we had earlier, is that one data is 6

developed, and there isn't quality assurance program 7

level. Have you considered the implications?

8 MR. CHERESKIN: Yes. So this is how I 9

think we've considered the implications in that the 10 way that everything is structured that this will have 11 to be reviewed as part of a license application.

12 And for a power reactor, we would have to 13 ensure that it meets NQA-1 requirements and for the 14 non-power reactor the applicable ANSI requirements.

15 And if Kairos develops separate data sets, it would 16 clearly be more work. However, in the end as part of 17 a licensing action, we would still need to make sure 18 the applicable quality requirements are met for non-19 power or power reactor design.

20 And so I think, I guess, from what I'll 21 call a licensing standpoint, we still perform that 22 review as part of a license application.

23 MEMBER MARCH-LEUBA: You can think at a 24 high level that the reason we are doing a test reactor 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

33 is to do an internal test of everything else, and 1

therefore all those results from the test reactor 2

would be available to a quality assurance level at 3

this load and not required for the power reactor.

4 So, I mean, it helps to think a little bit 5

before the power reactor comes for licensing, and we 6

know what to say.

7 MR. CHERESKIN: That makes sense.

8 MEMBER HALNON: This is Greg. Just real 9

quick, I mean, the data set which you use and how you 10 use it and what you are using it for and what you are 11 crediting makes all the difference in the world in 12 this. I mean, data to inform a design is one thing, 13 but data to credit a design is a different story. So 14 that's where my understanding of a quality program 15 data set is in play is, what are you using it for?

16 So, I mean, just like the MSRE, they are 17 using data from MSRE to inform their testing and their 18 design and their data collection. The same thing is 19 going to happen. They are going to use the test 20 reactor data to inform what they are doing with the 21 power reactor, but they are going to credit the data 22 from a safety perspective. And then they're going to 23 have to meet NQA-1 data collection and integrity and 24 all that stuff.

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34 So to me it looks like it's a question of 1

what am I using the data for not necessarily can I use 2

the data or not?

3 MEMBER PETTI: My only concern is, you 4

know, you gather the data on the test reactor QA and 5

somehow when you get to the power reactor you need to 6

credit it. And there is something you find out that 7

is missing in the QA pedigree that NQA-1 requires that 8

isn't required in ANSI.

9 I mean, they act different, you know. And 10 there is a process to dedicate ANSI. I understand all 11 that. But just make sure that it is thought through 12 because this data is not insignificant from a cost 13 perspective to gather, you know? And you don't want 14 to, you know, find out at the end.

15 MEMBER HALNON: But like what you're 16 saying, the bottom line is when you credit it, it's 17 going to have to meet NQA-1 standards --

18 MEMBER PETTI: Correct.

19 MEMBER HALNON: -- for a power reactor.

20 MEMBER PETTI: Correct.

21 MEMBER HALNON: Right.

22 MEMBER PETTI: And most of the data that 23 we talk about, you know, the irradiation, that stuff 24 is all going to be in NQA-1. That's not what I'm 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

35 talking about. And the historical data is the 1

historical data, you know.

2 MEMBER HALNON: Right.

3 MEMBER PETTI:

And that sort of 4

information but, yeah. Any other questions, members?

5 MEMBER KIRCHNER: And Dave, this is Walt.

6 MEMBER PETTI: Yeah.

7 MEMBER KIRCHNER:

May I

make an 8

observation?

9 MEMBER PETTI: Sure.

10 MEMBER KIRCHNER: It's along the lines of 11 Greg's earlier questions about cause and effect 12 between different test regimes. I just would observe 13

-- I don't think -- well, first I'll make this 14 observation. This is not part of a qualification of 15 materials per se.

It's more of a

design 16 consideration.

17 From what we note to date about the Hermes 18 design, it appears that the irradiation of the 19 graphite will not be significant for the lifetime of 20 that test reactor and probably not, you know, anything 21 close to what may be seen in the actual power reactor.

22 But with dimensional changes of graphite 23 under temperature and irradiation, then the fastening 24 structural support for this reflector system becomes 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

36 a design issue because you worry about the potential 1

with dimensional change of flow-induced vibrations.

2 Using Flibe as a coolant, there is a certain amount of 3

levitation of the graphite blocks. And any resulting 4

loose fit then could exacerbate abrasion and wear, 5

which then becomes a source for infiltration and 6

oxidation and other deleterious effects.

7 So I'm just making an observation that as 8

long as things are within the prototypical operating 9

conditions, fine. But if it turns out that the 10 dimensional changes with the graphite lead to other 11 effects, then as Greg was suggesting for example, if 12 you do see abrasion, do you go back then and look at 13 the considerations of infiltration and oxidation and 14 such?

15 So this is an observation beyond the 16 materials qualification methodology ATR to design 17 considerations for probably more so for the power 18 reactor than for the Hermes test reactor. Thank you.

19 MEMBER PETTI: Okay. No other questions 20 then I think we thank our speakers.

21 CHAIRMAN REMPE: We need to open the line 22 to public comments --

23 MEMBER PETTI: Oh, yes.

24 CHAIRMAN REMPE: -- at this time.

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37 MEMBER PETTI: Any member of the public, 1

unmute yourself, state who you are and your comment.

2 Okay. I'm not hearing any. We're ready.

3 CHAIRMAN REMPE: Okay. At this time then, 4

we're going to go off the record.

5 (Whereupon, the above-entitled matter went 6

off the record at 9:14 a.m. and resumed at 1:01 p.m.)

7 CHAIRMAN REMPE: So it's 1:01 p.m., and 8

we're back in session. And I'm going to ask Member 9

Ballinger to lead us through our next topic.

