ML24275A019
| ML24275A019 | |
| Person / Time | |
|---|---|
| Issue date: | 08/21/2024 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-0017 | |
| Download: ML24275A019 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards X-Energy Xe-100 Design-Centered Subcommittee Open Session Docket Number:
N/A Location:
teleconference Date:
08-21-24 Work Order No.:
NRC-0017 Pages 1-134 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.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com 1
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 X-ENERGY XE-100 DESIGN-CENTERED SUBCOMMITTEE 7
+ + + + +
8 WEDNESDAY 9
AUGUST 21, 2024 10
+ + + + +
11 The Subcommittee met via Teleconference, 12 at 8:30 a.m. EDT, Robert P. Martin, Chair, presiding.
13 14 COMMITTEE MEMBERS:
15 ROBERT P. MARTIN, Chair 16 RONALD G. BALLINGER, Member 17 VICKI M. BIER, Member 18 VESNA B. DIMITRIJEVIC, Member 19 CRAIG A. HARRINGTON, Member 20 GREGORY H. HALNON, Member 21 WALTER L. KIRCHNER, Member 22 SCOTT P. PALMTAG, Member 23 THOMAS E. ROBERTS, Member 24 MATTHEW W. SUNSERI, Member 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
2 ACRS CONSULTANTS:
1 DENNIS BLEY 2
4 5
DESIGNATED FEDERAL OFFICIAL:
6 DEREK WIDMAYER 7
8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
3 CONTENTS 1
Opening Remarks 4
2 Staff Introduction............... 10 3
Xe-100 Principal Design Criteria Topical 4
Report..................... 11 5
6 7
8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
4 P R O C E E D I N G S 1
(8:30 a.m.)
2 CHAIR MARTIN: This is a meeting of the 3
Advisory Committee on Reactor Safeguards X-Energy's 4
Xe-100 Design-Centered Subcommittee. I am Robert 5
Martin, Chair of today's subcommittee meeting. ACRS 6
members in attendance include myself, Ron Ballinger, 7
Craig Harrington, Tom Roberts, and Vicki Bier. All 8
right, and members attending virtually via Teams, and 9
I will definitely navigate the screen here, I see Greg 10 Halnon, Matt Sunseri --
11 (Audio interference.)
12 CHAIR MARTIN: Is there a live mic?
13 Please mute. If you have a live mic, please mute.
14 And I see Scott Palmtag, and Walt Kirchner, and Vesna 15 Dimitrijevic.
16 All right, and we have one consultant 17 participating in person. To my right, we have Steve 18 Schultz, and we have a couple of consultants, at least 19 one, I saw Dennis Bley online, and I'm not seeing 20 anyone else, but if I indeed missed somebody, either 21 members or consultants, please speak up now. I'll 22 give you a few seconds. Okay, thanks.
23 Derek Widmayer of the ACRS staff is the 24 designated federal officer for the meeting today. 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
5 member conflicts of interest were identified for 1
today's meeting.
2 During today's meeting, the subcommittee 3
will receive a briefing on the topical report and 4
staff's draft safety evaluation for X-Energy's 5
principal design criteria for the Xe-100 non-light 6
water small modular nuclear reactor.
7 Regarding principal design criteria, which 8
I expect we'll refer to by the acronym PDC many times, 9
we expect to focus today's meeting on X-Energy's 10 process to develop PDCs for the Xe-100 11 high-temperature gas-cooled reactor.
12 Consistent with the NRC's historic 13 reliance on general design criteria for light water 14 reactors, the PDCs proposed by the applicant and 15 accepted by the NRC are requirements that will 16 influence X-Energy's Xe-100 design and final safety 17 analysis report content.
18 The PDCs are therefore integral to the 19 review of the unique aspects of an advanced nuclear 20 power plant. We are reviewing this topical report 21 because it serves as the foundation for the safety 22 design approach of the Xe-100 advanced reactor.
23 For the record and to provide some context 24 for anyone less familiar with the PDC process, there 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 are a couple documents that we'll hear mentioned 1
during today's meeting that are publicly available on 2
NRC's website.
3 These are Regulatory Guide 1.232, Guidance 4
for Developing Principal Design Criteria for Non-Light 5
Water
- Reactors, and NEI 18-04, Risk-Informed 6
Performance-Based Guidance for Non-Light Water Reactor 7
Licensing Basis Development, and we'll add -- I'm sure 8
there's a couple other documents you'll bring up, but 9
those are the obvious two. The subcommittee will hear 10 presentations by and hold discussions with the NRC 11 staff and X-Energy regarding this matter.
12 A portion of the presentation by the 13 applicant and the NRC staff may be closed to discuss 14 information that is proprietary to the licensee and 15 its contractors pursuant to Title 5 U.S. Code, Section 16 552b(c)(4).
17 Attendance at the meeting that deals with 18 such information will be limited to the NRC staff and 19 its consultants, X-Energy, and those individuals and 20 organizations who have entered into an appropriate 21 confidentiality agreement with them. Consequently, we 22 will confirm that we have only eligible observers and 23 participants if there is indeed a closed portion of 24 the meeting. We've only allocated about 20 minutes if 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
7 that's necessary.
1 The ACRS was established by statute and is 2
governed by the Federal Advisory Committee Act, or 3
FACA. The NRC implements FACA in accordance with its 4
regulations found at Title 10 of the Code of Federal 5
Regulations, Part 7. Per these regulations and the 6
committee's bylaws, the ACRS speaks only through its 7
published letter reports.
8 We hold subcommittees like this one to 9
gather information and perform preparatory work that 10 will support our deliberations and final decisions of 11 whether to issue a letter report at the full committee 12 meeting, which I believe we'll be doing in two weeks.
13 All member comments should be regarded as 14 the individual opinion of the member only, not a 15 committee position. The rules for participation in 16 ACRS meetings, including today's, were announced in a 17 June 13, 2019 Federal Register Notice.
18 The ACRS section of the U.S. NRC public 19 website provides a charter, bylaws, member guidance, 20 subcommittee structure, agendas, letter reports, and 21 full transcripts of all full and subcommittee 22 meetings, including the slides presented there. The 23 meeting notice and agenda for this meeting were posted 24 there and can be easily found by typing About Us ACRS 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 in the search field in the upper right corner of the 1
website. Now, the word easy may be subjective.
2 The ACRS, consistent with the Agency's 3
value of public transparency in regulation of nuclear 4
facilities, provides opportunity for public input and 5
comment during its proceedings. We have received no 6
written statements or requests to make an oral 7
statement from the public.
8 We have also set aside time in the agenda 9
at the end of this meeting for any comments from 10 members of the public listening to this meeting. The 11 subcommittee will consider all public comments as 12 appropriate.
13 The subcommittee will gather information, 14 analyze relevant issues and facts, and formulate 15 proposed positions and actions, as appropriate, for 16 deliberation by our full committee.
17 A transcript of today's meeting is being 18 kept and will be made available. For the convenience 19 of our members and staff, NRC staff, advocates, and 20 members of the public, our meeting today, of course, 21 is being held both in person and over Teams, Microsoft 22 Teams. The Teams link information with a telephone 23 bridge line was placed in the agenda on the ACRS 24 public website.
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 When addressing the subcommittee, the 1
participants should first identify themselves and 2
speak with sufficient clarity and volume so that they 3
may be readily heard. When not speaking, we request 4
participants mute your computer microphone on Teams or 5
on the phone if you are on the bridge line. This 6
happens all the time. I'll just reiterate if you're 7
not speaking, please be on mute, as we, of course, had 8
a demonstration right at the beginning.
9 Please do not use any virtual meeting chat 10 feature, that is the chat feature that's in Teams, and 11 this happens a lot too, to conduct sidebar discussions 12 related to the presentations or just to say hi to the 13 friend you see online. Limit this to just reporting 14 on IT problems such as inability to hear speakers or 15 see presentations, or for our staff to communicate 16 generally to all participants that are on the line.
17 Also, for everyone in the room, please put 18 your electronic devices in silent mode, including 19 muting your speaker, microphone, or your laptops. In 20 addition, please keep sidebar conversations in the 21 room to a minimum since the microphones in the ceiling 22 are live.
23
- Finally, for the presenters, your 24 microphones at the table are uni-directional, so 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
10 you'll have to speak in front of the microphone in 1
order to be heard online.
2 Okay, after all of that formality, we will 3
now proceed with the meeting, and I will call on, so 4
I have Stephen Philpott, okay, you're over here to the 5
right, of course, of the NRC to begin today's 6
presentation.
7 MR. PHILPOTT: My name is Steve Philpott.
8 I'm the acting chief of one of the advanced reactor 9
licensing branches in the Office of Nuclear Reactor 10 Regulation. And as Dr. Martin mentioned, the purpose 11 of this subcommittee meeting is to discuss X-Energy's 12 principal design criteria or PDC topical report for 13 their Xe-100 design.
14 As you're aware, X-Energy is an awardee of 15 the Department of Energy's Advanced Reactor 16 Demonstration Program, and they are an early 17 implementer of the Licensing Modernization Project or 18 LMP technology in their licensing approach.
19 This PDC topical report describes 20 X-Energy's development of the principal design 21 criteria for the Xe-100 pebble bed high-temperature 22 gas-cooled reactor. X-Energy developed these PDCs 23 using guidance from, as Dr. Martin mentioned, from 24 Regulatory Guide 1.232, which we commonly refer to as 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 advanced reactor design criteria guidance, as well as 1
the technology-inclusive content of application 2
guidance for non-light water reactors for applicants 3
using the LMP methodology as found in NEI guidance 4
20-07, as well as Xe-100's specific safety functions 5
and design elements. This topical report is intended 6
to support future licensing applications for 7
X-Energy's Xe-100 design.
8 I'd like to start by thanking, expressing 9
the staff's appreciation to the ACRS for your interest 10 and time to review this important topic. I also want 11 to thank the NRC staff and the X-Energy staff that are 12 here for their time and preparation for today's 13 meeting, and for the presentations that the ACRS is 14 going to hear today. So, I look forward to the 15 conversation today, and if there are no questions now, 16 I'm just going to quickly turn it over to X-Energy.
17 CHAIR MARTIN: Okay, the floor is yours.
18 MR. VAUGHN: Thanks, Steve. So, an 19 introduction, I'm Steve Vaughn. I'm the licensing 20 director at X-Energy. To my left, I have Kyle 21 Metzroth. He's the deputy director of Xe-100 systems 22 development. To my right, we have Drew Nigh. He's 23 our manager of risk-informed safety analysis, which 24 also includes PRA.
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 We'll go ahead and get started. As Steve 1
mentioned though, X-Energy did get an award from DOE, 2
the Department of Energy, the advanced reactor 3
demonstration program.
4 PARTICIPANT: Yes, now X-Energy, Steven 5
Vaughn is speaking.
6 MR. VAUGHN: Yes, there are two Steves, my 7
apologies. So, again, X-Energy was awarded the 8
Department of Energy advanced reactor demonstration 9
program award, so here is just a disclaimer of that 10 acknowledgment.
11 So, agenda and objectives, we just did 12 introductions. First, we'll go over at a high level 13 the Xe-100 principal design criteria development 14 process, then we'll focus on general differences from 15 Reg Guide 1.232, which was just mentioned. That's 16 just a short slide.
17 The majority of the content are examples 18 of how we took the MHTGR, which I'll get into in a 19 little bit, and converge with the NEI 18-04, which 20 conformed to the Licensing Modernization Project 21 effort, and then questions throughout obviously, and 22 we can always end with questions and any closing 23 remarks.
24 As mentioned before, we started with Reg 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 Guide 1.232, though again, just a quick history of 1
that, that effort was extremely important for 2
non-light water reactors since the general design 3
criteria is based on large light water reactors, and 4
created advanced reactor design criteria, and then 5
lucky for X-Energy, at the high-temperature gas 6
reactor Appendix C, that Reg Guide had design criteria 7
based on the MHTGR.
8 So, we were given a set of specific design 9
criteria based on our technology. So, we started with 10 that, and then 18-04 came along shortly after. We had 11 a risk-informed performance-based way to develop 12 design criteria based on functions we'll get into in 13 a bit, so those are the two key documents.
14 NEI 21-07, that wasn't mentioned before, 15 but effectively that document took, or provided the 16 industry with guidance from the NRC on how to actually 17 develop a safety analysis report based on 18-04 18 methodology. So, we looked at it as a practical guide 19 to develop, you know, the chapterization of a SAR.
20 And, of course, the NRC's ARCAP guidance, 21 Advanced Reactor Content of Application Project 22 guidance, was issued a couple of years ago, and we 23 also used that as well because it does describe how to 24 address principal design criteria in that.
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14 And the one down below, it's an Xe-100 1
X-Energy document and it's a first example of how we 2
implemented, I'd say, the NEI 18-04 methodology.
3 Drew, myself, and Kyle, and a couple of others were 4
the ones who actually developed this document and 5
styled required safety functions and PRA safety 6
functions, Revision 5. And obviously, there was 7
Revision 1 three or four years ago and we're up to 8
Revision 5, so we're iterating through the functional 9
hierarchy of the Xe-100 safety case.
10 And this is just a picture really that 11 kind of describes what we've already discussed. We 12 start with Reg Guide 1.232, which, you know, I will 13 say it might have some risk-informed elements to it, 14 but was historically maybe more deterministic when it 15 comes to design criteria, and then we bring along 16 18-04 and 21-07 methodology and framework. That tells 17 you kind of what you need to do, but not how to do it.
18 So, that document I just mentioned, that 19 Xe-100 document, that's how we did it is we developed 20 essentially the functional hierarchy from the top down 21 and then from the bottom up, so we decomposed the 22 functions at a high level down to a detailed level.
23 And then when you get here in the green 24 box, the yellow, and blue, and mixed green, our Xe-100 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 PDC, so the topical report you see, I look at it as 1
the convergence of those two paradigms, if you will.
2 CHAIR MARTIN: I'm going to interrupt you 3
just for a second. I noticed that you don't really 4
have like one slide that kind of presents Xe-100, and 5
for the record, you know, you haven't visited the ACRS 6
since before I was on. Just real quick at a high 7
level, kind of explain what the Xe-100 is for anyone 8
that may be less familiar?
9 MR. VAUGHN: Yeah, I'll take a shot at it 10 as the licensing director, although I'll refer to the 11 one in design and safety analysis.
So, a
12 high-temperature gas reactor, our primary coolant is 13 helium. It's a pebble bed reactor using TRISO fuel, 14 and so it's online refueling.
15 So, we have a fuel handling system. As 16 pebbles go through the bottom of the core, they are 17 transferred back up to the top of the core. We have 18 a once-through steam generator, and that's, at a high 19 level, the main power system.
20 The helium is forced through the system 21 via two helium circulators. That's how we move the 22 helium through. And other key safety features are our 23 heat removal system reactor, RCCS, reactor --
24 CHAIR MARTIN: Reactor Cavity Cooling 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 System.
1 MR. VAUGHN: Reactor Cavity Cooling 2
System, there you go. It has both an active and 3
passive capability. And I'm probably missing some 4
other key features, but those are the high level ones.
5 CHAIR MARTIN: Graphite-moderated, I don't 6
know if you said that one.
7 MR. VAUGHN: Oh, yeah, graphite-moderated, 8
yeah.
9 CHAIR MARTIN: So, I wanted to make sure 10 you said the three key things that were assumptions in 11 Reg Guide 1.232, which of
14 MR. VAUGHN: Yeah, so we do have, in 15 between the pebble bed and the core barrel and reactor 16 pressure vessel, there are graphite blocks that 17 provide moderation.
18 CHAIR MARTIN: All right, thank you. You 19 can go on.
20 MR. VAUGHN: I do want to point out that 21 we added some definitions to expand on the 18-04 22 methodology. The ones you see in blue are what we 23 added to the topical report. The ones in black are 24 already defined in 18-04 and 21-07.
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17 And so, you know, the first question, why 1
do you even feel the need to define a term? Well, the 2
SSC classifications of safety-related, non-safety 3
related special treatments, non-safety related window 4
special treatments are defined at an SSC 5
classification level, but they actually didn't define 6
how they tie to the functions.
7 The only one that 18-04 did was the 8
required safety function, which has a very clear 9
delineation to required functional design criteria and 10 safety-related design criteria, but the others didn't.
11 So, you see if you added an NSRST class, 12 SSC classified as NSRST, 21-07 shows there's a direct 13 correlation and it's complementary design criteria, 14 but that term right there, NSRST, wasn't a defined 15 term, and we used basically the language in 18-04, 16 used what was there to define that term.
17 CHAIR MARTIN: And I believe you made a 18 point early on that the reg guide came before the NEI 19 report, so clearly there's some language, you know, 20 that didn't get captured because, of course, the 21 chicken came before the egg in this case.
22 So, you have, you know, taken the work 23 that's been done and deliberations on NEI 18-04, you 24 know, with the benefit not only of just the year 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
18 two that passed between the reg guide, but also the 1
last five years, and have worked it into the language 2
of NEI, excuse me, the Reg Guide 1.232. That was my 3
interpretation as I was reading through your material, 4
correct?
5 MR. VAUGHN: Correct, yeah, and then even 6
within 18-04 itself, they didn't define these terms 7
when we felt the need to. So, for NSRST PSF, what 8
18-04 did do is they described there are two ways to 9
get a classification for NSRST, and that's for 10 specific function or necessary for defense-in-depth.
11 So, we defined this term, defined it 12 functionally essentially, and we did the same thing 13 with non-safety related with no special treatment PSF.
14 And one of the reasons we did that for the one below, 15 the NST PSF, is to draw a direct correlation to this 16 owner-controlled design criteria, which is a term 17 that, you know, we didn't make up, we added, but it's 18 based on 18-04 language.
19 That owner-controlled, owner design 20 requirements, owner-controlled design requirements is 21 a term used in 18-04. We just changed the 22 requirements to criteria just to show that there -- we 23 wanted to make sure it's very clear, the delineation 24 between functions and design criteria throughout, 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 across the entire plant.
1 CHAIR MARTIN: They're not necessarily, 2
just as a clarification, not necessarily design 3
criteria that have a safety aspect to it, yes or no?
4 MR.
VAUGHN:
They're not safety 5
significant, which is a defined term in 18-04. Safety 6
significance includes safety-related in NSRST. Now, 7
those systems that are classified as NST PSFs, you 8
know, the PRA itself is going to model all functions, 9
including NST PSFs, but those functions aren't safety 10 significant, again which has a very clear definition 11 in 18-04.
12 CHAIR MARTIN: Meaning that there could 13 still be value from a defense-in-depth perspective?
14 Even though it can still be complementary, your 15 complementary design kind of covers some of that, but 16 maybe this is kind of clarifying the delineation, the 17 lines. You're crossing the line a little bit to 18 really kind of maybe later in safety analysis prove 19 they're not, you know, they're not really that 20 important to safety for instance.
21 MR. VAUGHN: I mean, there's --
22 CHAIR MARTIN: You're going a step beyond.
23 MR. VAUGHN: It plays a role in defense --
24 they play a role in defense-in-depth, or the need for 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 sufficient defense-in-depth, no, right. That's the 1
assertion that we made is NSRST is sufficient for 2
defense-in-depth, but they do play a role. The NST 3
ones do play a role in defense-in-depth.
4 CHAIR MARTIN: Of course, but ultimately, 5
it's the required functional design criteria, the 6
complementary design criteria that really have the 7
safety role.
8 MR. VAUGHN: And just a terminology thing 9
too, I mean, one of the things we found challenging 10 communicating to our own team is technically 11 everything in the PRA is a PSF, and so like it's a 12 bunch of nested terms and they weren't mutually 13 exclusive, and so this was the attempt to create a set 14 of mutually exclusive terms so that we could clearly 15 communicate which ones we were talking about.
