ML24080A510
| ML24080A510 | |
| Person / Time | |
|---|---|
| Site: | 99902078 |
| Issue date: | 03/20/2024 |
| From: | NRC |
| To: | NRC/NRR/DNRL/NRLB |
| References | |
| Download: ML24080A510 (5) | |
Text
From:
Getachew Tesfaye Sent:
Wednesday, March 20, 2024 9:00 PM To:
Request for Additional Information Cc:
Greg Cranston; Mahmoud -MJ-Jardaneh; Griffith, Thomas; Osborn, Jim; NuScale-SDA-720RAIsPEm Resource
Subject:
NuScale SDAA Section 9.3.4 - Request for Additional Information No. 022 (RAI-10157-R1)
Attachments:
SECTION 9.3.4 - RAI-10157-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:
29 Mail Envelope Properties (DM6PR09MB5686A5BC47990ADB9E4E5C228C322)
Subject:
NuScale SDAA Section 9.3.4 - Request for Additional Information No. 022 (RAI-10157-R1)
Sent Date:
3/20/2024 9:00:23 PM Received Date:
3/20/2024 9:00:28 PM From:
Getachew Tesfaye Created By:
Getachew.Tesfaye@nrc.gov Recipients:
"Greg Cranston" <Gregory.Cranston@nrc.gov>
Tracking Status: None "Mahmoud -MJ-Jardaneh" <Mahmoud.Jardaneh@nrc.gov>
Tracking Status: None "Griffith, Thomas" <tgriffith@nuscalepower.com>
Tracking Status: None "Osborn, Jim" <josborn@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:
DM6PR09MB5686.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 584 3/20/2024 9:00:28 PM SECTION 9.3.4 - RAI-10157-R1-FINAL.pdf 152713 Options Priority:
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1 REQUEST FOR ADDITIONAL INFORMATION No. 022 (RAI-10157-R1)
BY THE OFFICE OF NUCLEAR REACTOR REGULATION NUSCALE STANDARD DESIGN APPROVAL APPLICATION DOCKET NO.
05200050 CHAPTER 9, AUXILIARY SYSTEMS SECTION 9.3.4, CHEMICAL AND VOLUME CONTROL SYSTEM ISSUE DATE: 03/20/2024
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Background===
By letter dated October 31, 2023, NuScale Power, LLC (NuScale or the applicant) submitted Part 2, Final Safety Analysis Report (FSAR), Chapter 9, Auxiliary Systems, Revision 1 (Agencywide Documents Access and Management System Accession No. ML23304A355), of the NuScale Standard Design Approval Application (SDAA) for its US460 standard plant design.
The applicant submitted the US460 standard 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 Chapter 9 of the SDAA, and other Chapters as necessary, and determined that additional information is required to complete its review.
Question 9.3.4-1 Regulatory Basis 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 demineralized water supply isolation valves perform the safety function to isolate the demineralized water system and terminate an inadvertent boron dilution event. Consistent with its importance to safety, SDAA FSAR Table 9.3.4-3, Classification of Structures, Systems, and Components, classifies the demineralized water isolation valves as safety-related, and seismic Category I. Additionally, SDAA FSAR Table 3.9-16, Active Valve List, identifies the demineralized water isolation valves as ASME Code Section III Class 3 and necessary for accident mitigation.
SDAA Table 9.3.4-3 also classifies the safety-related demineralized water isolation valves as Quality Group D. This is a change from the NuScale US600 design which classified these isolation valves as Quality Group C and the staff subsequently found this treatment acceptable and concluded it is consistent with RG 1.26, Quality Group Classifications and Standards for Water-, Steam-, and Radioactive-Waste-Containing Components of NuScale Power Plants, and GDC 1.
2 The quality standards applied to Quality Group D SSCs, as delineated in RG 1.26, are not commensurate with the importance to safety of SSCs that perform safety-related functions and are relied on for mitigating design-basis events. Therefore, the staff cannot reach a determination on the adequacy of the current quality group classification of the demineralized water isolation valves.
Information Requested The applicant is requested to update the SDAA to classify the demineralized water isolation valves as Quality Group C consistent with RG 1.26 and GDC 1.
Question 9.3.4-2 Regulatory Basis GDC 14, Reactor coolant pressure boundary. The reactor coolant pressure boundary shall be designed, fabricated, erected, and tested so as to have an extremely low probability of abnormal leakage, of rapidly propagating failure, and of gross rupture.
GDC 26, Reactivity control system redundancy and capability. Two independent reactivity control systems of different design principles shall be provided. One of the systems shall use control rods, preferably including a positive means for inserting the rods, and shall be capable of reliably controlling reactivity changes to assure that under conditions of normal operation, including anticipated operational occurrences, and with appropriate margin for malfunctions such as stuck rods, specified acceptable fuel design limits are not exceeded.
The second reactivity control system shall be capable of reliably controlling the rate of reactivity changes resulting from planned, normal power changes (including xenon burnout) to assure acceptable fuel design limits are not exceeded. One of the systems shall be capable of holding the reactor core subcritical under cold conditions.
Issue SDAA FSAR Table 9.3.4-2, Boron Addition System Major Equipment with Design Data and Parameters, provides a minimum boron concentration for the boron addition system (BAS). Additionally, SDAA FSAR Section 9.3.4.2.1 states, [t]he BAS stores and transports borated water mixtures with a boron concentration of approximately 4370 ppm However, the SDAA does not prescribe that maximum boron concentration. This value (5600 ppm) was prescribed in the US600 design certification but appears to be removed in the US460 SDAA.
DSRS 9.3.4, Chemical and Volume Control System, provides guidance acceptable to the staff and states, the CVCS design and arrangement should be that all components and piping that can contain boric acid will either be heat-traced, located within heated rooms, or maintained at a low enough concentration to prevent precipitation of boric acid.
Absent a specification for the maximum boron concentration in the SDAA, the staff cannot confirm that the CVCS and BAS will prevent the precipitation of boric acid such that the CVCS can continue perform its functions associated with applicable regulations.
3 Information Requested The applicant is requested to update the SDAA to provide a specification for the maximum boron concentration in the CVCS and BAS.
Question 9.3.4-3 Regulatory Basis 10 CFR 52.137(a)(2) requires, A description and analysis of the SSCs 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 accomplished The description shall be sufficient to permit understanding of the system designs and their relationship to the safety evaluations. Items such asreactor coolant system other engineered safety features shall be discussedThe following power reactor design characteristics will be taken into consideration by the Commission:
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.
10 CFR 52.137(a)(25) requires, a description of the design-specific probabilistic risk assessment and its results.
Issue A standard design approval applicant is required to perform a design-specific probabilistic risk assessment (PRA) and document its description and results in the application. The capability of the CVCS to provide makeup inventory to the RCS is relied on in several sequences in the PRA. FSAR Table 19.1-3 identifies the CVCS check valve locations and CVCS flow area restrictions as key design features resulting from the PRA analyses for minimizing the likelihood of a break outside containment and reducing large release frequency and the conditional containment failure probability, respectively. The staff notes that the use of a CVCS flow area restriction would also play a significant role in any design-basis loss of reactor coolant inventory outside of containment. However, the staff could not find any information detailing the CVCS flow restriction feature in the FSAR.
Information Requested The applicant is requested to update the SDAA to provide necessary information in the design sections of the FSAR (e.g., Chapters 5, 6, 9, etc.) for the CVCS flow restriction design features. This information should include, but is not limited to, a description of the design feature, component specifications and classification information, and drawings or figures detailing its location(s) and orientation.