ML25139A545
| ML25139A545 | |
| Person / Time | |
|---|---|
| Issue date: | 05/21/2025 |
| From: | Palmtag S Advisory Committee on Reactor Safeguards |
| To: | Walter Kirchner Advisory Committee on Reactor Safeguards |
| References | |
| Download: ML25139A545 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 May 21, 2025 MEMORANDUM TO:
Walter L. Kirchner, Lead NuScale Design-Centered Subcommittee Advisory Committee on Reactor Safeguards FROM:
Scott P. Palmtag, Member NuScale Design-Centered Subcommittee Advisory Committee on Reactor Safeguards
SUBJECT:
INPUT FOR ACRS REVIEW OF THE NUSCALE US460 STANDARD DESIGN APPROVAL APPLICATION - SAFETY EVALUATION REPORT WITH NO OPEN ITEMS FOR CHAPTER 4, REACTOR In response to the Subcommittees request, I have reviewed the NRC staffs safety evaluation report (SER) provided to support ACRS review of the standard design approval application (SDAA), with no open items for Chapter 4, Reactor. The following is my recommended course of action concerning further review of this chapter of the SDAA and the staffs associated SER.
SER Summary Chapter 4 of the SER documents the staffs review of Revision 2 of Chapter 4, Reactor, of the NuScale SDAA Final Safety Analysis Report.
The NuScale Power Module (NPM) is a self-contained nuclear steam supply system composed of a reactor core, a pressurizer, and two steam generators integrated within the reactor pressure vessel and housed in a compact steel containment vessel. Chapter 4 provides a summary of the reactor and reactor core design, fuel rod and fuel assembly design, nuclear and thermal-hydraulic design, and other system designs included in the power module.
The staff has completed a thorough review of this chapter and has concluded that the NuScale design elements therein and associated combined license items met regulatory criteria.
Discussion The fuel and core design of the NPM in the US460 design are fundamentally the same as the US600 design approved in the DCA, with the notable increase in the power from 160 MWt to 250 MWt. Minor modifications were made to the fuel design to account for the power increase and the nuclear methods have been updated to cover the new core operating parameters, such as increased pressure, temperature and flow rates. A new critical heat flux correlation (NSPN-1) has been adopted to account for the new thermal-hydraulic conditions.
W.
Other notable changes to the US460 design include significant improvements to the emergency core cooling system (ECCS). One of the ECCS changes is the addition of an emergency core cooling system supplemental boron (ESB) system, which provides additional boron to aid in reactor shutdown in case of ECCS activation. As a result of the addition of the ESB, the US460 design does not require an exception to General Design Criterion 27, which was requested for the previous US600 design. Another change is the inclusion of additional holes and slots to the NPM core riser barrel to maintain a flow of borated water to the downcomer. The changes to the ECCS were reviewed as part of the review of the Extended Passive Cooling (XPC) and Reactivity Control Methodology, Topical Report. Additional comments on the XPC topical report are covered in the Chapter 15 Transient and Accident Analyses summary.
The staffs review of these and other changes reflected in the US460 design, as compared to the US600 certified design, was thorough with well supported conclusions throughout.
Member questions and concerns were addressed by both the applicant and staff during the April 1, 2025, subcommittee meeting on Chapters 1, 4, and 15. A separate review of the XPC topical report was performed during a separate subcommittee review on March 4, 2025. The Committees April 2025 summary report (Reference 6) documents its review of the XPC and Reactivity Control Methodology, Topical Report.
Recommendation As lead reviewer for NuScale Chapter 4, I recommend that the Committee not perform any additional review of this chapter.
References
- 1. U. S. Nuclear Regulatory Commission, Safety Evaluation of NuScale SDAA Chapter 4, Reactor, March 26, 2025 (ADAMS Accession No. ML24338A158).
- 2. NuScale Power, LLC, Standard Design Approval Application, Part 2, Chapter 4, Reactor, Revision 1, October 31, 2023 (ADAMS Accession Nos. ML23304A335 (Public)
ML23304A337 (Non-Public)).
- 3. NuScale Power, LLC, Submittal of Chapter 4 US460 Standard Design Approval Application Revision 1 to Revision 2 Snapshot, March 17, 2025 (ADAMS Accession No. ML25076A572).
- 4. U. S. Nuclear Regulatory Commission, Safety Evaluation of NuScale Topical report TR-124587, Revision 0, Extended Passive Cooling and Reactivity Control Methodology, February 25, 2025 (ADAMS Accession Nos. ML25051A242 (Public) ML24355A061 (Non-Public)).
- 5. NuScale Power, LLC, TR-124587, Extended Passive Cooling and Reactivity Control Methodology, Revision 0, January 5, 2023 (ADAMS Accession Nos. ML23005A308 (Public)
ML23005A309 (Non-Public)).
- 6. Advisory Committee on Reactor Safeguards, Summary Report - 724th Meeting of the Advisory Committee on Reactor Safeguards, April 2-3, 2025, May 16, 2025 (ADAMS Accession No. ML25121A302).
W.
May 21, 2025
SUBJECT:
INPUT FOR ACRS REVIEW OF THE NUSCALE STANDARD DESIGN APPROVAL APPLICATION - SAFETY EVALUATION WITH NO OPEN ITEMS FOR CHAPTER 4, REACTOR Package Accession No: ML25091A091 Accession No: ML25139A545 Publicly Available (Y/N): Y Sensitive (Y/N): N If Sensitive, which category?
Viewing Rights:
NRC Users or ACRS only or See restricted distribution OFFICE ACRS SUNSI Review ACRS ACRS NAME MSnodderly MSnodderly LBurkhart (MSnodderly for)
SPalmtag DATE 5/20/25 5/20/25 5/20/25 5/21/25 OFFICIAL RECORD COPY