10 MEMBER BALLINGER: Thank you. Thank you, 11 Madam Chairman. We're going to cover the second 12 Topical Report, this one on metallic materials, this 13 afternoon. And we've had a pretty much very good 14 introduction this morning, which basically covered 15 both so we don't need to do that, I don't think unless 16 there is staff that wants to say something initially.

17 Is that correct? No. Okay.

18 So we'll start off with Kairos and then 19 finish with the staff. And so who at Kairos goes? Is 20 it Margaret?

21 MR. PRICE: No. This is John Price. Can 22 you hear me okay?

23 MEMBER BALLINGER: We can hear you fine.

24 MR. PRICE: Okay. Hello.

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38 MEMBER BALLINGER: Take it away.

1 MR. PRICE: Okay. Thank you very much.

2 Hello, my name is John Price. I'm a senior licensing 3

engineer for Kairos Power. And I'll be presenting 4

with Dr. George Young the slides for the Metallic 5

Materials Qualification Licensing Topical Report Rev.

6 4.

7 First of all, I'd like to thank the full 8

committee for this opportunity to make this 9

presentation. This is a summary of the presentation 10 given to the ACRS Subcommittee on January 12.

11 Slide 2. As we always start off, our 12 company's mission is to enable the world's transition 13 to clean energy with the ultimate goal of dramatically 14 improving people's quality of life while protecting 15 the environment.

16 What this means as we go through this 17 meeting is that if the Licensing Topical Report gets 18 approval, we are one step closer to transitioning to 19 a cleaner energy and improving people's quality of 20 life while protecting the environment.

21 Slide 3. Dr. Young and I would like to 22 present the Metallic Materials Qualification Topical 23 Report and our methods used to qualify these materials 24 for use in the KP-FHR, specifically addressing the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

39 environmental effects on materials.

1 MEMBER BALLINGER: Excuse me. This is Ron 2

Ballinger. Somebody is crinkling paper, doing 3

something in the background. So whoever it is, could 4

you mute your microphone, please, unless it's the 5

speaker, in which case, stop crinkling it.

6 MR. PRICE: You got it.

7 CHAIRMAN REMPE: It's a technical term, 8

right?

9 MEMBER BALLINGER: Okay. Thanks.

10 MR. PRICE: Yeah. Today Dr. Young and I 11 would like to present the Metallic Materials 12 Qualification Topical Report and our methods used to 13 qualify these materials for use in the KP-FHRs, 14 specifically addressing the environmental effects on 15 materials.

16 The testing plan is for metallic materials 17 used in Flibe-wetted areas for safety-related, high 18 temperature components in non-power test reactors, 19 which we will call Hermes, and for the commercial 20 power reactor, which we will call KPX.

21 The materials, 316H and the associated 22 Weld Filler Metal 16-8-2, were chosen because of 23 existing qualification in high temperature 24 applications and because they are provided by the ASME 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

40 Code Section III, Div. 5, and endorsed by Reg. Guide 1

1.87.

2 The materials used to exhibit desirable 3

mechanical properties have demonstrated compatibility 4

with Flibe salt and have extensive experience based in 5

nuclear applications.

6 MEMBER BALLINGER: This is Ron Ballinger.

7 I'm told by our staff that 1.18 -- Reg. Guide 1.87 is 8

now on the street.

9 MR. PRICE: Great. The metals are used in 10 other industry applications, near time and temperature 11 with the KP-FHR.

12 Qualified materials provide assurance that 13 components can be designed for extremely low 14 probability of abnormal leakage, resistance to rapidly 15 propagating failure and resistance to gross rupture.

16 As this is a methodology document, the 17 demonstration of qualification will be documented in 18 the safety analysis reports as part of our future 19 licensing actions, provided the limitations specified 20 in the staff safety evaluation are met.

21 Slide 4. The Alloy 316H is qualified by 22 ASME Code Section III, Div. 5, for 816°C. The 23 associated Weld Filler Metal 16-8-2 is current 24 qualified for only 650°C.

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41 The ASME qualification of the weld filler 1

metal will be extended by testing to match the base 2

metal temperature for Alloy 316H. This will be 3

provided by elevated temperature tensile testing, 4

creep-fatigue testing and by creep-rupture testing.

5 The qualification for the power reactor 6

will satisfy NQA-1 based QA program and the 7

qualification for the non-power test reactor will 8

satisfy ANS-15.8 1995-based program.

9 There is a limitation stated in the draft 10 SC that Kairos Power plans on complying with. At this 11 time, I'm going to turn it over to Dr. George Young, 12 if there are no other questions, to complete the open 13 session presentation.

14 Dr. Young is a fellow scientist at Kairos 15 Power. Dr. Young has a BS in materials engineering 16 from Rensselaer Polytechnic Institute and an MS and 17 PhD degrees in material science from the University of 18 Virginia.

19 He has over 30 years of experience in the 20 nuclear power industry and is an expert with material 21 selection and performance for both conventional and 22 advanced nuclear power systems.

23 At Kairos

Power, Dr.

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

42 environmental degradation testing. Dr. Young has 1

authored over 50 peer-reviewed articles and book 2

chapters in the research areas of environmental 3

assisted cracking, welding metallurgy and physical 4

metallurgy. So, Dr. Young, take it away.

5 DR. YOUNG: Thanks, John. Hopefully, you 6

can hear me okay.

7 MEMBER BALLINGER: We can hear you fine.

8 DR. YOUNG: Great. Thank you. If we go 9

to the next slide. All right. We used the Phenomena 10 Importance and Ranking Table, the PIRT, approach for 11 the Metallic Materials Testing Program. We convened 12 the panel of experts about four years ago now, three, 13 four years ago.

14 And this PIRT review identified and ranked 15 the appropriate environmental degradation phenomena 16 that are applicable to the Flibe-wetted safety-related 17 components of our KP-FHR reactor technology.

