ML22348A122

Transcript of the Advisory Committee on Reactor Safeguards 701st Full Committee Meeting, November 30, 2022, Pages 1-70 (Open)

ML22348A122
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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, November 30, 2022 Work Order No.: NRC-2189 Pages 1-51 NEAL R. GROSS AND CO., INC.

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

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

1 1

2 3

4 DISCLAIMER 5

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

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

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

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

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

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

4 701ST MEETING 5 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 6 (ACRS) 7 + + + + +

8 OPEN SESSION 9 + + + + +

10 WEDNESDAY 11 NOVEMBER 30, 2022 12 + + + + +

13 The Advisory Committee met via Video-14 Teleconference, at 8:30 a.m. EST, Joy L. Rempe, 15 Chairman, presiding.

16 COMMITTEE MEMBERS:

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

2 1 DESIGNATED FEDERAL OFFICIAL:

2 WEIDONG WANG 3

4 ALSO PRESENT:

5 SAMUEL CUADRADO de JESUS, NRR 6 BILL JESSUP, NRR 7 JORDAN HAGAMAN, Kairos Power 8 RACHEL HAIGH, Kairos Power 9 BRANDON HAUGH, Kairos Power 10 RYAN LATTA, Kairos Power 11 GUS MERWIN, Kairos Power 12 NADER SATVAT, Kairos Power 13 JIM TOMPKINS, Kairos Power 14 CHRIS VAN WERT, NRR 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 1 A-G-E-N-D-A 2 PAGE 3 Opening Remarks . . . . . . . . . . . . . . . . . 4 4 Kairos Fuel Qualification Methodology Topical 5 Report 6 Remarks from the Subcommittee Chairman . . 7 7 Presentations and discussion with 8 representatives from the NRC Staff . . . . 35 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

4 1 P R O C E E D I N G S 2 8:30 a.m.

3 CHAIR REMPE: Well, good morning. The 4 meeting will now come to order. This is the second 5 day of the 701st meeting of the Advisory Committee on 6 Reactor Safeguards. I'm Joy Rempe, Chairman of the 7 ACRS. Other members in attendance are Ron Ballinger 8 Vicki Bier, Charles Brown, Vesna Dimitrijevic, Walt 9 Kirchner, Dave Petti, and Matt Sunseri.

10 Member March-Leuba is excused for today, 11 and Member Halnon is not present at this time, but he 12 may be participating intermittently during this 13 meeting. Nevertheless, we do have a quorum. And, 14 similar to yesterday, the Committee is meeting in-15 person and virtually.

16 A communications channel has been opened 17 to allow members of the public to monitor the 18 Committee discussion. Mr. Weidong Wang is the 19 designated federal officer for today's meeting.

20 During today's meeting, the Committee will 21 consider the Kairos Fuel Qualification Methodology 22 Topical Report. And portions of this meeting may be 23 closed as stated in the agenda. After that we'll go 24 back to working on some of our letters that were 25 produced in this meeting.

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5 1 The transcript of the open portions of the 2 meeting is being kept, and it's requested that 3 speakers identify themselves and speak with sufficient 4 clarity and volume so they can be readily heard.

5 Additionally, participants should mute themselves when 6 not speaking.

7 At this time, I'll ask other members if 8 they have any opening remarks, and if not, I'd like to 9 ask Dave Petti to lead us to this topic today, please.

10 MEMBER PETTI: Okay, thank you. I've not 11 received any information, so does NRC management want 12 to say something before we get going?

13 Go ahead, Bill.

14 MR. JESSUP: Okay, thank you, Member 15 Petti, and thank you Chairman Rempe, for the 16 opportunity to present to the Committee this morning.

17 My name is Bill Jessup. I'm chief of the Advanced 18 Reactor Licensing, Branch 1, in the NRC's Office of 19 Nuclear Reactor Regulation.

20 This morning the staff will be providing 21 a brief overview of our review and the safety 22 evaluation for Kairos Topical Report, KPTR 011, Fuel 23 Qualification Methodology for the Kairos Power 24 fluoride salt-cooled high temperature reactor, 25 Revision 2. This will follow a presentation from 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 1 Kairos on this topical report.

2 The Kairos Report presents a series of 3 tests, available data, and surveillance plans used to 4 support qualification of reactor fuel pebbles 5 utilizing TRISO fuel particles and Kairos non-power 6 and power reactor designs.

7 The staff presented on this topic to the 8 ACRS Kairos subcommittee on October 17th. And during 9 that meeting, several important topics relative to the 10 fuel qualification methodology were addressed.

11 The staff's slides today will provide an 12 abbreviated version of the subcommittee presentation 13 with a focus on some of the key issues raised during 14 the subcommittee meeting, including irradiation 15 testing and the potential impacts of salt impurities 16 on the fuel.

17 As mentioned during the October 18 subcommittee meeting, the HERMES test reactor 19 construction permit review is well underway. The 20 topical report we're discussing this morning, and two 21 others that are going to come to the Committee early 22 next year, are referenced in the Hermes application.

23 And finalizing these topical reports will be necessary 24 before the construction permit review can be 25 completed.

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7 1 We're looking forward to this morning's 2 discussion, and are appreciative of the Committee's 3 insights and comments on this very important topic.

4 And with that, I'll turn it back over to you, Member 5 Petti and Chairman Rempe.

6 MEMBER PETTI: Okay. With that, I think, 7 Kairos, are you ready?

8 MR. TOMPKINS: We are ready. Can you hear 9 me?

10 MEMBER PETTI: Not that great, actually, 11 a little bit louder if possible.

12 MR. TOMPKINS: Okay, can you hear me?

13 CHAIR REMPE: Much better, it was a user 14 here in the room.

15 PARTICIPANT: Thank you.

16 MEMBER PETTI: Thank you. Go ahead.

17 MR. TOMPKINS: All right, thanks, David.

18 So my name's Jim Tompkins, Manager of Fuel Licensing 19 at Kairos. With me here in Alameda we have Ryan 20 Latta, who's the principal engineer for fuel 21 qualification, Gus Merwin, who is manager of salt 22 chemistry for Kairos, Nader Satvat, who is our manager 23 of core design, Tim Drzewiecki who, I think, almost 24 all of you know. He's in the room with us as well.

25 He's in the Safety Analysis Group here at Kairos.

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8 1 We're a little scattered today, so I'm 2 going to kind of go through -- I think we have a 3 number of folks calling in. So, Micah, are you on?

4 Sounds like no Micah. How about Brandon, 5 are you on?

6 MR. HAUGH: Yes, I'm on, Jim.

7 MR. TOMPKINS: Okay. You want to just 8 introduce yourself, and title, and everything?

9 MR. HAUGH: Sure. My name is Brandon 10 Haugh. I'm the senior director of Modeling and 11 Simulation at Kairos Power.

12 MR. TOMPKINS: Okay. And we also have 13 Rachel Haigh. She's on in Charlotte. And is anyone 14 else on from Kairos?

15 MR. HAGAMAN: Yeah, Jim, this is Jordan 16 Hagaman, Director of Reliability Engineering and 17 Quality Assurance at Kairos.

18 MR. TOMPKINS: Thanks, Jordan. Anyone 19 else? All right, well, that's the group. I think we 20 can go ahead and get started. So Rachel, you want to, 21 can you go to the first slide?

22 So some of this material we presented.

23 What we've put together is an abbreviated presentation 24 that summarizes the overall methodology. And then 25 we've got some slides discussing a couple of what we 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

9 1 thought were the key issues from the subcommittee 2 meeting.

