ML20343A272

M201204B: Transcript - Meeting with the Advisory Committee on Reactor Safeguards

ML20343A272
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Issue date:	12/04/2020
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1 UNITED STATES NUCLEAR REGULATORY COMMISSION

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PUBLIC MEETING WITH THE ADVISORY COMMITTEE ON REACTOR SAFEGUARDS

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FRIDAY, DECEMBER 4, 2020

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The Commission met in the Commissioners' Hearing Room at the Nuclear Regulatory Commission, One White Flint North, 11555 Rockville Pike, at 10:00 a.m.,

Kristine L. Svinicki, Chairman, presiding.

COMMISSION MEMBERS:

KRISTINE L. SVINICKI, Chairman JEFF BARAN, Commissioner ANNIE CAPUTO, Commissioner DAVID A. WRIGHT, Commissioner CHRISTOPHER T. HANSON, Commissioner ALSO PRESENT:

ANNETTE VIETTI-COOK, Secretary of the Commission MARIAM ZOBLER, General Counsel

2 ACRS MEMBERS: (attending via video conference)

MATTHEW SUNSERI, Chair JOY REMPE, Vice Chair CHARLES BROWN WALTER KIRCHNER DENNIS BLEY JOSE MARCH-LEUBA RONALD BALLINGER VESNA B. DIMITRIJEVIC DAVID A. PETTI PETER RICCARDELLA

3 P-R-O-C-E-E-D-I-N-G-S 1

10:01 a.m.

2 CHAIRMAN SVINICKI: And now I will open 3

and convene our meeting this morning of the Commission 4

with the Advisory Committee on Reactor Safeguards.

5 Gather at NRC are the members of the Commission, 6

representative of OGC and of the Office of the 7

Secretary.

8 All members of the ACRS will be 9

participating remotely in todays meeting. Again, 10 appreciate very much all members of the Commission for 11 the flexibility, we had to stay very adaptive through 12 out the course of the public health emergency. Im 13 also gratefully that the members of the Advisory 14 Committee and Reactor Safeguards have made provisions 15 to participate in todays meeting. This is very 16 important engagement. I think of course the Commission 17 is in receipt of the letter reports of the ACRS 18 throughout the year on any number of important topics 19 mandated under the Atomic Energy Act and then other 20 matters that the Committee takes up in its own 21 discretion or just because they have been consistent 22 thorny technical issues that the agency have been 23 working through for a number of years like digital 24 instrumentation and control. So it is particularly 25

4 of great utility to members of the Commission to have 1

an opportunity to engage the ACRS to explore further 2

understanding of their consensus letter reports and 3

they are Committee that works by consensus but also 4

to have a chance to pursue topics if we should choose 5

outside of the current letter reports and issues the 6

Committee is working on.

7 So we will hear from Matthew Sunseri, 8

Chairman of the ACRS. We will hear from member 9

Kirchner. Also, from the Vice-Chairman, Joy Rempe and 10 from member Charles Brown.

11 I understand that other members of the ACRS 12 who traditionally in a physical meeting here would have 13 been at least available for questions, have two-way 14 communication for the purposes of today's meeting.

15 Although it's not very routine for other members of 16 the Committee to be called to answer questions. I just 17 want to make my colleagues aware that they stand in 18 that capacity ready to answer questions. So your 19 questions do not need to be limited to the members who 20 will be giving the formal presentations.

21 Before I start, would any member of the 22 Commission like to add anything?

23 Okay, hearing none, then I will begin by 24 turning over to the current Chairman of the ACRS, Matt 25

5 Sunseri. And I think the booth will help us pulling 1

him up. Oh, wonderful.

2 Okay, great, thank you. Please proceed 3

ACRS CHAIR SUNSERI: Good morning, 4

Chairman, good morning, Commissioners. I'm Matthew 5

Sunseri, Chairman of the Advisory Committee on Reactor 6

Safeguards.

7 It's a pleasure to be here with you today 8

to conduct this briefing. I know from previous 9

experiences that the members consider this to be a very 10 valuable experience, and we look forward to it and we 11 hope you do as well.

12 Slide 2 please. Our agenda is as follows.

13 I will be providing a general overview of activities 14 that we have completed since our last briefing with 15 you. Including our review of two subsequent license 16 renewals and an update on our transformation 17 activities.

18 Dr. Walt Kirchner, our Member-at-Large, 19 will be presenting a summary of our review of the NuScale 20 design certification application.

21 Dr. Joy Rempe, our Vice Chairman, will be 22 discussing our evaluation of NRC safety research 23 activities.

24 And lastly, Member Charles Brown will be 25

6 providing a

report on a

couple of digital 1

instrumentation and control activities that we have 2

reviewed.

3 Slide 3 please. Since our last briefing 4

with the Commission we have produced 29 letter reports.

5 Some of the more notable ones are our final report 6

on the safety aspects of the NuScale design 7

certification and standard design approval.

8 Walt Kirchner will be discussing this 9

report in more detail during his part. A couple of 10 reports on Agency research activities, as noted on this 11 slide. Joy Rempe will be providing more details during 12 her report.

13 Slide 4 please. We continue to review and 14 offer our advice on digital instrumentation and control 15 topics, as requested by Staff.

16 Charles Brown will be providing details 17 on two of these, one being implementation of 50.59 18 screening for I&C upgrades, and another on branch 19 technical position 7-19 regarding diversity and 20 defense-in-depth.

21 Recently we've been taking on some new 22 projects. We reviewed a few topical reports on the 23 Kairos, molten salt reactor.

24 Likewise, we have seen some topical reports 25

7 on the BWRX-300, a small modular reactor.

1 And although we haven't provided a written 2

report, we have begun to review the operating license 3

application for the SHINE medical isotope production 4

facility.

5 Finally, on this slide, we've completed 6

two subsequent license renewal applications.

7 Subsequent license renewal provides currently 8

operating plants the opportunity to operate for up to 9

80 years when they demonstrate they can safely mitigate 10 age related degradation at their plants. We expect 11 to see many more of these applications in the coming 12 years.

13 Slide 5 please. Now I want to briefly 14 cover two subsequent license renewal reviews that we 15 have completed, and set the stage for one of our 16 transformation topics that I will discuss in a moment.

17 Since our last briefing with you we 18 completed a review of the Peach Bottom application.

19 It was a straightforward review as the applicant had 20 demonstrated thorough technical details on their aging 21 management program, good maintenance of material 22 condition of the plant to date, effective consideration 23 of industry experience regarding aging, management and 24 compliance with regulations.

25

8 The Staff's safety evaluation was thorough 1

and complete. We issued our report in December of last 2

year noting that there were no license renewal issues 3

preventing the NRC from issuing licenses and that the 4

application should be approved.

5 Slide 6 please. Surry was our third 6

license, third subsequent license renewal review.

7 Similar to Peach Bottom, the applicant provided a 8

technically thorough application.

9 However, at some point between the time 10 when the application was submitted and when we took 11 up our review, the station experienced degradation of 12 a segment of their underground fire suppression system 13 piping. The applicant entered this issue into their 14 corrective action program and was dealing with the 15 situation as any other operating facility would be 16 doing.

17 This topic became a subject of a different 18 professional view, including both administrative 19 handling of the problem and technical differences with 20 the approach to resolve the issue.

21 We heard from two individuals that had 22 differing views from the majority of the Staff and 23 considered their input during our deliberations. It 24 was a healthy and professional exchange of information 25

9 and the Committee appreciated the individuals for 1

coming forward and sharing their views with us.

2 We issued our report in April of this year, 3

also noting that there were no open license renewal 4

issues preventing the NRC from issuing the license and 5

that the application should be approved.

6 Slide 7 please. Last topic for me to 7

discuss is an update of our transformation activities.

8 We've been keeping up with the Agency's actions through 9

multiple ways.

10 Earlier this year we met with the EDO's 11 office and learned about the direction the Staff was 12 moving. During this briefing we heard about four focus 13 areas and seven initiatives Staff is pursuing.

14 This is very helpful to us because we saw 15 a nexus with the committee in two areas. One being 16 risk-smart and the other process simplification.

17 Our Staff has also had frequent 18 interactions with NRR, and the details of some of their 19 process initiatives have crossed over into areas of 20 our review.

21 We also recognize the need to always be 22 looking for better ways to conduct our business and 23 continue to focus on safety as our guiding principle.

24 We're seeing some operational benefits 25

10 from our efforts. On a small scale we realize some 1

cost savings by scheduling more subcommittee work 2

during the same week as full committee meetings.

3 On a more significant level, work that our 4

previous chair had initiated to move us to greater use 5

of technology was timely and allowed us to response 6

to pandemic restrictions, hold meetings virtually and 7

meet all our pre-pandemic operational planed goals for 8

the year.

9

Finally, we continue to identify 10 opportunities during a recent retreat. We agreed to 11 consider use of virtual meetings for some of our 12 activities post-pandemic.

13 And one or more important, or more 14 significant ideas, relates to the experience we had 15 with the subsequent license renewal reviews. We'll 16 be trying out a reduction of some subcommittee 17 interactions based on the complexity of technical 18 issues. And instead take the review straight to full 19 committee for deliberation.

20 This has the advantage of reducing burden 21 on Staff and applicants while maintaining full 22 committee engagement. For example, activities such 23 as the subsequent license renewal of the Peach Bottom 24 could skip the subcommittee and come straight to full 25

11 committee while more complicated reviews, such as 1

Surry, would continue to have subcommittee and full 2

committee involvement.

3 This completes my part of the presentation.

4 I now call on Walt Kirchner for the NuScale review.

5 Slide 8 please.

6 ACRS MEMBER KIRCHNER: Thank you. Good 7

morning, Madam Chairman, and Commissioners. I'm Walt 8

Kirchner, Chair of the NuScale Subcommittee. And I'm 9

going to present the results of our NuScale design 10 certification application review.

11 Next slide, Number 9, please. On the left 12 you see the major design characteristics of the NuScale 13 power module, as submitted in their DCA.

