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:
of fire analyses, have been addressed in NUREG/CR-6850 to the extent allowed by the current state-of-the-art. NUREG/CR-6850 is therefore considered to be a preferable method for performing fire PRA to support applications for design certification or a COL. Reviewers may find that applicants for design certification use an approach to implementing the analysis tasks in NUREG/CR-6850 that is simpler than that suggested in NUREG/CR-6850. This can occur when the specifics of cable routings, ignition sources, and target locations in each fire zone of the plant are not known at the time the design certification application is submitted. Such an approach may be acceptable if conservative assumptions are used such that it is reasonable to conclude that the results bound those expected with the more detailed approach described in NUREG/CR-6850 with respect to CDF and LRF. Examples of conservative assumptions that have been accepted by the staff in previous reviews are listed below: 19.0-29 Draft Revision 3 –November 2014 A. Fire ignition in any fire area continues to grow unchecked into a fully developed fire without credit for fire suppression and causes the maximum possible damage to SSCs in the area. B. Bounding fire initiating event frequencies are applied. C. No credit is taken for the distance between fire sources and targets. D. All fire-induced equipment damage occurs at the beginning of the event. E. Any fire in the switchyard is assumed to result in a reactor trip. F. Although design features have been implemented to prevent spurious actuations induced by a single fire in a building, the PRA may assume that fire propagation in the building will lead to short circuits in electrical equipment that causes spurious actuation of equipment that could cause initiating events or prevent mitigating systems from operating properly. 2. The reviewer confirms that the fire risk analysis uses the same systems and accident sequence models as the internal events evaluation. 3.