16 CHAIR MARTIN: All right, thank you.
17 DR. SCHULTZ: This is Stephen Schultz. I 18 have a question associated with these new definitions.
19 Is there any reason why this was done specific to your 20 design? The second question is have you been 21 communicating with NEI or others in the industry or in 22 the same position you are with regard to moving 23 forward with their designs to perhaps adopt this same 24 approach?
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21 MR. VAUGHN: Great question. I wouldn't 1
say specific to our design. It was, I guess, specific 2
to, if you want to take the LMP construct and then 3
take the Reg Guide 1.232 construct and merge them.
4 Having these definitions just help keep the accounting 5
clear.
6 So, it wasn't specific to a technology.
7 I think anyone could use it. Have we discussed this 8
with NEI? No. That's a great suggestion and I'll 9
make sure they're aware that we did this and see if 10 other vendors, other folks in the industry want to use 11 it.
12 DR. SCHULTZ: Thank you.
13 MEMBER ROBERTS: Yeah, this is Tom 14 Roberts. What I thought I heard you say is that 15 everything modeled in the PRA is tracked in one of 16 these three categories. Is that right?
17 MR. VAUGHN: Correct, the --
18 MEMBER ROBERTS: That's a lot of 19 functions.
20 MR. VAUGHN: Yes, every function modeled 21 in the PRA is technically called a PRA safety 22 function, right, because it plays some role in 23 responding to events, and so we just made these 24 definitions to help delineate all of those things in 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
22 the PRA.
1 MEMBER ROBERTS: Did you use some sort of 2
metric like a risk achievement worth or something to 3
determine which ones are more important and show up in 4
a CDC?
5 MR. VAUGHN: Yeah, the metric piece risk 6
significance is the definition from NEI 18-04, so I 7
won't repeat it here, but it's consistent with 8
guidance in NEI 18-04.
9 MEMBER ROBERTS: Yeah, I think about 10 important to defense-in-depth. Some things that are 11 important to defense-in-depth might be complementary 12 design criteria. Everything in the PRA helped you 13 model. Therefore, it's important to defense-in-depth.
14 I'm just wondering how distinguished between the two 15 things.
16 MR. VAUGHN: Yeah, so there are two 17 criteria that get you to NSRST. One is risk 18 significance, which is a quantitative criteria, and 19 then the other one is defense-in-depth, which is a 20 blend of qualitative and quantitative criteria 21 outlined in Table 5-2 of NEI 18-04.
22 And when it comes to the qualitative 23 guidelines, you know, we have to interpret those in a 24 certain way to determine which functions are necessary 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 for adequate defense-in-depth versus providing 1
defense-in-depth.
2 MEMBER ROBERTS: Okay, thank you.
3 MR. VAUGHN: So, moving onto general 4
differences from Reg Guide 1.232, so the first three 5
are fairly straightforward, especially the first two.
6 So, we replaced important to safety with the NEI 18-04 7
definition of safety significant. So, again, safety 8
significant has a very clear definition, whereas 9
important to safety did not have such a clear 10 definition in regulatory space.
11 We did remove single failure criterion 12 from all PDC given that NEI 18-04 does leverage the 13 defense-in-depth evaluation approach, which I just 14 mentioned. That's when you go through the DID 15 evaluation for the entire plant, one of the last steps 16 in LMP before you enter it again, and during that 17 process, you kind of solidify the SSC classifications 18 and your defense-in-depth posture.
19 CHAIR MARTIN: Excuse me, question.
20 Regarding the single failure criterion, do you feel 21 like that the single failure criterion could play a 22 role in any LMP or NEI 18-04 approach to the safety 23 case or do you think that NEI -- I mean, I think my 24 read is that it obviously heavily weights, you know, 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 reliability, which is -- but do you think it excludes 1
the use of single failure criteria?
2 MR. VAUGHN: I wouldn't say it excludes 3
it, and I'm sure Drew has some thoughts on this, but 4
I would say the defense-in-depth approach, because 5
you're looking at the entire plant and then LMP, you 6
do your required safety functions, PRA safety 7
functions, you do your SSC classification, you do 8
special treatments effort, and then you do your 9
defense-in-depth evaluation.
10 That, like, say, four-step process ending 11 with the DID evaluation, I feel like is a holistic, 12 integrated approach that I think gets you to a better 13 safety case than just applying single failure 14 criterion multiple times, right. I think you can miss 15 something if you just apply the single failure 16 criterion in isolation.
17 CHAIR MARTIN: Okay, I appreciate your 18 answer. Maybe it will come up again here.
19 MR. VAUGHN: And we did replace, again, 20 the terminology. We want to keep them as consistent 21 as we can. We replaced postulated accident and 22 accident conditions with the NEI 18-04 defined 23 licensing basis events or LBEs, so AOO, TBE, and DBA.
24 So, the fourth one was, you know, new. As 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 we went through the process, we realized that the 1
MHTGR DC you see there, 18-32, 36, 37, 45, 46 to 72, 2
all talk about essentially monitoring inspection and 3
testing surveillance, and they're all system-specific 4
essentially.
5 And what we did is we took all of those 6
and really distilled it down to the essence of what 7
those criteria were really trying to get at. And it's 8
when you design a plant, you want to design for the 9
ability to monitor, inspect, test, and surveil through 10 the life of the plant, which is a great design 11 criteria to have.
12 What we did is we consolidated it down 13 into one and made sure we didn't leave anything out, 14 and then applied it to every system that is classified 15 as safety-related or NSRST. So, to me, it gave more 16 flexibility in language and we didn't miss anything 17 with it, so that's one thing we did to kind of 18 consolidate.
19 CHAIR MARTIN: Yeah, I thought it was one 20 of the bolder things you did in deviating from the reg 21 guide, but, you know, again, the committee expresses 22 their opinion, but I thought you caught something 23 there. You know, there's a lot of overlap, right, and 24 certainly by including statements related to testing, 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 surveillance, and the other ones, I mean, you're 1
covering everything, but I think what you did by 2
bringing in C-6 and really elevating it in the sense 3
that we have a design criteria that addresses all of 4
those things.
5 You know, I think it's unnecessary to 6
repeat and it allows you to focus maybe more 7
specifically on what all of the other DCs are really 8
saying. So, I don't know. It would not be unique to 9
X-Energy there, but I did think it was an interesting 10 observation you all must have had as you went through 11 that.
12 And I almost felt like it's elevating 13 monitoring, inspection, testing, surveillance by 14 having kind of the one central one as six as opposed 15 to kind of spreading it out and kind of reminding 16 everybody oh, yeah, you've got to do all of that.
17 MR. VAUGHN: Yeah.
18 CHAIR MARTIN: Right? So, I don't know.
19 That's something for the staff obviously to consider 20 in other reviews for sure, but actually my opinion, I 21 think it was a good move, that it does provide more 22 focus by having the one. All right, you cover it and 23 it covers for all of those things.
24 MR. VAUGHN: I appreciate that because 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
27 does force you to critically think for every 1
safety-significant system, what do I need to do in 2
this space? And it makes sense that the general 3
design criteria, the plants were already designed, 4
right, so they already kind of knew what the systems 5
were, so it's hard to not bring in system-specific 6
criteria because the designs were already there. So, 7
we wanted to, again, take a step back and get generic 8
to force you to think about it.
9 And now we're getting into the details.
10 So, again, you know, I selected these. I selected the 11 examples really based on -- because they're good 12 examples of how we took the 18-04 approach 13 essentially, but obviously in a PDC and a topical, we 14 can discuss. I kind of went in order starting at 11.
15 Well, I think PDC 10 describes SARRDL. The --
16 CHAIR MARTIN: Just for the record, define 17 SARRDL.
18 MR. VAUGHN: Yeah, SARRDL is specified 19 acceptable radionuclide release design limit. For 20 those familiar with SAFDL, it's the HTGR version or 21 TRISO-X version of a SAFDL. So, in essence, it's 22 described in PDC 10. So, I didn't bring that up 23 because it's not functional.
24 I guess one thing I should point out, when 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 navigating through and converging the 232 design 1
criteria and 18-04, we were realizing all of the 2
design criteria are actually functional, and you 3
really had to think about them. Is there a function 4
here or just design criteria?
5 And the ones I'm showing here are the ones 6
that truly were functional, and that's why they 7
blended so well to the 18-04 method. So, PDC 10 8
describes SARRDL. We didn't change any words from 9
what was in Reg Guide 232, but really that's the first 10 place you see that limit, which is a really important 11 one for us, SARRDL.
12 So, I mention that because it is using the 13 CDC down below, but we did take PDC 11 and 12, so 14 reactor protection and suppression reactor power 15 oscillations, and again, combined them, made sure we 16 didn't leave anything out, and decomposed them into 17 two PDCs, so there's an RFDC 11 and a CDC 11.
18 And one thing to point out here, you know, 19 this RFDC 11 is also really important and it ties into 20 our RFDC 26, which we'll get into in a little bit.
21 So, it is one of the two means to supporting 22 controlled reactivity because our reactor inherent 23 protection is by core design, the strong negative 24 temperature coefficient reactivity, that's how 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
29 control reactivity during LBEs.
1 So, this, and coupled with what we'll see 2
in RFDC 26, collectively have those two means. So, it 3
is a little bit awkward that you need to take 11 and 4
26 to support a function called control reactivity, 5
but that's, at the end of the day, that's what we're 6
left with. There might be an opportunity in the 7
future to consolidate those.
8 And then the last line there is showing 9
that it does align with RSF, required safety function, 10 1.1.1, controlled reactivity within the inherent 11 reactivity feedback.
12 And I guess one thing to point out here, 13 between RFDC and CDC, you'll see something common 14 where RFDC align design basis events to design basis 15 accidents, and CDC align with anticipated operational 16 occurrences.
17 All
- right, PDC 13, instrumentation 18 control, this one was a tough one to break out on its 19 own into RFDC, CDC, and OCDC, but it does contain all 20
-- the RFDC here aligns with control reactivity with 21 moveable poisons, so it obviously has a tie to control 22 reactivity, and the RSF isolate water steam ingress.
23 You know, maybe we should have spent some 24 time to go over not just the design, but some of 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
30 required safety functions, but there's a functional 1
tree, that document shown down below, that energy 2
implementation of 18-04. There's a decomposed tree of 3
functions. So, you know, 1.3 is control water steam 4
ingress. Under 1.3, there's a 1.3.1, isolate water 5
steam
- ingress, right, so you can see the 6
decomposition. We don't show that in these slides.
7 I do believe that the previous, the only 8
other time we briefed the ACRS was Kyle Martin, right.
9 They described all of that. I think in those slides, 10 I think there's a picture of those functions.
11 CHAIR MARTIN: And you're referring to 12 your visit in May of 2023, correct?
13 MR. VAUGHN: Correct, yeah, I believe we 14 did break down at some level the functions there, but 15 without that kind of decoder ring, it's hard to kind 16 of see all of this, but I just wanted to point those 17 out. And then on a CDC level, it's really similar to 18 control reactivity, the moveable poisons.
19 There's an NSRST PSF associated with that, 20 and then controlling heat removal with active means, 21 and then maintaining helium pressure boundary, 22 pressure during transients. Those are some other PSFs 23 that align with the CDC.
24 And on the control design criteria, 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
31 is instrumentation control needed to keep the plant 1
just at a normal operating state, so the I&C obviously 2
supports that. The challenge with this one is to --
3 you'll see later in DC 34, it was more straightforward 4
to create an RFDC CDC and OCDC, but this one with the 5
wording, it was really hard to compartmentalize them 6
into three separate phrases, so, you know, they all 7
have their own elements to it. Any questions on this 8
one?
9 Moving on to PDC 15, again there's no RFDC 10 element to this, but I did want to clarify that the 11 helium pressure boundary design doesn't provide a 12 required safety function for the HTGR or Xe-100, so it 13 aligns with a CDC, not an RFDC, and specifically, the 14 function aligns to prevent loss of the helium pressure 15 boundary integrity, and down below, it aligns with 16 normal operations and anticipated operational 17 occurrences.
18 Moving on to PDC 16, it essentially 19 defines from a design criteria perspective our 20 functional containment. The RFDC portion of it is 21 retain radionuclides in our fuel particles and 22 pebbles, that RSF 1 is at the top of our hierarchy of 23 our required safety functions.
24 That is the start, and in the picture down 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 below, that retain radionuclides in the fuel particles 1
and pebbles is to control reactivity, control heat 2
removal, and control water steam ingress.
3 Those are the
- three, and then 4
tangentially, you have, you know, maintain core 5
geometry, which kind of, you know, it's kind of, it's 6
crosscutting of all of them, but at a high level, 7
that's our functional hierarchy, and then down below, 8
those three, you know, you can decompose it further.
9 CHAIR MARTIN: Real quick, the language 10 you use there in your required functional design 11 criteria, to ensure that the functional containment 12 design limit. Now, could you have used SARRDL there 13 and said the same thing or is there expectations of 14 something more than SARRDL?
15 MR. VAUGHN: Great question. Currently, 16 the thought is that the functional containment design 17 limit at a high level is the frequency consequence 18 target in 18-04, that chart.
19 CHAIR MARTIN: That's SARRDL.
20 MR. VAUGHN: SARRDL is a little bit 21 different because SARRDL, you need to maintain SARRDL 22 during normal operations and anticipate operational 23 occurrences, yeah, but beyond that, SARRDL can be 24 exceeded.
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33 CHAIR MARTIN: But the SARRDL would cover 1
the whole spectrum from 10 CFR 20 through evaluation 2
guidelines for DBAs and even beyond design basis, that 3
whole frequency consequence.
4 MR. VAUGHN: It's tough to describe.
5 Maybe we could talk about this during the closed 6
portion if we can, but at a high level, yes, SARRDL, 7
if you brought up PDC 10, the SARRDL limit does not 8
need to be met during design basis events or design 9
basis accidents, similar to SAFDL for DBA. You know, 10 you expect SAFDL to be exceeded during a design basis 11 accident. So, likewise for SARRDL, they kept the 12 same.
13 CHAIR MARTIN: Okay, we'll just table that 14 and keep on going.
15 MEMBER ROBERTS: Yes, Tom Roberts.
16 There's a requirement in 18-04 to look for cliff edge 17 effects. Does that factor at all into CDC and 18 functional containment? Because it seems like cliff 19 edge effects may require assessment of scenarios that 20 are beyond design basis or design basis accidents, and 21 yet you still want to have resilience in the 22 functional containment particularly. Is that a factor 23 here and how is that accounted for?
24 MR. VAUGHN: I mean, so the fact is when 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 we implement our 18-04 methodology, we will look for 1
cliff edge effects, and I would say that if we -- you 2
know, this whole process is iterative, right? So, if 3
we go through and we identify something that comes out 4
of that evaluation, there's the potential to add 5
something to this to be able to account for it, but, 6
you know, right now, we don't have anything that 7
covers it explicitly, but in going through our 18-04 8
methodology, we will evaluate cliff edge effects.
9 MR. METZROTH: And I'll add that the PDC 10 pertain to design basis events, and AOOs, and design 11 basis accidents, whereas cliff edge effects, in my 12 opinion, generally pertain to beyond design basis and 13 lower frequency events than that. So, yes, we will 14 still get requirements for our design from evaluating 15 cliff edge effects through the 18-04 approach, but not 16 necessarily through the PDC.
17 MEMBER ROBERTS: Okay, thank you.
18 MR. VAUGHN: The RFDC portion of this is 19 focused on the fuel particles and pebbles, whereas the 20 complementary design criteria focuses on maintaining 21 a pressure boundary. That's the third barrier where 22 the particles and pebbles are the first two, meaning 23 that aligns with the previous one where the helium 24 pressure boundary integrity isn't a
required 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 functional design criteria that aligns with the CDC.
1 All right, so PDC 26 was a challenging one 2
to align all of the wording, but we did break it down 3
into not only an RFDC CDC and OCDC, but also a PDC, 4
and this, you'll recall that we didn't change the 5
wording much, but that's the fourth. If you look at 6
the GDC currently, the like four pieces to it, the 7
fourth one is that bottom one, and we just did 8
maintain that.
9 CHAIR MARTIN: Yeah, I mean 26 always 10 comes up with a new design. It seems like you're 11 focusing a lot of it on an active system requirements.
12 You're using the words moveable poison to attempt to, 13 say, credit passive response, or that comes in -- I 14 mean, it exists in your design because we're all 15 familiar with high-temperature gas reactors and their 16 performance with, you know, large negative feedback 17 with temperatures, but there's -- how does that play 18 into satisfying the design criteria? Because it seems 19 like you have like the implication that the statement 20 is that, you know, you have two active systems 21 basically.
22 MR. VAUGHN: Well, so RFDC 11, the reactor 23 inherent protection, is the passive means of 24 controlling reactivity, and then this RFDC up here 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
36 the, you know, the moveable poison.
1 CHAIR MARTIN: So, it's completely 2
separate?
3 MR. VAUGHN: Yeah, and they're separate, 4
so that was that, two independents, but that was the 5
challenge of, unfortunately, you have to look at both 6
RFDC 11 and RFDC 26 collectively.
7 CHAIR MARTIN: Those were the two, yeah, 8
okay.
9 MR. VAUGHN: That's the challenge, and 10 again, for our design, it's a removal of power gravity 11 drop is the, sort of that active -- that would be the 12 poisons portion.
13 CHAIR MARTIN: Okay.
14 MR. VAUGHN: And if you look at the CDC 15 notes, they're not too off, but one focuses on --
16 again, CDC focuses on AOOs and the OCDC focuses on 17 normal operations.
18 PDC 30, at the top, it is integrity of the 19 reactor helium pressure boundary. So, the RFDC 20 focuses on, this is again controlling water steam 21 ingress, in this case, isolating the water steam 22 source, and that's the event sequence that our design 23 needs to protect against and it's a required safety 24 function, so that's what this RFDC focuses on.
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37 CHAIR MARTIN: Yeah, you're kind of 1
getting into the section where, again, I'm noticing 2
from the staff's review, and of course there's 3
limitation and condition related to events.
4 MR. VAUGHN: Right.
5 CHAIR MARTIN: I know you haven't 6
presented events yet. I mean, the PDC is the very 7
first topical reports, and nominally you would 8
consider -- nominally when we refer to light water 9
reactors and other designs, a loss of coolant 10 accident, or in this case, the depressurized loss of 11 coolant circulation event where you could have area 12 risks. And so, PDCs like this and maybe the next one 13 kind of touch into events, okay.
14 Now presented
- events, that's been 15 acknowledged by the staff in their review, so, you 16 know, it's kind of a TBD, but certainly that is 17 something that, you know, an external stakeholder 18 might look at kind of going, you know, okay, it's a 19 little different, but we know there's kind of an 20 eye-opening on that anyway.
21 MR. VAUGHN: And this was often formed by 22 our PRA and our initial set, and so that was to try to 23 bring the technology --
24 (Simultaneous speaking.)
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38 MR. VAUGHN: Yeah, exactly. And PDC 34 is 1
about residual heat removal. I think the MHTGR DC 2
just said passive heat removal, but like that 3
definitely applies to us. The reactor cavity cooling 4
system has a passive mode. That ties with the 5
required principal design criteria. So, we have two 6
active means of removing heat.
7 The CDC focuses on one system to address 8
AOOs and the other system is internal operations, so 9
it aligns with owner-controlled design criteria. This 10 PDC was definitely more amenable to compartmentalizing 11 the three separate criteria as opposed to the I&C 11 12 and 13.
13 We have two more. So, at the end, we get 14 to the reactor vessel and reactor system structural 15 design basis. This is where we get into maintaining 16 core geometry. So, this is a required functional 17 design criteria to maintain core geometry, and some 18 things you'll see, we did that.
