Document: NRC Regulatory Guide
Document ID: 666e1303-0170-4974-a7d6-af27eb586524
Document Type: regulatory_guide
Title: Risk-Informed, Performance-Based Fire Protection for Existing Light-Water Nuclear Power Plants (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2104/ML21048A448.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.205
CFR Part: 
CFR Title: 

Content:
that are proposed in lieu of deterministic requirements.4 For these actions, the additional risk should be submitted with the transition license amendment request and can be deemed acceptable5 because of the previous approval. These previously approved alternatives to the deterministic requirements can be “carried over” into the NFPA 805 licensing basis. However, the additional risk of previously approved recovery actions is considered during transition when evaluating the acceptability of other risk increases resulting from the use of the fire risk evaluation approach. Regulatory Position 2.2.4.3 provides guidance on the base risk. Figure 1 provides a convenient framework to focus the discussion of this concept. The flowchart in Figure 1 starts with a given fire area to which the performance-based approach of NFPA 805, Section 4.2.4.2, is applied (block [1]). The licensee must estimate additional risk of the previously approved recovery actions, compared to the NFPA 805 deterministic criteria, and include it in the 3 The “deterministically compliant plant” has been referred to as “an ideal plant” that may not exist or be feasible in practice. Based on experience with the two NFPA 805 pilot plants, the risk of most variances from the deterministic requirements can readily be evaluated by postulating modifications, such as moving or protecting cables, which would meet the deterministic requirements. This provides the base case against which the added risk of the proposed alternative is evaluated. Because of the great similarity between the deterministic criteria of NFPA 805 and the requirements in Appendix R to 10 CFR Part 50, the compliant configuration should be clear, in most cases. An exception might occur for fire scenarios in which evacuation of the main control room is necessary. The RG addresses this by defining the term “primary control station,” which is used in the NFPA 805 definition of recovery action; see Regulatory Position 2.4. 4