ML23031A014
| ML23031A014 | |
| Person / Time | |
|---|---|
| Issue date: | 01/12/2023 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-2228 | |
| Download: ML23031A014 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Kairos Power Licensing Subcommittee Open Session Docket Number:
(n/a)
Location:
teleconference Date:
Thursday, January 12, 2023 Work Order No.:
NRC-2228 Pages 1-112 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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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 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 4
(ACRS) 5
+ + + + +
6 KAIROS POWER LICENSING SUBCOMMITTEE 7
+ + + + +
8 OPEN SESSION 9
+ + + + +
10 THURSDAY 11 JANUARY 12, 2023 12
+ + + + +
13 The Subcommittee met, via Teleconference, 14 at 9:30 a.m. EST, David A. Petti and Ronald G.
15 Ballinger, Chairs, presiding.
16 17 COMMITTEE MEMBERS:
18 DAVID A. PETTI, Chair 19 RONALD G. BALLINGER, Chair 20 VICKI M. BIER, Member 21 CHARLES H. BROWN, JR., Member 22 VESNA B. DIMITRIJEVIC, Member 23 WALTER L. KIRCHNER, Member 24 GREGORY H. HALNON, 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 JOSE MARCH-LEUBA, Member 1
JOY L. REMPE, Member 2
MATTHEW W. SUNSERI, Member 3
4 ACRS CONSULTANTS:
5 DENNIS BLEY 6
8 DESIGNATED FEDERAL OFFICIALS:
9 WEIDONG WANG 10 CHRISTOPHER BROWN 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
Kairos Power Topical Report (KP-TR-014), "Graphite 2
Materials Qualification for the Kairos Power Fluoride 3
Salt-Cooled High-Temperature Reactor" 4
Call to Order..................
5 5
ACRS Chairman Introductory Remarks 5
6 NRC Staff Introductory Remarks 8
7 Bill Jessup, NRR 8
8 Kairos Power Introductory Remarks and 9
Overview of Graphite Materials Qualification 10 Topical Report (KP-TR-014)
........... 10 11 Margaret Ellenson, Kairos Power.... 10, 41 12 Chong Chen, Kairos Power
......... 22 13 Gabriel Merick, Kairos Power
....... 30 14 Graphite Qualification Topical Report 15 Safety Evaluation................ 51 16 Richard Rivera, NRR............ 51 17 Alex Chereskin, NRR............ 52 18 Public Comments (None)
............. 76 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
5 P-R-O-C-E-E-D-I-N-G-S 1
9:30 a.m.
2 CHAIR PETTI: Okay, it's 9:30 Eastern, so 3
this meeting will now come to order.
4 Happy New Year, everyone.
5 This is a meeting of the Kairos Power 6
Licensing Subcommittee of the Advisory Committee on 7
Reactor Safeguards. I'm David Petti, Chairman of 8
today's Subcommittee meeting.
9 ACRS members in attendance are Charles 10 Brown, Jose March-Leuba, Joy Rempe, Matthew Sunseri, 11 Ron Ballinger, Walt Kirchner, and Greg Halnon. I do 12 not see Vesna or Vicki on the line yet.
13 MR. WANG: Actually, Vesna, I saw her.
14 CHAIR PETTI: You did? Okay.
15 Dennis
- Bley, Consultant, and Steve 16 Schultz, our Consultants, are on the line.
17 Weidong Wang of the ACRS staff is the 18 Designated Federal Official for this meeting.
19 During today's meeting, the Subcommittee 20 will review the staff's Safety Evaluation on Topical 21 Report "Graphite Material Qualification for the Kairos 22 Power Fluoride Salt-Cooled High-Temperature Reactor,"
23 Revision 4.
24 The Subcommittee will hear presentations 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 by and hold discussions with the NRC staff, Kairos 1
Power representatives, and other interested persons 2
regarding this matter.
3 Part of the presentations by the Applicant 4
and the staff may be closed in order to discuss 5
information that is proprietary to the licensee and 6
its contractors, pursuant to 5 USC 552b(c)(4).
7 Attendance at the meeting that deals with such 8
information will be limited to the NRC staff and its 9
consultants, Kairos Power, and those individuals and 10 organizations who have entered into an appropriate 11 confidentiality agreement with them. Consequently, we 12 need to confirm that we have only eligible observers 13 and participants in the closed part of the meeting.
14 The rules for the participation in all 15 ACRS meetings, including today's, were announced in 16 The Federal Register on June 13th, 2019.
17 The ACRS section of the U.S. NRC public 18 website provides our Charter, Bylaws, and agendas, 19 Letter Reports, and full transcripts of all full and 20 subcommittee meetings, including slides presented 21 there. The meeting notice and agenda for this meeting 22 were posted there.
23 We have received no written statements or 24 requests to make an oral statement from the public.
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 The Subcommittee will gather information, 1
analyze relevant issues and facts, and formulate 2
proposed positions and actions, as appropriate, for 3
deliberation by the full Committee.
4 The rules for participation in today's 5
meeting have been announced as part of the notice of 6
this meeting previously published in The Federal 7
Register.
8 A transcript of the meeting is being kept 9
and will be made available, as stated in The Federal 10 Register notice.
11 Due to the COVID pandemic, today's meeting 12 is being held over Microsoft Teams for ACRS, NRC 13 staff, and licensee attendees. There's also a 14 telephone bridge line, allowing participation of the 15 public over the phone.
16 When addressing the Subcommittee, the 17 participants should, first, identify themselves and 18 speak with sufficient clarity and volume, so that they 19 may be readily heard. When not speaking, we request 20 that participants mute their computer microphone, or 21 phone, by pressing *6.
22 We'll now proceed with the meeting, and 23 I'd like to start by calling upon NRR staff.
24 MR. RIVERA: Thank you.
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 MR. JESSUP: Yes, thank you, Member Petti, 1
for the opportunity to present to the Subcommittee 2
this morning.
3 My name is Bill Jessup, Chief of Advanced 4
Reactor Licensing Branch 1 in the Division of Advanced 5
Reactors and Non-power Production Utilization 6
Facilities in the Office of Nuclear Reactor 7
Regulation.
8 Kairos is currently developing non-power 9
and power reactors that would use its fluoride-cooled, 10 high-temperature reactor technology, also referred to 11 as KP-FHR technology.
12 As you know, the staff is currently 13 reviewing the construction permit application from 14 Kairos for its non-power Hermes Test Reactor that 15 would use the KP-FHR technology.
16 The two Topical Reports that we're going 17 to be discussing today would apply to both the non-18 power and power reactors currently under development 19 by Kairos. Therefore, the reviews for the Topical 20 Reports we're going to discuss today will need to be 21 finished before we can complete the construction 22 permit application review.
23 The first Topical Report on the 24 qualification of graphite materials describes 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
9 testing required to qualify, the structural graphite 1
materials used, and the safety-related components of 2
the KP-FHR designs.
3 The second Topical Report on the 4
qualification of metallic materials focuses on the 5
testing and modeling required to qualify the 6
structural alloys that will be used in the safety-7 related portion of the KP-FHR designs.
8 And as the agenda notes, the staff will 9
provide an overview of our review and safety 10 evaluation of each Topical Report following the Kairos 11 presentation on each of the Topical Reports.
12 I'd also like to note today, during the 13 staff presentations, you'll hear discussions regarding 14 guidance that the staff used for the review of both 15 Topical Reports from Regulatory Guide 1.87, 16 "Acceptability of ASME Code,Section III, Division 5, 17 High Temperature Reactors, Revision 2."
18 A draft of Reg Guide 1.87, Revision 2, was 19 issued for public comment in August 2021, along with 20 a supplement to the draft that was issued in February 21 2022.
22 The staff has resolved public comments 23 received during the public comment period, and we 24 expect that the final draft of Revision 2 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
10 issued in short order.
1 Any discussions of guidance from Reg Guide 2
1.87, Revision 2, during today's presentations and in 3
the Draft Safety Evaluations for each Topical Report 4
represents staff positions that will be reflected 5
accordingly in the final draft of the Reg Guide.
6 We're looking forward to today's 7
discussions and are always appreciative of the 8
Committee's insights and comments on these very 9
important topics related to the Kairos KP-FHR 10 technology.
11 And with that, I'll turn it back over to 12 you, Member Petti.
13 CHAIR PETTI: Okay. Thank you.
14 So, I guess we'll turn to Kairos and go 15 through the slides that we've seen.
16 MS. ELLENSON: Hi. This is Margaret 17 Ellenson. I am work for Kairos Power on the licensing 18 team. I'm the lead for this particular Topical 19 Report.
20 We also greatly appreciate the opportunity 21 to present to the ACRS our presentations. Obviously, 22 we focused on just what is in that Topical Report.
23 And I have a number of our technical staff 24 here who are going to present along with me, Gabriel 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 Merick and Chong Chen, in particular.
1 Yes, we look forward to the discussion and 2
the opportunity to present. Thanks very much. I 3
don't have any further comments unless --
4 CHAIR PETTI: Okay. So, who in Kairos is 5
going to start then?
6 MS. ELLENSON: Oh, okay, we're ready to 7
go?
8 CHAIR PETTI: Yes.
9 MS. ELLENSON: Okay, great. So, I'm going 10 to begin.
11 Hi. My name is Margaret Ellenson. I'm on 12 the Kairos Power licensing team. I've been with 13 Kairos for about three years. Prior to that, I was 14 with the NRC for about 15 years. I worked on the 15 Steam Generator Tube Integrity Program as well as fire 16 protection and security issues. So, a wide gamut.
17 Our purpose today for this Topical Report 18 is to provide an overview of the content of the 19 Graphite Material Qualification Plan that Kairos 20 expects to use to qualify structural graphite 21 materials for use in a KP-FHR. That is a Kairos Power 22 Fluoride Salt-Cooled High-Temperature reactor.
23 We'll be covering some of the material, 24 some of the content of that Topical Report in this 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 open session, and then, later, we'll be getting into 1
more details about other subjects during the closed 2
session.
3 And just to double-check, you can all see 4
my slides, is that correct?
5 CHAIR PETTI: Yes.
6 MS. ELLENSON: Great. Okay.
7 Kairos Power is a
mission-based 8
organization. Our mission is to enable the world's 9
transition to clean energy, with an ultimate goal of 10 dramatically improving people's quality of life while 11 protecting the environment.
12 We like to touch base with this mission 13 for each of our meetings and our key milestones. And 14 this Topical Report is one step toward accomplishing 15 that mission.
16 In particular, graphite is a unique 17 material for use in this regulatory context. So, 18 we're excited to be able to discuss this with ACRS and 19 the content of this Topical Report today.
20 I wanted to spend a brief moment kind of 21 getting at the purpose of Kairos submitting this 22 particular Topical Report. What we're hoping to 23 accomplish with this report is to align expectations 24 early about the methods that Kairos will use to 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 qualify graphite in a KP-FHR.
1 As the members here are probably well 2
aware, there are many steps along the way to 3
qualification of a material. And ultimately, 4
qualification is demonstrated in an application-5 specific Safety Analysis Report.
6 So, the goal of this particular Topical 7
Report is to identify those methods that can close 8
gaps between existing data and the data or analyses 9
that will be needed to support that qualification in 10 a Safety Analysis Report.
11 Obviously, the final design of the KP-FHR 12 will be important inputs as well to that 13 qualification. So, what the Topical Report covers is 14 the data, models, and analysis that will be needed to 15 be provided in a future license application.
16 Okay. I also wanted to provide a quick 17 reminder about our functional containment strategy for 18 a KP-FHR. You probably have seen this particular 19 image or slide before, but, just as a reminder, 20 containment is provided by the TRISO particles in our 21 fuel pebbles.
