Document: NRC Regulatory Guide
Document ID: 8e45dce1-e1e7-4415-b1dd-7e2a610e545b
Document Type: regulatory_guide
Title: Fire Protection for Nuclear Power Plants (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2023/ML20231A835.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.189
CFR Part: 
CFR Title: 

Content:
area should have a fire-resistance rating of 3 hours or more and should achieve the following: a. separation of SSCs important to safety from any potential fires in nonsafety-related areas that could affect their ability to perform their safety function; b. separation of redundant trains of systems and components important to safety from each other so that both are not subject to damage from a single fire; and c. separation of individual units on a multiunit site unless the requirements of GDC 5, “Sharing of Structures, Systems, and Components,” in Appendix A to 10 CFR Part 50 are met with respect to fires. The fire hazards analysis should be used to establish fire areas. Particular design attention to the use of separate, isolated fire areas for redundant cables will help to avoid loss of redundant cables important to safety. Separate fire areas should also be employed to limit the spread of fires between components, including high concentrations of cables important to safety that are major fire hazards within a safety division. Where fire area boundaries are not 3-hour rated, or not wall-to-wall or floor-to-ceiling boundaries with all penetrations sealed to the fire rating of the boundaries, the licensee should evaluate the adequacy of the fire area boundaries (i.e., barriers) to determine whether the boundaries will withstand the hazards associated with the area and, as necessary, protect important equipment within the area from a fire outside the area. Unsealed openings should be identified and considered when evaluating the overall effectiveness of the barrier (see Regulatory Position 4.2.1 of this guide for positions related to fire barrier testing and acceptance). If a wall or floor/ceiling assembly contains major unprotected openings, such as hatchways and stairways, plant locations on either side of such a barrier should be considered part of a single fire area. If success path A is separated by a cumulative horizontal distance of 6.1 m (20 ft) from