19 You know, core internal structure is here 20 too. That was one addition we made to add more 21 clarity from what we inherited from the MHTGR design 22 criteria. Other than that, we didn't change too much.
23 CHAIR MARTIN: 70 was something that GDCs 24 don't have, but obviously, there's a uniqueness 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
39 high-temperature gas reactors. You know, we're 1
relying on heat removal, passive heat removal, kind of 2
inside-out reactors if they've got a cavity cooling 3
system, and something like this, a design criteria 4
that focuses on everything else besides the fuel is 5
very, very important, so that's really more for maybe 6
people that are not as familiar, but that's really a 7
very key one there.
8 And we've come from other, you know, 9
safety analysis programs, and applications, and, you 10 know, other design centers. There's still the 11 expectation that you maintain thermal limits of, you 12 know, core internals and what have you, oftentimes in 13 particular, water.
14 You know, the margins are huge with gas 15 reactors and things are high temperature, so you don't 16 always know what component is being threatened. I 17 mean, in doing fuel, I've done a lot of research.
18 There's probably a lot of margin on that, so it might 19 be something else, so 70 is particular important.
20 MR. VAUGHN: Exactly, and then likewise, 21 this is focused on the reactor pressure vessel and the 22 core internals, and then you take a step back. We 23 also need to protect what's supporting the actual 24 reactor pressure vessel and the core, and again, 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
40 reactor building.
1 So, obviously, you need to maintain the 2
structural integrity here to maintain the core 3
geometry. So, 70 and 71 kind of double to maintaining 4
core geometry. So, 1.42 is, I would say the structure 5
itself, and then 1.4.1 is the maintaining pressure 6
boundary and the actual core itself, so.
7 CHAIR MARTIN: But them I'm just going to 8
be nosy to Kyle, and this puts a bit more of a burden 9
of your safety analysis, but eventually you'll come to 10 us or come to the staff, and maybe you've already done 11 some of that. Are you going to have a true like 12 integrated safety analysis which kind of looks at 13 normal limits and all of these things all together and 14 your transient analyses?
15 MR. METZROTH: Yeah, sure, I mean, we have 16 to look at, you know, events that consider challenging 17 the structural capacity of the building. We have to 18 look at events which, you know, it brings all of those 19 things together. So, yes, it is -- we have a very 20 integral safety analysis that considers all of those 21 factors.
22 CHAIR MARTIN: Yeah, it's certainly a lot 23 more complicated --
24 MR. METZROTH: Right.
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41 CHAIR MARTIN: -- you know, maybe than a 1
light water reactor in some ways, meaning you're 2
tracking so many more things.
3 MR. METZROTH: Well, I'm not sure that it 4
ends of being -- I mean, you do have to do containment 5
analysis in a light water reactor. You know, we don't 6
have containment. We're not doing --
7 CHAIR MARTIN:
- Yeah, but are you 8
integrating that all together with your --
9 MR.
METZROTH:
It doesn't have to 10 necessarily all be integrated. I mean, it's integral 11 in the fact that we have a tool set which spans the 12 spectrum of all of the things that have to be covered, 13 and that could be done by analysis one, feed things 14 into analysis two, and get the right boundary 15 conditions, et cetera. I think at a high level, it's 16 consistent.
17 CHAIR MARTIN: They are still segregators.
18 MR. METZROTH: Yeah, correct.
19 CHAIR MARTIN: And there are objectives.
20 MR. METZROTH: Right, it's a different 21 interpretation of integrated, but yeah, it's still 22 integrated in the fact that we're considering it all, 23 but it's not one giant analysis that has to factor in 24 everything.
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42 MR. VAUGHN: That's the end of the 1
presentation.
2 CHAIR MARTIN: All right, I'll turn to my 3
fellow members. Are there any further questions, 4
consultants? All right, I don't see any.
5 MEMBER ROBERTS: Yeah, one question.
6 Greg, 1.232 has a requirement to evaluate any unique 7
design features of your plant and determine if there's 8
any additional design criteria required for that.
9 Now, you've got a MHTGR, which you've got the benefit 10 of an appendix since it was basically written from 11 that.
12 So, it would seem reasonable that you 13 would have included it. You know, it covers you, but 14 the point is, is there anything unique about your 15 plant design or are you thinking about adding a design 16 criteria or do you consider you don't have to by the 17 reg guide?
18 MR. VAUGHN: The water steam was discussed 19 in the MHTGR DCE. I think I changed the wording a 20 little bit, but that was the only -- we didn't find 21 anything new, like a new licensing basis event we 22 needed to withstand to create a new design criteria.
23 MEMBER ROBERTS: Right.
24 MR. METZROTH: We utilized our early 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 version of our PRA to basically systematically 1
evaluate whether that was the case, and in going 2
through it, we found that, you know, all of the events 3
that considered the technology was pretty well 4
covered. We had to rearrange some things, but pretty 5
well covered by the PDC that were there.
6 MEMBER ROBERTS: Okay, thank you.
7 CHAIR MARTIN: Any further questions?
8 MEMBER KIRCHNER: Bob, this is Walt, yes.
9 CHAIR MARTIN: Hi, Walt.
10 MEMBER KIRCHNER: Could we go back to 16, 11 functional containment design?
12 MR. VAUGHN: What's your question, Walt?
13 MEMBER KIRCHNER: I'm just looking at that 14 and wondering versus what is in the reg guide, whether 15 this is meant to be as expansive as the reg guide.
16 The reg guide emphasizes multiple barriers.
17 Obviously, we have the different layers in the TRISO 18 particles and the fact that they're in pebbles. Is 19 that -- I'm just looking at the choice of words versus 20 what was used in the reg guide.
21 CHAIR MARTIN: Yeah, I think my comment at 22 the time was related to this, the language of 23 functional containment design limit. What all does 24 that mean? And I was looking for, you know, maybe 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 something more narrow. It seems like for me, it 1
hasn't been completely defined, you know, but it could 2
mean a lot, right, and it seems to me that that was 3
your -- it's kind of your answer. It's not just --
4 MEMBER KIRCHNER: Yeah.
5 CHAIR MARTIN: It's something called 6
functional containment design limit, so it can kind of 7
create a much larger box.
8 MR. VAUGHN: Effectively, the dose limit 9
is what we are aiming for, but that may derive back to 10 other criteria on SSCs that we would then create 11 specific limits for after we do all of the iterations 12 of the analysis.
13 CHAIR MARTIN: Sure, we still have thermal 14 limits. You know, you still got to look at, say, 15 1600C and TRISO limits --
16 MR. VAUGHN: Exactly.
17 CHAIR MARTIN: -- and stuff like that.
18 There are still kind of SAFDLs. You know, they're 19 kind of buried under all of that.
20 MR. VAUGHN: But we have to make sure to 21 derive it because, you know, it's not as -- TRISO 22 isn't as discrete as other, you know, in how it 23 exhibits radionuclide release as other fuel forms, and 24 so it's a little continuous, and so that's why we sort 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 of look at okay, we meet dose limits, and then we make 1
sure we want to derive back from that, you know, 2
because our safety analysts maybe want to have, well, 3
give me a number to shoot for and we want to derive 4
that back from the dose limit, and so there's just a 5
myriad of things that we could evaluate, but we 6
haven't got all of that in detail defined. We're 7
focused on the dose limit.
8 MEMBER KIRCHNER: What I'm tripping over 9
here is the second half of this where the pressure 10 boundary, the helium pressure boundary is not exceeded 11 during AOOs. Could you just elaborate on that? That 12 seems to me rather restrictive or less expansive than 13 the actual reg guide. And I understand why you're 14 partitioning, but I want to hear why you -- what's the 15
-- what AOOs? Why is it limited to AOOs?
16 MR. VAUGHN: So, I think what we're trying 17 to do here with PDC 16 is emphasize the different 18 between the SSCs performing the required functional 19 design criteria piece and the complementary design 20 criteria piece.
21 And the point of 16 is that the criteria 22 related to the RFDC or the requirement coming from the 23 RFDC is only applied to the fuel particles and 24 pebbles, whereas the requirement coming from the CDC 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 links back to, I guess, creating defense-in-depth and 1
AOOs and the requirements from that CDC.
2 MEMBER KIRCHNER: Why just AOOs?
3 CHAIR MARTIN: Well, you have the required 4
functional design criteria that covers the design 5
basis events, right. You've segregated -- and 6
earlier, when you said, you know, AOOs and CDCs go 7
together, you were almost begging for a question it 8
seemed like.
9 (Laughter.)
10 CHAIR MARTIN: This is a little bit novel 11 there.
12 MEMBER KIRCHNER: Well, here is the 13 question.
14 MR. VAUGHN: So, it relates back to the 15 basis for the classification of the functions. So, 16 for -- within NEI 18-04, Table 5-2 provides 17 qualitative guidelines for evaluating if you have 18 sufficient plant capability for defense-in-depth, and 19 there's a guideline in there that pertains to AOOs and 20 it says that you should minimize challenges to 21 safety-related SSCs and AOOs.
22 So, as a result of that guideline, it 23 leads to a safety classification on the helium 24 pressure boundary. There are events, there are AOOs 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 where we challenge safety-related SSCs, the fuel, such 1
that we need to have a requirement on the boundary to 2
create adequate defense-in-depth for those specific 3
events.
4 CHAIR MARTIN: Right, I mean, typically, 5
the limits associated with AOOs are more restrictive, 6
right, to the point you made. I guess my curiosity is 7
couldn't these CDCs just be part of the required 8
functional design? I mean, there's no less rigor, I 9
mean, for the work you do.
10 I mean, in some ways, the language maybe 11 deceives us, but terms like required functional design 12 criteria versus complementary design criteria, I think 13 it's trying to say there's some kind of secondary 14 importance associated with a word like complementary, 15 but it's not, right? I mean, when you go in practice, 16 you don't do anything different than --
17 MR. VAUGHN: This really derives from the 18 fact that these functions are performed by systems 19 based on a certain classification, right. This is 20 bringing in the 18-04 piece of it, right, and so in 21 the fact that we have identified there are things that 22 satisfy NSRST PRA safety functions. For the Xe-100 23 design, that's all based on defense-in-depth.
24 We don't actually have risk significant --
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 we haven't identified risk-significant SSCs that would 1
get you to NSRST that way. We get to NSRST purely 2
through defense-in-depth, and so a lot of the CDC 3
thinking that goes into here is because we've gone 4
through the PRA, we've done an initial classification.
5 All of the NSRST SSCs come out through 6
defense-in-depth, and as Drew mentioned on the Table 7
5 through guidelines and how it talks about AOOs, 8
that's how that language gets in there. So, it's a 9
reflection of the function we're asking it to perform 10 in a defense-in-depth capacity based on how NEI 18-04 11 points you in that direction. So, that's where some 12 of that language comes from.
13 MR. METZROTH: And I can just expand.
14 I'll give kind of like a counter-example here where 15 let's say like in design basis accidents, we were 16 relying on the helium pressure boundary to retain 17 radionuclides, to perform that required safety 18 function in those design basis accidents. If that 19 were the case, the second part of this PDC would 20 actually be an RFDC.
21 That required functional design criteria 22 would relate back to a required safety function. In 23 this case, since it's a defense-in-depth function, 24 NSRST PSF, it has a CDC. Bob, your point is well 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 taken. What's the difference between calling it RFDC 1
or CDC? The point is just to trace back to the origin 2
of the requirement.
3 MR. VAUGHN: And when you talk about 4
rigor, I mean, we still have to apply special 5
treatments. When we have an NSRST system, we'll apply 6
special treatments. That means design codes and 7
standards. We select those based on, you know, how 8
they play into the safety case, and so you can still 9
get to a certain level of rigor on that based on, you 10 know, the special treatments that you select. So, 11 you're right, it doesn't necessarily mean a difference 12 in level of rigor because we still have special 13 treatments to select for those systems.
14 CHAIR MARTIN: Walt, did you have anything 15 else to add on your question, original question?
16 MEMBER KIRCHNER: I'll wait for the staff.
17 Thank you.
18 CHAIR MARTIN: Okay, yeah, I think it does 19 kind of present some questions for the staff too.
20 MEMBER ROBERTS: Yeah, Walt, I think your 21 question is related to the one I asked about the cliff 22 edge effects assessments and how that might be part of 23 the outgrowth of the design requirements, because the 24 original PDC said that there will be, where are 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
50 exact words at, multiple barriers internal and/or 1
external to the reactor. So, what they seem to have 2
done is define what those multiple barriers are for 3
all three classes, AOOs, design basis events, and 4
design basis accidents, and so what they've done is 5
made the requirement more specific, but it seems to 6
track to what it says.
7 But what neither one says is there should 8
be defense-in-depth for events that are beyond, you 9
know, what's modeled design basis events and design 10 basis accidents, and whether there's some element of 11 the multiple barriers that that will spawn. It sounds 12 like that's future work.
13 And, I mean, another idea to sit in is 14 when you look at the reasonable but beyond design 15 basis categorization and you come up with well, I've 16 just blown through all of my barriers that I had, so 17 I no longer have multiple barriers, maybe I need to 18 add one more for that. It sounds like that would be 19 a reasonable outcome, what you get there. Is that 20 right?
21 MR. VAUGHN: That's correct and there's 22 also a barrier beyond the helium pressure boundary, 23 but we don't have it listed here because it's not 24 necessary for defense-in-depth, and that would be 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 helium pressure boundary and the reactor coolant.
1 That is a barrier functional containment.
2 But based on our design and what we've 3
done in 18-04 space and the PRA, we'll have to 4
obviously support this with associated stage analysis 5
and does it rise to the level of a NSRST PSF and 6
staff-associated complementary design criteria? But 7
it is still part of the defense-in-depth picture.
8 It's just not necessarily sufficient for it.
9 MR. METZROTH: And I think when you think 10 about something like -- you know, we actually debated 11 this quite a bit. And when you look at something like 12 the reactor building, we sort of thought about some of 13 these functions and the criteria that were coming out 14 of it. It's like what design requirement am I giving 15 a designer, right, like that's really what this has to 16 flow down to.
17 You know, and so the building is kind of 18 there, correct. It's there. It's part of 19 defense-in-depth. It's not needed for adequate 20 defense-in-depth. We will still evaluate it as part 21 of the defense-in-depth philosophy, but I'm not going 22 to hand the designer a requirement that says, right, 23 you know, provide this much on defense-in-depth.
24 These were things were there were specific 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 requirements that we could hand down and actually 1
provide the designer versus it's there and we're going 2
to evaluate it as part of it. So, you're right, it 3
doesn't probably capture all of that picture, but 4
there are other SSCs that are contributing that are 5
modeled in the PRA.
6 MR. VAUGHN: Tom, I just want to make sure 7
we're answering your question though. Are you 8
wondering why beyond design basis events aren't like 9
mentioned in the topical report?
10 MEMBER ROBERTS: No, it was more follow-up 11 on Walt's point about the multiple barriers verbiage 12 was taken out and replaced with some specifics about 13 what your design does, and so that takes, you know, a 14 principle and replaces it with a specific design, and, 15 you know, whether that risks losing what the principle 16 actually is when you do these more detailed analyses 17 and find that maybe you're still achieving this 18 standard design criterion, but not the underlying 19 principle, and you need to go back and make sure 20 you're covering that, and so I think you've answered 21 that question.
22 MEMBER KIRCHNER: Could you go back then 23 to your last criterion, your last illustration? This 24 is Walt again. I think it's number 70 for 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
53 building, excuse me, 71. That's it. Now, since 1
you've brought it up with regard to giving your 2
designers some criteria for the building design basis, 3
what about controlling unmitigated moisture and air 4
ingress?
5 Assuming you have a rupture in the primary 6
helium system boundary, are you going to provide a 7
functional requirement for the reactor building to 8
actually play a role in terms of a confinement 9
function?
10 MR. VAUGHN: So, well, hold on a second.
11 So, confinement and, and air ingress.
12 Let me address the air ingress piece of 13 that first.
14 When we look at our PRA and we look at the 15 events that are in the, you know, down at the DBE 16 region and the DBAs we derive from it, we dont have 17 credible scenario that leads to air ingress; right?
18 So, this is why were not, were not including that in 19 here because this isnt even informed by our initial 20 PRA.
21 Thats why we dont have a specific 22 criteria on it.
23 MEMBER KIRCHNER: Wait a minute. Stop.
24 You classified your helium pressure 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 boundary in a separate category only for AOOs. So, 1
that suggests that you could have a failure in your 2
pressure boundary, possibly a large failure.
3 MR. NIGH: This is Drew.
4 I think what Kyles trying to say is 5
theres no scenario that could lead to a significant 6
amount of air ingress such that it affects the 7
radiological consequences. Like, yes, a breach in the 8
pressure boundary eventually leads to some amount of 9
air ingress.
10 CHAIR MARTIN: Thank you.
11 MR. NIGH: I believe analyzed all those 12 scenarios occur, and the impact of air ingress as a 13 result, and it basically showed that, the physics, 14 that there is no significant amount of air ingress 15
- for, for those events that would alter the 16 radiological consequences of an impact.
17 MEMBER KIRCHNER: Okay. All right, thank 18 you.
19 CHAIR MARTIN: Yeah, I think thats one of 20 the challenges of us looking at the PDCs at this stage 21 because weve not seen your, like, you know, your 22 safety analyses and we havent seen the PRA. And I 23 think it puts more burden on staff, you know, to kind 24 of recognize, you know, this is coming first, 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
55 theres only so much information. It really is 1
otherwise ready for primetime.
2 And Ill probably bring it up in a second 3
here when we talk to the staff.
4 At the end of the day there can be no 5
limitations in conditions more than likely; right? I 6
mean, all of this has to be resolved. I mean, there 7
is no limitation in conditions on the GDC; right?
8 They are what they are.
9 And so, this is still kind of a work in 10 progress. Anything could change. You could learn 11 something in the next few years that drives, you know, 12 a tweak to what you have today.
13 It really puts more responsibility on the 14 staff to stay on top of that and keeping -- you know, 15 you see a lot more than we do. You see a lot more 16 than the public sees. And you should be sensitive to 17 that because otherwise youre going to get questions 18 that maybe in your mind have already been answered but 19 that havent been answered for the rest of us.
20 And so, you see some of that even from, 21 say, todays conversation. But, you know, I think 22 its good to air out this, you know, for the record 23 that this is something that will continue.
24 I think, you know, my personal opinion 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 since we provide this, you know, youve done a pretty 1
good job. I think youve taken the task of 2
integrating it before, and the Reg Guide 1.23 together 3
very seriously, and there might be value to from other 4
design centers.
5 So, this involves designs, the first one 6
through does a lot of work, you know, could very well 7
be to the benefit of other people who get it for free.
8 Thank you from 16th Street.
9 But I dont have any further questions.
10 I know we are, like, way early on the schedule. And 11 Im going to need a little help on how do we manage 12 schedule and how we should.
13 MR. SNODDERLY: So, I think the first 14 question -- this is Mike Snodderly from the ACRS 15 staff.
16 Right now the agenda calls for breaking.
17 This is a logical time, but it is early. So, I think 18 the question is break or do you want the staff to come 19 up?
20 CHAIR MARTIN: I would say lets go ahead 21 and have a 15-minute break. Again, this keeps us 22 pretty, pretty early on all things considered. But 23 Im up for tea, so.
24 So, how about, you know, I hate to 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
57 long break, but how about till 10:00 oclock? Is that 1
okay? Anybody have any heartburn with that?
2 MR. SNODDERLY: Youre the chairman.
3 CHAIR MARTIN: All right. There you go.
4 Well recess until 10:00 a.m.
5 (Whereupon, at 9:40 a.m.,
the 6
above-entitled matter went off the record, and 7
reconvened at 10:00 a.m.)
8 CHAIR MARTIN: Were going to reconvene our 9
hearing here this morning.