18 From that review, we highlight that the 19 reactor vessel is the only safety-related structural 20 metallic component which serves the function of 21 retaining the coolant around the fuel and that the 22 PIRT -- and again, this PIRT was for the power reactor 23

-- identified two potential accident scenarios that 24 could affect the structural integrity of these Flibe-25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

43 wetted safety-related components.

1 I note that these effects are mitigated by 2

design features. Those are air ingress into the 3

reactor and the potential for intermediate cooling 4

ingress into the primary coolant Flibe that only 5

pertains to the power reactor.

6 For the demonstration reactor, Hermes, we 7

a have a Flibe to air heat exchanger so there is no 8

intermediate coolant.

9 So that testing program that was informed 10 by the PIRT consists of kind of two major efforts, 11 testing and high temperature air to support ASME 12 design and then testing in molten Flibe salt to 13 account for any potential environmental degradation.

14 Next slide. So for the test in high 15 temperature air on Alloy 316H, these tests that 16 support the ASME model calibration and validation 17 include tensile testing, stress relaxation testing, 18 strain rate change, sometimes called stress dip tests, 19 uniaxial creep testing, notch bar creep-testing and 20 creep-fatigue testing so quite an extensive high 21 temperature air testing program to validate our high 22 temperature design.

23 Next slide. So as far as environmental 24 degradation, we grouped these in kind of four 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

44 categories. So these are the phenomena that were 1

assessed in detail based on the PIRT ranking. And 2

these form the basis for our testing plans.

3 So corrosion testing in Flibe, we intend 4

to perform, and are performing, corrosion tests in 5

Flibe. Those use compositional analysis of the salt 6

and also electrochemical potential monitoring to 7

monitor the test conditions there.

8 We identified environmentally assisted 9

cracking now where there may be some interaction of 10 the Flibe environment with applied stress on the 11 material. And we intend to assess the well-accepted 12 slow strain rate methodology, a very severe tensile 13 test in Flibe salt, and also fracture mechanics-based 14 testing where now we're using pre-crack samples to 15 look at corrosion fatigue and the potential for stress 16 corrosion cracking.

17 Then additionally, we'll use both our slow 18 strain rate test for the power reactor dedicated test 19 to look at the potential interaction of pre-bloating 20 in the Flibe environment.

21 The next topic on the upper right here is 22 kind of a catch-all we call metallurgical effects or 23 kind of other phenomena. Here we're going to look at 24 potential degradation modes like stress relaxation 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

45 cracking, phase formation, embrittlement. And we did 1

consider thermal cycling and thermal striping quite a 2

bit. I want to note that last bullet is mitigated by 3

design and don't require any additional testing.

4 Lastly, we assessed irradiation effects or 5

potential effects. These include just irradiation 6

induced embrittlement and then potential interactions 7

with the Flibe, irradiation affected corrosion and 8

irradiation assisted stress corrosion crack. So 9

that's an overview.

10 Next slide. So in summary, we have two 11 major efforts here. We are doing metallic materials 12 qualification testing to support the design and 13 licensing of both the non-power reactor Hermes and the 14 commercial power generation reactor, what we call KPX.

15 The scope of the testing is limited to the 16 structural alloys, the Base Metal 316H, and the Weld 17 Filler Metal 16-8-2. Those were used for construction 18 of the reactor vessel and, again, that's with 19 determining the primary safety related component of 20 interest.

21 The reactor vessel maintains the inventory 22 of Flibe coolant around the fuel pebbles and that's 23 the safety function so that we can credit the Flibe 24 salt as another barrier to the fission products.

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46 And by using qualified materials like 1

these, we are providing assurance that the reactor 2

vessel can be designed for extremely low probability 3

of abnormal leakage, resistance to reactor leak 4

propagating failure and resistance to gross rupture.

5 So materials testing then consists of two 6

major efforts. That's in the tests we discussed in 7

high temperature air that support ASME design as well 8

as extension of the ASME Code for the weld filler 9

metal up to 816C and then the testing of the molten 10 Flibe salt to assess the potential environmental 11 degradation modes.

12 Any questions on that?

13 MEMBER KIRCHNER: George, this is Walt 14 Kirchner, just a clarification. You're limiting the 15 scope of testing for the reactor vessel, but I presume 16 you intend to use these same alloys for the primary 17 coolant boundary?

18 DR. YOUNG: That's right. All our piping 19 or hot leg and cold leg piping is 3/16th inch.

20 MEMBER KIRCHNER: Thank you.

21 MEMBER BALLINGER: Any questions from the 22 members, consultants? Okay. I should have mentioned 23 we have the possibility of a closed session if we need 24 it for this, but so far we haven't needed one. But if 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

47 we need one, we have that opportunity. So if there 1

aren't any questions from the members and consultants, 2

we can thank you very much for your presentation and 3

then is the staff ready to go?

4 MR. RIVERA: Hi. This is Richard Rivera, 5

and yes, I have the presentation on my screen as soon 6

as you are available to share my screen.

7 CHAIRMAN REMPE: Would the folks from 8

Kairos please quit sharing?

9 DR. YOUNG: Will do.

10 CHAIRMAN REMPE: Thank you.

11 MEMBER BALLINGER: Well, we'll get there.

12 We'll get there.

13 CHAIRMAN REMPE: Okay. Time for the staff 14 to share.

15 MR. RIVERA: Let me know if you can see 16 the screen.

17 MEMBER BALLINGER: Yes, we can. Thank 18 you.

19 MR. RIVERA: All right. Thank you. And 20 John Honcharik was the lead reviewer for this Topical 21 Report and will lead the presentation.

22 MR. HONCHARIK: Thanks, Rich. I'll turn 23 my microphone.

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

48 you can -- have it pretty close to you if you can.

1 MR. HONCHARIK: Thank you. Is this good?

2 Good afternoon. I'm John Honcharik, Senior Materials 3

Engineer in the Division of New Licenses.

