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:
the effects of fire do not adversely affect the ability to achieve and maintain safe shutdown. Designs incorporating reactor containment buildings should provide fire protection for redundant shutdown systems in the reactor containment building that will ensure, to the extent practicable, that one shutdown division will be free of fire damage. Additionally, new reactor designs should ensure that smoke, hot gases, or the fire suppressant will not migrate into other fire areas to the extent that they could adversely affect safe-shutdown capabilities, including operator actions. 8.3 Passive Plant Safe-Shutdown Condition As discussed in SECY-94-084, the definitions of safe shutdown in the Commission’s regulations and guidelines do not address the inherent limitations of passive RHR systems. In GDC 34, “Residual Heat Removal,” of Appendix A to 10 CFR Part 50, the NRC regulations require that the design include an RHR system to remove residual heat from the reactor core so that specified acceptable fuel design limits are not exceeded. GDC 34 further requires suitable redundancy of the components and features of the RHR system to ensure that the system safety functions can be accomplished, assuming a loss of offsite power or onsite power, coincident with a single failure. Passive reactor designs are limited by the inherent ability of the passive heat removal processes and cannot reduce the temperature of the reactor coolant system below the boiling point of water for heat transfer to occur between the reactor coolant and the heat sink. The plant designs include cooling systems to bring the reactor to cold shutdown or refueling condition; however, these systems are not safety grade. These nonsafety-grade systems (i.e., makeup water to the heat sink and cooldown capability) are necessary to maintain long-term cooling (i.e., beyond 72 hours) and must be capable of accomplishing their respective functions without damage to the fuel as demonstrated by design and analysis.