3 So I'm going to start with this first 4 slide and just go over the definition that we're 5 working to which is qualified fuel is fuel for which 6 there's a reasonable assurance that exists that the 7 fuel fabricated per the specification will perform 8 consistent with the safety analysis. And so I think 9 there's an important consideration there that it is 10 tied to the facility you're putting it into.

11 Fuel qualification methodology is 12 applicable to both test and power reactors. So we 13 tried to write this generally. The qualification is 14 subject to the conditions and limitations described in 15 the topical report and some conditions added by the 16 NRC in their SER. Some of the conditions apply to the 17 power reactor only. And so I just wanted to point 18 that out.

19 We intend to demonstrate qualification met 20 this. The topical is the methodology for 21 qualification. It's not the actual qualification. So 22 we're actively initiating and starting to perform some 23 of our lab testing. The demonstration that the fuel 24 is officially qualified for Hermes, which will 25 obviously come first, will be documented in safety NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

10 1 analysis report documents as part of the licensing, 2 which we're doing initially under Part 50.

3 So with that, I'm going to turn it over to 4 Ryan, and he's going to walk through the -- give you 5 a high level of the methodology and then respond to 6 some of our questions.

7 MR. LATTA: Okay. Ryan Latta speaking for 8 Kairos Power, Fuel Qualification Engineer. I'm first 9 going to give a couple slides that go point by point 10 through sections of the methodology, and then we'll 11 follow that up with a few more slides on some specific 12 questions that were raised in the subcommittee 13 meeting.

14 Okay. So starting with the first section 15 of the report, we discussed the U.S. and international 16 experience with TRISO fuels. There's a wide range of 17 experiences in multiple countries in the use and 18 development of TRISO fuel and different fuel forms.

19 And then there's subsequent use in gas reactors that 20 were their test reactors or demonstration commercial 21 type reactors.

22 This kind of culminates in the U.S. in the 23 initiation of the AGR Program in the early 2000s. We 24 ran the AGR Program to develop a particle design and 25 perform the radiation and safety testing to qualify NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

11 1 that fuel system. The AGR 1 and AGR 2 tests were 2 written up into a topical report written by EPRI. And 3 that was reviewed by the NRC and issued an SER.

4 And Kairos leverages this AGR particle 5 design and the data used in the AGR 1 and 2 in this 6 issued SER and TR, topical report, for our application 7 in an FHR, okay.

8 That section of the report is the Kairos 9 Power fuel element PIRT. And so Kairos Power 10 performed a fuel PIRT exercise with the goal of 11 looking at the figure of merit where the figure of 12 merit was fission product transport and release from 13 the fuel under different conditions of normal 14 operation and accidents in our application to an 15 AP-FHR.

16 In doing this, we identified over 200 17 phenomena related to fuel performance and then 18 identified the high importance phenomenon for further 19 investigation. These were high importance levels and 20 low -- medium to low mileage levels. And that kind of 21 forms a lot of the basis of the qualification 22 methodology, and specifically the pebble laboratory 23 test section that I'll talk about later.

24 Okay. Next section is on the fuel 25 specification, manufacturing, and quality control NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

12 1 through inspection. So as I previously said, Kairos 2 leverages the AGR particle design. We have a fuel 3 specification that's equivalent to what was used in 4 the AGR Program.

5 Currently we're developing TRISO 6 manufacturing and annular fuel pebble development in 7 an in-house program to produce a quality commercial 8 product. Product that is produced goes through a 9 quality control process where inspection is used to 10 ensure that the fuel specification is met. The fuel 11 indeed does meet the product specification equivalent 12 to the AGR Program. And in forming that 13 characterization, we demonstrate that quality is 14 maintained.

15 Okay, next section is the fuel 16 qualification envelope. So as I previously said we're 17 leveraging the AGR Program, and this defines our fuel 18 qualification envelope. Specifically in this case, 19 we're leveraging AGR 2 that was documented in the EPRI 20 TRISO topical report. And so the fuel qualification 21 envelope considers irradiation test conditions and 22 transient conditions.

23 There are four key parameters for normal 24 operation. These are power, temperature, burn-up, and 25 fluence. And the initial reactor has to operate NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

13 1 within this envelope for steady state conditions and 2 without needing additional irradiation test data 3 outside of that -- if you're going to operate outside 4 of that test data within the commercial reactor, then 5 you need additional irradiation testing to meet the 6 new envelope.

7 Additionally, there are temperature limits 8 for transient conditions, and also noting that there 9 are significant margins in the temperature regime 10 which AGR was tested. Tests were conducted versus the 11 KB-FHR designs for both the test and power reactor.

12 Next slide, please. Okay, the next 13 section of the report is on pebble laboratory testing.

14 And so this test program came out of the findings of 15 the PIRT. The high priority items identified were to 16 be investigated in this test program with the goal of 17 demonstrating that the pebbles and particles meet 18 function requirements, that there's no physical damage 19 or interaction of particles with FLiBe.

20 And so there are two categories of testing 21 that are being worked on. The first category is 22 mechanical test of the pebble. The second category is 23 material compatibility testing of the pebble.

24 The prescribed mechanical tests are pebble 25 compression, pebble impact, tribology, which is wear NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

14 1 behavior, and then molten salt infiltration behavior.

2 The material compatibility tests are interactions of 3 the pebble with FLiBe or with air. And then for each 4 of these specific tests, acceptance criterias were 5 defined within the topical report.

6 The next section, fuel irradiation 7 qualification testing, so if you, as I previously 8 described, if you are outside of the fuel 9 qualification envelope, it requires a fuel irradiation 10 test. The test that's proposed is very similar to the 11 AGR type of irradiation tests that were performed in 12 the AGR.

13 We would use our TRISO fuel particles, a 14 statistically significant number of them in our 15 annular fuel pebble design. And then we would perform 16 an irradiation test at the bounds of the commercial 17 reactor to extend the bounds of the qualification 18 envelope.

19 Fission product gas monitoring would be 20 performed during the test to understand the failure 21 fraction of fuel in the test. And then after the 22 test, there would be PIE performed to confirm the 23 failure fraction and the behavior of the fuel.

24 MEMBER KIRCHNER: This is Walt Kirchner, 25 just a clarification. So you're just talking about NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

15 1 fuel particles, not fuel particles in a pebble?

2 MR. LATTA: No, these would be fuel 3 particles in our annular fuel pebble design, so it 4 would be in our annular pebble, the Kairos pebble. So 5 they would be inside the pebble.

6 MEMBER KIRCHNER: Okay, thank you.

7 MEMBER PETTI: And, Walt, because this is 8 for the bigger reactor.

9 MEMBER KIRCHNER: Yeah.

10 (Simultaneous speaking.)

11 MEMBER PETTI: Not for Hermes, right?

12 MR. LATTA: Yes, that's correct. Okay, 13 that section is on fuel performance modeling. This 14 section, for information, right, the description of 15 models related to fuel that Kairos is using, the main 16 focus is on KP-BISON which is the subject of a 17 previous topical report where an SER was -- where the 18 topical report is reviewed and an SER issued.

19 The KP-BISON would be validated to IAEA, 20 and AGR data, and eventually to Kairos-produced 21 irradiation test data. And this tool has been used 22 for core design and source term analysis.

23 There's additional description of DEM and 24 FEM models that are used to understand the flow 25 behavior of pebbles to the core, wear, behavior, and 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 1 loads in the core, and along with mechanical behavior 2 of the pebble.

3 Next section of the report is the 4 in-service surveillance program --

5 MEMBER PETTI: Just to go back a question 6 on the performance model.

7 MR. LATTA: Yes.

8 MEMBER PETTI: You plan on running the 9 test predictions of this irradiation that's in the 10 second bullet and then also sort of a post-test --

11 MR. LATTA: Yeah, yeah.

12 MEMBER PETTI: -- sort of thing?

13 MR. LATTA: Yeah, you know, for designing 14 an irradiation test, we'll certainly be modeling it 15 before we conduct the test. Yeah.

