ML20352A478

Transcript of the Advisory Committee on Reactor Safeguard 681st Full Committee Meeting - December 1, 2020, Pages 1-99 (Open)

ML20352A478
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Issue date:	12/01/2020
From:	Advisory Committee on Reactor Safeguards
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Burkhart, L, ACRS
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NRC-1258
Download: ML20352A478 (99)

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Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION

Title:

Advisory Committee on Reactor Safeguards Open Session Docket Number: (n/a)

Location: teleconference Date: Tuesday, December 1, 2020 Work Order No.: NRC-1258 Pages 1-59 NEAL R. GROSS AND CO., INC.

Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.

Washington, D.C. 20005 (202) 234-4433

1 1

2 3

4 DISCLAIMER 5

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

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

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

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

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

4 681ST MEETING 5 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 6 (ACRS) 7 + + + + +

8 OPEN SESSION 9 + + + + +

10 TUESDAY 11 DECEMBER 1, 2020 12 + + + + +

13 The Advisory Committee met via Video-14 Teleconference, at 2:00 p.m. EST, Matthew W. Sunseri, 15 Chairman, presiding.

16 17 COMMITTEE MEMBERS:

18 MATTHEW W. SUNSERI, Chairman 19 JOY L. REMPE, Vice Chairman 20 WALTER L. KIRCHNER, Member-at-large 21 RONALD G. BALLINGER, Member 22 DENNIS BLEY, Member 23 CHARLES H. BROWN, JR. Member 24 VESNA B. DIMITRIJEVIC, Member 25 JOSE MARCH-LEUBA, Member NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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2 1 DAVID A. PETTI, Member 2 PETER RICCARDELLA, Member 3

4 ACRS CONSULTANT:

5 MICHAEL CORRADINI 6 STEVE SCHULTZ 7

8 DESIGNATED FEDERAL OFFICIAL:

9 ZENA ABDULLAHI 10 11 ALSO PRESENT:

12 MICHAEL DUDEK, NRR 13 DAVID H. HINDS, GE-Hitachi 14 MARIELIZ JOHNSON, NRR 15 SCOTT MOORE, Executive Director, ACRS 16 NOLAN RYAN, NRR 17 GEORGE WADKINS, GE-Hitachi 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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3 1 AGENDA 2 Item Page 3 Opening Remarks by the ACRS Chairman . . . . . . 5 4 BWRX-300 Topical Report NEDC-33912, 5 Reactivity Control 6 Remarks from the Subcommittee Chairman . . . . 7 7 Presentation and discussion 8 NRC staff, Michael Dudek . . . . . . . . . . . 8 9 GE-Hitachi, George Wadkins and David Hinds . . 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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4 1 P R O C E E D I N G S 2 2:01 p.m.

3 CHAIR SUNSERI: Meeting will now come to 4 order. This is the first day of the 681st meeting of 5 the Advisory Committee on Reactor Safeguards.

6 I'm Matthew Sunseri, Chair of the ACRS.

7 And I now call the roll to confirm communications and 8 that a quorum exists. I'll start with Ron Ballinger.

9 Dennis Bley.

10 MEMBER BLEY: Here.

11 CHAIR SUNSERI: Charles Brown.

12 MEMBER BROWN: Here.

13 CHAIR SUNSERI: Vesna Dimitrijevic.

14 MEMBER DIMITRIJEVIC: Here.

15 CHAIR SUNSERI: Walt Kirchner.

16 MEMBER KIRCHNER: Here.

17 CHAIR SUNSERI: Jose March-Leuba.

18 MEMBER MARCH-LEUBA: Present.

19 CHAIR SUNSERI: Dave Petti.

20 MEMBER PETTI: Here.

21 CHAIR SUNSERI: Joy Rempe.

22 VICE CHAIR REMPE: Here.

23 CHAIR SUNSERI: Pete Riccardella.

24 MEMBER RICCARDELLA: I'm here.

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5 1 back. Ron Ballinger, have you joined us yet? Okay.

2 He was just on another line with us. I guess he'll 3 join shortly. But we do have a quorum. So we will 4 proceed on.

5 The ACRS was established by the Atomic 6 Energy Act and is governed by the Federal Advisory 7 Committee Act. The ACRS section of the U.S. NRC 8 public website provides information about the history 9 of the ACRS and provides documents such as our 10 charter, bylaws, Federal Register notices for 11 meetings, letter reports, and transcripts of all full 12 and subcommittee meetings, including slides presented 13 at the meetings.

14 The Committee provides its advice on 15 safety matters to the Commission through its publicly 16 available letter reports.

17 The Federal Register notice announcing 18 this meeting was published on November 20, 2020 and 19 provides an agenda and instructions for interested 20 parties to provide written documents or request 21 opportunities to address the Committee.

22 The Designated Federal Officer for this 23 meeting is Ms. Zena Abdullahi.

24 During today's meeting, the Committee will 25 consider the following, a BWRX-300 topical report on NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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6 1 reactivity control, and we will proceed into report 2 preparation if time permits.

3 A phone bridge line has been opened to 4 allow members of the public to listen in on the 5 presentation and Committee discussions. We have 6 received no written comments or requests to make oral 7 statements from members of the public regarding 8 today's session.

9 There will be an opportunity for public 10 comment. And we have set aside time in the agenda for 11 comments from members of the public attending or 12 listening to our meetings. Written comments may be 13 forwarded to Ms. Zena Abdullahi, the Designated 14 Federal Officer.

15 A transcript of the open portion of the 16 meeting is being kept. And it is requested that 17 speakers identify themselves and speak with sufficient 18 clarity and volume so that they may readily be heard.

19 Additionally, participants should mute themselves when 20 not speaking. And that's all.

21 So, as far as opening remarks, I really 22 don't have anything else to add. Our agenda is fairly 23 abbreviated for this session. Over the course of the 24 entire meeting, we will be looking at two letter 25 reports in preparation for our Commission briefing, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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7 1 along with a planning and procedure session.

2 So that's all I have for my opening 3 remarks. Any members care to make any statements 4 before we get into the agenda? All right. I'm not 5 hearing anything.

6 So our first topic is BWRX-300 topical 7 report. This session is characterized as open and 8 closed. And Dr. March-Leuba is our lead member on 9 this. And so I will turn it over to Jose at this 10 point.

11 MEMBER MARCH-LEUBA: Thanks, Mr. Chairman.

12 We are going to be listening about the reactivity 13 control design requirements in the topical report for 14 the BWRX-300 from GEH.

15 And before we start, I'd like to remind 16 the members that GEH has chosen to protect our 17 intellectual property. And there are many proprietary 18 issues on this topical report.

19 So, if the questions -- we have a closed 20 phone line that we can jump to if there are questions 21 that get into the proprietary nature. So, if I feel 22 that we are going that direction, I will use the magic 23 words of let's table this for the proprietary session, 24 the closed session, and please don't -- at that 25 moment, let's move to the closed session.

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8 1 That said, I want to thank both the staff 2 and GEH for making the extra work to make all the 3 presentations open so the public can learn about this 4 novel design.

5 And we, the Commission, or not the 6 Commission, the Committee heard about all the 7 proprietary and detailed information in the 8 subcommittee meeting just last month.

9 So, with that said, I believe the staff is 10 going to make the introductory remarks. So, Mike, are 11 you ready?

12 MR. DUDEK: I am. Thank you, Lead Person 13 March-Leuba and Chairman Sunseri and the rest of the 14 full Committee. Thank you for your time today.

15 On behalf of the staff, I'm just going to 16 give brief opening remarks on this third topical 17 report from GEH on reactivity control that requested 18 us to review their design requirements, analytical 19 methodology, acceptance criteria, and regulatory basis 20 associated with these reactivity control functions for 21 their small modular reactor design. As you stated, a 22 lot of this is proprietary and information that we 23 should protect.

24 This meeting comes off the heels of a very 25 successful subcommittee meeting. And I think that we NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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9 1 are prepared to discuss anything that you have or 2 answer any questions that you have.

3 So, without any further ado, I turn it 4 back over to you. And thank you guys, thank you, 5 Committee, for your time today.

6 MEMBER MARCH-LEUBA: Thanks, Mike. So 7 it's time for GEH to start their presentation.

8 MR. WADKINS: Thank you. This is George 9 Wadkins. I am the Vice President, New Power Plants 10 and Products Licensing for GE-Hitachi.

11 Today we will be presenting an overview of 12 the BWRX-300 small modular reactor design features for 13 reactivity control, including a brief description of 14 the content for licensing topical report NEDC-33912P, 15 BWRX-300 Reactivity Control.

16 As noted in our previous discussions with 17 the ACRS members, the BWRX-300 built upon our 18 extensive experience in boiling water reactor 19 technology, including our most recent experiences in 20 development and certification of the Economic 21 Simplified Boiling Water Reactor or ESBWR.

22 The BWRX-300 is the tenth generation of GE 23 boiling water reactors. And the BWRX-300 design 24 leverages the use of proven technology to the greatest 25 extent possible while incorporating advances in design NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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10 1 requirements and features to further enhance nuclear 2 safety and to provide for the protection of the public 3 in the unlikely event of an accident. Many of these 4 advances will be discussed today.

5 I first want to thank the NRC staff for 6 their in-depth review of this licensing topical 7 report. It is obvious to GE-Hitachi that the safety 8 review completed by the NRC staff was thorough and 9 focused on ensuring that the content of the licensing 10 topical report was complete, understandable, accurate, 11 and met the applicable regulatory requirements and 12 guidance.

13 As previously requested by the ACRS, we 14 are providing for an extensive open discussion of the 15 content of this licensing topical report. During our 16 presentation, we will pause at the end of each slide 17 to allow for questions from the ACRS members. But 18 please feel free to raise questions at any time.

19 If the discussions involve proprietary 20 information, then we will request tabling the question 21 until the latter closed session.