22 The second element of functional 23 containment is the Flibe coolant which has good 24 fission product retention properties. I'm bringing 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 this up now because I wanted to make it clear that the 1
concentration of fission products in our coolant, the 2
Flibe coolant, will be maintained at very low levels 3
during operation. And this is unlike other molten 4
salt reactors that might have dissolved fuel. Those 5
dissolved fuel molten salt reactors can develop hot 6
spots due to coolant infiltration into graphite.
7 That's not really something that is an issue for a KP-8 FHR technology.
9 I also want --
10 MEMBER MARCH-LEUBA: Hey, this is Jose.
11 This is Jose March-Leuba.
12 MS. ELLENSON: Yes? Hi.
13 MEMBER MARCH-LEUBA: What, approximately, 14 is the retention, the sequestration time of the Flibe 15 in the core? I mean, what's the time course if there 16 was a contamination?
17 MS. ELLENSON: The residence time for the 18 Flibe in the core or for fission product retention?
19 Those things I think would be heavily design-20 dependent. So, we don't necessarily have the hard 21 numbers yet for those.
22 MEMBER MARCH-LEUBA: I'm not looking for 23 the hard numbers. Is it seconds? Is it minutes?
24 Hours? Days? Years? What unit will you use?
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15 MS. ELLENSON: Yes, I'm looking at some of 1
our other design experts around the room here. Just 2
one moment.
3 Maybe on the order of seconds or minutes.
4 MEMBER MARCH-LEUBA: Seconds or minutes to 5
move through the core, and then, a fraction of it will 6
go through the cleanup system? Maybe 10 percent or --
7 MS. ELLENSON: Yes, I wouldn't know. I 8
wouldn't know the fraction. That would be part of the 9
design of the Flibe Inventory Management System.
10 MEMBER MARCH-LEUBA: So, basically, if I 11 was going to think about daily you will remove, at 12 most once a day, it would be cleaner. So, there won't 13 be any significant concentration increase over time?
14 MS. ELLENSON: It will be a managed 15 parameter. So, the concentration of fission products 16 and the character, the nature, of the Flibe will be a 17 managed parameter in KP-FHR.
18 MEMBER MARCH-LEUBA: Okay.
19 MS. ELLENSON: Yes. Okay.
20 I also wanted to bring up a reminder with 21 this slide that there are two places where you will 22 find graphite in a KP-FHR core. One is the graphite 23 reflector structure. That's the subject of this 24 Topical Report. There's also graphite in the fuel 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 pebbles themselves. That is out of scope for this 1
particular Topical Report. It is covered by other 2
Topical Reports submitted by Kairos Power.
3 CHAIR PETTI: So, I just, for the record, 4
so that people don't get confused, the matrix is not 5
graphitized. It's probably better characterized as a 6
carbonaceous material, to differentiate it from the 7
actual reflector, which is a true graphite that goes 8
through high-temperature graphitization.
9 Thanks.
10 MS. ELLENSON: Thank you.
11 MEMBER KIRCHNER:
And just for 12 clarification -- this is Walt Kirchner -- so, this 13 report does not qualify these same materials for the 14 primary coolant boundary; just for the vessel?
15 MS. ELLENSON: Yes, that's correct.
16 MEMBER KIRCHNER: So, you're illustrating 17 the reactor cavity here and excluding the rest of the 18 primary coolant loop?
19 MS. ELLENSON: Yes, that's correct.
20 MEMBER KIRCHNER: Okay. Thank you.
21 MS. ELLENSON: Okay. All right. I also 22 wanted to take a moment before we get into the details 23 of the qualification plan to talk about the scope of 24 this Topical Report and to make sure that we're 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 aligned on what components are we actually talking 1
about here, and in particular, to clarify the safety 2
functions of this structural graphite in the reactor 3
vessel.
4 The role of the reflector structure is to 5
support two different safety functions. You can see 6
in this cartoon, which is intentionally cartoonized 7
because it reflects what's common between a test and 8
a power reactor, you could see that the blue and the 9
red here reflect where the coolant is flowing. So, 10 you can see that the graphite reflector forms one part 11 of the conduit or channel through which Flibe coolant 12 will flow.
13 It also provides the pathway through which 14 reactivity control elements can be inserted. So, the 15 two safety functions there that it supports are the 16 removal of heat from the reactor and the insertion of 17 negative reactivity, or reactivity control, I should 18 say.
19 However, the way that it supports those 20 safety functions is simply by maintaining its 21 integrity. So, by staying whole, it maintains those 22 channels for the control, reactivity control elements 23 to insert, and it also maintains the flow path for the 24 coolant.
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18 It does not provide a safety function 1
related to moving heat from one place to another.
2 There's other systems that provide that safety 3
function.
4 So, I just wanted to make sure that we 5
were clear about what the safety functions are that we 6
need to qualify this material for.
7 MEMBER BROWN: This is Charlie Brown. Can 8
I ask you a question relative to the figure?
9 MS. ELLENSON: Sure.
10 MEMBER BROWN: So, the graphite itself is 11 not a heat removal function itself? It's merely a 12 reflector function, and the heat removal is done by 13 other means? That's the way -- I'm not a designer.
14 That's why I'm asking the question the way I'm asking.
15 MS. ELLENSON: Yes, exactly. Its safety 16 function is to stay whole, so that the coolant can 17 flow the way its designed to. Otherwise, it does not 18 have a function in heat removal.
19 MEMBER BROWN: Okay. And the second 20 question is, in the Topical Report it talked about the 21 reflector, the graphite reflector, being buoyant in 22 the Flibe coolant flow. I didn't understand how 23 something would be buoyant and just kind of floating 24 around in the flow path. It's not stably, or does it 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 just move around? That's the way I read it.
1 MS. ELLENSON: Yes, it is designed -- if 2
you see some of the pictures that we have of our ETU 3
unit in New Mexico, you'd see that it, basically, 4
fills the reactor vessel, right, except for this 5
cavity that's in the center, where the actual fuel 6
pebbles will go. The graphite is maintained in a 7
certain orientation, but it doesn't bear any 8
structural loads. That's why we bring up the idea of 9
buoyancy. It's not actually bearing any weight or 10 structural
- loads, like, for
- example, a
high-11 temperature gas reactor might.
12 MEMBER BROWN: Okay. In other words, it 13 is fixed? It's just not --
14 MS. ELLENSON: It is fixed.
15 MEMBER BROWN: -- bearing any loads?
16 MS. ELLENSON: Yes.
17 MEMBER BROWN: All right. Thank you very 18 much.
19 MEMBER BALLINGER: Charlie, all they're 20 saying -- this is Ron Ballinger -- all they're saying 21 is that the graphite is less dense than the --
22 MEMBER BROWN: That part I got. It was 23 the openness of the buoyancy thought process that made 24 it -- I just wanted to make sure I understood 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
20 connection, and now I do. I appreciate that. Thank 1
you.
2 MEMBER BALLINGER: It doesn't have a 3
ballast tank. It doesn't have ballast tanks.
4 MEMBER BROWN: Right. Okay. Thank you.
5 MS. ELLENSON: All right. Okay. All 6
right. I briefly wanted to walk through just the 7
organization of this report.
8 It has what you would expect at the 9
beginning: introductory material, background on 10 nuclear graphite.
11 The next three bullets on this slide --
12 unirradiated graphite, irradiated graphite, and 13 environmental compatibility -- those reflect the 14 technical meat of the report.
15 We also have some conclusions and 16 limitations in there, limitations primarily related to 17 elements where our final design may affect the 18 qualification program that we use.
19 And then, there's a few appendices that 20 get into some of the details of the analysis and 21 demonstration that we would do in our qualification 22 program.
23 And just a reminder about the scope, that 24 this report does apply to both a test reactor and a 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
21 power reactor application, and that seismic 1
qualification is out of scope for this particular 2
report.
3 Okay. The qualification plan represented 4
in the report largely follows the ASME BPV, Section 5
III, Division 5, Code, and I commonly refer to this as 6
just the Division 5 Code. There's a portion of that 7
Code that specifically addresses graphite materials.
8 It breaks the qualification into three different 9
elements:
characterization of as-manufactured 10 graphite mechanical and thermal properties, which we 11 refer to as unirradiated graphite in the report. And 12 that portion of our Topical Report we'll talk about 13 how thermal and mechanical properties are within 14 expected variability.
15 The Code also specifies a sampling plan to 16 use for those confirmatory tasks. In this section of 17 the report -- this is Chapter 3 -- we also make a 18 connection back to properties related to fatigue, as 19 well as a discussion of purity, which is not 20 necessarily discussed in the Division 5 Code, but we 21 provide some context in the report there.
22 The second element there, characterization 23 of graphite properties under irradiation, the Topical 24 Report talks about both basic properties and 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 irradiation creep properties. It discusses the use of 1
existing data, new data, existing models, new models, 2
and how those things would be applied to both a test 3
reactor or a power reactor application.
4 A detailed discussion of those two 5
chapters, the unirradiated graphite and the irradiated 6
graphite, we expect to do in the closed section.
7 And then, the fifth chapter of the Topical 8
Report is Environmental Compatibility. This is a non-9 mandatory section under the Code, but Kairos Power 10 reviewed the available phenomena identification 11 studies that have been issued to date. For example, 12 Idaho National Lab, Oak Ridge National Lab, Georgia 13 Tech did some phenomena identification studies for 14 either a molten salt reactor or for graphite use in 15 reactors. We also reviewed relevant literature to 16 identify different phenomena that could be of interest 17 to structural graphite in a KP-FHR application.
18 And at this point, I'm going to hand over 19 the discussion to my colleague Chong Chen, who is our 20 graphite expert, to be able to give some background on 21 graphite.
22 Chong, are you able to introduce yourself?
23 MR. C. CHEN: Yes, sure. Thank you.
24 My name is Chong Chen, and I'm a 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
23 engineer. I've work for Kairos since 2020. Before 1
that, I work in GrafTech, formally GrafTech, and SGL 2
3 And so, a little bit of the background 4
about graphite. Graphite, it, basically, is a carbon 5
organized unit in a structured way. It has a 6
crystalline structure, and basically, it's all carbon 7
content.
8 And graphite is very thermally stable. In 9
the inert atmosphere it is stable over 3200 degrees C 10 or higher, and essentially, the highest temperature 11 used in any industry.
12 Mechanical strength, also, is different 13 compared with metal. And the strength increases with 14 temperature. Yes, that's the difference, and also, a 15 very low coefficient of thermal expansion. But one 16 thing that is different compared to metal is graphite 17 is not an anisotropic material. They have a different 18 property in a certain direction.
19 Graphite also has a certain porosity 20 property, above 20 percent porosity. And the 21 property, due to the pure use in the manufacture 22 process, the property, there's a variability. It's 23 not as uniform as typical metal you will see in the 24 industry.
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24 And the last thing I wanted to mention for 1
graphite is that the billets has a limitation, and it 2
is difficult to make very large billets, especially 3
for fine grain or superfine grain. So, people tend to 4
have a bigger billets to save the cost, but it is 5
sometimes not the case for superfine grain graphite.
6 CHAIR PETTI: So, just a question then.
7 So, the billets for superfine grade tend to be smaller 8
than the extruded graphites?
9 MR. C. CHEN: That's correct. It is the 10 case, yes.
11 CHAIR PETTI: I mean, I know how big the 12 historic grades were. How big would the billet be?
13 MR. C. CHEN: Well, different industry has 14 a different size. Just to give you a visual, 15 typically, we -- well, the one typical we talk about 16 for this case, the graphite we're going to use, the 17 rocky bottom is 1x2x4 feet in this kind of size.
