ML24135A387
| ML24135A387 | |
| Person / Time | |
|---|---|
| Site: | 99902078 |
| Issue date: | 05/14/2024 |
| From: | NRC |
| To: | NRC/NRR/DNRL/NRLB |
| References | |
| Download: ML24135A387 (5) | |
Text
From:
Getachew Tesfaye Sent:
Tuesday, May 14, 2024 9:17 PM To:
Request for Additional Information Cc:
Alina Schiller; Mahmoud -MJ-Jardaneh; Griffith, Thomas; Vance, Lindsay; NuScale-SDA-720RAIsPEm Resource
Subject:
NuScale SDAA Section 19.1 - Request for Additional Information No. 025 (RAI-10190-R1)
Attachments:
SECTION 19.1-RAI-10190-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. ML23306A033).
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:
34 Mail Envelope Properties (BY5PR09MB5682D6CA58AA0BF9DD5345368CEC2)
Subject:
NuScale SDAA Section 19.1 - Request for Additional Information No. 025 (RAI-10190-R1)
Sent Date:
5/14/2024 9:17:23 PM Received Date:
5/14/2024 9:17:27 PM From:
Getachew Tesfaye Created By:
Getachew.Tesfaye@nrc.gov Recipients:
"Alina Schiller" <Alina.Schiller@nrc.gov>
Tracking Status: None "Mahmoud -MJ-Jardaneh" <Mahmoud.Jardaneh@nrc.gov>
Tracking Status: None "Griffith, Thomas" <tgriffith@nuscalepower.com>
Tracking Status: None "Vance, Lindsay" <lvance@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 584 5/14/2024 9:17:27 PM SECTION 19.1-RAI-10190-R1-FINAL.pdf 151459 Options Priority:
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1 REQUEST FOR ADDITIONAL INFORMATION No. 025 (RAI-10190-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, PROBABILISTIC RISK ASSESSMENT DOCKET NO. 05200050 ISSUE DATE: 05/14/2024
=
Background===
By letter dated October 31, 2023, NuScale Power, LLC (NuScale or the applicant) submitted Part 2, Final Safety Analysis Report (FSAR), Revision 1, Chapter 19, Probabilistic Risk Assessment and Severe Accident Evaluation (Agencywide Documents Access and Management System Accession No. ML23304A385), Chapter 9, Auxiliary Systems (ML23304A355), and Chapter 6, Engineered Safety Features (ML23304A345) 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 Code of Federal Regulations (10 CFR) Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants, Subpart E, Standard Design Approvals. The NRC staff has reviewed the information in Chapters 19, 9, and 6 of the SDAA and has determined that additional information is required to complete its review.
Question 19.1-52 Regulatory Basis 10 CFR 52.137(a)(2) requires that an application must contain a final safety analysis report which must include, in part, the following, A description and analysis of the SSCs
[structures, systems, and components] of the facility, with emphasis upon performance requirements, the bases, with technical justification, upon which the requirements have been established, and the evaluations required to show that safety functions will be accomplishedThe description shall be sufficient to permit understanding of the system designs and their relationship to the safety evaluations. Items such ascontainment system, engineered safety features, auxiliary and emergency systems shall be discussedThe following power reactor design characteristics will be taken into consideration by the Commission:
The extent to which generally accepted engineering standards are applied to the design of the reactor; The extent to which the reactor incorporates unique, unusual or enhanced safety features having a significant bearing on the probability or consequences of accidental release of radioactive materials; 10 CFR 52.137(a)(25) requires that an application must contain a final safety analysis report which must include, in part, the following, a description of the design-specific probabilistic risk assessment and its results.
2 10 CFR Part 50, Appendix A, GDC 1, Quality standards and records. Structures, systems, and components important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed. Where generally recognized codes and standards are used, they shall be identified and evaluated to determine their applicability, adequacy, and sufficiency and shall be supplemented or modified as necessary to assure a quality product in keeping with the required safety function.
Issue The Containment Evacuation System (CES) performs numerous functions for the NuScale 460 design as listed in Section 9.3.6 of the FSAR. The safety-related containment isolation valves (CIVs) perform a safety function to isolate containment under various accident conditions to contain radioactivity within containment. The CIVs will close based on a Module Protection System signal and are part of the CES piping at the point where the piping interacts with the containment structure. The CES piping in the US460 design is larger in size compared to that in the design certification application (DCA) (US600) design. In the US460 design, the CES piping and valves downstream of the CIVs and upstream of the CES vacuum pump suction were enhanced compared to the DCA by applying an increased pressure rating to them to withstand containment design pressure. The enhanced valves include a motor-operated valve, which bypasses the vacuum pumps, and three air-operated valves. Two of the three air-operated valves are located at the suction of the vacuum pump, and one is located at the interface with the service air system. The Module Protection System provides a signal to close the enhanced valves as a backup to the CIVs failing to close.
The enhanced CES design in the US460 is important to safety because, with these enhancements, the CES piping and the four enhanced valves mentioned above provide defense-in-depth (DID) to the CIV function to isolate containment. The enhanced CES design in the US460 is important to risk because it is used as the basis to exclude the failure of the CIVs in the Level 1 and Level 2 probabilistic risk assessment (PRA). In the US460, a failure of containment isolation, coupled with the larger CES line size, has the potential to impact emergency core cooling system (ECCS) success due to a loss of inventory and consequently result in core damage and radiological release to the public through containment bypass. Due to the enhanced CES design, a failure of containment isolation, in conjunction with a failure of the enhanced section of CES piping to isolate (i.e., closure of the 4 valves), was determined by the applicant as very low likelihood compared to the likelihood of incomplete activation of the ECCS and, therefore, an insignificant contribution to risk of the US460 design.
A standard design approval applicant is required to perform a design-specific PRA and document its description and results in the application. The enhanced CES design provides DID to containment isolation and, as such, reduces the risk of radiological release to the public.
However, Chapters 6 and 9 of the SDAA FSAR do not include any information on the enhanced CES design in the US460.
Information Requested Provide FSAR markups in Chapters 6 and 9 of the SDAA FSAR for the enhanced CES design. The FSAR markups should include, but are not limited to, the following:
FSAR Section 6.2.4.2: A description of the enhanced CES design.
3 FSAR Section 9.3.6: A description of the purpose of the enhanced CES design.
FSAR Table 9.3.6-1: Component safety classification information and the augmented design requirements for the enhanced section of the CES (e.g., ASME Standard B31.1).
FSAR Figure 9.3.6-1: Drawings or figures detailing component locations.