ML21287A635
| ML21287A635 | |
| Person / Time | |
|---|---|
| Issue date: | 09/08/2021 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| Burkhart, L, ACRS | |
| References | |
| NRC-1635 | |
| Download: ML21287A635 (85) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Docket Number:
(n/a)
Location:
teleconference Date:
Wednesday, September 8, 2021 Work Order No.:
NRC-1635 Pages 1-57 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W., Suite 200 Washington, D.C. 20009 (202) 234-4433
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1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 UNITED STATES OF AMERICA 1
NUCLEAR REGULATORY COMMISSION 2
+ + + + +
3 688TH MEETING 4
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5
(ACRS) 6
+ + + + +
7 OPEN MEETING 8
+ + + + +
9 WEDNESDAY 10 SEPTEMBER 8, 2021 11
+ + + + +
12 The Advisory Committee met via Video-13 Teleconference, at 8:30 a.m. EDT, Matthew W. Sunseri, 14 Chairman, presiding.
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
2 COMMITTEE MEMBERS:
1 MATTHEW W. SUNSERI, Chairman 2
JOY L. REMPE, Vice Chairman 3
WALTER L. KIRCHNER, Member-at-large 4
RONALD G. BALLINGER, Member 5
VICKI BIER, Member 6
DENNIS BLEY, Member 7
CHARLES H. BROWN, JR. Member 8
VESNA B. DIMITRIJEVIC, Member 9
GREG HALNON, Member 10 JOSE MARCH-LEUBA, Member 11 DAVID A. PETTI, Member 12 ACRS CONSULTANT:
13 STEPHEN SCHULTZ 14 DESIGNATED FEDERAL OFFICIAL:
15 WEIDONG WANG 16 ALSO PRESENT:
17 BLAISE COLLIN, Kairos Power 18 DARRELL GARDNER, Kairos Power 19 BRANDON HAUGH, Kairos Power 20 DUKE KENNEDY, NRR 21 SCOTT MOORE, Executive Director, ACRS 22 RICHARD RIVERA, Kairos Power 23 JEFFREY SCHMIDT, NRR 24 JAMES TOMKINS, Kairos Power 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
2 Call to Order..................
4 3
Opening Remarks by the ACRS Chairman 5
4 Kairos Topical Report on Fuel Performance....
8 5
Remarks from the Subcommittee Chairman 8
6 Presentation by Kairos Power
....... 10 7
Presentation by NRC Staff......... 42 8
Public Comments (None)
............. 56 9
Committee Comments (None)............ 56 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
4 P R O C E E D I N G S 1
8:31 a.m.
2 CHAIR SUNSERI: Good morning. The meeting 3
will now come to order.
4 This is the first day of the 688th meeting 5
of the Advisory Committee on Reactor Safeguards. I'm 6
Matthew Sunseri, the Chair of the ACRS.
7 I'll now call the roll to verify a quorum 8
and that communications are open.
9 Let's start with Ron Ballinger.
10 MEMBER BALLINGER: Here.
11 CHAIR SUNSERI: Vicki Bier? Vicki, are 12 you there? Unmute.
13 MEMBER BIER: Sorry about that. Yes, I'm 14 here.
15 CHAIR SUNSERI: Okay. Dennis Bley?
16 MEMBER BLEY: Here.
17 CHAIR SUNSERI: Charles Brown?
18 MEMBER BROWN: I'm here.
19 CHAIR SUNSERI: Vesna Dimitrijevic?
20 MEMBER DIMITRIJEVIC: I'm here.
21 CHAIR SUNSERI: Greg Halnon?
22 MEMBER HALNON: Here.
23 CHAIR SUNSERI: Walt Kirchner?
24 Walt is having some communication troubles 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 today. I'm sure he'll be joining us as soon as he 1
can.
3 MEMBER MARCH-LEUBA: Here.
4 MEMBER KIRCHNER: Matt, I'm here. Sorry.
5 CHAIR SUNSERI: Okay, good. Great. Got 6
you.
7 Dave Petti?
8 MEMBER PETTI: Here.
9 CHAIR SUNSERI: Joy Rempe?
10 MEMBER REMPE: Here.
11 CHAIR SUNSERI: And myself.
12 So, we have all members present and 13 communications were loud and clear. So, we have a 14 quorum.
15 The ACRS was established by the Atomic 16 Energy Act and is governed by the Federal Advisory 17 Committee Act. The ACRS section of the U.S. NRC 18 public website provides information about the history 19 of the ACRS and provides documents such as our 20
- Charter, Bylaws, Federal Register notices for 21 meetings, Letter Reports, and transcripts of all full 22 and subcommittee meetings, including all slides 23 presented at the meetings. The Committee provides its 24 advice on safety matters to the Commission through its 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 publicly available Letter Reports.
1 The Federal Register notice announcing 2
this meeting was published on August 16th, 2021, and 3
provided the agenda and instructions for interested 4
parties to provide written documents or requests and 5
opportunities to address the Committee.
6 The Designated Federal Officer for this 7
meeting is Mr. Weidong Wang.
8 During today's meeting, the Committee will 9
consider the following:
10 The first topic is the Kairos Topical 11 Report on Fuel Performance.
We'll have a
12 presentation, and
- then, we will have report 13 preparation activities. And I do note that portions 14 of the Kairos session will be closed to discuss and 15 protect information designated as proprietary.
16 And then, in the afternoon, we will 17 continue preparations for our briefing to the 18 Commission which is scheduled for October.
19 The phone bridge line has been opened to 20 allow members of the public to listen in on the 21 presentation and Committee discussions. We have 22 received no written comments or requests to make oral 23 statements from members of the public regarding 24 today's session.
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 There will be an opportunity for public 1
comment, and we have set aside time in the agenda for 2
comments from members of the public attending or 3
listening to our meeting. Written comments may be 4
forwarded to Mr. Weidong Wang, the Designated Federal 5
Officer.
6 A transcript of the open portions of the 7
meeting is being kept. So, it is requested that 8
speakers identify themselves and speak with sufficient 9
clarity and volume, so that they can be readily heard.
10 Additionally, participants should mute themselves when 11 not speaking.
12 So, I just wanted to open by saying it's 13 been a while since we've gotten together. July was 14 our last Committee meeting. We did have a 15 subcommittee in September. So, I do appreciate 16 everyone getting back together here.
17 And I want to acknowledge everybody's 18 patience for us and the early hour of this meeting.
19 We had intended that this meeting would be an in-20 person meeting. When we scheduled it as such, 21 pandemic trends were looking beneficial to support in-22 person meetings, which we were greatly anticipating 23 and looking forward to. However, in light of the 24 public health trends, we could not in good conscience 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 schedule travel amongst the escalating rates of the 1
virus transmission. So, we decided to postpone in-2 person meetings, not indefinitely, but we'll talk more 3
about this during our P&P session. But it's not 4
likely to get back together until December, even if 5
that is supported by the public health trends.
6 Anyway, that's all I wanted to say. So, 7
at this point in time, I will ask Member Petti if he 8
is ready to start the Kairos sessions, and turn it 9
over to Dave.
10 MEMBER PETTI: Thank you, Mr. Chairman.
11 Let's see, would the senior staff like to 12 say something before we pass it over to Kairos?
13 MR. KENNEDY: Yes. Good morning.
14 This is Duke Kennedy. I'm the Acting 15 Chief of the Advanced Reactor Licensing Branch. So, 16 I will give some opening remarks.
17 So, good morning, Mr. Chairman and 18 Distinguished Members of the ACRS. It's my pleasure 19 to be here today to provide introductory remarks on 20 behalf of the Division of Advanced Reactors and Non-21 Power Production and Utilization Facilities in the 22 Office of Nuclear Reactor Regulation.
23 With me today is Mr. Jeffrey Schmidt of 24 the Advanced Reactor Technical Branch, who is the lead 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 technical reviewer and will provide the staff 1
presentation, and Mr. Richard Rivera, providing 2
project management support, and other members of DANU.
3 The staff is looking forward to 4
discussions with and feedback from the ACRS members 5
today on the Draft Safety Evaluation of the Kairos 6
Power Topical Report titled, "KP-FHR Fuel Performance 7
Methodology." Staff briefed the Kairos Power 8
Licensing Subcommittee on this report on July 6th, 9
2021, as was mentioned.
10 And as you will hear, this Topical Report 11 is important for Kairos' safety case and is related to 12 other Topical Reports, such as the Mechanistic Source 13 Term and Fuel Qualification Reports.
14 We note that this meeting is the third 15 time staff and Kairos Power have had the opportunity 16 to brief the ACRS on Kairos Power Topical Reports, and 17 the staff appreciated the helpful comments from the 18 ACRS on Topical Reports covering reactor coolant, 19 scaling methodology, and licensing modernization, 20 project implementation, and the draft of the report 21 that's the subject of today's meeting.
22 The staff looks forward to continuing to 23 work with the Chairman and the rest of the ACRS 24 members and staff as we complete the reviews of more 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
10 Kairos Power Topical Reports and review license 1
applications for facilities that will use the Kairos 2
Power design.
3 We expect to receive a construction permit 4
application for the Kairos Power's Hermes Test Reactor 5
later this year.