18 That's just roughly.
19 CHAIR PETTI: Uh-hum. Good.
20 MEMBER KIRCHNER: So, Chong, this is Walt 21 Kirchner.
22 So, that means you'll have to stack these 23 for the reflector in the larger power reactor 24 application?
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25 MR. C. CHEN: Yes.
1 MEMBER KIRCHNER: I don't remember the 2
dimensions for Hermes, but can you make the reflector 3
out of one stack, one billet?
4 MR. C. CHEN: No.
5 MEMBER KIRCHNER: Okay.
6 MR. C. CHEN: No, no way to make that 7
large graphite. That would be ideal, but it's not the 8
case.
9 MEMBER KIRCHNER: Okay. Thank you. Thank 10 you.
11 MEMBER HALNON: This is Greg.
12 Where is this ET-10, where is it developed 13 or manufactured?
14 MR. C. CHEN: Okay. Yes. So, ET-10 is 15 the grain graphite produced by IBIDEN. It's the 16 company.
17 MEMBER HALNON: What country is it being 18 developed in?
19 MR. C. CHEN: That's a Japanese company.
20 MEMBER HALNON: Okay. And quality 21 control, how is that maintained, so that you know that 22 you're getting the top quality stuff? And do they 23 have a testing program representative sample or is 24 every billet checked? Or how is that done?
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26 MR. C. CHEN: Yes, I think there were 1
details laid out in, I think more regarding the 2
quantity, and I think in the closed session we'll 3
discuss that.
4 MEMBER HALNON: Okay.
5 MEMBER BALLINGER: This is Ron Ballinger.
6 So, it's ET-10, not 110? And the source 7
for KP-FHR is now limited to that source? Because, a 8
lot of times, the source really determines a lot of 9
the properties.
10 MR. C. CHEN: Well, yes. And so, once you 11 quantify this, basically, you stay with this material, 12 you're quantified.
13 MEMBER BALLINGER: Right, but what I mean 14 is, is it down to the source itself, where the 15 precursor material is actually obtained?
16 MR. C. CHEN: Oh, yes. So, yes, that's 17 another topic. So, how do we control the material we 18 have quantified today will be the same when using it 19 later? So, where there's the best knowledge, the 20 process, we ensure we've got the material down to even 21 stock on the raw material, making the stuff, the 22 graphite.
23 MEMBER BALLINGER: Yes, okay. That's my 24 general understanding of where you have to start.
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27 MR. C. CHEN: Yes. Yes, you have to 1
control the raw material properties, start with the 2
raw material property.
3 CHAIR PETTI: Chong, just a question. I 4
was a little confused in the Topical. Here, you say 5
ET-10, but there's also ETU-10. I thought that what 6
was going into Hermes was ETU-10, but that all the 7
testing would be done on ET-10, where the "U" just 8
represents the halide process to get rid of some of 9
the impurities and wouldn't affect the thermal or 10 mechanical properties. Do I have that right?
11 MR. C. CHEN: I think it's the ET-10 12 itself, the purities that meet a requirement. So, I 13 think maybe in the early document you see ETU-10, but 14 I think the updated version is ET-10. I think I will 15 refer it to our licensing team and see if that's the 16 case.
17 CHAIR PETTI: Oh, okay. I don't know 18 which version we were reading, but there was 19 discussion in the document about ETU and the halide 20 process. So, you're saying that you're actually going 21 to qualify and use ETU? You're not going to use the 22 higher purity graphite?
23 MR. C. CHEN: We will use ET-10, not ETU-24 10.
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28 CHAIR PETTI: Okay.
1 MR. C. CHEN: Because ET-10, it's purity; 2
it's to meet the requirement. It's very pure 3
material. So, it's not necessary we go through 4
another purification. It's unnecessary.
5 CHAIR PETTI: Okay.
6 MEMBER KIRCHNER: This is Walt.
7 So, you don't think you need the halide 8
process for ET-10 if you can control the raw materials 9
coming in?
10 MR. C. CHEN: Yes. Right. Correct.
11 MEMBER KIRCHNER: Okay. I'll just come 12 back to this in the closed session. I have some 13 questions about impurity levels.
14 MR. C. CHEN: Sure. Okay. So, okay. If 15 there's no further question, I will continue.
16 So, graphite has been used -- I guess 17 everybody in this meeting room well understood it has 18 been used in the nuclear reactor for a long time and, 19 also, accumulated some data. In the Topical Report we 20 reference different graphite, and IG-110 is well-known 21 and CGB, it's used in a molten reactor experiment.
22 Okay. Now we're back to the ET-10 we 23 already talked about. It's isotropic loaded material.
24 By definition, it's the near isotropic material, or 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 that's what we're talking about.
1 All right. Next slide, please.
2 Well, environmental compatibility, or just 3
the highlights of what we are looking at. We 4
considered five phenomena which can potentially damage 5
graphite integrity or structure. And we consider from 6
a physical side and we consider infiltration -- and it 7
will be talked about in the closed section -- and 8
also, mechanical reduction, due to the infiltration or 9
impact due to the stress.
10 And as Margaret pointed out in the earlier 11 stage, in the earlier presentation, in the graphite 12 reflector we are using, it's different compared with 13 a gas-cooled reactor. Basically, it does not have a 14 lot of load on it because the density of graphite is 15 much less than the salt, molten salt's density. And 16 another phenomenon we consider is erosion and 17 abrasion.
18 On the chemical side, we consider chemical 19 compatibility between the graphite and the Flibe, and 20 also, oxidation, which is only one section of a 21 reactor will have oxidation, potential oxidation, in 22 cases of the leak.
23 CHAIR PETTI: So, just again, a question 24 here. Here it says ETU-10. So now, I'm confused. 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
30 it ETU or ET-10? Which one is it actually, are you 1
going to actually use in qualifying and doing testing?
2 MR. C. CHEN: ET-10. ET-10. It must be 3
a typo, I guess.
4 CHAIR PETTI: Okay. Okay. Thank you.
5 MR. C. CHEN: All right. Next slide, 6
please.
7 Okay. I think my colleague Gabriel will 8
cover this slide.
9 MR. MERICK: Hi. This is Gabriel. One 10 second.
11 (Pause.)
12 All right. Sorry for the technical issue 13 here.
14 My name is Gabriel Merick. I am a 15 materials engineer at Kairos. My expertise is in 16 radiation effects, and for Kairos, I'm leading the 17 radiation testing part and, also, this abrasion and 18 erosion part of the Topical Report.
19 So, this is part of our environmental 20 compatibility testing. We will be doing some 21 tribology testing to confirm that there's no 22 significant abrasion of our structural graphite.
23 There's no abrasion expected because, as we said 24 earlier, the reflectors are buoyant in the Flibe, and 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 the contact portions are, therefore, very low. Also, 1
structural graphite ET-10 is harder than our fuel 2
pebbles. So, we don't expect abrasion from the 3
pebbles rubbing against the graphite reflector. I'm 4
doing confirmatory testing for that.
5 The second point there is to confirm that 6
we don't have significant erosion of our structural 7
ET-10 reflectors. And we confirm that with testing of 8
graphite specimen exposed to long-term Flibe flow in 9
our rotating cage loop test systems. Again, we don't 10 expect significant erosion because our Flibe flow 11 velocity is low, especially compared to gas-cooled 12 reactors, and we have the MRSE experience, which 13 demonstrated no signs of erosion on the graphite 14 reflector surfaces after three years of operation.
15 MEMBER HALNON: So, this is Greg.
16 Will you be looking at surface roughness 17 as well and try to quantify the difference before and 18 after?
19 MR. MERICK: Yes, we'll be looking at this 20 and, also, more specifically, wear rates for the first 21 part there.
22 MEMBER HALNON: Okay. Because that's 23 significant I think in the infiltration discussion we 24 may have later on.
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32 MR. MERICK: Thank you.
1 MR. C. CHEN: Now, I'm going to pick up 2
here on the slides to talk about chemical 3
compatibility of graphite with Flibe.
4 The graphite is a very inert material in 5
most chemicals and has been studied, and there is no 6
significant graphite interaction or reaction, chemical 7
reaction, between graphite and Flibe molten salt which 8
leads to graphite structure degradation.
9 In a molten salt experiment conducted in 10 the '60s demonstrated, in graphite, there's no 11 graphite degradation observed after three years' 12 operation. So, that's very strong evidence.
13 And one particular reaction considered 14 that could lead to graphite structural degradation, 15 it's called intercalation. And from a later study, we 16 realize this indicated this could not happen under our 17 reactor operation conditions.
18 And fluorination, which means there is a 19 minor treatment with fluorination possible and it has 20 been reported recently in the literature. And we 21 thoroughly studied the literature results and 22 discussed it with the expert in this area. And we 23 don't think the treatment of surface fluorination will 24 lead to any bulk property change, and there's no bulk 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 fluorination that was observed. That's the key.
1 Any questions? If no further questions, 2
next slide, please?
3 DR. BLEY: Yes.
4 CHAIR PETTI: Just a question.
5 DR. BLEY: Oh, Dave, go ahead. Sorry.
6 CHAIR PETTI: My understanding is MSRE 7
only operated for one effective full power year. So, 8
that three years may be a calendar time, but in terms 9
of reactor operation, it's only one. It's fine. I 10 agree with you there's no degradation, but it's not as 11 much operation, I think, as we'd like to see. So, you 12 know, you could get a different experience with a 13 longer operation time.
14 MR. C. CHEN: You are right, but at this 15 moment, probably the best data, and the most relevant 16 and most useful data --
17 CHAIR PETTI: Correct. Correct. No, I 18 agree.
19 MR. C. CHEN: Yes, I agree with you, yes.
20 MEMBER BALLINGER: This is Ron Ballinger.
21 Am I to understand that the salt does not 22 wet the graphite?
23 MR. C. CHEN: Yes. Yes, the salt --
24 MEMBER BALLINGER: So, that's the source 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
34 of all of this good behavior, I think.
1 MR. C. CHEN: Correct. You are right.
2 DR. BLEY: This is Dennis Bley.
3 Could you tell us a little more about 4
intercalation, your second bullet, and if that 5
happens, what would be the problems? I guess where 6
I'm headed is, given your statement here, it would 7
seem the safety analysis is going to have to consider 8
this if we get outside of expected operating 9
conditions.
10 MR. C. CHEN: Yes. Sure. And 11 intercalation, let me give you one example. In the 12 graphite industry, when we make this flexible 13 graphite, which is you have intercaland go into the 14 graphite structure, and then, you heat treat it. So, 15 the graphite falls apart and turns, from a solid 16 piece, turns into almost like what we call a worm, 17 almost like a cushion, like a marshmallow-type thing, 18 and the total structure is totally destroyed. And 19 that's called intercalation.
20 This type of reaction is able to 21 destructure -- degradation. You've, basically, lost 22 all the structure, mechanical copy. And so, that's 23 what I am talking about. And for fluoride, there's no 24 evidence this kind of reaction can happen.
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35 So, does that answer your question?
1 DR. BLEY: Well, almost. So, you're not 2
really hanging your hat on operating conditions?
3 You're hanging your hat on the chemistry and that this 4
cannot happen? Is that what you're saying?
5 MR. C. CHEN: Well, we look at it based on 6
-- well, actually, there's a literature study that has 7
been done. And you put the graphite in the Flibe, and 8
you simulate to the reactor operation, the 9
temperature, and there, after that, you look at, 10 analyze the graphite structure. And is there any 11 intercalation that happened? And the conclusion from 12 the study is, no, there's no intercalation happening.
13 DR. BLEY: Okay. So, it's still hinging 14 on operating conditions. So, if we could get higher 15 temperatures than the expected ones in an accident, 16 this is something that ought to be addressed, is what 17 it sounds like to me.