16 MEMBER PETTI: Thank you.

17 MR. LATTA: Okay. Speaking to Field 18 Surveillance program, so once there's a test reactor, 19 a commercial reactor, in those reactors there would be 20 a surveillance program for the fuel to confirm fuel 21 performance in the operating environment.

22 In this case, the surveillance program has 23 three parts. The first part is fission product 24 monitoring in the cover gas and FLiBe coolant for 25 radioactivity. There's a circulating limit that's 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 1 allowable for the reactors.

2 Next part is the pebble inspection. So 3 pebbles traverse the core and are reinserted into the 4 core. As you saw, the pebbles exit the core, they are 5 inspected for physical damage along with the burn-up 6 being measured over their lifetime.

7 The third part of fuel surveillance is 8 destructive PIE. And so pebbles that have reached 9 their equilibrium would be extracted from the core 10 through the pebble handling system. And they'd be 11 sent to hot cells where PIE would be performed on test 12 reactor pebbles and pebbles from the initial power 13 reactor. And the objective there is to confirm fuel 14 performance of the fuel in its application.

15 MEMBER PETTI: Just a question for 16 clarification. I didn't think, based on previous 17 discussions that we've had, that you'd actually ever 18 get to equilibrium in Hermes in a pebble. So, that 19 would only be pebbles in the power KB-FHR?

20 MR. LATTA: The maximum burnup would be 21 much slower in the Hermes.

22 MEMBER PETTI: Right. So you can't 23 monitor your PIE on a pebble that had reached 24 equilibrium burn-up until you're downstream in with 25 the --

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18 1 MR. LATTA: It would be the --

2 MR. SATVAT: Yeah, this is Nader for core 3 design. Basically, the maximum burn-up that is 4 achievable in Hermes, based on the full lifetime of 5 Hermes, there is a possibility of achieving 6 equilibrium. But because of capacity factors, it 7 might not happen.

8 MR. LATTA: So it would be the maximum 9 burn-up in Hermes which may or may not be the 10 equilibrium for Hermes.

11 MEMBER PETTI: Right, okay. Thanks, that 12 helps.

13 MR. LATTA: Yes, thank you.

14 Okay, next slide, please. So that was a 15 summary of the fuel qualification methodology. The 16 next few slides go in to address a few questions, 17 specific questions from the previous subcommittee 18 meeting.

19 These two questions, the first was related 20 to the presence of transition metals in FLiBe and 21 their effect on the sodium carbide layer. Second 22 question was related to pebble irradiation program and 23 irradiation testing for the Hermes test reactor. So 24 in the next couple of slides, I'll go through those, 25 address these questions in some more detail.

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19 1 Okay, first slide here says relates to the 2 presence of transition metals in FLiBe. So we're 3 conducting laboratory testing of the pebbles in FLiBe 4 at temperature and pressure, and looking at pressure 5 thresholds for infiltration of FLiBe, and we're 6 precluding infiltration by design in the fuel so that 7 FLiBe will not reach the fuel region of the pebble.

8 For any kind of mechanism to occur here, 9 the FLiBe would have to infiltrate into the fuel 10 region, and this would have to bring the transition 11 metal fluorides in contact with the TRISO particle.

12 Additionally, the OPIC layer separates the 13 SiC layer from the free surface of the OPIC. So you 14 have to go through the OPIC, the metal fluorides would 15 have to transmit through the OPIC. So you would have 16 to have a failed OPIC contact between the salt and the 17 sodium carbide.

18 The previous meeting, I brought up about 19 AGR-567 where Capsule 1 had a significant amount of 20 failures due to nickel ingressing into the fuel and 21 damaging the particles. That's performed at a 22 significantly higher temperature than KB-FHR fuel 23 operates at. It's at least 500 degrees temperature 24 difference or more higher in the AGR test.

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

20 1 amount of nickel in the AGR irradiation. There was an 2 Inconel nickel-based alloy sheath covered a niobium 3 sleeve where it is believed that the two components, 4 nickel and niobium, formed a low melting point 5 eutectic. And this helped to transport nickel through 6 the system resulting in failures. Whereas in our case 7 we have transition metal fluorides in salt.

8 So because of these low temperatures and 9 difference in the system, due to these detrimental 10 effects were active, we expect them to progress very 11 slowly. And in the instance of TRISO failures, we are 12 monitoring fission gas products in the gas space and 13 the coolant spaces of the reactor. And there's a 14 circulating activity limit that's a technical 15 specification for the reactor. And this really 16 ensures the safety of the system.

17 MEMBER PETTI: So let me -- there's a lot 18 on the exhibit I don't understand. We have a 19 different understanding of the system. I'm not 20 worried about transition metal fluorides. If you're 21 doing redox control you will have elemental transition 22 metal because of the redox state. Those metals, even 23 though it doesn't fully wet a pebble, they will be in 24 contact and can get into the pebble.

25 It doesn't have to get into the TRISO NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

21 1 particle, it just has to get into the matrix. There's 2 old data from General Atomics where they introduced 3 iron from their furnace that fell into their 4 compacting equipment. And a little bit of iron got in 5 and attacked.

6 Second, you've seen the letter, the draft 7 letter. There are references to show that transition 8 metals will react with silicon carbide much more 9 quickly. There's 500 degrees C lower. That's 10 irrelevant. There's data out there from diffusion 11 experiments to show that if you can get the material 12 to the silicon carbide layer, even at lower 13 temperatures, that you will start to get the corrosion 14 to occur.

15 Now, so the question is, can you get it 16 there? That's the big issue.

17 MR. LATTA: Right.

18 MEMBER PETTI: And I would argue that 19 there's so little experience in this new first of a 20 kind system that that's an issue that should be 21 thought about.

22 MR. TOMPKINS: Let me just respond, first 23 by saying that, yeah, we agree that the, you know, 24 even at lower temperatures it's still going to be a 25 problem. But our understanding is that it would be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

22 1 slower. But the real protection is making sure the 2 salt doesn't get there in the first place. That's 3 really what we're trying to design out of the system.

4 And I don't know --

5 MEMBER PETTI: So again, I have this 6 mental problem, because I read a topical report that 7 said that the tritium is going to get all into the 8 graphite. We're going to mass transport all the 9 tritium that's produced in the FLiBe and get into the 10 graphite. But we're not going to get any of these 11 metallic elements that are in the salt to the surface 12 of the graphite.

13 They're going to pretty much get there by 14 the same mechanism which is mass transport in the 15 liquid. So again, I'm having trouble with the physics 16 in trying to put the whole picture together.

17 MR. MERWIN: This is Gus Merwin from salt 18 chemistry. I'll take maybe two small points. If 19 redox control is implemented, it'll be implemented in 20 the chemistry control system which is separate from 21 the reactor core as well as the primary heat transport 22 system. And so the making of metallic particles would 23 be physically separated from the fuel region of the 24 core. And then that --

25 MEMBER PETTI: What does that mean? I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

23 1 don't understand what you're talking about. If you 2 set the redox, you set the equilibrium condition in 3 the entire coolant system. You agreed to do it, 4 that's fine that you're doing it outside the core, 5 that's an easy place to do it. It makes sense. But 6 whatever you do, you set that chemical equilibrium 7 across the entire system. Otherwise, it wouldn't 8 work.

9 MR. MERWIN: I agree. The goal of redox's 10 potential is it's going to keep those transition 11 metals in a metallic form which would not bring them 12 into the reactor coolant. They would stay in the 13 element.