22 So, proceeding on to slide 2, the purpose 23 of today's presentation includes an overview of the 24 BWRX-300 design features involved in the mitigation of 25 licensing basis reactivity events.

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11 1 This includes how the BWRX-300 design 2 complies with the applicable regulatory requirements 3 and guidance and how the BWRX-300 design provides for 4 defense-in-depth shutdown capability and reactivity 5 control.

6 The licensing topical report addresses 7 design requirements, acceptance criteria, and 8 regulatory basis for the BWRX-300 reactor protection 9 system, or RPS for short, and other design features 10 for reactivity control and mitigation of anticipated 11 transients without scram, or ATWS for short.

12 I will now turn over the presentation to 13 David Hinds, principal design engineer for the BWRX-14 300, to discuss defense-in-depth design features for 15 BWRX-300.

16 MR. HINDS: Hello. This is David Hinds.

17 I will first check to ensure you can hear me.

18 MEMBER MARCH-LEUBA: We can hear you.

19 MR. HINDS: Okay. Thank you. All right.

20 So this is a very brief summary of our licensing 21 topical report. I'm trying to touch on technical and 22 the associated licensing input information.

23 And again, if there's detailed questions, 24 we'd be glad to take them. Some of them we may take 25 for the next session.

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12 1 So, in BWRX-300, we apply a very detailed 2 defense-in-depth approach to the design across the 3 board. And we base that upon the fundamentals of the 4 IAEA approach for defense-in-depth. We think it's 5 quite rigorous and easy for our engineering team to 6 follow and align to.

7 So we have applied that approach, which 8 uses a defense line approach such that it's very clear 9 as to where the layers of defense-in-depth are.

10 And for this discussion today and this 11 licensing topical report, we are focused on the 12 defense-in-depth approach associated with the 13 fundamental safety function of reactivity control.

14 Of course, we have defense-in-depth for 15 the other fundamental safety functions. But, again, 16 this is focused only on reactivity control today, 17 which is to ensure defense-in-depth for shutdown 18 capability and reactivity control. If you could, move 19 to the next slide, please.

20 So, in keeping with what I just stated 21 about our defense-in-depth approach, I'll walk briefly 22 through our defense lines.

23 We begin with defense line 1. And defense 24 line 1 is the fundamental design approach where we do, 25 we apply a high level of quality and reliability and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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13 1 conservatism into the design.

2 And some of those design approaches that 3 we use for defense line 1 help to reduce challenges to 4 the plant from a trip perspective, reduces the trips 5 per year, reduces the numbers of AOOs. We use a very 6 rigorous operating experience review approach.

7 And as George stated, since this is the 8 tenth generation of our boiling water reactors, we 9 have a long lineage of operating experience to draw 10 from to build upon and continuous improvement. Next 11 slide, please.

12 Just to highlight a few of the associated 13 design features in the plant associated with 14 reactivity control, we'll start right at the basics of 15 control rods.

16 So our control rods -- and, of course, 17 this is not to scale. Our control rods that we're 18 using have a long period of operating experience.

19 We're using control rods that are already receiving 20 operating experience in the current fleet of boiling 21 water reactors.

22 And this is just showing a visual for 23 anyone that's not used to looking at the figures, and 24 on the right, just shows a visual of how the control 25 rod fits in a control cell or fuel cell with four fuel NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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14 1 bundles surrounding the control rod blade.

2 So it is a proven design, a high level of 3 reliability. And we have even, in addition to the 4 high reliability that we're currently achieving with 5 our control rods, we have done some additional things 6 (audio interference) for the blades, the control rod 7 blades.

8 We've applied a, what we call an in-9 lattice core such that we have a slightly larger water 10 gap there for the control rod blades to travel between 11 fuel assemblies, helping to minimize any potential for 12 binding or prevention of movement of the rods upon 13 demand. So we've slightly increased the pitch from 14 fuel bundle to fuel bundle, gives plenty of margin for 15 control rod movement.

16 We're also using advancements in the fuel 17 channels that helps to minimize any chance of 18 deformation of fuel channels. We are collecting 19 operating experience on those channels today. We have 20 no evidence of shadow corrosion on those NSF type 21 channels that we're using.

22 And these, this type of design, it also 23 helps ensure we have a very high degree of shutdown 24 margin as well. Can you move to the next slide, 25 please?

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15 1 So, just touching on some of the 2 associated regulations, and then I'll continue through 3 the defense lines as well. So 50.62, 10 CFR 50.62 was 4 one of the regulations that was addressed in the 5 licensing topical report.

6 In that regulation, one of the explicit 7 requirements is for alternate rod insertion system.

8 And we do have the ARI system, which we have 9 experience with on our current operating fleet.

10 And in the slide here, I have the brief 11 summary of the hydraulic scram function or hydraulic 12 ability to insert the control rods.

13 So our control rods are driven on the 14 BWRX-300 by fine motion control rod drives. Our older 15 plants have hydraulic only or locking piston control 16 rod drives.

17 The BWRX-300, just like the ABWR and 18 ESBWR, apply a newer design, which also has operating 19 experience of fine motion control rod drives. They 20 have motors to, electric motors to provide the normal 21 control rod movement in both directions, insert and 22 withdraw, for very small and fine motion. That's for 23 normal power control and also serves as a backup to 24 hydraulics for quick shutdown.

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16 1 unlike the current operating fleet of only hydraulic, 2 the hydraulics on this design, as water hydraulics, 3 are only there for the purpose of fast shutdown, i.e.,

4 scram.

5 So we use pressurized water in 6 accumulators, stored energy. Many of you, if not all 7 of you, are probably quite familiar with the operating 8 fleet of the HCUs.

9 So we have redundancy by providing 10 hydraulic control units. Two control rods are aligned 11 to each HCU. We have, the HCUs are actuated by a 12 reactor protection system. And in the BWRX-300, we 13 also have a diverse means.

14 Then, we additionally have a ARI function 15 that will depressurize the scram air header if 16 necessary to provide further backup for insertion or 17 reactor scram if needed.

18 So this is somewhat of a busy slide. But 19 it's somewhat busy because we have many ways to get to 20 the control rods. And so I'll run back through again, 21 because I maybe jumped around a little.

22 Control rods normally inserted and 23 withdrawn by electric motors through the fine motion 24 control rod drives. They're inserted with hydraulics 25 for fast shutdown in a scram. The hydraulics are NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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17 1 actuated by our reactor protection system. And 2 there's also a diverse means to actuate them.

3 In addition to those two means to actuate 4 the hydraulic control units, if there's a common cause 5 failure of hydraulic control unit actuation, there's 6 a diverse ARI, depressurization to cause the scram as 7 well.

8 So that's basically three ways to get the 9 hydraulics and the electric motors, also in addition 10 to their normal power control, can provide a backup to 11 insertion during the case of a failed scram. So 12 that's a little, brief summary of a little complicated 13 discussion.

14 But in addition, at the very bottom of 15 this slide, for those who are quite familiar with the 16 operating fleet hydraulics, one of the possible, not 17 likely but possible, failure modes was hydraulic lock 18 of the scram discharge volume.

19 I'll note that on this design we've 20 additionally incorporated a way to remove the scram 21 discharge volume. And it's just a one-way insertion 22 of hydraulics. Okay. If we could, move to the next 23 slide, please.

24 MEMBER MARCH-LEUBA: Jose. By that, you 25 mean instead of discharging into, a dedicated volume NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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18 1 will discharge into the vessel, correct?

2 MR. HINDS: That is correct. Okay. I'll 3 keep on moving. And I'll be glad to take questions 4 any time.

5 So defense line 2 is -- so defense line 1 6 is more programmatic and fundamental features and 7 design decisions, such as the in-lattice.

8 Once we get into defense line 2, 3, and 4, 9 we have systems and features that may actuate or 10 control to improve safety of the plant or to respond 11 to an event.

12 And defense line 2, that includes 13 functions that normally control the plant, such as 14 pressure control, water level control, things, rod 15 control, normal control features of the plant.

16 And we have a high level of quality 17 applied to defense line 2 than just plain non-safety 18 equipment, but not to the pedigree of the full safety-19 related or safety class 1 equipment. However, it does 20 have enhanced quality and reliability features applied 21 to the design and the procurement.

22 The defense line 2 is, includes functions 23 to control or stop postulated initiating events. You 24 know, I mentioned pressure control and level control, 25 key features in control of the plant.

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19 1 So the quality that we place and the 2 redundancy that we place into these systems minimizes 3 postulated initiating events that could challenge the 4 safety class 1 or safety-related systems that will be 5 in defense line 3 as I get to that.

6 Defense line 2 is independent from defense 7 line 3 all the way through, provides a high 8 reliability and, again, reduces the challenges to the 9 plant from a trip perspective. If you could, go to 10 the next slide, please.

11 Here's another design feature just 12 highlighting, of course, the reactor pressure vessel.

13 Just to, there are many things to talk about on the 14 reactor pressure vessel, but I'll only highlight a 15 couple of them.

16 One is, this is a natural circulating 17 boiling water reactor similar to the ESBWR but smaller 18 in size. So we took ESBWR concept, and we scaled it 19 to a nominal 300-megawatt electric power plant.

20 However, many of the features that come 21 with natural circulation are quite helpful in 22 mitigating events.

23 So the part I'll highlight here is large 24 steam volume. It's a higher volume to power ratio as 25 compared to, for example, the ESBWR. So the high NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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20 1 volume to power ratio minimizes any pressurization 2 transients.

3 However, in part of our defense line 1 4 design decisions, we added conservatism in. Even 5 though we have that larger volume to power ratio, we 6 have chosen to raise the design pressure from our 7 historical values such that we have additional margin 8 in the design pressure of the reactor vessel, and we 9 have a higher volume to power ratio. So, therefore, 10 the pressurization transients are not a challenge for 11 this plant.