18 Dave, maybe you're stronger --
19 CHAIR PETTI: Yes. No, I was trying to 20 put -- what exactly about the operating conditions 21 does it not occur? Is it just because the Flibe 22 doesn't wet?
23 MR. C. CHEN: No.
24 CHAIR PETTI: Is there something unique 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 about the reactor conditions? So, is there another 1
set of conditions where it could happen? That's what 2
we're trying to understand, I think.
3 MR. C. CHEN: Yes, okay. Let's start 4
with, I think intercalation has a lot to do with the 5
chemistry. And the current study has been done in 600 6
or 700 degrees. I don't recall exactly what 7
experiment temperature was used. It was in our 8
operation temperature range.
And there's no 9
integration observed. But, for this reaction, you 10 could say in an accident condition you could go to a 11 higher temperature.
- Actually, in a
higher 12 temperature, it's not favorable for this type of 13 reaction. So, it will not happen.
14 And just to give you an example, if this 15 reaction does not happen at 600 degrees C, it's not 16 going to happen in 800 degrees C. Because this means, 17 if you go to a higher temperature, this reaction can't 18 happen. So, not all the reactions go with the 19 temperature. So, that's what I'm trying to point out 20 here.
21 MEMBER BALLINGER: This is Ron Ballinger 22 again.
23 But there's no interconnected porosity 24 here, right?
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37 MR. C. CHEN: Graphite porosity is 1
interconnected.
2 MEMBER BALLINGER: It is interconnected?
3 MR. C. CHEN: It is.
4 MEMBER BALLINGER: Oh, okay.
5 MEMBER KIRCHNER: So, Ron, to follow up on 6
your question, and to try to get at Dennis' point, 7
this intercalation is the result of intrusion by 8
another chemical into the porosity of the graphite?
9 And you're saying that, for use applied, you don't 10 have that? Because it doesn't wet the surface, you 11 don't have that potential? What theory and literature 12 indicate it cannot occur? I mean, what is the 13 physical mechanism that can't occur in the KP-FHR?
14 MR. C. CHEN: Okay. So, let me step back 15 one step, and now let's differentiate -- I think it 16 may be the true term may be slightly confused.
17 intercalation is chemical reaction. It has nothing to 18 do with porosity and intrusion.
19 And infiltration, sounds like what you 20 mentioned, is really sort of porosity. You Flibe 21 infiltrate those into the pore structure, and because 22 it's interconnected, it can keep going and become a 23 (audio interference) process.
24 So, the intercalation is a chemical. It's 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
38 in the molecular level. As it intercalates, the 1
chemical goes into the graphite layer, between the 2
layer, graphite layer, and then, it, thus, can lead to 3
the structure damage. And that's the chemical 4
way/process to cause graphite structure damage.
5 And what I am saying here is this reaction 6
is not going to happen in this fluoride salt. There's 7
no evidence the fluoride salt will intercalate into 8
the graphite.
- Yes, that's what about the 9
intercalation.
10 And another thing about it that you 11 mentioned is, in infiltration, the Flibe goes into the 12 graphite structure. And whether the Flibe that goes 13 into the graphite structure will cause damage or not 14 is determined by several other factors, which is not 15 what we talk about here. I just want to clarify that.
16 MEMBER KIRCHNER: But, basically, when you 17 use this term, what you're talking about is attacking 18 the grain boundaries of the graphite structure?
19 MR. C. CHEN: Related, but not just the --
20 yes, the reaction will start with the grain boundary, 21 but it will go through, between the graphite layer.
22 So, it's -- yes.
23 MEMBER BALLINGER: Intercalation is --
24 CHAIR PETTI: There's a tremendous amount 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 of literature on intercalation in graphite.
1 MEMBER KIRCHNER: Yes, intercalation is 2
why a lithium ion battery works.
3 CHAIR PETTI: Exactly.
4 MR. C. CHEN: Correct. You are right.
5 Yes, you are absolutely right. So, that's why your 6
battery will not last forever, and in and out, in and 7
out, or maybe many times. Eventually, the graphite 8
used in the battery will fall apart. It will lose all 9
the electrical connectivity. That's why the battery 10 will die. That's the intercalation, you're absolutely 11 right.
12 CHAIR PETTI: I've always believed that 13 any cesium in TRISO particles is actually intercalated 14 in the graphite layer, in the pyrocarbon in the buffer 15 layers, that that's the mechanism. Hard to prove, but 16 just the analogy with lithium in graphite. So, 17 there's a huge amount of literature on it.
18 But what you're saying is, independent of 19 the ability to wet and infiltrate, just chemically, it 20 doesn't happen?
21 MR. C. CHEN: Yes. That is, most of the 22 time the reaction does not happen.
23 CHAIR PETTI: Correct. Okay.
24 MR. C. CHEN: Okay. So, if there's no 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 further questions, then let's move on to the next 1
slide, please.
2 Margaret? All right. Okay, thank you.
3 So, the next topic is about oxidation.
4 The oxidation may occur at the top of the reflector 5
and where the inert gas, it's the gas in the inert gas 6
space. But, in the air ingress event, this can 7
potentially reduce -- have oxidation occur, for the 8
whole reactor, only on this section.
9 So, we will assess the effect of oxidation 10 and we'll measure the oxidation kinetic parameter of 11 this ET-10 graphite, and we're also determining the 12 weight loss with the strength. So, you would 13 determine how much weight loss will -- how much 14 strength, it will actually cause so much strength 15 reduction. And then, we'll determine the oxidation 16 profile. So, you're talking about the oxidation 17 penetrating 5 millimeters or 10 millimeters, or so 18 forth, something like that.
19 The oxidation, and also another thing we 20 are looking at is the graphite submerged in the Flibe, 21 It will also be assessed to determine if this 22 oxidation occurs for the graphite submerged in the 23 molten salt. And then, if we determine there is 24 oxidation going on there, we will associate a 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
41 strength; reaction will be further assessed.
1 So, that's about oxidation.
Any 2
questions?
3 CHAIR PETTI: Yes, just a question. You 4
know there's been a tremendous amount of work done in 5
this area for the other graphite grades.
6 MR. C. CHEN: Yes.
7 CHAIR PETTI: Do you anticipate ET-10 to 8
have, say, different oxidation kinetics than IG-110?
9 I would expect them to be kind of similar.
10 MR. C. CHEN: Well, I will say the trend, 11 more or less, is similar, but the degree of oxidation 12 and the kinetics parameter will be grade-dependent.
13 There's a lot to do with the pore structure and the 14 starting material and a purity extraction.
15 CHAIR PETTI: Right. Okay.
16 MR. C. CHEN: Any further questions? If 17 no, I am going to pass it back to Margaret.
18 (No response.)
19 MS. ELLENSON: Okay, great.
20 So, just to summarize, the graphite 21 material qualification report will largely follow the 22 ASME BPV Code with a few limited departures, which I 23 know that the NRC staff will talk about further, and 24 we'll talk about further in our closed session.
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42 Our qualification plan will use both a 1
combination of existing data and data from new tests, 2
and seismic qualification is outside of the scope of 3
this particular Topical Report.
4 There's a few limitations that we have 5
documented in this Topical Report. They're largely 6
related to the need to finalize the design to be able 7
to have those design inputs for the qualification 8
program itself.
9 So, for example, the height of the vessel 10 relates to the infiltration threshold pressure.
11 Irradiation creep data relates to the component 12 lifetime or the fluence in the final design, whether 13 or not there are freeze (audio interference) -- so, 14 freeze-thaw cycles, just for example are precluded by 15 design for our -- are not within the design basis of 16 a KP-FHR.
17 Other things about the interactions 18 between any secondary loops, like an intermediate salt 19 loop, an interfacing system, and then, coincident 20 effects of irradiation and oxidation, which, again, 21 that is a design feature. It's a design lever that we 22 can pull to be able to minimize that effect.
23 There's also future testing that we're 24 going to do related to demonstrating an irradiated 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 fatigue response, following trends from existing 1
- datasets, and
- then, demonstrating in a
final 2
application that we are able to develop this envelope 3
for a qualification bound for irradiated properties.
4 And lastly, to provide a design-specific analysis for 5
weight loss due to oxidation.
6 So, those were the limitations that we had 7
identified, and I believe that this is our last slide 8
for the open session.
9 CHAIR PETTI: So, I had a broader 10 question, and maybe you can defer to the closed 11 session.
12 But there's a discussion about the quality 13 program that you plan to use that appears to be in 14 conflict to the quality program that Div 5 expects.
15 MS. ELLENSON: Sure.
16 CHAIR PETTI: Can you talk about that?
17 MS. ELLENSON: Yes. So, Div 5 is really 18 written for a power reactor application, and there are 19 quality standards and a quality program that we are 20 developing for a power reactor application.
21 In the NRC regulations, there are 22 different standards that applied to a non-power 23 reactor. So, for our test reactor application, we 24 expect to follow the NRC guidance about quality 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 assurance programs, and I believe that that is written 1
up in the introduction of the Topical Report, how we 2
will handle pulling the data into the appropriate 3
quality assurance program related to what type of 4
application we're going to use.
5 CHAIR PETTI: Okay. That's what I guess 6
I was confused about. If you take data that we'll 7
hear about in the closed session and you're using the 8
test reactor quality standards, how can you use that 9
data for a potential power reactor Div 5 application, 10 given it's not the same? I didn't see that discussed 11 in the Topical, but maybe I missed it.
12 MS.
ELLENSON:
Yes.
So, the 13 qualifications will be separate and distinct between 14 the test reactor and the power reactor. We will be 15 using the quality assurance standards for a power 16 reactor for any data that we use to rely on for a 17 power reactor application. So, if it happens to be 18 the same dataset, we would do what we would need to do 19 under a quality assurance program to be able to pull 20 that data under the appropriate quality assurance.
21 CHAIR PETTI: Okay. So, when you get data 22 that could apply to both Hermes and the power reactor, 23 you're going to default to the power reactor QA 24 standards?
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45 MS. ELLENSON: Not necessarily. There are 1
methods that you can use to be able to pull data into 2
a quality assurance program. There may be some 3
methods that are appropriate for a non-power reactor 4
quality assurance program and different methods that 5
one might use for a power reactor quality assurance 6
program. So, it depends on which application, and 7
which application we are using the data for would 8
drive the methods that we would need to use to do 9
quality assurance for that data.
10 MEMBER BALLINGER: This is Ron Ballinger.
11 I'm getting ahead of ourselves, but I 12 think, on the metals side, there are words in there to 13 the effect that the QA and data overall circumscribe 14 the test reactor. In other words, they're going to 15 use mostly qualified data for the power reactor, but 16 that data will automatically work for the test 17 reactor. Am I wrong?
18 MS. ELLENSON: Well, I can't speak for the 19 Metallics Topical Report. I'm not the lead for that 20 one. But, for the Graphite Topical Report, where data 21 is already Q, for example -- there's a great deal of 22 data out there that was already generated under a Q-23 level program -- obviously, that data could be 24 directly applied to both a power reactor or a test 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
46 reactor. I was speaking to the situation where data 1
may not yet be Q and we may need to pull it under our 2
quality assurance programs. I would speaking to what 3
we would do in that circumstance.
4 MEMBER BALLINGER: Thanks.
5 CHAIR PETTI: So, these are radiation that 6
are being talked about for the high fluence to 7
determine turnaround, et cetera, et cetera. Those 8
really aren't Hermes issues. Those are power reactor 9
issues.