14 MEMBER PETTI: But they're coming in off 15 the walls, all the surfaces.

16 MR. MERWIN: Which would make them 17 fluorides. They'd be in an oxidation process.

18 MEMBER PETTI: And then they would be 19 reduced to elemental because of the redox condition.

20 MR. MERWIN: I don't believe that they 21 would first oxidize and then reduce in the salt. If 22 the system's at equilibrium, there would be either a 23 driving force to oxidize them or a driving force to 24 reduce them. Having both of them in parallel doesn't 25 make sense to me.

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24 1 MEMBER BALLINGER: Have you folks produced 2 what amounts to a PORV diagram for this system.

3 MR. MERWIN: Yes, but we are not crediting 4 that in this fuel performance topical.

5 MEMBER BALLINGER: That's where they would 6 find a few and be able to define the conditions, the 7 electrochemical conditions, so potentially the system.

8 And you could -- that's where they map the various 9 species.

10 MEMBER BALLINGER: Correct --

11 MEMBER PETTI: There will always be an 12 equilibrium between the oxide and the metal. And if 13 you're doing redox control, the oxide should be very 14 low, right?

15 MEMBER BALLINGER: And you have to know 16 where the potential actually is with respect to --

17 MEMBER PETTI: And if they do what they're 18 going to do, which again, I don't want to get into 19 details, the way they're going to control the redox, 20 you keep it fairly low. So they should be elemental.

21 But those elements, it's coming off all 22 the metal. That's why there's a lifetime on the 23 vessel. Go ahead, keep going.

24 MR. LATTA: Okay. We can move to the next 25 slide if there's no more comment.

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25 1 Okay? The next two slides talk to these 2 --

3 COURT REPORTER: Just a friendly reminder 4 from the court reporter to identify yourself as you 5 speak.

6 MR. LATTA: Okay. This is Ryan Latta 7 speaking. The next couple of slides talk to the issue 8 you brought up about elutriation testing for the test 9 reactor, some technical discussion and discussion of 10 the licensing of a test reactor.

11 So this first slide, fuel causation 12 methodology ensures the reasonable assurance and 13 demonstrates that through the test program that's 14 proposed. Additionally, in this reactor, there's the 15 additional barrier in the core of having FLiBe present 16 as an additional and separate barrier for the release 17 of fission products.

18 And that mitigates safety concerns within 19 the reactor itself. The AGR Program extensively tests 20 radiation tested TRISO particles, and that defines our 21 qualification envelope.

22 Kairos, as I've discussed, leverages the 23 TRISO particle design and ensures, through 24 manufacturing and inspection, that a high quality fuel 25 form is produced. And that is in compliance with the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

26 1 fuel specification for this particle type.

2 Speaking to the test reactor itself, 3 there's a defense-in-depth philosophy here within the 4 core, use of TRISO particles plus five coolants, 5 previous discussion of different gas reactors operated 6 at higher normal operating and accident temperatures, 7 whereas these FHR temperatures and accidents in normal 8 operations are on the lower end. The combination of 9 these diverse and defense-in-depth approaches ensure 10 the safety of the reactor.

11 Additionally, in the case of fuel failure, 12 surveillance is being performed, activity is monitored 13 in the cover gas space and in the coolant spaces on 14 the reactor. And there's a circulating limit on 15 maximum allowable activity that will affect operations 16 as it's approached. Because of this, it represents no 17 challenge to the public health and safety.

18 Next slide, please.

19 MEMBER KIRCHNER: Excuse me.

20 (Simultaneous speaking.)

21 MEMBER KIRCHNER: This is Walt Kirchner.

22 Oh, sorry, Dennis, go ahead.

23 MEMBER BLEY: Okay, thanks. I've been 24 stewing over that last discussion, Dave, and Ron, and 25 you folks from Kairos' discussion. The PORV diagram, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

27 1 and showing where you live on that, and the different 2 processes ought to be helpful. You said -- Kairos 3 says they have one. But they don't think they need it 4 here. We seem to have a difference of opinion which 5 perhaps that would help.

6 Is that something you could share in a 7 closed session? And, Dave, I wonder if that would 8 help from your point of view?

9 MEMBER PETTI: I think I know what Ron was 10 asking for. I mean, have it in my head.

11 MEMBER BLEY: I mean, you've got the PORV 12 diagram in your head is what it sounds like.

13 MEMBER PETTI: Yes.

14 (Laughter.)

15 MR. MERWIN: This is Gus Merwin, manager 16 of salt chemistry. We can talk in more detail in the 17 closed session. There is boundary limits for redox 18 control that are stated as part of source term topical 19 that limit the, at least on the fluoride scale, the 20 redox potential of the salt.

21 But we are intentionally not crediting it 22 for fuel performance strictly because we do not 23 believe that salt chemistry is related to fuel 24 performance, because interaction of the salt liquid 25 with the TRISO is precluded by design.

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28 1 So the chemistry control system and how 2 we operate the salt chemistry, in our opinion, I don't 3 want to be to bold here, but it's not related to TRISO 4 performance. That's in the boundary of the statements 5 in the topical.

6 MEMBER BLEY: Well, I kind of got that was 7 your position, but it might help.

8 PARTICIPANT: Certainly an added 9 supporting thing though.

10 MR. MERWIN: Certainly.

11 MR. TOMPKINS: Well, could we provide more 12 discussion in a closed session, Gus? Do you have --

13 MR. MERWIN: Certainly.

14 MR. TOMPKINS: Okay, all right. Maybe 15 that's something we do in the closed session.

16 MR. LATTA: Okay. Ryan Latta speaking 17 again. So this is our final slide. So the Hermes 18 test reactor provides important confirmation of the 19 FHR technology and supported deploying our commercial 20 reactor. The Hermes reactor is a full integral test 21 of Kairos fuel for the application in the power 22 reactor.

23 And in looking at the Atomic Energy Act, 24 licensing of test reactors, there is significant 25 latitude related to the licensing of test reactors.

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29 1 I'll just read the first quote here, but it says in 2 issuing licenses under the subsection of the AEA, the 3 Commission shall impose the minimum amount of such 4 regulations to fulfill its obligations under the act.

5 And so in conclusion, there's been 6 extensive testing of TRISO fuel under the DOE AGR 7 Program along with Kairos Power's laboratory test 8 program of the fuel pebble form and its manufacturing 9 programs.

10 And this also, in addition to the defense-11 in-depth and diverse safety of the FHRs and retention 12 of radionuclides, cites the TRISO fuel, combination of 13 the TRISO fuel with the five coolants and the 14 monitoring of fuel, provides the reasonable assurance 15 of the protection of public health and safety which is 16 consistent with the AEA.

17 When considering this project as a whole 18 and its application to the FHR, we're able to 19 demonstrate that we meet the public health and safety 20 consistent with the Atomic Energy Act.

21 MEMBER KIRCHNER: This is Walt Kirchner.

22 Let me just understand what you're saying here. So 23 Hermes is part of your fuel qualification methodology 24 AGR then? And the testing in Hermes will be the 25 qualification of your fuel --

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30 1 MR. TOMPKINS: No.

2 MEMBER KIRCHNER: -- for reactor 3 application.

4 MR. TOMPKINS: No, actually not. The 5 testing for the power reactor will probably be done in 6 an oxide test facility like a patent or something like 7 that. Because we're trying to expand the 8 qualification envelope. We need it to expand the 9 qualification envelope for the power reactor.

10 But, you know, I -- this is James 11 Tompkins, sorry about that. But clearly, we're going 12 to, you know, we're going to look at what happened in 13 Hermes, and we're going to factor that. That'll be 14 part of the qualification, in a sense.