12 And we've already gone through a previous 13 LTR, as listed here, for the reactor pressure vessel 14 isolation and overpressure protection. However, that 15 overpressure or that volume to power ratio and the 16 minimization of pressurization helps also in 17 reactivity abnormal events such as a slow or failed 18 scram. Okay. If you could, go to the next slide, 19 please.

20 Defense line 3 is the heart of safety.

21 That's our highest safety class right in the middle of 22 our defense-in-depth and posture. So safety class 1 23 or safety-related systems reside in defense line 3.

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21 1 placed in a safe condition, assigned the highest 2 safety class. And we ensure that we have independence 3 from defense line 2, and for that matter, independence 4 from defense line 4 as well.

5 MEMBER MARCH-LEUBA: Dave, this 6 independence from DL 2, is there going to, do you --

7 obviously, you have the final design. But you won't 8 have any detailed communications between the control 9 system and the protection system, DL 2 and DL 3?

10 MR. HINDS: They are separate digital 11 control systems. The only potential would be for 12 protected communication, for example, one-way 13 information sharing, but not -- there will be 14 protected communications, if any. They are completely 15 separate systems.

16 MEMBER MARCH-LEUBA: Most likely, I would 17 imagine, the communication will go from DL 3, if a 18 scram happens, and you pass it to the control system.

19 MR. HINDS: Yes.

20 MEMBER MARCH-LEUBA: And those should be 21 unidirectional.

22 MR. HINDS: Yes.

23 MEMBER MARCH-LEUBA: And when we review 24 the details, we are going to be very interested on the 25 architecture and make sure that those unidirectional NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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22 1 communications are really unidirectional.

2 MR. HINDS: I understand.

3 MEMBER MARCH-LEUBA: Okay.

4 MEMBER BROWN: By that he means not 5 software configured. This is Charlie.

6 MR. HINDS: Okay. I understand.

7 MEMBER BROWN: Hardware, data diode type, 8 one way, not configured by software.

9 MR. HINDS: Okay. I understand. And 10 we'll have, for any license submittal, we would go 11 into, of course, great detail on the I&C architecture 12 and address those features. But I understand your 13 comments. Thank you.

14 MEMBER BROWN: And I presume that will be 15 covered in the, when we finally get to a reactor 16 protection system topical report or whatever you're 17 going to issue for that, will provide that as well as 18 the information of how you intend to achieve, not the 19 detailed parts, obviously, but the architecture 20 approach --

21 MR. HINDS: Yes, for future licensing 22 submittals, yes. Now, there's further decisions to be 23 made as to whether they would be under a licensing 24 topical report or under an actual application. But, 25 yes, I agree with your statement.

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23 1 MEMBER BROWN: Okay. That's fine. I just 2 wondered where it's going to be, because, I mean, when 3 I went through the other, these other documents, so 4 far there's -- you talk about the RPS as an RPS and 5 you say what it's going to do, but there's no other 6 details. That's all.

7 MR. HINDS: That is correct. Your review 8 is correct. So I agree with your statements.

9 MEMBER BROWN: Okay. Thank you.

10 MR. HINDS: Okay. If you could, move to 11 the next slide, please.

12 Okay. One of the key systems within the 13 highest of safety classes, in addition to the reactor 14 protection system, is the isolation condenser system.

15 So I mentioned that the RPV itself has 16 certain pressure mitigating features by its volume to 17 power ratio. However, the pressure control is 18 primarily at least in the safety class 1. In an event 19 where we have an isolation, we use an isolation 20 condenser system.

21 We inherited the design from ESBWR as far 22 as the condensers themselves. We are applying three 23 trains of the same size of condensers that we applied 24 on ESBWR.

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24 1 plant, we have a very large margin and significant 2 capacity for minimizing any pressurization transients 3 and controlling any challenge to pressurization by use 4 of the isolation condenser system.

5 It primarily operates in a passive mode.

6 This is a very simplified figure that doesn't show the 7 valves. There are valves in here.

8 But all it takes to actuate the system is 9 the opening of one valve in the return line, the 10 condensate return line to the vessel. And there are 11 parallel, diverse means in that condensate return line 12 to actuate. And in the worst case, if we were to lose 13 all power and signal, it fails in the in-service 14 condition.

15 And again, there's redundancy here as well 16 with a very simple actuating system. Once placed in 17 service, it stays in service and requires no support 18 features once placed in service.

19 Again, there's three trains. We have them 20 as a staggered operating points for the automatic 21 initiations on pressure such that they don't all come 22 into service at the same time. But in a severe event 23 where, such as a complete failure to scram, we would 24 expect to hit all three and use them to mitigate the 25 event.

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25 1 Again, failsafe, simple system. And 2 again, we drew upon the program from ESBWR, which 3 included a full-scale test of these isolation 4 condensers. And we also covered this design feature 5 in our previous LTR for overpressure protection as 6 well.

7 MEMBER MARCH-LEUBA: Dave, this is Jose 8 again. Typically when we do these things, we have 9 competing requirements. From the thermal-hydraulic 10 point of view, it's super exciting to have extra 11 capacity because you can cool down better. You can 12 cool down more and you can cool down with failures.

13 From the criticality safety point of view, 14 you can bring the core to cold. And I'm going to ask 15 you to remind us that no matter how cold the core 16 gets, even with two blades stuck out, you are not 17 going to return to power. That's your requirement, is 18 that correct?

19 MR. HINDS: That's correct. We, as I've 20 mentioned before when I was talking about the 21 hydraulic control units, we have one hydraulic control 22 unit aligned to two control rod drives. And we assume 23 a failure of one of those hydraulic control units and 24 still have adequate shutdown margin.

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26 1 I think we'll be fine with more than that. However, 2 that's what our analyzed state is, is two stuck-out 3 control rods with ample shutdown margin.

4 MEMBER MARCH-LEUBA: And you plan to do 5 this with all three ICS running at full blast and 6 making the core as cold as it can possibly get?

7 MR. HINDS: Yes, within reason, yes. So 8 yes, agree with your statement.

9 MEMBER MARCH-LEUBA: Thank you.

10 MR. HINDS: So we do have, you know, 11 temperature extremes on our analysis. I think that's 12 permanently addressing your point. And I'll note that 13 we do include some design enhancements from the ESBWR.

14 To get into details on those, if you're interested in 15 getting that level of detail, we'd prefer to discuss 16 that in the closed session.

17 But it does help with, I'll just simply 18 state that those design enhancements improve the 19 pressure control while helping with the reactivity 20 control. So this system helps with pressure control 21 while at the same time assisting with reactivity 22 control. Okay, if we could go to the next slide, 23 please.

24 MEMBER KIRCHNER: David, this is Walt 25 Kirchner. So going back to your statement, you NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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27 1 mentioned there's defense line 3 is the highest 2 quality class, I'm -- or safety class. I just assume 3 that the reaction coolant pressure boundary as 4 illustrated in this diagram then would also be of the 5 highest quality.

6 MR. HINDS: That's correct.

7 MEMBER KIRCHNER: Safety-related if you're 8 using 10 CFR 50 or 52 definitions.

9 MR. HINDS: Yes, that is correct. And 10 we've applied --

11 MEMBER KIRCHNER: Thank you.

12 MR. HINDS: We've applied the IAEA 13 approach, we've been using terminology of safety class 14 I, II, and III. But I agree with your statement. And 15 so this system is a safety class I or safety-related 16 system highest safety class, that's correct.

17 MEMBER BLEY: David, this is Dennis Bley.

18 I want to go back to what Jose was talking about. And 19 I don't think it's for this current report, but later 20 when we get to this design cert review, you mentioned 21 that the intent is to have maximum ICS occur.

22 You know, in the past, at least in some 23 places, people have worried that that was too much and 24 developed thoughts about how to cut it back, which can 25 lead to significant problems. We'll be interested in NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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28 1 discussing that when we get into details, that system.

2 MR. HINDS: Okay, thank you. And the part 3 when I mentioned, alluded to some design enhancements, 4 and I'll be glad to discuss a little further in a 5 closed session, will help with your question as well.

6 So I understand your question. And that staggered set 7 point that I mentioned earlier, that also helps with 8 your question as well. But I understand it.

9 So we have evaluated inadvertent IC 10 actuation as part of our standard suite of analysis, 11 and so I understand. Okay.

12 MR. SCHULTZ: Dave, Steve Schultz. In the 13 system that you've described, the return valves fail 14 open, and also they're -- the system is failsafe.

15 With regard to operator action, any operator actions 16 that are proposed or could take place that would close 17 those valves?

18 MR. HINDS: No, the operator is not --

19 okay so I think you asked that, I'll address your 20 question in two ways, and hopefully one way will 21 answer you. It is one is that the system completely 22 actuates without operator action. I think the other 23 side of your question is could the operator cause a 24 problem by disabling the safety function.

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29 1 ensure that the proper human factors, of course there 2 will be operators and the operators will be expected 3 to be aware of this situation and monitor. Part of 4 our human factors design will take into account the 5 human reliability analysis and potential that an 6 operator could disable a safety function.

7 And our intent that we're still working 8 through is that that would not occur. It is an 9 automated system and so I do not think that's 10 difficult to achieve.

11 MR. SCHULTZ: Good, thank you.

12 MR. HINDS: Okay, thank you. If we could 13 move to the next slide, please. Okay, so now we're up 14 to the backup defense behind the safety-related 15 systems, which should hopefully never be called upon.

16 So, defense line 4-alpha, and we've take the IAEA 17 defense lines 4 and split to 4-alpha and -bravo.

18 Won't talk much about 4-bravo, it's more like the flex 19 or deep defense-in-depth.

20 But in the defense line 4-alpha, we have 21 functions to mitigate the postulated initiating event, 22 similar to the goals of defense line 3, but it's in a 23 backup way. And this is there to mitigate times when 24 defense line 3 or the safety-related systems are 25 called upon and experience a common cause failure.