10 MS. ELLENSON: Yes.
11 CHAIR PETTI: So, you would conduct those 12 radiations under NQA-1? Is that --
13 MS. ELLENSON: Yes. So, a power reactor 14 application that would want to have a component 15 lifetime that would go past turnaround, yes, we would 16 do those tests. We would generate that test data 17 under an NQA-A program.
18 CHAIR PETTI: I mean, I guess I may want 19 to explore this with the staff, but I've always -- my 20 experience, in talking to the quality people that I 21 had interface with was always two flags of quality.
22 You end up always in a problem somewhere. There will 23 be something. What you don't want is you spent the 24 time, you spent the money under the test reactor QA to 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 get some data, and then, for some reason, they say, 1
no, that's not good enough for the power reactor. And 2
you have to go back and do it all over again. And 3
that's what I'm hoping doesn't happen.
4 MS. ELLENSON: Yes. Yes, and the data 5
that I'm talking about is not necessarily new data 6
that would be generated, but historical data that we 7
want to bring under --
8 CHAIR PETTI: Okay. Yes, historical data 9
I can understand you can, yes, you can pull stuff.
10 MS. ELLENSON: Uh-hum. You can use 11 different methods.
12 CHAIR PETTI: Right. That I understand, 13 right.
14 MEMBER BALLINGER: For the benefit of the 15 other members, can you tell us what turnaround is?
16 MS. ELLENSON: Oh, maybe I could have 17 someone else speak to that, our radiation expert.
18 MEMBER BALLINGER: Okay. It's a term of 19 art.
20 MS. ELLENSON: Yes. So, when graphite is 21 irradiated, the fast neutrons lead to dimensional 22 change. The graphite starts to shrink, and then, 23 expands and gets back to its initial density. The 24 point at which the shrinkage is maximum is called 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
48 "turnaround." And when the graphite gets back to its 1
initial dimension or density, it's called "crossover."
2 MEMBER BALLINGER: Thanks. I'm sure now 3
everybody knows.
4 MEMBER KIRCHNER: Well, I think the 5
important thing, Ron, is that -- this is Walt -- is 6
that, you know, they stay below that fluence for the 7
Hermes Test Reactor. It becomes a lifetime issue for 8
the power reactor.
9 CHAIR PETTI: Right, and there's a big 10 concern, historically -- I'm saying go back 20-30 11 years --
12 MEMBER KIRCHNER: Yes.
13 CHAIR PETTI: -- nobody designed reactor 14 cores that went beyond turnaround.
15 MEMBER KIRCHNER: Exactly.
16 CHAIR PETTI: They always fitted to a sort 17 of limit.
18 MEMBER KIRCHNER: Yes.
19 CHAIR PETTI: Now, there's discussions 20 about, well, maybe we can go that way, as long as --
21 you know, between that and where your dimensional 22 change goes back to zero, can you take advantage of 23 that because it gives you greater lifetime, et cetera, 24 et cetera?
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49 MEMBER KIRCHNER: Yes.
1 CHAIR PETTI: And that's a big discussion 2
with people who want to use graphite in cores because 3
it's expensive, et cetera, et cetera.
4 MEMBER KIRCHNER: Right.
5 CHAIR PETTI: Yes.
6 MEMBER KIRCHNER: And there are secondary 7
issues that the members would be aware of, and that is 8
things like, if you're putting control rods into the 9
reflector, that becomes one of the issues you have to 10 demonstrate that you're not going to interfere with, 11 create a blockage --
12 CHAIR PETTI: Yes.
13 MEMBER KIRCHNER: -- in the shutdown 14 mechanisms, as an example.
15 CHAIR PETTI: Make sure the holes are 16 where you think they are.
17 MEMBER KIRCHNER: Yes, and they're still 18 straight.
19 CHAIR PETTI: Right. Exactly.
20 I had, again, another question, but it may 21 be more appropriate for the closed session.
22 I've actually looked at a lot of graphite 23 stuff over the years, and there's always properties 24 and, you know, there's against the grain, through 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 grain, with the grain, et cetera, et cetera. You get 1
all these material properties.
2 And what I've never fully understood --
3 and I think it depends on each designer -- how you 4
take that data and actually use it in the 5
thermomechanical analysis. Do you pick the most 6
conservative number for each material property, so 7
that you know you're conservative? Or do you try to 8
get more sophisticated in using these different 9
anisotropic values in your thermomechanical analysis?
10 MR. C. CHEN: I can briefly discuss a 11 little bit. So, to clarify, yes, you're right, many 12 graphite, it's not anisotropic material. You have a 13 with-grain and against-grain direction property. It's 14 up to the designer how to use it.
15 And so, we know the property just, for 16 example, some reactivity, and the with-grain is always 17 higher than against-grain. So, we want to use, take 18 advantage of this kind of a property, we can design 19 this way, but I think it is more a design question.
20 CHAIR PETTI: Yes. Because, then, you 21 have to know that all the grains are with-grain in one 22 direction, and it gets complicated, is what I always 23 thought.
24 MR. C. CHEN: Yes. And so, that's why, 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 when we measure the property, we will make sure all of 1
the property in both directions.
2 CHAIR PETTI: Right.
3 Okay. Any other questions, Members? If 4
not, we'll go over to staff.
5 (No response.)
6 Okay. Thank you, Kairos.
7 Let's get the staff presentation now.
8 MR. RIVERA: All right. This is Richie.
9 Okay, the safety presentation now. Let me switch to 10 ours.
11 Just to confirm, can --
12 CHAIR PETTI: I can see the slides.
13 MR. RIVERA: Sorry, I'm trying to -- give 14 me one brief second, please.
15 (Pause.)
16 Weidong, can you confirm if you can see 17 the screens?
18 MR. WANG: Yes.
19 MR. RIVERA: I'll switch to full screen in 20 a second. Okay.
21 Sorry about that.
22 I will pass on the mic to Alex Chereskin, 23 who is the lead reviewer for this Topical Report.
24 MR. CHERESKIN: All right. Good morning, 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 everyone. This is Alex Chereskin.
1 First, I would like to confirm that you 2
guys can hear me and that I'm speaking loud enough 3
into the microphone.
4 CHAIR PETTI: No problem. We can hear 5
you.
6 MR. CHERESKIN: Great. Thank you.
7 So, as Richie said, my name is Alex 8
Chereskin, and I'll be presenting the NRC staff review 9
of the Kairos Graphite Qualification Topical Report 10 today. I'm also joined by Matt Gordon and Meg 11 Audrain, who were also technical reviewers on the 12 review of this Topical Report.
13 Next slide, Richie.
14 Kairos Power requested a review and 15 approval on the Topical Report related to graphite 16 material qualification for the KP-FHR design. And as 17 noted earlier, this qualification applies to the 18 structural graphite only.
19 In general, Kairos proposed to qualify its 20 graphite consistent with the NRC staff-endorsed ASME 21 Code,Section III, Division 5, with deviations that 22 were noted in the Topical Report and evaluated by the 23 NRC staff.
24 This qualification plan applies to both 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 power and non-power test reactor designs, with 1
differences that were, again, described in the Topical 2
Report and evaluated by the NRC staff.
3 One thing to note is that the NRC staff's 4
review focused on evaluating the qualification program 5
against applicable requirements from Section III and 6
Division 5. And because we were evaluating the 7
qualification program, this is not an evaluation of 8
things like component design and calculating a 9
probability of failure of graphite components.
10 The staff's review focused on the overall 11 qualification framework, and this includes evaluation 12 against Section III, Division 5, requirements that are 13 being endorsed in Regulatory Guide 1.87, Revision 2, 14 as Bill noted earlier; use of existing graphite 15 qualification data, unirradiated graphite testing --
16 or radiation testing for graphite, oxidation testing, 17 and molten salt testing.
18 Richie, next slide, please.
19 This slide contains the regulatory basis 20 for the NRC staff review. Portions of the regulatory 21 basis include the sections from Part 50 and 52 related 22 to information that is required to be provided in 23 licensing applications, and information related to the 24 graphite material properties fits that and will need 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 to be supplied as part of a license application.
1 The NRC staff also evaluated the 2
qualification program against KP-FHR PDC that had been 3
previously heard by the NRC staff in KP-TR-003-NP-A.
4 And as shown below, there are a few KP-FHR PDC that 5
rely on graphite components to be met.
6 The first one is KP-FHR PDC 1, which is 7
Quality Standards and Records, and that requires SSCs 8
that are safety-significant to be designed to quality 9
standards commensurate with safety significance. In 10 this case, we're looking at ASME Code,Section III, 11 Division 5.
12 PDC 34, the Residual Heat Removal, and 13 PDC 35, which is Passive Residual Heat Removal, which 14 requires systems remove residual heat, and graphite 15 components, as discussed earlier, need to maintain a 16 structural integrity in order to maintain the physical 17 geometry of the core, in order to support the core 18 cooling.
19 Additionally, there is KP-FHR PDC 74, 20 which is the Reactor Vessel and Reactor System 21 Structural Design Basis, and this requires that the 22 reactor vessel system supports the integrity of the 23 graphite during postulated accidents in order to 24 ensure geometry for passive heat removal, and also, to 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 allow sufficient insertion of the neutron absorbers.
1 Next slide, please.
2 So, this slide covers the NRC staff 3
evaluation of the proposed qualification of 4
unirradiated graphite properties in the Kairos Topical 5
Report. The NRC staff found that the proposed testing 6
plan will satisfy the requirements of Section III, 7
Division 5, and the requirements in the ASME Code 8
include HHA-2210, 3100, and 4100, as these provisions 9
of the Code outline the required properties that need 10 to be measured in order to qualify a grade of 11 graphite.
12 And so, the staff found that the proposed 13 testing program was acceptable because the properties 14 required by HHA-III-3100, as-manufactured graphite, 15 will be tested as part of the unirradiated testing 16 program with appropriate temperature intervals that 17 meet Code requirements.
18 Additionally, staff found this approach 19 acceptable because the sample size and cutting 20 patterns that are in the proposed qualification 21 program are consistent with HHA-III-4100, as-22 manufactured graphite.
23 Kairos Power did propose two deviations 24 from the Code requirements which the NRC 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
56 evaluated.
1 The first one is to test certain 2
parameters at room temperature. The staff found this 3
acceptable, as it is conservative, because, for 4
unirradiated graphite, the properties listed will 5
improve as temperature increases.
6 The second deviation proposed by Kairos 7
Power is to not test fracture toughness. And the 8
Topical Report states that Kairos will not rely on 9
this to demonstrate that graphite components can 10 perform their safety functions and that the damage 11 tolerance discussions are outside the scope of this 12 Topical Report.
13 The staff found this acceptable, subject 14 to Limitation Condition No. 7 in the Topical Report, 15 which states that Kairos Power must demonstrate how 16 full acceptance is performed without the fracture 17 toughness of graphite.
18 And so, the last bullet on this slide --
19 oh, sorry, there's one more bullet there.
20 In addition, in the unirradiated testing, 21 Kairos Power stated that fatigue testing will be 22 performed. This is consistent with HHA-3140 and the 23 ASME Code, which states that fatigue shall be 24 considered in a graphite deployment design.
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57 The staff found it acceptable to perform 1
the low cycle fatigue testing. These will provide the 2
data needed to design graphite components against the 3
effects of fatigue, consistent with HHA-3140. And the 4
staff found it acceptable to use the historical data 5
trends, subject to that limitation and Condition 2.a, 6
which would require Kairos to perform their low cycle 7
fatigue testing and demonstrate that the ET-10 8
graphite follows the same trends as the graphite cited 9
in the Topical Report.
10 In addition, Kairos proposed to use 11 ASTM D7219 in order to guide their purity standards, 12 which is consistent with Section III, Division 5, HHA-13 I-1110, "Material Specification."
