ML22146A399
| ML22146A399 | |
| Person / Time | |
|---|---|
| Site: | 99902043 |
| Issue date: | 06/14/2022 |
| From: | Alina Schiller NRC/NRR/DNRL/NRLB |
| To: | Michael Dudek NRC/NRR/DNRL/NRLB |
| Schiller A | |
| Shared Package | |
| ML22146A398 | List: |
| References | |
| ML20217L422, ML22094A057 | |
| Download: ML22146A399 (10) | |
Text
June 14, 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:
AUDIT
SUMMARY
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 and approval. In this licensing topical report (LTR), NuScale is seeking NRC staffs approval for the use of a methodology for establishing the technical basis for plume exposure emergency planning zones (EPZ).
The NRC staff initiated a regulatory audit as part of its review of the LTR. The purpose of this regulatory audit was for the NRC staff to audit NuScales calculations associated with its methodology in support of the staffs review of the LTR (revised audit plan at ML22094A057). Via teleconference, the NRC conducted an audit entrance meeting on November 29, 2021, held multiple regulatory audit discussions, and performed an exit meeting on May 3, 2022.
CONTACTS: Alina Schiller, NRR/DNRL 301-415-8177 Getachew Tesfaye, NRR/DNRL 301-415-8013
The audit was conducted remotely via NuScales electronic reading room (eRR) and teleconferences on Microsoft Teams. As the audit proceeded, the staff requested additional documents to review which NuScale provided in the eRR. No pre-decisional documents were provided directly to the staff or docketed.
Docket No. 99902043
Enclosure:
As stated cc w/encl.: DC NuScale Power LLC Listserv
PKG: ML22146A398 PROP: ML22161B038 PUBLIC: ML22146A399
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DATE 05/25/2022 05/27/2022 05/27/2022 05/27/2022 OFFICE DNRL/NRLB:PM NAME ASchille*r DATE 06/14/2022
Enclosure AUDIT
SUMMARY
FOR THE REGULATORY AUDIT OF NUSCALE TOPICAL REPORT TR-0915-17772, METHODOLOGY FOR ESTABLISHING THE TECHNICAL BASIS FOR PLUME EXPOSURE EMERGENCY PLANNING ZONES, REVISION 2
1.0 BACKGROUND
AND PURPOSE 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 Commissions (NRCs) review and approval. In this licensing topical report (LTR), NuScale is seeking NRC staffs approval for the use of a risk-informed methodology for establishing the technical basis for plume exposure emergency planning zones (EPZs).
Revision 2 contained a significant scope change from Revision 1 to include advanced light-water (LW) small modular reactors (SMRs) and advanced non-light-water reactors. In response to staffs Request for Additional Information (RAI) 9830 (ML21146A363), the scope of the LTR Revision 2 was reduced to only include LW SMRs. In order to seek clarity on this issue, as well as several others, the NRC staff initiated a regulatory audit as part of its review of the LTR. The purpose of this regulatory audit was for the NRC staff to exchange information, review, and provide clarifying feedback on NuScales example calculation using its methodology for its design at an operating reactor site in support of the staffs review of this LTR.
The NRC staff, following RAI 9828 (ML21116A110), has engaged with NuScale to justify the proposed seismic events screening criteria in the LTR. An integrated team of NRC staff experts from several offices developed an approach for seismic event sequence screening for EPZ sizing purposes for LW SMRs. The NRC staff communicated options to resolve technical issues, including options for seismic event screening criteria, based on this approach at public meetings on October 27, 2021, and November 4, 2021 (meetings summary at ML21316A115). The four options proposed were:
- 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 LTR at COL stage using a technically defensible approach.
2 The regulatory audit included the NRC staffs review of non-docketed information via the NuScale electronic reading room (eRR) and teleconferences with NuScale.
2.0 REGULATORY AUDIT BASIS 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, (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 (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 Decision-making, Final Report (ML17062A466) 3.0 AUDIT LOCATION AND DATES The audit was conducted remotely via NuScales eRR and Teams meetings.
Dates:
November 29, 2021-April 29, 2022 Location:
NuScale eRR
3 4.0 AUDIT TEAM MEMBERS Marie Pohida, NRR/DRA/APLC Shilp Vasavada, NRR/DRA/APLC Mihaela Biro, NRR/DRA/APLA Elijah Dickson, NRR/DRA/ARCB Todd Smith, NSIR/DPR Raymond Hoffman, NSIR/DPR/RLB Keith Compton, RES/DSA/AAB Getachew Tesfaye, NRR/DNRL/NRLB Alina Schiller, NRR/DNRL/NRLB 5.0 APPLICANT PARTICIPANTS Liz English Carrie Fosaaen Mark Shaver Jeremiah Doyle Brandon Haley Gary Becker 6.0 AUDIT DOCUMENTS The staff audited the following documents provided by NuScale in the eRR:
((
4 L. TR-0915-17772_Methodology for EPZ-Table 4-1
7.0 DESCRIPTION
OF AUDIT ACTIVITIES AND
SUMMARY
OF OBSERVATIONS During the audit, NuScale communicated that ((
}} and (( }} in the LTR methodology. NuScale also proposed a change to the methodology to use a (( }}.