6 I'd like to highlight that the working 7
relationship between NRC staff and Kairos Power was 8
excellent. Similar to previous reviews of Kairos 9
Power Topical Reports, the staff has used public 10 meetings as an efficient means for addressing 11 technical issues without the need for extensive 12 interactions via requests for additional information.
13 Finally, I'd like to thank the technical 14 staff from the Advanced Reactor Technical Branch and 15 DANU for their efforts to produce a high-quality Draft 16 Safety Evaluation and the staff from the Office of 17 Research for their valuable support.
18 That concludes my opening remarks, and I 19 guess we'll turn it over to Kairos Power.
20 MR. TOMKINS: Okay. My name is James 21 Tomkins. I'm Kairos Power licensing and focused 22 mainly on Fuel Topical Reports and Chapter 4 of the 23 PSAR.
24 So, we have Blaise Collin, who is one of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
11 our fuel performance experts, who will present an 1
overview of the Topical Report.
2 So, Blaise, I think you're on?
3 MR. COLLIN: Yes, I am on.
4 Good morning, everybody.
5 MR. TOMKINS: So, with that said, I will 6
turn it over to Blaise. He's going to present a high-7 level overview of the Fuel Performance Topical, 8
because we did cover it in pretty substantial detail 9
at the last meeting. And this is a public meeting.
10 So, Weidong, if you can set up Blaise, so 11 that he can share his screen?
12 And, Blaise, go ahead and share your 13 screen and take it away.
14 MR. WANG: Blaise is already as a 15 presenter. So, he can share the screen.
16 MR. TOMKINS: Okay.
17 MEMBER PETTI: We don't see anything yet, 18 Blaise.
19 MR. COLLIN: Good morning, everybody, 20 again.
21 Sorry for the technical blip. The team 22 has asked, when it actually starts, that I share my 23 screen. I am not presenter anymore at the moment.
24 So, we ask the ACRS if they could make me one again.
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 CHAIR SUNSERI: My screen shows you as a 1
presenter. This is Matt.
2 MR. COLLIN: Okay. Now it seems to be 3
working again. I'm not sure what you're seeing. Are 4
you seeing my presentation?
5 MEMBER PETTI: There we go. We can see 6
it.
7 MR. COLLIN: All right. Okay, here we go.
8 All right. Sorry for the technical 9
difficulties.
10 Good morning, Mr. Chairman, and good 11 morning, Members of the ACRS Committee. Good morning 12 to the staff and the public listening in.
13 This will be an overview of our Fuel 14 Performance Methodology Topical Report. We already 15 had an extensive discussion about this Topical Report 16 with the ACRS Subcommittee in early July. This will 17 be a high-level public presentation in which we, 18 obviously, do not disclose any of our proprietary 19 material.
20 So, the Topical Report for October from 21 Kairos Power contains the following introduction.
22 Basically, it covers how we modeled the behavior of 23 TRISO fuel under our KP-FHR conditions, and also 24 discusses how we intend to perform verification 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
13 validation, including answers on the quantification of 1
the fuel performance code which is named KP-BISON.
2 It's the Kairos Powers commercial version of the BISON 3
code developed at INL. And there's a consequence 4
section in the Topical Report that describes exactly 5
how we intend to perform fuel performance analysis 6
with KP-BISON.
7 So, as many of you know, this is just a 8
slide presenting an overview of TRISO fuel behavior 9
when put under neutron flux. A TRISO particle is made 10 out of, in our case, a UCO kernel, which is uranium 11 oxycarbide fuel. That kernel is surrounded by a 12 carbon buffer and three outer coating layers, a 13 silicon carbide layer sandwiched between two 14 pyrocarbon layers.
15 So, all these
- layers, all these 16 constituents have various behaviors. When under flux, 17 the kernel tends to swell outward. The buffer and the 18 PyC layers tend to shrink early during irradiation and 19 reverse to swelling when neutron fluence accumulates.
20 And the SiC layer, which is sandwiched here between 21 the two PyC layers, tends to have pretty much elastic 22 behavior.
23 So, the whole purpose of, I mean, one of 24 the purposes of our fuel performance calculation 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
14 obviously, to ensure the integrity of the fuel when 1
put under the KP-FHR irradiation conditions, and 2
therefore, we need to calculate the elemental changes 3
of all these coating layers and calculate the 4
associated stresses to these dimensional changes.
5 Again, something that is pretty well known 6
by the TRISO community, historically, and more 7
recently with the development of the Advanced Gas 8
Reactor Program by their department of energy, the 9
fuel failure mechanisms have been identified for TRISO 10 fuel, in general, and UCO fuel, in particular. These 11 are listed on the slide.
12 There is a potential pressure vessel 13 failure of TRISO particles that results from 14 increasing internal pressure inside the particle, that 15 pressure coming from fission gas. And in the case of 16 UO2 fuel, it can also come from the formation of 17 carbon monoxide.
18 As I mentioned earlier, the PyC layers 19 tend to shrink early during irradiation, and that 20 could, in particular, lead to the cracking of IPyC 21 layer. That cracking can itself lead to a failure of 22 the silicon carbide layer by, basically, adding 23 additional stress on the silicon carbide layer.
24 Another phenomena that exists between 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
15 IPyC and the SiC is the potential debonding between 1
the two layers that will also put stress on the 2
silicon carbide layer, potentially, again, leading to 3
its failure.
4 There are other phenomena that are 5
specific to UO2, like kernel migrations, where the 6
kernel would migrate towards the SiC layer because of 7
accumulation of carbon monoxide on one side of the 8
layer, the particle pushing the kernel in the other 9
direction. And once the kernel contacts the coating 10 layers, the outer coating layers, it could fail the 11 silicon (audio interference).
12 (Audio interference) attacked by fission 13 products that are, obviously, generated in the kernel 14 or by, in the case of UO2, it could be chemically 15 attacked by carbon monoxide, and that also could lead 16 to its failure when the thickness of the silicon 17 carbide layer gets too thin.
18 At very high temperature, the silicon 19 carbide layer might or would also decompose between 20 its constituent silicon, on the one side, and carbon, 21 on the other side. That only occurs at temperatures 22 above about 2,000 degrees Celsius, so far out of reach 23 of KP-FHR temperatures.
24 And finally, a more recent failure 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 mechanism that was observed by post-irradiation 1
examination of FHR fuel is a fracture of the buffer 2
that could lead to cracking of the IPyC in case the 3
IPyC doesn't debond from the buffer during 4
irradiation. And as we've seen cracking of the IPyC 5
layer could itself lead to failure of the silicon 6
carbide layer.
7 So, these are about half a dozen failure 8
mechanisms that are well identified for TRISO fuel and 9
models for the relevant failure mechanisms relevant to 10 UCO fuel, which is the Kairos Power fuel, and relevant 11 to the irradiation conditions of KP-FHR. So, these 12 relevant failure mechanisms were developed and 13 implemented in BISON and, by extension, in KP-BISON, 14 with the purpose being to predict potential failure of 15 the coating layers, including the SiC layer, and 16 potential subsequent release of fission products from 17 the particle into the fluoride coolant of the KP-FHR.
18 MEMBER MARCH-LEUBA: This is Jose March-19 Leuba.
20 This is a
good exposition of the 21 degradation mechanisms of the kernel. Do you also 22 consider fabrication problems when it came out 23 defective from the factory? How are those considered?
24 MR. COLLIN: Correct. So, we do have 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
17 fuel specification, and they're similar to the actual 1
specification of the AGR program. By fabrication, you 2
can have manufacturing defects. These defects have 3
specifications. So, for instance, you could fabricate 4
particles with defective layers. So, you know by 5
fabrication that some of your particles might have a 6
defective SiC layer or defective PyC layers or a 7
missing buffer.
8 So, you have like a set of defects that 9
were identified by previous TRISO fuel fabricators, 10 including the AGR program. And all these defects have 11 upper allowed limits. So, when we run our 12 calculations for (audio interference) release of 13 fission products, we take into account that, purely by 14 fabrication, some of these particles are potentially 15 already defective. So, it's sort of independent of 16 additional calculations made by KP-BISON.
17 KP-BISON would, basically, tell you if you 18 put intact particles into flux, are they going to keep 19 their integrity or are some of these coating layers 20 failed? But, in addition to these calculations, we 21 have already a small fraction of already-existing or 22 already defective particles, and that is accounted for 23 when we do calculations of release of fission 24 products.
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18 MEMBER MARCH-LEUBA: And that fraction is 1
calculated based on sampling? I mean, it's on quality 2
control? Previous experience? Testing?
3 MR. COLLIN: So, at this moment, because 4
we do not have, well, Kairos has not produced TRISO 5
particles yet. So, at this moment, we are using this 6
specification. And so, we have, for each potential 7
defect, there is an upper limit on the allowable 8
fraction of defects. And we're using these upper 9
bounding values for our calculations in the short 10 term. So, it's short-term calculations.