10 We have heard from X-Energy. And were 11 going to move into staffs presentation of their 12 evaluation. I believe Adrian Muniz will be leading 13 our discussion for the introduction part at least.
14 Go ahead.
15 MR. MUNIZ: Thank you.
16 Good morning. My name is Adrian Muniz 17 Perez. I am the lead product manager for the review 18 of the X-Energy Xe-100 design.
19 Sitting right next to me is Ian Jung, a 20 senior reliability and risk analyst, and lead tech, 21 technical leader for the X-Energy design.
22 And right next to him is Dan Beacon. Hes 23 supporting their view on his integral part of the core 24 team design team, design 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
58 We are all staff members of the Office of 1
Nuclear Reactor Regulation, NRR, Division of Advanced 2
Reactors and Non-power Production and Utilization 3
Facilities, also known as DANU.
4 We are here today to present on the NRC 5
staff review of X-Energys principal design criteria 6
topical report.
7 Next slide. Thank you.
8 As presented during X-Energys 9
presentation, the topical report describes their 10 process for developing the principal design criteria, 11 or PDC, for their design and the resultant PDCs coming 12 off this process.
13 The staffs evaluation documented review 14 and regulatory approval of their proposed PDCs, the 15 NRC staff found this is acceptable to support design 16 and licensing process associated with X-Energys 17 design, subject to limitation applications stated in 18 the safety evaluation.
19 Well provide additional details in some 20 of the slides.
21 In our review of our X-Energys proposed 22 PDC started in July 2022 with the initial submittal of 23 their topical report, during the review of this 24 topical report the staff issued questions to X-Energy 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
59 and engaged in an RFI associated with this effort.
1 This resulted in greater understanding of 2
their proposed PDCs and X-Energy provider of the 3
topical report as a result of this engagement.
4 The NRC staff safety evaluation is based 5
on Revision 3 of X-Energys topical report that was 6
submitted on June 17, 2024.
7 Now Im going to turn it over to Ian Jung 8
who will cover the next slides.
9 MR. JUNG: My name is Ian Jung, Senior 10 Reliability and Risk Analyst. I have the honorable 11 position of technical lead, but I feel like its more 12 of a punishment.
13 (Laughter.)
14 MR. JUNG: So, with that, I can begin and 15 Ill cover these slides.
16 In addition to us, we have engaged other 17 staff members as necessary to get insights and inputs 18 in our evaluation.
19 So, as you know, 10 C.F.R. Parts 50 and 52 20 contains requirements on PDCs. It doesnt say, the 21 requirements doesnt say a lot but its simply 22 principal design criteria must be submitted for a 23 staff review and approval.
24 And just one note to 10 C.F.R. Part 50, 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 Appendix A on GDCs. It is not, its a requirement for 1
light-water reactors but it contains some important 2
information about the scope and content of PDCs. The 3
language there it says that PDCs establish necessary 4
design fabrication, construction,
- testing, and 5
performance requirement for SSCs important to safety.
6 And that is SSCs provide reasonable 7
assurance that the facility can be operated without 8
undue risk to health, to the health and safety of the 9
public.
10 So, the reason I highlight this portion is 11 that when you apply licensing modernization project at 12 NEI 18-04, theres a set of information, critical 13 elements of LMP needs to be executed that provides a 14 reason for us to obtain a finding. I think theres 15 some difference between light water reactor side and 16 the risk-informed (audio interference) side.
17 Its going to come up later when we, when 18 Im talking about the scope of the PDCs regarding 19 licensing basis events
- like, you
- know, 20 beyond-design-basis not being included in the PDCs for 21 X-Energy.
22 This conversation led to imposing 23 limitation on condition because under the LMP 24 beyond-design-basis is best if they show it to 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
61 important which leads to classification, appropriate 1
requirements and so on, which could lead to safety 2
significant
- SSCs, which may require potential 3
principal design criteria.
4 Based on the current design that X-Energy 5
has, they have not identified any risks significant 6
beyond-design-basis events and so on. So, we are 7
going with that. I think that we are still imposing 8
a limitation to condition. The rest of the LMP 9
process has to be executed as well as their design, 10 currently being preliminary, has to be finalized.
11 Next slide.
12 As was mentioned earlier by X-Energy, 13 several regulatory guides are very relevant to our 14 review. Reg Guide 1.23 -- 232 provides items on PDCs 15 for non-light water reactors, non-LWRs.
16 Reg Guide 1.233 provides guidance for 17 risk-informed and performance-based methodology to 18 inform the licensing basis and content of 19 classifications. It endorses NEI 18-04 with certain 20 clarifications.
21 Regularly Guide 1.253, which has been --
22 which was issued a few, a couple months ago, it 23 provides additional guidance on PDCs as its related to 24 PDCs when you implement the LMP. So, required 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 functional design criteria and so on, CDCs and so on, 1
those start showing up in NEI 21-07 document.
2 So, staff approved the NEI 21-07 with 3
additions and clarifications.
4 Next slide.
5 CHAIR MARTIN: Just real quick.
6 MR. JUNG: Yes.
7 CHAIR MARTIN: It was first amended two 8
years ago. And it was noted on your slide one or two 9
back. And, of course, now youre mentioned regulatory 10 guidance.
11 Two years seems kind of a long time for a 12 topical report like this. Is it because of all the 13 newness, you know, their approach to, I mean, you 14 know, opinion, questions from staff that kind of led 15 to keep it from the more traditional assumptions that 16 appeared in the Reg Guide 22-52?
17 But, nonetheless, this integration of new 18 and possible suitable, was that really what most of 19 your questions through the different revisions and 20 maybe required an extra iteration about the design 21 evolving fast enough to support where its influenced 22 the overall?
23 MR. JUNG: The answer is yes. Overall, we 24 found that the modular high-temperature test records 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
63 and criteria are very similar. So, we knew going in 1
that it wasnt going to be a huge challenge. Yet, 2
implementation of LMP led to additional conversations.
3 And the reason it took a little bit longer 4
is that, actually, X-Energy suggested for the staff to 5
perform an audit so that we, the staff, can see some 6
of the implementation documents of the LMP relevant to 7
PDC developed, required function of design criteria, 8
classification, and so on.
9 So, we benefitted a lot from that which 10 led to another several months of delay. Overall, the 11 review of this topical report has gone very smoothly.
12 Our conversation with X-Energy was very cordial and 13 very professional.
14 CHAIR MARTIN: Okay, thank you.
15 Who asked for an audit?
16 MR. JUNG: X-Energy volunteered and we 17 accepted.
18 So, X-Energy design, key design features, 19 Im not going to repeat it. Steve Vaughn at X-Energy 20 did it. And the report, MHTGR mostly, very similar 21 design. There are some differences, of course, but, 22 you know, the fuel design being, you know, prismatic, 23 fuel block versus pebble being one of those.
24 But, overall, theres no significant 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 design differences.
1 DR. BLEY: Excuse me. This is Dennis Bley.
2 Can you say a little more about the audit, 3
what kind of things you learned and maybe what 4
difficulties you might have had if you hadnt had the 5
chance for that audit?
6 MR. JUNG: So, theres an audit report 7
thats a part of our safety evaluation. And so, I was 8
reading through it. X-Energy made available several 9
LMP implementation documents. So, development of the 10 required safety functions, PRA safety functions, 11 similar documents. I can refer to it.
12 CHAIR MARTIN:
Safety classification 13 documents, like that?
14 MR. JUNG: Yes. Im just going to go, 15 theres five documents: preliminary SSC classification 16 list; special treatment of reactor protection system; 17 integrate decision-making process into implementation 18 guide; and the PRA Phase 1 event sequence analysis 19 document.
20 So, these are the documents that X-Energy 21 provided staff. Also was engaged in find which 22 documents might be useful for us.
23 And it led to a conversation that if some 24 of them led to actually modification to 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
65 report and later revisions of the topical report.
1 DR. BLEY: Okay. Thank you.
2 Im just wondering if some of these 3
documents they developed about how to implement NEI 4
18-04, if any of that suggested that there might be 5
more general guidance from the staff to other 6
applicants who might be following the general 7
approach?
8 MR. JUNG: I think my, my sort of 9
observation at the time on the subject has been into 10 X-Energys implementation of these, these documents 11 are still preliminary in nature. I think it might be 12 more beneficial to go through the process and then 13 bring back the lessons learned into, into more broadly 14 to other stakeholders.
15 DR. BLEY: Okay, thanks. Because that, 16 yeah, I think some of the guidance in 18-04, predicts 17 not the right word, but might be difficult for some 18 applicants to implement. And this may have given some 19 clarity on how to go through that process.
20 MR. JUNG: I think, personally, I fully 21 understand that. And at the same time X-Energy 22 implementing, for even X-Energy its very challenging 23 even now. We see that. And so I think all the 24 lessons learned were going to get.
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66 Of course, for the staff members we are 1
learning, using these Reg Guides we are learning a 2
lot of lessons. We are already applying lessons 3
learned on documentation of the NEI 18-04 into our 4
task.
5 So, those are being actually discussed 6
even among staff members on how to bring back the 7
lessons learned, and document that and bring back into 8
the potential revisions to future LMP guides and 9
guidance documents. Thats already being useful.
10 DR. BLEY: Okay, thank you.
11 CHAIR MARTIN: And Ill add, you know, I 12 started to write my letter, my draft letter. And 13 focusing mostly on what we talked about Xe-100 PDCs.
14 But there is for me a temptation to talk about this 15 generically.
16 And, you know, given that weve, you know, 17 seen a couple of PDCs, you know, come through, and, 18 you know, maybe after the third one we have a better 19 idea maybe how, how to report with that, how to 20 consider these sort of things.
21 And so, Im trying to decide in my head 22 whether I should add some content to my letter related 23 to the generic application of PDCs. Because I think, 24 you know, Im learning a lot. Sounds like you all 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 have learned a lot over the last two years about 1
implementing.
2 You know, the Reg Guide itself has been, 3
you know, was focused on non-light water reactors.
4 That just feeds right
- into, you
- know, the 5
technology-inclusive philosophy of the subsequent Reg 6
Guides.
7 Maybe one day we see a little tighter 8
coupling between, you know, those subsequent Reg 9
Guides and kind of revisit Reg Guide 232 in light of 10 what weve learned from multiple design center 11 meetings like this one.
12 But this one I think is, particularly 13 mostly because Im chair, the keeper, but I think 14 theres a lot to learn here, a lot of lessons learned, 15 I think. And certainly as you compile and were 16 compiling some ourselves, that I think that it might 17 lead to further improvements, process improvements 18 that we can do here.
19 Anyway, proceed.
20 MR. JUNG: Understood.
21 DR. SCHULTZ: This is Steve Schultz.
22 Let me ask it a little differently.
23 Youve spent a lot of time going through this portion 24 of the process. And Revision 3 as youve gone 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
68 this evaluation and your review, are you for X-Energy, 1
has it prepared both you and X-Energy, put you in a 2
position to move forward more rapidly because of the 3
time you spent here?
4 Do you have a better understanding of what 5
needs to be done in the next steps of the licensing?
6 I would hope the answer would be yes, but 7
if you could answer from your point of view on that 8
Id appreciate it. Thank you.
9 MR. JUNG: The answer is yes. Not just 10 because of this topical report. Because there are 11 several multiple topical reports that are currently 12 under review, and audits are ongoing on several of 13 those topical reports.
14 Overall, safety analysis there are four, 15 four topical reports that are currently under review 16 and audits ongoing.
Theres the training 17 qualification topical report, and graphite topical 18 reports are coming soon.
19 We are performing our audit, actually, 20 right now, pre-application readiness assessment on 21 that.
22 So, putting all these together it does 23 take a challenge. Its new and novel. But I think, 24 I think X-Energys working hard and we can see that.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
69 They have their own milestones. And staffs been 1
entertaining quite a bit of expense learning about the 2
design, learning about the LMP process.
3 So, ARCAP, advanced reactor content of 4
application and technology-inclusive content 5
application guidance finally issued a few months ago 6
with the endorsement from the committee. We are all 7
learning and implementing, I think its to some degree 8
having a construction, Part 50 construction permit 9
application process allows gradual process to go 10 further into the final design. And the operating 11 license application will be coming out.
12 So, feel comfortable where we are. But I 13 think theres a lot more to be done.
14 DR. SCHULTZ: Thanks for your perspective.
15 Thank you.
16 MR. JUNG: So, next slide.
17 So, just a recap. Overall, PDC the 18 approach for us is that based on the fact that these 19 are, these PDCs are based on Appendix Charlie of the 20 Reg Guide 1.232, substantially similar in design, 21 allows us to be a little more efficient. And theres 22 some modifications made to the Appendix Charlie based 23 on the X-Energy-specific design.
24 Also, PDCs are, X-Energy PDCs are also 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 based on LMP implementation, which was talked about.
1 Marriage of Reg Guide, deterministic Reg 2
Guide 1.232, a bit more risk-informed and performance 3
-based Reg Guide 1.233, is not yet, not a clear cut.
4 So, we struggled a little bit trying to marry those 5
things, two things together, and the terminologies and 6
so on.
7 And then new expressions of LMP require 8
safety functions, require safety function of the 9
criteria, PRA safety functions, and so on.
10 I think the staff wants me to hurry up.
11 MEMBER HALNON: This is Greg. Can I jump 12 in here real quick?
13 I just wanted to, on that previous slide 14 you mentioned it wasnt as clear as what you had 15 hoped. Are you guys keeping notes so that -- one of 16 my questions I was going to ask you all, if you were 17 happy with the guidance statutes through both 18 reviewing, and I should have asked the applicant about 19 developing the PDCs, are you all keeping notes and are 20 you planning on a future lessons learned type revision 21 of these, or maybe another Reg Guide that roadmaps you 22 for the right way to go, or the better way, more 23 efficient way of getting through this using LMP?
24 MR. JUNG: The answer is yes. It would 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
71 we have a contract with the Idaho National Lab whos 1
been supporting the development of many of this LMP 2
guidance.
3 So, one of the new task items is actually 4
collection of the lessons learned. And I think a 5
couple weeks ago there was a discussion of developing 6
a Excel spreadsheet where this information is 7
documented, lessons learned are documented and 8
questioned in the future.
9 Also, that lessons learned is somewhat 10 important from the perspective of Part 53 guidance 11 development because we, if possible, we want to 12 include those lessons learned into the Part 53 13 guidance documents that has to be developed based on 14 the past.
15 Some of those guidance under Part 53 is 16 going to be also based on the LMP guidance we do have 17 right now under Part 50 and 52.
18 MEMBER HALNON: Okay. Thats excellent.
19 Thank you.
20 And perhaps when we get into the Part 53 21 interactions we can walk through some of the lessons 22 learned that youre capturing to see how it might make 23 things more efficient down the road.
24 But Im glad youve got that task going 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 on. Thank you.
1 CHAIR MARTIN: A follow-up to Gregs 2
question. You mentioned an Excel spreadsheet. Will 3
there be a document, public domain document kind of 4
capturing your work with the lab, work with DOE? I 5
would think that --
6 MR. JUNG: I know its internal. At some 7
point those lessons learned will probably need to 8
circle back with industry.
9 CHAIR MARTIN: Sure. It will go public at 10 that point.
11 MR. JUNG: Exactly.
12 CHAIR MARTIN: Okay.
13 MR. JUNG: Yeah. Even during that meeting, 14 interactions with X-Energy, X-Energy already has 15 expressed some of the lessons learned and some of the, 16 actually, improvements that can be made to NEI 18-04 17 and so on. Its already showing up.
18 CHAIR MARTIN: Okay.
19 MR. JUNG: So, Ill be very quick. So, the 20 key differences are discussed here.
21 Overall, the significance of these items 22 are not super complex. And I would say Ive seen 23 enough to emphasize some of these areas in our safety 24 evaluation. So, these are some of the areas that we 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
73 focused on.
1 So, Im going to, just like X-Energy did, 2
Im going to go through some of the examples of these 3
areas.
4 Next slide.
5 So, to my knowledge, X-Energy is proposing 6
to replace important safety with safety significant.
7 And the safety significant, the terminology is well 8
defined in NEI 18-04, a lot more clearly than 9
traditional important to safety definition.
10 So, the reason I think that terminology is 11 very important to be part of these PDCs is that under 12 the LMP your terminologies and definitions and so on 13 are quite different in some of the areas. So, even 14 Reg Guide 1.233 talks about if you are following an 15 LMP you are, you know, it is expected that terminology 16 under LMPs is supposed to be used.
17 So, I think X-Energy is being consistent 18 with that.
19 So, I think overall, overall, you know, 20 there are some areas that in LMP safety significance 21 you can access these being safety-related and NSRST 22 SSCs, and also LMPs, its a score of these focuses on 23 normal operations, AOOs, and design basis events, 24
- DBEs, and design basis
- accident, 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
74 beyond-design-basis events.
1 But there was a notion that, that in NEI 2
21-07, as well as ARCAP roadmap I have a sheet on the 3
screen, talked about there may be cases where 4
important to safety SSCs may not be fully captured in 5
safety significant SSCs under the NEI 18-04.
6 So, finally, follow the Reg Guide 1.232 7
that brings some of these concerns to use, because 8
when you -- if you look at the Reg Guide 1.232, 9
Appendix Charlie, as well as X-Energy PDCs, it 10 addresses some of the PDC 60. I think, for example, 11 it talks about normal radiological releases, like gas 12 and that. Also, fuel handling and fuel storage 13 systems are discussed.
14 And, also, some of the normal operations 15 that was discussed by X-Energy, normal operation is 16 also included in the Reg Guide. So, I think that we 17 felt that there is no gap.
18 Next slide.
19 Yeah, I briefly touched on this on the 20 scope of the LBEs. And, so, X-Energy replaces the 21 terms in Reg Guide 1.232, such as postulate accident 22 and accident conditions with a terminology used in the 23 LMP. Postulated accidents and accident conditions, 24 those terminology has a certain meaning in the light 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 water reactor space.
1 Also, those are not used in LMP. So, I 2
think its good to translate those terminologies into 3
LMP language.
4 One other area that we looked at was how 5
come theres no beyond-design-basis events discussed 6
here? Because under the LMP beyond-design-basis 7
events are one of the LBE categories which may 8
contribute to risk-significant or defense-in-depth 9
functions, as well as, as well as it can lead to a 10 safety-significant SSC, for example.
11 So, based on the current design, X-Energy 12 indicated that they have not seen any significant, 13 risk-significant SSC for the beyond-design-basis 14 events. And so, one, and also there it is one of 15 those marriages between Reg Guide 1.232 and 1.233.
16 They are generally equating these 17 postulated accidents and accident conditions to AOOs 18 and DBEs and DBAs. Yet, we, the staff did not really 19 have full confidence in that. All the current 20 preliminary design and current implementation of LMP 21 may lack the full benefit of LMP process: PRA, 22 defense-in-depth evaluation, and so on.
23 We felt that there is room that there 24 possibility of beyond-design-basis events showing up 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 to be potentially risk significant, for example.
1 And, also, if you look at the LMP process 2
and turn to some of the external hazards, or certain 3
sites may with the external hazard characteristics, if 4
these PDCs are applied you may also have some 5
challenges.
6 So, we felt that I think its good to 7
impose the limitation of application based on 8
preliminary design and preliminary implementation of 9
the LMP. Future applicants may find these PDCs 10 applying to their design by verifying that their LMP 11 notification confirms this. Thats the limitation 12 provision (audio interference.)
13 CHAIR MARTIN: I know from historical 14 context the GDCs design basis as, well, almost 60 15 years ago werent as sensitive to beyond-design-basis 16 events as we are today.
17 But I do agree that the language in NEI 18 18-04, you know, when you acknowledge that certainties 19 associated with liability always in frequency of 20 events you are looking, you will look at events that 21 are considered beyond design basis.
