ML18292A581

2018/10/19 Nuscale SMR TR RAIs - Request for Additional Information Letter No. 9578 (Erai No. 9578) Topical Report Thermal Hydraulic Stability 15.9, Srsb

ML18292A581
Person / Time
Site:	PROJ0769
Issue date:	10/19/2018
From:	NRC
To:	NRC/NRO/DLSE/LB1
References
Download: ML18292A581 (3)

Text

Title 10 of the Code of Federal Regulations (CFR), Part 50, Appendix A, General Design Criterion (GDC), "Reactor design," requires that the reactor core and associated coolant, control, and protection systems shall be designed with appropriate margin to assure that specified acceptable fuel design limits (SAFDLs) are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences (AOOs). Title 10 of CFR, Part 50, Appendix A, GDC 12, "Suppression of reactor power oscillations," requires that the reactor core and associated coolant, control, and protection systems shall be designed to assure that power oscillations which can result in conditions exceeding SAFDLs are not possible or can be reliably and readily detected and suppressed. Section 5.6.1 of TR-0516-49417-P, "Neutron Kinetics," describes the reactor kinetics models, but does not adequately describe the methods for determining the nuclear data used in the analysis. NRC staff needs to establish a finding the nuclear data used in the stability analysis is suitable. Accordingly, NRC staff requested additional information related to the methods used for generating the nuclear data in RAI 8802 and RAI 9439. RAI 9439 supersedes the response to RAI 8802 and revises the relevant upstream nuclear design method used for the purpose of generating nuclear data from SIMULATE5 to CASMO5. The NRC staff's evaluation of the response to RAI 8802 determined that (1) it remained unclear unclear how CASMO5/SIMULATE5 was used to determine nuclear parameters related to the kinetics calculation apart from the reactivity coefficients (i.e., delayed neutron fraction, prompt neutron lifetime, and delayed neutron precursor decay constant). Therefore, the staff also requests that the applicant update the TR to (1) describe the methodology for determining all necessary point kinetics parameters, and (2) confirm that point kinetics parameters used in licensing evaluations will be based on NRC-approved nuclear design methods. Additionally, NRC staff requests that the TR be updated to clarify that the stability analysis will account for the most limiting point in cycle and most limiting thermal hydraulic conditions of allowable operation or that conservatively bounding parameters will be used.