15 But it's not directly tied to it. I mean, 16 and part of the reason for that is that we might 17 decide at some point we're not going to it in Hermes.

18 I mean, I can't guarantee that we're going to go over.

19 I mean, we plan to. So we need a way to expand that 20 envelope so we would do that testing, most likely in 21 an outside facility. That answer your question, Walt?

22 MEMBER KIRCHNER: Yes, part way. Can you 23 go back to the previous slide?

24 MR. TOMPKINS: Okay.

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

31 1 irradiation testing was done for all HTGRs wasn't the 2 temperature. It was to qualify the fuel, because the 3 whole argument is that this is functional containment.

4 And you had to take production scale fuel and test it, 5 and irradiate it to demonstrate that the finished 6 product didn't have defects from the manufacturing 7 process.

8 Let me ask a few other questions. Who's 9 going to make your fuel?

10 MR. TOMPKINS: I think, ha, ha, I don't 11 want to --

12 MEMBER KIRCHNER: And a manufacturing spec 13 process is, this is, you know, operating these coating 14 machines at scale is something of a black art.

15 MR. TOMPKINS: Yeah.

16 MEMBER KIRCHNER: And one needs to have a 17 lot of trial and error before you get to the quality 18 that's required from the EPRI spec.

19 MR. TOMPKINS: I don't think we can 20 announce who's making our fuel yet. But I will say 21 that we've expended significant resources in the last 22 year or so making pebbles, and also testing how to 23 make particles. And so that's underway.

24 MR. LATTA: And also through the ARDP we 25 worked with the National Laboratories through CRADAs 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 1 with Oak Ridge and INL.

2 MEMBER KIRCHNER: Well, my point's a 3 subtle one. It's not until you actually, whether you 4 make it or you contract for someone to make the fuel, 5 you've got to stand up that production line and make 6 significant quantities of fuel and test it before you 7 have confidence that you've got a product that you can 8 actually put in the reactor. And I'm assuming that's 9 part of the Hermes demonstration.

10 MR. MERWIN: Yeah, and that's part of what 11 Ryan talked about, the pebble development process that 12 we're doing where, as we make pebbles, and we make 13 particles, we learn from that. And we've already made 14 some adjustments that were discussed at the last 15 meeting.

16 For example, we found in making pebbles 17 that the pressures were too high. And we were 18 breaking, you know, we were causing breakage. And so 19 we revised the process to reduce the pebbles, or to 20 reduce the suppressing pressure.

21 MR. LATTA: Yeah, so this is Ryan Latta 22 speaking. So in the development program there's, you 23 know, there's extensive characterization of the fuel 24 post fabrication, you know, use of the big 25 consolidated leach-burn-leach process, use of other NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

33 1 characterization techniques to inspect the TRISO 2 particles after they've been incorporated into a fuel 3 form.

4 Additionally, in talking to defense in 5 depth here and the difference between -- with gas 6 reactors, you know, in this core we also have FLiBe as 7 a containment. And it was just pointing out that 8 temperatures are low in an FHR which, you know, reduce 9 the transport of fission products. And these are 10 additional barriers of safety that are not present in 11 other reactors that have been licensed with TRISO 12 fuel.

13 MR. TOMPKINS: And by the way, we know 14 who's going to make our fuel. I don't think we've, 15 you know, officially announced it yet. So that's why 16 I'm hesitant to say.

17 MEMBER KIRCHNER: Thank you.

18 MR. LATTA: Are there questions?

19 MEMBER PETTI: Yeah. So what I'm 20 struggling with, and members, I need help here, is 21 that this is new information that's not in any of the 22 written documentation. And I was told once by senior 23 ACRS members that this is nice. But we have to go by 24 the written record.

25 This is very helpful. I mean, I expected 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

34 1 the last slide that did say, because of the test 2 reactor, they got a light touch. That's not written 3 down anywhere. But that, they're saying that. It's 4 not in the SE. It's not in the topical report. And 5 so it is this missing context in my opinion.

6 And just read the topical report because, 7 A, because it's time to do both, it's time to do it 8 for the power reactor and for Hermes. But some of 9 this would be, if it was in the written documentation, 10 would help put more context around this.

11 CHAIR REMPE: And, again, the latest 12 version of a draft letter that I've seen basically 13 points out that the draft SE needs some enhancement 14 before it should be issued. And we may want to change 15 some of this. But again, I mean, that's where we're 16 at on what should be said. Because, again, if there's 17 also discussion about the chemistry and to go like 18 that, that needs to be documented.

19 MEMBER PETTI: Okay. Any other comments, 20 members?

21 MEMBER KIRCHNER: Can we see the last 22 slide again? I'm just saying, so the intention is, 23 going forward, Kairos will do pebble testing in 24 another reactor to get up to the temperatures and 25 exposure that you would see for an actual power NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

35 1 reactors.

2 MEMBER PETTI: Right.

3 (Simultaneous speaking.)

4 MEMBER PETTI: Yes.

5 MEMBER KIRCHNER: Yeah, okay.

6 MEMBER PETTI: You know, historically, in 7 TRISO irradiation, your radiation comes as two 8 functions. One is performance. The other is 9 confirmation of manufacture. Because the spec 10 historically has been viewed as never being 11 absolutely, 100 percent, you know, perfect, just 12 because of the history of TRISO fuel. So they're 13 separate here. And that's the subtlety.

14 Any other questions, members? If not, I 15 guess we can turn to staff.

16 MR. CUADRADO: Yeah, this is Samuel 17 Cuadrado from the staff. I'll be running the slides 18 for the staff.

19 MEMBER PETTI: Okay. Give us a minute.

20 MR. CUADRADO: Okay.

21 MEMBER PETTI: They're getting up to the 22 front table here.

23 MR. CUADRADO: All right.

24 MR. VAN WERT: Good morning, my name is 25 Chris Van Wert. I'm staff, and I will be presenting 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 1 our review on the Kairos Power Topical Report, 2 KP-TR-011, field qualification methodology for the 3 Kairos Power fluoride salt-cooled, high temperature 4 reactor.

5 Next slide please. So Kairos requested 6 staff review approval of the topical report. And as 7 mentioned this morning, it covers both the power and 8 the non-power versions of the KP-FHR. The staff's 9 review focused on the overall fuel qualification 10 framework, which includes but is not limited to the 11 use of existing data, surveillance, unirradiated 12 testing, and irradiation testing.

13 All right. And next slide, please. I 14 keep trying to advance the slides myself. I 15 apologize. So just quickly, the regulatory basis here 16 is the same slide as from the subcommittee meeting.

17 We cover 50.34(a) and (b), 50.43(e), as well as 10 CFR 18 111, additionally, PDCs 10 and 16 which were 19 previously approved in a PDC topical report for the 20 basis as well.

21 Next slide, please. The Kairos fuel 22 qualification topical report builds heavily upon 23 existing data, namely the EPRI topical report which 24 provided fuel qualification for the particle level for 25 TRISO particles from the AGR-1 and 2 program. In NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

37 1 addition to that, existing data regarding carbon 2 matrix property data is used to inform their testing 3 matrix. The staff reviewed the data that they were 4 using and confirmed that it was applicable to given 5 the operating conditions for the Kairos reactor 6 design.

7 As in Section 39 of the topical report, 8 they present the fuel surveillance plans for the fuel 9 qualification. This includes cover gas monitoring, 10 un-destructive examinations, and planned destructive 11 examinations. And the staff found that these were 12 acceptable for monitoring fuel performance and 13 detecting particle failure.

