ML25127A294

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Advanced Reactor Stakeholder Public Meeting - Final Master
ML25127A294
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Issue date: 05/07/2025
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Advanced Reactor Stakeholder Public Meeting May 8, 2025 Bridge line: 301-576-2978 Conference ID: 630033119#

Time Topic Speaker 10:00am-10:05am Opening Remarks NRC 10:05am-10:15am Research Supporting Human Factors Reviews for Advanced Reactors NRC 10:15am-10:35am Overview of RES technical reports on the use of ASME Section VIII Design Rules NRC 10:35am-11:05am Technology Inclusive Management of Safety Case (TIMaSC) Project Southern Company, LMNT Consulting 11:05am Public Comment Adjourn NRC

Opening Remarks

Advanced Reactor Program Highlights Updates and Recent Accomplishments:

  • 2/20 - Public Microreactor Workshop
  • 2/24 - Publication of New Microreactor Webpage
  • 2/26 - Completion of the Draft Safety Evaluation with Open Items for the Kemmerer Power Station Unit 1 Construction Permit Application
  • 3/31 - Long Mott Generating Station Construction Permit Application Received Upcoming Public Meetings:
  • 5/22 1:00 pm: Meeting on the Technical Report NEI 24-11, "Fire Brigade Staffing Analysis for Advanced Reactor Technologies."

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Research Supporting Human Factors Reviews for Advanced Reactors Niav Hughes Green, Ph.D.

Advanced Reactor Stakeholder Meeting May 8, 2025

Contact:

Niav.Hughes@nrc.gov 5

=

Background===

  • Three new human factors engineering (HFE) contractor reports released in April 2025
  • Provides technical basis and draft guidelines to support NRCs HFE reviews
1. Reviews of important human actions in achieving safety functions for small, advanced reactor designs
2. Reviews of facilities without main control rooms
3. Alternatives to full-scope, high-fidelity testbeds for HFE validation activities
  • Would potentially supplement review guidance in draft Interim Staff Guidance (ISG), Development of Scalable HFE Review Plans (DRO-ISG-2023-03*)

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Implications of Safety and Operational Features of Small Advanced Reactors and Alternative Risk Methods for HFE Reviews (Important Human Actions)

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  • The unique design and operational characteristics of small advanced reactors are likely to change the role of humans and the types of human actions important to managing safety functions.

Context:

  • Identify the implications of small, advanced reactor design characteristics on human performance.
  • Describe methods applicants may use to identify important human actions.
  • Define guidelines to support NRC HFE reviewers in assessing whether an applicants methods adequately model human actions important to safety.

Report Objectives:

7 Reference: OHara, J. (2025). Implications of Safety and Operational Features of Small Advanced Reactors and Alternative Risk Methods for Human Factors Engineering Reviews (BNL Technical Report No. 227636). Upton, NY:

Brookhaven National Laboratory. ML25090A258

Review of Reactor Facilities without Main Control Rooms ML25090A257

  • A traditional main control room (MCR) could potentially not be necessary for some small, advanced reactors to support normal operations or emergency management due to changes in the role of plant personnel.
  • Reactor monitoring and control could potentially be accomplished from simple panels either locally or remotely (OHara, Desaulniers, Green, Seymour, & DAgostino, 2021).

Context:

  • Identify when a traditional MCR could potentially not be necessary.
  • Identify workplace design alternatives to traditional MCRs.
  • Define guidelines to support reviews of workplace designs with and without an MCR.

Report Objectives:

8 Reference: OHara, J. (2025). Review of Reactor Facilities without Main Control Rooms (BNL Technical Report No. 227637). Upton, NY: Brookhaven National Laboratory. ML25090A257

Analytical and Performance-Based Evaluation Alternatives to Full-Scope, High-Fidelity Testbeds ML25090A259

  • Integrated System Validation (ISV) traditionally involves use of a full-scope, high fidelity testbed, but may not be cost-justified or practical for all anticipated advanced reactor designs.
  • Alternative bases may support performance-based acceptability determinations.

Context:

  • Identify the implications of not having a full-scope, high-fidelity testbed for HFE validation.
  • Identify analytical and performance-based test and evaluation methods that provide alternatives to full-scope, high fidelity testbeds.
  • Define guidelines to support reviewing HFE validation activities that use alternative methods.

Report Objectives:

9 Reference: OHara, J. (2025). Analytical and Performance-Based Evaluation Alternatives to Full-Scope, High-Fidelity Testbeds (BNL Technical Report No. 227577). Upton, NY: Brookhaven National Laboratory.