4 Alex Chereskin in the Division of Advanced 5

Reactors also reviewed this Topical Report with me.

6 I will present to you our evaluation and conclusion of 7

the Metallic Materials Qualification Topical Report 8

for use in the Kairos fluoride salt-cooled reactor.

9 Next slide. The NRC staff reviewed the 10 Topical Report, which provides the qualification plan 11 for metallic structural materials used in Flibe-wetted 12 areas for safety-related high temperature components 13 of the KP-FHR power and non-power test reactors.

14 The planned material testing includes 15 analysis and monitoring programs that will be used to 16 address the materials reliability and compatibility of 17 the metallic material in an environment of the KP-FHR 18 designs in order to partially satisfy PDC 14 and 31 of 19 the Kairos principal design criteria that was approved 20 by the staff in Topical Report KPR-003.

21 These PDCs are applicable to the 22 qualification of the metallic components for the 23 Kairos designs on which the staff based this review.

24 And the results of these planned tests and analysis 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

49 will be provided in future licensing applications that 1

references Topical Report along with the detailed 2

description of the design, inspection and surveillance 3

programs for the KP-FHR designs in order to 4

demonstrate the materials reliability.

5 Next slide. The staff's review focused on 6

the overall testing framework to conclude there is 7

reasonable assurance that the testing for 8

environmental effects of Flibe on metallic structural 9

materials provided in Section 4 of the Topical Report 10 will partially satisfy PDCs 14 and 31.

11 The specific topics reviewed include the 12 materials, which are 316H and ER16-8-2 stainless steel 13 weld metal. The test environment and the four 14 degradation categories, which were corrosion, 15 environmentally-assisted

cracking, effects on 16 metallurgical properties and irradiation.

17 Next slide. First, we'll discuss the 18 material to be used. The metallic structural 19 materials proposed for KP-FHR designs are 316H, also 20 known as stainless steel, and the associated ER16-8-2 21 stainless steel weld fill metal.

22 These materials are qualified for use in 23 ASME Code,Section III, Division 5, for high 24 temperature applications with respect to mechanical 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

50 properties. Division 5 of Section III, as someone 1

pointed out, is endorsed in Regulatory Guide 1.87, 2

Rev. 2, which was just published, I believe, 3

yesterday.

4 There is a Limitation and Condition 4 5

related to the weld material mechanical properties 6

since the fill metal is not currently qualified to the 7

higher temperatures necessary to support the accident 8

scenarios of the KP-FHR designs. Therefore, NRC 9

imposed the condition that the fill metal must be 10 qualified to the temperature in accordance with the 11 ASME Code Section III, Division 5, requirements that 12 bound postulated accident conditions and are approved 13 by the staff.

14 Next slide. Next, we will discuss the 15 test environments used for the proposed material 16 testing. The staff found that the material testing 17 environment duplicates the operating environment for 18 the Kairos designs for both normal operating and 19 postulated accident conditions.

20 There is a Limitation and Condition 3 21 which requires that if the time and temperature for 22 both normal and postulated accident conditions change 23 for the Kairos designs, they must still be bound by 24 the NRC-endorsed ranges found in Table 2 of Reg. Guide 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

51 1.87 for the 316H and fill metal.

1 NRC staff also finds the impurity test 2

acceptable since it will be conducted for the 3

commercial power reactor similarly intermediate salt 4

ingress and air ingress into the Flibe salt while the 5

non-power test reactor testing will similarly air 6

ingress into the Flibe.

7 In addition, Limitation and Condition 8 8

applies since the details of impurity testing, that is 9

the concentration of the contaminants have not been 10 determined. Therefore, the condition states that the 11 specific concentration of each contaminant used in 12 impurity effects testing shall bound accident 13 scenarios postulated in the transient analysis for the 14 KP-FHR designs.

15 MEMBER BALLINGER: This is Ron Ballinger.

16 I have a question about since 1.87 endorses Division 17 5, aren't these limitations and conditions in effect 18 redundant because assuming that they satisfy both 1.87 19 and the ASME Code, don't those documents require you 20 to do these tests in effect to meet those limitations 21 and conditions?

22 MR. HONCHARIK: No. The ASME Code for 23 metallics does not provide what you need to do for 24 testing for environmental compatibility.

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

52 MEMBER BALLINGER: I'm not talking about 1

the environmental part. I'm talking about the 2

mechanical part.

3 MR. HONCHARIK: The mechanical part, yes.

4 MEMBER BALLINGER: Yes.

5 MR. HONCHARIK: Mm-hmm. Right. Yeah. I 6

think what we're saying here is the limitation and 7

condition is that you have to do it. You have to have 8

it qualified so that your accident temperature, 9

whatever that will be, that they are postulated by the 10 transient air.

11 MEMBER HALNON: Okay. So this is Greg.

12 That answers I think a question I had about this.

13 Like the filler material qualification, it is not 14 qualified to the higher temperature because it just 15 wasn't tested that high. It's not the technical issue 16 where something happens to the grain structure or 17 something, is it?

18 MR. HONCHARIK: Right.

19 MEMBER HALNON: Okay.

20 MEMBER BALLINGER: But again, not to beat 21 a dead horse, but the point is if the filler gets the 22 material in Section II so then you can use it in 23 Section V, it has to be qualified for a temperature 24 that is at least, I think 25 degrees or so higher than 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

53 the operating temperature.

1 So the limitation and condition is 2

redundant because just the application applying to the 3

Code means you're going to have to do that testing to 4

get in Section II.

5 MEMBER HALNON: Is operating temperature 6

the same as accident temperature?

7 MEMBER BALLINGER: Well, they don't call 8

it operating or maximum. They just call it maximum 9

temperature.

