RC-12R-C1\

ASME/ANS RA-S-1.4-2021

Probabilistic Risk Assessment Standard for Advanced Non- Light Water Reactor Nuclear Power Plants

AN AMERICAN NATIONAL STANDARD

Date of Issuance: February 8, 2021

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Copyright © 2021 by

THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS

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CONTENTS

Foreword iii

Correspondence With the ASME/ANS Joint Committee on Nuclear Risk Management iv

Committee Rosters vii

SECTION 1 INTRODUCTION 1

Section 1.1 Objective 3

Section 1.2 Scope 3

Section 1.3 Requirements for Different Design-Life Cycle Stages 4

Section 1.4 Structure for PRA Requirements 5

Section 1.5 Applicability of PRA Technical Elements 9

Section 1.6 PRA Configuration Control 9

Section 1.7 Peer Review Requirements 9

Section 1.8 Addressing Different PRA Scopes 9

Section 1.9 Determining Risk-Significant Items 10

Section 1.10 Screening Criteria 13

Section 1.12 Derivation of Technical Requirements 16

Section 1.13 References 17

SECTION 2 ACRONYMS AND DEFINITIONS 19

Section 2.1 Acronyms 21

Section 2.2 Definitions 22

Section 2.3 References 34

SECTION 3 RISK ASSESSMENT APPLICATION PROCESS 35

Section 3.1 Overview of Application Process 37

Section 3.2 Range of PRA Applications Considered for This Standard 40

Section 3.3 Step-by-Step Approach to PRA Applications 40

Section 3.4 References 46

SECTION 4 RISK ASSESSMENT TECHNICAL REQUIREMENTS 47

Section 4.1 Purpose 49

Section 4.2 Use of Expert Judgment 49

Section 4.3 Technical Requirements 51

Nonmandatory Appendices

POS.1 Notes Associated With Plant Operating State Analysis 57

IE.1 Notes Associated With Initiating Events Analysis 69

ES.1 Notes Associated With Event Sequence Analysis 81

SC.1 Notes Associated With Success Criteria Development 90

SY.1 Notes Associated With Systems Analysis 101

HR.1 Notes Associated With Human Reliability Analysis 117

DA.1 Notes Associated With Data Analysis 129

FL.1 Notes Associated With Internal Flood PRA 158

FL.2 Explanatory Content Associated With Internal Flood PRA 161

F.1 Notes Associated With Internal Fire PRA 196

1. Notes Associated With Seismic PRA 222

2. Explanatory Material Associated With Seismic PRA 243

HS.1 Notes Associated With Hazards Screening Analysis 253

HS.2 Notes Associated With Hazards Screening Analysis High Level Requirements 256

1. Notes Associated With High Winds PRA 280

2. Explanatory Material Associated With High Winds PRA 303

i

XF.1 Notes Associated With External Flooding PRA 332

XF.2 Explanatory Material Associated With External Flooding PRA 350

1. Notes Associated With Other Hazards PRA 372

2. Explanatory Material Associated With Other Hazards PRA 376

ESQ.1 Notes Associated With Event Sequence Quantification 388

MS.1 Notes Associated With Mechanistic Source Term Analysis 396

RC.1 Notes Associated With Radiological Consequence Analysis 417

RC.2 Additional Information For Radiological Consequence Analysis 420

RI.1 Notes Associated With Risk Integration 431

RI.2 An Example of Risk Integration Using Relative Significance 433

SECTION 5 PRA CONFIGURATION CONTROL 439

1. Purpose 441

2. Objective 441

Nonmandatory Appendix 444

CC.1 Notes Associated With Configuration Control 444

SECTION 6 PEER REVIEW 445

Section 6.1 Purpose 447

Section 6.2 Peer Review Team Composition and Personnel Qualifications 448

Section 6.3 Review of PRA Elements to Confirm the Methodology Used and Implementation 448

Section 6.4 Expert Judgment 449

Section 6.5 PRA Configuration Control 449

Section 6.6 Peer Review Documentation 449

SECTION 7 NEWLY DEVELOPED METHODS 451

Section 7.1 Introduction 453

Section 7.2 Objectives and Technical Requirements for Newly Developed Methods (NM) 453

Nonmandatory Appendix 456

NM.1 Notes Associated With Newly Developed Methods 456

(All references are distributed within the above sections.)