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Stay Informed about NRCs Human Factors Research Subscribe to Email Updates via NRCs GovDelivery Subscription Services https://service.govdelivery.com/accoun ts/USNRC/subscriber/new Category: Research Topic: Human Factors Research 10 QR Code for NRC GovDelivery Subscriptions https://service.govdelivery.com/accounts/USNRC/subscriber/new

Overview of RES Technical Reports on the use of ASME Section VIII Design Rules Joseph Bass May 8, 2025 11

OUTLINE Technical assessment on the use of ASME Section VIII design rules for advanced non-light water reactor components

- Comparison of Section VIII and Section III, Division 5

- Potential modifications of and additions to Section VIII for high-temperature nuclear applications 12

Technical Assessment on Use of Section VIII Motivation:

Increased interest from non-light water reactor vendors in adopting the Section VIII Code rules for nuclear components.

Office of Research Activity:

1.

A comparison between the Section III, Division 5 and Section VIII design rules in TLR-RES/DE/REB-2025-02 Evaluating the high temperature design rules and design space of Section III, Division 5 and Section VIII of the ASME Boiler & Pressure Vessel Code (ML25059A010). Published February 28, 2025.

2.

Methods to supplement Section VIII rules to address high temperature effects are discussed in TLR-RES/DE/REB-2025-02 Potential modifications or additions to the ASME Section VIII rules to provide greater confidence in the design of high temperature nuclear components. Publication anticipated in May 2025.

These reports are primarily focused on design rules within the ASME Code 13

TLR-RES/DE/REB-2025-02 Evaluating the high temperature design rules and design space of Section III, Division 5 and Section VIII of the ASME Boiler & Pressure Vessel Code (ML25059A010)

This report considers the applicability of the ASME BPVC Section VIII for the design and construction of components for high temperature nuclear reactors in two ways:

1. Comparison of Section VIII to the endorsed methodology in Section III, Division 5

- Design methodology differences between the Codes

- Bree cylinder example problem 2.

Discussion of failure modes which are not considered in Section VIII Rules Considered

1.Section III, Division 5: Class A
2.Section VIII Division 1
3.Section VIII Division 2: Part 4, Class 2
4.Section VIII Division 2: Part 5, Class 2 14

Comparison of III-5 to Section VIII Key design differences between the Section III and Section VIII rules include:

1. Design life philosophy Section VIII applies an indefinite life concept (time-independent allowable stresses)

Section III, Division 5 includes time-dependent allowable stresses

2. The definition of the allowable stresses
3. Failure modes addressed in the design rules
4. Weld design rules
5. Qualified materials
6. Scope of components 15

Example Problem: Bree Cylinder 16 The standard Bree cylinder is used as a representative problem to compare the Section III and Section VIII permissible design space.

A parametric study was conducted with 5 independent variables:

1. Primary stress, P
2. Secondary Stress, Q
3. Temperature, T
4. Design life, life
5. Hold time, hold

Design Space: Temperature Effect 17 Increasing temperature At higher temperatures,Section III, Division 5 has a smaller permissible design space when compared to the Section VIII

Design Space: Hold Time Effect 18 Increasing hold time At longer hold times,Section III, Division 5 has a smaller permissible design space when compared to the Section VIII

Design Space: Design Life Effect 19 Increasing design life At higher design lives,Section III, Division 5 has a smaller permissible design space when compared to the Section VIII

Summary of TLR-RES/DE/REB-2025-02 20

1. This report analyzes the design rules in Section VIII and compares those rules to Section III, Division 5.

This uses the Section III and Section VIII rules are applied to a Bree cylinder and the results show that:

Generally, at longer design live,Section III is more restrictive Generally, at higher temperatures,Section III is more restrictive Generally, at longer hold time,Section III is more restrictive

2. The key differences analyzed in this report revolve around high-temperature effects (high-temperature failure modes/effects).
3. Several other key differences are identified including: 1) Permissible materials; 2)

Applicable components; 3) Welding rules.

TLR-RES/DE/REB-2025-07 Potential modifications or additions to the ASME Section VIII rules to provide greater confidence in the design of high temperature nuclear components This report documents potential additional design criteria to Section VIII rules to provide increased confidence in the long-term reliability of high temperature components.

Design considerations for application of high-temperature Section VIII rules:

1. The definition of allowable stresses
2. The lack of high temperature fatigue data
3. The lack of creep-fatigue design rules
4. The strength of weldments in the creep regime.

To address these considerations, several specialized criteria are considered in this report:

1. Negligible load criteria
2. Negligible creep criteria
3. Negligible fatigue criteria
4. High-temperature weld design and inspection 21 Creep damage Fatigue damage

Conclusions

1. The Section VIII rules do not account for some high-temperature failure modes which may be present for high-temperature nuclear components (e.g.,

high-temperature fatigue effects, and creep effects in welds).

