ML23340A047
| ML23340A047 | |
| Person / Time | |
|---|---|
| Site: | 99902078 |
| Issue date: | 12/06/2023 |
| From: | NRC |
| To: | NRC/NRR/DNRL/NRLB |
| References | |
| Download: ML23340A047 (4) | |
Text
From:
Getachew Tesfaye Sent:
Wednesday, December 6, 2023 10:02 AM To:
Request for Additional Information Cc:
Alina Schiller; Mahmoud Jardaneh; Griffith, Thomas; Sfowler@nuscalepower.com; NuScale-SDA-720RAIsPEm Resource
Subject:
NuScale SDAA Section 19.1.5 - Request for Additional Information No. 013 (RAI-10115-R1)
Attachments:
SECTION 19.1.5 - RAI-10115-R1-FINAL.pdf Attached please find NRC staffs request for additional information (RAI) concerning the review of NuScale Standard Design Approval Application for its US460 standard plant design (Agencywide Documents Access and Management System (ADAMS) Accession No. ML222339A066).
Please submit your technically correct and complete response by the agreed upon date to the NRC Document Control Desk.
If you have any questions, please do not hesitate to contact me.
Thank you, Getachew Tesfaye (He/Him)
Senior Project Manager NRC/NRR/DNRL/NRLB 301-415-8013
Hearing Identifier:
NuScale_SDA720_RAI_Public Email Number:
22 Mail Envelope Properties (BY5PR09MB568246EDA07903833BEEE6C18C84A)
Subject:
NuScale SDAA Section 19.1.5 - Request for Additional Information No. 013 (RAI-10115-R1)
Sent Date:
12/6/2023 10:01:56 AM Received Date:
12/6/2023 10:01:58 AM From:
Getachew Tesfaye Created By:
Getachew.Tesfaye@nrc.gov Recipients:
"Alina Schiller" <Alina.Schiller@nrc.gov>
Tracking Status: None "Mahmoud Jardaneh" <Mahmoud.Jardaneh@nrc.gov>
Tracking Status: None "Griffith, Thomas" <tgriffith@nuscalepower.com>
Tracking Status: None "Sfowler@nuscalepower.com" <sfowler@nuscalepower.com>
Tracking Status: None "NuScale-SDA-720RAIsPEm Resource"
<NuScale-SDA-720RAIsPEm.Resource@usnrc.onmicrosoft.com>
Tracking Status: None "Request for Additional Information" <RAI@nuscalepower.com>
Tracking Status: None Post Office:
BY5PR09MB5682.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 585 12/6/2023 10:01:58 AM SECTION 19.1.5 - RAI-10115-R1-FINAL.pdf 149459 Options Priority:
Normal Return Notification:
No Reply Requested:
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1 REQUEST FOR ADDITIONAL INFORMATION No. 013 (RAI-10115-R1)
BY THE OFFICE OF NUCLEAR REACTOR REGULATION NUSCALE STANDARD DESIGN APPROVAL APPLICATION DOCKET NO.
05200050 CHAPTER 19, PROBABILISTIC RISK ASSESSMENT AND SEVERE ACCIDENT EVALUATION SECTION 19.1.5, SAFETY INSIGHTS FROM THE EXTERNAL EVENTS PROBABILISTIC RISK ASSESSMENT FOR OPERATIONS AT POWER ISSUE DATE: 12/06/2023
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Background===
By letter dated December 31, 2022, NuScale Power, LLC (NuScale or the applicant) submitted Part 2, Final Safety Analysis Report (FSAR), Chapter 19, "Probabilistic Risk Assessment and Severe Accident Evaluation," Revision 0 (Agencywide Documents Access and Management System Accession No. ML22365A010) of the NuScale Standard Design Approval Application (SDAA) for its US460 standard plant design. The applicant submitted the US460 plant SDAA in accordance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants, Subpart E, Standard Design Approvals. The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in Chapter 19 of the SDAA and determined that additional information is required to complete its review.
Question 19.1.5-1 Regulatory Basis 10 CFR 52.137(a)(25) states that an SDAA must contain an FSAR that includes a description of the design-specific probabilistic risk assessment (PRA) and its results. The Statement of Considerations (SOC) for Part 52 (72FR49352) states, [t]he Commission has decided that the contents of applications for design approvals should contain essentially the same technical information that is required of design certification applications (e.g., demonstration of compliance with technically relevant Three Mile Island requirements, proposed technical resolutions of unresolved safety issues and medium and high-priority generic safety issues, and design-specific probabilistic risk assessment information) and many of the public comments on contents of applications for design certification apply to the requirements for design approvals.
Issue In SECY-93-087, the Commission approved the use of a PRA-based seismic margins analysis (SMA) for a design certification application (DCA) in lieu of a seismic PRA.
NUREG-0800, Standard Review Plan (SRP), Chapter 19.0, Revision 3, provides guidance on the methods acceptable to the staff to demonstrate low seismic risk, including the acceptance criteria for PRA-based SMA. The guidance includes the seismic fragility calculations based on design-specific information and the consideration of the accident sequences that require seismic
2 fragility evaluation for determining sequence-level high confidence of low probability of failure (HCLPF) capacities.
Evaluating the seismic fragility is a key element of a PRA-based SMA and provides key insights to understand plant risk. A PRA-based SMA considers all sequences leading to core damage or containment failure. The results of the PRA-based SMA include characterization of the HCLPF capacities for select structures, systems, and components (SSCs) and sequence-level and plant-level HCLPF capacities. Focusing on only those SSCs that contribute to the plant-level HCLPF capacity does not provide adequate information to support the staffs review of the development of and risk insights from the PRA-based SMA. Further, only providing HCLPF capacities does not provide adequate information for the staffs review of the fragility evaluation performed for the PRA-based SMA and the resulting uncertainties. Section 5.4, Position on Documentation of DC/COL-ISG-020 (ML100491233) specifies that fragilities for the SSCs in the seismic equipment list (SEL) as well as the sequence-level and plant-level HCLPF capacities, among others, be provided in Chapter 19 of the FSAR.
Due to the above reasons, NuScale SDAA FSAR Section 19.1.5.1, Seismic Risk Evaluation, does not provide sufficient information in Table 19.1-32 for the staff to effectively review the description and results of the PRA-based SMA, including the SSC fragility parameters and the corresponding uncertainty. The level of information necessary for the staff to make it finding on PRA-based SMA is consistent with that provided in the NuScale DCA FSAR Table 19.1-38.
Consequently, there is insufficient information in the SDAA FSAR to support the staffs finding on the PRA-based SMA per the regulatory basis identified above and the guidance in SRP Section 19.0, specifically under Design-Specific PRA (PRA-Based SMA) and the acceptance criteria in Section II of that guidance. The information requested hereunder is necessary for the staff to evaluate the PRA-based SMA, including its results, and make corresponding safety findings.
Information Requested To support the staffs finding on the PRA-based SMA against 10 CFR 52.137(a)(25), NuScale is requested to update the FSAR to include the following information in either an expanded Table 19.1-32 or in separate tables:
- 1. Key SSCs on the SEL that are considered important to understanding seismic risk insights, with their respective failure modes, fragility parameters (HCLPF, median capacity (Am)),
logarithmic standard deviation for randomness (beta_r), logarithmic standard deviation for uncertainty (beta_u), fragility evaluation method, and seismic correlation information.
- 2. Sequence-level HCLPF capacities for each seismically initiated accident sequence.