FOREWORD

The American Society of Mechanical Engineers (ASME) Board on Nuclear Codes and Standards (BNCS) and the American Nuclear Society (ANS) Standards Board mutually agreed in 2004 to form the Nuclear Risk Management Coordinating Committee (NRMCC). NRMCC was chartered to coordinate and harmonize standards activities related to probabilistic risk assessment (PRA) between ASME and ANS. A key activity resulting from NRMCC was the development of PRA standards structured around the Levels of PRA (i.e., Level 1, Level 2, Level 3) to be jointly issued by ASME and ANS. In 2011, ASME and ANS decided to combine their respective PRA standards committees to form the ASME/ANS Joint Committee on Nuclear Risk Management (JCNRM).

In 2006, ASME BNCS established the New Reactor Task Group under the Committee on Nuclear Risk Management (CNRM) to evaluate the need for codes and standards to support the design, construction, licensing, and operation of advanced non-light water reactor (non-LWR) nuclear power plants (NPPs). Following the formation of JCNRM, the New Reactor Task Group is now known as the ASME/ ANS JCNRM Advanced Non-LWR PRA Standard Writing Group (Non-LWR WG). The charter of the Non- LWR WG is to develop recommendations to JCNRM on requirements for the performance of PRAs for advanced non-LWRs. The expected applications of such PRAs include input to licensing and design decisions such as selection of licensing-basis events and safety classification of equipment, satisfaction of U.S. Nuclear Regulatory Commission (NRC) PRA requirements for advanced non-LWRs, and support of risk-informed applications for advanced non-LWR NPPs. With the concurrence of JCNRM, the Non-LWR WG decided early on that a new PRA standard was needed to support a broad range of applications for advanced reactor designs.

To support a diverse mixture of reactor concepts, including high-temperature gas-cooled reactors, liquid metal-cooled fast reactors, molten salt reactors, microreactors, and small modular reactors, CNRM decided early on to develop this new PRA standard on a reactor-technology-neutral basis using established technology-neutral risk metrics common to existing light water reactor (LWR) Level 3 PRAs. Such risk metrics include frequency of radiological consequences (e.g., dose, health effects, and property damage impacts). To support a wide range of applications defined by the non-LWR stakeholders, the scope of this Standard is very broad and is comparable to a full-scope Level 3 PRA for an LWR with a full range of plant operating states and hazards. Because some of the advanced non-LWR designs supported by this Standard include modular reactor concepts, this Standard includes requirements that support an integrated risk of multi-reactor facilities including event sequences involving two or more reactors or radionuclide sources concurrently.

In 2013, the JCNRM issued a trial use for the pilot application (TUPA) version of this Standard as ASME/ ANS-RA-S-1.4-2013. This trial use version was extensively piloted in the development of a number of advanced non-LWR PRAs that were under development and being built around the world. These advanced non-LWR PRA pilots included one to support the licensing of the HTR-PM pebble bed reactor plant in the Republic of China and a modernization of the GE PRISM PRA, which piloted a major fraction of this Standard’s technical requirements in 2018. The experience with pilot applications of this Standard has been extended to support the development of the Traveling Wave and Molten Chloride Fast Reactor at TerraPower, the pebble bed HTGR under development at X-Energy, the Versatile Test Reactor being developed for the U.S. Department of Energy, the Fluoride Cooled High Temperature Reactor at Kairos, the eVinciTM Micro Reactor at Westinghouse, and Advanced HTGRs under development in Japan. The purpose of this version of this Standard is to capture the lessons learned from these pilot applications and to incorporate improvements that have been made in other PRA standards that are applicable to advanced non-LWRs.