10 MEMBER HALNON: Maximum temperature. Okay.

11 MEMBER BALLINGER: Corrosion is a different 12 story.

13 MR. HONCHARIK: All right. Next slide.

14 The next topic is the degradation mechanisms. The 15 first is corrosion. This includes the various types 16 of corrosion, such as general corrosion, crevice 17 corrosion, thermal aging, erosion and wear.

18 So the NRC staff found the proposed 19 testing acceptable to determine the impacts Flibe has 20 on the corrosion rates of materials based on several 21 variables including temperature, microstructure, salt 22 composition, which would include the nominal redox and 23 impurity ingress chemistries,

geometry, 24 erosion/corrosion, thermal aging, presence of graphite 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

54 and redox control. The corrosion rates of 316H and 1

its fill metal can be determined from these proposed 2

tests.

3 The next degradation category is 4

environmentally-assisted cracking.

For stress 5

corrosion cracking and corrosion fatigue, the NRC 6

found the proposed testing plan provides reasonable 7

assurance in determining the crack growth rates for 8

fatigue and stress corrosion cracking relative to the 9

environment of the Kairos designs.

10 For environmental creep degradation, the 11 NRC staff found the proposed testing plan acceptable 12 because creep testing in both nominal Flibe and in air 13 would be conducted to determine if the Flibe 14 contributes additional degradation beyond those 15 determined in the creep test performed on the air.

16 Also additional testing will be required to quantify 17 any increase in degradation caused by the Flibe.

18 Next slide. Next is metallurgical effects 19 degradation as designated in the Topical Report.

20 For stress relaxation cracking, the NRC 21 staff found the proposed testing acceptable because 22 testing air is acceptable since the triaxial stresses 23 are the major contributors to stress relaxation 24 cracking not the environment. And the tests will be 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

55 used to conduct failure future analysis and design 1

requirements of the Kairos designs.

2 For phase formation embrittlement, the NRC 3

staff found the proposed testing plan acceptable 4

because the testing will determine whether the 5

material picks up any element during its exposure to 6

Flibe and form a deleterious second phase.

7 As part of this testing, Condition 11 is 8

applicable, which states that, if intermetallic 9

formation occurs, an applicant will need to perform 10 testing to quantify the effects on the mechanical 11 properties of 316H and the associated weld metal.

12 For thermal cycling, the NRC found that 13 the thermal stresses will be addressed by conducting 14 analysis through refined design and operation of the 15 Kairos designs.

16 As part of this testing

analysis, 17 Condition 12 applies in that the applicant will assess 18 the thermal cycling and striping in future licensing 19 submittals by minimizing the thermal gradients via 20 appropriate design and operating conditions.

21 Next slide.

The next degradation 22 mechanism is irradiation-induced effects. The NRC 23 staff found the testing acceptable for irradiation-24 induced embrittlement because the degradation factors 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

56 will be based on existing data and supplemented by 1

irradiation tests conducted on material to quantify 2

design margins at the irradiation levels for the non-3 power test reactor and the commercial power reactor.

4 As part of this testing, Limitation and 5

Condition 13 would apply and that the test environment 6

shall bound the Kairos designs, including expected 7

irradiation damage and healing content.

8 For irradiation-affected corrosion, the 9

NRC found the proposed testing plan acceptable because 10 existing data will be used to develop degradation 11 factors and be monitored by a materials surveillance 12 program and in addition an inspection program.

13 As part of this surveillance and 14 inspection program, Condition 14 applies in that the 15 material surveillance program and inspection and 16 monitoring program must be implemented for the non-17 power test reactors and commercial power reactors.

18 And finally for irradiation-assisted 19 stress corrosion cracking, the NRC found the proposed 20 testing plan acceptable because stress corrosion 21 cracking testing program specified in Section 4 will 22 determine if stress corrosion cracking is a credible 23 degradation mechanism and a materials surveillance 24 program will be used to monitor the irradiation stress 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

57 corrosion cracking for the non-power reactor and 1

commercial power reactor systems. In addition, 2

Condition 14 also applies.

3 Next slide. So in conclusion, the staff 4

finds that there is reasonable assurance that the 5

material testing

plan, including

analysis, 6

surveillance and monitoring for 316H and ER16-8-2, 7

with the limitations and conditions noted in the 8

safety evaluation can be used to provide the necessary 9

information to address the materials reliability and 10 compatibility in the environment of the Kairos 11 designs. And that is because testing duplicates the 12 material operation and accident condition environments 13 that the material will experience in these designs.

14 The material test samples are 15 representative of actual weldments. Analysis will be 16 performed to mitigate stress relaxation cracking and 17 thermal cycling through design and operations.

18 The material surveillance program will be 19 used to monitor for irradiation effects on corrosion 20 and stress corrosion cracking.

21 And, as I stated before, the results of 22 these planned tests and analysis will be used for 23 future licensing applications to ensure the components 24 perform its safety function and that there will be an 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

58 extremely low probability of normal leakage or rapidly 1

propagating failure, which would partially satisfy 2

PDCs 14 and 31.

3 And that concludes my presentation.

4 MEMBER BALLINGER: Thank you. I have one 5

last -- well, I have a question. How does the 6

document compare with the ESG?

7 MR. HONCHARIK: Oh, are you talking about 8

the ISG Report?

9 MEMBER BALLINGER: The ISG.

10 MR. HONCHARIK: Yes. It is very similar 11 to it. I think we basically were reviewing this --

12 MEMBER BALLINGER: Similar?

13 MR. HONCHARIK: -- at the same time.

14 MEMBER BALLINGER: Yeah.

15 MR. HONCHARIK: So we kind of, you know --

16 MEMBER BALLINGER: Okay.

17 MR. HONCHARIK: -- used this as a --

18 MEMBER BALLINGER: For the record --

19 MR. HONCHARIK: -- template.

20 MEMBER BALLINGER: -- very, very close.

21 MR. HONCHARIK: Yes.

22 MEMBER BALLINGER: Questions from the 23 members?

24 MEMBER HALNON: Were any of the limitations 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

59 and conditions, were any of those controversial in any 1

way? Did the applicant accept all of those as a good 2

thing?