11 In the
- future, once the fuel is 12 fabricated, it will be characterized and all these 13 defects will be measured as part of the 14 characterization process. So, we will, potentially, 15 we will be able to replace the upper values from the 16 fuel specification by actual measured values from 17 actual fabrication. And obviously, we expect these 18 values to be, these measured values to be smaller than 19 with the specification, and it's the point of the 20 specification to reject every lot whose measured 21 characteristics would be above specification.
22 MEMBER MARCH-LEUBA: Okay. Thank you very 23 much.
24 MR. COLLIN: Sure.
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 MEMBER REMPE: This is Joy.
1 During our Subcommittee open meeting, we 2
talked about the fact that Kairos will still need to 3
get data to show or support any statements that say 4
the coolant is a separate and independent fission 5
product release barrier. Because we don't have, or 6
Kairos doesn't have, data to try and characterize 7
whether there's any chemical attack by the coolant on 8
the various layers of the particle.
9 How will Kairos try and estimate a 10 mechanistic source term when they have so much 11 uncertainty in the timing and magnitude of the fission 12 products released? Because there could be some 13 chemical attack by the coolant on the various layers 14 of the particles.
15 MR. COLLIN: So, at this moment and at 16 this time, I guess we are assuming that there will 17 actually be no interaction between the coolant and the 18 TRISO particles. So, like in our design, in our fuel 19 design, obviously, we do have -- in the pebble form, 20 there's a layer, there's an outer shell that keeps the 21 fuel itself or the TRISO particles separate from the 22 fluoride, from the coolant.
23 And so, we are going to conduct tests --
24 so, these tests are actually already ongoing -- 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
20 basically study the interaction between the fluoride 1
and the graphite and the pebble; check for potential 2
infiltration of the fluoride into the pebble. It is 3
my understanding at this point that we do not have 4
infiltration of the fluoride into the pebble, so that 5
the fluoride is not reaching the TRISO particles.
6 MEMBER REMPE: So, discuss those tests a 7
little bit more here on the record. Are they high 8
temperature or at temperature and at characteristic 9
fluids conditions?
10 MR. COLLIN: So, I would have to let our 11 test expert discuss these. I don't know the details.
12 MEMBER PETTI: Blaise, can I ask you a 13 question?
14 I understand that a white paper on 15 mechanistic source term has come in. And I don't know 16 that my colleagues know that, but I do. We will be 17 reviewing that. Will there be more information in 18 that Topical Report on this sort of topic?
19 MEMBER REMPE: And, in particular, will 20 there be experimental data to support it? Because, 21 yes, I am aware that that paper has come in. And I'm 22 just kind of wondering because, if you don't have data 23 to support it, I'm just thinking, then, you must have 24 to take into account a lot of uncertainties with 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 respect to timing and magnitude.
1 MR. TOMKINS: Yes, Joy, this is Jim 2
Tomkins.
3 I think the question you're asking is 4
really more related to the Fuel Qualification Topical 5
Report, which you will be seeing at some point in the 6
near future.
7 MEMBER REMPE: This Topical Report, in 8
tests -- it is not saying that it's proprietary --
9 indicates that you believe that the coolant is a 10 separate and independent barrier, right?
11 MR. TOMKINS: Yes, it is.
12 MEMBER REMPE: So, I think it's a 13 legitimate question, if you believe that it's a 14 separate and independent barrier, and then, the fact 15 that you're mentioning release of fission products 16 here, to ask. Again, this is a big uncertainty if you 17 don't have data to support the timing and magnitude of 18 the release.
19 And I know the staff has addressed this by 20 not making a finding at this time. But, again, when 21 we have a lot of uncertainties, and we start having 22 the staff review things with a lot of gaps in data, 23 then there will be re-reviews as you're planning --
24 this is like the first step in a multi-stage review, 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 correct?
1 MR. TOMKINS: Correct.
2 MEMBER REMPE: So, I just am curious on 3
what the plan is.
4 MR. TOMKINS: And we have data in the fuel 5
qualification that indicates that infiltration at the 6
pressures we're at, it does not occur.
7 MEMBER REMPE: Okay. So, do you have data 8
that also is considering radiation, temperature, 9
pressure, all of these phenomena together? And it's 10 characteristic of your anticipated burnup that you 11 expect for the fuel?
12 MR. TOMKINS: That I don't know. I don't 13 know what --
14 MR. GARDNER: So, this is Darrell Gardner.
15 I apologize for jumping in.
16 I think we're getting off-topic. The 17 questions being asked really are specific to another 18 Topical Report that hasn't been presented and is still 19 under review by the staff. So, I think we acknowledge 20 the comment, but we're not prepared to have the 21 conversation about fuel qualification and the testing, 22 and all that, today at this meeting.
23 MEMBER REMPE: Okay, I'll wait. And I 24 want to discuss this same issue with the staff.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
23 Thank you.
1 MR. COLLIN: So, if I can just add 2
something to close the discussion in a way.
3 Obviously, development of any type of fuel performance 4
code, you have to go with some assumptions about what 5
you should model and what you can, basically, ignore 6
because of insignificant impact.
7 In the case you mention, the assumption is 8
that the fluoride will not have any deleterious effect 9
on the TRISO particles, which, as we mentioned, is 10 something that is under test. Obviously, if the 11 findings contradict the assumption, we'll obviously 12 have to account for that potential interaction and 13 find a way to develop the appropriate model to include 14 and implement in KP-BISON. But, at this point, we 15 don't have any reason to believe that this will be the 16 case.
17 As you mentioned, this is a multi-step 18 process. We're, basically, at step one of this 19 development of our fuel performance code. We do have 20 a lot of verification and validation still to be done, 21
- and, of
- course, in the
- future, potential 22 implementation of new models, depending on findings on 23 our fuel qualification tests.
24 So, I guess I'll go ahead and discuss our 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
24 fuel performance code KP-BISON. So, Kairos Power, 1
which is on the left side of this slide, we decided to 2
go with UCO TRISO fuel in the fluoride salt-cooled, 3
High-Temperature Reactor.
4 On the other hand, INL, Idaho National 5
Laboratory, with its own funding early on, and then, 6
with support from the MOOSE program, has been working 7
on the development of a high fuel performance code 8
called BISON. And it was our understanding at Kairos 9
Power that there were like a lot of benefits to use 10 BISON as our fuel performance code.
11 So, we developed this collaboration with 12 INL to implement UCO TRISO models in BISON and, like 13 I mentioned earlier, get our own commercial version of 14 the code that's being called KP-BISON to run our fuel 15 performance calculations. So, a few more words about 16 KP-BISON. As mentioned, it was chosen by Kairos Power 17 for its fuel performance code.
18 BISON sits on the MOOSE framework that 19 also has a lot of other "animals" under its framework.
20 There's like computation of benefits from using BISON 21 because of the link to MOOSE. We also leverage 22 extensive developments made by INL and NEAMS, not only 23 for TRISO fuel, but for fuel performance in general.
24 The code is pretty robust.
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
25 So, what we worked on with INL, it's a 1
conversion between Kairos and INL. So, we, basically, 2
wrote the BISON code to like almost, I would call that 3
state of the art in terms of TRISO fuel modeling. So, 4
it's quite a bit of the plan where we imported 5
existing TRISO models into BISON. A lot of that work 6
has been done through an FOA award. So, it's a 7
collaboration; this FOA is a collaboration between 8
Kairos Power and a couple of National Labs on various 9
modeling and simulation aspects, including one on fuel 10 performance that we are working on with INL.
11 And obviously, one of the important 12 benefits of the using BISON as our fuel performance 13 tool is the ongoing support from the BISON team at 14 INL. There's a group of half a dozen INL engineers 15 that are really on top of things and really helping 16 develop this TRISO modeling in BISON to, again, like 17 a state-of-the-art status.
18 So, how does this all work? Well, it's a 19 modeling code. So, there's not many surprises here.
20 On the one hand, we have the geometry show 21 characteristics of the TRISO fuel, as we mentioned 22 earlier when discussing fuel properties. Because of 23 fabrication, all the fuel properties will have 24 distributions. All the properties are computed around 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
26 no known values, but they have tails extending on both 1
sides of their nominal values.
2 We have our KP-FHR with its own 3
irradiation conditions, and KP-BISON takes these as 4
inputs, and together with some of the material 5
properties implemented in the code -- material 6
properties being, for instance, some of, I know we 7
mentioned like a swelling of the kernel, shrinkage of 8
the PyC layers. So, these are material properties 9
that are ones which have correlations that are 10 implemented in the code.
11 So, the
- geometry, the irradiation 12 conditions, they feel into some of these material 13 properties, and with all these input parameters, 14 KP-BISON calculates intermediate results, such as the 15 fuel temperature or temperature in the kernel or in 16 the coating layers, the pressure coming from the 17 fission gas, the displacements of the coating layers, 18 and the stress or stresses that are induced by these 19 displacements.
20 And all these intermediate results serve 21 the purpose of calculating the two figures of merit of 22 KP-BISON which are the probability of failure of the 23 outer coating layers and the release of fission 24 products that can be directly from intact particles 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
27 that could be enhanced by failure of some of the 1
coating layers. So, that's the overall philosophy of 2
these KP-BISON calculations.
3 As I
mentioned
- earlier, the fuel 4
properties or the fuel that is used by Kairos is 5
similar to the fuel developed by the AGR program.