22 I guess as I was reviewing the material, 23 reconciling the maybe lack of, you know, specific 24 mention of beyond-design-basis in the proposed PDCs, 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 the fact that theyre going to do it anyway. I mean, 1
thats if youre, if youre following LMP in a 2
rigorous manner you will be, you know, considering 3
the, you know, safety significance of the SSCs in all 4
these contexts.
5 So, it is currently there. And indication 6
of LMP may be considered a little more restrictive 7
than the tradition of GDCs for light water reactors.
8 It comes down to whether the language appears there or 9
not.
10 Now, what we dont have is, like, the 11 flip-end events, and thats a little bit beyond, well, 12 you know, beyond 5 times 10 to the minus 7th, in that 13 space. So, that effect remains excluded even under, 14 you know, inevitable marriage of the Reg Guide with 15 NEI 18-04.
16 But I do think its covered elsewhere in 17 the NRC safety framework documents.
18 MR. JUNG: Yeah. And I fully agree. And 19 its sort of in the nature of where we are in the 20 whole process. And, also, if we did have the complete 21 design, final design, there might be a lot better 22 clarity on some of these things.
23 But, historically, equating postulated 24 accidents and so on are traditional DBAs. But 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
78 historical also its these GDCs and so on came around 1
19 late 60s and early 70s. Maybe before my time, but 2
I was told.
3 But as we learned many lessons learned 4
since
- then, that two additional regulatory 5
requirements on what we call beyond-design-basis 6
accidents. It could be debated depending on the 7
frequency and consequence, sure this could have been, 8
you know, beyond-design-basis events or just been 9
DBEs. But at the time the decision was more a 10 traditional framework.
11 So, it could be a long story there. But 12 I think that we are covered clearly for ARDP as well 13 as commitment for X-Energy to follow the LMP, provide 14 the assurance to help continue to PRA, and theyll 15 still go through and make sure what can go wrong, you 16 know, comprehensive evaluation of what could go wrong 17 is evaluated for PRA standard requirements as well as 18 LMP implementation through integrated decision making 19 panel process that will be subject to future NRC 20 review.
21 CHAIR MARTIN:
Till we get more 22 information, particularly on the LBEs and first 23 response, do you have that LC, limitation condition, 24 associated with this TR.
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79 MR. JUNG: Yes.
1 Next slide.
2 MEMBER ROBERTS: The applicant talked about 3
how making qualitative and quantitative factors will 4
figure out the beyond-design-basis events, what parts 5
of the system need to be credited or what parts of the 6
system are, you know, dismantled for PRA modeling.
7 For the containment part specifically they 8
took out the words about multiple barriers. And so, 9
what they defined is a system that they think had 10 multiple barriers from a standpoint of specifically 11 what they put in as opposed to the generic, you know, 12 have multiple barriers.
13 The committee six years ago wrote a letter 14 on functional containment where one of the 15 recommendations was to always have multiple barriers 16 in functional containment systems. And Im just 17 wondering if that gets lost taking the words out of 18 the PDC? Or is your expectation that the subsequent 19 evaluation will ensure theres multiple barriers 20 because thats just what the PRA and the judgement 21 will produce, something thats needed?
22 Just wondering what your thoughts are on 23 that? Because maybe not the words, multiple barriers 24 just means that, you know, the conclusion was what 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
80 they specify doesnt contemplate multiple barriers 1
beside beyond-design-basis event, you know, what hope 2
do you have to get multiple barriers?
3 MR. JUNG: Member Roberts, can I, can I 4
speak, respond to that by the time we get to the 5
functional containment slides?
6 MEMBER ROBERTS: Sure.
7 MR. JUNG: So, staff also looked at the 8
area of normal operations and the use of 9
owner-controlled design criteria. X-Energy went 10 through owner-controlled design criteria pretty well.
11 The reason that we got established looked 12 at the normal operations is its partly because LMP 13 scope does not include, NEI 18-04 scope does not 14 include the normal operations.
15 So, there was a notion, and NEI 21-07, as 16 well as NRC staff guidance that talks about there may 17 be cases where safety-significant SSCs may not equate 18 to important to safety, that I discussed earlier. So, 19 we looked at the area that was kind of, we thought 20 that was important to consider some normal operation 21 aspects of that.
22 So, X-Energy includes those normal 23 operations, normal operations were at normal 24 conditions these PDCs, some of them are related to the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
81 OCDCs in particular SSCs is not performing -- is 1
performing non-safety related functions.
2 But, also, as I mentioned earlier, 3
X-Energy PDCs 60 through 64 discussed some of the 4
normal operational releases, gas, liquid, and solid 5
waste, and then also fuel storage and handling, design 6
criteria in 61 through 64 and so on. So, those are 7
captured.
8 So, overall, we felt that the overall 9
action of PDCs covered this area.
10 And then the use of OCDCs, although they 11 may not be the design basis of the plant, but it 12 clearly provides a clarity in terms of separation 13 between safety-significant SSC design criteria versus 14 those that are not. Or as we discussed earlier, the 15 PRA models, all these SSCs.
16 So, I think its all being handled and 17 having this distinction is useful for this.
18 Next slide.
19 So, replacement of single failure 20 criterion with the reliability criterion was discussed 21 by X-Energy. We felt that this is consistent with the 22 staff guidance in Reg Guide 1.233.
23 The concept was approved by the Commission 24 earlier.
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
82 In NEI 18-04 we also recognized that, that 1
safety-significant SSCs would be, would have a 2
reliability target and capability targets as well.
3 And then also defense-in-depth evaluation is needed 4
for us during the assessment of the event sequences.
5 So, we felt that this replacing --
6 replacement is not lost.
7 But we also recognized that single failure 8
criteria is in some cases good industry practice. So, 9
I took the 603 for I&C, for example, gets us the 10 criterion. Some of the active systems have to be able 11 to establish the redundancy and overall reliability 12 redundancy. And we found that diversity play a 13 critical role, in doing so apply a single basis 14 criterion is a good practice, theoretical practice.
15 CHAIR MARTIN: If they had kind of kept an 16 either/or kind of statement, single basis criteria for 17 reliability, would it materially change anything to 18 the PDC?
19 You know, my experience is doing safety 20 analysis for, you know, for other projects, I mean 21 having to address the reliability or, you know, 22 pinpoint design inputs in the decision-making process, 23 it counts; right? And were dealing with new plants.
24 Now, when you get down to, you know, some 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
83 very specific parts, well, then maybe there are, there 1
is data that supports, you know, the design inputs for 2
PRA. Maybe not. Maybe theres some novelty 3
associated with designs both TRL, technology readiness 4
level, to SSC, that really are hard to pinpoint in 5
reliability.
6 And as a practitioner in the single 7
failure
- criteria, while oftentimes terribly 8
conservative, versus why it was introduced 60, 70 9
years ago could be valuable and really help with the 10 regulatory engagement. It has had a long history and 11 a very successful history.
12 I perceive a possibility that, you know, 13 when you were starting to -- I know youve audited, 14 you know, the PRA, you know, this early PRA. But, 15 maybe not to the degree that you will down the road.
16 You know, might you find maybe a need to revisit this 17 one should you not be able to really make a conclusion 18 on some reliability numbers for maybe some, oh, TRL 19 aspect of the design.
20 So, that was kind of two questions. You 21 know, the first simple one, would it, you know, be 22 included just in your statement whether that would 23 have any problem with that? Or and then second, a 24 what if kind of question.
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84 MR. MUNIZ: Personally, I think, I think it 1
may not hurt to use the or. That gives them more 2
flexibility. So, I dont think theres an issue with 3
that.
4 But I think to me its more at a function 5
level. I think if we look at the term reliability it 6
brings a lot. I think it captures the intent of why 7
certain design techniques would show up.
8 So, during the LMP implementation when you 9
set reliability terms, and capability terms, and 10 defense-in-depth, and all that, and as you classified 11 SSCs, at the time you start helping define what are 12 special treatments you want to identify about, it 13 leads to codes and standards, depending on the 14 significance of the functions these SSCs are 15 performing, Im not surprised that you get to stand, 16 stand up to frame specific techniques. That helps use 17 of failure criterion or something.
18 So, personally, Id rather leave that 19 choice to the designers rather than putting a single 20 failure criterion up front may actually be too narrow, 21 too
- specific, which may lead to potentially 22 unnecessary conservatism that we wanted to avoid. So, 23 thats my thought.
24 CHAIR MARTIN: I do think, along 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
85 opinions, the process, maybe its August, applies more 1
on the PRAs. And it suggests that the quality of PRAs 2
are going to be higher than when it agrees with the 3
Part 52. Of course, thats pretty high standard 4
already.
5 But, you know, the operating plant, 40, 50 6
plus years of experience, you know, the qualities are 7
very, very high. The plants that are still on paper, 8
you know, theres a question mark there. And, of 9
course, LMP accommodates that. But I think from a 10 practitioners standpoint it actually might be hard to 11 implement. You might want to have the or statement 12 in there to, you know, solve certain problems.
13 But I do think scrutiny on PRAs would be 14 a little bit higher. Im sure the staff here is 15 sensitive to that.
16 But to the extent that criterion is a way 17 out, you know, and can be sticky areas, again, more to 18 the benefit of the applicant but certainly from the 19 engagement with the staff.
20 I saw Dennis. Dennis hand. Go ahead, 21 Dennis.
22 DR. BLEY: I did put it up because this is 23 a thing Ive worried about for a long time.
24 But the truth is, unless youve got 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
86 really lousy PRA, if a single failure is significant 1
in its impact it will surface very clearly in the PRA.
2 And, separately, speaking of it being 3
conservative, well, not quite. There are quite a 4
number of double or even higher order failures that 5
can be more likely than a particular single failure.
6 So, its not always giving you what youre hoping for.
7 Back when it was formulated we didnt know 8
how to do the reliability approach thoroughly, so it 9
was kind of a cover to make sure we had enough 10 redundancy to at least have some protection. But I 11 dont see the value in it today.
12 CHAIR MARTIN: Okay. We all have opinions.
13 So, thanks, Dennis. Perfectly fine that 14 way. But I do appreciate, obviously, being given the 15 details of PRAs. You know, theres a lot of insights 16 that come from that.
17 My principal concern is the uncertainties 18 associated with those design inputs, particularly for 19 a
plant that has never been built.
Those 20 uncertainties are, you know, going to be and pretty, 21 pretty challenging I think for everyone.
22 But, Tom, you look like you have a 23 question.
24 MEMBER ROBERTS: Yeah. I just wanted 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
87 follow up on what Dennis just said.
1 I think you made an important point, which 2
is that for some designs, specifically I&C as an 3
example, there are decades, you know, of experience 4
with designing a single failure criterion as one of 5
the inputs. And throwing that out would have a whole 6
lot more baggage that you would have to figure out, 7
okay, how do I get the equivalent of that in terms of 8
my reliability assessment?
9 And so, at least for some areas, just 10 keeping a
digital alternative single failure 11 criterion, at least the applicant level, not 12 necessarily at the safety analysis or the NRC staff 13 level, it might be important just to ensure that the 14 reliability analysis thats needed by the -- if, you 15 know, the approach is sufficient.
16 So, I dont know if you want to comment on 17 that. But thats what I understood you to say.
18 MR. MUNIZ: I think this is a conversation 19 we are having with an applicant and also internally.
20 I still believe that whether a single 21 failure criterion exists or not, the applicants are 22 right now accident significant and the PRAs speak 23 about it. They understand uncertainties. They have 24 a challenge of addressing potentially areas, so less 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
88 expense, less data, and so on.
1 But I think, personally, I do believe that 2
LMP is designed to deal with that. And thats why 3
theres a
difference in that element.
4 Defense-in-depth, one of the main purposes is to deal 5
with uncertainties.
6 DR. BLEY: This is Dennis again.
7 I agree with Tom here, especially when you 8
start looking at digital I&C, which is an area where 9
we havent got especially the reliability models these 10 days. So, you need some alternative to protect you 11 there.
12 I think in most of the places where were, 13 you know, talking pumps, valves, that kind of stuff, 14 theres plenty of pages for the other opinion.
15 MR. MUNIZ: I think we all are recognizing 16 that same challenge. I think there are going to be 17 some areas with passive system failure modes or 18 digital system reliability for common failures and 19 things like that.
20 So, what Im trying to get at is that 21 there are requirements and expectations that present 22 that, as well as uncertainty being considered as part 23 of the integrated system making process as well. And 24 then PRA, even TR review process we endorse will have 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
89 a tremendous requirement there and responsibility to 1
address how you are you addressing the uncertainties, 2
lack of operating experience. Which may lead to some 3
of this decision point.
4 This is important, if applicant or 5
designer choose to, Im going to say, hey, weve done 6
this code always for the reactor protection system, 7
actually 603s, apply that. Give it to the vendor and 8
generate it.
9 That can be one of the options. But still 10 theres going to be some question. Do you want to 11 follow single failure criterion and then still have a 12 challenge here, like you have some of the sequences, 13 I&C system is involved, wed like to understand always 14 the PRA model. What PRA model in terms of frequency 15 of consequences?
16 So, I just want to share that. The 17 provisions are there. But at this point I want to 18 give X-Energy to have an opportunity to decide on what 19 brings the reliability in sufficient quantity, in 20 their own choice.
21 CHAIR MARTIN: Certainly appreciate that.
22 I think one of my points is that we have 23 kind of two approaches for some decisions, you know, 24 even at a low level design process. And thats a good 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
90 thing.
1 You know, weve been living off single 2
failure criteria for a very long time. And its been 3
very successful. And now we have elevated the role of 4
risk in our decision making and development of safety 5
cases. Now we have kind of a different approach.
6 They can complement each other. They can use them to 7
verify each other, you know, should you need that, you 8
know, level of rigor.
9 My only, you know, concern might be that, 10 you know, we start moving past what has been 11 successful, you know, up to 2024, and not recognize 12 that benefit and try to go into the other, other 13 direction.
14 Right tool or the, the right problem, you 15 know. And thats what, you know, this language, you 16 know, maybe just take the PDCs offering. You cut one 17 out, well, maybe youre really, you know, cutting off 18 your arm, you know. Because there may be situations, 19 weve heard an example or two that, you know, you may 20 want to go the other direction.
21 I just want to comment real quick. Walt, 22 I did notice just briefly your hand went up and then 23 went down. Did you want to say something?
24 MEMBER KIRCHNER: Well, I would have 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
91 concurred with Dennis. One would hope that a good PRA 1
would flesh out very early on single points of failure 2
in terms of impacting the overall robustness of the 3
design.
4 I would observe, though, that applying 5
single failure criteria to the defense-in-depth audit 6
may be a useful way just to test the completeness.
7 I felt that early in the LMP process the 8
defense-in-depth exercise was the least well 9
fleshed-out aspect of the NEI 18-04 and LMP. And 10 certainly for a simple desktop audit of the 11 defense-in-depth exercise, looking at single failures 12 and, one would hope, as Dennis observed, those would 13 have been identified very early on, but it is a way, 14 Bob, to test out whether to have a robust design for 15 the particular system in question.
16 Thats all I wanted to add.
17 CHAIR MARTIN: Well, thanks, Walt. That 18 kind of accentuates my point there that theres value 19 for verification testing.
20 All right, thanks. Go ahead.
21 MR. JUNG: Next slide.
22 PDC 16 uses, the language and Reg Guide 23 1.232 made certain changes. So, it came up at the 24 X-Energy presentation, they are dividing the PDC into 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
92 two, on RFDC 16 and CBC 16, and consistent with the 1
NEI 18-04 and Reg Guide NEI 21-07.
2 So, for DBEs and DBAs, these are multiple, 3
right, the barriers and fuel particles.
4 That is, essentially, X-Energy is relying 5
on these fuel particles and pebbles, their main three 6
layers there as multiple barriers or as a function for 7
CDC in the area for helium bound before AOOs.
8 And then next bullet has theyre placing 9
design conditions within importance to the design 10 limits. A little bit more clear, more clear that 11 design limit is established.
12 And so, overall they feel that the 13 function of containment is approved by the Commission 14 a few years ago. And the intent of the MHTGR 16 is 15 met.
16 So, with that, you know, remember Robert 17 asked me about the question of what do you think about 18 the, you know, multi-layer approach? I, to me I still 19 go back to the LMP process. So, theres a functional 20 requirements that are placed or functional 21 categorization, requires safety functions and PRA 22 safety functions, and so on.
23 So, for more significant elements are 24 related --
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
93 CHAIR MARTIN: Please mute.
1 MR. JUNG: So, from an overall LMP 2
perspective we feel that even the intent is, I think 3
the intent of the Reg Guide is met. Theres no 4
question about the fuel failure, fuel particles.
5 For helium coolant boundary aspects of the 6
layer, if I remember correctly, even in Reg Guide 7
1.232 theres a, theres a table that showed what was 8
in the GDC and what was what the staff resolution is.
9 Even the staff at the time had some discussions on it.
10 And, actually, they had a discussion and it could be 11 a layer or more.
12 So, there is a little datapoint for that.
13 But I think, you know, also X-Energy has 14 indicated that there are other SSCs, right, you know, 15 in the actual building and so on. X-Energy has 16 determined that this is sufficient criteria to meet 17 the functional requirements that they identified.
18 If they needed additional layers for 19 defense-in-depth perspective, it would have shown up.
20 Thats what we saw.
21 So, we felt this is reasonable approach.
22 Yet, the whole process to still go 23 through. Thats why theres the imposition of the 24 limitation in condition, it has to be still 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
94 demonstrated.
1 CHAIR MARTIN: Okay. Walt, I see your 2
hands up.
3 MEMBER KIRCHNER: Yes, thank you.
4 This is an area where it's more for the 5
staff, than the applicant. I see what the applicant 6
is doing here.
7 But my assessment is that this definition 8
actually dilutes what the Reg Guide provides for, and 9
let me explain.
10 The Reg Guide takes a much more expansive 11 view of what functional containment means by basically 12 stating multiple barriers, internal or external to the 13 reactor and its cooling system, shall be provided to 14 control the release of reactivity to the environment, 15 and ensure that functional containment design 16 conditions important to safety are not exceeded for as 17 long as the postulated accident conditions require.
18
- Now, postulated accident conditions 19 earlier was redefined as licensing bases events.
20 This is not, this is a rather narrow, more 21 narrow interpretation in my opinion, of what is in the 22 Reg Guide under functional containment, PDC 16.
23 And, my concern is that it's the 24 Commission policy that multiple barriers to form 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
95 robust containment system, to prevent unmitigated 1
radionuclide release is the intent here of this.
2 And, that's why I asked the question about 3
the (audio interference), and whether that was going 4
to be credited or not, as one of those barriers 5
earlier.
6 I just think in this case, I know it's 7
been tailored by the applicant for their particular 8
analysis based on going through the entire NEI 18-04 9
cycle.
10 But it leaves the perception perhaps to 11 the public, that this isn't quite the robust multiple 12 barrier system that the Commission and Agency had in 13 mind, when they drafted the Reg Guide.
14 So, that's a
personal opinion and 15 observation. It's a problem, we've seen this with 16 other applications as well, particularly on this 17 particular PDC.
18 And, my sense, how an applicant implements 19 it is a lower level thing. But retaining that basic 20 philosophy that the Commission laid out, is important.
21 And so sometimes just an observation, this 22 multiple, this dissecting of the PDC and the ascribing 23 in this case, the helium pressure boundary only for 24 AOOs, well, you need it during normal operation anyway 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
96 because you depend on the purity of the helium to 1
protect the pebbles, and the particle fuel.
2 So, it's a little bit, I know that's 3
addressed also in an earlier PDC in 15 about, I think 4
it's number 15, about unmitigated moisture control on 5
access in particular, is a concern for an MHTGR using 6
a steam Rankine cycle.
7 But when these PDCs get parsed like this, 8
I wonder whether they're losing the overall intent 9
that was initially determined in the Reg Guide.