3 MR. HONCHARIK: Yeah, from what I know, 4

yeah, there was no really confrontational report --

5 MEMBER HALNON: Okay.

6 MR. HONCHARIK: -- of those conditions.

7 MEMBER HALNON: So technically everybody 8

agrees that this is good stuff?

9 MEMBER BALLINGER: It's hard not to agree.

10 It's very extensive. Other questions? I don't think 11 we need a closed session then. So we need to go out 12 and ask the public for comments. So if you're a 13 member of the public and you would like to make a 14 comment, please do whatever it takes to unmute 15 yourself and make your comment. Thank you.

16 Hearing no comments, thank you very much.

17 And I'll turn it back over to you, Madam Chairman.

18 CHAIRMAN REMPE: Thank you. So at this 19 point, we're going to go off the record. And that 20 will be going off the record for the rest of this 21 meeting, so thank you, Mr. Court Reporter.

22 (Whereupon, the above-entitled matter went 23 off the record at 1:34 p.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

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

Metallic Materials Qualification Topical Report ACRS Kairos Power Full Committee Meeting February 1, 2023

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

Purpose:

This report presents a materials testing plan methodology, including analysis and monitoring, for metallic structural materials used in Flibe-wetted safety-related high temperature components.

The materials include Alloy 316H and Weld Filler Metal 16-8-2. These materials were chosen because of existing qualification in high temperature applications and because they are provided by ASME Code,Section III, Division 5 and endorsed by Regulatory Guide 1.87.

Alloy 316H and its weld metals exhibit desirable mechanical properties, have demonstrated compatibility with Flibe salt, and have an extensive experience base in nuclear applications.

Alloy 316H and its weld metals are used in other industry applications near the time and temperature of the KP-FHR.

Qualified materials provide assurance that components can be designed for extremely low probability of abnormal leakage, resistance to rapidly propagating failure, and resistance to gross rupture.

• Scope: The report is applicable to both the KP-FHR test reactor and power reactor designs, provided the limitations specified in the report are met.

The material qualification test results generated by this methodology will be used as a basis in future licensing actions to address materials reliability and environmental compatibility in KP-FHR reactor designs.

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

4 Codes and Standards Applicability

• ASME Code Alloy 316H and Weld Filler Metal 16-8-2 are approved materials for high temperature reactors in ASME Code,Section III, Division 5 Alloy 316H is qualified for 816°C Weld Filler Metal 16-8-2 is currently qualified to 650°C The ASME qualification of weld filler metal 16-8-2 will be extended by testing to match the base metal temp for Alloy 316H:

Elevated Temperature Tensile Testing Creep-Fatigue Testing Creep-Rupture Testing

• Quality Assurance

• The qualification for the power reactor will satisfy an NQA-1 based QA program

• The qualification for the test reactor will satisfy an ANSI/ANS-15.8-1995 based QA program

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

5 Testing Program Overview

• A phenomena importance and ranking table (PIRT) was created for the metallic materials testing program

• The PIRT review identified and ranked the appropriate environmental degradation phenomena that are applicable to the Flibe-wetted safety-related components of the KP-FHR.

• The reactor vessel is the only safety-related structural metallic component which serves the function of retaining the coolant around the fuel.

The PIRT identified two potential accident scenarios that could affect the structural integrity of Flibe-wetted safety-related components (Note that these effects are mitigated via design features):

air ingress into the reactor intermediate coolant ingress into the Flibe (power reactor only)

• The testing program is informed by the PIRT results and consists of two major efforts:

testing in high temperature air to support ASME design, and testing in molten Flibe salt to account for potential environmental degradation.

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

6 Testing Program Overview (continued)

• The following tests are conducted for Alloy 316H stainless steel to support model calibration and validation of ASME design methodologies (all conducted in high temperature air):

Tensile Testing Stress Relaxation Testing Strain Rate Change (Stress Dip) Testing Uniaxial Creep Testing Notch Bar Creep Testing Creep-Fatigue Testing

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

7 Testing Program Overview (continued)

• Corrosion Corrosion Testing with Use of Compositional Analysis and Electrochemical Potential (ECP) Monitoring

• Environmentally Assisted Cracking Slow Strain Rate Testing (SSRT)

Fracture Mechanics Based Testing -

Corrosion Fatigue (CF) and Stress Corrosion Cracking (SCC)

Environmental Creep Testing

• Metallurgical Effects / Other Stress Relaxation Cracking Phase Formation Embrittlement Thermal Cycling / Striping

• Irradiation Effects Irradiation-Induced Embrittlement Irradiation-Affected Corrosion Irradiation-Assisted Stress Corrosion Cracking (IASCC)

• The following potential degradation phenomena were assessed in detail and form the basis for the testing plans:

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

8 Summary

• Metallic materials qualification testing is being conducted to support the design and licensing of both the non-power test reactor (Hermes) and the commercial power generation reactor (KP-X).

The scope of testing is limited to structural alloys 316H and 16-8-2 for the reactor vessel, which was determined to be the primary safety-related component of interest The reactor vessel maintains an inventory of Flibe coolant around the fuel pebbles (fission product barriers).

Qualified materials provide assurance that the reactor vessel can be designed for extremely low probability of abnormal leakage, resistance to rapidly propagating failure, and resistance to gross rupture.

• The materials testing consists of two major efforts:

testing in high temperature air to support ASME design, ASME qualification extension, and testing in molten Flibe salt to account for potential environmental degradation.