6 Specifically, it is similar to, there's the same or 7
very close specification, so similar to the AGR-2 UCO 8
fuel and the AGR-5/6/7 fuel.
9 The AGR-2 UCO fuel is discussed in a 10 Pre-Topical Report. That's compilation of results 11 from AGR-1 and AGR-2 PIE that was issued, presented to 12 the staff, obviously, and issued in 2020.
13 The AGR-5/6/7 is the latest portion of the 14 AGR irradiation program. The fuel is now out of the 15 reactor and awaiting PIE. And obviously, a lot of 16 information from the AGR-5/6/7 PIE will become 17 available in the upcoming years.
18 So, it's just important to note that we 19 are relying on the fuel that proved to be robust and 20 showed very good performance during the AGR 21 irradiation tests.
22 So, that's two properties are, obviously, 23 one big part of the KP-BISON input parameters. The 24 other inputs are the material properties and 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
28 physical model. So, these two tables summarize, on 1
the one hand, the material properties that are 2
included in KP-BISON for all the constituents of the 3
TRISO particle. So, there's the swelling of the 4
kernel. We have elastic properties. We have 5
properties that depend on the irradiation level, so, 6
basically, on a fast neutron fluence. Obviously, 7
thermal properties, and for the purpose of fission 8
product release, we also have diffusion coefficients 9
for a handful of isotopes and for each of the TRISO 10 constituents as well.
11 And obviously, to capture the physical 12 behavior of the fuel, we rely on a few physical 13 models. Some of these are very basic, like heat 14 equation, something you would find in any fuel 15 performance code.
16 We're looking at things like fission gas 17 release and the pressure that fission gas will create 18 inside a particle, but we also have things that are 19 more particular to TRISO fuel like penetration of 20 palladium into the silicon carbide layers, meaning the 21 migration of palladium from the kernel into the SiC 22 and corrosion of that layer that could lead to its 23 failure.
24 For short-lived fission gas, we're looking 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 at something called release-rate-over-birth-rate 1
ratio, which is just basically a measure of the 2
release of these short-lived fission gases over their 3
production rate.
4 And finally, as I mentioned, we're doing 5
fission product release calculations, and we model 6
fission product transport through these kernel or 7
TRISO constituents using fission diffusions.
8 So, all this makes, all these models and 9
properties implemented in KP-BISON -- so, the existing 10 database, if you will, is pretty well-suited to 11 studying and modeling behavior of UCO TRISO fuel in 12 the KP-FHR. So, we feel that we have a good tool to 13 now perform our fuel performance calculations in the 14 KP-FHR.
15 So, that slide shows our V&V, so 16 verification and validation, plan. We really rely 17 heavily on these two existing benchmarks. One is from 18 the IAEA. It's a benchmark that was already executed 19 by some of, at the time, some of the participating 20 countries.
21 And our purpose is to go through, again, 22 all of these benchmark cases that cover normal 23 operation or operational transients and, also, some of 24 the expected behavior under accident conditions. 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
30 mixes verification and validation cases. And like I 1
said, it's been already run by a lot of different 2
codes. So, it's a very good starting point to make 3
sure that all the TRISO models have been currently 4
implemented in BISON.
5 A
more recent benchmark from the 6
Generation IV International Forum focuses on a couple 7
of, again, more recent experiments; namely, AGR-1, 8
AGR-2, and the European Commission test, HFR-EU1bs.
9 We will also use this benchmark to verify and validate 10 KP-BISON.
11 And in addition to the AGR tests, 12 including in this benchmark, we also intend to extend 13 our ow V&V to what we refer to as INL benchmark.
14 Basically, it means that we want to use even more AGR 15 data to test KP-BISON, specifically, under conditions 16 that are more relevant to or KP-FHR irradiation 17 conditions.
18 So, basically, we want to basically select 19 data that are closer to the KP-FHR envelope. We also 20 want to use the AGR data to look at separate effects, 21 looking at things like swelling of the buffer 22
-- swelling of the kernel, I'm sorry, or shrinkage of 23 the buffer; looking at cracking of the IPyC. Yes, so 24 we will use select data from the AGR PIE to look at 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 separate effects and check that KP-BISON is able to 1
reproduce the PIE data.
2 And actually, we'll rely on other existing 3
data published from German tests or, more recently, 4
tests on the HTR-PM Chinese reactor. So, basically, 5
like the irradiation tests they did on their fuel 6
prior to, obviously, inserting in the HTR-PM core.
7 So, a lot of different things that cover 8
-- we're trying to basically cover and use most of the 9
existing data on TRISO fuel. It's still a small, 10 TRISO is still a small world when compared to light-11 water reactor fuel, but we're trying to be exhaustive 12 in the data that we can use to perform the V&V of 13 KP-BISON.
14 MEMBER REMPE: So, this is Joy.
15 I was just wondering about when you plan 16 to do a peer review. Because isn't that required for 17
-- I assume this would be considered a newly developed 18 method, and the staff is going to require peer reviews 19 as part of a PRA of a newly developed method. And is 20 that in your plan? Because I didn't recall seeing 21 that in your Topical Report.
22 MR. COLLIN: I'm not sure I understand 23 what you mean by "new."
24 MEMBER REMPE: Well, although BISON has 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
32 been around for a while, you're adding new models to 1
it. And so, for your code, I believe, if you're going 2
to be using something that supports a PRA, which I 3
believe you're going to use the licensee modernization 4
process with your design, right? And so, the staff 5
usually requires newly developed methods to have a 6
peer review. And where will that be in your code 7
development process, before or after you do the V&V?
8 MR. COLLIN: I might let some of my 9
licensing colleagues answer that question. We have 10 not -- well, at least as far as I know, I have not 11 gotten into that type of discussion with the rest of 12 the Kairos team yet. Now we're early in our V&V. So, 13 right now, we're mostly focused on doing that V&V.
14 But Darrell or Jim, maybe you have an answer.
15 MR. TOMKINS: Blaise, maybe Brandon can.
16 Brandon, can you address that?
17 MR. HAUGH: Sure, I can do that.
18 Hi. This is Brandon Haugh, the Director 19 of Modeling Simulation at Kairos Power. Hopefully, 20 you can hear me okay.
21 So, Joy, to answer your question, I'll do 22 it in two parts.
23 So, we will go through a commercial grade 24 dedication activity for BISON and KP-BISON when we get 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 to that point. So, that will be at the end or near 1
the end of our verification and validation process.
2 So, that will meet our quality assurance requirements 3
to make sure that the code performs as it's supposed 4
to.
5 When it comes to the peer review, I would 6
leave that to the PRA model, when we get to the 7
application of the licensing modernization project.
8 It wouldn't necessarily be BISON itself. It would be 9
an application within the PRA, whether that's Level 1, 10 2, or 3, and how it's used, determining frequency and 11 consequences.
12 So, we haven't committed to the 13 application of the licensing modernization project for 14 the Hermes Test Reactor. That's what we're focused on 15 now.
16 While this report, methodology, could be 17 applied to both, our nearer-term horizon is the non-18 power test reactor. So, we'll be applying it in a 19 more deterministic fashion.
20 MEMBER REMPE: So, if you're just going to 21 focus for the near term on Hermes, do you really need 22 NRC approval? I mean, that's going to be built on the 23 Oak Ridge site, right?
24 MR. HAUGH: No, it --
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34 MEMBER REMPE: So, it's not a powered 1
reactor. So, why worry about all these safety 2
evaluations?
3 MR. HAUGH: Well, the reactor is not on a 4
DOE site. It's outside of that. So, we are licensing 5
that with the NRC. While it is a non-power reactor, 6
we still need appropriate methods to ensure that we 7
meet the top-level regulatory requirements. And fuel 8
performance, since it's a fission product barrier, is 9
one of those.
10 MEMBER REMPE: Okay. Well, we'll just 11 have to see how this goes. Thank you.
12 MR. HAUGH: Uh-hum.
13 MR. COLLIN: All right. So, back to the 14 presentation. So, yes, this slide shows like a high-15 level -- it's a high-level flow chart of fuel 16 performance analysis and methodology. As mentioned 17 earlier, what we're trying to do, basically, is from 18 our irradiation input parameters, which are fission 19 rate
- density, fast fission
- fluence, and the 20 temperature of the coolant, these are inputs to the 21 code.
22 Our code performs thermal analyses, so 23 looking at the temperatures of all the coating layers 24 and of the kernel, performs a stress analysis 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
35 calculates the stress in the coating layers. And the 1
stresses inform about potential failure of the coating 2
layers.
And the temperatures inform the 3
diffusivities, so the values of the diffusion 4
coefficients in the various layers, and that leads to 5
calculation of the fission product really. So, we say 6
there's like more to each of these boxes, but for a 7
public presentation, that's the high-level methodology 8
for KP-BISON analysis.
9 So, I already mentioned the fact that, 10 during quantification, all of the fuel properties will 11 be distributed around a nominal value and extend on 12 both sides of these nominal values, for the average 13 values during quantification.