10 So, any observation from the staff would 11 be welcome. But I've seen this in a number of the 12 PDCs.
13 They were getting into actual specific 14 design detail, rather than having an overlying, or 15 overarching is the better word, PDC for the particular 16 safety function that's in question.
17 MR. JUNG: Member Kirchner, I appreciate 18 your thought and it brings up your insights, something 19 to think further.
20 But I think at least my logic and the 21 review is that my trust in the (audio interference) 22 process, right?
23 You mentioned, there was mentioning about 24 Section 5 of the NEI in 04, which has a extensive 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
97 discussion of the defense-in-depth adequacy 1
evaluation.
2 And, there's a certain criteria that comes 3
along. For example, no single features, or no single 4
element is relied upon in demonstrating 5
defense-in-depth adequacy.
6 So I'm not sure exactly how this 7
particular AOO sequence may satisfy that element.
8 And also, if you look at the reason there 9
are steps in a kind of little bit challenging 10 situation, is the lack of the helium permutation 11 itself.
12 If you look at the construction permit 13 stage defense-in-depth evaluation, the NEI 21-07 talks 14 about because of the preliminary nature of the design, 15 and the lack of a programmatic elements, then that's 16 going to come down the road.
17 It focuses more on plant capability 18 defense-in-depth, not based on a programmatic element 19 that will come along, as well.
20 So, that limits also the scope of the 21 defense-in-depth to be plant capability, based on the 22 preliminary design.
23 So, NEI 04 allows the consideration of 24 both, at the end, both capability as well as 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
98 programmatic elements in demonstrating overall 1
defense-in-depth.
2 I just want to mention that to kind of 3
express my trust in the process that's undergoing.
4 But I think it's more at the end is the language of 5
multi-layer.
6 I do worry about a little bit, having the 7
language imposed on the designers at this juncture, 8
may potentially impose a unnecessary conservatism that 9
may, that may actually negate the potential benefit of 10 a LMP permutation.
11 CHAIR MARTIN: We've spent a lot of time 12 talking about this.
13 MEMBER ROBERTS: Yes, I was going to make 14 the exact same comment as Walt. But one thing I might 15 add is if the ACRS reviewed the functional containment 16 approach back in 2018, the recommendation, Ill just 17 read it verbatim.
18 The functional containment should contain 19 multiple barriers as defense-in-depth features that 20 should be minimally dependent upon each other, and 21 adverse of nature.
22 And per the ideals in the letter, that was 23 because of a concern that containment is more 24 important, ultimately the safety, than probably any 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
99 other feature.
1 And so, the idea of thinking you're smart 2
enough to rely on one barrier as sufficient, is cause 3
to concern to the committee 6 years ago.
4 I just wanted to make sure you're aware of 5
that, that precedent.
6 MR. JUNG: Yes, and another challenge is 7
the unique nature of these fuel pebbles, and fuel 8
particles.
9 Again, can we say on the language of are 10 they really independent, how that in a same, same, 11 under the same pebble things like that.
12 And, but there's an even interpretation of 13 a LBE sub right, if you want a really original intent 14 of the functional containment.
15 Is it really related to design basis 16 accident in a traditional sense. It's really the 17 original containment design is based on DVAs.
18 And so, we are in this somewhat unique 19 situation with the AOOs where we don't expect the fuel 20 to exceed the subtle temperature, things that we count 21 upon, there's going to limitation for that.
22 So, it appears that where DVEs and DVAs, 23 which is a significant, potentially more significant 24 consequential event, event sequences, if we equate 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
100 those events, I think the multiple barriers are really 1
articulated in here.
2 Even without multi, but barriers of 3
plural. So, I see that.
4 CHAIR MARTIN: Well, certainly we have 5
between the required functional design criteria and 6
the complementary design criteria, there are certain 7
barriers (audio interference) that are acknowledged 8
whereas the corpus of the Reg Guide just has the one 9
kind of statement.
10 Because obviously in this discussion kind 11 of falls back to kind of the historic discussion that 12 led up to the Reg Guide, about containment versus 13 confinement for high temperature gas reactors.
14 And, the Reg Guide is clear that TRISO is 15 kind of a key assumption in the preparation of these 16 PDCs.
17 But it's certainly something to keep on 18 considering, particularly and I'll bring up another 19 point.
20 They have a proprietary TRISO, the 21 TRISO-X. We're all familiar with EPRI's, I just call 22 it the TRISO topical, but obviously the staff reviewed 23 that in 2023 timeframe.
24 And, obviously came to a pretty strong 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
101 conclusion about the particular TRISO that was tested 1
out in Idaho.
2 But they had something a little different 3
and I know you have reviewed the fuel qualification 4
topical, and have some L&Cs associated with that.
5 But all that kind of plays into the 6
functional containment story. And, at least I had a 7
question and I got some help, when I was reviewing, 8
got some help from Derek Widmayer.
9 Because he's federal officer for this 10 organization, or staff was supporting and he pulled up 11 that topical and it answered a number of questions 12 kind of related to what commitments that you already 13 have with X-Energy supporting this obviously very key 14 barrier.
15 Or maybe another word, tri-structural that 16 implies multiple barriers, obviously at the kernel, 17 around the kernel.
18 So, I do think given that little bit of 19 history, it really supports my own personal comfort 20 level with the functional containment story that you 21 already have reviewed some of this.
22 Have L&Cs already kind of on record about 23 where they need to go ultimately with demonstrating 24 the fuel performance.
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102 So, given how much time we've spent on 1
this, I didn't, I wanted to give you the same question 2
I had for X-Energy on this one related to SARRDLs 3
versus functional containment, but I'm going to let 4
that one go.
5 Believe it or not, I think we're getting 6
more and more on time. So, why don't we go ahead and 7
proceed to the next one.
8 DR. SCHULTZ: I've got one more comment.
9 CHAIR MARTIN: Okay.
10 DR. SCHULTZ: One more comment.
11 In the safety evaluation, you indicate 12 that the required functional design criteria and the 13 complimentary design criteria, they have been accepted 14 by the staff.
15 But then you also remark that with regard 16 to the specific functional containment design limits, 17 those have not yet been reviewed.
18 And, I think you had just indicated that 19 the limitation in condition 1 may cover that, but I 20 didn't really see that being applicable to your 21 statement in the SE, and thought that perhaps 22 expanding that limitation and condition would be 23 appropriate.
24 MR. JUNG: I think the way we added that 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
103 just more of a expectation. So, just like any other 1
PDC, like even PDC 2, environmental qualification type 2
of things.
3 DR. SCHULTZ: Everything would --
4 (Simultaneous speaking.)
5 MR. JUNG: Everything --
6 DR. SCHULTZ: -- sort of get to that same 7
category in terms of what needs to be done, given the 8
more detailed design information?
9 MR. JUNG: Yes, it didn't have to get the 10 NRC, but I think it's just the emphasizing that that 11 work -- demonstration of conformance to the PDC design 12 our staff to carry through by having the design limits 13 established, which will be subject to NRC's review 14 perhaps during the construction permit application.
15 DR. SCHULTZ: As well as any other changes 16 that may affect the design criteria, as well?
17 MR. JUNG: Right.
18 DR. SCHULTZ: Thank you.
19 MR. JUNG: Next item is PDC 6, which was 20 discussed earlier by X-Energy, as well. It combines, 21 you're proposing a one single criterion for this area.
22 We felt that it's actually a better idea.
23 I think as you know, the LMP brand new 24 design, it's a clean sheet approach on things. So, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
104 identifying this one criteria that covers broadly to 1
all safety significant access, is a great idea.
2 Actually, it simplifies not limiting, but, 3
not limiting just particular systems but having a 4
design criterion that applies to all safety 5
significant assets. We felt it was a (audio 6
interference).
7 So, PDC 11, Dan, can you cover that? Dan 8
wasn't really feeling well earlier, so.
9 MR. BEACON: It's been a rough morning.
10 MR. MOORE: Could we take a short break?
11 This is Scott Moore, from ACS. Could we take a short 12 break for about 5 minutes?
13 CHAIR MARTIN: Oh, if we need a break, 14 let's go ahead and do it. I mean, 5 minutes, let's 15 get back at 11:20.
16 (Whereupon, the above-entitled matter went 17 off the record at 11:14 a.m. and resumed at 11:21 18 a.m.)
19 CHAIR MARTIN: Okay, so we were moving on 20 to PDC 11. You may proceed.
21 MR. MUÑIZ: Dan Beacon is not feeling 100 22 percent, so I'm going to take a shot. But Dan's still 23 here; he might try to answer some of the questions.
24 So, PDC 11 on reactor inherent protection, 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
105 TRISO fuel plays a significant role there. X-Energy 1
exposed its plan this morning so I don't want to 2
belabor this.
3 And, PDC 11 both captures MHRDC 11 and 12, 4
and also inherent protection of the TRISO fuel is one 5
of the two means that's discussed in PDC 26.
6 It's a unique design in the sense that 7
instead of two active means, there's one inherent 8
protection along with the record, the trip system that 9
poison and to come along down the road.
10 There is a, we put a little one limitation 11 condition regarding the expression of the indoor power 12 range, power operating range, where the staff because 13 of the design stages we are in, as well as the LMP 14 permutation, there might be a possibility beyond the 15 power range there might be some potential oscillations 16 and other issues.
17 So, we are proposing a limitation on that.
18 That the designers and applicant's referencing that 19 would verify that there's no such issues in other 20 ranges.
21 CHAIR MARTIN: Okay, that power oscillation 22 was actually was it 12 or, right? Oh no, you didn't 23 have it because it probably that's kind of all goes 24 together with it.
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106 But I believe there is a separate PDC 1
specifically about power operation. But, or excuse 2
me, power oscillation. Obviously it plays into what 3
you're saying here about the totality of the power 4
operation range.
5 Okay, so just wanted, if anybody was 6
looking at the topical, you might want to look at 7
also, I think it's 12.
8 MR. MUÑIZ: Appreciate it.
9 So, limitation 2, yes, as Dr. Martin 10 mentioned, it has relationship to the MHTGR-DC 12.
11 Next.
12 CHAIR MARTIN: So, they say subsumed by PDC 13
- 11. Okay, so they integrate the two.
14 MR. MUÑIZ: Right.
15 CHAIR MARTIN: Okay, I guess my bad. I 16 mean, obviously the 12, 12 has always been there in 17 Reg Guide, but that's what they did kind of the same 18 way they used PDC 6 and just propagated its role.
19 MR. MUÑIZ: Yes, so PDC 11 captures both 11 20 and 12.
21 CHAIR MARTIN: I see.
22 MR. MUÑIZ: PDC 14 reactor helium pressure 23 boundary, and testing considerations are removed and 24 integrity part is captured by PDC 70.
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107 If you look at the PDC 70, it talks about 1
the integrity of the reactor helium pressure boundary.
2 PDC 6 as discussed earlier, it covers all testing 3
provisions for all the safety significant assets is 4
covered.
5 There is a, I'm trying to read through it.
6 Yes, what I was going to mention is that is ingress of 7
moisture, air, and secondary coolant to other fluid is 8
replaced with a moisture ingress, based on current 9
their design.
10 But I think staff is proposing the 11 limitation and condition that needs to be verified, 12 depending on the LMP implementation and the design.
13 We just couldn't see without the detailed 14 design, whether the moisture ingress simplification is 15 sufficient or not.
16 So, we are imposing a limitation of that.
17 MR. METZROTH: And, does this somewhat 18 imply that they don't believe, they don't, reliability 19 frequency of event data, that you can't have a double 20 guillotine break that when you consider the 21 characteristics of the most serious breach of the 22 pressure boundary, that it just falls outside of the 23 likelihood range.
24 And as a consequence, they're looking 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
108 the next one up that is the moisture ingress. Is that 1
a basis for excluding mention of airing?
2 Because obviously you've captured it as 3
the limitation condition because there's more to be 4
said about it, I'm sure.
5 But is that the way you interpreted it?
6 MR. MUÑIZ: It doesn't ring me a bell the 7
specifics of this. Can I call up X-Energy to kind of 8
chime on that?
9 If you can speak up?
10 MR. METZROTH: Could you repeat the 11 specific question?
12 CHAIR MARTIN: Actually, Kyle, could you 13 just stand over here to make sure that everyone can 14 hear you.
15 MR. METZROTH: So, the gist of the question 16 was the statement that you provided here, which 17 effectively excludes the European press.
18 Because it's fine that you've kind of 19 excluded the largest breaks based on your PRA model.
20 (Simultaneous speaking.)
21 MR. NIGH: It's based on an evaluation of 22 the design, and looking at the frequency of various 23 break sizes.
24 Including that there are certain break 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
109 sizes that fall in the design basis event region; and 1
certain fall outside of that.
2 So, the size that we have, we don't have 3
4 (Simultaneous speaking.)
5 MR. METZROTH: If you pressurize enough --
6 MR. NIGH: -- to have a significance. We 7
mentioned earlier we evaluate any possibility of that 8
occurring, but it's not enough, it's not break size 9
where we have a significant amount that gets in such 10 that it's a big concern.
11 MR. METZROTH: Yes, and you got to kind of 12 where you said there's no possibility for like a 13 double heat guillotine break, for example.
14 MR. NIGH: Right.
15 MR. METZROTH: Like, we did look what if 16 two holes open up in the helium pressure boundary.
17 And, that event is sufficiently unlikely that it 18 wouldn't be covered by this PDC.
19 PARTICIPANT: Can you identify yourselves 20 again for the court reporter, please?
21 MR. METZROTH: Oh, sorry, Kyle Metzroth.
22 MR. NIGH: Drew Nigh.
23 CHAIR MARTIN: It seemed obvious connecting 24 the dots, but I just wanted to hear it from you two.
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110 MR. NIGH: Thank you.
1 MR. MUÑIZ: That's how I was going to 2
answer, but.
3 (Laughter.)
4 MR. MUÑIZ: I'm saved. PDC 26 next slide.
5 It was discussed earlier a little bit, PDC 6
- 26. There are several requirements the provisions, we 7
evaluated each one of them.
8 The key one being in the event and diverse 9
means to achieve, they shut down and a puncture rod is 10 one of the method. And the other one is inherent 11 reactivity feedback I discussed.
12 And, I'm not going to go through it.
13 There's RFTC and CTC related to DVEs. And DVEs and 14 DVAs, and AOOs.
15 And, yes, so we felt that the underlying 16 intent of the Reg Guide 1.232 is achieved by this PDC 17 26 proposed.
18 MEMBER KIRCHNER: This is Walt Kirchner.
19 Could you elaborate? I'm not following the logic 20 here. This is a moderated, a gas-cooled graphite 21 moderated TRISO fueled reactor.
22 As you cool down the plant, it adds 23 reactivity. So I'm not getting the logic that 24 certainly that characteristic is desirable to prevent 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
111 reactivity insertion accidents, or overheating. And 1
suppression of reactor power oscillations.
2 But as you cool down this system, you will 3
be adding reactivity. So, I don't understand the 4
logic of saying the inherent feedback effect is part 5
of the means, diverse means of achieving shutdown.
6 You're going to need control rods and 7
shutdown, and an independent shutdown mechanism to 8
achieve a cold shutdown condition.
9 MR. MUÑIZ: I'm going to call upon Dan or 10 X-Energy. I'm not a reactor engineer, but my 11 understanding is, is that the inherent reactivity 12 feedback mechanism demonstrated by the sum of the task 13 team, and to be further demonstrated a by fuel 14 qualification.
15 It demonstrated that the negative reactive 16 feedback is sufficient enough to reach a shutdown 17 condition.
18 That's an interesting --
19 (Simultaneous speaking.)
20 MEMBER KIRCHNER: No, no, the negative 21 feedback protects you against overheating reactivity 22 transients. It doesn't shut you down.
23 It adds reactivity as you cool down the 24 system. So therefore, you need sufficient reactivity 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
112 in the control systems, likely control rods, some 1
designs, smaller designs may use drones.
2 But, and then you'll need two independent 3
mechanisms to satisfy the overall intent of PDC 26.
4 But the inherent reactivity feedback, which is 5
desirable for overheating and reactivity insertion 6
transients, doesn't work to your advantage when you're 7
cooling down a reactor like this.
8 You're adding reactivity as you cool down 9
the system.
10 CHAIR MARTIN: I will add, I noticed, I 11 have to check but cold shutdown is not used here, 12 right?
13 MEMBER KIRCHNER: No, it isn't. The 14 condition already issued back, it was cited by the 15 applicant in one of the -- no, sorry.
16 It was cited in the Reg Guide 1.232 of the 17 conditions position on achieving shutdown. And not 18 requiring a cold shutdown, realizing that the mass, 19 the inventory, the thermal inertia for lack of a 20 better description of such a system, doesn't allow you 21 to achieve a cold shutdown condition like is possible 22 in a LWR system, in a reasonable period of time.
23 So, the condition recognized that and the 24 Agency made provisions for that. But what I'm 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
113 objecting to is that the inherent feedback that you 1
get out of this kind of reactor design, protects you 2
against overheating transients, protects you against 3
reactivity insertion accidents.
4 But it doesn't help you shut down. You 5
have to compensate for the fact that as you shut down 6
this system and it cools down, that that adds 7
reactivity and hence, the reactor control systems, 8
reactivity control systems need to be designed 9
accordingly.
10 Then, to have a diverse means, you have 11 usually control rods and then shutdown rods. And for 12 most MHTGR designs that I'm familiar with, so that you 13 can actually have a means to ensure that you don't 14 return to criticality as the system cools down.
15 CHAIR MARTIN: So, the PDC, I wasn't and 16 maybe I'm being too generous, but the PDC as they have 17 written, has mentioned movable poisons.
18 I guess they don't, doesn't necessarily 19 apply what you say here, just control rods. I guess 20 I felt like the PDC was a still, maybe still open to 21 some interpretation about the means.
22 They had pointed specifically to PDC 11 23 related to the inherent reactivity feedback. I guess 24 my impression coming out of the earlier meeting, 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
114 that there was at least an opportunity for X-Energy to 1
address that in a more specific manner.
2 PARTICIPANT: Well, don't you want to say 3
something?
4 MR. VAUGHN: Yes, definitely.
5 PARTICIPANT: Please introduce yourself.
6 MR. VAUGHN: Yes, yes, Steve Vaughn, 7
Licensee X-Energy. Yes, great question, Member 8
Kirchner.
9 And we can discuss more details in the 10 closed portion if you want, but you're right, the 11 inherent reactivity will take heat down to a certain 12 temperature, right, then it will start to add positive 13 reactivity.
14 And so PDC RTC 26 this let's say shutdown 15 rods, will cover all modes, all temperatures. If you 16 want to get into the details in the closed, we can 17 talk to you in a little more detail about that. But 18 we're getting into specific design criteria right now.
19 CHAIR MARTIN: Does the way you've written 20 that the PDC 26, Bill, support what Walt's saying here 21 about a diverse and even cold shutdown? Something a 22 specific concern.
23 MR. VAUGHN: The comment that safety 24 analysis will show that combination of inherent 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
115 reactivity feedback in RFDC 11, plus PDC RFC 26, the 1
safe shutdown rods, will get you to safe shutdown 2
margin for all modes.
3 CHAIR MARTIN: Yes, I guess I agree. I 4
feel like we're getting close to proprietary content.
5 So I don't know if we can pursue this.
6 What do you feel, Walt? I mean.
7 MEMBER KIRCHNER: No, I'm just making the 8
observation that you don't get to the shutdown based 9
on the inherent feedback conditions.
10 That they will provide a means for holding 11 the reactor shutdown so that they can go to refueling, 12 et cetera, et cetera.
13 So, I'm just making a point that we 14 shouldn't mix up, yes, this is true. You've got a 15 desirable design characteristic for this system to 16 prevent reactivity insertion accidents, and 17 overheating. And that's inherent.