14 I'm going to draw your attention to the 15 figure on the right. And highlight several unique 16 features of the NuScale design.

17 It's very highly integrated.

It 18 illuminates large diameter piping outside the reactor 19 pressure

vessel, which is enclosed in the 20 high-strengthened containment vessel. And that is 21 normally under a vacuum, under normal operations.

22 Almost to the effect of a thermos bottle.

23 It's immersed in a large pool of water.

24 The internal dimensions of volumes assure 25

12 that the core remains covered for a wide spectrum of 1

design basis events, including cool down transients 2

in AOO and small break LOCAs, which are design basis 3

accidents, ensuring that specified acceptable fuel 4

limits are not exceeded.

5 The tall riser, or chimney shroud in the 6

middle of the diagram, above the core, provides the 7

driving head for natural circulation. And then you 8

see two helical-coil steam generator bundles wrapped 9

around the riser in the downcomer section.

10 That's shown in red and blue in this figure.

11 And then the really unique features of this 12 design are two passive safety systems. One is the decay 13 heat removal system.

14 And about the middle of the diagram, in 15 green, you see the heat exchangers for the decay heat 16 removal system. And then there are passively actuated 17 ECCS valves. You see three at the top of the reactor 18 pressure vessel and then two recirculation valves, just 19 above the core elevation, at the bottom of the figure.

20 Both systems provide a diverse means 21 through boiling condensation to reject stored energy 22 and decay heat to the reactor building pool. And that 23 provides long coping times.

24 Slide Number 10 please. Now I turn to our 25

13 review of the DCA and the safety evaluation report.

1 After we met our Phase 3 milestone we 2

regrouped. And based on that review, identified 3

crosscutting safety focused areas for our next Phase 4

5 review.

5 Which we supplemented with in-depth 6

technical chapter reviews by Members. Particularly 7

focusing on how the Staff closed open items from the 8

earlier phase. These chapter reviews are then 9

presented to the Committee and approved by the Committee 10 as a whole.

11 We issued our final letter report before 12 the revised July 31st milestone. And our effort, in 13 summary, span about four years and including some 40 14 odd subcommittee and full committee meetings and over 15 two dozen letter reports on the topic. So, it was a 16 very comprehensive review.

17 Next slide please. Number 11. So in our 18 NuScale final letter report, in summary, we found that 19 there is reasonable assurance that the NuScale SMR can 20 be constructed and operated without undue risk to the 21 health and safety of the public.

22 We concluded that the Staff's SER and DC 23 and standard design approval, should be issued subject 24 to the Staff's exclusion regarding finality of design.

25

14 We identified potentially risk 1

significant, but solvable design items, to be reviewed 2

at the COL stage, and updated in the, in an update in 3

the PRA fuel load. I'll cover these items on the short 4

list on the slide in the remainder of my presentation.

5 Slide 12 please. Helical-Tube steam 6

generator design. The NuScale design for the steam 7

generators is different from the existing fleet. The 8

boiling is inside the tube banks, in parallel channels 9

of different lengths.

10 When NuScale did experiments to verify the 11 design, they encountered unstable flows, so called 12 density wave oscillations, with the potential for tube 13 vibration and accelerated tube wear.

14 Typically what is done in the industry, 15 in a case like this, is to take a very large delta P 16 at the inlet to the bundles. And that will suppress 17 oscillations and evenly distribute the flow in the tube 18 banks.

19 Further design work is needed, as well as 20 testing, to demonstrate that the proposed flow 21 restrictor design could adequately suppress the density 22 wave oscillations.

23 Because of these steam generator integrity 24 issues, the Staff proposed that the steam generator 25

15 not receive finality. And we concur.

1 In addition to further testing, the Staff 2

has also proposed a COL item and ITAAC to address these 3

matters.

4 Slide 13 please.

ECCS valves.

5 Successful ECCS performance requires one of three of 6

the reactor vent valves, those are the valves at the 7

top of the pressure vessel, and one or two of the reactor 8

recirculation valves at the bottom, to create a loop.

9 However, failure of these hydraulically 10 operated valves systems are one of the most important 11 risk contributors identified in the NuScale PRA.

12 The valves are positioned by the chemical 13 volume control system. And the reactor recirculation 14 valves, in particular, are in a high boron concentration 15 environment at reactor coolant temperatures. So, 16 corrosion and valve sticking are of concern.

17 Extensive additional qualification 18 testing, required by the Staff, should demonstrate the 19 reliable performance after extended periods in an 20 operational environment and confirm the validity of 21 the PRA failure models.

22 Slide 14 please. Source term. The 23 proposed accident combustible gas monitoring system 24 design that was submitted with the DCA, would require 25

16 un-isolating containment and establishing a sizable 1

flow through non-safety grade, relatively large 2

diameter piping of yet unspecified length outside 3

containment, to obtain a representative sample of the 4

containment atmosphere.

5 We concurred with the Staff on not granting 6

design finality, albeit for different reasons. Theirs 7

was a concern about process sample system leakage; ours 8

was the one of un-isolating containment to a large line 9

and opening the risk of a containment bypass.

10 Design alternatives could resolve this 11 issue. Or a risk informed argument might be used by 12 the applicant at the COL stage to justify an exemption 13 from this post-PMI requirement.

14 Slide 15 please. Boron dilution. In the 15 NuScale power module, boron dilution can occur in the 16 reactor downcomer when natural circulation is 17 interrupted.

18 For example, this could happen during a 19 cool down transient or during a small break LOCA. And 20 it's due to boiling in the core because of the decay 21 heat.

22 And then subsequent condensation, either 23 on the steam generator tube banks and outer -- inner, 24 sorry, reactor pressure vessel wall. Or in the case 25

17 of a leak, a steam leak to the containment, condensation 1

on the containment wall, which is immersed in the 2

reactor pool.

3 It's mainly a beginning of cycle issue 4

because you have high boron concentrations there to 5

compensate for excess reactivity in the core. This 6

interruption of flow results in a situation where when 7

you boil the water that's in the core, you carryover 8

very little of the boron.

9 So the core concentration of boron 10 increases in these events. And the water in the 11 downcomer is diluted, and/or the containment vessel.

12 I note on the slide, and I have a mistake 13 to report, I have the cited NUREG report numbers 14 backwards. So on your Slide 16, as well as 15, those 15 numbers need to be interchanged.

16 But these are issues that were looked at 17 in the 1990 period, post-Chernobyl, with the existing 18 fleet.

19 So, this past February the applicant filed 20 a corrective action under its program and proposed 21 design fixes that included four orifice holes in the 22 riser, about mid-height, to redistribute the higher 23 boron concentration water in the riser to the downcomer.

24 Especially after the top of the riser is uncovered.

25

18 They also changed the containment level 1

and pressure set points for ECCS actuation. And this 2

was to mitigate buildup at de-borated water in the 3

containment.

4 Staff confirmed the efficacy of the orifice 5

for, orifices, in preventing boron levels in the 6

downcomer dropping below critical boron concentrations 7

out to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. However, these changes may not be 8

as effective in post-ECCS actuation with the downcomer, 9

I'm sorry, with the orifice holes being uncovered.

10 So that bypass route is defeated.

11 Next slide, 16, please. In our letter 12 reports we describe a resulting metastable state. And 13 what we mean by that is, the core, as I mentioned 14 previously, the core and the riser are highly borated, 15 but the coolant is diluted below boron, critical boron 16 concentrations in the downcomer. As well as 17 distilling, putting distilled water, essentially, into 18 the containment.

19 A rapid influx with this deborated water, 20 say, due to restoration of natural circulation, could 21 result in re-criticality, return to power and the 22 potential of core damage. Our review of the Staff 23 analyses suggest the need for a more detailed analysis 24 to prevent accidents and to develop recovery 25

19 strategies.

1 And I note here, this is a thermal 2

hydraulics reactor physics problem, I'm not talking 3

about developing operating procedures.

4 There are several factors at issue. It's 5

a complex problem. There are large uncertainties in 6

the boron distribution when you start analyzing it.

7 And existing methods aren't qualified, 8

really, for tracking boron concentration. So it causes 9

the analyst to make numerous assumptions about boron 10 distribution.

11 And finally, this, we're talking about 12 larger time spans than are usually considered. And 13 there are issues with numerical diffusion in terms of 14 estimating boron concentration.

15 Further, just an observation to conclude 16 this section of my report, in the early '80s, 17 inadvertent boron dilution was a topic based on 18 licensing event reports. And in those, and the 19 contractor report cited, human error was determined 20 to be a significant risk contributor. Especially 21 during refueling operations.

22 And we note that the proposed NuScale 23 nuclear power plant will have frequent refueling of 24 the modules.

25

20 Slide 17. Probabilistic risk assessment.

1 The PRA submitted was sufficient in scope and detail 2

to inform the DCA design to reduce risk.

3 The risk measures suggest that the design 4

meets your safety goals with large margins. However, 5

issues that I just went through, like boron dilution, 6

suggest that these margins need to be substantiated 7

going forward.

8 In particular, the importance of the CVS, 9

CVCS system, as the preferred recovery system and human 10 errors associated with building crane operations with 11 frequent heavy lifts, and as I cited earlier, refueling 12 operations, suggests further review at the COL stage.

13 Slide 18 please. Lessons learned. So, 14 in summary, the crosscutting focus area approach we 15 use proved to be effective and could be adopted for 16 future applications.

17 I note that Staff has already implemented 18 such an approach for several advance reactor designs.

19 Secondly, I note that the, for non-LWR advance 20 reactors, they're likely to be much more dependent on 21 modeling in simulation. In part, to compensate for 22 lack of experimental data and/or operating experience.

23 So, critical methodology reports need to 24 be submitted and reviewed early in the process of these 25

21 advance reactor reviews.

1 The completeness of new reactor design 2

should be sufficient to support requested exemptions.

3 Particularly if the application comes in under 10 CFR 4

52.

5 NuScale setup a high bar for justifying 6

exemptions from GECs and did a particularly good job 7

in technically backing up their requests. So, design 8

completeness and confirmatory experimental data will 9

be important to support expeditious review of any 10 exemption requests for future applications.