14 So, basically, each property will have 15 statistical variations because of this process. And 16 we know from experience that particles that are in the 17 tails of these distributions are usually more likely 18 to fail. That is, for instance, when the thickness of 19 your silicon carbon layer gets too thin, it might not 20 be able to sustain the internal pressure from the 21 fission gas, if it's too thin. So, it's more likely 22 to fail.
23 So, we have to account for these 24 statistical variations when assessing the probability 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 of failure of the fuel. So, this table here shows 1
just a summary of all of the fuel properties that will 2
have a distribution around these new values. And as 3
mentioned in these bullets, part of the methodology is 4
to treat the fuel statistically, so it captures (audio 5
interference) the rise of failure probability.
6 And this is done in KP-BISON by using 7
Monte Carlo modeling, where we, basically, sample 8
through these distributions for -- each particle is 9
sampled through the distribution of its fuel 10 properties. So we can, for each particle, more 11 accurately determine if it fails or if it stays intact 12 during irradiation.
13 That's sort of, again, a high-level 14 summary of that Monte Carlo calculation scheme where 15 we sample the fuel properties. We let KP-BISON do its 16
-- like with the sampled particles, look at the 17 potential, you know, the particular performance of 18 that particle under KP-FHR irradiation conditions.
19 Basically, does it fail or does it stay intact?
20 We sample many, many particles to get 21 something representative of the KP-FHR core and, also, 22 representative of the distributions of these fuel 23 properties. And when the loop is over, we just 24 compute the statistics of all these sampled 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
37 calculations and come up with the overall failure 1
probability for that sample and, again, the potential 2
or subsequent fission product release.
3 So, we have, obviously, discussed this 4
scheme in greater details with the Subcommittee in 5
July. Again, this is a high-level flow chart for this 6
public meeting.
7 As I mentioned, part of V&V is uncertainty 8
quantification. In general, when talking about fuel 9
performance modeling, and, in particular, for UCO, 10 uncertainty can be found in these four inputs to the 11 code:
12 Your operating conditions. So, that would 13 be in our case the fission rate density, the neutron 14 flux, the temperature of coolant. All of these can 15 have uncertainties that for KP-BISON would come 16 from -- these are inputs that come from neutronation 17 and thermal-hydraulic codes. So, these codes have 18 their own uncertainties, and we, obviously, have to 19 account for the fact that all these inputs to KP-BISON 20 come with their own uncertainties.
21 Uncertainties can also be found on the 22 material properties. So, I think kernel swelling, 23 shrinkage of the carbon layers. So, all these 24 material properties are known within a degree of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
38 uncertainty. And since they impact the potential or 1
the interior of the coating layer, we also have to 2
account for their potential uncertainty when running 3
KP-BISON.
4 Some of the physical models that we use 5
are also subject to uncertainty. They would, for 6
instance, include diffusivities that are used to model 7
fission product transport. So, again, we have to 8
understand what the impact of the uncertainties on 9
these physical models, what impact they have on the 10 results calculated by KP-BISON.
11 And finally, as already mentioned, we do 12 have uncertainties on the fuel properties that come 13 from these statistical variations during the 14 quantification process.
15 So, that's a lot of different parameters.
16 I think at some point we tallied up to about 60 17 different input parameters to KP-BISON. We already 18 know from previous codes or evolution of programs that 19 some of these input parameters have a large impact on 20 fuel performance. And since some of them have a 21 negligible impact, it's our goal to run some 22 sensitivity studies to particularly assess the 23 relative impact of all these input parameters to the 24 code.
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 And again, we find these two FOMs 1
throughout the presentation. We are concerned about 2
the probability of failure of the fuel and the 3
potential release of fission products that would be 4
enhanced by failure of some of the coating layers.
5 So, we give a methodology for uncertainty 6
quantification. This methodology is proprietary. So, 7
we will not discuss it in detail during the open 8
session of this meeting. It's already been discussed 9
in early July with the Subcommittee.
10 We feel that methodology provides us with 11 a conservative way of calculating of failure of the 12 fuel and release of fission products. So, the 13 methodology includes the calculation of one-sided 14 95/95 tolerance limits on these two figures of merit.
15 And we think that these tolerance limits, the way they 16 are calculated and the way the methodology for 17 uncertainty quantification has been developed, we feel 18 that these are conservative tolerance limits that 19 will, then, show that we do have like a conservative 20 way of calculating the performance of the fuel in our 21 KP-FHR cores.
22 And I think that's the end of it.
23 MEMBER PETTI: Members, any questions?
24 MEMBER HALNON: This is Greg Halnon.
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 A quick question on the uncertainty 1
calculations. Since the plant is not really 2
physically built or designed
- yet, from my 3
understanding, how did you ensure that the operating 4
conditions that you chose were bounding in the fact 5
that, since there's an input to the model for 6
uncertainties -- I guess what I'm trying to get to is, 7
how did you define the operating conditions, such that 8
you bounded all the necessary fuel parameters that may 9
result from operating transients and other things that 10 may happen, based on human interactions?
11 MR. COLLIN: So, I will, unfortunately, to 12 answer this question during this public session. The 13 treatment of operating conditions is a large, like 14 important part of our methodology.
15 MEMBER HALNON: Okay. Well, we can 16 talk --
17 MR. COLLIN: Yes, we can discuss; I can 18 answer that question once we hit the closed session, 19 if you --
20 MEMBER HALNON: Sure. Yes.
21 MR. TOMKINS: And I might add, I mean, 22 Greg, we haven't made a final determination of the 23 operating condition uncertainties because it does 24 depend on the instruments we use in the plant 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
41 things like that. So, that isn't done yet.
1 MEMBER HALNON: Okay. Well, that may be 2
the answer to the question.
3 MR. TOMKINS: Yes, yes.
4 MEMBER HALNON: We can talk in more detail 5
later on.
6 MR. COLLIN: Yes, we do have -- they're 7
still TBD. Again, they do not depend on -- they're, 8
you know, outside of -- well, I guess what I'm trying 9
to say is like these are things that are not 10 controlled by KP-BISON. These are inputs to the code.
11 The code will take whatever is given to it. But, 12 right now, we have the way around to, again, make sure 13 that we run conservative evaluation of this 14 uncertainty. But, yes, we can discuss it in more 15 detail.
16 MEMBER HALNON: Okay. Yes, let's discuss 17 the relationship between the inputs and how you chose 18 the operating conditions to provide those inputs. I 19 think that's my question. So, we'll talk more.
20 MR. COLLIN: Sure.
21 MEMBER PETTI: Okay. If there's no more 22 questions, does staff have their presentation?
23 MR. SCHMIDT: Yes, I do.
24 MEMBER PETTI: Thanks, Jeff.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
42 MR. SCHMIDT: I'll log in here.
1 Can people see this?
2 MEMBER PETTI: Yes.
3 MR. SCHMIDT: All right. Great.
4 Good morning, everyone. My name is Jeff 5
Schmidt, and I'm a Senior Reactor Systems Engineer in 6
the Advanced Reactor Technical Branch II, the Division 7
of Advanced Reactors and Non-Power Production and 8
Utilization Facilities, or better known as DANU.
9 We're going to be discussing the KP-FHR Fuel 10 Performance Methodology Revision 3.
11 Kairos requested approval of the Fuel 12 Performance Methodology Revision 3. The Topical 13 Report is applicable to the Kairos UCO TRISO fuel for 14 the FHR non-power reactor, which has been identified 15 as Hermes earlier, and the power reactor. So, this is 16 kind of a dual-use Topical Report. I think that's 17 already been addressed.
18 The TR itself identifies several open 19 items to be addressed in subsequent revisions. We've 20 talked about that already. That is a staged review.
21 So, there are some known. Kairos identified open 22 items, and some staff identified open items in the 23 limitation section of the SE.
24 The staff review focused on 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
43 calculational framework, which is composed of UCO 1
TRISO fuel failure mechanisms, which Blaise went into 2
in some detail; uncertainty parameters and associated 3
methodology; determination of the upper tolerance 4
limits for the figures of merits of in-service failed 5
fuel fractions and fission product release. TRISO 6
being one of the important barriers to fission product 7
release, these outputs from the fuel performance 8
analysis fell into the mechanistic source term 9
methodology, which is a separate Topical Report.
10 The regulatory
- basis, Kairos wants 11 flexibility so far in the licensing path. So, you'll 12 see that 10 CFR 50.34(a) and (b) are also listed, and 13 the corresponding regulations for design 14 certification, combined license application, and 15 standard design approvals.
16 As mentioned, the TRISO particle is the 17 primary fission product barrier. So, 10 CFR 100.11, 18 "Determination of exclusion area, low population zone 19 and population center distance," is an important 20 regulatory basis.
21 And then, Kairos has a PDC 10, "Reactor 22 Design," which has been approved by staff, which, 23 basically, limits the release of TRISO, well, of 24 fission products during normal operations and AOOs.