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30 1 They're ensured -- they also ensure that the plant is 2 placed in a safe state.

3 If you go to the next slide, please.

4 MEMBER MARCH-LEUBA: Dave, go back to this 5 slide.

6 MR. HINDS: Sure.

7 MEMBER MARCH-LEUBA: And have you ever 8 seen a non-proprietary setting, an example so we can 9 think what you're --

10 MR. HINDS: Yes.

11 MEMBER MARCH-LEUBA: We can focus on what 12 you're talking about?

13 MR. HINDS: Certainly, ARI. So I touched 14 on, because I talked about many features of the 15 control rod movement in an earlier slide, I hit may 16 defense lines. So I hope I didn't confuse things 17 there, I was worried about that slide.

18 So with the control rod insertion, I hit 19 many defense lines there. If you remember, there's 20 many ways to insert the control rods. So an example 21 of the defense line 4-alpha method to insert the 22 control rods is the ARI. And then there's some others 23 where we would get a little further into proprietary.

24 But, and I'll be glad to discuss further. But that's 25 an example, ARI, alternate rod insertion.

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31 1 MEMBER MARCH-LEUBA: Okay, I'll make a 2 note to ask you in the closed session, because I'm 3 interested. Is this defense-in-depth actions going to 4 be performed by a non-safety-grade computer?

5 MR. HINDS: They are a lower safety class 6 than what in the US we'd call safety-related.

7 However, we are applying the IAEA approach, so it's 8 not just taken all the way back to what you would 9 think of non-safety as a graded approach to quality.

10 So we've applied a safety class II, which a not all 11 the way to the level of safety-related, but not all 12 the way down to the level of non-safety-related and 13 augmented quality.

14 MEMBER MARCH-LEUBA: So in I&C lingo, it 15 will be redundant but not diverse?

16 MR. HINDS: This platform in defense line 17 4 is diverse from defense line 3.

18 MEMBER MARCH-LEUBA: All right, but within 19 itself, it will be more than one channel, hopefully 20 three. But they will all be the same type of 21 computer.

22 MR. HINDS: Correct, this is appropriate 23 level of redundancy, but it could be all the same, it 24 could be all the same technology within the 25 redundancy.

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32 1 MEMBER MARCH-LEUBA: Okay, thank you.

2 We'll look at those details with the next --

3 MR. HINDS: Okay.

4 MEMBER MARCH-LEUBA: Yes, I'm sure.

5 MR. HINDS: Okay, thank you. All right, 6 next slide please. Okay, just a little bit into --

7 further into the ATWS rule, 50.62. These are -- this 8 is really a restatement of ATWS rule, which I'm sure 9 you're well aware of. So, but only pulling out the 10 portions of the ATWS rule 50.62 which apply to boiling 11 water reactors specifically, ARI, SLC, and automatic 12 recirc pump trip. Can you go to the next slide 13 please.

14 Okay, as far as going through those 15 features. So automatic recirc pump trip. As I stated 16 earlier, this is a natural circulating power plant, so 17 therefore the automatic recirc pump trip is deemed to 18 be not technical relevant in that we do not have 19 recirc pumps to trip, so therefore we do not include 20 a recirc pump trip feature.

21 However, the purpose of the recirc pump 22 trip is to minimize a reactivity in the case of a 23 failure to scram, and we do have other features to 24 minimize reactivity in a similar fashion.

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33 1 within the reactor, and the enhancements that I 2 mentioned for the isolation condenser system that I 3 can discuss further in the closed session help in this 4 respect as well. We, the feedwater system is 5 controlled as well to minimize reactivity effects.

6 Okay, if we could go to the next slide, please.

7 So the SRP, we just stayed a little bit 8 out of the SRP, and I'm sure the NRC will cover this 9 further, so I'll go over it very quickly, is the SRP 10 related to 15.8, related to the ATWS rule. And there 11 is a statement in there, in the SRP, that talking 12 about evolutionary plants, which we think the BWRX-300 13 is an evolutionary plant.

14 And it says that you could have a diverse 15 scram system and satisfying design and quality 16 assurance criteria. And/or you could demonstrate the 17 consequences of the ATWS event or within acceptable 18 values.

19 In keeping with our defense-in-depth 20 approach, we've addressed both of these so we do have 21 a diverse means of shutdown, the details of which I've 22 kind of alluded to at a very high level, but I can 23 talk a little further in the closed session. But we 24 do have a diverse means to shut down. I talked about 25 it a little bit in a very high level in the prior NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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34 1 slides. We do have ARI and we do have electric motors 2 to move the control rods that are in addition to the 3 normal hydraulic scram.

4 I've listed there, a little bit to the 5 question a minute ago, where ARI and electric motor 6 run-in are included in defense line 4-alpha. And 7 there's multiple defense lines that are ensuring the 8 hydraulic insertion occurs as well in defense line 2, 9 3, and 4-alpha.

10 MEMBER BROWN: Does the next -- this is 11 Charlie Brown.

12 MR. HINDS: Yes.

13 MEMBER BROWN: Does the fine motor control 14 drive, is that able to insert rods at a fast enough 15 speed to handle the reactivity transience? Is that --

16 it's intended to do that as well?

17 MR. HINDS: Yes. So it's -- great 18 question. It's, during normal operation, we want the 19 fine movement to minimize the reactivity effects at 20 high power, for example. However, the speed is 21 calibrated such that we have an insertion capability 22 that is fast enough to handle the complete failure of 23 all of the other means to get the control rods in.

24 So if all of those other means that I 25 discussed on the hydraulic actuation, as well as the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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35 1 ARI, all of them fail, the control rod insertion by 2 motors is fast enough. And that's coupling that with 3 the pressure control features of the isolation 4 condenser system that I just talked about earlier. So 5 short answer is yes, it is fast enough.

6 MEMBER BROWN: Is, does that -- based on 7 your comments, does that mean it has more than one 8 speed? In other words, for insertion it can go faster 9 than you would -- than you would necessarily for your 10 fine motion control during normal operations?

11 MR. HINDS: We're actually still working 12 on whether we're going to adjust the speed any during 13 normal operation, but we do have this setting for the 14 rapid insertion, as we discussed here. We're planning 15 to use servomotors, which have a capability to move at 16 variable speeds. So it's likely that we will have a 17 slower speed during high power operation, but we're 18 still working through making that decision. But it's 19 an excellent question.

20 MEMBER BROWN: Okay, thank you.

21 MR. HINDS: Okay, if we can move to the 22 next slide please, I'll try to wrap up.

23 MEMBER MARCH-LEUBA: While we're on the 24 open session, let me just say that we, ACRS, are going 25 to be terribly interested. I know you, the design NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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36 1 team, has spent a lot of time thinking about ATWS and 2 during the review, both the staff and ACRS are going 3 to be very interested in this topic when you have the 4 final design and the final calculations to ensure that 5 nothing can go wrong. Just putting it on the record, 6 and we'll talk more about this in the closed session.

7 MR. HINDS: Okay, all right, understand.

8 So just a brief summary here, don't -- hopefully don't 9 need to go into much detail. But here's the listing 10 of regulatory acceptance criteria, all pulled from 11 regulations. So I don't think any, should be any 12 surprises here. So we have pressure requirements, 13 fuel integrity, containment integrity, rad release, 14 and ensuring that shutdown and long-term cooling are 15 all evaluated and analyzed.

16 Okay, if no questions there, I'll keep on 17 moving and trying to keep the time moving. Okay, and 18 so I think this is the last slide in this --

19 MEMBER BROWN: Sir, can I ask one other 20 question? I kind of forgot.

21 MR. HINDS: Sure.

22 MEMBER BROWN: You mentioned this as back 23 on the speed of the time motion motor controls.

24 MR. HINDS: Yes.

25 MEMBER BROWN: You mentioned that that was NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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37 1 going to be servos.

2 MR. HINDS: That's our intent, yes.

3 MEMBER BROWN: Okay. And --

4 MR. HINDS: We do have some options there 5 where we have some motors that we've used previously 6 that are stepper motors and we have some motors we've 7 used previously that are induction. But our current 8 preference is servos. We've not procured them yet, so 9 there is a chance that that would change, but our 10 current intent is servomotors.

11 MEMBER BROWN: The reason I ask is that 12 servomotors don't always have the same torque 13 characteristics that an induction motor or even a step 14 motor. I'm familiar with both the step motors, I had 15 rod control systems that were step motors in my old 16 plants in the Navy, in one of the design plants. And 17 the motor control were basically reluctance motors, 18 which you could control and make sure they had enough 19 torque.

20 But servomotors don't always have a lot of 21 torque since they're pretty fine control type devices.

22 That was my only question is are those really 23 satisfactory for a higher speed type insertion where 24 you might need to generate some additional torque.

25 That's the only thought process I had.

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38 1 MR. HINDS: Yes, we have applied torque 2 specifications to our motor supplier and not had any 3 problem to date with aligning to get a supplier for 4 that. But I agree with your focus on that topic. We 5 do not think we'll have a problem meeting it.

6 MEMBER BROWN: Okay.

7 MR. HINDS: But again, we do have further 8 work to be done and through the procurement cycle, but 9 we do have a supplier that we think can meet our 10 requirements there on torque.

11 MEMBER BROWN: Okay, thank you.

12 MR. HINDS: Okay.

13 MEMBER MARCH-LEUBA: The rules of the game 14 -- this is Jose -- the rules of the game is, we don't 15 design the reactor for you, but in my opinion, I would 16 go for the highest torque, the biggest force you can 17 have on that FMC, I mean, the fine motion control rod 18 drive, the electric motors. So that even if there is 19 some binding, you can push the rod in. And I can 20 control the velocity by stepping it slowly with a step 21 motor.