18 You still need two control rod control 19 systems to achieve and meet the goal of PDC 26.
20 CHAIR MARTIN: All right, so like I said, 21 I still don't think we can go much further into this 22 without getting into some very specific stuff.
23 MEMBER KIRCHNER: Okay.
24 CHAIR MARTIN: But it's a good point.
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116 MEMBER KIRCHNER: No, I just, the first 1
bullet there just is a little misleading.
2 CHAIR MARTIN: I would agree.
3 MEMBER KIRCHNER: To meet the intent of PDC 4
26, you're going to need in the case of an MHTGR 5
- design, two active control
- rod, control-like 6
reactivity control systems. That's my point.
7 With the inherent reactivity feedback is 8
a desirable characteristic that will prevent the power 9
oscillations, and other aspects that are mentioned in 10 PDC 11 and 12.
11 PARTICIPANT: Yes, we can take it up on the 12 closed session, thank you.
13 MR. JUNG: Yes, we'll wait until that 14 closed session.
15 CHAIR MARTIN: All right, well we're like, 16 I'm not sure our schedule supports a closed session.
17 Is that fair to say?
18 DR. BLEY: This is Dennis. I wanted to 19 sneak a question in kind of for Walt. When I read 20 that first bullet, it doesn't say that means 1 and 21 means 2 either one works. It says and.
22 So, I'm wondering if we're, the arguments 23 about interpreting at that bullet saying that you can 24 wait till the later session for that.
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117 MEMBER KIRCHNER: Yes, it can, Dennis.
1 You're correct. I was just reacting to that, the way 2
it is presented in the view graph, which is different 3
than the actual PDC.
4 CHAIR MARTIN: It is different than what it 5
appears in any.
6 MR. SNODDERLY: So Bob, this is Mike 7
Snodderly with the ACRS staff. We have the ability to 8
go to a closed session. There is a MS Teams meeting 9
available.
10 I suggest we finish the open session, get 11 public comment, and then we can, and then see what 12 time, what the time is like and figure out next steps.
13 MR. MOORE: This is Scott Martin. We do 14 need to start the afternoon session at 1:00 o'clock.
15 CHAIR MARTIN: Exactly, so we do have a 16 constraint. I'd like to provide a little time for 17 lunch but we're used to pinching that a little bit.
18 Anyway, let's proceed and we'll see if we 19 can't provide a little more clarity in a closed 20 session on this question.
21 MR. MUÑIZ: Yes, I'm a substitute player so 22 expectations should be a little bit lower.
23 So, this is time for procedural heat 24 removal passage system for, within that particular 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
118 function is done through the fuel, and that 1
radionuclide limits are met for the DVEs and DVAs and 2
a 50-34 limit.
3 There's a active system that provides the 4
decay heat removal function, such that the SARRDLs 5
have not exited for AOOs.
6 But it's a CDC, normal operation size for 7
CDC, the helium, the circulating system plays a role 8
there.
9 The HP, helium pressure boundary 10 maintaining core geometries as discussed earlier in 11 PDC 7, related to integrity of the helium pressure 12 boundary system.
13 We felt that overall, the intent of direct 14 access on that.
15 Okay, next one.
16 I think this was the last item before the 17 limitation condition. PDC 70, reactor vessel and 18 reactor systems short design basis, and there's some 19 changes are made to be a little bit more specific 20 regarding the helium pressure boundary, and core 21 internal support reactor integrity.
22 And also, achieving low and also achieving 23 low probability of radically profligating failure 24 during DVEs and DVAs.
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119 And also, that also supports PDC 14 that 1
was discussed by the X-Energy earlier this morning, 2
ensuring core geometry for passive heat removal of 3
residual heat.
4 Also, it's part of this PDC, it supports 5
PDC 34, permitting, permits insertion of the neutron 6
observers and maintain core reactor inherent 7
protection.
8 As we discussed earlier, it is tied to PDC 9
11 and 26. So, we feel that intent of the MHTGR DC 70 10 is met.
11 CHAIR MARTIN: One just comment/question 12 possibly.
13 The language of course, focuses on the 14 core internals. You mentioned ensure geometry for 15 passive heat removal.
16 There's also a permit insertions of 17 neutrons. But in addition, guarding reactivity 18 control, the integrity of those neutron absorbers has 19 to be assured like a light water reactor, because we 20 worry about control rod elements. Same sort of thing 21 here.
22 And, those familiar with high temperature 23 gas reactors might be aware that Japan's HGTR 24 facility, they were very sensitive about that. 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
120 they have a very interesting reactivity control 1
system.
2 These delay neutron, or excuse me, control 3
rod insertions, in the hottest part of the core to 4
make sure that they don't have this concern.
5 And, I can read the PDC and come to an 6
interpretation that obviously addresses some thermal 7
safety limit on control rod temperatures.
8 Do you feel like the language is strong 9
enough? Did you think through that particular aspect 10 of PDC 70 when you were going through this?
11 MR. MUÑIZ: I think about I can help.
12 Dan's chiming in but I think overall, that the 13 language there in terms of the scope of reactor vessel 14 and the internals inside of it, talk about how do you 15 captures overall, all the elements of safety, safety 16 significant assets.
17 Dan, can you chime in?
18 CHAIR MARTIN: It's certainly a temptation 19 to look at any one of these. I mean, for instance we 20 were looking at 26 and that's very much a reactivity 21 control safety function.
22 But I think here with 70, it actually 23 crosses the safety functions. It's not just a heat 24 removal, but there's also, and it touches reactivity 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
121 control and its integrity.
1 MR. MUÑIZ: Yes, eventually it gets to the 2
issue of performing requires safety functions, and the 3
structural integrity as well as the reactivity 4
insertion.
5 All those things play together.
6 CHAIR MARTIN: Thank you.
7 MR. MUÑIZ: Next slide.
8 So keeping an eye on that, I'm not going 9
to labor too much. The first one is the really the 10 kind of more overarching limitation condition given 11 the preliminary nature of the design, as well as 12 implementation of LMP.
13 We are imposing a, this overarching 14 limitation of condition that says basically the 15 applicants for licenses referencing this topic report, 16 would confirm these PDCs are sufficient.
17 Because the further implementation of the 18 design and LMP, may identify changes were dealt up 19 from the what we proposed.
20 DR. BLEY: Excuse me, this is Dennis Bley.
21 I want to make a comment on these, and I 22 wanted to do it before you go through them all so you 23 could maybe address my comment and question as you go 24 through.
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122 Number 1 and 3 here really bothered me.
1 Number 2 bothered me a little bit. And, my concern is 2
my understanding of topical reports once they're 3
approved, is that when you actually use them in the 4
license application, you have to essentially do the 5
things that are listed here.
6 And if we're taking out a few things, it 7
might give people the impression unless limitations 8
and conditions are proposed, they don't need to go 9
back over everything in the topical report and make 10 sure it's applicable to their design.
11 Now, number 2 is, fits that as well, but 12 number 2 has at least the sense of something that 13 might be forgotten.
14 But it seems to me these are basically 15 unnecessary, and could give a wrong impression that 16 you need something like this to relook at any issues 17 in the topical report, when the license comes up.
18 So, if you can talk about that as you go 19 through these, I'd appreciate it.
20 MR. MUÑIZ: Yes, our intention is not to 21 give that impression that the rest of the topical 22 report that we approve are not evaluated for 23 applicability.
24 We felt that number 1 and 3 are in 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
123 same realm in terms of kind of more of a, I think it 1
was a sufficient number 1.
2 We felt it was sufficient to --
3 (Simultaneous speaking.)
4 DR. BLEY: I feel like a checklist for you 5
guys on what to look for when the actual application 6
comes in. But I stand with what I said before about 7
why it bothers me.
8 MR. MUÑIZ: Purely speaking, number 1 and 9
3 may not have been imposed, but we felt that still is 10 a unique approach.
11 And LMP implementation being that's fully 12 exercised, we wanted to emphasize this area very 13 strongly so that we actually give the clear indication 14 that what we are proving is based on somewhat limited 15 implementation of the design, as well as the LMP.
16 DR. BLEY: Yes, that's --
17 (Simultaneous speaking.)
18 DR. BLEY: -- that's true, but it always 19 is required for using a topical report that you make 20 sure all the assumptions in that report apply to your 21 design.
22 So, my worry is what I said, that somebody 23 might be reading this and thinking, unless things are 24 spelled out in limitations and conditions, they don't 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
124 need to do much more when they use it in the license 1
application.
2 I'm sure that doesn't apply to this 3
applicant, but it might to others.
4 MR. MUÑIZ: Understood. I think it's 5
something that X-Energy is, for at least for X-Energy, 6
are intending to be part of the future licensing 7
applications and so on, I think it's there.
8 But we understand your point, and but 9
fundamentally though, all the fundamentals of use of 10 topical reports as approved by the NRC staff, tends to 11 be consistently emphasized to the other applicants.
12 CHAIR MARTIN: We might have to look at 13 these as IOUs, right? Because we're on conformation, 14 future license application reference.
15 PDCs, and I'm voicing an opinion, should 16 ultimately be without L&Cs. At some point when you 17 have all the information, there are no L&Cs associated 18 with the GDC, right? Those are design criteria for 19 light water reactors.
20 Unlike other topic reports, I can see this 21 being revised much later in the license application 22 process where it's clear, meaning you cleared the L&Cs 23 because you have all the necessary information.
24 I know the PDC process is relatively new.
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125 Surprisingly, it's only the third one we've seen. But 1
how do you feel about the idea that to a point, you 2
need to clear the L&Cs?
3 That's for really both the applicant that 4
you come to an agreement that these are the ones that 5
apply to Xe-100, and we are satisfied with this set 6
that it covers kind of after you've gone through these 7
L&Cs, and that I've confirmed and I've seen the PRAs, 8
I've seen the accident analyses.
9 There's convincing evidence that they have 10 really done everything they said in this PDC document.
11 Now, I will note that of course, I think 12 both in your SE and in their topical, it kind of says 13 yes, we may revisiting this.
14 But the ultimate goal I think, should be 15 to get rid of these L&Cs. Is that how everyone feels?
16 MR. MUÑIZ: From a staff's perspective, 17 that's a ideal case where there's no limitation 18 addition. Plus as these GDCs are applied, there might 19 be some lessons learned on how exactly this criteria 20 led.
21 So there could be a future improvements.
22 CHAIR MARTIN: Yes, Steven?
23 MR. VAUGHN: Before X-Energy had agreed 24 during the upgrading license application, you expect 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
126 this top report to be a rev 4 and or 5, and we 1
wouldn't expect any license conditions on it.
2 CHAIR MARTIN: You can't have an IOU and 3
approve a plant, right?
4 MR. MUÑIZ: Next slide.
5 Just quick conclusion. So, based on our 6
review, we found that X-Energy has provided a 7
reasonable set of PDCs that are appropriate for 8
establishing the requirements of the Xe-100 design, 9
consistent with the intent of the Reg Guide and LMP 10 guidance that I discussed.
11 These are subject to the limitation 12 condition we discussed. We found that this PDC 13 established the necessary design fabrication, 14 construction, testing and improvements design criteria 15 for safety significant SSEs to provide reasonable 16 assurance that the design could be operated with undue 17 risk to health and safety of the public.
18 Therefore, revision 3 of the topical 19 report is suitable for referencing and future 20 licensing applications under 10 CFR Part 50, Parts 50 21 and 52, for the Xe-100 design.
22 That's all we have.
23 CHAIR MARTIN: Great, open up for any 24 member or consultant questions? Anybody online?
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127 Once, going twice?
1 I think at this point, I could open up for 2
public comment. So anyone, any member of the public 3
like to?
4 Ed Lyman, I see your hand raised.
5 DR. LYMAN: Yes, hi, it's Edwin Lyman, from 6
Union of Concerned Scientists. Can you hear me?
7 CHAIR MARTIN: Yes.
8 DR. LYMAN: Yes.
9 Yes, I'd just like to say I'm disappointed 10 that there was not further attempt to resolve Member 11 Kirchner's comments about the diverse reactivity 12 control system, GDC.
13 Just from what was presented here, it does 14 not look like what has been proposed as consistent, or 15 the same level of safety as a light water reactor, 16 because light water reactors also under most 17 conditions, have inherent negative reactivity 18 feedback. Yet, they have two diverse shutdown systems 19 in addition to that.
20 So, at least from what's presented here, 21 it looks like this would not have the same or 22 equivalent level of safety to light water reactors.
23 So, I'm hoping that more information about 24 that can be provided publicly, because I don't have 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
128 confidence in what I've seen.
1 The second point with regard to functional 2
containment. Again, I would, I think Member 3
Kirchner's observations are very relevant.
4 This is something that of course, is 5
cross-cutting. It's also applied to the Natrium 6
design. Every other plant with a functional 7
containment. I'm deeply concerned.
8 And I have very little confidence in the 9
process, especially in a Part 50 context where these 10 are being used, this approach is being used for 11 fundamental, making fundamental design choices based 12 on an inadequate dataset.
13 And, as is the case with the Natrium, 14 there are key issues related to fuel performance that 15 have not, that there is not the experimental data 16 available to validate those. Yet this key decision 17 about whether to have a containment or not depends 18 critically on the fuel performance, and questions that 19 may not be resolved until the plant is actually 20 operating. And, fuel performance data has been 21 accumulated.
22 So, I'm deeply concerned that for these 23 paper designs to rely too heavily on expectations 24 about fuel performance to make these critical 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
129 choices like functional containment or not, put great 1
risk on the applicant.
2 Okay, so that's the applicant's problem.
3 But I'm worried that the NRC ultimately is not going 4
to make a decision to deny an operating license, even 5
if there is a significant design choice that turns out 6
to be wrong, based on the accumulation of operating 7
data. So, I think a holistic, you have to take a step 8
back and look at what is being proposed here, and 9
whether there should be more conservative design 10 criteria, especially for a first of a kind plant.
11 Thank you.
12 CHAIR MARTIN: Thank you.
13 Are there any other further questions from 14 members of the public?
15 (No audible response.)
16 CHAIR MARTIN: All right, I need help 17 transitioning to a closed session so we can kind of 18 answer the, that one question that came up.
19 MR. SNODDERLY: Yes, Dr. Martin. So, I ask 20 that you close this open session and then we would be 21 the closed session invite. If there's anyone that 22 does not have the invitation to the closed session, 23 could you please raise your hand and we'll make sure 24 we forward it to you.
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130 CHAIR MARTIN: Okay, I don't think I got 1
it.
2 MR. SNODDERLY: Okay, so Derek, if you 3
could please forward the invitation to Bob. Everybody 4
else has it? Okay.
5 And then, so once Chairman Martin closes 6
this session.
7 CHAIR MARTIN: Yes, so all of a sudden we 8
have thee hands raised. Are these members of the 9
public?
10 MR.
SNODDERLY:
James is our court 11 reporter. So Derek, please send the invite to James 12 Cordes.
13 MR. WIDMAYER: Okay.
14 MR. SNODDERLY: Or to Shannon, then Shan, 15 we need to get it to James. And I'm sorry, Mr.
16 Stuhdreher.
17 MR. STUHDREHER: Stuhdreher, yes.
18 MR. SNODDERLY: Stuhdreher, can you please 19 identify yourself or your question?
20 MR. STUHDREHER: Yes, I was asking for the 21 meeting for the closed portion of this. I'm with the 22 Department of Energy.
23 MR. SNODDERLY: That's up to, can someone 24 from X-Energy please send an invite, or?
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131 MS. MADDOCKS: Hey, this is Jessica with 1
X-Energy, Project Manager. Check your email. I sent 2
it out to you, but it's in an email. It's not a 3
meeting notice.
4 MR. STUHDREHER: Oh, okay, all right, thank 5
you.
6 MR. SNODDERLY: Thank you, Jessica.
7 Is there anyone on the line, anyone else 8
on the line that feels that they have a need to know?
9 Please identify yourself and make a request so that we 10 can determine whether.
11 (Pause.)
12 CHAIR MARTIN: Okay, if we can, I don't 13 want to leave this right, until James, until we, 14 James, can you please, let's stay on the line until 15 James confirms that he has the invite.
16 PARTICIPANT: No dogs allowed at the 17 meeting.
18 CHAIR MARTIN: Yes, no dogs.
19 Okay, James, let's --
20 MEMBER DIMITRIJEVIC: I don't also see 21 invite in my email. So this is Vesna, hi. So Derek, 22 can you also make sure that you send it to my Gmail?
23 Since I'm not in Boston.
24 MR. SNODDERLY: Okay, I will do that right 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
132 now.
1 MEMBER DIMITRIJEVIC: Okay, thanks.
2 MR. SNODDERLY: And I'm going to do it to 3
James, too.
4 CHAIR MARTIN: Yes, thanks, Mike. I 5
couldn't get a, I've been forwarding it but I've lost 6
the ability to do such all of a sudden.
7 MR. SNODDERLY: Okay.
8 MR. WIDMAYER: So, I think it was just 9
James and --
10 MR. SNODDERLY: Right, and James.
11 MEMBER DIMITRIJEVIC: And, Vesna.
12 MR. WIDMAYER: And, Vesna, yes.
13 MR. SNODDERLY: Yes, I've got Vesna.
14 Shan, are you on the line?
15 (No audible response.)
16 MR. SNODDERLY: I don't, all right, James, 17 please put your email address in the chat. For this 18 meeting.
19 MR. WIDMAYER: Yes, he just did.
20 MR. SNODDERLY: Okay.
21 MR. WIDMAYER: Walt, you've got your hand 22 up again?
23 MEMBER KIRCHNER: Yes, could you forward 24 that closed invitation?
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133 MR. WIDMAYER: Oh, yes, I missed, you, yes.
1 Hey, Mike, can you forward it to Walt?
2 MR. SNODDERLY: Yes.
3 (Pause.)
4 MR. SNODDERLY: Walt, I just sent it to 5
your NRC email address. Is that acceptable?
6 (No audible response.)
7 DR. BLEY: Hey Mike, Dennis Bley.
8 MR. SNODDERLY: Yes, Dennis?
9 DR. BLEY: I was sure I had it but I've got 10 the one for tomorrow. I don't have this one.
11 MR. SNODDERLY: No worries, no worries, no 12 worries. I think the main, we just need to get, I'm 13 doing that now.
14 MR. WIDMAYER: Yes, you should have it 15 Dennis.
16 (Pause.)
17 MR. SNODDERLY: All right, I've asked 18 Chairman Martin to please close this meeting and 19 everyone please go to the closed session.
20 CHAIR MARTIN: Great, I'm going to use the 21 gavel here. We're closing this open session on the 22 Xe-100 principal design criteria.
23 (Whereupon, the above-entitled matter went 24 off the record at 12:04 p.m.)
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NRC Staff Review of the X-energy Principal Design Criteria Topical Report for the Xe-100 Reactor Design Adrian Muniz, Senior Project Manager Ian Jung, Senior Reliability and Risk Analyst Dan Beacon, Nuclear Engineer Office of Nuclear Reactor Regulation Division of Advanced Reactors and Non-Power Production and Utilization Facilities
Topical Report Purpose
- Purpose of the topical report:
o Describes X-energys process for developing principal design criteria (PDC) o Requests the U.S. Nuclear Regulatory Commission (NRC) staff review and approval of proposed PDCs
- To comply with applicable regulatory requirements under Title 10 of the Code of Federal Regulations (10 CFR) Parts 50 and 52
- To support the design and licensing process 2
Review Chronology
- Revision 1 of the topical report (ADAMS Access No. ML22195A260) on July 13, 2022
- Staffs preliminary questions and X-energy responses in a letter dated December 30, 2022 (ML22364A293)
- Regulatory audit to support its review based on an audit plan (ML23009B755) and documented its observations in an audit report dated January 19, 2023 (ML23093A215).