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44 Portions of the Topical Report not 1
addressed by the Safety Evaluation, and there's a 2
number here. So, the PIRT in Section 2.3; Section 3
2.4, "Fission Product Transport," and all the 4
subsections of 2.4; Section 3, "Fuel Modeling, 5
Material Properties, and Physical Models"; Section 6
4.1.1, "Verification and Validation"; Section 5, 7
"KP-BISON Code, and all subsections; Topical Report 8
(audio interference), "Defeating Coefficients for Key 9
Fission Product Modeling KP-BISON"; Section 6.4.2, 10 "TRISO and Pebble Models, including potential pebble 11 behavior and material uncertainties that could affect 12 TRISO particle failure fractions," and Section 6.3, 13 "Fission Product Release," as it pertains to fuel-14 pebble mechanical and chemical interactions with a 15 salt environment and possible wear, which (audio 16 interference) could be outside the scope of this 17 Topical Report.
18 And I know there was a question on the 19 salt environment, and those type of questions are 20 being addressed by the Kairos Fuel Qualification 21 Topical Report.
22 So, the staff made no findings in these 23
- areas, primarily because of verification and 24 validation and quantitative uncertainty analysis was 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
45 not provided in Revision 3.
1 As was mentioned --
2 MEMBER MARCH-LEUBA: Jeff?
3 MR. SCHMIDT: Yes?
4 MEMBER MARCH-LEUBA: Yes, this is Jose.
5 MR. SCHMIDT: Okay.
6 MEMBER MARCH-LEUBA: This petition from 7
the staff, they are going to provide that in Revision 8
4 in the near future? Or is it going to be a 9
supplement? Or both?
10 MR. SCHMIDT: Yes, I don't know. Maybe 11 Kairos can speak to that. I mean, my conceptual idea 12 was a Revision 4, but --
13 MEMBER MARCH-LEUBA: Yes, that's what I 14 was thinking because, if we issue Revision 3 as an 15 approved Topical Report, and it doesn't get superseded 16 by a Revision 4, then there are holes in this 17 approach.
18 MR. SCHMIDT: Yes. Yes. So, I guess I 19 envisioned it as a Revision 4 which would supersede 20 this revision in its entirety.
21 MEMBER MARCH-LEUBA: Correct.
22 MEMBER REMPE: So, Jeff, this is Joy.
23 MR. SCHMIDT: Hi, Joy.
24 MEMBER REMPE: I guess I'm not sure from 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 what I've heard from Kairos. So, it would be good to 1
hear from them because it sounded like they're going 2
to have a multi-stage review process, and you might 3
end up with six or seven of these iterations. And to 4
preclude -- I mean, I hope that it will all come in 5
Rev. 4 -- but to preclude having a lot of these 6
iterations for all these design developers, I'm 7
wondering if the staff needs to start thinking about 8
some guidance.
9 And I know I mentioned this during the 10 Subcommittee meeting on, what's the minimum set of 11 requirements for a first-step review? And will you 12 limit it to two or three, or can they come in 10 13 times, and then, say, "Well, we have 10 SEs from the 14 staff," or something? I just am kind of wondering how 15 many iterations there are going to be.
16 MR. SCHMIDT: Do you want me to try to 17 handle that or do you want Kairos --
18 MR. TOMKINS: Can I address that? This is 19 Jim Tomkins. Can you hear me?
20 MEMBER REMPE: Sure. I'm interested in 21 Kairos' response, but I'm also interested in the 22 bigger picture for all of the design developers that 23 are coming through here.
24 MR. TOMKINS: So, first off, it is a two-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 step process. So, it's not going to be an eight-step 1
process. And so, we're going to close these open 2
items, either with a revision to the Topical Report or 3
a separate Technical Report or possibly as part of the 4
FSAR. We're not committing to any one of those 5
approaches at this point in time.
6 But we're going to get an SER that says, 7
"Here's the open items." And we think any one of 8
those three methods is a viable way to close the open 9
items.
10 MEMBER REMPE: So, this is on the record, 11 and, I mean, you've got a couple of these or several 12 of these Topical Reports, and they're all kind of a 13 multi-stage review process. And I guess maybe I've 14 missed something, but this is the first time where 15 I've heard you say on the record, "No, we're just 16 going to have a two-step process," which gives me a 17 lot or relief, frankly. So, we can, actually, put 18 this in our letter, that this is the first step of a 19 two-step process, is what the licensee told us on the 20 record?
21 MR. TOMKINS: Yes. We might want to have 22 Darrell --
23 MR. GARDNER: This is --
24 MR. TOMKINS: Yes.
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 MR. GARDNER: Yes, this is Darrell 1
Gardner.
2 I would argue that that's not what we 3
said. What we said was that we recognize that, when 4
this SE is issued, it will have open items that we're 5
obligated to address as part of a future licensing 6
action, which would an FSAR or a PSAR, as the case may 7
be, or a Design Certification or a COL. So, all those 8
avenues are available in terms of licensing actions.
9 And those licensing actions could not be completed, 10 absent us addressing these open items. That's --
11 MEMBER REMPE: Well, I guess I'm confused.
12 You're saying you may not even submit another Topical 13 Report? You may just wait until the PSAR?
14 MR. GARDNER: I'm saying that is an 15 acceptable licensing option. There's no regulations 16 that require any Topical Reports be submitted at all.
17 MEMBER REMPE: Okay. So, there will be a 18 lot more required in the FSAR and PSAR if that's your 19 approach. And so, I guess we --
20 MR. GARDNER: (Audio interference). I get 21 it.
22 MEMBER REMPE: -- maybe should think about 23 documenting this in our letter; that, clearly, 24 something else has to be done, but it's unclear 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
49 whether it will come as a Topical Report or as the 1
final FSAR.
2 MR. GARDNER: I guess the question would 3
be of the Committee is, is there a reason that 4
decision has to be made as part of this review?
5 MEMBER REMPE: No, but, again, I'm 6
concerned, not just with Kairos and what you're 7
planning on doing. You're right on that. But I am 8
wondering what is going to happen here with all of the 9
design developers and whether the staff needs to think 10 about some guidance for this process. Because there 11 have been --
12 MR. GARDNER: Sure, I understand --
13 MEMBER REMPE: -- some doubts in all of 14 your Topical Reports.
15 MR. GARDNER: I understand that, and I'd 16 like to just take the opportunity to go on the record.
17 We've had an extensive dialog with both the staff, the 18 management team, and the Commission, about our 19 licensing approach and our licensing strategies. I 20 would say we've had feedback that was very positive in 21 our approach that's consistent with a way to innovate.
22 MEMBER REMPE: But you can understand 23 that, again, our concern is safety, but sometimes we 24 have design developers who come in who complain about 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 the cost for licensing. And if it was an endless DO 1
loop, it could really increase the cost. But, again, 2
if you're just going to wait until the FSAR, that's 3
another situation. I just am trying to understand the 4
vision here.
5 MEMBER MARCH-LEUBA: Yes, and this is 6
Jose.
7 And I understand your position from a very 8
high level, point of view, but I cannot see how you 9
can validate a KP-BISON code in the FSAR. There is no 10 section of the FSAR that says, "Validation of Codes."
11 You have to validate it before you use them. That's 12 my opinion.
13 MR. GARDNER: So, this is Darrell Gardner 14 again to say that, there are a number of open items.
15 I mentioned three pathways that are acceptable 16 licensing vehicles to address those open items. You 17 could use a combination. So, typically, validation is 18 not something you would see, but you could see that in 19 a Technical Report, while other open items might be 20 addressed directly in the FSAR.
21 MEMBER HALNON: Yes, and that's to mean 22 that all the information in a study or uncertainty 23 analysis would be in the text of an FSAR, but you 24 would reference a report or some other thing that 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
51 staff had reviewed during the process. I'm assuming 1
that's what you're meaning here. Because, from Jose's 2
perspective, we wouldn't put chapters and pages and 3
pages and pages of a study in there. It would be a 4
lot of reference --
5 MR. TOMKINS: Right, because it would be 6
proprietary.
7 MEMBER HALNON:
Incorporation by 8
reference. Right.
9 MR. TOMKINS: Yes.
10 MEMBER HALNON: But the staff would review 11 those referenced reports as part of the approval 12 process for the application.
13 MR. TOMKINS: Right.
14 MR. SCHMIDT: This is Jeff Schmidt.
15 Should I move on then?
16 MEMBER PETTI: Yes, please do.
17 MR. SCHMIDT: Thank you.
18 So, the staff review, the staff found that 19 the UCO TRISO particle failure mechanism is 20 acceptable, based on the expected operating 21 conditions, subject to Limitation and Condition 3, 22 based on the AGR program data and the EPRI TRISO 23 Topical Report.
24 Other relevant TRISO particle release 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 mechanisms, such as manufactured defect particles and 1
dispersed uranium, are included in the calculational 2
framework.
3 Relevant model uncertainties, such as 4
particle manufacturing variability,
- model, and 5
physical properties, and irradiation conditions, 6
operating conditions, were adequately accounted for.
7 Individual uncertainties were 8
conservatively combined to yield an upper tolerance 9
limit for the predicted failed particle fraction and 10 the fission product release from fully intact and in-11 service failed particles.
12 The staff SER limitations and conditions.
13 NRC-approved fuel performance failure must be used to 14 determine in-service particle failure fraction and 15 fission product release. A subsequent TR, as has been 16 talked about, may include other means to determine 17 these figures of merit.