22 Just think about it. I mean, the safest 23 thing is to have the high -- the biggest motor you can 24 find that will push the rod in no matter what. And --

25 okay, that's it. I'm not helping you design your NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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39 1 reactor, but just giving you some hints.

2 MR. HINDS: Okay. Okay, thank you for the 3 comment, I understand the nature of it. Thank you.

4 So the final slide here in this segment is 5 we did highlight another one of the regulations, the 6 GDC 27, and we just highlight it here because we go 7 through in the LTR and evaluate all the appropriate 8 GDCs and regulatory documents associated with 9 reactivity control. And I'll highlight this one in 10 addition to the ATWS rule, just because we had an 11 alternate means of compliance or actually an 12 exception.

13 And it's primarily just the wording of the 14 GDC and that the GDC is, so you can see above, the 15 reactivity control system shall be designed to have a 16 combined capability in conjunction with poise and 17 addition by ECCS of reliability, the reliability 18 controlling reactivity changes to assure under 19 postulated access. Anyway, you can read it.

20 We changed the words but meet the intent, 21 just because the words didn't explicitly align with 22 our design since we are, as stated in our prior 23 submitted LTR and reviewed LTR on the RPV isolation 24 and overpressure protection. We do not rely upon ECCS 25 injection systems and associated borated coolant.

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40 1 And therefore the wording of this did not 2 explicitly apply, so we've reworded it but still meet 3 the intent such that core coolability is maintained 4 for a locus. Because we have sufficient water 5 inventory, and we're assuring that through the RPV 6 isolation. So we preserve the coolant and we do not 7 have a borated solution and there's no concern with 8 ECCS injection diluting a borated system and causing 9 a reactivity excursion.

10 So this -- I think, we feel like was 11 written for different type designs, and so we've 12 applied a PDC to substitute for the GDC, and that's an 13 exception stated in the LTR.

14 MEMBER BROWN: Presume when you do your 15 submittals in whatever form they are, they will 16 somehow address the fact whether the plant will be 17 able to be shut down under all temperature conditions, 18 the sub-critical as opposed to perking along at low 19 power for weeks?

20 MR. HINDS: Yes, and as I stated before, 21 as we do our shutdown margin calculations with the two 22 highest worth control rods associated with an HCU 23 fully withdrawn and we have ample shutdown margin.

24 And we also have a temperature range which we apply to 25 that, and so I think we will not have a problem NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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41 1 meeting the point that you're alluding to.

2 MEMBER BROWN: Okay, thank you.

3 MR. HINDS: Okay. That's it for the slide 4 presentation, and I think I've exceeded my time, I'm 5 sorry.

6 MEMBER MARCH-LEUBA: Well, you did good.

7 Just as a reminder to the members, we are going to 8 have an open presentation by the staff, and then we 9 are going to go to the closed session to see some 10 details of calculations by GEH. And we have plenty of 11 time.

12 Our plan is to read the letter, the ACRS 13 letter in the open session, so we will have the staff 14 present open session here. We will all, that are 15 allowed to, move to the closed session to see those 16 calculations, and then we'll come back to the open 17 session to read the letter.

18 And on that line, GE, Zena is going to 19 send you the final copy of the letter, because we've 20 made some modifications based on members' inputs. And 21 if you could give it a quick read to make sure the 22 modifications did not put any proprietary information 23 on it, we would appreciate it. And we have to do it 24 real fast.

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42 1 please.

2 MR. NOLAN: Okay, thank you. This is Ryan 3 Nolan. I'm in the Nuclear Methods and Systems and New 4 Reactors Branch in NRR, and I'll be presenting the 5 staff's presentation for our review of the BWRX-300 6 reactivity control topical report. And I will be 7 assisted by Marieliz Johnson, who is helping me with 8 the slides today. Marieliz, you can go to the next 9 slide.

10 So here's an outline of the presentation 11 today. We'll quickly go through the review team, a 12 little bit of background on the BWRX-300. The bulk of 13 the presentation will focus on the staff's review of 14 specific regulatory requirements, and we'll wrap up 15 with the conclusion.

16 These slides are very similar to what you 17 saw in the subcommittee meeting. However, I plan on 18 just touching the highlights and not going into the 19 full detail that we did in the subcommittee meeting.

20 However, if there are questions we can certainly go 21 into more details. Next slide, Marieliz.

22 So this is just to present the review 23 team, many of which are here to support, answer any 24 questions that I cannot. So with that, you can move 25 to the next slide, Marieliz.

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43 1 So a quick background. BWRX-300, it's a 2 300-megawatt electric SMR. It's natural circulation, 3 uses a passive cooling isolation condenser. The 4 control rods are typical BWR control rods that we're 5 all familiar with.

6 This design does include some defense-in-7 depth and diverse features with respect to reactivity 8 control for ensuring the reactor is properly 9 controlled and shut down. And this topical report 10 goes through specific requirements, design 11 requirements, as well as assesses regulatory 12 requirements specific to reactivity control functions.

13 Next slide, Marieliz.

14 So here's a short list of the specific 15 design features that are included, or and systems that 16 are included in the BWRX-300 design. I'll just 17 briefly step through each one. The control rod system 18 is made up of control rods, we've already talked about 19 them, GE provided a good overview, as well as control 20 rod drives.

21 The drives are split up into the safety-22 related rapid insertion function that's performed 23 hydraulically, as well as a non-safety-related fine 24 motion control function that uses electric motors and 25 is used for normal operation as well as a scram NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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44 1 follow-up function as a backup means.

2 Also, there's an alternate rod insertion 3 system. This provides a diverse means of a hydraulic 4 scram in the event of an HCU failure. And it uses 5 energized to actuate pilot valves. And so it's an 6 alternate means to vent the control air. Next slide, 7 Marieliz.

8 This is a list of the regulations that we 9 addressed in the safety evaluation. I'm going to go 10 through each. I'll go through the ATWS rule first, 11 and then I will go through each of the GDCs that's 12 underlined. I do not have specific slides on the GDCs 13 which are not underlined. This is mainly due to the 14 means for the requirements or design requirements on 15 certain systems for meeting these requirements are 16 fairly traditional and straightforward.

17 And so just at a high level, the GDCs 18 which are not underlined, the staff found that the 19 approaches described in the topical report were 20 consistent with the associated GDCs, and we found 21 those to be acceptable. So with that, we'll talk 22 about 50.62 on the next slide. Marieliz.

23 So the topical report defines the 24 acceptance criteria for evaluating the effectiveness 25 of the reactivity control systems and functions. It's NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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45 1 listed here on this slide. These are consistent with 2 the SRP, as well as it's consistent with the 3 acceptance criteria that the operating fleet has used 4 to evaluate the ATWS transients. Next slide, 5 Marieliz.

6 So first, specific requirement for 50.62 7 related to BWRs is C3. This requires all BWRs to have 8 an alternate rod insertion system that's diverse from 9 the reactor trip system. This is fairly 10 straightforward because the BWRX-300 uses a fairly 11 traditional ARI system. They commit to having one, 12 and so the staff found that that approach is 13 acceptable and consistent with the requirement. Next 14 slide.

15 50.62(c)(4) requires BWRs to have a 16 standby liquid control for injection into the vessel.

17 The topical report specifies that the design will meet 18 the risk goals for 50.62, which is a probability of an 19 ATWS is less than one times ten to the minus five per 20 reactor year. This is achieved through diverse scram 21 actuation logic, diverse rod motor force, as well as 22 a couple other things that is proprietary.

23 The staff found that this risk goal is 24 consistent with the intent of 50.62, and this could be 25 used as -- to support a future exemption if so NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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46 1 desired. We did write a limitation and condition on 2 this, next slide. We wrote several limitations and 3 conditions in certain areas where the topical report 4 maybe didn't go into a lot of detail as what type of 5 analysis will be performed in the future.

6 And so we just wanted to clarify some of 7 the staff's expectations or what we would expect to 8 demonstrate some of the statements that were included 9 in the topical report. So specific to ATWS, we have 10 a limitation and condition to provide a reliability 11 analysis that takes into account operating experience 12 in order to demonstrate that the probability of an 13 ATWS is less that one times ten to the minus five per 14 reactor year, demonstrating the intent of the rule is 15 satisfied.

16 50.62(c)(5) requires BWRs to automatically 17 trip the recirculation pumps under ATWS conditions.

18 This one as well is fairly straightforward. It's not 19 applicable to the BWRX-300 because it is a natural 20 circulation -- a plant does not have recirc pumps.

21 And so this regulation is not applicable to the BWRX-22 300. However, the design does have compensating 23 measures, which is proprietary, and we did discuss at 24 the subcommittee meeting. Next slide.

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47 1 the general design criteria. The first one is GDC 12, 2 which requires control and protection systems to 3 ensure that oscillations that could exceed the SAFDLs 4 are prevented or they're detected and suppressed.

5 The topical report specifies that the 6 BWRX-300 will meet GDC 12 through several design 7 features, some of which are included here, which is a 8 small core, sort of a newer of form of orifice design, 9 a coupled power to flow response, as well as the 10 design of the RPB chimney. We wrote a limitation 11 condition on this as well. Next slide.

12 And this is really just to ensure that the 13 analysis which demonstrates some of the statements 14 made in the topical report is performed using an 15 approved method. And that's really the intent of this 16 limitation condition, is to make sure that there is an 17 appropriate analysis to demonstrate GDC 12 is met.

18 MEMBER MARCH-LEUBA: Ryan, this is Jose.

19 We talked about some of this in the subcommittee.

20 When we say approved method, do we need to have a 21 topical report that says NRC approves it for use in 22 the BWRX-300? Or an approved method for ESBWR is 23 acceptable? Or does it need to be extended? Can you 24 talk a little bit about approved methods?

