ML24304B075
| ML24304B075 | |
| Person / Time | |
|---|---|
| Site: | 99902078 |
| Issue date: | 10/30/2024 |
| From: | NRC |
| To: | NRC/NRR/DNRL/NRLB |
| References | |
| Download: ML24304B075 (7) | |
Text
From:
Getachew Tesfaye Sent:
Wednesday, October 30, 2024 11:07 PM To:
Request for Additional Information Cc:
Ricky Vivanco (He/Him); Mahmoud -MJ-Jardaneh; Griffith, Thomas; Sfowler@nuscalepower.com; Bode, Amanda; NuScale-SDA-720RAIsPEm Resource
Subject:
Nonproprietary - NuScale LOCA TR-0516-49422-P, Rev 3 - Request for Additional Information No. 031 (RAI-10296-R1)
Attachments:
TR-0516-49422-P (LOCA) - RAI-10296-R1 - FINAL NON-PROPRIETARY.pdf Attached please find NRC staffs nonproprietary request for additional information (RAI) concerning the review of NuScale Topical Report TR-0516-49422-P, Loss-of-Coolant Accident Evaluation Model Revision 3 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23008A001). The encrypted proprietary version will be submitted in a separate email.
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:
41 Mail Envelope Properties (BY5PR09MB5682E7E8072B79B963C5FB928C552)
Subject:
Nonproprietary - NuScale LOCA TR-0516-49422-P, Rev 3 - Request for Additional Information No. 031 (RAI-10296-R1)
Sent Date:
10/30/2024 11:07:05 PM Received Date:
10/30/2024 11:07:07 PM From:
Getachew Tesfaye Created By:
Getachew.Tesfaye@nrc.gov Recipients:
"Ricky Vivanco (He/Him)" <Ricky.Vivanco@nrc.gov>
Tracking Status: None "Mahmoud -MJ-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 "Bode, Amanda" <abode@nuscalepower.com>
Tracking Status: None "NuScale-SDA-720RAIsPEm Resource" <NuScale-SDA-720RAIsPEm.Resource@nrc.gov>
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 687 10/30/2024 11:07:07 PM TR-0516-49422-P (LOCA) - RAI-10296-R1 - FINAL NON-PROPRIETARY.pdf 172086 Options Priority:
Normal Return Notification:
No Reply Requested:
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Normal Expiration Date:
1 REQUEST FOR ADDITIONAL INFORMATION No. 031 (RAI-10296-R1)
BY THE OFFICE OF NUCLEAR REACTOR REGULATION NUSCALE STANDARD DESIGN APPROVAL APPLICATION DOCKET NO. 05200050 TR-0516-49422-P, Loss-of-Coolant Accident Evaluation Model Revision 3 ISSUE DATE: 10/30/2024
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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) of the NuScale Standard Design Approval Application (SDAA) for its US460 standard plant design. Chapter 15, Transient and Accident Analyses (Agencywide Documents Access and Management System Accession No. ML23304A365) references the NuScale topical report "Loss-of-Coolant Accident Evaluation Model," TR-0516-49422-P, Revision 3 (ML23008A001), submitted January 8, 2023. 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 TR-0516-49422-P, Revision 3, and determined that additional information is required to complete its review.
Regulatory Basis 10 CFR 50.46 provides the acceptance criteria for emergency core cooling systems (ECCS) for light-water nuclear power reactors 10 CFR 50, Appendix K provides the required and acceptable features of an ECCS evaluation model (EM)
General Design Criterion (GDC) 38 requires a system to remove heat from the reactor containment and rapidly reduce containment pressure and temperature following any loss-of-coolant accident.
