Document: NUREG-0800
Document ID: 8dd882f4-a34f-4415-acd1-ebb441c72786
Document Type: srp
Title: PROBABILISTIC RISK ASSESSMENT AND SEVERE ACCIDENT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1213/ML12132A481.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
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Content:
iate steam generator (SG) manway open or when nozzle dams are installed in the wrong order. Such configurations may invalidate PRA results. Staff may review NRC Information Notice No. 88-36 (Reference 26) to understand the risks associated with these configurations. 4. The staff reviews the applicant’s implementation of industry guidance for safety during outages provided in NUMARC-91-06 (Reference 4). In particular, the staff should assure that, if the applicant plans to use freeze seals, the potential for loss-of-coolant accidents due to failed freeze seals has been considered in the PRA. The potential for such accidents is discussed in NRC Information Notice No. 91-41 (Reference 25). Reviewers should also confirm the existence of an adequate means to control reactor vessel level and an adequate means to control reactor vessel temperature and pressure during shutdown in Boiling Water Reators (BWRs). 5. Accidents during non-power modes of operation are not part of the design bases of the facility. Consequently, non-power operations, associated accident sequences and specific accident phenomanolgy are not considered in the review of the accident analyses provided in Chapter 15 of the FSAR. Indeed, the staff’s review of the level of safety during non-power modes of operation provided by the design of the facility and operating procedures and controls in place is limited to the review of the PRA for non- power modes of operation. This puts additional burden on the PRA reviewer to pursue issues, as necessary, to assure that the PRA model has fidelity and the assumptions in the risk analyses are justified. In some cases the reviewer may need to engage reviewers from other technical branchs that have expertise in a particular areas (e.g., systems operation, T-H performace, operating experience). Reviewers should therefore be aware of the following issues related to safety during non-power modes of operation: A. Based on previous PRAs, studies by the EPRI and studies