25 MR. NOLAN: Yeah, yeah, we did talk about NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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48 1 it a little internally as well, just briefly. And 2 there needs to be demonstration that the topical 3 report is applicable to the BWRX-300. I think there's 4 some flexibility in how that's done. Traditionally 5 that is done through topical reports.

6 But I think the staff is open and is 7 flexible to how that is documented. So I think at a 8 minimum it needs to be documented somewhere.

9 Traditionally it's the topical report, but it probably 10 doesn't have to be.

11 MEMBER MARCH-LEUBA: Okay, so we'll 12 revisit this in the future, and it's for GEH and the 13 staff to negotiate what will be acceptable. Clearly, 14 I think we all agree, even GEH, that the 15 recommendation needs to be performed. And the 16 question is how we do it with minimal pain. Okay, 17 thank you.

18 MR. NOLAN: Certainly. Next slide. So 19 GDC 26, it requires two independent reactivity control 20 systems based on different design principles. The 21 topical report specifies that the BWRX-300 will meet 22 the GDC by providing control rods, which is used for 23 normal operations including AOOs and addresses 24 malfunctions, as well as holding the reactor 25 subcritical under cold conditions.

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49 1 And then the feedwater level control 2 system is used to satisfy bravo above, which, you 3 know, is used to adjust the reactivity control during 4 planned and normal power outages. And this of course 5 is something that we will review obviously in more 6 detail once we get an application. But as described 7 in the topical report, it is consistent, the approach 8 is consistent with GDC 26.

9 So GDC 27, the intent of the GDC is to 10 require reactor designs to achieve and maintain 11 subcriticality, and this is using only safety-related 12 equipment following accidents, as well as addressing, 13 taking into account single failures. And as was 14 discussed by GEH in their presentation, they proposed 15 a PDC.

16 It maintains fundamentally all of the same 17 information that is in the GDC, with a focus of just 18 satisfying the intent of that regulation. And as was 19 discussed already, the BWRX-300 will use the control 20 rods to ensure that the reactor remains subcritical 21 under cold conditions.

22 We do expect to see an analysis in the 23 future which would demonstrate this. That analysis 24 would look at both, you know, instantaneous shutdown 25 margin, as well as, you know, a long-term shutdown NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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50 1 margin, which would account for, you know, any 2 cooldown from the isolation condensers.

3 MEMBER KIRCHNER: So Ryan, this is Walt 4 Kirchner. Just a process question. So they are 5 proposing a PDC in lieu of the GDC, and then in the 6 actual review of an application, then this would 7 require a formal exemption.

8 MR. NOLAN: That's correct. I think, you 9 know, as we, you know, we've been reviewing some 10 interesting designs recently and some exemptions are 11 maybe more administrative in nature and less 12 technical, and perhaps this would fall into that 13 category.

14 So technically from a legal perspective, 15 yes, it would require an exemption. However, I don't 16 think it raises any substantial technical issues or 17 concerns at this point. It's more just a matter of 18 documenting it.

19 MEMBER KIRCHNER: Yeah, and analysis will 20 demonstrate that they have the rod work necessary to 21 keep it shut down as in subcritical through a range of 22 conditions. And it's been brought up earlier, you 23 know, obviously it's the temperature, it's the 24 cooldown that would be something to look at in the 25 future.

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51 1 Okay, I'm just checking how you're doing 2 this now. And then this would be consistent with the 3 requirements also of 10 CFR 50 or 52 then in terms of 4 a safe shutdown condition.

5 MR. NOLAN: That's correct.

6 MEMBER KIRCHNER: Yeah. I noticed that 7 the GE used the, I think it's the IAEA language, they 8 talked about a safe state. But I suspect for the 9 staff, you would be looking for what's required as for 10 10 CFR 50 or 52.

11 MR. NOLAN: That's correct. And we 12 documented in our safety evaluation specifically the 13 interpretation that the staff has on GDC 27. And that 14 was pulled from the recent SECY paper that we wrote 15 where we specifically state the intent is, and it's a 16 first bullet here, you know, the intent is to maintain 17 long-term subcriticality using only safety-related 18 equipment.

19 MEMBER KIRCHNER: Excellent, thank you.

20 MR. NOLAN: Yup. Next slide. So GDC 28 21 requires that reactivity control systems be designed 22 with appropriate limits on the amount and rate of 23 reactivity increase to ensure that reactivity 24 accidents can neither damage the reactor pressure 25 boundary or disrupt the core or the internal NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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52 1 structures to a point where it impairs significantly 2 the capability to cool the core.

3 These types of events are called out 4 specifically in GDC 28. Some of them include, you 5 know, rod ejection, rod dropout, things of that 6 nature. The topical report states that the BWRX-300 7 will meet GDC 28, and this is through a series of 8 design features of the control rod drive system in its 9 ability to limit the rate and amount of reactivity 10 increase, as well as a safety analysis which 11 demonstrates compliance with the requirement.

12 And so this analysis would look at control 13 rod drop accidents, and in the topical report GE has 14 committed to using, you know, existing approved 15 methodologies to perform that analysis. It's a 16 similar analysis which was performed for the ESBWR.

17 And so the staff found this approach to be consistent 18 with the GDC.

19 This is the final limitation and condition 20 specific to a control rod drop accident. Again, this 21 is really to document the staff's expectation that 22 this analysis be performed using design-basis 23 assumptions, as well as using approved methods. And 24 we tried to write some flexibility into this condition 25 as well.

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53 1 And so we provided also another option if 2 GE wants to go a different route that they could 3 demonstrate perhaps that the control rod accident is 4 a beyond-design-basis event and do a sort of a 5 different type of analysis and include that into 6 Chapter 19. Versus a, you know, more of a traditional 7 transient accident analysis, what we typically would 8 refer to as a Chapter 15 analysis.

9 And so that was just to establish sort of 10 expectations and provide some flexibility for the 11 future.

12 MEMBER MARCH-LEUBA: Is there a real need 13 to do that? I mean, we have all the methodology and 14 GEH knows how to do the rod drop calculations on a 15 cycle-specific basis. It doesn't save any money, it 16 doesn't make anything easier to try to change what 17 we're doing. In my opinion, yes, continue to do what 18 you're doing for operating reactors, which is every 19 cycle, just analyze the rod drop and do it.

20 MEMBER KIRCHNER: Yeah, just to add to 21 what Jose's saying, I would expect they're all -- that 22 the applicant, or GEH in particular here, I mean, 23 they're well experienced and must be totally up to 24 date on DG 1327, I don't remember what it now is as a 25 final reg guide, as Jose suggests. So it would seem NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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54 1 to me that the path forward for expediting one's way 2 through the licensing review would be to stick with 3 the current rod drop analyses.

4 MR. NOLAN: Yes, I think the staff would 5 find that acceptable. The reason this is here is 6 really rooted in the way the original topical report 7 described this analysis, as well as some of the RAI 8 responses. And so we wanted to just be very clear of 9 what our expectation was that it be a design-basis 10 safety analysis, as well as I think GE proposes a one-11 time analysis to bound cycle-by-cycle variations.

12 But we wanted to clarify that it doesn't 13 have to do that. And I think we felt that this 14 condition provided that flexibility and clarification 15 that we needed to make the finding from a compliance 16 perspective.

17 MEMBER MARCH-LEUBA: I agree with you, 18 Ryan, that either way it satisfies regulations. But 19 the path of least resistance is do the calculation and 20 recycle. You know how to do it. It doesn't -- maybe 21 we'll GE in the closed session, but I don't think it 22 adds that much cost to the -- I would keep doing what 23 has worked for 60 years, and that's my personal 24 opinion. Thank you.

25 MR. NOLAN: Yup, and that's what we're NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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55 1 trying to communicate here. We would certainly find 2 the traditional approach acceptable. Next slide, 3 Marieliz. Yeah.

4 So to conclude here, taking into account 5 the limitations in conditions, the topical report 6 provides an acceptable description of the 7 requirements, the acceptance criteria, and the 8 regulatory basis for the design feature specific to 9 the reactivity control functions for the BWRX-300.

10 And just as a disclaimer, we don't have 11 the application in front of us at this time, we don't 12 have the detailed design in front of us. And we will 13 evaluate full regulatory compliance at the time that 14 that application or other future licensing activities 15 are submitted to the staff. If an applicant can't 16 demonstrate compliance, you know, we do expect them to 17 justify an exemption to a regulation.

18 And with that, that concludes my 19 presentation.

20 MEMBER MARCH-LEUBA: Great. Do we have 21 any questions for the staff in the open session? And 22 just a reminder, there's going to a GEH closed session 23 presentation, and there will not be a staff closed 24 session presentation, but they will be able to answer 25 questions if necessary.

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56 1 So any questions?

2 MEMBER KIRCHNER: Jose, this is Walt 3 again. This is not a question, maybe a statement.

4 I'm just thinking about the fine motion control rod 5 drives and the discussion we had. If indeed they wind 6 up down the road designing that system such that it 7 has one speed for normal rod withdrawal during normal 8 operation and a different speed for insertion, then 9 one -- just I'm thinking aloud a little bit here --

10 then one worries that there's the potential for the 11 system to not operate, function correctly and run the 12 rods out at the higher motor speed or however they 13 design it.

14 I'm, just an observation, something to 15 look at down the road when there's an actual design, 16 a detailed design.

17 MEMBER MARCH-LEUBA: We would be very 18 interested on that. But my suspicion is that the rod 19 ejection would be faster than the speed the motor can 20 move at. But and I will bound it.

21 MEMBER KIRCHNER: I agree, that would 22 likely bound it, you know, the traditional ejection or 23 drop in this case.

24 MEMBER MARCH-LEUBA: Yes. Okay, can we 25 open the public line please? For comments? Is the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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57 1 public phone line open for comments? Is anybody on 2 the public phone there, can you please say hello? I 3 don't hear anybody. So if there is anybody in the 4 public line that wants to make a comment, please state 5 your name and do the comment.

