ML25139A525
| ML25139A525 | |
| Person / Time | |
|---|---|
| Issue date: | 05/21/2025 |
| From: | Walter Kirchner Advisory Committee on Reactor Safeguards |
| To: | Walter Kirchner Advisory Committee on Reactor Safeguards |
| References | |
| Download: ML25139A525 (1) | |
Text
UNITED STATES NUCLEAR REGULA TORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 May 21, 2025 MEMORANDUM TO:
Walter L. Kirchner, Lead FROM:
SUBJECT:
NuScale Design-Centered Subcommittee Advisory Committee on Reactor S J
i guarJ [
Walter L. Kirchner, Member
(
it\\ 4-6 L
('\\lt-'t-i. <"
NuScale Design-Centered Subcommittee' L
Advisory Committee on Reactor Safeguards INPUT FOR ACRS REVIEW OF THE NUSCALE US460 STANDARD DESIGN APPROVAL APPLICATION-SAFETY EVALUATION REPORT FOR CHAPTER 1, "INTRODUCTION AND GENERAL DESCRIPTION OF THE PLANT" In response to the Subcommittee's request, I have reviewed the NRC staff's safety evaluation report (SER) provided to support ACRS review of the standard design approval application (SDAA), with no open items for Chapter 1, "Introduction and General Description of the Plant."
The following is my recommended course of action concerning further review of this chapter of the SDAA and the staffs associated SER.
Background
The NuScale US460 SDAA is a power uprate of the individual modules of its US600 design certification application (DCA) and consists of up to six NuScale Power Modules (NPMs) in a single reactor building (RXB). The NPMs are largely immersed in a large pool of borated water in the RXB, which also serves as the ultimate heat sink. Each NPM is a small, integrated, natural-circulation pressurized water reactor composed of a shrouded reactor core and riser, a pressurizer, and two helical-coil steam generators (SGs) within a reactor pressure vessel (RPV),
which is housed integral to a high-strength steel, closely fitting containment vessel (CNV). This design feature eliminates large-diameter piping to connect the SGs and pressurizer to the RPV.
The modularized system can then be moved within the RXB and disassembled for refueling.
The reactor core consists of approximately half-length, commercial 17x17 fuel assemblies (37) and control rod assemblies (16), surrounded by a stainless-steel reflector, and is cooled by natural circulation of the borated, light-water primary coolant. Nominal operating conditions, power peaking, and fuel burnup are below those of the current pressurized water reactor operating fleet. Each NPM is rated at 250 MWt (versus 160 MWt for the US600 DCA), with an output of approximately 77 Mwe. With the power uprate, the nominal operating pressure of the reactor was raised to 2000 psia, and this led to several other design changes, notably the RPV and CNV design pressures and materials selection.
Other unique safety features are: 1) Decay Heat Removal System (DHRS) with two passive trains, each connecting a SG to a heat exchanger immersed in the reactor pool; and 2)