18 UCO TRISO --
19 MEMBER MARCH-LEUBA: Can you give me an 20 example of these "other means"? What do you have in 21 mind?
22 MR. SCHMIDT: Let's see. A subsequent 23 document may include other means. I guess what we're 24 really saying there is the revisions of the Topical 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 Report will -- so, there are options in the Topical 1
Report which you could input, instead of using an 2
approved fuel performance code, for example, you could 3
use directly, say, the AGR fuel failure fractions as 4
input. You could use experimentally-derived or 5
experimentally-based inputs into the code.
6 That was one of the options listed in the 7
Topical Report, but the details weren't provided 8
sufficient for the staff to make any finding in that 9
area.
10 MEMBER MARCH-LEUBA: Okay. Thanks. Yes, 11 keep going.
12 MR. SCHMIDT: Yes. So, Jose, that was, 13 let's say if you wanted to use the AGR fuel failure 14 fractions, for example, as input, experimentally-15 based. Does that make sense?
16 MEMBER MARCH-LEUBA: Yes, basically, what 17 you are saying is that TRISO is a very good fuel and 18 you can probably bound what can possibly be a worse 19 mechanism; you don't need to calculate it?
20 MR. SCHMIDT: Yes, or you can use 21 experimental data.
22 MEMBER MARCH-LEUBA: Yes, but that's what 23 I mean by "bounding." And it's probably a good 24 approach. I'm not saying it's not.
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 MR. SCHMIDT: Yes.
1 MEMBER MARCH-LEUBA: I understand, but I 2
would code, though.
3 MR. SCHMIDT: Yes, so, I mean, the staff 4
is not agreeing or disagreeing. It's just saying that 5
that was presented in the Topical Report, but we would 6
need some information about it, how that was proposed 7
to be done.
8 So, the UCO TRISO particle failure 9
mechanism must be reevaluated if the operating 10 conditions are not bounded by the UCO TRISO EPRI-AR-1A 11 Topical Report.
12 The Kairos Fuel Qualification Topical 13 Report will address expanding the EPRI TRISO operating 14 envelope. Kairos has identified in the Fuel 15 Qualification Topical Report that the particle power 16 density is not bounded, at least for the KP reactor.
17 It may be bounded the Hermes reactor that's still 18 under review, but I think they acknowledge that there 19 might be some additional work needed there for 20 particle power.
21 Federal Limitations and Conditions 4, 5, 22 6, 8, 10, and 11 exist, due to information not 23 included in the TR Revision 3, but is expected in 24 subsequent revisions.
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 The methodology can be used to evaluate 1
the figures of merit -- or cannot be used, I'm sorry 2
-- cannot be used to evaluate the figures of merit for 3
AOOs, design basis accidents, beyond design basis 4
events, as a methodology for combining these with 5
bounding quasi-steady-state operating conditions was 6
not provided.
7 Some aspects of pebble performance will be 8
addressed in another TR. And that's really referring 9
to the Kairos Fuel Qualification Topical Report.
10 Staff conclusions. The fuel performance 11 methodology of Revision 3 Topical Report provides an 12 acceptable methodology for determining conservative 13 UCO TRISO particle fission product release from in-14 service failed and intact particles, manufacturing 15 defects, and dispersed uranium.
16 Staff approvals are subject to the 17 Limitations and Conditions of the SER.
18 That ends my presentation. Are there any 19 questions?
20 (No response.)
21 MEMBER PETTI: Thank you, Jeff.
22 Hearing no further questions.
23 So, I think were' done with this session, 24 Mr. Chairman.
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 CHAIR SUNSERI: All right. Thank you, 1
Dave.
2 We can ask for public comments at this 3
point in time.
4 And because we are using this Teams 5
approach, it's my understanding that the public can 6
unmute their line by using *6, state their name, and 7
make their comment.
8 So, let's call for that then. So, members 9
of the public listening in, this is your opportunity 10 for making a comment.
11 If you are muted, unmute your line using 12
- 6, state your name, and make your comment.
13 (No response.)
14 All right. We are not hearing any. So, 15 I mean, we will offer the same opportunity for direct 16 participants of the Teams line, just like we would be 17 doing if you were in the room.
18 So, any members that would like to make a 19 comment, please do so at this time.
20 (No response.)
21 All right. Dave, it looks like we don't 22 have any comments.
23 So, at this point in time, we think we 24 would move into report preparation, which we needed 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
57 at least start in a closed session, it's my 1
understanding. Is that correct?
2 MEMBER PETTI: Correct.
3 CHAIR SUNSERI: All right. So, let's do 4
this. Let's take a 30-minute break. We'll reconvene 5
at 10:30 Eastern time in closed session.
6 (Whereupon, at 9:59 a.m., the open session 7
was concluded.)
8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
KP-NRC-2109-001 Kairos Power LLC www.kairospower.com 707 W Tower Ave, Suite A 5201 Hawking Dr SE, Unit A 2115 Rexford Rd, Suite 325 Alameda, CA 94501 Albuquerque, NM 87106 Charlotte, NC 28211 Project No. 99902069 September 2, 2021 US Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Kairos Power LLC Presentation Materials for Kairos Power Meeting with the Advisory Committee on Reactor Safeguards on Fuel Performance Methodology Topical Report This letter transmits presentation materials for the September 8, 2021 meeting with the Advisory Committee for Reactor Safeguards (ACRS) full committee. At the meeting, participants will discuss the KP-FHR Fuel Performance Methodology Topical Report (KP-TR-010) that was submitted to the Nuclear Regulatory Commission staff for review and approval. provides the non-proprietary presentation materials. Kairos Power authorizes the Nuclear Regulatory Commission to reproduce and distribute the submitted non-proprietary content, as necessary, to support the conduct of their regulatory responsibilities.
If you have any questions or need any additional information, please contact James Tomkins at tomkins@kairospower.com or (510) 808-5265, or Darrell Gardner at gardner@kairospower.com or (704)-769-1226.
Sincerely, Peter Hastings, PE Vice President, Regulatory Affairs and Quality
Enclosures:
1)
Presentation Materials for the September 8, 2021 ACRS Meeting (Non-Proprietary)
KP-NRC-2109-001 Page 2 xc (w/enclosure):
William Kennedy, Acting Chief, Advanced Reactor Licensing Branch Stewart Magruder, Project Manager, Advanced Reactor and Licensing Branch
KP-NRC-2109-001 Presentation Materials for the September 8, 2021 ACRS Meeting (Non-Proprietary)
KAIROS POWER ACRS FULL COMMITTEE MEETING SEPTEMBER 8, 2021 KP-FHR Fuel Performance Methodology Topical Report Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
- Introduction
- Fuel Behavior (including PIRT analysis)
- Fuel Modeling
- Verification and Validation / Uncertainty Quantification
- KP-BISON Code
- Fuel Performance Analysis Methodology 2
Topical Report Contents 2
Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
UCO TRISO Fuel Behavior Coating Layer Irradiation Behavior Observation Kernel Swells outward Pushes buffer outward Buffer Shrinks inward Pulls IPyC inward if not debonded IPyC / OPyC Shrink early during irradiation and then start swelling later in irradiation as fast neutron fluence accumulates Dimensional changes are anisotropic Swelling starts radially at moderate fast neutron fluence levels and tangentially at higher fast neutron fluence levels SiC Elastic behavior PyC shrinkage provides compressive stress Fission gas pressure causes tensile stress 3
Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
Key failure mechanisms identified in TRISO fuel Pressure vessel failure of spherical or aspherical particles resulting in the failure of all three coating layers Cracking of the IPyC layer leading to SiC failure Partial debonding of the IPyC from the SiC leading to SiC failure Kernel migration towards the SiC layer and its subsequent failure Chemical attack of the SiC layer by fission products or CO leading to its failure Thermal decomposition of the SiC layer at high temperatures Buffer fracture leading to cracking of undebonded IPyC KP-BISON models failure mechanisms relevant to UCO fuel under KP-FHR irradiation conditions with the purpose of predicting the potential failure of the SiC layer and the release of fission products.
UCO TRISO Fuel Behavior - Failure Mechanisms 4
Copyright © 021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
UCO TRISO Fuel Performance Modeling - KP-BISON Fluoride Salt-Cooled High Temperature Reactor (KP-FHR)
UCO TRISO Fuel Engineering-scale nuclear fuel performance code Finite-element modeling of LWR, TRISO, and metal fuels in 1D-spherical, 2D-axisymmetric, and 3D geometries Fully-coupled thermodynamics and species diffusion equations Steady and transient reactor operations UCO TRISO Model in BISON 5
Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
UCO TRISO Fuel Performance Modeling - KP-BISON KP-BISON was chosen as Fuel Performance Code by Computational benefits from the framework Leverage of extensive development effort by. and Level of development and maturity of code o
Co-development KP-INL o
FOA award DE-NE0008854 Modeling and Simulation Development Pathways to Accelerating KP-FHR Licensing Efficient support from development and maintenance team (BISON Team) at INL 6
Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
KP-BISON - Inputs & Outputs Geometry radius, thickness, etc.
Fuel characteristics composition, densities, etc.