2. Compared to the endorsed methodology in III-5, the Section VIII rules generally allow for higher stresses at long times and high temperatures.
3. Analysis, such as the analysis shown in the second report (e.g., negligible creep and negligible fatigue criteria), may provide confidence that the Section VIII rules are appropriate for high-temperature nuclear applications.

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Questions 23

Brandon M Chisholm, PhD - Southern Company Steve Nesbit - LMNT Consulting Nuclear Regulatory Commission (NRC) Advanced Reactor Stakeholder Meeting May 8, 2025 Technology Inclusive Management of Safety Case (TIMaSC) Project

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Outline & Purpose of Todays Presentation

  • Provide refresher on TIMaSC effort (Chisholm)
  • Update NRC and stakeholders on project status since June 2024 (Chisholm)
  • Discuss White Paper annotated outline for information and feedback (Nesbit)
  • Socialize the project with the broader advanced reactor community 25

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Introduction / Overview

  • Southern Company, the Department of Energy (DOE), and members of the advanced reactor industry are working on the fourth effort in a series to develop guidance for advanced non-light water reactors applicants/licensees
  • The approach in the guidance is technology inclusive, risk-informed (RI), and performance-based (PB)
  • The intended users of all guidance documents are applicants or licensees under 10 CFR Part 50 or Part 52
  • As users of previous guidance documents (e.g., LMP/NEI 18-04, TICAP/NEI 21-07) approach the operational phase of their plants lifecycles, additional insight is being gained regarding key areas of uncertainty within the associated regulatory framework(s) 26

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Some RI and/or PB initiatives for Advanced Reactors (not exhaustive)

  • Advanced Reactor Content of Application Project (ARCAP): DANU-ISG-2022-01 through -09
  • Technology Inclusive Risk Informed Change Evaluation (TIRICE): NEI 22-05, currently under NRC review for endorsement
  • Risk-Informed Performance-Based Emergency Planning: NEI 24-05, currently under NRC review for endorsement
  • Draft proposed NRC security rule on Alternative Physical Security Requirements for Advanced Reactors
  • NRC siting guidance: draft revisions to RG 4.7
  • Advanced Reactor Construction Oversight Process (ARCOP)
  • Advanced Reactor Oversight Program (AROP[?])

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TIMaSC Need

  • LMP and TICAP establish the basis for (i) the development of a safety case for a non-LWR applicant and (ii) the documentation of that safety case in the Safety Analysis Report, respectively
  • ARCAP provided additional information about the broader advanced reactor licensing basis

- Some elements of the licensing basis are linked to the safety case developed using the LMP methodology, while some are not

  • Once a licensing basis is accepted by the NRC and the operating license is granted, TIRICE establishes a methodology for determining if prior NRC approval is required for certain changes to the facility

- Analogous to 10 CFR 50.59 but consistent with the risk-informed, performance-based safety case for advanced reactors

  • Additional guidance related to the maintenance of the broader licensing basis would be beneficial (at least) or is necessary

- TIMaSC is primarily focused on the operational phase of an advanced reactor 28

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TIMaSC Objectives and Products

  • Clarify how an RIPB safety case fits into the licensing basis for an advanced reactor under the existing NRC regulatory frameworks

- Describe relationships using a Network Diagram

  • Identify how changes to the RIPB safety case can be managed in a right-sized manner (i.e., such that the regulator can confirm reasonable assurance of adequate protection while optimizing focus on non-trivial changes)

- Provide guidance (and/or considerations) for change control

  • Prioritize future work to further reduce uncertainty and risk associated with the licensing of advanced reactors

- Develop a RIPB Regulatory Framework Roadmap report for stakeholder alignment

  • Socialize the outcomes, results, and insights with key stakeholders (including regulators and industry) to maximize alignment

- Interactions in public meetings, industry working groups, and other venues 29

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Areas of Particular Interest

  • Opportunities outside of the scope of NEI 18-04 for advanced non-light water reactors (LWRs) to meet regulations using RIPB approaches
  • Changes outside the scope of TIRICE (NEI 22-05)

- New information (changes to the state of knowledge)

- Considerations beyond determining whether a license amendment is required or not 30

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31 How are elements of the licensing basis linked (or not linked)?

SNM = Special Nuclear Material ARCOP = Advanced Reactor Construction Oversight Program PRA = Probabilistic Risk Assessment IDP = Integrated Decision-making Process

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32 What kinds of changes should be considered?

