ML22094A057

Revised Audit Plan for NuScale EPZ Topical Report - Rev. 2

ML22094A057
Person / Time
Site:	99902043
Issue date:	04/12/2022
From:	Alina Schiller NRC/NRR/DNRL/NRLB
To:	Michael Dudek NRC/NRR/DNRL/NRLB
Schiller A
References
TR-0915-17772, Rev 2
Download: ML22094A057 (8)

Text

April 12, 2022 MEMORANDUM TO:

Michael I. Dudek, Chief New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation FROM:

Alina Schiller, Project Manager /RA/

New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation

SUBJECT:

REVISED PLAN FOR THE REGULATORY AUDIT OF NUSCALE POWER, LLC, TOPICAL REPORT TR-0915-17772, METHODOLOGY FOR ESTABLISHING THE TECHNICAL BASIS FOR PLUME EXPOSURE EMERGENCY PLANNING ZONES, REVISION 2 By letter dated August 4, 2020, NuScale Power, LCC, (NuScale) submitted Topical Report (TR)-0915-17772, Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones, Revision 2 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20217L422) for the U.S. Nuclear Regulatory Commission (NRC) staffs review.

The NRC staff and NuScale agreed to a regulatory audit to discuss technical details related to the remaining issues involving the NRC Request for Additional Information (RAI) 9828 (ADAMS Accession No. ML21116A110). The audit commenced on November 29, 2021 (plan for the regulatory audit at ADAMS Accession No. ML21327A209).

At the audit discussion on December 9, 2021, NuScale identified the need to extend the regulatory audit to March 31, 2022 (revised plan for the regulatory audit at ADAMS Accession No. ML21349A368). By letter dated December 23, 2021 (ADAMS Accession No. ML21348A004), the staff communicated the review status update.

Docket No. 99902043

Enclosure:

Revised Audit Plan cc w/encl.: DC NuScale Power LLC Listserv CONTACT: Alina Schiller, NRR/DNRL (301) 415-8177

M. Dudek 2

The audit resumed on January 24, 2022, when NuScale proposed a modified version of one of the four viable options which the staff indicated, during the December 7, 2021, audit discussion, to resolve the remaining issue. To support its review of the modified option, the staff requested that NuScale use an example calculation to demonstrate the implementation of its proposed methodology, including the modified option. As agreed, NuScale provided the example implementation of the updated methodology to the NRC for review on March 24, 2022. At the audit discussion on March 29, 2022, NuScale provided a walkthrough of the example.

Additional audit meetings were scheduled in April 2022, based on the staffs review of the example calculation.

The staff and NuScale agreed to extend the audit to April 29, 2022, to allow time for the staff to finalize its review of NuScales example calculation. The revised audit plan is provided as an enclosure.

ML22094A057

• via e-mail NRR-106 OFFICE DNRL/NRLB: PM DNRL/NRLB: LA DNRL/NRLB: PM DNRL/NRLB: PM NAME ASchiller SGreen*

GTesfaye*

ASchiller DATE 03/29/2022 04/04/2022 03/30/2022 04/12/2022

Enclosure U.S. NUCLEAR REGULATORY COMMISSION REVISED PLAN FOR THE REGULATORY AUDIT OF NUSCALE POWER, LLC, TOPICAL REPORT TR-0915-17772, METHODOLOGY FOR ESTABLISHING THE TECHNICAL BASIS FOR PLUME EXPOSURE EMERGENCY PLANNING ZONES, REVISION 2 APPLICANT:

NuScale Power, LLC APPLICANT CONTACT:

Liz English Carrie Fosaaen Mark Shaver Jeremiah Doyle Brandon Haley Amee Gurr DATE:

November 29, 2021-April 29, 2022 LOCATION:

Remote Audit (via NuScales Electronic Reading Room (eRR))

AUDIT TEAM:

Marie Pohida (NRR/DRA/APLC), Team Lead Shilp Vasavada (NRR/DRA/APLC)

Mihaela Biro (NRR/DRA/APLA)

Elijah Dickson (NRR/DRA/ARCB)

Keith Compton (RES/DSA/AAB)

Todd Smith (NSIR/DPR)

Raymond Hoffman (NSIR/DPR/RLB)

PROJECT MANAGER:

Getachew Tesfaye/Alina Schiller (NRR/DNRL/NRLB)

BACKGROUND AND PURPOSE The purpose of this regulatory audit is for the U.S. Nuclear Regulatory Commission (NRC) staff to exchange information with, review, and provide clarifying feedback on NuScales preliminary dose-distance relationship calculation for an example small modular nuclear power plant in support of staffs review of NuScales Topical Report (TR)-0915-17772, Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones, Revision 2 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20217L422).

The NRC staff, following a request for additional information (RAI), has engaged with NuScale to justify the proposed seismic screening criteria in the TR. An integrated team of NRC staff experts developed an approach for seismic sequence screening for emergency planning zone (EPZ) sizing purposes for light-water (LW) small modular reactors (SMRs). The NRC staff communicated options to resolve technical issues, including alternative seismic screening criteria, based on this approach at public meetings on October 27, 2021, and November 4, 2021 (meetings summary at ADAMS Accession No. ML21316A115). The four options proposed are:

1. 5E-7/year annual exceedance frequency (AEF), with associated conditions on use.

2. 1E-6/year AEF for NuScales design only, with associated conditions on use.

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3. 1E-7/year sequence core damage frequency.

4. Site-and design-specific threshold, with associated conditions on use, justified by an applicant using the TR at construction and operating license (COL) stage using a technically defensible approach.

The NRC will specifically audit NuScales preliminary calculations associated with the seismic screening frequency applicability at an example nuclear power plant in support of staffs review of TR-0915-17772.