14 Kairos Power also noted that they will 15 define the graphite specification needed for the KP-16 FHR technology based on the requirements of the 17 graphite components in that specific design.
18 Are there any questions on this slide 19 before we move on?
20 CHAIR PETTI: Yes, I had a question on the 21 fracture toughness limitation. I think I followed the 22 logic in the limitation, which is, when one does 23 inspections and sees a defect, a flaw, usually, one 24 uses the fracture toughness as part of the evaluation 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 to figure out if the flaw is significant or not.
1 Was there more beyond that than what's 2
actually written there? I mean, are there other 3
techniques that one can use without using fracture 4
toughness that you guys were aware of?
5 MEMBER BALLINGER: Yes, this is a question 6
I had, too. And I was going to reserve it for the 7
closed session. But are they measuring the Weibull 8
modulus of this stuff? That's another way to sort of 9
get --
10 MR. CHERESKIN: Sure.
11 MEMBER BALLINGER: -- at the issue of 12 fracture toughness, and it's an easier measurement to 13 make.
14 CHAIR PETTI: I can tell you that it can 15 be done. It's been done for the historic grades --
16 MEMBER BALLINGER: Yes.
17 CHAIR PETTI: -- all the work that INL and 18 Oak Ridge have done for NGNP, yes.
19 MEMBER BALLINGER: Yes.
20 MR. CHERESKIN: I'll try to address the 21 question here, and if needed, we can talk more, I 22 guess, about the specifics of testing in the closed 23 session.
24 But, in general, the Topical Report did 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 not provide, I'll say, the final disposition of how 1
this would be performed, although there is a very 2
brief discussion about damage tolerance, which is a 3
term that kind of came out of the U.K. experience with 4
the gas reactors, finding that graphite performance 5
could still perform their safety functions, even given 6
extensive cracking. So, there is some information 7
that is available to show that it may be possible to 8
demonstrate components can perform their safety 9
functions, even with cracks in the component.
10 CHAIR PETTI: Okay. Keep going, I guess.
11 MEMBER KIRCHNER: Dave?
12 CHAIR PETTI: Yes?
13 MEMBER KIRCHNER: Dave, this is Walt.
14 CHAIR PETTI: Go ahead.
15 MEMBER KIRCHNER: On the purity standards, 16 now, normally, for the gas-cooled reactors, it's more 17 a question of neutronics. But here, the purity 18 standards would be a concern if you had contaminants 19 getting into the Flibe coolant system.
20 How did the staff look at that? Did you 21 look at it from a chemical standpoint or from a 22 neutronics standpoint?
23 MR. CHERESKIN: Yes, just to clarify, when 24 you're talking about impurities getting into 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
60
- coolant, is that a
reference to potentially 1
interacting with what is present in the graphite?
2 MEMBER KIRCHNER: Yes, versus neutronic 3
considerations, uh-hum. Normally, like back in the 4
HDGR programs, you were worried, especially if you 5
had a solid core, not a pebble-bed core, you were 6
worried about the boron equivalent of the contaminants 7
that are in the graphite, as-manufactured. Here, 8
there's the potential for different considerations 9
like the coolant interaction with the contaminants.
10 MR. CHERESKIN: And this has also been the 11 NRC staff evaluation. But the purity limits that are 12 in the ASTM standard, you know, they do include like 13 things such as ash content and, also, boron 14 equivalency. And those would provide some assurance 15 that those limits are reasonable, when you consider 16 like their potential to accelerate oxidation of the 17 graphite.
18 MEMBER KIRCHNER: Okay. All right. It's 19 a different look at the issue of contaminants vis-a-20 vis the historical concerns for gas-cooled reactors.
21 CHAIR PETTI: Well, my understanding is 22 just that this whole area, these graphites that they 23 make today are just so much better than what were 24 made, you know, 25-30 years ago for like Fort St.
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61 Vrain. The technology, because graphite is used in 1
other industries, has really improved.
2 And I can remember having big discussions 3
about what the purity specification was for putting in 4
an irradiation test, and the glow discharge mass spect 5
show stuff was really clean compared to what people 6
remember --
7 MEMBER KIRCHNER: Yes, my experience is 8
dated and it's H451.
9 CHAIR PETTI: Right.
10 MEMBER KIRCHNER: So, a long way back.
11 Okay. Thank you.
12 MR. CHERESKIN: Okay. If there are no 13 further questions, I think we can move to the next 14 slide.
15 (No response.)
16 Okay. So, okay, I've lost my place here.
17 Okay.
18 This slide continues the NRC staff's 19 evaluation of the unirradiated material properties 20 section of the Topical Report. So, graphite 21 anisotropy, you know, it will occur. All grades will 22 exhibit probably some degree of it. However, the 23 magnitude is grade-dependent, and the mechanical 24 property is also statistical in nature. And because 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
62 the properties will vary both within the billet and 1
between production lots of graphite, the designer will 2
need to account for these variations.
3 The staff had found the Kairos program for 4
intra-billet variability acceptable because their 5
unirradiated qualification plan is consistent with the 6
sample size and cutting patterns within HHA-III-4000, 7
and that provides reasonable assurance that intra-8 billet variation can be quantified and factored into 9
the graphite component design.
10 Additionally, as stated in the Topical 11 Report, Kairos Power plans to use lot-to-lot variation 12 data from the graphite manufacturer in order to be 13 able to examine the lot-to-lot variation in graphite 14 properties. And in addition, that data was shown to 15 be consistent with the Appendix C of the Topical 16 Report which discusses how to demonstrate historical 17 data is applicable to the as-manufactured graphite.
18 And that contains some provisions, you know, what 19 would need to be demonstrated to ensure that you can 20 compare those datasets.
21 Are there any questions on this slide?
22 MEMBER KIRCHNER: This is Walt again.
23 Is there a lot of historical data with ET-24 10?
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63 MR. CHERESKIN: So, I am not aware of 1
exactly how much data the manufacturer has.
2 MEMBER KIRCHNER: So, could you just, you 3
know, for the record, just tell us -- say you were 4
using H451 data, which was pretty good graphite in its 5
day. How do you interpolate between that and ET-10??
6 MR. CHERESKIN: So, we would not be --
7 sorry, the intent here is not to use other graphite 8
property data to evaluate that lot-to-lot variation.
9 This would be using the manufacturer's data for the 10 unirradiated properties to determine the variation 11 over time in the production lots of that graphite.
12 The reference to historic data is because 13 there is a Code article that lays out the requirements 14 to use data that may have been collected some years 15 ago, to ensure you can use that and verify it against 16 the recent or current production lots. It was not 17 meant to say that it would be used with another 18 graphite grade.
19 MEMBER KIRCHNER: Okay. I misunderstood 20 that. Thank you for the clarification.
21 MR. CHERESKIN: No problem.
22 All right. I think we can move on to the 23 next slide then.
24 Okay. So, this slide discusses the NRC 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
64 staff's evaluation of -- now, we're getting into 1
Section 4 of the Topical Report, which discusses the 2
graphite qualification program for the irradiated 3
basic properties of the graphite. And when I say 4
that, it means the properties that are not irradiation 5
creep, but, as you can see on this slide, stuff like 6
dimensional change and strength, and whatnot.
7 And the NRC staff found the qualification 8
plan in the Topical Report acceptable because Kairos 9
will use irradiated property data for all the basic 10 properties, consistent with the properties that are 11 required by HHA-2220.
12 Additionally, the Topical Report states 13 that the irradiated properties will bound the 14 qualification envelope of the anticipated temperature 15 fluence profile conditions that will be found in the 16 KP-FHR design. This is supported by NRC staff 17 Limitation Condition 9 which requires Kairos to 18 demonstrate the data will bound the final design for 19 the temperature irradiation envelope, once that has 20 been finalized.
21 In addition, Kairos will use the process 22 described in Appendix B that we were just talking 23 about on the use of historical data to demonstrate 24 that the irradiated property test data is applicable 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
65 to the as-manufactured graphite production lots.
1 And so, part of the ASME Code requirements 2
for demonstrating historical data is applicable, those 3
are found in HHA-5000. And additionally, the proposed 4
process from Kairos Power will demonstrate that the 5
graphite meets the definition of the same grade as 6
found in HAB-9200 of the ASME Code, to confirm that 7
the irradiated test data is applicable to the current 8
production lots.
9 And the final bullet on this slide just 10 touches on some of the limitations and conditions that 11 are applicable to this section, which, again, would 12 require the Applicant Kairos Power to demonstrate that 13 the data bounds the plant conditions; that the data 14 meets applicable QA requirements, and that 15 uncertainties in the irradiated data are accounted for 16 in the design.
17 Are there questions on this slide before 18 we move on to irradiation creep?
19 (No response.)
20 All right. Hearing none, Richie, can you 21 go to the next slide, please?
22 So, this slide and I believe the next 23 slide are going to touch on a topic that was actually 24 the focus of a question earlier. So, covering just 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
66 some background on irradiated graphite behavior, in 1
order to kind of set the stage for the brief 2
discussion.
3 And so, just a little bit of background is 4
that graphite will initially shrink volumetrically 5
with increasing dose, and then, once it hits a point 6
called "turnaround," it expands. And so, that's kind 7
of what we had covered before.
8 The dimension change is also a function of 9
temperature. A higher temperature and you will reach 10 that turnaround point at a lower dose.
11 And so, two other points that the staff 12 wanted to note was that not all components will 13 experience this turnaround point at the same time, as 14 you will have, likely, a gradient for flow temperature 15 and fluence across the scope of your graphite 16 components.
17 And one of the reasons why turnaround is 18 important is because that interface within a component 19 of where you have volumetric densification and 20 expansion may cause cracking at that location.
21 And so, on the next slide -- Richie, if 22 you would go to that -- the staff had just put 23 together a quick diagram to kind of show what 24 turnaround looks like as a function of temperature and 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
67 fluence.
1 And you can see where those red and blue 2
arrows are. That just demonstrates the change from 3
volumetric densification to expansion. And we just 4
kind of wanted to provide that as a visual in order to 5
support the next slide or two.
6 MEMBER HALNON: All right. Just one quick 7
question.
8 After the turnaround point at the bottom 9
part where the arrows are, is there other concerns on 10 the upswing there before you get to, say, zero percent 11 change again that makes the turnaround point even more 12 important than just bottoming out?
13 MR. CHERESKIN: Yes. And so, I think, 14 actually, that's something that we're going to talk 15 about in the next slide or two. So, just to give a 16 preview, I mean, that is probably the area where 17 tertiary creep may start to occur. And so, that's 18 something we're going to discuss a little bit more in 19 either of the next one or two slides, I believe.
20 MEMBER HALNON: All right. I'll sit back 21 and learn then. Thanks.
22 MR. CHERESKIN: If there are no further 23 questions, we can go to the next slide.
24 (No response.)
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68 All right. Hearing none, this slide forms 1
the NRC staff evaluation of the proposed irradiation 2
creep program, qualifications programs, for both the 3
power and non-power test reactor designs.
4 The staff found the proposed qualification 5
plan for the power reactor irradiation creep 6
acceptable because the test program will bound the KP-7 FHR qualification envelope and the number of proposed 8
samples is consistent with other creep experiments.
9 Again, this is subject to some limitations 10 and conditions, and the first one being that Kairos 11 demonstrates that tertiary creep is identified, if it 12 occurs during the creep testing. The data that is 13 obtained from these creep tests is sufficient to model 14 the creep. Again, going back to the bounding 15 qualification envelope, and ensuring that dimensional 16 changes of the irradiated graphite are measured in 17 both the against-and with-grain directions.