14 Next slide, please. Section 3.6 of the 15 topical report covered planned fuel pebble laboratory 16 tests. And these included mechanical, tribology, 17 buoyancy, salt infiltration, and material 18 compatibility testing.

19 The staff reviewed the test plans and 20 confirmed or determined that they were acceptable for 21 use for determining the pebble conditions. And this 22 is based on the sort of test conditions that were 23 going to be used of un-radiated tests in consideration 24 with the planned operating conditions.

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

38 1 talk a little bit more on this, this follows from 2 this morning, but the Kairos plan is to include 3 radiation in a gas environment, purge gas monitoring 4 for fission gas, and also post-irradiation 5 examinations. This was presented in 3.7 of the 6 topical report.

7 And the testing methods that were used 8 were similar to the ones used for the EPRI TRISO 9 particle topical report and the non-destructive PIEs 10 which include looking for damage to the fuel pebbles, 11 as they go through the EHSS. That would help 12 determine if there was a manufacturing flaw which 13 would lead to damage to the pebbles as it circulated 14 around.

15 And then the post-radiation examination 16 includes the consolidated leach-burn-leach 17 investigations to determine, or to confirm the 18 particle fraction, failure fraction.

19 The staff reviewed the irradiation testing 20 plans as presented in Section 3.7 of the topical 21 report, and noticed again that it closely follows 22 previously accepted testing conditions and methods and 23 that it's acceptable for the purposes that Kairos laid 24 out.

25 Next slide, please.

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39 1 MEMBER KIRCHNER: Just a minor --

2 MR. VAN WERT: Yes.

3 MEMBER KIRCHNER: -- Chris. Looking ahead 4 to the power reactors, and you would either use the 5 results from Hermes to demonstrate the compatibility 6 with FLiBe under the irradiation environment. I mean, 7 irradiation and gas for a gas cooled reactor which is 8 going to be cooled with helium --

9 MR. VAN WERT: Right.

10 MEMBER KIRCHNER: That's, you know, it's 11 an inert gas. So that's a lot different than being in 12 a FLiBe environment.

13 MR. VAN WERT: So I think we heard this 14 morning from, I believe, from Jim Tompkins who was 15 answering a related question. If they have results 16 from Hermes, they'll obviously use that for informing 17 their process and informing their decisions on the 18 power reactor.

19 However, they are running pebble tests in 20 the patent type of reactor. I don't think they've 21 decided on where, but that will support their power 22 reactor. So they will have that data too. So it's 23 not completely necessary, but obviously they will be 24 using it, and they will have that at their hand as 25 long as Hermes is built and operated.

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40 1 Next slide, please. Oh, yeah. All right, 2 so based on conversations that we had at the 3 subcommittee meeting and in further conversations with 4 Kairos, of course, we went wanted to add this 5 discussion as well.

6 You heard the physical description this 7 morning in the Kairos presentation that the staff was 8 looking at the possible sources of impurities, you 9 know, corrosion products or LNL, iron, chromium, 10 nickel, that can be present.

11 You know, the staff's review, of course, 12 is focused on not only the transport mechanism that 13 would potentially lead to these TRISO particles being 14 attacked by these products, but also how would this 15 work overall from a, or how would it be viewed from a 16 safety standpoint?

17 Are we reaching that reasonable assurance 18 of safety for the public and the environment? And so 19 we're looking at the transport mechanism, but we're 20 also looking at how this would play out with the 21 reactor.

22 And so, you know, as you heard this 23 morning they have the chemistry control system which 24 will help minimize the amount of the corrosion 25 products or elemental articles in the molten salt. If NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

41 1 it were to be transported, you know, they have their 2 testing to show that the salt is not going to be 3 infiltrating down to the fuel layer.

4 They also have, you know, the level of 5 assurance when they're investigating the pebbles as 6 they go around to ensure that there's no damaged fuel 7 beyond the specifications that they include, their 8 criteria for damaged pebbles.

9 So with this in mind, the salt should not 10 be reaching the fuel layer. The overall system would 11 also detect any particles that did become compromised 12 through the cover gas monitoring system as well.

13 So with the entirety of that combined, so 14 the difficulty in the transport mechanism along with 15 the ability to detect damaged particles, sorry, 16 damaged pebbles, as well as, you know, any early 17 failures that were to occur, the staff found that 18 reasonable assurance was reached in terms of public 19 health and safety. Any questions?

20 MEMBER PETTI: If they could have an 21 indication from the gas monitoring that a pebble 22 somewhere is involved, but you don't know which one it 23 is --

24 MR. VAN WERT: Right.

25 MEMBER PETTI: -- and you will not know NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com

42 1 which one it is even when you to run it through the 2 pebble monitoring system, right, you'll not do that.

3 It's not an issue, in my opinion, on 4 solubility limits. They're not going to be 5 precipitating metals stock. But, you know, real 6 engineered system, not a perfect laboratory, 100 ppm 7 of some of these materials could be quite reasonable.

8 And my mental picture, and again, I could 9 be wrong, is anything being done outside the core is 10 a little too late in terms of filtering. Because that 11 graphite is huge filter. I mean, you know, graphite 12 combination materials are used all over the place as 13 filters, right.

14 And I'm pushing all this salt through.

15 And again, it doesn't have to get into the fuel layer.

16 That pebble is a very porous layer. It just has to 17 get to the surface, and it'll start migrating down the 18 surface.

19 You know, that's the concern. And again, 20 I said this in the subcommittee, if you take two 21 technologies, and you bring them together, you don't 22 bring just the good. You also potentially bring some 23 negatives. And you've got to think in the negative 24 space. And that's what struck me, was that I didn't 25 even see it.

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43 1 Talk about acknowledge, there's references 2 in the draft letter, this has been studied for 3 electronics, actually. And it's more simple. They 4 put iron, chromium, and nickel up against silicon 5 carbide. And even at 600 degrees, it moves really 6 quickly to calculate through 35 methods. So, you 7 know, it's not purely a high temperature, you know. It 8 can happen at low temperature.

9 CHAIR REMPE: Once you go on, I mean, 10 listening to this, the subcommittee meeting and today, 11 and I'm looking through the 11-page draft SE, do you 12 think maybe it needs to be beefed up a bit in some of 13 the discussion based upon, I mean, I'm seeing some 14 more discussion in your slides than what we saw in the 15 subcommittee. Are you guys in agreement, yeah, we 16 probably need to revise the SE and add a bit more 17 detail?

18 MR. VAN WERT: I mean, that's something 19 that we can definitely investigate. And if you're 20 talking about the SE, I think that's easier for the 21 staff to do. I don't know if -- and I'm looking over 22 at Billy a little bit here, but the current state on 23 that, we can open up the SE, correct, and make 24 adjustments if necessary here.

25 PARTICIPANT: I tend to agree with that.

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44 1 CHAIR REMPE: Thank you.

2 MEMBER PETTI: My concern, I mean, look at 3 this at 100,000 feet. Take Kairos out of it. You've 4 got a new fuel flow. I'm sorry, go read the EPRI 5 topical report. All it says is the particles are 6 good. It doesn't say anything about the fuel element.

7 And it says you have to qualify that yourself, each 8 vendor, right.

9 At 100,00 feet, I've got a reactor, I'm 10 going to put this fuel in with a novel coolant, and 11 we're not actually ever going to see neutrons before 12 the thing is actually operated. That precedent is 13 what bothers me, because there's others out there 14 whose fuels are nowhere near as mature this, 15 potentially.

16 That's the other concern I have in the 17 back of my mind, is that there's not enough guardrails 18 in the SE to kind of say why you went down this road.

