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:
tial 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 IN 91-41 (Ref. 28). 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 Reactors (BWRs). 5. The staff reviews the low power and shutdown Level 2 analysis using methods similar to the at power assessment, considering (1) an estimation of containment capacity 19.0-27 Draft Revision 3 –November 2014 considering the capacity of any temporary penetrations, and (2) the feasibility of operators to close containment before adverse environmental conditions prevent closure. The staff reviews the low power and shutdown internal flood and internal fire analysis using methods similar to the at power assessment, considering (1) each defined plant operational state, (2) the impact of breached or failed fire barriers that could impact a fire area, and (3) the impact of impaired or disabled flood barriers that could impact a flood zone. 6. Accidents during non-power modes of operation generally are not part of the design bases of the facility. Consequently, non-power operations, associated accident sequences and specific accident phenomenology 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 branches that have expertise in particular areas (e.g., systems