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

Graphite Material Qualification Topical Report ACRS Full Committee Meeting February1, 2023

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

Purpose:

This report presents the methods for qualifying structural graphite for use in KP-FHRs Qualification is subject to the conditions specified in topical report

• Scope: This report is applicable to a KP-FHR test or power reactor provided that the report conditions are met

• Graphite to be Qualified: ET-10 is a superfine grain graphite with nearly isotropic properties

• Safety Functions The graphite reflector provides a physical pathway for maintaining core cooling and a physical pathway for reactivity control element insertions Structural integrity ensures the safety functions can be met

• Quality Assurance The qualification for the power reactor will satisfy an NQA-1 based QA program The qualification for the test reactor will satisfy an ANSI/ANS-15.8-1995 based QA program 3

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

4 ASME Code Application

• The qualification plan follows the ASME BPV,Section III, Division 5, code with a few exceptions.

A portion of the code specifically addresses graphite materials Graphite Qualification Subject Areas Unirradiated Graphite Irradiated Graphite Environmental Compatibility

• The code and the topical report organize qualification into three elements:

Characterization of as-manufactured graphite mechanical and thermal properties Characterization of graphite properties under irradiation Environmental compatibility

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

5 Qualification of Unirradiated and Irradiated Graphite

• Qualification for unirradiated ET-10 would follow ASME Code III (5), As-Manufactured Graphite:

Kairos Power will conduct testing for mechanical properties, thermal properties, and purity with limited departures from the code.

Both with grain and against the grain properties will be measured. The final design of the reflector structure will take into account uncertainty in property values due to anisotropy.

A combination of testing data and historical data will be used to assess property variation.

• Qualification will apply ASME Code III (5) HHA-2200, Material Properties for Design and HA-III-3000 Properties to be Determined, for irradiated graphite properties.

Applicable data exists for basic irradiation properties for use in either a power and test reactor application.

Kairos Power will generate new test data to characterize irradiation creep for a power reactor application.

Applicable data exists for irradiation creep coefficients for use in a test reactor application.

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

6

• Phenomena relevant to qualification were identified through review of applicable phenomena identification studies and other technical literature Environmental Compatibility Between Flibe and ET-10 Phenomenon Qualification Plan Purpose Infiltration Confirmatory testing (applicable to power reactor conditions only)

Confirm that graphite mechanical properties are not degraded by Flibe infiltration.

Abrasion and Erosion Confirmatory testing Demonstrate no significant abrasion or erosion under prototypical operating conditions.

Chemical Compatibility No testing planned Applicable literature indicates that intercalation is thermodynamically unfavorable in Flibe.

Oxidation Testing (applicable to test and power reactors)

Measure ET-10 oxidation kinetic parameters; determine weight loss vs strength; determine oxidation depth profile; confirm that oxidation of submerged graphite does not occur to a degree that would affect strength.

Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

7 Summary

• The qualification plan in the Graphite Material Qualification Topical Report describes the plan to qualify ET-10 for safety-related structural graphite component design for use in a KP-FHR.

• The qualification plan conforms with the ASME BPV,Section III, Division 5, code with limited departures.

• The qualification plan will use existing data and data from new tests.

• Seismic qualification of the reflector structure is outside the scope of the topical report.

NRC Evaluation of KP-TR-014-P, Graphite Material Qualification for the Kairos Power Fluoride Salt-Cooled High Temperature Reactor (KP-FHR), Rev. 4 Alex Chereskin Matt Gordon Meg Audrain US Nuclear Regulatory Commission February 1, 2023

Introduction 2

Kairos Power, LLC requested staff review and approval of KP-TR-014-P, Rev. 4, Graphite Material Qualification for the Kairos Power Fluoride Salt-Cooled High Temperature Reactor (KP-FHR)

KP-TR-014-P, Rev 4 provides a methodology by which the Kairos ET-10 graphite will be qualified for use in either a KP-FHR non-power or KP-FHR power reactor The staffs review focused on the overall qualification framework including:

Evaluation against ASME Code Section III Division 5 requirements (Regulatory Guide 1.87, Revision 2)

Use of existing data Unirradiated testing Irradiation testing Oxidation testing Molten salt testing

Regulatory Basis 3

Title 10 of the Code of Federal Regulations (10 CFR) Sections 50.34(a),

50.34(b), and corresponding regulations for design certification applications, combined license applications and standard design approvals The following Kairos PDC are applicable to this topical report and were previously approved by the NRC staff (KP-TR-003-NP-A):

KP-FHR PDC 1, Quality standards and records KP-FHR PDC 34, Residual heat removal KP-FHR PDC 35, Passive residual heat removal KP-FHR PDC 74, Reactor vessel and reactor system structural design basis

Staff Evaluation

• Qualification of Unirradiated Graphite

• The NRC staff found that the proposed testing plan will satisfy the requirements of ASME Code Section III Division 5 (Section III Division 5)

Article HHA-III-3100, As-Manufactured Graphite

• Intra-billet and lot-to-lot property variation

• Irradiated Properties

- HHA-2220, "Irradiated Material Properties" requires measurements for irradiated properties

- ORNL data is used for basic properties

- Additional irradiation testing for irradiation creep for the power reactor design

• Environmental Effects

- Infiltration, oxidation, abrasion and erosion 4

5 Conclusions

• The staff reviewed the topical report KP-TR-014-P, Rev. 4 and concludes that the graphite material qualification program is acceptable for ET-10 graphite to be used in either non-power or power designs of the KP-FHR.

• Will meet applicable PDCs, in part Graphite components will be qualified to ASME Code consistent with PDC 1 Graphite component integrity is needed to achieve PDCs 34, 35, and 74

• Subject to NRC staff limitations and conditions Needed to ensure data bounds anticipated conditions Ensures certain future actions stated in the topical report are reviewed Ensure that if certain design aspects change, they are appropriately addressed

6 Questions?

7 BACK-UP SLIDES

Limitations and Conditions 1.