19 So it doesn't look like it's a precedent for 20 everybody, because of the importance in fuel.

21 MR. VAN WERT: And I definitely understand 22 that, and I think maybe it's something you touched on 23 earlier, I think. Also it's something maybe I should 24 have been more clear in the SE. It was the separation 25 between Hermes and full power.

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45 1 So yeah, if another full power came in 2 and wanted to jump straight to this, that would be 3 different. And we are talking about Hermes here. So 4 the purpose of the Hermes reactor is, to some extent, 5 proved a concept. It's also to provide data, you 6 know, for Kairos to use.

7 And so our approval is specific to this.

8 They will be running their separate tests for the 9 power reactor as well. So I do think we have to kind 10 of keep that in our mind. They're running the best 11 integral testing you could ever do. You know, they're 12 building a one-third scale reactor. They will be 13 getting the data.

14 I understand that it would be great to 15 know everything before we build it, but I think we 16 have to consider the safety impacts. So we have a 17 good feeling that the fuel, a very good feeling that 18 the fuel will not have these failures to begin with.

19 And then if you look at the rest of the, 20 you know, the Hermes design, I think that that's the 21 purpose of the test reactor, is to get this 22 information.

23 MEMBER KIRCHNER: That was the problem I'm 24 having is like Dave. Conceptually, I mean, Kairos 25 should be lauded for what they're doing. And one 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

46 1 would hope that other advanced reactor concepts would 2 also build what I'll call a prototype.

3 And I just -- it would seem to me that 4 then the Hermes is an integral part of the fuel 5 qualification methodology. Or if you accept the 6 methodology without explicit reference to Hermes or a 7 follow-on power reactor, then your limitations and 8 conditions are subject to demonstration of integral 9 fuel performance in Hermes. You see where I'm going 10 logically?

11 MEMBER SUNSERI: Like Dave, yeah. This is 12 -- it kind of sets a precedent. I think what Kairos 13 is doing, personally, one person's opinion, I missed 14 the subcommittee meeting, it's laudatory that they're 15 building a prototype.

16 MR. VAN WERT: Right.

17 MEMBER SUNSERI: And they can test out 18 things like quality issues of taking a novel coolant 19 and mixing it with the pebble TRISO fuel technology.

20 MEMBER KIRCHNER: Yeah. Well, we'll let 21 you go. And when you get to the conclusion, this 22 somehow seems like that should be explicit in the SE, 23 that this Hermes, in effect, is the fuel quality --

24 MEMBER PETTI: Is a part of it.

25 MEMBER KIRCHNER: Is a part of it, yeah.

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47 1 MEMBER PETTI: No, I think that would 2 help. It's a context issue, really. Think about 3 reading these things four years from now or something, 4 you know, when you've lost all of it. That's the 5 concern that I have.

6 MEMBER KIRCHNER: Yeah.

7 MR. VAN WERT: I do want to hesitate some 8 because, you know, I don't want to put words in 9 Kairos' mouth as well as far as their business plans.

10 As you heard this morning, they were saying that it's 11 also possible they decided that, you know, Hermes 12 costs too much, licensing is too difficult, or 13 whatever. And so if they decide not to do that, you 14 know, that's a business decision on their part.

15 And another applicant could come in, you 16 know, or another method would have been if they were 17 to run these simply in a laboratory setting, you know, 18 patent or whatever, and not even do Hermes whatsoever.

19 That's an option. That's their decision.

20 I do want to say hats off to them for 21 building a prototype. Because I do think that's the 22 best test that they could do. So I don't want to say 23 that they have to build the prototype. But I do think 24 that if they do they're going to -- this is what 25 they're going to be using to inform their future 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 1 decisions.

2 And I think with that in mind, what they, 3 you know, our determination was that what they have 4 supplied is sufficient for its purpose, for building 5 Hermes and for doing the testing there.

6 MR. TOMPKINS: Yeah. And if I could just 7 add, we have no plans to not do Hermes. I don't want 8 to kind of give a --

9 (Laughter.)

10 MR. TOMPKINS: But, you know, things 11 change, right.

12 MR. VAN WERT: Yeah. There is no 13 requirement as staff limitations that they must build 14 it, just to be clear. Any other questions on this 15 before we go to the next slide?

16 All right, next slide, this is approaching 17 the end. Again, we're just mentioning here that in 18 addition to the, you know, what Kairos calls 19 limitations within their topical report, we have the 20 one single additional staff limitation which is that 21 future license applications for non-power, read 22 Hermes, will include justification for the 23 applicability of this methodology during rapid reactor 24 transient events.

25 And then the next slide is conclusions.

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 1 Simply that, in conclusion, as discussed in the 2 previous slides and presented in the staff's safety 3 evaluation report, the staff reviewed the topical 4 report and concludes that the fuel qualification 5 methodology contained within is acceptable for 6 supporting fuel qualification of the Kairos fuel 7 pebbles in either a non-power or a power version of 8 the KP-FHR.

9 And that is all. If there is any further 10 questions, I'd be happy to answer them.

11 MEMBER PETTI: Okay, no other questions.

12 MEMBER BIER: Dave?

13 MEMBER PETTI: Yeah?

14 MEMBER BIER: Quick question which is 15 probably for the Hermes folks, not for the staff, the 16 Kairos folks, sorry. Is there any expectation for the 17 timing of Hermes, assuming that things to ahead as 18 currently planned? I probably read that someplace and 19 have forgotten it.

20 MR. TOMPKINS: Yeah. I think it's in the 21 2026 timeframe, something like that. To start up, you 22 mean?

23 MEMBER BIER: Yeah, just when is the ACRS 24 going to see information, you know, regarding detailed 25 plans and that kind of stuff?

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 1 MR. TOMPKINS: Well, ACRS is going to see 2 the Hermes CP application in April, I believe.

3 MEMBER BIER: Perfect. Thank you.

4 MR. TOMPKINS: Okay.

5 MEMBER PETTI: Okay. I guess we'll open 6 up for comments from the public. Identify yourself 7 and state your comment.

8 Okay, not hearing any. Then I think --

9 CHAIR REMPE: Okay. So we --

10 MEMBER PETTI: Back to you.

11 CHAIR REMPE: Okay. We've been in session 12 about an hour. And there was talk about a closed 13 session. Do you want to do that? Because I don't 14 think it'll last more than ten or 15 minutes before we 15 take a break and read the letter, the draft letter in?

16 MEMBER PETTI: Do members want the closed 17 session? No?

18 CHAIR REMPE: Oh, does anyone want the 19 closed session to discuss this?

20 MEMBER BALLINGER: I sent stuff direct to 21 Dave.

22 CHAIR REMPE: You don't want to see what 23 they've got on their chart at all?

24 MEMBER KIRCHNER: Not at this point.

25 CHAIR REMPE: Okay.

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51 1 MEMBER BIER: Are there additional Kairos 2 presentations that were planned for closed session or 3 just Q&A.

4 MR. TOMPKINS: No, no.

5 MEMBER BIER: Okay, thank you.

6 CHAIR REMPE: Because it's not in their 7 submittal, and it's not in the SE, or maybe it's just 8 not needed to discuss it.

9 So if that's the case, then let's take a 10 -- let's see, it's almost 9:40. Let's wait until 11 about five until, and come back, and read in the 12 letter. Does that sound okay? It's a little bit more 13 than 15 minutes for people like Charlie who say I 14 never give you enough of a break.

15 So, okay, we're going to recess and come 16 back in five minutes. Thank you.

17 (Whereupon, the above-entitled matter went 18 off the record at 9:37 a.m.)

