ML24346A169
Text
Response to SDAA Audit Question Question Number: A-4.3-10 Receipt Date: 07/05/2023 Question:
Provide detailed information on the reflector design to include the size and number of the water holes in the radial reflector of NPM-20 design and demonstrate that the reflector is modeled conservatively in the core neutronics analyses performed using CASMO5 and SIMULATE5.
Section 4.3 does not include the full description of the reflector design. In response to FISD A-4.3-2, the applicant provided digital format information which includes CASMO5 and SIMULATE5 input and output files for the equilibrium cycle. The CAMSO5 input files include radial reflector models. However, the information does not include the size and number of holes in the reflector. (( 2(a),(c) Please provide markups to the SDAA to include the reflector design and how it is modeled in the core neutronic analyses with the new reflector design.
Response
The NuScale Power Module (NPM) incorporates the use of a stainless-steel heavy reflector with cooling channels in circumference around the reactor core. Figure 1 provides a depiction of the heavy reflector for the NPM-20 design described in the US460 standard design approval application (SDAA). (( }}2(a),(c),ECI Figure 2 provides a depiction of the heavy reflector for the NPM-160 design used for the US600 design certification application (DCA) along with a depiction of the modeling regions for NuScale Nonproprietary NuScale Nonproprietary
CASMO5/SIMULATE5. (( }}2(a),(c),ECI NuScale incorporates a standard modeling approach of the radial reflector in CASMO5/ SIMULATE5 following the method described in Section 3.4.2 of TR-0616-48793-P-A, Revision 1. (( }}2(a),(c) (( }}2(a),(c) The nuclear analysis methodology, described in TR-0616-48793-P-A, Revision 1, applies a best-estimate plus uncertainty approach to nuclear analysis calculations. Nuclear analysis calculations are performed using conservative assumptions and core modeling options, and uncertainties are applied to calculated physics parameters as Nuclear Reliability Factors (NRFs) to provide conservative predictions to the calculated parameters. The NRFs were developed by comparing CASMO5/SIMULATE5 calculated values against empirical benchmarks of experimental reactors, commercial reactor data, and MCNP calculated values. (( }}2(a),(c) (( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c),ECI NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c),ECI As noted in the response and stated in Section 4.3 of the US460 SDAA, the core design is performed following the methodology of TR-0616-48793-P-A, Revision 1. The reflector design in the US460 SDAA is presented with a similar level of detail as the US600 DCA. NuScale Nonproprietary NuScale Nonproprietary
Updated Response The NuScale US460 CASMO5/SIMULATE5 reflector model is updated to incorporate the NPM-20 reflector design. (( }}2(a),(c) The impact of differences in the US600 and US460 reflector designs is insignificant compared to the uncertainties applied through the application of the NRFs. NuScale Nonproprietary NuScale Nonproprietary
Figure 1 Assembly Radial Power Distribution at Beginning, Middle, and End of Cycle with NPM-20 Reflector Design NuScale Nonproprietary NuScale Nonproprietary
Figure 2 Boron Letdown Curve for Equilibrium Cycle with NPM-20 Reflector Design No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}