6 We'll leave the public line open for a 7 moment longer, and I'm going to ask the members if 8 anybody wants to make a statement around the table.

9 Remember that we will come back to the open line this 10 session to read the letter. But if you want to make 11 a comment on the record right now, that will be the 12 time.

13 Seeing no feedback, we are going to 14 temporarily recess this meeting, and we are going to 15 move to the closed team meeting, the closed phone line 16 to get the proprietary information. Everybody knows 17 that? Yes, sir.

18 CHAIR SUNSERI: No, I'm sorry, when you're 19 done, I had a question. I wanted to ask you about 20 timing and things.

21 MEMBER MARCH-LEUBA: Comment, go ahead, 22 I'm done.

23 CHAIR SUNSERI: Okay, so we're going to 24 recess here and go to closed session. I'm going to 25 suggest we take a 20-minute break and reconvene the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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58 1 closed session at 20 minutes before the hour, so 2 that'd be 3:40. How long do you think that closed 3 session is going to last? And I know it's just a 4 slag, but do you have an idea? Because we should give 5 the public an ideal of when we would return to the 6 open session approximately, so.

7 MEMBER MARCH-LEUBA: I believe, let me 8 make sure, --

9 CHAIR SUNSERI: Why don't we just say 10 4:30?

11 MEMBER MARCH-LEUBA: GE has provided 20 12 slides, but if we -- and I assume Charlie Hicks is 13 going to be doing it, okay, he likes to talk even more 14 than I do. But we can do -- let me make an executive 15 decision. We'll be back in the open line no earlier 16 than 4:30.

17 CHAIR SUNSERI: Okay.

18 MEMBER MARCH-LEUBA: That will give us --

19 CHAIR SUNSERI: Yeah, that's fine. That's 20 fine. That's good enough. And then we can have staff 21 monitor the 4:30 open line and let people --

22 (Simultaneous speaking.)

23 CHAIR SUNSERI: Yeah, okay, thank you.

24 MEMBER MARCH-LEUBA: So we are on recess, 25 and we will see everybody on the -- everybody that is NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.

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59 1 allowed to be in the closed line at 3:40, that's 20 2 minutes from now.

3 CHAIR SUNSERI: Thank you.

4 MEMBER MARCH-LEUBA: So we are off the 5 open line record. We will still have a transcription 6 of the closed session at 3:40. We are on recess.

7 (Whereupon, the above-entitled matter went 8 off the record at 3:19 p.m.)

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GE-Hitachi Nuclear Energy Michelle P. Catts GE-Hitachi Nuclear Energy Americas, LLC Senior Vice President, Nuclear Programs P.O. Box 780, M/C A-18 Wilmington, NC 28402 USA T 910.200.9836 Michelle.catts@ge.com M200153 November 24, 2020 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555-0001

Subject:

Submittal of ACRS Full Committee Presentation Slides for NEDC-33912P, BWRX-300 Reactivity Control Licensing Topical Report Enclosed are the final presentation slides for use during the upcoming Advisory Committee on Reactor Safeguards (ACRS) GE-Hitachi Nuclear Energy Americas, LLC (GEH) Full Committee Meeting on December 1, 2020. This supports the ACRS review involving NEDC-33912P, BWRX-300 Reactivity Control, Revision 0, Supplement 1, and the corresponding NRC Advanced Safety Evaluation Report (SER) with No Open Items. contains non-proprietary information and may be made available to the public.

If you have any questions, please contact me at 910-200-9836.

Sincerely, Michelle P. Catts Senior Vice President, Nuclear Programs GE-Hitachi Nuclear Energy Americas, LLC

Enclosure:

1. ACRS Full Committee Presentation Slides for NEDC-33912P, BWRX-300 Reactivity Control Licensing Topical Report - Non-Proprietary Information cc: R Franovich, US NRC Document Components:

001 M200153 Cover Letter.pdf 002 M200153 Enclosure 1 Non-Proprietary.pdf

ENCLOSURE 1 M200153 ACRS Full Committee Presentation Slides for NEDC-33912P, BWRX-300 Reactivity Control Licensing Topical Report Non-Proprietary Information

ACRS Full Committee Presentation GEHitachi (GEH)

Licensing Topical Report (LTR) NEDC33912P BWRX300 Reactivity Control (Open Session)

December 1, 2020

Purpose of ACRS Full Committee Presentation

• Describe Design Features to Meet Regulatory Requirements and Provide DefenseinDepth for Licensing Basis Reactivity Events

• Address design requirements, acceptance criteria, and regulatory basis for the BWRX300 Reactor Protection System (RPS) and other associated means for:

- Reactivity Control

- Anticipated Transients Without Scram (ATWS)

• Provide the design requirements, acceptance criteria, and regulatory basis for the BWRX300 mitigating systems associated with an ATWS Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 2

DefenseinDepth Design Features for BWRX300 Reactivity Control

DefenseinDepth Design for BWRX300 BWRX300 applies a defenseindepth approach aligned with IAEA guidance

• Address Fundamental Safety Functions to ensure overall plant safety

• Assigns BWRX300 functions to Defense Lines associated with Fundamental Safety Functions

• This LTR is focused on the Fundamental Safety Function of Reactivity Control that ensures defenseindepth shutdown capability and reactivity control Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 4

DefenseinDepth - Defense Line 1 IAEA Defense Line 1:

Level 1

• Reduce challenges to the Reactor Protection System (RPS) from all occurrences Defense Line 1 (DL1)

- Fewer trips per year

- Reduces number of Anticipated Operational Occurrences (AOOs)

• Reduced challenges to RPS

• Some transients become Infrequent Events defined as < 1 per 100 Reactoryears

• Strengthen subsequent Defense Lines

- Quality

- Reliability

- Conservatism Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 5

BWRX300 Reactor Pressure Vessel (RPV)

• Large RPV steam volume results in lower pressurization rate for isolation events (compared to ABWR and existing BWRs) resulting in less reactivity effect

• Refer to NEDC33910P, BWRX300 Reactor Pressure Vessel Isolation and Overpressure Protection Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 6

DefenseinDepth - Defense Line 2 IAEA Defense Line 2:

Level 2

• Includes functions which normally control the plant

- Rod control and control of power generation systems Defense Line 2 (DL2)

• Plant functions designed to control or stop a Postulated Initiating Event (PIE)

• Minimizes PIEs that reach DL3 setpoints thereby reducing challenges to DL3 systems

• Independent from DL3

- Includes diverse means of shutdown

• Provides high reliability of plant control Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 7

BWRX300 Control Rod with Fuel Assemblies Proven BWR operating fleet Control Rod design Increased clearance for control blades Positioned by Fine Motion Control Rod Drives (FMCRDs)

Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 8

DefenseinDepth - Defense Line 3 IAEA Defense Line 3:

Level 3

• Includes functions which act to mitigate a PIE

- Isolation Condenser System (ICS)

Defense Line 3 (DL3)

• Ensure plant is placed in a safe state

- Reactor Protection System (RPS) Scram

• Assigned to highest safety class

• Independent of DL2 Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 9

Isolation Condenser System (ICS)

• Heat exchanger design and capacity of each ICS train is the same as ESBWR

• Total % heat removal capacity from ICS larger than ESBWR

• Failsafe, simple system

• Limits reactor pressure and temperature and maintains reactor water inventory

• Condensate return valves (not shown) fail open on loss of power to the valves

• Condensate return well above the core

• ICS design enhancements provides pressure control and assists in power reduction Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 10

DefenseinDepth - Defense Line 4a IAEA Defense Line 4a:

Level 4

• Includes functions to mitigate a PIE along with failure of DL3

• Mitigates CCFs in DL3 Defense Line 4a (DL4a)

- Alternate Rod Insertion (ARI) - provides hydraulic scram in event of Hydraulic Control Unit (HCU) actuation failure

- FMCRD insertion with motors

• Ensures plant is placed in a safe state Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 11

Design Features Required by ATWS Rule 10 CFR 50.62 mandates reduction of risk from an ATWS 10 CFR 50.62(c)(3), (4) and(5) require the following design features for BWRs:

• ARI System

• Automatic Standby Liquid Control System (SLCS)

• Automatic Recirculation Pump Trip Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 12

10 CFR 50.62(c)(3) - Alternate Rod Insertion (ARI) System

• Each control rod can be inserted hydraulically using stored highpressure water from hydraulic control unit (HCU) accumulators by either:

- RPS and diverse actuated scram solenoid valves removing control air to each HCU

- Diverse ARI pilot valves removing control air to scram solenoid valves for all HCUs

• Fine Motion Control Rod Drives (FMCRDs) have electricmotordriven positioning used for both insertion and withdrawal of control rods

• Electricmotordriven positioning diverse from hydraulic scram

- Allows rod movement, even with failure of ARI System

- Utilize sensors and logic that are diverse and independent of RPS

• Common cause failure (CCF) of hydraulic scram caused by scram discharge volume used in older designs is eliminated

- Scram discharge fluid goes into Reactor Pressure Vessel Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 13

10 CFR 50.62(c)(5) - Automatic Recirculation Pump Trip Forced circulation BWRs trip recirculation pumps to reduce core flow and power:

BWRX300 utilizes natural circulation and has no recirculation pumps BWRX300 design incorporates:

• Control of power generation systems to assist in mitigation

• Reduction of water level, core flow and reactor power in a similar manner as recirculation pump trip in a forced circulation plant Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 14

Design Features Described in Standard Review Plan (SRP)

NUREG0800, SRP 15.8, states:

A. For evolutionary plants where the ATWS rule does not explicitly require a diverse scram system, the applicant may provide either of the following:

i. A diverse scram system satisfying the design and quality assurance criteria specified in SRP Section 7.2 ii. Demonstrate that the consequences of an ATWS event are within acceptable values BWRX300 meets both requirements for an AOO with failure to scram

• Alternate means for shutdown

• ARI and electric motor runin included in DL4a

• Successful shutdown ensured by DL2, DL3, DL4a

• Consequences of failure to scram from normal and diverse means mitigated by use of DL4a Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 15

Regulatory Acceptance Criteria

• Primary System Maximum primary stress within Reactor Coolant Pressure Boundary (RCPB) does not exceed the emergency limits as defined in the ASME B&PV Code,Section III

• Fuel Integrity Cladding temperature and oxidation criteria of 10 CFR 50.46 met

• Containment Integrity Maximum containment pressure does not exceed the design pressure

• Radiological Releases Maintained within 10 CFR 100 allowable limit

• Shutdown and Cooling Reactor is brought to longterm shutdown with continued effective core cooling Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 16

10 CFR Part 50, Appendix A, GDC 27

• 10 CFR Part 50, Appendix A, GDC 27, Combined Reactivity Control Systems Capability The reactivity control systems shall be designed to have a combined capability, in conjunction with poison addition by the emergency core cooling system, of reliably controlling reactivity changes to assure that under postulated accident conditions and with appropriate margin for stuck rods, the capability to cool the core is maintained

-Exception Core coolability is maintained for lossofcoolant accidents because loss of water inventory in the RPV is minimized by the assured function of RPV isolation valves to mitigate large line breaks Refer to NEDC33910P, BWRX300 Reactor Pressure Vessel Isolation and Overpressure Protection Copyright 2020 GE Hitachi Nuclear Energy Americas, LLC - All Rights Reserved 17

NRC Staff Presentation-GEH Topical Report NEDC-33912P, Revision 0, Supplement 1, BWRX-300 Reactivity Control BWRX-300 Small Modular Reactor ACRS Full Committee Meeting December 1, 2020

Presentation Outline

• NRC Staff Review Team

• BWRX-300 Background

• NRC Staff Review of NEDC-33912P

• Conclusion 2

NRC Staff Review Team

• NRR Nuclear Methods, Systems, and New Reactors Branch (SNRB)

Ryan Nolan Andrew Proffitt Alex Siwy

• NRR PRA Licensing Branch C (APLC)

Anne-Marie Grady Alissa Neuhausen

• NRR Instrumentation and Controls Branch A (EICA)

Dinesh Taneja

• NRR New Reactor Licensing Branch (NRLB)

Rani Franovich 3

BWRX-300 Background

• 300 megawatt electric small modular reactor

• Uses natural circulation and passive cooling isolation condenser system Based on ESBWR design

• Uses typical boiling-water reactor bottom-entry, cruciform-shaped control rods

• Includes defense-in-depth and diverse features to ensure the capability to shut down and control the reactor

• NEDC-33912P specifies design requirements and assesses regulatory requirements related to reactivity control 4

BWRX-300 Reactivity Control Systems and Functions NEDC-33912P specifies design requirements for:

• Rod control system

• Reactor protection system

• (( ))

• Alternate rod insertion

• (( ))

5

Evaluation of Applicable Regulations

• 10 CFR 50.62, Requirements for reduction of risk from ATWS events

• 10 CFR 50, Appendix A, General Design Criteria GDC 12, Suppression of reactor power oscillations GDC 20, Protection system functions GDC 21, Protection system reliability and testability GDC 22, Protection system independence GDC 23, Protection system failure modes GDC 24, Separation of protection and control systems GDC 25, Protection system requirements for reactivity control malfunctions GDC 26, Reactivity control system redundancy and capability GDC 27, Combined reactivity control systems capability GDC 28, Reactivity limits GDC 29, Protection against anticipated operational occurrences 6

Evaluation of Applicable Regulations:

10 CFR 50.62

• NEDC-33912P, Section 3.7.1 defines the ATWS acceptance criteria for evaluating the effectiveness of the reactivity control diverse shutdown means:

RCS and main steam pressure below 120% design Peak cladding temp. and oxidation within 10 CFR 50.46 limits Peak containment pressure/temp. below design Coolable geometry Radiological doses are maintained within 10 CFR 100 limits

• Consistent with SRP Section 15.8, Anticipated Transients Without Scram.

7

Evaluation of Applicable Regulations:

10 CFR 50.62(c)(3)

• Requires BWRs to have an ARI system diverse from the reactor trip system.

• The BWRX-300 includes an ARI system for diverse depressurization of the scram air header and will meet the requirement of 50.62(c)(3).

8

Evaluation of Applicable Regulations:

10 CFR 50.62(c)(4)

• Requires BWRs to have a standby liquid control system (SLCS) for injection into the vessel.

• NEDC-33912P specifies the BWRX-300 will meet the risk goals of 10 CFR 50.62 for P(ATWS) less than 1x10-5 per reactor year (( )).

Diverse scram actuation logic Diverse rod motive force

(( ))

• This risk goal is consistent with the intent of 10 CFR 50.62 (( ))

• Limitation and Condition 5.1 9

Evaluation of Applicable Regulations:

10 CFR 50.62(c)(4)

Limitation and Condition 5.1:

Any applicant referencing NEDC-33912P must perform and document:

• Reliability analysis or testing, considering applicable operating experience and expected load follow conditions, of the BWRX-300 diverse scram features to demonstrate the probability of an ATWS is less than 1x10-5 per reactor year (( )).

10

Evaluation of Applicable Regulations 10 CFR 50.62(c)(5)

• Requires BWRs to automatically trip the recirculation pumps under ATWS conditions.

• This requirement is not applicable to the natural circulation BWRX-300.

11

Evaluation of Applicable Regulations:

General Design Criterion 12

• Requires control and protection systems to ensure power oscillations that could exceed the SAFDLs are prevented or detected and suppressed.

• NEDC-33912P states the BWRX-300 will meet GDC 12 and maintains margin to instability through:

small core and orifice design coupled power-flow response RPV chimney

• Limitation and Condition 5.3 12

Evaluation of Applicable Regulations:

General Design Criterion 12 Limitation and Condition 5.3:

Any applicant referencing NEDC-33912P must perform and document:

• A stability analysis in accordance with an approved methodology to demonstrate that the BWRX-300 maintains a coupled power-flow response such that any operational perturbation, maneuver, or AOO that does not cause an immediate scram is naturally damped and decays quickly to steady state for all modes of operation; prevents SAFDLs from being exceeded; is not susceptible to regional or radial modes of oscillation; and includes necessary provisions to address cycle-specific conditions.

13

Evaluation of Applicable Regulations:

General Design Criterion 26

• Requires two independent reactivity control systems of different design principles a) The first must use control rods and is used for normal operation, including AOOs, with margin for malfunctions b) The second must reliably control reactivity changes resulting from planned, normal power changes c) One system must be capable of holding the reactor subcritical under cold conditions

• NEDC-33912P states that the BWRX-300 will meet GDC 26 by providing:

Control rods (satisfy a and c above)

Feedwater level control system at power, other means to adjust level in other modes (satisfies b above)

• NRC staff finds this approach consistent with GDC 26 14

Evaluation of Applicable Regulations:

General Design Criterion 27

• The intent of GDC 27 is to require reactor designs to achieve and maintain long-term subcriticality using only safety-related equipment following a postulated accident with margin for stuck control rods.

• NEDC-33912 proposes the following principal design criterion (PDC) in lieu of GDC 27:

The BWRX-300 reactivity control system shall be designed to have the capability of reliably controlling reactivity changes to assure that under postulated accident conditions and with appropriate margin for stuck rods the capability to cool the core is maintained.

• BWRX-300 control blades will be capable of holding the reactor subcritical under cold conditions assuming failure of the highest worth control rod pair.

• Analysis that demonstrates the control rod system is sufficient for achieving and maintaining shutdown margin could justify an exemption to GDC 27 and the use of the design-specific PDC.

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Evaluation of Applicable Regulations:

General Design Criterion 28

• Requires reactivity control systems be designed with appropriate limits on the potential amount and rate of reactivity increase to assure that postulated reactivity accidents can neither:

1) result in damage to reactor pressure boundary greater than limited local yielding

2) sufficiently disturb the core, its support structures or other reactor pressure vessel internals to impair significantly the capability to cool the core.

• Reactivity accidents that must be considered:

Rod ejection (unless prevented by positive means), rod dropout, steam line rupture, changes in coolant temperature/pressure, and cold water addition

• NEDC-33912P states that the BWRX-300 will meet GDC 28 by:

Design features of CRD system and rod control system limiting the amount and rate of reactivity increase Safety analyses demonstrating compliance submitted in future licensing activities o Including analysis of CRDA event using approved methodology (NEDE-33885P-A)

• NRC staff finds this approach consistent with GDC 28 16

Evaluation of Applicable Regulations:

General Design Criterion 28 Limitation and Condition 5.2:

Any applicant referencing NEDC-33912P must perform and document:

• A CRDA design-basis safety analysis applied to an equilibrium cycle in accordance with an approved methodology, providing justification for any deviations (e.g., performing a one-time analysis to bound cycle-by-cycle variations), or request an exemption to justify the CRDA as a beyond-design-basis event and document the CRDA analysis results in the probabilistic risk assessment.

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Conclusion

• With specified Limitations and Conditions, NEDC-33912P provides an acceptable description of design requirements, acceptance criteria, and regulatory bases for design features of the BWRX-300 reactivity control functions.

• Detailed design of BWRX-300 SMR is not complete.

If applicant is not able to demonstrate compliance with NRC regulations, the applicant will be expected to justify an exemption from the applicable requirement.

NRC staff will evaluate regulatory compliance of the final BWRX-300 design with regards to reactivity control during future licensing activities for BWRX-300 applications.

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Questions?

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