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

KP-FHR Fuel Qualification Methodology Topical Report AC RS F U L L CO M M IT T E E M E E T IN G N OV E M B E R 3 0 2022 O PE N S ES S IO N Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

Fuel Qualification Scope/Applicability Qualified fuel is defined as fuel for which reasonable assurance exists that the fuel, fabricated in accordance with its specification, will perform as described in the safety analysis (NUREG-2246)

Fuel qualification methodology is applicable to KP-FHRs Test and power reactors Qualification is subject to the methodology and limitations described in topical report Demonstration of qualification will be documented in safety analysis report documents as part of a licensing application under Part 50 or Part 52 2

Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

Fuel Qualification Methodology

• U.S. and International Experience Foundation of TRISO fuel particle technology

• Kairos Fuel Pebble and Particle PIRT The fuel element PIRT is used to identify high priority phenomena for investigation in the fuel qualification program

• Fuel Specification, Manufacturing, and Quality Control through Inspection Fuel specification equivalent to the AGR program Fuel Manufacturing Development Program (e.g. pebble pressed at pressures comparable to AGR compacts)

• Fuel Qualification Envelope Operation is within the bounds of existing AGR TRISO particle qualification envelope If not, an irradiation test is needed to expand the operational envelope Large temperature margins exist between AGR data and the KP-FHR designs for both test and power reactor 3 Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

Fuel Qualification Methodology (continued)

• Fuel Pebble Laboratory Qualification Testing Pebble laboratory testing program will ensure that pebbles protect the particles from physical damage and interaction with Flibe Pebbles tested for compression, impact, wear, infiltration, buoyancy, and compatibility with air and Flibe

• Fuel Irradiation Qualification Testing A method is included for future irradiation test of a statistically significant number of TRISO fuel particles at conditions beyond the bounds of existing AGR irradiation test data to support a wider operational envelope

• Fuel Performance Model Physics based models in KP-BISON are a quantifiable representation of fuel knowledge used for core design and source term analysis

• Fuel In-Service Surveillance Program Pebbles inspected multiple times for damage and burnup during lifetime Cover gas and Flibe monitored for radioactivity Destructive PIE for both the test and initial power KP-FHR 4

Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

Questions from the Subcommittee Meeting

• There were two questions from the Subcommittee Meeting that we would like to address in more detail Presence of transition metals in the Flibe and their effect on the SiC layer Pebble Irradiation Program Copyright © 2022 Kairos Power LLC. All Rights Reserved. 5 No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

Presence of Transition Metals in the Flibe

• Laboratory testing program described in the topical report will demonstrate that infiltration into the fuel region does not occur

• Flibe has to infiltrate to the fuel annulus to bring transition metal fluorides to TRISO

• It is not credible to have metallic transition metals to transport to TRISO because they are solids, which is different than AGR where metallic elements were liquids or gases

• Particle temperatures for KP-FHR fuel are well below AGR irradiation temperatures where Ni attack was observed (~500°C lower)

• Because of the low operating temperatures, any detrimental effects are expected to progress slowly

• TRISO failures would be observable by fission product monitoring in the gas and coolant spaces for the reactor and limited by the technical specification circulating activity limit 6

Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

Pebble Irradiation Testing for the Hermes Test Reactor

• The KP-FHR fuel qualification methodology ensures fuel meets the reasonable assurance criteria for qualification AND there is no safety concern due to the Flibe being an additional separate barrier to the release of radionuclides

• The AGR program extensively irradiation tested TRISO fuel particles that define the fuel qualification envelope for KP-FHRs

• Kairos Power is developing the pebble and particle manufacturing which ensures high quality fuel which is demonstrated through inspection to be in compliance with the fuel specification

• Defense-in-depth - TRISO fuel particles + Flibe coolant

• Irradiation testing cited in subcommittee meeting for prior precedent fuel designs were all for HTGRs which have higher normal operating and accident temperatures

• Fuel in-service surveillance and monitoring activity in the cover gas and coolant during operations provides further assurance fuel does not present a challenge to public health and safety 7

Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

Pebble Irradiation Testing for the Test Reactor (continued)

• The Hermes test reactor will provide important confirmation of the technology to support the deployment of a Kairos Power commercial power reactor

• Hermes is a full integral test of the Kairos fuel for a power reactor

• The licensing of test reactors is provided significant latitude in the Atomic Energy Act (AEA):

• In issuing licenses under this subsection of the AEA , the Commission shall impose the minimum amount of such regulations to fulfill its obligations under the act. (AEA Section 104b)

• The Commission is directed to impose only such minimum amount of regulation of the licensee as the Commission finds will permit the Commission to fulfill its obligations under this Act to promote the common defense and security and to protect the health and safety of the public and will permit the conduct of widespread and diverse research and development. (AEA Section 104c)

• The extensive TRISO particle irradiation testing performed under the DOE AGR program along with the Kairos Power laboratory qualification program of the fuel pebble design and the defense-in-depth provided by radionuclide retention in the Flibe coolant provides reasonable assurance of the protection of public health and safety consistent with the AEA 8 Copyright © 2022 Kairos Power LLC. All Rights Reserved.

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

NRC Evaluation of KP-TR-011-P, Fuel Qualification Methodology for the Kairos Power Fluoride Salt-Cooled High Temperature Reactor (KP-FHR), Rev. 2 Chris Van Wert US Nuclear Regulatory Commission November 30, 2022

Introduction

• Kairos Power, LLC requested staff review and approval of KP-TR-011-P, Rev. 2, Fuel Qualification Methodology for the Kairos Power Fluoride Salt-Cooled High Temperature Reactor (KP-FHR)

• Provides a methodology by which the Kairos fuel pebble design 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:

• Use of existing data

• Surveillance

• Unirradiated testing

• Irradiation testing 2

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

50.34(b), 50.43(e), and corresponding regulations for design certification applications, combined license applications and standard design approvals 10 CFR 100.11 Determination of exclusion area, low population zone and population center distance Kairos PDC 10 - Reactor design which has been approved by the staff (KP-TR-003-NP-A)

KP-FHR PDC 16, Containment Design which has been approved by the staff (KP-TR-003-NP-A) 3

Staff Evaluation Applicability of Existing Data

• KP-TR-011, Rev. 2 is applicable based on a comparison of the Kairos and AGR-2 particles as well as the operating conditions

• Use of existing carbon matrix property data is applicable for determining pebble testing conditions for fuel qualification Fuel Surveillance

• Surveillance of the cover-gas, non-destructive examinations, and planned destructive examinations are acceptable for monitoring fuel performance and detecting particle failure 4

Staff Evaluation (cont.)

Unirradiated Testing

• Planned tests include mechanical, tribology, buoyancy and salt infiltration, and material compatibility

• The planned unirradiated pebble testing is acceptable based on the conservative test conditions and plant operating conditions Irradiation Testing

• Fuel pebble irradiation in a gas environment

• Purge gas monitoring for fission gas

• Post Irradiation Examinations 5

Coolant Salt Impurities

• The staff considered sources available for impurities which could attack the particles (e.g. Fe, Cr, Ni, etc.)

• The transport of significant impurities to the fuel particles is not feasible given the chemistry monitoring system, solubility limits in molten salt, cover gas monitoring system, and significantly lower temperatures as compared with AGR-5 6

Staff Limitations The staffs approval of KP-TR-011-P includes the following staff limitation in addition to the limitations provided by Kairos in Section 4.2 of the topical report:

Future license applications for non-power KP-FHRs will include justification of the applicability of this methodology during rapid reactor transient events.

7

Conclusions The staff reviewed the topical report KP-TR-011-P, Rev. 2 and concludes that the fuel qualification methodology contained within is acceptable for supporting fuel qualification of Kairos fuel pebbles in either non-power or power reactor versions of the KP-FHR.

8

Questions?

9