During the audit, NuScale provided also proposed design features that would be identified in the LTR to limit the scope of the LTR to the NuScale design, including the Standard Design Approval (SDA) design and other possible future derivatives. The staff evaluated NuSales proposed design features and provided feedback on the list. To support the staffs review of the updated methodology, NRC staff requested NuScale to provide an example calculation for NuScales implementation of the updated methodology. On January 28, 2022, NuScale agreed to and developed a detailed example implementation of the updated methodology by March 25, 2022, to support additional discussions with the NRC staff. NuScale developed the calculation that included details of the inputs to their proposed methodology and how it could be exercised. In addition, NuScale provided a walkthrough of the calculation. The NRC staff audited NuScales detailed calculation using these information sources and provided technical and clarifying feedback on the methodology in the LTR using the detailed calculation as the basis. The NRC staffs review of and feedback on the example calculation was not to accept or approve the example calculation or its results. Based on audit discussions, it is the staffs understanding that the example will not be referenced in the Revision 3 to the LTR. The NRC staff is not making and will not make a regulatory finding on the example calculation or its results. The inputs to this detailed example calculation included: A. Non-seismic sequences from the NuScale design certification (DC) probabilistic risk assessment (PRA) (internal events, external hazards and low power and shutdown); B. Seismic sequences and fragilities from the NuScale DC PRA-based seismic margin analysis (SMA) with refinements; C. Seismic hazard and source term and seismic core damage frequency from the NuScale Severe Accident Design Alternative (SAMDA) analysis, Applicant Environmental Report Standard Design Certification, Revision 5 (ML20224A512) developed for the Surry and Peach Bottom sites. The seismic hazard was used in the PRA-based SMA to determine seismic sequence frequencies; D. Severe accident source terms to the environment based on the release categories from the NuScale SAMDA analysis;
5 E. Off-Site Design-Basis Source Term (DBST) from calculation EC-0000-2274; and F. Dose in Place MACCS model -based on MELCOR Accident Consequence Code System (MACCS) base model ER-P030-4113. The staffs review of the example calculation focused on: A. (( }}; B. Non-seismic single module screening based on 1E-7/year core damage sequence frequency; C. Multi-module sequence identification and screening for seismic and non-seismic sequences; D. Treatment of uncertainty in the seismic event screening threshold; E. Treatment of uncertainty in non-seismic core damage sequences; F. Consideration of key assumptions and sources of uncertainty in the underlying PRAs; G. Treatment of other risks that do not involve core damage (e.g., mechanical damage of fuel pins by a dropped partially intact module being moved during refueling); H. Classification of more severe (containment failed) and less severe (containment intact) core damage sequences including severe accident phenomena; I. Severe accident source terms from the NuScale SAMDA analysis; J. Off-site dose calculations; and K. EPZ dose criteria and EPZ dose versus distance calculations: EPZ distance from the DBST compared to the early phase U.S Environmental, Protection Agency Protective Action Guidelines (PAGs), EPZ distance from less severe accidents compared to the early phase PAGs, EPZ distance for a substantial reduction in early health effects, 200 rem acute whole body dose, using acute red marrow dose, and ((
}}.
6 The staff found that NuScales detailed example calculation provided an adequate demonstration of the proposed methodology, including the changes proposed during the audit. Thus, the staff was able to focus on specific audit discussion items and understand proposed LTR updates. These discussion items included: A. The need for key assumptions and key sources of modeled uncertainty to be identified and evaluated by the applicant in context of the application and the NRC staffs corresponding condition of use as communicated in the October 27, 2021, public meeting; B. Clarification of wording inconsistencies; C. Clarification of the term new sequences in the context of the uncertainty treatment for the seismic event screening threshold; D. The use of the terms point estimate versus best-estimate; E. Characterization of certain sequences as less severe as opposed to more severe and assignment of sequences to a particular release category; F. Uncertainty analysis regarding site-specific meteorology; G. Ensuring that the user of the LTR will retain the information on and relevant to the screened-out sequences for emergency plan development, pursuant to 10 CFR 50.47, Emergency plans; H. Consideration of a potential condition of application in the staff SER describing an acceptable (( }}; and I. Consideration in the Revision 3 to the LTR the need to update and/or remove the examples in appendices A through E to reflect the updated methodology recognizing the NRC staff will not be rendering a regulatory finding on the appendices, per NuScales request in the LTR. 8.0 EXIT BRIEFING The NRC staff conducted an audit exit meeting via a teleconference on May 3, 2022. The NRC staff summarized their observations and described information that would need to be docketed for the NRC staff to continue its review. 9.0 OPEN ITEMS AND PROPOSED CLOSURE PATHS Not applicable. 10.0 DEVIATIONS FROM THE AUDIT PLAN Not applicable.
7
11.0 REFERENCES
- 1.
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.
- 2.
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.
- 3.
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, April 12, 2022, ADAMS Accession No. ML22094A057.
- 4.
Request for Additional Information (RAI) 9828, Issued April 22, 2021, ADAMS Accession No. ML21116A110.
- 5.
Request for Additional Information (RAI) 9830, Issued April 22, 2021, ADAMS Accession No. ML21146A363 for the RAI response.
- 6.
NuScale Severe Accident Design Alternative (SAMDA) analysis (ER-P040-4281), contained in the Applicant Environmental Report Standard Design Certification, Revision 5, July 2020, ADAMS Accession No. ML20224A512.}}