11 In the case of the boron dilution issue 12 that I discussed previously, the analysis and review 13 should continue beyond an arbitrary cutoff of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, 14 or whatever is appropriate, until such time as it can 15 be demonstrated that the plant is in a safe, stable 16 shutdown condition.

17 And finally, and here I'll borrow from Dr.

18 Bley's presentation to you last December regarding 19 methods. It may be advantageous in the review of 20 advance concepts to follow strategy for independent 21 confirmatory analysis by the Staff, starting with 22 simplicity, then adding complexity as needed. Working 23 the problem backwards beginning with bounding the 24 source term and scaling down the confirmatory analyses 25

22 proportionate to the hazard of the application.

1 This completes my presentation. We thank 2

the Staff and the NuScale for supporting our review.

3 I now turn to our Vice Chairman, Dr. Rempe, who will 4

speak on research.

5 ACRS VICE CHAIR REMPE: Thank you, Walt.

6 Can everyone hear me?

7 CHAIRMAN SVINICKI: Yes we can, Dr. Rempe.

8 Please proceed.

9 ACRS VICE CHAIR REMPE: Thank you. I am 10 Joy Rempe and I serve as Chair for the ACRS Safety, 11 Research Subcommittee.

12 This presentation focuses on the ACRS 13 review of the NRC safety research program, including 14 research activities to prepare the Agency for the 15 future.

16 Slide 20 please. The Office of Regulatory 17 Research, or RES, provides technical advice, tools and 18 information, for meeting NRC's mission. Including 19 resolving safety and security issues, making regulatory 20 decisions and promulgating regulations and guidance.

21 The Atomic Energy Act of 1974 mandates the 22 existing of the Office of Regulatory Research. This 23 congressional mandate recognizes that a strong, 24 technical foundation is required to support the world 25

23 class regulatory and expected that the RES program 1

provide this foundation.

2 Slide 21 please. Since 1974, ACRS has 3

conducted formal reviews of NRC research. Currently, 4

this activity includes our reviews of research 5

conducted in support of the specific regulatory 6

activities, periodic reviews of important ongoing 7

research, and our biennial review of the NRC's safety 8

research program.

9 Slide 22 please. Our 2020 biennial review 10 continues to emphasize the items identified in the 1997 11 Commission direction to evaluate the needs, scope and 12 balance of the reactor safety research program, the 13 progress of ongoing activities to meet Agency needs 14 and how well RES anticipates research needs and its 15 position for the changing environment.

16 Our 2020 letter report also emphasizes 17 prioritization, identification of user

needs, 18 long-term planning and follow-up on prior ACRS 19 recommendations.

20 Slide 23 please. The conclusions and 21 recommendations in our biennial report were developed 22 by integrating insights from an additional meeting with 23 the director of RES to obtain an overview of his program, 24 plan, priorities and areas of interests, three, working 25

24 group information meetings to discuss research 1

conducted by each RES division, and other ACRS review 2

activities, such as focus reviews if important ongoing 3

reports.

4 Staff assistance was essential in 5

completing our review and we appreciate your 6

willingness to participate in this process.

7 In the next five slides, I'll highlight 8

the higher level recommendations of conclusions from 9

our letter report. As I review these guidance, I'll 10 mention selective research projects being conducted 11 within each RES division.

12 I'll also identify relevant follow-on 13 reviews that we have conducted, are planned to conduct 14 on research projects that are being performed to prepare 15 the Agency for future activities.

16 Slide 24 please. The NRC research program 17 is preliminary directed through the user need process 18 in which other agency offices provide research requests 19 to RES.

20 In addition, the agencies now providing 21 RES with a limited amount of resources for future 22 focused research with longer term horizons. Our first 23 conclusion was that the user need process satisfactory 24 meets agency near-term meetings for regulatory 25

25 decisions.

1 In addition, we serve as efforts to 2

initiate future focused research who will prepare the 3

Agency for upcoming challenges, including advance 4

nuclear technology regulation and agency 5

transformation activities.

6 Slide 25 please. Our letter of report 7

emphasizes that we support the systematic approach 8

implemented for RES to prioritize research emphasizing 9

enterprise risk in project selection, evaluation and 10 termination.

11 In our 2018 biennial letter report, we 12 identified the need that a systematic approach to 13 prioritize research projects. And during our 2020 14 review, we were pleased to see that a prioritization 15 approach is being implemented that consider factors 16 such as safety and security, emerging issues, 17 innovative technologies and efforts needed in 18 certainties, preservation of core competencies and the 19 development and maintenance of analysis methods and 20 tools.

21 We continue to emphasize that all RES 22 activities be prioritized and selected using this 23 process, including the future focused research 24 projects.

25

26 As part of the conclusion, we assert that 1

ongoing RES efforts to engage other offices are critical 2

for this approach to be successful.

3 Slide 26 please. Our letter report 4

discusses several important international 5

collaborations. Such as the new Canadian Nuclear 6

Safety Commission collaboration, that will provide the 7

Agency important data and new models for evaluating 8

non-LWR technologies.

9 As RES continues to leverage resources 10 using international and inter-agency collaborations, 11 our third conclusion emphasizes that's it's important 12 for RES to ensure that Agency priorities continue to 13 be clearly defined and addressed.

14 Slide 27. RES contributions are preparing 15 the Agency for anticipated non-LWR submittals. And 16 our letter of report emphasizes that the non-LWR 17 reference planned evaluations should provide 18 confidence about the adequacy of selected computational 19 tools and identified any remaining data gaps.

20 In the upcoming year, RES will be briefing 21 us about the results in these referenced plans 22 evaluations.

23 Slide 28. We also have briefing planed 24 that will allow us to provide input on several other 25

27 RES activities. Such as the efforts to address the 1

gap created by the unexpected loss of the Halden test 2

reactor, and an additional briefing on the selection 3

and process of future focused research projects.

4 We've received our first briefing on the 5

selected Fiscal Year '20 future focused research 6

project in September 2020. And we have a second review 7

plan in the next year to discuss the progress made on 8

the Fiscal Year '20 projects and the recently selected 9

Fiscal year '21 projects.

10 In summary, with respect to our biennial 11 review, I want to observe that RES has responded to 12 our 2020 letter report and indicated that they agree 13 with our recommendations and are implementing them with 14 existing RES programs and processes.

15 And the next slide, 29 please. Finally, 16 with respect to RES activities that will prepare the 17 Agency for the future, I want to emphasize that we have 18 planned information briefing since several research 19 topics that will address emerging Agency needs.

20 The future focused research projects are 21 as planned to address the Halden gap, non-LWR research 22 activities, such as results from the non-LWR referenced 23 planned evaluations, and the RES integrated university 24 programs for mission related research and development.

25

28 RES and ACRS have concurred that these 1

briefings, which are designed to provide timely and 2

effective ACRS input to RES, will be performed instead 3

of the quality reviews that I discussed during our 4

December 2019 ACRS meeting with you.

5 This completes my portion of our ACRS 6

presentation. And I'd now like to call on Member Brown, 7

who will provide an update on ACRS digital 8

instrumentation and control review activities.

9 Charlie.

10 ACRS MEMBER BROWN: Thank you, Joy. I'm 11 Charles Brown, Chair of the Digital I&C Subcommittee.

12 Slide 31 please. I'll be discussing and 13 presenting two digital I&C letter reports that we wrote 14 this year.

15 The first is on Regulatory Guide 1.187, 16 Revision 2, and NEI 96-07, Appendix D, Revision 1.

17 These regard the application of 10 CFR 50.59 to Digital 18 I&C modifications.

19 The second one will Be Branch Technical 20 Position 7-19. Revision 8, which is guidance for 21 defense-in-depth and diversity due to latent defect 22 common cause failures and Digital I&C systems.

23 Slide 32. I'll cover Reg Guide 1.187 and 24 Appendix D of 96-07 first. 10 CFR 50.59(c)(1) allows 25

29 licensees to change facilities and procedures in its 1

UFSAR, perform tests or experiments not in its UFSAR, 2

without a license amendment request if, one, the 3

technical specification changes are not required, and 4

two, the change, test or experiment does not meet any 5

of the eight (c)(2)(I) through (viii) criteria of 10 6

CFR 50.59 (c)(1). Or (c)(2), excuse me.

7 NEI 96-07, excuse me, Slide 33 please.

8 NEI 96-07, Revision 1, was issued in November 2000 and 9

provided guidance to aid industry in determining if 10 an LAR was required for facility changes based on 10 11 CFR 50.59.

12 Reg Guide 1.187, Revision 1, endorsed NEI 13 96-07 without clarifications or exceptions. NEI 96-07 14 applies to all structure, systems and components to 15 address 10 CFR 50.59 requirements.

16 Its use over the next few decades resulted 17 in several, in varying opinions and difficulties in 18 applying this guidance to Digital I&C systems.

19 Slide 34. This difficulty was the 20 interpretation of 10 CFR 50.59 item (c)(2)(vi) stating 21 that a license amendment request is needed if the change 22 would "create a possibility for a malfunction of an 23 SSC important to safety with a different result than 24 any previously evaluated in the final safety analysis 25

30 report as updated for DI&C changes." Very all 1

encompassing.

2 As a result, NEI developed 96-07, Appendix 3

D, to assist licensees in performing 10 CFR 50.59 4

reviews for digital modifications.

5 Slide 35 please. Reg Guide 1.187, the 6

Revision 2, prepared by the Staff, endorsed Appendix 7

D, with an exception. Which was a point of contention 8

between the NRC and NEI relating to the phrase, 9

"different result than previously evaluated in the FSAR 10 in 10 CFR 50.59 section (c)(2)(vi).

11 Slide 36 please. Our letter of report of 12 June 20th, 2019 agreed that new guidance has been 13 needed.

14 However, we concluded that there is an 15 opportunity for expanding the use of 10 CFR 50.59 for 16 Digital I&C modifications by more clearly identifying 17 the significance of different results caused by a 18 malfunction of structure systems or components 19 important to safety, as specified in Criterion 6.