In preparing the technical requirements in this Standard, the Non-LWR WG made use of applicable source material from PRA standards that have been developed for LWRs including ASME/ANS RA-Sb-2013, “Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications,” as well as Trial Use PRA standards developed by ASME and ANS for Low-Power-and- Shutdown PRA, Level 2 PRA, and Level 3 PRA.

This publication, the 2021 edition of Probabilistic Risk Assessment Standard for Advanced Non-Light Water Reactor Nuclear Power Plants, was approved by the ASME Board on Nuclear Codes and Standards and the ANS Standards Board. ASME/ANS RA-S-1.4-2021 was approved by the American National Standards Institute on January 28, 2021.

CORRESPONDENCE WITH THE ASME/ANS JOINT COMMITTEE ON NUCLEAR RISK MANAGEMENT

General. ASME Standards are developed and maintained with the intent to represent the consensus of concerned interests. As such, users of this Standard may interact with the Committee by requesting interpretations, proposing revisions or a case, and attending Committee meetings. Correspondence should be addressed to:

Secretary, ASME/ANS Joint Committee on Nuclear Risk Management The American Society of Mechanical Engineers

Two Park Avenue

New York, NY 10016-5990

https://go.asme.org/Inquiry

Proposing Revisions. Revisions are made periodically to the Standard to incorporate changes that appear necessary or desirable, as demonstrated by the experience gained from the application of the Standard. Approved revisions will be published periodically.

The Committee welcomes proposals for revisions to this Standard. Such proposals should be as specific as possible, citing the paragraph number(s), the proposed wording, and a detailed description of the reasons for the proposal, including any pertinent documentation.

Interpretations. Upon request, the ASME/ANS Joint Committee on Nuclear Risk Management (JCNRM) Standards Committee will render an interpretation of any requirement of the Standard. Interpretations can only be rendered in response to a written request sent to the Secretary of JCNRM.

Requests for interpretation should preferably be submitted through the online Interpretation Submittal Form. The form is accessible at https://go.asme.org/InterpretationRequest. Upon submittal of the form, the Inquirer will receive an automatic e-mail confirming receipt.

If the Inquirer is unable to use the online form, he/she may mail the request to the Secretary of JCNRM at the above address. The request for an interpretation should be clear and unambiguous. It is further recommended that the Inquirer submit his/her request in the following format:

Requests that are not in the format described above may be rewritten in the appropriate format by the Committee prior to being answered, which may inadvertently change the intent of the original request.

Moreover, ASME does not act as a consultant for specific engineering problems or for the general application or understanding of the Standard requirements. If, based on the inquiry information submitted, it is the opinion of

the Committee that the Inquirer should seek assistance, the inquiry will be returned with the recommendation that such assistance be obtained.

ASME procedures provide for reconsideration of any interpretation when or if additional information that might affect an interpretation is available. Further, persons aggrieved by an interpretation may appeal to the cognizant ASME Committee or Subcommittee. ASME does not “approve,” “certify,” “rate,” or “endorse” any item, construction, proprietary device, or activity.

Attending Committee Meetings. The JCNRM regularly holds meetings and/or telephone conferences that are open to the public. Persons wishing to attend any meeting and/or telephone conference should contact the Secretary of JCNRM.

ACKNOWLEDGMENTS

This edition of the advanced non-LWR PRA Standard was the result of the dedicated efforts of the following individuals who are responsible for the changes made to the 2013 trial use version of this Standard: Jordan Hagaman, Peiwen Whysall, Matthew Denman, and Matthew Warner at Kairos Power; Marty Sattison, Individual; Andrew Clark and Jamal Mohmand of Sandia National Laboratory; David Grabaskas of Argonne National Laboratory; Dennis Henneke of GE Hitachi Nuclear Energy; Hanh Phan of the U.S. Nuclear Regulatory Commission; and Karl Fleming, KNF Consulting Services, LLC.

ASME/ANS RA-S COMMITTEE

Probabilistic Risk Assessment Standard for Advanced Non-LWR Nuclear Power Plants

(The following is a roster of the Committee at the time of the approval of this Standard.)