The NRC staff finds that it is necessary to limit applicability of the topical report consistent with the limitations listed by Kairos in Section 7.2, Limitations, of the topical report. An applicant referencing this topical report will need to demonstrate that these limitations are met at the time of a license application, subject to NRC staff review and approval.

2.

In the topical report, KP described several action items to be performed in the future. These action items, as described below, are subject to NRC staff review and approval once submitted with an application:

1.

Section 3.1.1 states that KP will perform low cycle fatigue testing to demonstrate that ET-10 follows the same fatigue trends as H-451 and PGX.

2.

Section 3.2 states that in order to use historical data, KP will verify that the historical data is applicable as per the process described in Appendix B of the topical report.

3.

Section 4.3 states that the qualification envelope from the irradiation data will be shown to envelope the operating conditions of the reactor.

4.

Section 4.3 states that the ORNL irradiation data will be used to estimate the turnaround fluence with confidence intervals.

5.

Section 4.3.1.2 states that irradiation creep target test temperatures are selected to bound operating conditions, and that the power reactor lifetime is bounded by irradiation creep testing conditions.

6.

Section 4.3.1.2 states that tertiary creep will be identified if it occurs.

7.

Section 4.3.2.2 states that a conservative turnaround fluence limit will be calculated, and that it will be shown that the non-power reactor does not exceed this limit.

8.

Section 5.2 states that KP will quantify wear rates of the graphite via tribological testing with the carbon pebbles, and confirm that no significant loss of volume occurs due to erosion via visual inspection of graphite exposed to moving Flibe.

9.

Section 7.2 states that the design will preclude the coincident effects of oxidation and irradiation that may inhibit the reflector from performing its safety function.

8

Limitations and Conditions 3.

The NRC staffs review and approval of this topical report was conducted against the 2017 Edition of Section III Division 5 and the associated staff endorsement, and associated conditions. Therefore, approval of this topical report is only applicable for the 2017 Edition and any deviations not described in this topical report or use of updated BPVC versions would require separate review and approval.

4.

The approval of this qualification methodology is only applicable to the Kairos power and non-power test reactor designs. Graphite will experience different changes to its properties as a function of its operating environment (e.g., temperature, fluence, coolant). Additionally, graphite components may have different safety functions and damage tolerance depending on the specific reactor design. Therefore, the specifics of this methodology may not be applicable to other designs.

5.

If a salt other than the Flibe used as the primary coolant (e.g. nitrate) salt is used in the intermediate loop for either the power or non-power reactor designs, an applicant referencing this topical report must demonstrate that no adverse effects of graphite exposure to the intermediate salt will occur and quantify these effects to demonstrate that the graphite components can perform their safety functions.

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Limitations and Conditions 6.

The approval of this topical report is limited to the qualification testing methodology for ET-10 graphite.

The NRC staff did not review topics such as the reflector design, margins, monitoring, surveillance, or inspection programs. The approval of this topical report does not include a determination of an acceptable operating life for the graphite components. An applicant will need to demonstrate an acceptable graphite component lifetime based on intended function of the graphite blocks, damage tolerance, reflector design, margins, monitoring, surveillance, and/or inspection programs.

7.

An applicant referencing this topical report must describe how flaw acceptance will occur without using fracture toughness.

8.

The NRC staff does not currently accept the use of any known documented creep model in literature for modeling tertiary creep of graphite. The staff does not accept the use of the United Kingdom Atomic Energy Authority (UKAEA) creep model, as it was developed on the irradiation response of Gilsonite.

Therefore, an applicant referencing this topical report will need to develop its own creep model and demonstrate that it adequately models creep behavior for ET-10 graphite. This includes identification of tertiary creep if it occurs and determination of creep coefficients.

9.

An applicant referencing this topical report must demonstrate that the irradiated test data for both basic properties and creep properties bounds the temperature and fluence profiles for the qualification envelope without extrapolation of the data. If this cannot be demonstrated, then the applicant will be required to obtain additional irradiated test data to bound anticipated operating conditions (i.e.,

temperature and fluence combinations).

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Limitations and Conditions

10. An applicant referencing this topical report must demonstrate how the data (irradiated and unirradiated) meet the quality assurance requirements in Section III Division 5 (e.g., HAB-3125, 3127, 3800, and 4000) for graphite qualification for the power reactor design.

11. Dimensional changes of creep samples must be measured and recorded in both the with grain (WG) and against grain (AG) directions, as required by HHA-II-4000, Detailed Requirements for Derivation of the Material Datasheet - Irradiated Material Properties.

12. The following Limitations and Conditions apply to creep modeling for the non-power reactor:

1.

An applicant referencing this topical report must demonstrate that a creep model can be developed for the non-power reactor without using creep data that pre-dates H-451.

2.

Demonstrate that a conservative creep coefficient can be derived from data described in Section 4.3.2.2 of the topical report and show margin to ensure that the graphite components can perform their safety functions.

3.

The proposed creep model is only acceptable because it is limited to applications before turnaround. Additionally, an applicant referencing this topical report must submit the turnaround fluence to the NRC staff for review to confirm that the non-power reactor does not reach turnaround.

4.

Development of a creep model based on the historical data referenced is only acceptable for a non-power reactor.

5.

As stated in Section 4.3.2.2 of the topical report, an applicant must demonstrate that no irradiation-induced stress-driven failure of graphite will occur pre-turnaround.

13. If results of the testing described in Section 5.1.3 of the topical report indicate that there is significant degradation of graphite exposed to the Flibe, then this effect must be accounted for in the design of the graphite reflector.

14. If properties that are not included in this qualification program are needed for the graphite reflector design, an applicant referencing this topical report must perform the necessary testing to obtain properties not included in the qualification program 11