20 I underlined the significance because 21 that was the point we were trying to get alone.

22 Difference, without that, is very broad.

23 Slide 37 please. Basically we urge the 24 Staff and NEI to resolve the disagreement.

25

31 Subsequently, NEI developed a substantially revised 1

section, 4.3.6, in Appendix D, Revision 1, dated May 2

2020, to resolve the exception.

3 The revision focused on the significance 4

of a different result to determine the need for an LAR 5

prior to a Digital I&C change. It also provided 6

numerous examples of when a change will create a 7

different result and when it will not create a different 8

result. And they upgraded that to consider, to take 9

into consideration the significance of the different 10 results.

11 Slide 38 please. The Staff agreed in 12 proposed revised draft of Regulatory Guide Revision 13 2 with clarifications only. In other words, no 14 exception.

15 During our 674th meeting, we reviewed NEI 16 96-07, Appendix D, Revision 1 and Regulatory Guide 17 1.187, Revision 2. Our letter report of June 23rd 18 agreed with the resolution and the Reg Guide Revision 19 2 should be issued.

20 Slide 39. Next I'll cover Branch 21 Technical Position 7-19, Revision 8, October 2020.

22 The BTP provide Staff review guidance for evaluating 23 any defense-in-depth and diversity means credited to 24 address vulnerability to common cause failures.

25

32 It applies for any new plant designs or 1

changes to any existing plants that require NRC 2

approval. It does not apply to changes under 10 CFR 3

59. 50.59.

4 Slide 40 please. The revision maintains 5

the policy established by the Commission in SRM to 6

SECY-93-087.

7 It's further amplified by identifying the 8

need for a well-defined Digital I&C architecture 9

meeting the fundamental design principles to identify 10 defense-in-depth and diversity needs.

11 It also introduces the use of safety 12 significant assessment categories, high, lower and 13 lowest. It also identifies means to eliminate and 14 mitigate common cause failures and how some common cause 15 failure consequences may be acceptable.

16 And that is a new item. In other words, 17 when you evaluate the common cause failure, you might 18 find that the end result is acceptable and you don't 19 have to worry about what it does.

20 Slide 41 please. It revises guidance on 21 spurious actions and diverse manual actions. And it 22 also includes use of qualitative assessments per 23 Supplement 1 to Regulatory Issues Summary 2002-22 for 24 non-reactor protection systems and engineered safety 25

33 feature actuation systems.

1 I want to make sure you focus on, it's a 2

non-reactor plant protection systems and engineered 3

safety feature actuation systems.

4 Slide 42 please. Our recommendations were 5

as follows. Number 1 was that the Revision 8 should 6

be issued subsequent to incorporation of our Revisions, 7

Recommendations 2 and 3.

8 Recommendation 2 was that the branch 9

technical position discusses combining or integrating 10 of the reactor trip system in ESFAS and associated 11 communications architectures into a single protection 12 system. This approach challenges two critical 13 defense-in-depth and diversity elements: redundancy 14 and independence.

15 The branch technical position should 16 ensure that reviewer is verified, that fundamental 17 architecture principles are maintained.

18 Slide 43 please. The third recommendation 19 was that the branch technical position should ensure 20 that interconnections between high safety significant 21 systems and those of lower safety significance, are 22 one-way, unidirectional digital communication devices 23 rather than bidirectional communication devices.

24 The use of bidirectional reduces 25

34 independency and defense-in-depth. And this was, we 1

recommended this to preclude the comprise of high safety 2

significant systems.

3 That concludes my presentation. Matt, 4

I'll pass it back to you.

5 ACRS CHAIR SUNSERI: Thank you, Charlie.

6 Chairman and Commissioner, this concludes our prepared 7

remarks. We are now ready for your questions.

8 CHAIRMAN SVINICKI: Thank you very much, 9

Chair Sunseri, Vice Chairman Rempe and all ACRS Members, 10 for your work on the topics that were presented, but 11 also on the numerous letter reports and topics that 12 we did not select as presentations for today. Thank 13 you.

14 It's quite an extensive body of work. And 15 you were also working under the unplanned circumstance 16 of the public health emergency, so the Commission is 17 very grateful for your efforts.

18 For the Commissioner questioning today, 19 we will begin with Commissioner Caputo.

20 COMMISSIONER CAPUTO: Good morning.

21 Thank you all for joining us today.

22 I'd like to begin my questions with Dr.

23 Rempe. On Slide 25 you stated, we support the 24 systematic approach implemented by research to 25

35 prioritize the research projects emphasizing 1

enterprise risk and project selection evaluation and 2

termination.

3 Would you please discuss the emphasis on 4

enterprise risk as opposed to safety significance and 5

safety risk?

6 ACRS VICE CHAIR REMPE: Sure. Clearly, 7

the research programs are investigating safety. But 8

as they select projects over the years, there are some 9

other factors that should be considered.

10 For example, at one point in time a 11 particular research project may have significant safety 12 issues. But as the years go by they may learn things 13 from this initial research that may demonstrate that 14 safety is no longer important.

15 The interest in that research may decrease.

16 For example, right now, we are very concerned about 17 the non-LWR applications that may be facing the Agency.

18 If, for example, some of the interest in 19 these non-LWRs decreases, that should be considered.

20 It may still be a safety issue, but if no one is going 21 to build them that may not be as important.

22 So, we need to consider that. We need to 23 consider the core competencies.

24 When the events of Fukushima happened, 25

36 certain core competencies in their preservation can 1

be very important even though perhaps they didn't seem 2

important until we had that event. So it's good to 3

think about the various aspects, as I mentioned in the 4

list of items and enterprise risk during my 5

presentation.

6 And if the Agency tries to prioritize the 7

research, they need to consider all of these factors.

8 And I believe that's now being done. Did that help?

9 COMMISSIONER CAPUTO: Yes. Thank you.

10 I'm going to continue in that vein though.

11 You noted how ACRS examines the needs, 12 scope and balance of the reactor safety research 13 program. How well it anticipates research needs and 14 how it's positioned for a changing environment.

15 However, I remain concerned that the 16 research portfolio may be overly focused on historic 17 issues and may not have that proper balance with forward 18 looking work.

19 So, what I'd like to ask is, and maybe other 20 Members would like to comment, but in reviewing our 21 research, does the Committee specifically examine 22 whether projects remain safety significant or whether 23 they're simply pursuing increasingly minute levels of 24 accuracy such that further research is unlikely to alter 25

37 existing regulatory activities?

1 Because I would be concerned that if we're 2

not seeking out that distinction point where we're 3

pursuing resource, it's not going to change the nature 4

of what we do, then it may be important to reallocate 5

those resources to more forward looking issues.

6 Can you just give me a sense of your views 7

on that? And whether or not you think we're striking 8

the right balance.

9 ACRS VICE CHAIR REMPE: I believe we are 10 trying to strike that correct balance. I call your 11 attention, in the division of engineering section of 12 our biennial 2020 report.

13 And it reports several activities that are 14 going to be ceasing. And they may have been terminated 15 by this time, but there are issues that we regularly 16 have brought up over the years.

17 And in 2018 we mentioned them. And in 18 2020, in our report, we reported that these activities 19 should be, they are, the Staff reported they are being 20 finalized.

21 The final documentation is being completed 22 and they should be terminated at this time. We'll 23 follow up on that in your 2020 report.

24 But yes, we do try and quiz the Staff on 25

38 those points. And we have our information briefs on 1

the projects within each division.

2 COMMISSIONER CAPUTO: Okay, thank you.

3 I'd like to move on to Digital I&C with Mr. Brown.

4 On Slide 30. I gather the ACRS is working 5

to define the significance of a different result, it 6

came up several times.

7 I'm a little concerned that developing a 8

common understanding or a working definition is often 9

something that is helpful to do at the outset of a 10 project. So, at this point, it seems that it's 11 difficult to tell whether we're actually nearing the 12 finish line with Digital I&C or whether we're continuing 13 to be stuck in a perpetual debate over definitions of 14 terms.

15 So you indicated that branch technical 16 position 7-19, Revision 8, should be issued once two 17 additional recommendations are incorporated. You also 18 indicated that Reg Guide 1.187, Revision 2 should be 19 issued with clarifications.

20 Can you tell me when you expect these 21 documents to be final and whether they provide enough 22 regulatory clarity and stability for licensees 23 ultimately to successfully pursue and implement Digital 24 I&C upgrades?

25

39 ACRS MEMBER BROWN: Okay. Well, I'll try 1

to adjust this, address this, in a generalized manner, 2

as well as specific.

3 The definition of once you integrate or 4

try to integrate a couple of systems together provides 5

a difficult, how do you address that when you put stuff 6

together and put it into one system.

7 The integration of those two systems is 8

not what we would, any of us would think to be a primary 9

consideration and combination. And they address that 10 in 96-07. Relative to addressing some other systems.

11 Like the feedwater control system.

12 The feedwater control system, right now 13 in most of the plants, has four, there is three or four 14 valves, if you're a light water reactor with four loops.

15 COMMISSIONER CAPUTO: Mr. Brown, I think 16 you misunderstand the nature of my question.

17 ACRS MEMBER BROWN: Oh, okay.

18 COMMISSIONER CAPUTO: My question is much 19 more in the vein of, are we done yet. I think it's 20 been mentioned by the Commission, several times in the 21 past, including one by myself, the Airbus 320 took off 22 in 1987 with digital technology. The Navy Seawolf 23 program in 1989, the Boeing 777 in '94. Not to mention, 24 the geneses of Digital I&C was actually the NASA's 25

40 Apollo Program.

1 What I'm concerned about is whether or not 2

we're actually coming to closure and resolving these 3

issues. These debates, the nature of what you were 4

just explaining to me, I'm guessing these debates and 5

discussions have been going on for over 30 years.

6 My question is targeted at closure. Are 7

we actually reaching resolution or does the debate 8

simply continue indefinitely? That's the nature of 9

my question.