18 For the non-power reactor irradiation 19 creep program, there are some differences, and that's 20 what we are going to focus on here. The non-power 21 reactor irradiated creep qualification plan will rely 22 on data from other grades of graphite to develop a 23 creep model.
24 And the NRC staff found this acceptable 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
69 because the quality graphite in the non-power test 1
reactor will not reach turnaround. And so, kind of 2
building off those previous slides, this is important 3
for a couple of reasons.
4 The first being that, after turnaround 5
changes to properties found less predictable and more 6
limiting, and as we discussed earlier, post-turnaround 7
components could be partially in biometric 8
densification and expansion, which may cause some 9
cracks. And additionally, this would be prior to the 10 onset of tertiary creep, which is important because at 11 that point the creep behavior would be changing, and 12 additional data might be needed to accurately model 13 what that tertiary creep looks like.
14 And so, the staff has reasonable assurance 15 that, using the historical data shown in the Topical 16 Report, that a conservative creep coefficient can be 17 determined. And one other reason why the staff found 18 this approach acceptable is because this is just for 19 the non-power test reactor design, which is consistent 20 with the minimum regulation provision in the Atomic 21 Energy Act.
22 And again, this qualification program is 23 subject to certain limitations and conditions in order 24 to have Kairos demonstrate that the creep model 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
70 conservative. The graphite in the non-power reactor 1
design is limited to pre-turnaround, and this is just 2
applicable to the non-power reactor, given that part 3
of the rationale is the minimum regulation clause in 4
the AEA; and also, to demonstrate there's no stress-5 driven failure pre-turnaround.
6 Are there any questions on this slide 7
before I move forward?
8 CHAIR PETTI: Yes. Just as I understand 9
it, once you get beyond turnaround, the issue about 10 whether the graphite is going to start to crack as it 11 swells all depends on what's going on with creep. If 12 creep can take out those stresses, then you reduce the 13 chances of cracks. And so, that's why there's this 14 big focus on trying to understand the creep behavior 15 beyond turnaround. Is that how you guys sort of see 16 it?
17 MR. CHERESKIN: Yes, I think so, and I 18 think that's a good point to raise; that creep is 19 necessary in graphite components, as it will 20 counteract those stresses to counteract the cracking.
21 So, I think we have a common understanding there.
22 CHAIR PETTI: So, in my opinion, this is 23 still sort of an open question with all these 24 graphites post-turnaround, and it's where I think most 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
71 of technology development and research, there is a lot 1
focused on that because it tells you how long your 2
graphite is going to last.
3 So, thanks.
4 MR. CHERESKIN: Yes. Okay. If there are 5
no further questions, I think we can go to the next 6
slide.
7 This slide covers the NRC staff evaluation 8
of the oxidized properties portion of the graphite 9
qualification program. And so, this moves to Section 10 5 of the Topical Report, which describes qualification 11 testing to determine properties of the oxidized 12 graphite. And this was evaluated against ASME Code 13 HHA-III-3200, which described the required properties 14 of oxidized graphite to be measured.
15 And so, the staff found the Kairos Power 16 oxidation program testing acceptable because the 17 proposed testing will cover a range of temperatures 18 for oxidation, including in the kinetic oxidation 19 regime. The reason why I point that out is because, 20 when you are in the kinetic regime, it allows the 21 oxygen to penetrate deeper into the graphite, 22 resulting in a larger strength loss for the amount of 23 oxidation that occurs.
24 Staff also found this acceptable. Like 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
72 Kairos described earlier, they will develop the mass 1
loss versus strength loss relationship for the ET-10 2
graphite and follow ASTM D7042 for oxidation testing.
3 There were two deviations from the Code 4
requirements that Kairos proposed that the staff found 5
acceptable, the first being that they do not measure 6
the unoxidized elastic modulus, as -- sorry. They 7
will not measure the oxidized elastic modulus because 8
using the unoxidized values will yield more 9
conservative values in stress analyses.
10 Additionally, they will not measure the 11 thermal conductivity of the oxidized graphite. My 12 staff found this acceptable because Kairos has stated 13 that it will not credit heat dissipation from the top 14 portion of the reflector in its accident analyses.
15 Are there questions on this slide before 16 we move on?
17 (No response.)
18 Okay. Next slide, please, Richie.
19 So now, we come to the NRC staff 20 evaluation of testing in the KP-FHR environment, which 21 was covered earlier by Kairos in their presentation.
22 So, in the KP-FHR design, the graphite 23 will be exposed to flowing Flibe, as well as moving 24 pebbles, which presents the potential for 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
73 infiltration to the graphite, abrasion, and erosion.
1 ASME Code HHA-3143 requires an evaluation of abrasion 2
if there's relative movement between graphite 3
components and fuel of a pebble-bed reactor.
4 Additionally,Section III, Division 5, 5
requires the designer to consider environmental 6
effects, although, currently, in the Code there are no 7
specific rules for the molten salt environments. And 8
so, the staff evaluated the Kairos-proposed 9
qualification testing program and found it acceptable 10 because it will determine the impacts of abrasion, 11 erosion, and Flibe infiltration. It will address the 12 potential for mass loss due to abrasion and erosion, 13 consistent with HHA-3143. And additionally, it will 14 look at the loss of strength due to Flibe 15 infiltration, as that should be considered in order to 16 be able to assess the structural integrity of graphite 17 components in the KP-FHR design.
18 Are there questions on this slide before 19 we move on?
20 MEMBER KIRCHNER: I have one comment or 21 comment that we can take up in the closed session.
22 But, apropos to the discussion about 23 dimensional change earlier, and the fact that the 24 billets that are going to be produced are not full 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
74 height for the reflector, it means you're going to 1
stack lots. So, one also has to be cognizant that you 2
can have abrasion between the graphite components, not 3
just graphite components in
- fuel, but actual 4
individual components that make up the reflector 5
region of the design.
6 MR. CHERESKIN: Okay. And I think we 7
can --
8 MEMBER KIRCHNER: You could have, for 9
example, you could have flow-induced vibration. That 10 would be a design issue to look at, such that that 11 could cause abrasion of block-to-block, depending on 12 how they're locked together, et cetera.
13 MR. CHERESKIN: Understood, and I think we 14 can discuss that further in the closed session.
15 Are there any further questions before we 16 move to what I believe is the conclusion slide?
17 (No response.)
18 All right. Richie, could you go to the 19 next slide, please?
20 Okay. So, to conclude, the staff reviewed 21 Topical Report KP-TR-014, Revision 4, and concluded 22 that the graphite material qualification program was 23 acceptable for the ET-10 graphite to be used by the 24 KP-FHR design.
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
75 I did just want to reiterate that this was 1
not a review of the overall graphite component design 2
or anything like a performance-monitoring program, as 3
it's focused on the plan to qualify the ET-10 graphite 4
to ASME Code requirements.
5 The staff approval is subject to 6
limitations and conditions that were proposed both by 7
Kairos and the NRC staff. And in addition, this 8
qualification program will meet applicable PDCs that 9
were discussed earlier in part, as the qualification 10 program considers the appropriate conditions --
11 thermal, radiation, oxidation in the molten salt 12 environment -- relevant to the design, and it also 13 meets the Section III, Division 5, rules, with the 14 noted exceptions, which will provide reasonable 15 assurance that the graphite components can be designed 16 to maintain their structural integrity within the 17 qualification envelope.
18 Additionally, I wanted to note that this 19 review was performed to the 2017 edition of Section 20 III, Division 5, which is what is being endorsed in 21 Regulatory Guide 1.87. And so, there is a 22 limitation/condition to say that this review was 23 performed to that edition in the Code and is 24 applicable for that edition.
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
76 And as noted, this will meet the relevant 1
PDC, as the qualification program is consistent with 2
the ASME Code which relates to PDC 1, use of standards 3
appropriate with safety significance of components.
4 And additionally, graphite component integrity is 5
needed to achieve PDCs 34, 35, and 74, as was 6
described earlier, for the functions of passive 7
residual heat removal and insertion of reactivity 8
elements.
9 I believe this is the last slide. So, are 10 there any further questions?
11 CHAIR PETTI: Members, any questions?
12 (No response.)
13 I guess not. So, thank you.
14 MR. CHERESKIN: Okay.
15 CHAIR PETTI: So, we have about eight 16 minutes before we're going to take our break, and 17 then, move into the closed session.
18 So, let me open to the public. Any 19 comments from the public? Unmute yourself, state your 20 name and your comment.
21 (No response.)
22 Okay. I'm not hearing any.
23 Why don't we take a break until half past 24 the hour, and we will start up on the closed Teams 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
77 link at that point. Everybody should have the closed 1
link.
2 Thank you.
3 MEMBER BROWN: So, 11:30, is that what you 4
said, Dave?
5 CHAIR PETTI: Correct. Correct.
6 MEMBER BROWN: Okay.
7 (Whereupon, the above-entitled matter went 8
9 10 11 12 13 14 15 16 17 18 19 20 off the record at 11:08 a.m.
21 MEMBER KIRCHNER: Ron, Walt, I'm here.
22 MEMBER BALLINGER: Ah, okay, Walt.
23 MEMBER DIMITRIJEVIC: I am here, too.
24 MEMBER BALLINGER: And Vesna. Boy, I've 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
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GraphiteMaterialQualificationTopicalReport ACRSKairosPowerSubcommitteeMeeting January12,2023 OPENSESSION
KairosPowersmissionistoenabletheworldstransitiontocleanenergy, withtheultimategoalofdramaticallyimprovingpeoplesqualityoflife whileprotectingtheenvironment.
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3 Introduction
- Thisreportpresentsthe methodsforqualifying structuralgraphiteforusein KPFHRs Qualificationissubjectto theconditionsintopical report
- Thisreportisapplicabletoa testorpowerKPFHR providedthatthereport conditionsaremet 3
3 IdentifyStandard Requirements EvaluateExisting Data IdentifyData Gaps IdentifyMethods toCloseGaps ConductTesting CompleteDesign Demonstrate Qualification ina SafetyAnalysis Report
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4 FissionProductRetentionintheKPFHR
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5 TestandPower KPFHRs
- Thereflectorprovidesa physicalpathwayfor maintainingcorecooling andaphysicalpathway forreactivitycontrol elementinsertions.
- Structuralintegrity ensuresthesafety functionscanbemet.
DowncomerRegion ActiveCoreRegion NegativeReactivityInsertion Graphite Vessel/CoreBarrell ColdLeg FlowtoPrimary HeatTransfer, i.e.,normal heat removal
- nottoscale Heat Removal System ColdLeg
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6 StructuralGraphiteTopicalReportOrganization
- Introduction KPFHRTechnologies RegulatoryInformation
- NuclearGraphite
Background
PhenomenaIdentificationandRanking
- UnirradiatedGraphite
- IrradiatedGraphite
- EnvironmentalCompatibility
- ConclusionsandLimitations
- AppendixA: DataAnalysis
- AppendixB: ETU10Demonstration ofHistoricalDataApplicability
- AppendixC: ParameterEstimation andUncertaintyAssessment
- AppendixD: ComparisonofIG110 andETU10MaterialProperties
- Scope:
Thereportappliestobothatestreactor andapowerreactor.
Seismicqualificationisoutofscopeforthe report.
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7 ASMECodeApplication
- ThequalificationplanfollowstheASMEBPV,SectionIII,Division5code(the Division5Code)
Aportionofthecodespecificallyaddressesgraphitematerials GraphiteQualification SubjectAreas Unirradiated Graphite Irradiated Graphite Environmental Compatibility
- TheDivision5Codeorganizes qualificationintothreeelements:
Characterizationofasmanufactured graphitemechanicalandthermalproperties, Characterizationofgraphiteproperties underirradiation Environmentalcompatibility
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8 BackgroundonGraphite
- Characteristicsofgraphite(vsmetallicmaterial)
Allgraphitegradesare99.9%+ carbon.