Question LOCA.LTR-51, 52, 54 Issue By letter dated January 6, 2023 (ML23011A012), NuScale submitted NRELAP5 files via DVD to support review of the loss-of-coolant accident (LOCA) licensing topical report (LTR), and other LTRs that support the SDAA. NuScale informed NRC in February 2024, that a code error was found. Subsequently, NuScale informed NRC that a new code version, NRELAP5 v1.7, was being released and would be used for the SDAA and supporting topical reports. ((
2 (( }}. (( }}. Further, staff understands some design changes may have also impacted the base model. In addition, the staff notes that part of the code upgrade altered the critical flow model. Information Requested In order for the staff to complete its technical review of the analytical approach and base its findings on submitted information relevant to the version of the code utilized in developing the EM, NuScale is requested to: a) Re-submit any of the remaining files impacted by this code version change. (( }}. b) Provide a compiled listing of all changes to the base model, as well as a listing of, and a disposition for, changes to the design that may impact the base model but were determined to be insignificant and therefore did not require a change to the base model. c) Provide justification that the introduced code changes are either in conformance with the 10 CFR Part 50 Appendix K critical flow model requirement or that the changes to the critical flow modeling are more conservative. (( }}. Question LOCA.LTR-4, 45, 47 Issue Integral and separate effects tests are used to justify the development and applicability of an evaluation model to a given design. Since test facilities are not typically full-scale, distortions exist that can affect local and global elements of the analysis when compared to the full-scale plant. Therefore, a scaling analysis needs to be performed that identifies important non-
3 dimensional parameters related to geometry and key phenomena and scaling distortions and their impact on the code assessment must be identified and evaluated. In accordance with NUREG-0800, Standard Review Plan (SRP), Section 15.0.2, the NRC staff performed a review to confirm that scaling analyses for the NuScale LOCA EM were conducted to provide assurance that the experimental data captured from its testing facility (NuScale Integral System Test (NIST) facility) and the models developed will be applicable to the full-scale analysis of the plant transients, and scaling distortions are identified and appropriately addressed in the bias and uncertainty evaluation. During its review of the scaling methodology described and evaluated in TR-0516-49422-P Sections 8.3 and 8.4, and data assessment reports provided for staff audit, (( }}. The staff understands the timing of event is subject to boundary conditions and the identified timing distortion is because the test boundary condition deviated from the original scaled one. However, the decay heat depends on the problem time and significant distortion of event time affects the level of decay heat at limiting figure of merit values. It is unclear to the staff if the uncertainty from this distortion was accounted for, since it does not align with the stated time scaling ratio described in the topical report. (( }}. Information Requested a) Based on the information above and because the scaling analysis summary in the Extended Passive Cooling LTR references to the LOCA TR for the scaling analysis of the long-term phase, NuScale is requested to i) ((
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4 (( }}; and ii) ((
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b) Update the scaling analysis in the LOCA topical report to account for NIST-2 facility changes and post-test results. (( }}. If the scaling analysis is documented in a different topical report for a certain component, a reference to that report may be appropriate (e.g., reference to the non-LOCA topical report for the EM and assessment of the decay heat removal system (DHRS)). Question LOCA.LTR-2 Issue The LOCA methodology does not provide an adequate basis for model validation vs. test data (( }}. Riser holes have an impact on thermal hydraulic conditions, for example but not limited to, initial conditions, natural circulation and RCS response; these impacts and any others need to be addressed. Information Requested a) Provide justification via sensitivity studies demonstrating that NRELAP5 can adequately calculate the actual expected NPM response with respect to the integrated topical report model. (( }}. The potential impact on the RCS response and conditions for the integrated model on the figures of merit calculated by the topical report model and downstream activities should be shown analytically as described below:
- i.
Provide sensitivities and evaluations of the impact of riser holes on the integral effects tests responses used for Evaluation Model validation for the LOCA topical report. The various impacts of riser holes on the integral test validation response should be captured in the impacts on the integrated NRELAP5 evaluation model results for LOCA analyses. ii. Provide sensitivities and evaluations for the impact of riser holes on the total integral response of the LTR models (LOCA, non-LOCA and XPC) to various design basis events and conditions that show that the test validation response to riser holes is captured. The impact on the RCS response and conditions for the integrated model on the figures of merit calculated by the LOCA, non-LOCA and XPC topical report models should be shown analytically.
5 b) Revise the LTRs to include the above information. Question LOCA.LTR-53 Issue As a result of the NRC staffs Quality Assurance Program (QAP) implementation inspection in February 2024, the NRC staff understands that the LOCA LTR is controlled as a licensing product within NuScale, and the document itself is not considered to be the LOCA Evaluation Model (EM). It is the NRC staffs understanding that information presented in the LOCA LTR are derived from engineering documents. As such, the NRC staff needs to determine if there is information presented or conclusions stated in the LOCA LTR, which is drawn from engineering documents that are not subject to design verification consistent with 10 CFR 50 Appendix B in accordance with Part II, Quality Assurance Program Description Details, Section 2.3.1, Design Verification of Topical Report MN-122626, Revision 1-A, NuScale Power, LLC Quality Assurance Program Description (ML24033A318) (hereafter referred to as QAPD LTR). This includes information subject to Part III, Nonsafety-Related Structures, Systems, and Components (SSC) Quality Control, Section 3.1.3, Design Control in the QAPD LTR, regardless of whether the verification process has been conducted in accordance with this section of the QAPD LTR, since the Section 3.1.3 verification is not required to conform to 10 CFR 50 Appendix B. Information Requested Provide a list of any such documents as described above. For any of these documents not already available in eRR for staff audit, please make those additional documents available for audit. NuScale may choose to provide any relevant information regarding which portions of the LTR or conclusions those documents support. In addition, provide a listing of any section of the LOCA LTR that are either not considered part of the EM or not directly supported by engineering documents that are part of the EM.}}