10 ACRS MEMBER BROWN: Okay. I understand.

11 I did not understand that at first.

12 So I'm going to give you a background and 13 a little bit of history. Twelve years ago I came on 14 to this Committee to address, to try to help the 15 Committee to address how do we incorporate Digital I&C 16 systems into the plants. Whether they're existing or 17 a new design certifications.

18 I sat in on my first subcommittee meeting 19 in July or August of 2008. The presentation by the 20 applicant at that time, and this is my personal opinion, 21 was terrible. You couldn't tell what was going on.

22 The effective way to evaluate this stuff, 23 the vendor would give you a stick-man type architecture, 24 and then they would say we will agree to comply with 25

41 every reg guide regulation position that is in all your 1

standards.

2 However, you couldn't tell, it was like 3

evaluating, if you're going to design a car, I'm going 4

to evaluate the brake line, then I'm going to look at 5

the fuel line, and then I'm going to figure out how 6

the carburetor works, but I don't know how they all 7

fit together to make a car.

8 We, at that time, told them that it was 9

an unsatisfactory approach.

There was no 10 architecture, how you can define and understand what 11 this basic system looks like and how you maintain the 12 fundamental principles of redundancy and dependence, 13 diversity and defense-in-depth, deterministic 14 processing, simplicity, control of access, the whole 15 panoply of what I call basic fundamental design 16 principles.

17 It took about a year and a half or two before 18 that particular project finally presented an 19 architecture where we could become to the point where 20 it was satisfactory and would work satisfactory and 21 we could agree with it. And we wrote a letter to say 22 such.

23 The second project came along was AP-1000.

24 Somebody was obviously listening. We had a much 25

42 better architecture presented.

1 It didn't take as long to get through it.

2 There were a couple of issues. And the AP-1000 3

applicant complied.

4 And then the third project was the Korean 5

KHNP. They presented theirs. They obliviously had 6

really been listening. I don't think it took us hardly 7

any time at all to review that project and agree with 8

it.

9 And when NuScale came along, I think it 10 took six or seven months to go through all the details.

11 And they fully complied with the idea that an 12 architecture complete, where you can see how you 13 maintained independence redundancy and all those 14 principles, that's the bull work.

15 That's the framework you have to prove to 16 ensure you got a satisfactory system. It took about 17 six months to do that.

18 So if you ask me my judgment, we have made 19 significant progress over the last ten to 12 years.

20 I can't speak for the previous years, from 1987 to 2008, 21 I was in the Naval Nuclear Program at that time 22 developing all the Naval nuclear Digital I&C systems 23 from 1978 until December 1999.

24 So I was appalled when I first got here.

25

43 Right now, we have issued, and just to put it in a 1

track, a ISG-6, I believe it was, initiated a project 2

to do pre-review or pre-application reviews where the 3

focus was on the architecture of the systems to make 4

sure the vendors understood what the staff wanted.

5 That was after the first one back in 2008.

6 Subsequent to that, I guess, I've forgotten 7

which SRM or which SECY it was, talking about 8

risk-informed and technology-neutral type stuff. And 9

a DSRS was put into place for the mPower SMR. And that 10 design-specific review standard fundamentally focused 11 on the architecture and went through all the various 12 items that I've just discussed to show that it met that.

13 That was a much simplified approach, it 14 was more easily understood, and it was able to be agreed 15 to pretty readily. That same architecture, that same 16 principle in the mPower DSRS, was then translated into 17 the NuScale, which allowed us to complete that review 18 in a matter of six, seven, eight months.

19 So right now, we're on track. Two things 20 have happened. One, we have now issued BTP 7-19, which 21 incorporated this thought process into the 22 defense-in-depth review of any new project to ensure 23 that we don't beat it to death for no known reason.

24 The same thing applies with the general 25

44 approach for a new design application. There's a new 1

design-specific review standard called design review 2

guide for non-light water reactors, which now breaks 3

down the architecture and walks through each of those 4

features, and that's how the design will be assessed 5

in the future.

6 We've just completed a review of that and 7

will soon be issuing a letter. And so if you ask my 8

opinion, we have made giant steps over the last ten 9

years. Has it been difficult? Yes. Has it been easy?

10 No. Are every piece, you know, little piece of it 11 complete? I don't think so. But compared to what was 12 established back 25 years ago, I think -- or 30 years 13 ago even, I think the progress has been quite good.

14 And this committee, in fact, has been the 15 lead since 2008 in making sure this happens. The staff 16 has done a very good job of incorporating those thought 17 processes in putting together over these various 18 projects that projects that have come along and included 19 the lessons learned from back fits and put together 20 some new documents that are very streamlined and helped 21 those reviews be streamlined.

22 Did that answer your question?

23 COMMISSIONER CAPUTO: Yes, I believe it 24 did.

25

45 CHAIRMAN SVINICKI: Thank you very much, 1

Commissioner Caputo. Next we will hear from 2

Commissioner Wright.

3 COMMISSIONER WRIGHT: Thank you. I 4

thought somebody was trying to add on. Okay, we're 5

over -- okay, thank you. Thank you very much.

6 So good morning, and I thank you for the 7

presentations. And also, you know, especially during 8

these challenging times during the pandemic and 9

everything, we want to thank you for the way you're 10 doing what you're doing. Because the independent 11 advice that you give us is very -- is critical to what 12 our Agency's doing. So thank you for that.

13 Chairman Sunseri, I appreciate that you're 14 keeping up on the Agency transformation efforts and 15 leveraging technology to do your work during this health 16 emergency. You indicated on one of your slides, I 17 believe it was slide 7, but we don't have to pull it 18 up, but you indicated that you met with the OEDO 19 representatives early in 2020 to discuss transformation 20 activities, and that you interact frequently on staff 21 changes.

22 Can you tell me a bit more about these 23 interactions with the OEDO staff? And do you have a 24 single point of contact on the ACRS when, you know, 25

46 who I guess would transmits any information activity 1

to the rest of the group, or does the staff provide 2

information to the ACRS, or is there some other way?

3 ACRS CHAIR SUNSERI: Thank you for the 4

question. So there's a couple of ways that we keep 5

up with this. First off, I would say Scott Moore, our 6

Executive Director, has close tie-ins with NRR and the 7

other offices on the other side of the Agency. And 8

that is in fact how we stayed abreast with the EDO's 9

office.

10 We had committed to the Commission through 11 one of our letter reports that we would keep up with 12 what is going on with the Agency's transformation 13 activities and then align ourselves with some of those 14 or, you know, integrate some of our own ideas.

15 So Scott Moore, our Executive Director, 16 actually set up that meeting with EDO office because 17 it had been about a year. And we had a good presentation 18 that actually opened our eyes to the fact that there 19 had been a change in direction somewhat from where we 20 had originally set up our transformation activities 21 to where the Agency is currently going with the four 22 focus areas and seven initiatives.

23 And that's how we learned about Be 24 riskSMART or more details about Be riskSMART and more 25

47 details on some process simplification with regard to 1

upcoming applicants, of which we're trying to align 2

our processes with also. So through our Executive 3

Director's contact into the other offices is one way.

4 The second, another way is each one of our 5

-- we have technical staff and we have administrative 6

staff under Scott that interfaces routinely with NRR 7

and others on the other side about what's going on.

8 And that's -- that, to some extent, that's 9

how we worked out our arrangement with NuScale on the 10 different review that Dr. Kirchner talked about in his 11 presentation was, you know, through our staff 12 interaction with us. So that's another example of the 13 way we find out about transformation activities that 14 are going on in the other agencies.

15 And you know, we just continue to pursue 16 that with the respect to subsequent license renewal.

17 We're working right now on a Memorandum of 18 Understanding to, you know, more integrate or more 19 delineate, I should say, how we're going to conduct 20 those reviews when we find out that a subsequent license 21 renewal activity has, you know, is technically sound 22 and no significant challenges to it and no open items.

23 We should be able to take those straight to full 24 committee and save everyone a lot of effort on that.

25

48 So those are just kind of three examples 1

of the way we do it, and there's probably more going 2

on behind the scenes that I don't even know about.

3 But I hope that addresses your question.

4 COMMISSIONER WRIGHT: Yeah, thank you.

5 So some of the current transformation and innovation 6

activities you just mentioned you're tracking, what 7

do you consider maybe the most relevant to ACRS and 8

its work, of these transformation activities?

9 ACRS CHAIR SUNSERI: Yeah, so I think the 10 riskSMART is clearly one. I mean, the ACRS has been, 11 you know, an advocate of using risk techniques all 12 along. I mean we're right on the front end of it.

13 So any time we can enhance or improve safety by taking 14 a risk-informed approach to it and avoid doing things 15 for the sake of doing them and then doing things that 16 have -- and then focusing on things that are more 17 risk-significant and make a difference, that's clearly 18 something that we're interested in.

19 So the -- so you know, our risk activities 20 and the things we're involved with as far as further 21 promulgating or further moving the agency towards being 22 a risk-informed, more risk-informed going into the 23 future is certainly an area that we're very closely 24 aligned with.

25

49 COMMISSIONER WRIGHT: Have you, has ACRS 1

engaged at all with EMBARK Venture Studios?

2 ACRS CHAIR SUNSERI: I am not aware that 3

we have. I saw that term come up the other day in some 4

communication. I wasn't, I'm not familiar with it, 5

maybe one of the other members are.

6 COMMISSIONER WRIGHT: Okay. Yeah, just 7

if you have or I just wondered if there were any 8

initiatives that you all felt that you could benefit 9

from. So we can talk offline on that at another time.

10 So during this whole pandemic thing, you've 11 being doing a lot of things virtually. Are there 12 anything that you've been doing now that you feel might 13 be best continued in a virtual way, or do you think 14 there are some things that absolutely have to be done 15 in person?

16 ACRS CHAIR SUNSERI: So I mention that we 17 are looking at using virtual technology after the 18 pandemic restrictions are gone. And we think there 19 is an opportunity to engage applicants and maybe staff 20 and even some of our own members in a way to where we 21 don't to bring everybody together in the room at the 22 same time.