Variation in as-fabricated properties Material properties implemented in KP-BISON Irradiation conditions Fission rate density Fast fluence Coolant temperature Fuel temperature, fission gas pressure, displacements, stress
Figures of Merit (FOMs)
Failure probability Fission product release 7
Copyright © 021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
KP-BISON - Fuel Properties Leverage of extensive DOE effort in the development and qualification of UCO TRISO fuel (AGR Program)
KP-FHR UCO TRISO fuel is similar to AGR UCO TRISO fuels AGR-2 -> UCO TRISO-Coated Particle Fuel Performance -
Topical Report EPRI-AR-1(NP)-A AGR-5/6/7 -> AGR Programs UCO TRISO fuel qualification and margin tests AGR-5/6/7 Test Train - Courtesy of AGR Program 8
Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
KP-BISON - Material Properties & Physical Models TRISO Constituents Material Properties Kernel Buffer IPyC SiC OPyC Swelling Elastic modulus Poissons ratio Irradiation-induced creep Poissons ratio in creep Irradiation-induced dimensional changes Thermal conductivity Specific heat capacity Thermal expansion Diffusion coefficients Physical Models Description Heat Equation Thermal state of the particle and temperature profile across the kernel and coating layers Fission yields Generation of fission products Fission gas release Generation of internal pressure Internal gas pressure Stress state of the particle potentially leading to its failure Palladium penetration Corrosion of the SiC layer potentially leading to its failure Release rate over birth rate (R/B) ratio Indicator of TRISO failure Fission product transport (Fickian diffusion)
Release of fission products to the coolant Existing database of material properties and physical models suited to modeling of TRISO fuel behavior and performance 9
Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
Verification & Validation IAEA CRP-6 Benchmark Gen-IV Benchmark Fuel Performance Models During Normal Operation And Operational Transients o
Verification: cases 1-13 Fission Product Release Behavior Models Under Accident Conditions o
Verification: cases 1-5 o
Validation: cases 6-11 INL Benchmark International Data TRISO Fuel Performance Models Under Accident Conditions o
Select AGR-1, AGR-2, and HFR-EU1bis safety tests o
Includes code-to-code comparison during normal operation Code-to-code comparison with PARFUME o
Representative cases of KP-FHR AGR-1 and AGR-2 PIE and AGR-5/6/7 R/B data o
Select data within KP-FHR envelope o
Separate effects Additional PIE or R/B data o
German, Chinese, etc.
10 Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
Fuel Performance Analysis Methodology Failure Probability Fission Product Release Thermal Analysis Stress Analysis Fission Rate Density Fast Neutron Fluence Flibe Temperature For each TRISO particle Irradiation input parameters Thermo-mechanical analysis of the TRISO coating layers Evaluation of the failure probability (stress) and fission product release (diffusivities)
Diffusivities 11 Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
Statistical Treatment Property Specified Mean Value Kernel diameter (m) 425 10 Buffer thickness (m) 100 15 PyC thickness (m) 40 4 SiC thickness (m) 35 3 Kernel density (g/cm3) 10.4 Buffer density (g/cm3) 1.05 0.10 PyC density (g/cm3) 1.90 0.05 SiC density (g/cm3) 3.19 C/U atomic ratio 0.40 0.10 O/U atomic ratio 1.50 0.20 PyC BAF 1.045 SiC aspect ratio 1.04 Particle-to-particle statistical variations in physical dimensions and fuel properties (layer thickness, density, etc.) that arise from the fuel fabrication process.
Particles in the tails of the statistical distributions are more prone to failure.
statistical treatment of a large population of particles to compute its overall failure probability.
Monte Carlo computation scheme implemented in KP-BISON 12 Copyright © 021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
Monte Carlo Calculation Scheme Sampling Fuel Properties Failure Probability Fission Product Release Sampling loop Computation of statistics for all sampled particles Fuel Performance Analysis of sampled particle 13 Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
Uncertainty Quantification Uncertainty exists in:
Operating conditions (i.e., fission rate density, neutron flux, temperature)
Material properties that define the mechanical state of the TRISO particles and, ultimately, the integrity of the coating layers Physical models that determine some of the physical quantities affecting material properties and fission product transport Fuel properties (geometrical dimension, density, etc.) that are tailored by fuel fabrication to obtain TRISO particles that adequately perform under irradiation sensitivity studies will be conducted to assess the quantitative impact of the variations of these input parameters to the probability of failure of the TRISO particles and subsequent release of fission products.
14 Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
A proprietary methodology was developed to ensure that the probability of failure of the TRISO particles and subsequent release of fission products are calculated conservatively.
In particular, the methodology derives one-sided 95/95 tolerance limits on the two FOMs.
Uncertainty Quantification Methodology 15 Copyright © 2021 Kairos Power LLC. All Rights Reserved.
No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.
NRC Staff Evaluation of the KP-FHR Fuel Performance Methodology, Revision 3 Jeff Schmidt Senior Reactor Systems Engineer Advanced Reactor Technical Branch 2 Division of Advanced Reactors and Non-Power Production and Utilization Facilities Office of Nuclear Reactor Regulation
Introduction Kairos requested approval of the KP-FHR Fuel Performance Methodology Topical Report (TR) Revision 3 The topical report is applicable to a Kairos UCO TRISO fueled, FHR non-power or power reactor The TR identifies several open items to be addressed in a subsequent revision In addition to the Kairos identified open items, the staff identified additional items in the safety evaluation which need to be addressed in a subsequent revision(s)
The staffs review focused on the calculational framework composed of, UCO TRISO fuel failure mechanisms Uncertainty parameters and associated methodology Determination of the upper tolerance limits for the figures of merit (FOMs) of in-service failed fuel fraction and fission product release Outputs from fuel performance analysis are inputs to the mechanistic source term methodology 2
September 8, 2021 Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report
Regulatory Basis 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 10 CFR 100.11 Determination of exclusion area, low population zone and population center distance Kairos PDC 10 - Reactor design which has been approved by the staff (KP-TR-003-NP-A)
Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report 3
September 8, 2021
Portions of the Topical Report Not Addressed by the Safety Evaluation The staff makes no finding on the following TR sections:
Section 2.3, Phenomena Identification and Ranking Tables Section 2.4, Fission Product Transport and all the Section 2.4 subsections Section 3, Fuel Modeling - Material Properties and Physical Models, and all Section 3 subsections Sections 4.1.1; Verification; 4.1.2, Validation (and all 4.1.2 subsections); and 4.1.5, Validation, Verification and Uncertainty Quantification Results Section 5, KP-BISON Code, and all Section 5 subsections Topical report Table 3-8, Diffusion coefficients for Key Fission Products Modeled in KP-BISON Section 6.4.2, TRISO and pebble models, including the potential pebble behavior and material uncertainties that could affect TRISO particle failure fractions Section 6.3, Fission Product Release as it pertains to fuel pebble mechanical and chemical interactions with the salt environment, and possible wear which are stated by the vendor to be outside the scope of this tropical The staff made no findings in these areas primarily because no verification, validation and quantitative uncertainty analysis was provided in Revision 3 4
September 8, 2021 Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report
Staff Review The staff found the UCO TRISO particle failure mechanisms acceptable based on the expected operating conditions subject to Limitation and Condition 3 based on the AGR program data and the EPRI-AR-1-A topical report Other relevant TRISO particle release mechanisms such as manufactured defective particles and dispersed uranium are included in the calculational framework Relevant model uncertainties such as particle manufacturing variability, model and physical properties and irradiation conditions (operating conditions) were adequately accounted for The individual uncertainties were conservatively combined to yield an upper tolerance limit for the predicted failed particle fraction and the fission product release from fully intact and in-service failed particles September 8, 2021 5
Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report
An NRC approved fuel performance code must be used to determine in-service particle failure faction and fission product release. A subsequent TR revision(s) may include other means to determine these FOMs.
UCO TRISO particle failure mechanisms must be re-evaluated if operating conditions are not bounded by the UCO TRISO EPRI-AR-1-A TR. The Kairos Fuel Qualification TR will address expanding the EPRI TRISO operating envelope.
Several Limitations and Conditions (4, 5, 6, 8, 10 and 11) exist due to information not included in TR Revision 3 but is expected in a subsequent revision(s).
The methodology can not be used to evaluate the FOMs for AOOs, DBA and BDBE events as the methodology for combining these with the bounding quasi steady-state operating conditions was not provided.
Some aspects of pebble performance will be addressed in another TR Staff SER Limitation and Conditions 6
September 8, 2021 Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report
- The Fuel Performance Methodology, Revision 3, TR provides an acceptable methodology for determining a conservative UCO TRISO particle fission product release from in-service failed and intact particles, manufacturing defects, and dispersed uranium
- The Staff approvals are subject to the Limitations and Conditions of the SER.
Staff Conclusions 7
September 8, 2021 Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report
Topical Report (TR)
Uranium Oxycarbide (UCO)
Tristructural isotopic (TRISO)
Figures of Merit (FOMs)
Kairos Power Fluoride-Salt Cooled High Temperature Reactor (KP-FHR)
Acronyms/Definitions 8
September 8, 2021 Non-Proprietary ACRS Presentation on the Kairos Power, LLC Reactor Coolant Topical Report