Thermallystableininertenvironment,ashighas~3,200°C Mechanicalstrengthincreaseswith temperature Low coefficientofthermalexpansion Anisotropic property Upto~20% porosity Highproperty variability Graphitebilletsizelimitation,difficulttomakelargebillet,superfinegraingraphite.
- Graphitehasbeenused innuclearreactorsfordecadesandextensiveknowledgehas accumulatedaboutthematerial.
Thetopicalreportalsoreferencesrelevantdataaboutothergradesofgraphite,forexampleIG 110(isomolded, superfine)andCGBgrades(extruded,mediumgrain).
- ET10isasuperfinegraingraphite withnearlyisotropicpropertiesthatwillbe qualifiedforuseinaKPFHR.
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EnvironmentalCompatibility GraphiteQualification SubjectAreas Unirradiated Graphite Irradiated Graphite Environmental Compatibility
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10 Chapter5:EnvironmentalCompatibility
- FivephenomenarelevanttointeractionbetweenFlibeandETU10
- PhysicalFactors Infiltration(SeeSection5.1.1) ClosedSession Stress(SeeSection5.1.2)
Graphitereflectorbearsnostructuralloads,unliketheHTGR.
ErosionandAbrasion(SeeSection5.2)
- ChemicalFactors ChemicalcompatibilitywithFlibe(SeeSection5.1.3)
Oxidation(SeeSection5.3)
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11 AbrasionandErosion
- KairosPowerwillperformconfirmatorytribologytestinginFlibe to demonstratethatnosignificantabrasionofthestructuralgraphiteoccursdue tocontactbetweenthereflectorandpebbles NoabrasionexpectedascontactforcesarelowandET10isharderthanthepebbles
- KairosPowerwillperformconfirmatoryerosionexaminationofET10 specimensexposedtolongtermFlibe flowinrotatingcageloop(RCLs):
Erosionisanissueforgascooledreactorswherethegasflowvelocitywas12ordersof magnitudehigherthantheflowvelocityofFlibe inaKPFHR MRSEexperience: Noobvioussignsoferosionongraphitesurfaceafter3yearsofoperation
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12 ChemicalCompatibilitywithFlibe TherearenoknownchemicalreactionsbetweengraphiteandFluorideleading todegradation.
- MSREexperience: Nographitedegradationwasobservedafter3yearsof operation
- Intercalation: TheoryandliteraturedataindicateitcannotoccurunderKPFHR operatingconditions
- Fluorination: KairosPowerhasevaluatedavailableliteratureresultsand found thatalthoughtherewasindicationoftrace surfacefluorination, nobulk fluorinationwasobserved. Bulkfluorinationwouldbenecessaryto affect graphitemechanicalproperties.
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13 Oxidationduringairingressevent
- Oxidationmayoccuratthetopofthereflector(inertgasspace)underair ingressevents,whichcouldpotentiallyreducegraphite strength.
Theeffectofairoxidationwillbeassessed:
MeasuretheET10oxidationkineticparameters Determinetheweightlossvsstrength Determineoxidationdepthprofile
- OxidationofgraphitesubmergedinFlibewillalsobeassessedtodetermineif oxidationoccurs.Ifso,theassociatedstrengthreductionwillbeassessed.
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14 Summary
- ThequalificationplanintheGraphiteMaterialQualificationTopicalReportdescribestheplan toqualifyET10forsafetyrelatedstructuralgraphitecomponentdesignforuseinaKPFHR.
- ThequalificationplanconformswiththeASMEBPV,SectionIII,Division5,Codewithlimited departures.
QuantificationofmechanicalpropertiesasmanufacturedET10atroomtemperaturewhichis conservativeforuseinfuturemodeling.
Fracturetoughnesswillnotbemeasured.
- Thequalificationplanwilluseexistingdataanddatafromnew tests.
Existingdataforbasicirradiationpropertiesandirradiationcreepsupportdesignofagraphitereflector witha4yearlifetime(preturnaroundconditions).
Acombinationofexistingbasicirradiationpropertiesdataandquantificationofexistingirradiation creepdatawillsupportdesignofagraphitereflectorwithalifetimeunderbeyondturnaround conditions.
Acombinationofconfirmatorytestinganduseofexistingdatatodemonstrateenvironmental compatibilityofET10inFlibe.
- Seismicqualificationofthereflectorstructureisoutsidethescopeofthetopicalreport.
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15 Limitations
- Flibe infiltrationisnotaconsiderationfortheKPFHRwhenlimitedtoreactorvesselfluid heightsupto4m.
- Additionalirradiationcreepdatafromtestingof ETU10isnotrequiredwhentheturnaround fluenceisgreaterthanthecomponentlifetime.
- Graphitequalificationpresumesthereflectordoesnotundergofreezethawcycles.
- Afuturelicenseapplicationwillevaluateandjustifytheeffectsofunplannedintermediatesalt infiltrationintotheprimaryloop,ifthereactordesignusesintermediatesaltinaninterfacing heattransferloop.
- Thereflectorstructureandreactorvesseldesignprecludethecoincidenteffectsofoxidation andirradiationsuchthatthestructuralintegrityofthetopofthereflectorwouldbeunableto performitssafetyfunction.
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16 Limitations(continued)
- AfuturelicenseapplicationwilldemonstratethatET10unirradiatedfatigueresponsefollows thesametrendsasH451andPGX.
- Afuturelicenseapplicationthatreliesonthequalificationprograminthisreportwill demonstratethatthedatareliedonforqualificationboundstheanalysisforirradiated properties.
- Adesignspecificanalysisoftheeffectofweightlossduetographiteblockoxidationon structuralintegrityofthereflectormaterialwillbeprovidedinafuturelicenseapplicationthat referencesthequalificationprogramdescribedinthisreport.
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17 Backup: GraphiteManufacturingProcess Source:SGLCarbonwebsite. https://www.sglcarbon.com/en/marketssolutions/material/sigrafineisostaticgraphite/
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 January 12, 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 4
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" Sample size and cutting patterns consistent with HHA-III-4100, As-Manufactured Graphite Conservative to use room temperature strength and modulus because these properties improve with temperature for unirradiated graphite No fracture toughness if Limitation and Condition 7 is met Fatigue testing will be performed Limitation and Condition 2.a
- Use of purity standards in ASTM D7219-08 is consistent with Section III Division 5 HHA-I-1110, Material Specification" The staff finds it acceptable to define the graphite specification for unirradiated and irradiated properties based on the requirements of graphite components in the KP-FHR
Staff Evaluation (Cont'd)
- Qualification of Unirradiated Graphite (Contd)
- Graphite anisotropy is grade dependent and mechanical properties are statistical in nature
- Vary within billet and between lots
- Intra-billet variability of properties consistent with HHA-III-4000
- Lot-to-lot variation will use data from the graphite manufacturer and compare to as-manufactured graphite
- Limitation and Condition 2.b
- Use of historical data consistent with HHA-III-5000, Use of Historical Data 5
Staff Evaluation (Cont'd)
- Irradiated Properties
- HHA-2220, "Irradiated Material Properties" requires measurements for irradiated properties
- Dimensional change, CTE, strength, thermal conductivity, and elastic modulus
- Damage dose and temperature range shall cover qualification envelope
- The NRC staff found the qualification plan acceptable because KP is using irradiated property data from ORNL for all properties above, except creep
- Data will be shown to bound qualification envelope (Limitation and Condition 2.c)
- KP will demonstrate consistency with HHA-III-5000, Use of Historical Data for ORNL test data
- Limitations and Conditions 6, 9, and 10
- Require applicant to demonstrate plant conditions bounded by data, all data meets ASME QA requirements, and that data uncertainties are accounted for in design 6
Staff Evaluation (Contd)
- Irradiated Graphite Behavior
- Graphite initially shrinks volumetrically with increasing dose, and then expands
- Dimensional change also a function of temperature
- Turnaround is the point where contraction turns to expansion
- Not all components will experience turnaround at the same time
- Interface within components of volumetric densification and expansion which may cause cracks 7
Staff Evaluation (Contd) 8
Staff Evaluation (Cont'd)
Power Reactor Irradiated Creep The staff found the proposed testing for irradiated creep acceptable because it will bound the KP-FHR qualification envelope and the number of samples is consistent with other creep experiments (e.g. AGC-3 experiments)
Limitation and Conditions 2.e, 2.f, 8, 9, and 11 Ensure tertiary creep is identified, data is sufficient to model creep, data bounds qualification envelope, and dimensional changes measured in both AG and WG directions Non-Power Reactor Irradiated Creep Data from other grades of graphite will be used to develop a creep model The NRC finds this acceptable All graphite will be pre-turnaround Important because after turnaround changes become less predictable and more limiting Additionally, post-turnaround components would partially be in volumetric densification and expansion which may cause cracks Prior to onset of tertiary creep Reasonable assurance a conservative creep coefficient can be determined Acceptable because non-power reactor minimum regulation consistent with the AEA Limitation and Conditions 2.g, 12.a through e Demonstrate that creep model is conservative, limited to pre-turnaround, applicable to non-power reactor, and demonstrate no stress-driven failure pre-turnaround 9
Staff Evaluation (Cont'd)
- Oxidized Properties
- HHA-III-3200, Oxidized Graphite, requires properties of oxidized graphite to be measured
- Strength, elastic modulus, thermal conductivity
- The staff found the KP oxidation testing acceptable
- Covers a range of temperatures including the kinetic oxidation regime
- Will develop mass vs. strength loss for ET-10 graphite
- Follows ASTM D7542 for oxidation testing
- Acceptable to use unoxidized elastic modulus because it will yield more conservative values in stress analyses
- Acceptable to not measure thermal conductivity of oxidized graphite because KP stated the design will not credit heat dissipation from the top portion of the reflector.
10
Staff Evaluation (Cont'd)
- KP-FHR Environment
- Graphite in the KP-FHR will be exposed to flowing Flibe as well as moving pebbles
- Potential for infiltration, abrasion, and erosion
- HHA-3143, "Abrasion and Erosion," requires an evaluation of abrasion if there is relative movement between graphite components and fuel of a pebble bed reactor
- Section III Division 5 requires designer to consider environmental effects although no specific rules for molten salt environments
- Limitation and Condition 2.h
- The NRC staff found the proposed qualification testing acceptable to determine the impacts of abrasion, erosion, and Flibe infiltration
- Potential mass loss for abrasion and erosion consistent with HHA-3143
- Loss of strength due to Flibe infiltration should be considered in order to assess structural integrity of graphite components 11
12 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.
Does not include review of design, monitoring, damage tolerance, etc.
Subject to NRC staff limitations and conditions KP proposed limitations are necessary and appropriate Will meet applicable PDCs, in part Considers all conditions (thermal, irradiation, oxidation, coolant) relevant to design Meeting Section III Division 5 rules provides reasonable assurance structural integrity is maintained within qualification envelope Limitation and Condition 3 Graphite components will be qualified to ASME Code consistent with PDC 1 Graphite component integrity is needed to achieve PDCs 34, 35, and 74
13 Questions?
References
- B. J. Marsden, M. Haverty, W. Bodel, G. N.
Hall, A. N. Jones, P. M. Mummery & M.
Treifi (2016) Dimensional change, irradiation creep and thermal/mechanical property changes in nuclear graphite, International Materials Reviews, 61:3, 155-182, DOI: 10.1080/09506608.2015.1136460
- Windes, William E., Rohrbaugh, David T., Swank, David W., INL/EXT-19-54726, AGC-Irradiation Creep Strain Data Analysis, Revision 0, July 2019.
14