23 Now, I think our experience is that 24 transactionally, our meetings have gone very well and 25

50 we've moved business forward and we've conducted very 1

thorough and good reviews. There is a little bit, I 2

would say, and I'll inject my personal opinion somewhat 3

here, is I think there is a little bit of -- a little 4

bit of lost interpersonal reaction loss on the virtual 5

meetings.

6 I mean, where you're together in a room 7

face to face, you can read the whole language of the 8

room. And it gives you a little bit different sense 9

sometimes of how a topic is percolating through the 10 group when you can see, you know, the shrugs or, you 11 know, the mannerisms of the group as a whole.

12 When we're in this virtual context, 13 oftentimes we don't even have the cameras on, we're 14 just listening to a voice. Or like in this particular 15 example, you only see my face versus the nine other 16 members.

17 COMMISSIONER WRIGHT: Right.

18 ACRS CHAIR SUNSERI: So, you know, we are 19 looking forward to getting back to face to face, but 20 we recognize that the virtual meetings have added a 21 dimension that is actually beneficial for us, and I 22 think we're going to continue some of that. We're going 23 to integrate it in with our business going forward.

24 COMMISSIONER WRIGHT: Right. With the 25

51 time I've got left, I'll bring Dr. Kirchner in and talk 1

a little bit about NuScale, because it's been in the 2

news lately and it's certainly timely. So my 3

understanding is that the ACRS disagreed with the staff 4

on certain conclusions and recommendations regarding 5

the boron redistribution issue that were outlined in 6

that report.

7 I

believe there were certain 8

recommendations and conclusions, three of them I 9

believe that were primarily focused on operator 10 recovery actions. Can you tell me a little bit more 11 about those disagreements and, you know, and how you 12 all went through that?

13 ACRS MEMBER KIRCHNER:

Thank

you, 14 Commissioner. Well, this was an issue that we -- a 15 little history first. We identified this, when I look 16 at my notes, probably a year ago June was the first 17 time that this surfaced. And it made our short list 18 of focus areas that, obviously.

19 And earlier this calendar year, when 20 NuScale came back with their proposed changes, these 21 were definitely an improvement. They certainly 22 addressed the cooldown transients that were a concern 23 that resulted in boron dilution.

24 Where we probably were looking for more 25

52 detailed analysis was in the case of post-ECCS actuation 1

where the boron concentration in the downcomer can drop 2

below the critical boron concentration within hours.

3 As I mentioned, this is a, it's a difficult problem 4

to analyze. There are a lot of factors that you have 5

to consider.

6 Our current code suite that is used, both 7

by the applicant and for that matter the confirmatory 8

codes that the Agency has, aren't really well suited 9

for tracking boron distributions and mixing. And the 10 staff, it's not that we disagreed with the staff per 11 se. The staff did a couple of bounding analysis 12 scenarios. Those were good.

13 Sometimes the problem isn't easily 14 bounded. Our big concern really was that there is the 15 possibility in trying to recover from such an event 16 that you could restore natural circulation. Now, 17 depending on what the boron concentration is in the 18 downcomer and/or the containment, you have the 19 possibility of sweeping quickly a large volume of 20 de-borated water into the core.

21 And that's our concern. And so it's not 22 so much that we disagreed with the analyses that the 23 staff presented. It was more a completeness 24 perspective on our part, I believe, to further explore 25

53 the issue and ensure that the recovery options that 1

are at hand will actually take you to the safe condition.

2 So that doesn't perhaps really answer your 3

question, but I don't think it's so much, again, I would 4

say it's not so much that we disagreed with the staff's 5

analyses, but we think that there's more work to be 6

done on this issue.

7 COMMISSIONER WRIGHT: Okay, thank you, 8

thank you, Chairman.

9 CHAIRMAN SVINICKI:

Thank

you, 10 Commissioner Wright.

Next we'll hear from 11 Commissioner Hanson. Please proceed.

12 COMMISSIONER HANSON: Thank you, Chairman 13 Svinicki. Good morning, everyone, it's nice to meet 14 you all virtually. I wish we could at some point I 15 hope we can be in the same room together. As the new 16 guy, I'm -- this is my first opportunity to kind of 17 be with you all collectively, so it's good be here.

18 CHAIRMAN SVINICKI: I was just going to 19 mention that if we didn't have the public health 20 emergency, in general the ACRS gave a wonderful holiday 21 gathering after this December meeting with the 22 Commission, which was always such a nice part of doing 23 some fellowship in the holidays. So Commissioner 24 Hanson, I hope we do get back to that.

25

54 COMMISSIONER HANSON: Yeah, I hope we do, 1

thank you.

2 I'll start with Dr. Rempe. Thank you for 3

your presentation this morning. Advanced reactor 4

issues are getting a lot of attention. But I've been 5

thinking about other parts of the advanced reactor fuel 6

cycle, such as transportation, storage, security, waste 7

management, enrichment, fuel fabrication, etc.

8 And I'm wondering if those issues are also 9

getting, or if they are getting sufficient attention 10 from a research standpoint. The ACRS noted in its 11 bi-annual -- biennial evaluation letter that a 12 systematic approach is being implemented by RES to 13 prioritize research, emphasizing enterprise risk in 14 project selection evaluation and termination.

15 So to what extent are these other areas 16 being considered as potential research projects?

17 VICE CHAIR REMPE: Thank you for the 18 question. I would draw your attention to the point 19 that we raised in our letter report about the need to 20 look at some of the unique issues posed by some of the 21 advanced reactors where they plan to load the core 22 offsite and transport a reactor with a loaded core to 23 the site. And then after the fuel is burned, I'll take 24 the reactor with the spent fuel back and do something 25

55 with the core at a different location.

1 And we have raised that in several of our 2

meetings. And I was pleased to see that, that issue 3

is starting to be addressed, and in fact Amy Cubbage 4

brought it up in the stakeholder meeting recently and 5

I think it was last October. So we aren't yet aware 6

of how the staff will deal with some of these issues, 7

but the staff is cognizant of it, and we will be 8

exploring that topic in some of these additional 9

briefings that we're going to be holding.

10 We explore it not only through the research 11 venue, but also we have a separate subcommittee (audio 12 interference) of the advanced reactors, future 13 licensing activity. So we've been going through the 14 reports issued by the staff for the various methods.

15 And we had one of those meetings this week 16 and we brought up some of those issues that you're 17 mentioning with Volume 5 for the codes that the staff, 18 so we've been asking them how they were going to deal 19 with those aspects of the fuel cycle.

20 So yes, research is starting to address 21 that. We are just starting to consider it in our 22 reviews and we haven't issued a letter on it, but I 23 believe we will be discussing it in our one of our letter 24 reports in the upcoming year.

25

56 Does that help, or --

1 COMMISSIONER HANSON: Great, yeah, very 2

much so.

3 VICE CHAIR REMPE: --- did I answer your 4

question?

5 COMMISSIONER HANSON: Yeah, no, thank you, 6

that's very helpful. I really appreciate that.

7 I want to turn to digital I&C. I 8

appreciated the interaction between Commissioner 9

Caputo and Mr. Brown on this subject. Mr. Brown, you 10 mentioned ACRS's involvement in evaluating the digital 11 I&C systems with NuScale and other technologies that 12 are coming down the pike.

13 To what extent has ACRS been involved in 14 looking at application of digital I&C systems to 15 existing plants? Say, at Limerick or other utilities 16 that are exploring this or have put forward draft 17 proposals?

18 ACRS MEMBER BROWN: Well, at this point 19 we don't look at anything until there's a formal request 20 for an LAR from the applicant, from the operating plant, 21 whoever owns it, and they submit that to the NRC.

22 COMMISSIONER HANSON: Okay.

23 ACRS MEMBER BROWN: And then there's a 24 review period established, and then our -- we get 25

57 scheduled with the documentation.

And then 1

subcommittee meetings and follow-up with full committee 2

meetings. But at this point, the only one we've dealt 3

with in the last few years was Diablo Canyon. None 4

others.

5 The only other one I can remember -- an 6

Oconee one was done back in 2008, but that was, I'd 7

just walked in the door at that time, so that was 8

fundamentally done by the time I got here. So we have, 9

our committee doesn't do much of anything until there's 10 a formal application with the details provided to the 11 staff.

12 COMMISSIONER HANSON: Thank you for that.

13 I mean, let me follow up. I mean, at this point, 14 though, with the recommended revisions to the BTP and 15 the reg guide, do you feel like the staff is 16 well-positioned then to expeditiously evaluate LARs 17 or other proposals for digital I&C systems on existing 18 plants?

19 ACRS MEMBER BROWN: Yes, in particular 20 most, in my person opinion based on the new things in 21 1.187 and the NEI documents, with the exception of the 22 reactor trip systems and ESFAS systems, engineered 23 safeguard safety feature systems, they provide many 24 examples of how you can proceed with those without 25

58 getting wrapped around the axle. So I think that's 1

a significant improvement in where we're going with 2

that.

3 The new design review guide that we're 4

presently in process of reviewing is a substantial 5

improvement over the old standard review plan that, 6

in NUREG-0800, that has been used for decades. It 7

focuses on the architecture, which takes it from a 8

bottom-up review approach to a top-down review 9

approach, where it simplifies what you have to look 10 at.

11 If you have an architecture that defines, 12 maintains your key issues of redundancy and 13 independence, those are the linchpins. And if you can 14 show that in an architecture, now you have to only look 15 at a few details within the design to say is there 16 something we missed that's based on some different types 17 of systems that you put in to, you know, to do the 18 computations.

19 So I think the position of the new reg 20 guides for new plants, I think that new design review 21 guide, which we haven't, you know, we're about to send, 22 issue a letter to the staff. It's for non-lightwater 23 reactors, but without question the entire guide could 24 apply to lightwater reactors, if somebody wants to do 25

59 that. Or for operating plants to upgrade their I&C 1

systems.

2 And as a matter of fact, we made a comment 3

of that in our letter which will be issued probably 4

in the next week or so. Or two weeks, whatever it is 5

to get us through the editorial process.

