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:
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 operation. The staff will verify that the applicant has: i. Used a systematic process to identify accident sequences, including significant human errors, that lead to multiple module core damages or large releases and described them in the application ii. Selected alternative features, operational strategies, and design options to prevent these sequences from occurring and demonstrated that these accident sequences are not significant contributors to risk. These operational strategies should also provide reasonable assurance that there is sufficient ability to mitigate multiple core damages accidents. 2. Shutdown and refueling operations for small, modular reactor designs may be performed in ways which are new and completely different from those used at large traditional LWRs either licensed or under review by the NRC. In these cases, a more in-depth review will be needed to assure the validity of the PRA model. Reviewers should confirm that applicants identify and describe all the specific plant operating states (POS) in a refueling outage between the time the output breaker to the grid is opened for plant shutdown and when it is closed to resume power operation after the outage. The reasonableness of the PRA model for low power and shutdown modes of operation cannot be judged without a description of each POS that includes an estimate of the expected time in the POS, a description of the expected changes in configuration of the nuclear steam supply system, a description of the methods of removing heat from the fuel during each POS, a description of the automatic and human actions expected to occur during each POS and an assessment of the potential upset conditions and human errors during each POS that could contribute to a loss of decay heat removal. Design-Specific