Document: NUREG-0800
Document ID: dd4f84a9-8976-44c4-b631-d7c0254f4efc
Document Type: srp
Title: PROBABILISTIC RISK ASSESSMENT AND SEVERE ACCIDENT EVALUATION FOR
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1416/ML14161A594.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
sed to perform such studies. Applicants frequently use the Modular Accident Analysis Program (MAAP) code for such studies. The staff is aware of T-H modeling issues with the code that could compromise its ability to confirm the validity of the PRA success criteria involving minimal sets of mitigating equipment. Use of this code is acceptable only if sufficient benchmarking studies have been done which compare MAAP results with those of a T-H code the staff has reviewed and approved and show that MAAP is able to capture the important T-H phenomena and the timing of such phenomena in simulations of accident sequences included in the PRA. If a small set of accident scenarios is used in the studies, the reviewer confirms that the applicant has provided an adequate rationale for its selection of scenarios, including a discussion of the criteria used for selection. 2. For passive plant designs, the staff reviews the applicant’s use of the PRA to identify “nonsafety-related,” SSCs that require regulatory treatment (i.e., to support the RTNSS program). Specifically this includes the following evaluations performed by the applicant as described in SRP 19.3: A. Evaluation of the risk significance of nonsafety systems using the Focused PRA B. Evaluation of uncertainties associated with assumptions made in the PRA models of passive systems C. PRA initiating event frequency evaluation Design-Specific PRA (Procedures Specific to Integral Pressurized Water Reactors) 1. For small, modular integral pressurized water reactor designs, the staff reviews the results and description of the applicant’s risk assessment for a single reactor module; and, if the applicant is seeking approval of an application for a plant containing multiple modules, the staff reviews the applicant’s assessment of risk from accidents that could 19.0-25 Draft Revision 3 –November 2014 affect multiple modules to ensure appropriate treatment of important insights related to multi-module design and