6 COMMISSIONER HANSON: Okay.

7 ACRS MEMBER BROWN: So yes, I think the 8

documents that have come out have given the applicants 9

the opportunity to do it. The next issue after that 10 is execution. And hopefully the committee will be able 11 to help the staff in the reviews and help expedite those 12

-- the execution in order that the plant requests can 13 be processed expeditiously.

14 COMMISSIONER HANSON: Great, I hope so 15 too, because I share Commissioner Caputo's question 16 of kind of are we there yet.

17 ACRS MEMBER BROWN: Well, you're all both 18 right on the numbers. This has been a frustration of 19 mine ever since I got here 12 years ago.

20 COMMISSIONER HANSON: Yeah, I can --

21 ACRS MEMBER BROWN: The Committee invited 22 me to be a participant, a member, just so that we could 23 try to get a handle on this. Hopefully we've done that.

24 COMMISSIONER HANSON: I hope so too, and 25

60 thank you for your service on the committee for these 1

last 12 years.

2 ACRS MEMBER BROWN: Thank you.

3 COMMISSIONER HANSON: I look forward to 4

more of that.

5 ACRS CHAIR SUNSERI: Commissioner? I'm 6

sorry to interrupt, Commissioner, this Matt Sunseri.

7 May I be recognized?

8 COMMISSIONER HANSON: Sure.

9 ACRS CHAIR SUNSERI: So I'd like, if I 10 could, I'd like to offer a non-I&C professional 11 perspective on this topic. And I may be outside my 12 swim lane on this, and Charlie can correct me, but you 13 know, I think the Agency has done a good job of 14 identifying all the issues that are bounded around this 15 topic.

16 And there's a program called the Integrated 17 Action Plan that is updated and maintained that has 18 kind of all the issues in one place, and the Agency 19 is systematically working through those things. And 20 that's how we get involved in these activities as they 21 review things and come through this Integrated Action 22 Plan, then we get involved with it.

23 And so I think that plan is progressing 24 quite nicely, and it's probably nearing the maintenance 25

61 mode of performance here. But that, like I said, this 1

is just a non-I&C professional view on that, and I'll 2

yield now.

3 COMMISSIONER HANSON: Thank you, Chairman 4

Sunseri. But while I have you, I want to close with 5

one last question. In the ACRS's report from this past 6

October regarding Part 53 licensing and regulation of 7

advanced nuclear reactors, there's a paragraph at the 8

end that caught my attention on fusion reactors. And 9

I thought your comments about the potential application 10 of a to be developed Part 53 to those fusion reactors 11 was really interesting.

12 But I wanted to get your thoughts on, and 13 various folks are out there in the fusion community 14 are also talking about potential application of Parts 15 20 and 30 and wanted to get your thoughts on that as 16 well.

17 ACRS CHAIR SUNSERI: Thank you for that 18 question. So Part 53 with respect to fusion reactors, 19 our comment on that is we seek -- and there's a lot 20 of debate, I think, in the industry about how much 21 regulation is needed on the fusion reactors. But we 22 see there's enough, I'll call, lack of better words, 23 I'll say hazards associated with operation of fusion 24 reactors that can create concerns for public that we 25

62 feel need to be addressed. And so we are prompting 1

that those kind of issues be taken up in Part 53.

2 COMMISSIONER HANSON: Okay, thank you, 3

Chairman.

4 CHAIRMAN SVINICKI: Thank you very much, 5

Commissioner Hanson. And perhaps this -- my question's 6

built a bit on what my colleagues have been asking about, 7

not surprisingly, but maybe slightly different angle 8

on some of these. Let me begin where Commissioner 9

Hanson left off on the ACRS involvement as the 10 provisions of Part 53 take shape. And also I think 11 there's some connective tissue with the lessons learned 12 letter report on the aspects of the review of advanced 13 reactors.

14 And I, the staff has been, and I think been 15 encouraged by the Commission, but also intended to take 16 a little bit of a more iterative approach to the 17 development of the draft language for Part 53, just 18 given the enormity of what they're trying to take on 19 here.

20 And I think that that, or I'm optimistic 21 that that will serve them well because they won't get 22 too far down finishing brush strokes on something that 23 then they get feedback and get feedback and realize 24 that they have to go about it a very different way.

25

63 But as a result the ACRS's engagement, you 1

know, in my view probably shouldn't wait for a proposed 2

rule itself because the staff would be pretty far down 3

the road. Chairman Sunseri, can you talk a little bit 4

about how the ACRS intends to structure or approach 5

its engagement on the broad kind of lessons learned 6

from advanced reactors reviews, and then folding some 7

of those insights into your engagement with the NRC 8

staff on their development of Part 53?

9 ACRS CHAIR SUNSERI: Thank you for the 10 question. Well, we see Part 53 as an important rule 11 in the future and so we want to be engaged with that, 12 and we've had early engagement.

13 We actually have a member that is assigned 14 a lead for us in this area, Dr. Bley is following this 15 area pretty closely for us, and so we have staff members 16 also that work with, across the aisle as they would 17 say with the NRR to keep up with things. And we expect 18 that as activities progress, that we -- and we have 19 requested for early on engagement, we think that is 20 important.

21 And as an independent committee, we have 22 to be a little cautious about how early we get involved 23 and what kind of involvement we are with, because we 24 don't want to become so part of the process that we 25

64 lose our objectivity to evaluate it at the end.

1 CHAIRMAN SVINICKI: Well, thank you for 2

that caution. But I -- the staff will need to develop 3

and cover some new ground here, so I think that having 4

the benefit of some perspectives, given the vast 5

experience of a lot of the ACRS members, will be helpful.

6 And I'm confident that between the staff and the ACRS 7

members, you can strike the right balance there.

8 ACRS CHAIR SUNSERI: If you would like to 9

recognize Member Bley, he may be able to provide some 10 additional details for you.

11 CHAIRMAN SVINICKI: Certainly. Dennis, 12 did you want to chime in?

13 ACRS MEMBER BLEY: Yes, I do. Thank you 14 very much, Chairman. Yeah, a couple of things with 15 respect to what you raised with Commissioner Hanson's 16 questions. I think on Part 53, we're just beginning 17 to interact with the staff. We have a meeting coming 18 up, I think it's in January or February, on the fusion 19 in the Part 20 and 30, the rad protection and the 20 by-product where I think we even mention tritium in 21 our last letter report. We'll be focusing on those 22 and urging the staff to.

23 But fusion's going to be kind of tricky.

24 It's, I'm not sure how well that's going to integrate 25

65 with the rest of Part 53. So we'll be talking with 1

the staff and probably with you folks along the way.

2 You mentioned the role of lessons learned 3

in Part 53, and I think that's important. We've already 4

been pulling that into the beginnings of our reviews 5

of the new design certs that'll be coming in on new 6

reactors and raising those issues. So they're 7

beginning to feed in that way first. And we've pushed 8

on this and it seems that the same people on the NRC 9

staff who will be developing Part 53 will be heavily 10 involved in those other activities. So I think we'll 11 get good cross-fertilization through that path.

12 So we agree with the issues you raised, 13 and I think we'll be following those and urging the 14 staff to be proactive in looking into these areas in 15 great detail.

16 CHAIRMAN SVINICKI: Thank you for that, 17 that's helpful. And I won't project onto Commissioner 18 Hanson's question, but I will just say for myself on 19 the fusion approach, coming at it as an individual, 20 my view was it may be the world's least comfortable 21 fit to have fusion in there, but if you scope it out 22 before you start, then you don't reach that conclusion.

23 And if you try to have it in, given the 24 early stages that the staff is at, I felt like maybe 25

66 you would discover it doesn't have a good home in Part 1

53. But you don't know if it washes out before you 2

even explore that. So I just want to say that's how 3

tepid my conclusion was. It was really based on more 4

procedural just awareness than anything else. So I 5

share the notion that it may ultimately not have a good 6

home there, but we don't know that now.

7 And I did want to turn to Dr. Rempe on the 8

passing mention in the letter report on the 9

discontinuous -- the discontinuation of access to the 10 Halden reactor. And of course that's not just for NRC, 11 that's for the global research community, given the 12 decision about not extending the operation of that 13 facility.

14 I noticed in an ACRS letter report on a 15 topical report on fuels was mentioned again about that, 16 that may severely complicate the ability for fuel 17 developers to submit the kind of data that they would 18 need. And I know that going forward, this'll be much 19 on the mind of the ACRS. But Dr. Rempe, was there --

20 I've also heard from others that say, I don't know, 21 maybe not waiting all the way for the Versatile Test 22 Reactor but, or truly new capacity.

23 But that this issue of the loss of Halden 24 is, from some they portray it as more manageable than 25

67 others. Nobody's thrilled about it in the research 1

community. Could you speak to that? Is this, you 2

know, a real kind of a deep concern for the ACRS? I'm 3

putting you on the -- part of the continuum of people 4

who find this severely problematic.

5 VICE CHAIR REMPE:

Thank

you, 6

Commissioner, for that question. My colleagues on the 7

ACRS will probably acknowledge that I'm the one who 8

often brings this up because that topic is near and 9

dear to my heart. With respect to the capability of 10 having a thermal test reactor, which is what the Halden 11 reactor was, the Versatile Test Reactor will be a fast 12 reactor if it is -- or if it is actually built, which 13 is down the road a bit.

14 But we do have in the world other reactors 15 that have loops that could probably accomplish much 16 of the mission of the Halden reactor. For example, 17 there's the BR2 in Belgium and there's the ATR here 18 in the US. But what we lack is the capabilities with 19 respect to instrumentation and the ease at which it 20 was performed at Halden because of their standardized 21 test.

22 With respect to the instrumentation, 23 Halden had some very unique capabilities. They could 24 in-pile, in situ measure or provide data for thermal 25

68 conductivity degradation, which is very important in 1

understanding how well the fuel is able to transfer 2

its heat. And they had other capabilities, in-pile 3

crack growth. There's a host of these things that they 4

had developed and were using regularly which have been 5

not transferred outside the Halden reactor with such 6

ease.

7 I know, before I retired from INL and I 8

think it continues that there are efforts to try and 9

develop those capabilities, but it's not been 10 demonstrated that they have that yet at this time.