ASME/ANS Joint Committee on Nuclear Risk Management

R. J. Budnitz, ANS Cochair, Lawrence Berkeley National Laboratory (retired)

1. R. Grantom, ASME Cochair, C. R. Grantom, P. E. Associates, LLC

2. W. Henneke, ANS Vice Cochair, GE Hitachi Nuclear Energy

P. F. Nelson, ASME Vice Cochair, National Autonomous University of Mexico

1. Martinez, Secretary, The American Society of Mechanical Engineers

2. J. Amico, Jensen Hughes, Inc.

V. K. Anderson, Nuclear Energy Institute

G. Apostolakis, Nuclear Risk Research Center

M. Bensi, University of Maryland

S. Bristol, NuScale Power

G. DeMoss, PSEG Nuclear

M. R. Denman, Kairos Power

F. Ferrante, Electric Power Research Institute

K. R. Fine, First Energy Nuclear Operating Company

K. N. Fleming, KNF Consulting Services, LLC

A. Gilbertson, U.S. Nuclear Regulatory Commission

D. Grabaskas, Argonne National Laboratory

H. A. Hackerott, Individual

T. G. Hook, Arizona Public Service

J. M. Jansen Vehec, Holtec International

D. M. Jones, Enercon Services

G. W. Kindred, Tennessee Valley Authority

S. H. Levinson, Individual

R. Linthicum, Exelon, PWR Owners Group

A. Maioli, Westinghouse Electric Co.

J. O’Brien, U.S. Department of Energy

M. K. Ravindra, MKRavindra Consulting

R. I. Rishel, Duke Energy, BWR Owners Group

M. B. Sattison, Individual

R. E. Schneider, Westinghouse Electric Co.

J. L. Stone, Exelon Corp.

I. B. Wall, Individual

S. Bernsen, Contributing Member, Individual

J. R. Chapman, Contributing Member, Individual

F. Dermarkar, Contributing Member, CANDU Owners Group

J. E. Hagaman, Alternate, Kairos Power

1. C. Hance, Alternate, Electric Power Research Institute

2. A. Hughes, Contributing Member, Etranco, Inc.

K. L. Kiper, Contributing Member, Westinghouse Electric Co.

S. Kojima, Contributing Member, Individual

G. A. Krueger, Alternate, Nuclear Energy Institute

N. LaBarge, Alternate, Westinghouse Electric Co.

S. R. Lewis, Contributing Member, Individual

Y. J. Li, Alternate, GE Hitachi Nuclear Energy

S. Poghosyan, Contributing Member, International Atomic Energy Agency

P. A. Schroeder, Contributing Member, American Nuclear Society

1. Spitzer, Contributing Member, International Atomic Energy Agency

2. E. True, Contributing Member, Jensen Hughes, Inc.

M. J. Walker, Alternate, Tennessee Valley Authority

Advanced Non-LWR PRA Standard Writing Group

K. N. Fleming, Chair, KNF Consulting Services, LLC

D. Grabaskas, Vice Chair, Argonne National Laboratory

R. J. Budnitz, Lawrence Berkeley National Laboratory (retired)

A. J. Clark, Sandia National Laboratories

M. R. Denman, Kairos Power

H. L. Detar, Westinghouse Electric Co.

M. Gonzales, U.S. Nuclear Regulatory Commission

J. E. Hagaman, Kairos Power

D. W. Henneke, GE Hitachi Nuclear Energy

A. J. Huning, Oak Ridge National Laboratory

Z. Jankovsky, Sandia National Laboratories

B. C. Johnson, TerraPower

K. Muramatsu, Tokyo City University, Japan

H. K. Phan, U.S. Nuclear Regulatory Commission

M. B. Sattison, Individual

J. Tong, INET, Tsinghua University, the People’s Republic of China

S. D. Unwin, Pacific Northwest National Laboratory

M. S. Warner, Kairos Power

P. T. Whysall, Kairos Power

Subcommittee on Standards Development

1. R. Denman, Chair, Kairos Power