REGULATORY BASES This regulatory audit is based on the following:

Title 10 of the Code of Federal Regulations (CFR) 50.47, Emergency plans 10 CFR Part 50, Appendix E, Emergency Planning and Preparedness for Production and Utilization Facilities NUREG-0396/EPA 520/1-78-016, Planning Basis for the Development of State and Local Government Radiological Emergency Response Plans in Support of Light Water Nuclear Power Plants, (ADAMS Accession No. ML051390356)

Regulatory Guide 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," Revision 3 (ADAMS Accession No. ML17317A256)

U.S. Nuclear Regulatory Commission, Use of Probabilistic Risk Assessment Methods in Nuclear Activities: Final Policy Statement, Federal Register (60 FR 42622)

The Staff Requirements Memorandum (SRM) to SECY-04-0118, Plan for the Implementation of the Commission's Phased Approach to Probabilistic Risk Assessment Quality NUREG-1855, Revision 1: Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decisionmaking, Final Report, (ADAMS Accession No. ML17062A466)

REGULATORY AUDIT SCOPE The audit team will review NuScales preliminary dose-distance relationship calculation for an example small modular nuclear power plant using the methodology in NuScales TR-0915-17772. The staffs review will focus on providing clarifying feedback on the calculation.

The NRC staff will provide clarification on its approach on screening seismic events based on an occurrence frequency threshold for EPZ sizing purposes for LW SMRs discussed in the public meeting on October 27, 2021.

3 INFORMATION AND OTHER MATERIAL NECESSARY FOR THE REGULATORY AUDIT To support the regulatory audit, NRC staff requests relevant material to discuss the following:

Topic 1: NuScales Preliminary Dose-Distance Relationship Calculation

1. Details of the NuScales preliminary dose-distance relationship calculation for an example nuclear power plant using the methodology in NuScales TR-0915-17772, including answers to the following questions:

a. Whether the example nuclear power plant is an operational U.S. LW reactor or a SMR? Provide details of the example plant, including location, the nuclear steam supply system, and containment type.

b. What assumptions were made in performing the preliminary dose-distance relationship calculation?

c. What was the source term used for the calculation and what is the basis for using the selected source term (e.g., the accident sequence or scenario or scenario class used to define the source term)?

d. Is the source term consistent with the release category(ies) in the NuScale Severe Accident Mitigation Design Alternatives report (ADAMS Accession No. ML20224A512)? If not, provide the basis for choosing a different source term?

e. What were the meteorological parameters used for the calculation and what was the basis for using the selected parameters?

f.

What is the dose limit used for the calculation and how was it determined to be either more severe or less severe consistent with the methodology in NuScales TR-0915-17772?

g. What is the occurrence frequency of the sequence or scenario or class of scenarios that provided the source term used in the preliminary calculation?

h. What is the release frequency used in the calculation and how was it determined? What is its relationship to the selected source term?

i.

What is the approach and basis for calculating the probability of exceedance of the selected dose acceptance criteria?

j.

What potential analytical margins exist in the source term? Are there other inputs that can impact the dose-distance calculation?

Topic 2: Screening of Seismic Events

a. Is the seismic screening threshold based on the approach developed by the NRC staff expected to be limited to only NuScale-specific seismic design characteristics (such as the certified design response spectrum and plant-level fragility)?

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b. Is a design-and site-specific seismic screening threshold based on the approach developed by the NRC being considered as an option?

Topic 3: Appendix A, Appendix B, and Appendix C a) Please provide the appropriate source term (MELCOR) and dose (MACCS) output files supporting the example calculations.

LOGISTICS The audit will be conducted using NuScales eRR. The audit entrance meeting was held on November 29, 2021. The audit, scheduled to begin on November 29, 2021, extended from December 17, 2021, to March 31, 2022 (revised plan for the regulatory audit at ADAMS Accession No. ML21349A368), is further extended to April 29, 2022. The general format of the audit will include reviewing documents and discussions with the NuScale staff. The audit exit meeting will be scheduled at a later date.

SPECIAL REQUESTS On December 9, 2021, NuScale requested an extension of the audit to evaluate the four options to resolve the remaining issues involving RAI 9828 that were summarized by the NRC staff during the audit discussions on December 7, 2021. On January 24, 2022, NuScale proposed a modified version of one of the four options presented by the NRC staff. To support the review of the modified option, the staff requested that NuScale use an example calculation to demonstrate the implementation of its proposed methodology, including the modified option.

NuScale provided an example calculation for implementation of its proposed methodology, including the modified option, on March 24, 2022. The NRC staff and NuScale agreed to extend the audit to the end of April 2022, to allow time for the staff to complete its evaluation of the example calculation and NuScales proposed methodology.

DELIVERABLES The NRC audit team will issue a regulatory audit summary report within 90 days after the completion of the audit that will be placed on the docket and in ADAMS. The audit outcome could also identify any additional information to be reviewed in a follow-up audit or submitted separately for making regulatory decisions. If the audit outcome identifies additional needed information, the NRC will identify the need for RAIs or schedule a follow-up audit by April 29, 2022.

REFERENCES

1.

Letter from NuScale Power, LLC, NuScale Power, LLC Submittal of Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones, TR-0915-17772, Revision 2, August 4, 2020, ADAMS Accession No. ML20217L422.

2.

LIC-111, Regulatory Audits, October 31, 2019, ADAMS Accession No. ML19226A274.

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3.

Plan for the Regulatory Audit of NuScale Power, LLC, Topical Report TR-0915-17772, Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones, Revision 2, November 23, 2021, ADAMS Accession No. ML21327A209.

4.

Revised Plan for the Regulatory Audit of NuScale Power, LLC, Topical Report TR-0915-17772, Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones, Revision 2, December 21, 2021, ADAMS Accession No. ML21349A368.