As reflected by NEI 22-05 (and 10 CFR 50.59),

not all changes are of equal significance from a safety perspective DID = Defense-in-Depth IDP = Integrated Decision-making Process

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High-Level TIMaSC Timeline

  • Project on hold since mid-2024
  • 2025 - develop White Paper, obtain initial feedback from NRC

- Interested in any initial feedback on draft White Paper outline (following slides)

- White Paper will be used to inform scope and content of guidance (more on next slide)

- Transmit paper to NRC August 2025 for informal review and comment

  • 2025-2026 - Develop draft guidance, carry out tabletop exercises, obtain NRC feedback on draft guidance

- Submit guidance to the NRC for formal review and endorsement May 2026 33

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TIMaSC White Paper

  • The White Paper will further define TIMaSC scope and evaluate issues for inclusion in the eventual TIMaSC guidance document
  • The following slides address the key sections of the White Paper, as currently envisioned

- Caveat: the draft outline for the White Paper is a snapshot and the organization of the document will likely change during development of the paper itself

  • Seeking NRC input on the White Paper scope now and as the document develops 34

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White Paper Outline

  • Section 1 - Introduction

- Plans are for this section to address the following areas

>> Purpose and scope

  • Develop a shared understanding of the key elements of guidance on management of the RIPB licensing basis
  • Assessment of existing processes and programs as well as new and developing tools
  • Focus on the interplay between PRA changes and changes to the licensing basis

>> Perspective on RIPB regulation

>> Background - relatively recent and pertinent industry and NRC work 35

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White Paper Outline (cont.)

  • Section 2 - Advanced Reactor RIPB Licensing Basis

- Plans are for this section to address the elements and relationships of the advanced non-LWR RIPB licensing basis

>> Starting point for advanced reactor licensing basis is the list of elements in ARCAP Roadmap ISG (DANU-ISG-2022-01)

>> Additional insights from the Southern Company white paper entitled Follow-on RIPB Implementation Guidance Needed for Advanced Non-Light Water Reactors (ML21237A051)

>> Incorporation of deterministic elements 36

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White Paper Outline (cont.)

  • Section 3 - Facility Changes to Which NEI 22-05 Is Applicable

- Plans are for this section to address specific measures to be taken for facility changes once the need for a license amendment is determined (either way)

- This includes assessing impacts on definition, frequency, and consequences of LBEs; defense-in-depth evaluation; reliability and capability targets; special treatments; etc.

  • Section 4 - Facility Changes to Which NEI 22-05 Is Not Applicable

- NEI 22-05 does not apply to changes that are controlled by other more specific requirements and criteria established by regulation

- Examples include changes to quality assurance, physical security, and emergency plans

- Plans are for this section to identify specific areas and associated requirements.

  • Section 5 - New Information

- Plans are for this section to address processes to be followed for different types of new information 37

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White Paper Outline (cont.)

  • Section 6 - PRA

- Plans are for this section to address the following areas

>> Evolution of Advanced Reactor PRAs

>> Role of PRA in Establishing the Licensing Basis under NEI 18-04

>> Non-LWR PRA Standard and Supporting Peer Reviews

>> PRA Configuration Control, Updates and Change Management

>> New information

>> Cautions and Limitations

- The section will address considerations for managing impacts of changes to the PRA on the advanced non-LWR RIPB licensing basis 38

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White Paper Outline (cont.)

  • Section 7 - Other Topics

- Plans are for this section to address specific topic areas that may not be covered adequately in other sections, and which may not ultimately be addressed by TIMaSC

- Examples include

>> Risk-informed Technical Specifications

>> Reliability Assurance Program

>> Reactor Oversight Process

>> Fire Protection

>> Risk Metrics

>> Considerations Prior to Operation

>> Adding Units to a Site

  • Section 8 - Summary 39

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Questions and General Discussion 40

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Abbreviations Abbreviation Definition ARCAP Advanced Reactor Content of Application Project ARCOP Advanced Reactor Construction Oversight Program CFR Code of Federal Regulations DID Defense in Depth DOE Department of Energy IDP Integrated Decision-Making Process ISI In-service Inspection IST In-service Testing LMP Licensing Modernization Project LWR Light Water Reactor NEI Nuclear Energy Institute NRC Nuclear Regulatory Commission PRA Probabilistic Risk Assessment 41

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Abbreviations (cont.)

Abbreviation Definition SAR Safety Analysis Report SNM Special Nuclear Material TICAP Technology Inclusive Content of Application Project TIMaSC Technology Inclusive Management of Safety Case TIRICE Technology Inclusive Risk-Informed Change Evaluation 42

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PUBLIC COMMENT PERIOD PUBLIC COMMENTS 44

CLOSING REMARKS CLOSING REMARKS 45

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