- Revision 2 (ML23181A172) on June 30, 2023
- Staffs additional questions (ML23277A274) on Revision 2 and discussion with X-energy in a public meeting (ML23346A120)
- Revision 3 (ML24047A308) addressing staff questions during the review and X-energys self-identified items
- Draft safety evaluation issued (ML24190A060) on July 17, 2024 (based on Revision 3) 3
Regulations
- In accordance with the provisions of 10 CFR Parts 50 and 52, licensing applicants must submit PDCs for the proposed facility.
o For example, 10 CFR 50.34(a)(3)(i), which requires, in part, that applications for a construction permit (CP) include PDCs for the facility.
- 10 CFR Part 50, Appendix A discusses the scope and content of PDCs:
[PDCs] establish the necessary design, fabrication, construction, testing, and performance requirements for structures, systems, and components important to safety; that is, structures, systems, and components [SSCs] that provide reasonable assurance that the facility can be operated without undue risk to the health and safety of the public.
4
Guidance
- Regulatory Guide (RG) 1.232, Guidance for Developing Principal Design Criteria for Non-Light Water Reactors (ML17325A611) o Appendix C provides Modular High-Temperature Gas Reactor Design Criteria (MHTGR-DCs)
- RG 1.233, Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light Water Reactors (ML20091L698) o Endorses Nuclear Energy Institute (NEI) 18-04, Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development, Revision 1 (ML19241A472)
- RG 1.253, Guidance for a Technology-Inclusive Content of Application Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light-Water Reactors, (ML23269A222) o Endorses NEI 21-07, Technology Inclusive Guidance for Non-Light Water Reactors - Safety Analysis Report: For Applications Utilizing the NEI 18-04 Methodology, Revision 1 (ML22060A190).
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Xe-100 Design
- Key features
- Pebble bed, high-temperature gas-cooled reactor (HTGR)
- Tri-structural isotropic (TRISO) fuel
- Graphite moderator
- Helium-cooled
- Passive heat removal
- No active electrical power to perform required safety functions 6
Xe-100 PDC Approach and Overview
- Xe-100 PDCs are based on MHTGR-DCs (Appendix C of RG 1.232) o Xe-100 and MHTGR substantially similar o Some PDCs modify MHTGR-DCs to reflect Xe-100
- Xe-100 PDCs are also based on the LMP implementation o Risk-informed and performance-based approach o Required safety functions (RSFs), required functional design criteria (RFDC),
probabilistic risk assessment (PRA) safety functions (PSFs), and complementary design criteria (CDC) o Terminologies based on the LMP
- The NRC staffs review used applicable regulatory guidance, mainly RGs 1.232 and 1.233 as applied to PDCs.
o Evaluate deviations from RG 1.232 in consideration of the key Xe-100 design features and the LMP implementation 7
General Changes to PDCs
o Use of the term safety-significant o Scope of licensing basis events (LBEs) in PDCs o Single PDC for monitoring, testing, inspection, and surveillance of safety-significant SSCs o PDC 26, Reactivity control systems o PDC 34, Residual heat removal 8
Use of the term safety-significant
- Replace important to safety from RG 1.232 with safety-significant to align with language from NEI 18-04
- Advanced Reactor Content of Application Project (ARCAP) DANU-ISG-2022-01, Review of Risk-Informed, Technology-Inclusive Advanced Reactor ApplicationsRoadmap (ML23277A139) identified that some SSCs may be important to safety but not safety-significant per NEI 18-04 process o No gap because of use of RG 1.232 9
Scope of LBEs for the Proposed PDCs
- X-energy replaces the terms such as postulated accident or accident conditions used in MHTGR-DCs in RG 1.232 with those describing LBEs* used in NEI 18-04.
Proposed PDCs need to address the functions provided by both safety-related (SR) and NSRST SSCs.
- Xe-100 design is preliminary and implementation of the LMP process is in progress. Proposed PDCs may not represent a full set of PDCs for all SSCs that are safety-significant. The NRC staff proposes a Limitation/Condition (item (1)).
- Anticipated Operational Occurrences(AOOs), Design Basis events (DBEs), Beyond Design Basis Events (BDBEs),
and Design Basis Accidents (DBAs) 10
PDCs for normal operations and use of Owner Controlled Design Criteria (OCDCs)
- X-energys proposed PDCs (i.e., 2, 4, 10, 13, 15, 19, 22, 26, 34, 44, 60, 61, and 64) include criteria associated with normal operations or conditions.
- X-energy uses OCDCs to designate design criteria for NST SSCs that are not required to be met during AOOs, DBEs, or DBAs.
o NST SSCs are not classified as safety-significant SSCs according to the LMP process.
o OCDCs are not part of the Xe-100 design bases scope
- Use of OCDCs for design criteria that correspond to NST SSCs distinguishes OCDCs from PDCs (RFDCs and CDCs) that correspond to SR and NSRST SSCs.
11
Replacement of single-failure criterion with reliability criterion
o Commission approval in SRM-SECY-03-0047
- The NEI 18-04 methodology subjects the design to a reliability criterion (e.g., a reliability target) and to an evaluation of defense-in-depth (DID) adequacy based on assessments of event sequences.
12
PDC 16: Use of functional containment concept
- PDC 16 uses the language of MHTGR-DC 16 with changes.
o PDC-RFDC 16 for barriers in fuel particles and pebbles for DBEs and DBAs.
o PDC-CDC 16 for a barrier of the helium pressure boundary for AOOs.
- Additionally, replaces design conditions important to safety with design limit to clearly articulate that a design limit related to the functional containment exists and cannot be exceeded.
- Meets the intent of MHTGR-DC 16 in RG 1.232.
o The Commission approved the use of functional containment concept in Staff Requirements Memorandum (SRM) to SECY-18-0096.
13
PDC 6, Monitoring, Inspection, Testing, Surveillance
- X-energy proposes PDC 6 as a single criterion for monitoring, testing, inspection, and surveillance of safety-significant SSCs.
o Subsumes MHTGR-DCs 18, 31, 36, 37, 45, and 46
- Meets the underlying intent of the related MHTGR-DCs in RG 1.232.
o Scope of activities consistent with those that would be required by the subsumed MHTGR-DCs o Broadly applicable to all safety-significant SSCs (i.e., SR and NSRST SSCs) 14
PDC 11, Reactor inherent protection
- Meets the intent of MHTGR-DCs 11 and 12
- Also provides for one of the two means to meet the intent of MHTGR-DC 26 (adequately control heat generation)
- Sufficient negative reactivity feedback ensures fuel performance and radionuclide release limits are not exceeded for DBEs and DBAs, and that specified acceptable system radionuclide release design limits (SARRDLs) are not exceeded for AOOs
- Condition/Limitation 2: The in the power operating range phrase is expanded to ensure that safety analyses include the full scope of the power operating range, DBE, and DBA conditions 15
PDC 14, Reactor helium pressure boundary
- Integrity and testing considerations are removed from corresponding MHTGR-DC 14.
o Covered by PDC 70 and PDC 6, respectively.
- Ingress of moisture, air, secondary coolant, or other fluids is replaced with moisture ingress.
o No risk-significant AOOs, DBEs, or DBAs with unacceptable ingress of air or other fluids. (Limitation/Condition item 3 applies) o Moisture encompasses the secondary coolant (water).
16
PDC 26, Reactivity control systems
- The independent and diverse means are control rods (means 1) and inherent reactivity feedback (means 2)
- Control rods insert and maintain safe shutdown for DBEs and DBAs (RFDC)
- Independent and diverse means ensure SARRDLs and HPB limits are not exceeded, and safe shutdown is achieved and maintained for AOOs (CDC) and normal operations (OCDC)
- Means to support shutdown interventions: Included verbatim from MHTGR-DC 26 paragraph 4 (PDC)
- Further supported by PDC-RFDC 11 (core cooling/heat generation)
- All underlying intents of MHTGR-DC 26 are covered
- Specific design features are not being approved in this SE.
17
- Passive system for decay heat removal (DHR) to ensure fuel and radionuclide release limits are met for DBEs and DBAs (RFDC)
- Active means to ensure DHR and residual heat are removed such that SARRDLs are not exceeded for AOOs (CDC) and normal operations (OCDC) o The function of the HPB to maintain core geometry is covered in PDC 70
- All aspects of MHTGR-DC 34 are covered 18
PDC 70, Reactor vessel and reactor system structural design basis
- HPB and core internals support reactor integrity and low probability of rapidly propagating failure during DBEs and DBAs.
o Supports PDC 14.
- Ensure geometry for passive heat removal of residual heat.
o Supports PDC 34.
- Permit insertion of neutron absorbers and maintain reactor inherent protection.
o Further bolsters PDCs 11 and 26.
- All aspects of MHTGR-DC 70 covered.
19
Proposed Limitations and Conditions (1) X-energy is requesting approval for the proposed PDCs based on a preliminary design and the LMP implementation at the time of the topical report submittal. Xe-100 design changes and associated LMP implementation could necessitate a revision to the proposed PDCs described in the TR.
Therefore, future licensing applicants referencing the topical report must confirm that the PDCs in this topical report remain appropriate for its design. In addition, if additional or revised PDCs are identified that are not within the scope of what is approved in this topical report, those PDCs will be subject to further NRC staff review.
(2) For PDC-RFDC 11, X-energy used the words in the power operating range. This phrase has the potential to complicate the applicability of PDC-RFDC 11 to the scope of MHTGR-DC 12. Power oscillations or reactivity upsets that may occur outside the power operating range should be assessed. Accordingly, the NRC staff conditions the acceptance of PDC-RFDC 11 on confirmation by future licensing applicants referencing this topical report that applicable safety analyses cover the full scope of the operating range, DBE, and DBA conditions for the final design.
(3) For PDC 14, X-energy is proposing to delete the words ingress of air, secondary coolant, or other fluids from MHTGR-DC 14 and replace it with the words moisture ingress. For justification, X-energy states that no risk significant AOOs, DBEs, or DBAs were identified with unacceptable ingress of air or other fluids. This cannot be verified at the present state of the Xe-100 design. Accordingly, the NRC staff conditions the acceptance of this PDC on the NRC staffs review of AOOs, DBEs, and DBAs as part of a future license application referencing this topical report.
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Conclusion
- X-energy has provided a reasonable set of PDCs that are appropriate for establishing requirements for the Xe-100 design consistent with the intent of RG 1.232 and the LMP guidance.
- Subject to these limitations and conditions, these PDCs establish the necessary design, fabrication, construction, testing, and performance design criteria for safety-significant SSCs to provide reasonable assurance that the Xe-100 design could be operated without undue risk to the health and safety of the public.
- Revision 3 is therefore suitable for referencing in future licensing applications under 10 CFR Parts 50 and 52 for the Xe-100 design.
21
Abbreviations ARDC - advanced reactor design criteria BDBE - beyond design basis event CFR - Code of Federal Regulations CP - construction permit DANU - Division of Advanced Reactors and Non-Power Production and Utilization Facilities DC - design criterion DBA - design basis accident DBE - design basis event GDC - general design criterion HPB - helium pressure boundary L&C - limitation and/or condition LWR - light-water reactor MHTGR - modular high temperature gas reactor NEI - Nuclear Energy Institute NRR - Office of Nuclear Reactor Regulation NSRST - non-safety related with special treatment NST - non-safety related with no special treatment OCDC - Owner Controlled Design Criterion PDC - principal design criterion PSAR - preliminary safety analysis report QA - quality assurance RG - Regulatory Guide SAFDL - Specified acceptable fuel design limit SARRDL - Specified acceptable system radionuclide release design limit SSC - structure, system, or component SE - safety evaluation SR - safety-related 22
References
- RG 1.232, Guidance for Developing Principal Design Criteria for Non-Light Water Reactors (ML17325A611)
- RG 1.233, Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light Water Reactors (ML20091L698)
- RG 1.253, Guidance for a Technology-Inclusive Content of Application Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light-Water Reactors, (ML23269A222)
- NEI 21-07, Technology Inclusive Guidance for Non-Light Water Reactors - Safety Analysis Report: For Applications Utilizing the NEI 18-04 Methodology, Revision 1 (ML22060A190).
- NEI 18-04, Revision 1, Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development (ML22060A190)
- SECY-18-0096, Functional Containment Performance Criteria For Non-Light-Water-Reactors (ML18115A157)
- SECY-03-0047, Policy Issues Related to Licensing Non-Light-Water Reactor Designs (ML030160002)
- DANU-ISG-2022-01, Review of Risk-Informed, Technology-Inclusive Advanced Reactor Applications Roadmap (ML23277A139) 23
MHTGR
- The standard MHTGR consists of four identical reactor modules, each with a thermal output of 350 MWt, coupled with two steam turbine-generator sets to produce a total plant electrical output of 540 MWe. The reactors are helium cooled and graphite moderated and utilize ceramically coated particle type nuclear fuel. The design includes passive reactor-shutdown and decay-heat removal features.
- The MHTGR reference configuration was established by DOE after tradeoff evaluations that indicated the selection of (1) "prismatic" fuel blocks over pebble-bed spheres; (2) steel primary-system vessels over PCRVs; (3) modular-sized reactors over a larger, single reactor; and (4) separation of the reactor from the remainder of the primary-system components in a side-by-side design rather than the containment of all components "in-line" within a single vessel.
24
Xe-100 Functional Containment (SECY-18-0096) Functional containment: a barrier, or a set of barriers taken together, that effectively limits the physical transport of radioactive material to the environment.
Relevant phenomena are modeled mechanistically Multiple barriers between the UCO kernel and receptors of Interest X-energys XSTERM code is a suite of modules that model these phenomena in an integration manner Informed by RG 1.233 / NEI 18-04 implementation 25
© 2024 X Energy, LLC, all rights reserved 1
© 2024 X Energy LLC, all rights reserved 1
Xe-100 Principal Design Criteria (PDC) Licensing Topical Report (LTR)
August 21, 2024 Steve Vaughn, Director, Licensing Kyle Metzroth, Deputy Director, Xe-100 Systems Development X Energy, LLC
© 2024 X Energy, LLC, all rights reserved 2
Department of Energy Acknowledgement and Disclaimer This material is based upon work supported by the Department of Energy under Award Number DE-NE0009040.
This presentation was prepared as an account of work sponsored by an agency of the United States Government.
Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
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Agenda & Objectives Objectives:
Accurately communicate:
The Xe-100 PDC development process General differences from RG 1.232 guidance Example Xe-100 PDC that implement the NEI 18-04 methodology Respond to questions and comments from the ACRS Sub-committee Agenda:
Introductions/Opening Remarks Xe-100 PDC Development Process Xe-100 PDC:
General differences from RG 1.232 Example PDC Implementing the NEI 18-04 Methodology Questions/Closing Remarks
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Xe-100 PDC Development Process
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Xe-100 PDC Development Process
- RG 1.232 Guidance for Developing Principal Design Criteria for Non-LWRs
- NEI 21-07 and RG 1.253 Guidance for a Technology-Inclusive Content of Application Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light-Water Reactors
- DANU-ISG-2022-01 Review of Risk-Informed, Technology-Inclusive Advanced Reactor ApplicationsRoadmap
© 2024 X Energy, LLC, all rights reserved 6
Xe-100 PDC Development Process RG 1.232 Appendix C MHTGR-DC NEI 18-04 NEI 21-07 Xe-100 PDC
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Xe-100 PDC Development Process
- Added some definitions to expand on the NEI 18-04 terminology:
Function Design Criteria Required Safety Function (RSF)
Required Functional Design Criteria (RFDC)
Safety-Related Design Criteria (SRDC)
Non-Safety-Related with Special Treatment (NSRST) PRA Safety Function (PSF)
Complementary Design Criteria (CDC)
Non-Safety-Related with No Special Treatment (NST) PSF Owner-Controlled Design Criteria (OCDC)
© 2024 X Energy, LLC, all rights reserved 8
Xe-100 PDC:
General Differences from RG 1.232
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Xe-100 PDC l General Differences from RG 1.232
- Replaced important to safety with the NEI 18-04 definition of safety-significant
- Removed single failure criterion given NEI 18-04 leverages the defense-in-depth (DID) evaluation approach
- Replaced postulated accident and accident conditions with NEI 18-04 defined licensing basis event (LBE) terms (e.g., AOO, DBE, and DBA)
- Combined the language from MHTGR-DC 18, 32, 36, 37, 45, 46, and 72 into a single Xe-100 PDC 6 Monitoring, inspection, testing, surveillance
© 2024 X Energy, LLC, all rights reserved 10 Xe-100 PDC:
Example PDC Implementing the NEI 18-04 Methodology
© 2024 X Energy, LLC, all rights reserved 11 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- Combined PDC 11 Reactor inherent protection and PDC 12 Suppression of reactor power oscillations and decomposed a PDC-RFDC 11 and PDC-CDC 11
- PDC-RFDC 11 is one of the two means for supporting PDC-RFDC 26 Reactivity control systems
- Aligns with RSF 1.1.1 Control Reactivity with Inherent Reactivity Feedback
© 2024 X Energy, LLC, all rights reserved 12 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC 13 aligns with RSF 1.1.2 Control Reactivity with Moveable Poisons and RSF 1.3.1 Isolate Water/Steam Ingress
- PDC-CDC 13 aligns with NSRST PSF 1.1.2 Control Reactivity with Moveable Poisons, NSRST PSF 1.2.2 Control Heat Removal with Active Means, and NSRST PSF 2.5 Maintain HPB Pressure Integrity During Transients
© 2024 X Energy, LLC, all rights reserved 13 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-CDC 15 clarifies that the HPB design does not provide an RSF and therefore aligns with CDC not RFDC
- Aligns with NSRST PSF 2.7 Prevent Loss of HPB Integrity
© 2024 X Energy, LLC, all rights reserved 14 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC 16 describes the functional containment provided by the fuel particles and pebbles and PDC-CDC 16 describes the functional containment provided by the HPB
- Aligns with RSF 1 Retain Radionuclides in Fuel Particles and Pebbles and NSRST PSF 2 Retain Radionuclides in the HPB
© 2024 X Energy, LLC, all rights reserved 15 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC and PDC-CDC aligns with the Control Reactivity with Moveable Poisons RSF and NSRST PSF respectively
© 2024 X Energy, LLC, all rights reserved 16 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC 30 is focused on mitigating a steam generator tube rupture DBE and DBA and PDC-CDC 30 is focused on preventing helium leakage during AOOs
- PDC-RFDC 30 aligns with RSF1.3.1, Isolate Water/Steam Source and PDC-CDC 30 aligns with NSRST PSF 2.5, Maintain HPB Pressure Integrity During Transients
© 2024 X Energy, LLC, all rights reserved 17 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC 34 Residual heat removal provides a passive heat removal function while the PDC-CDC and PDC-OCDC provide an active heat removal function
- PDC-RFDC 34 aligns with RSF 1.2.1, Control Heat Removal Through Passive Means and PDC-CDC 34 aligns with NSRST PSF 1.2.2, Control Heat Removal with Active Means
© 2024 X Energy, LLC, all rights reserved 18 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC 70 Reactor vessel and reactor system structural design basis supports maintaining core geometry for passive heat removal and controlling reactivity
- PDC-RFDC 70 aligns with RSF 1.4.1, Maintain HPB and Core Geometry
© 2024 X Energy, LLC, all rights reserved 19 Example Xe-100 PDC Implementing the NEI 18-04 Methodology
- PDC-RFDC 71 Reactor building design basis structurally protects the reactor vessel and reactor system in support of maintaining core geometry for passive heat removal and controlling reactivity
- PDC-RFDC 71 aligns with RSF 1.4.2, Maintain Reactor Building Geometry
© 2024 X Energy, LLC, all rights reserved 20 End of Presentation Questions and Closing Remarks