11 I know that the Jules Horowitz, which is being 12 constructed in France, was also trying to develop the 13 capability.

14 And I, again, I know people are trying to 15 do it, but it is a capability that's very important 16 when we think about the HALEU or the accident tolerant 17 fuel and you want to have high-burnup data. -- you 18 want to have that kind of data. You need to have 19 something like Halden.

20 So I do hope -- we have a meeting scheduled 21 in the next couple of months here to hear what the 22 staff's plans are to address that capability, and it 23 is an international problem. And I anticipate that 24 the staff will be giving their ideas on an international 25

69 solution to that problem.

1 Does that help?

2 CHAIRMAN SVINICKI: Yes, thank you.

3 That's very helpful. And I would just say, even though 4

my background is not really as an experimenter, I know 5

another benefit of the long-term access to something 6

like ATR or to Halden is the confidence one has in the 7

comparison.

8 Because basically you've gone back to the 9

same machine and you've run a different parameter or 10 something like that. The comparability over the course 11 of, for ATR or Halden over the course literally decades 12 really brings a certain pedigree to the research work.

13 So thank you for that.

14 And I'll just close with one comment that 15 was triggered by the interesting question of 16 Commissioner Wright, which had to do with the, as a 17 committee of experts spread across the country, what 18 elements of the virtual work would you like to carry 19 forward. I appreciate that certainly elements of doing 20 some remote gatherings would work well for you.

21 I think another potential benefit of 22 retaining some element of working in a distributed way, 23 if indeed you all have found that you can work that 24 way, is that as the committee approaches whatever its 25

70 next solicitation for membership might be, I think that 1

folks may be academics or researchers or those who are 2

tied maybe or cannot easily accommodate the need to 3

fly to Maryland ten times a year.

4 You may be able to get a more diverse set 5

of applicants. You could get diversity across 6

background and competencies and perhaps just diversity 7

in the very traditional sense. That may be -- so I 8

would just plant the seed of in your next solicitation 9

making explicit whatever these revised practices are 10 going to be, because you may have some wonderful 11 applicants that previously were put off by the need 12 to have all your meetings in person.

13 So I just note that as perhaps a potential 14 benefit to come out of all this. And with that, I will 15 turn over to Commissioner Baran.

16 COMMISSIONER BARAN: Thanks, Chairman.

17 Walter, thanks for your discussion of the NuScale design 18 certification review and the issues that ACRS flagged 19 there as areas of concern or ongoing work. I'd like 20 to ask about a few of those.

21 On the boron dilution issue, what would 22 the staff need to require at the combined license stage 23 to address that issue?

24 ACRS MEMBER KIRCHNER:

Thank

you, 25

71 Commissioner. Well, I think the consensus of the 1

Committee would be that we would like to see a much 2

more detailed analysis of, and I'm being a little bit 3

repetitive here, of my answer to Commissioner Wright, 4

that they explore the state of the system and the options 5

that are available. For example, I flagged in my 6

presentation the importance of the chemical volume 7

control system. That is the preferred option that the 8

applicant identified to recover.

9 Now, consider the fact that if that 10 system's not available, what is the backup approach?

11 And that likely would be to use the containment fill 12 and drain system. But the containment fill and drain 13 system is kind of an indirect way to get boron where 14 you want it. You're pushing on a rope, so to speak.

15 Whereas the CVCS system would extract from 16 the downcomer, inject into the riser, as well as spray 17 into the pressurizer. And that drainage from the 18 pressurizer would preferentially go to the downcomer.

19 So that's the kind of space that I think we feel needs 20 to be further explored. It is doable. It's not a 21 showstopper. But it certainly is a matter of concern.

22 And let me perhaps fall back on a little 23 history. I did cite a couple of agency-sponsored 24 contractor reports that are on my slides. The result 25

72 of the existing fleet looking at the boron dilution 1

issues for a small break LOCA led to among other things 2

the institution of administration concerns -- controls, 3

excuse me, at the plants.

4 And the one thing you don't want to do in 5

a situation like that with the existing fleet is restart 6

the reactor coolant pumps. So that's why I highlighted 7

previously our concern about can you get in a situation 8

where the equivalent here for the NuScale design would 9

be restoring natural circulation.

10 And so that is the space we feel that needs 11 to be explored more thoroughly. Once you've done that, 12 then you can look at the systems that are available 13 and identify the best path to recover the plant and 14 put it in a safe condition.

15 COMMISSIONER BARAN: Okay, thanks. You 16 also discussed another issue, which was the possibility 17 that the reactor could return to criticality after being 18 shut down if the most impactful control rod fails to 19 insert. The NRC staff concluded that the risk 20 associated with this event was negligible 21 Can you walk us through ACRS's view of 22 whether the risk is negligible?

23 ACRS MEMBER KIRCHNER: Well, the scenario 24 that they looked at was, actually I've touched on it, 25

73 they looked at the situation when the core is highly 1

borated. In neutronic terms, you would say it's black.

2 The boron concentration is much higher than it would 3

be under normal operation.

4 They looked at a scenario where you used 5

a containment fill and drain system. The water would 6

spill into the downcomer, and you would have a very 7

slow rate of entry of deborated water into the core.

8 Probably a good deal of mixing. And if in that 9

circumstance you did return to criticality, it would 10 likely be benign. Because the rest of the core is 11 essentially black and you wouldn't get any feedback 12 effects from the core.

13 So that would be a benign incident. I was 14 hinting at this when I said that sometimes when you 15 do a bounding calculation like that, maybe the answer 16 or the concern is in between. So, and what I mean by 17 that is so say you restore the level into the system, 18 the boron, it's -- you have deborated water but the 19 concentration isn't -- is sufficient still to retain 20 the core subcritical.

21 But then you get this rapid influx of 22 deborated water. Then that's a different scenario, 23 and we haven't seen that one analyzed. And the results 24 of that may also be benign. And again, going back to 25

74 the history, these same kinds of analyses were done 1

for the existing fleet, and they were able to 2

demonstrate whether or not it would result in core 3

damage or not. And the case was it would not.

4 COMMISSIONER BARAN:

Okay.

My 5

understanding is that ACRS members weren't unanimous 6

about whether this potential return to criticality is 7

ultimately acceptable. And I'm interested in hearing 8

the different views on that question.

9 And I know, Walter, if you want to kind 10 of present the discussions of, you know, is this 11 ultimately acceptable or not, or if folks just want 12 to chime in if they have kind of the different views 13 on that. I'm just interested in hearing the discussion 14 around.

15 ACRS MEMBER KIRCHNER: Well, I think I 16 should turn to, if I may, Commissioner Baran, may I 17 turn to my colleague Dr. Jose March-Leuba? He was our 18 lead on this particular focus area, and I would like 19 him to have an opportunity to present his views.

20 COMMISSIONER BARAN: Great, thanks.

21 ACRS MEMBER MARCH-LEUBA: Thank you, I 22 just turned my video on. There, it's coming. All 23 right. So I'll talk while -- there we are.

24 First, the question about the static 25

75 control rod and return to criticality which led to the 1

GDC 27 exemption is different than boron 2

redistribution. And I am of the agreement that 3

absolutely does not pose any safety significance 4

whatsoever. And our letter on the topic explains the 5

five different items why, so I won't bother you with 6

it. It's of no safety significance.

7 With respect to boron dilution, that's 8

completely different. Both the applicant and the staff 9

and even some of us when we talk keep trying to focus 10 on operator procedures that we will use to, in a nice 11 controlled way, recover the facility after they take 12 us to ECCS. That's not what I'm talking about.

13 What I'm talking about is once you are in 14 this condition where a lot of positive reactivity is 15 sitting in front of the core, you have -- the amount 16 of distilled water that you have in front of the core 17 is, at the worst case scenario, is 12 core volumes.

18 And all that water is eventually going to get into the 19 core. The question is how fast does it get in there, 20 does it have time to mix with all the boron that's in 21 there?

22 It's a very difficult problem, and 23 completely ignoring it by saying, surely it will mix, 24 why do I have to look at it, it's not very reassuring.

25

76 So the -- what I would expect that staff to do at the 1

COL review is, review from the applicant that they have 2

performed a systematic search for initiating events, 3

accidents, okay, like inadvertent actuations, like 4

operator errors, that could cause an accident.

5 So you have to look for those initiating 6

events and then analyze them and say this one doesn't 7

cause a problem, this one cause a problem. Because 8

when we were in the December of 2019 time frame with 9

the design as submitted, the position from the applicant 10 was there was no initiating event that could possibly 11 get that distilled water into the core.

12 When we looked into it, we found two. We 13 found two that actually were the natural progression 14 of the events. In the case of the small break LOCA 15 extremely worrisome transient. It would have been 16 possibly bad. And so I think we need to -- I'm not 17 saying that anything bad can happen to the core, I'm 18 saying that I don't see a systematic analysis to find 19 out if it can. And that needs to be performed.

20 And the reason we're suggesting to do it 21 at the COL stage is because all these initiating events 22 come from the balance of plan components, like CFD, 23 CVCS, which are not currently design. So at the COL 24 stage, we will know how many valves, how many pipes, 25

77 how many pumps, where are they located, what can go 1

wrong with them. Right now, we only have cartoons.

2 So it makes sense to delay this systematic search for 3

initiating events to that stage instead of now, because 4

we just don't have the information.

5 COMMISSIONER BARAN: That's helpful, 6

thank you very much. Thank you, Chairman.

7 CHAIRMAN SVINICKI: Well, again, on behalf 8

of the Commission, I want to thank all the members of 9

the ACRS for the presentations, for their hard work 10 throughout the course of the year, all of the letter 11 reports that they provided. And in the absence of any 12 of my colleagues seeking recognition, I think from our 13 commission to your committee, many happy holidays and 14 a happy new year. And perhaps we can enjoy your nice 15 potluck next time around.

16 All right, thank you all, and we are 17 adjourned.

18 (Whereupon, the above-entitled matter went 19 off the record at 11:48 a.m.)

20