2. R. LaBarge, Vice Chair, Westinghouse Electric Co.

V. K. Anderson, Nuclear Energy Institute

S. Bernsen, Individual

S. Bristol, NuScale Power

K. N. Fleming, KNF Consulting Services LLC

A. Gilbertson, U.S. Nuclear Regulatory Commission

D. Grabaskas, Argonne National Laboratory

D. W. Henneke, GE Hitachi Nuclear Energy

K. Kaspar, South Texas Project Electric Generating Station

1. J. Li, GE Hitachi Nuclear Energy

2. Ma, Idaho National Laboratory

J. O’Brien, U.S. Department of Energy

B. J. Ratnagaran, Southern Company

M. B. Sattison, Individual

R. Schneider, Westinghouse Electric Co.

V. Sorel, Electricité de France

R. Summitt, Engineering Planning and Management

G. Teagarden, Jensen Hughes, Inc.

S. D. Unwin, Pacific Northwest National Laboratory

P. Whiteman, AREVA

Subcommittee on Standards Maintenance

P. J. Amico, Chair, Jensen Hughes, Inc.

A. Maioli, Vice Chair, Westinghouse Electric Co.

V. Andersen, Jensen Hughes, Inc.

M. Bensi, University of Maryland

J. M. Biersdorf, Idaho National Labs

R. J. Budnitz, Lawrence Berkeley National Laboratory (retired)

M. Carr, Palo Verde Generating Station

S. Eder, Facility Risk Consultants

K. R. Fine, First Energy Nuclear Operating Company

H. A. Hackerott, Individual

J. Hall, Entergy Corporation

D. C Hance, Electric Power Research Institute

D. W. Henneke, GE Hitachi Nuclear Energy

T. G. Hook, Arizona Public Service

J. M. Jansen Vehec, Holtec International

F. Joglar, Jensen Hughes, Inc.

D. M. Jones, Enercon Services

A. M. Kammerer, Individual

J. Lin, ABS Consulting

N. Lovelace, Hughes Associates

D. N. Miskiewicz, Engineering Planning and Management, Inc.

1. Ning, U.S. Nuclear Regulatory Commission

2. K. Ravindra, MKRavindra Consulting

A. Rubbicco, Duke Energy

R. E. Schneider, Westinghouse Electric Co.

M. L. Szoke, UK Atomic Energy Authority

I. B. Wall, Individual

M. Degonish, Alternate, Westinghouse Electric Co.

J. Mitman, Alternate, U.S. Nuclear Regulatory Commission

Subcommittee on Risk Applications

G. W. Kindred, Chair, Tennessee Valley Authority

G. DeMoss, Vice Chair, PSEG Nuclear, LLC

D. M. Jones, Vice Chair, Enercon Services

R. J. Budnitz, Lawrence Berkeley National Laboratory (retired)

C. R. Grantom, C.R. Grantom P.E. Associates, LLC

F. G. Hudson, Metcalfe PLLC

J. M. Jansen Vehec, Holtec International

S. H. Levinson, Individual

R. Linthicum, Exelon, PWR Owners Group

A. Moldenhauer, Dominion Energy

P. F. Nelson, National Autonomous University of Mexico

J. O’Brien, U.S. Department of Energy

V. Patel, Southern Company

1. Rishel, Duke Energy, BWR Owners Group

2. Rosenberg, U.S. Nuclear Regulatory Commission

1. L. Stone, Exelon Corp.

2. Sutton, INGRID Consulting Services, LLC

V. Warren, Jensen Hughes, Inc.

C. DeMessieres, Alternate, U.S. Nuclear Regulatory Commission

SECTION 1 – INTRODUCTION CONTENTS

SECTION 1 INTRODUCTION 1

1. Objective 3

2. Scope 3

   1. Treatment of Hazard Groups 4

   2. Hazards and Initiating Events 4

3. Requirements for Different Design-Life Cycle Stages 4

4. Structure for PRA Requirements 5

   1. PRA Elements 5

   2. High Level Requirements 6

   3. Supporting Requirements 6

5. Applicability of PRA Technical Elements 9

6. PRA Configuration Control 9

7. Peer Review Requirements 9