Title 10

PART 50 APPENDIX R


Appendix R to Part 50 - Fire Protection Program for Nuclear Power Facilities Operating Prior to January 1, 1979

10:1.0.1.1.30.0.117.88.38 : Appendix R

Appendix R to Part 50 - Fire Protection Program for Nuclear Power Facilities Operating Prior to January 1, 1979 I. Introduction and Scope

This appendix applies to licensed nuclear power electric generating stations that were operating prior to January 1, 1979, except to the extent set forth in § 50.48(b) of this part. With respect to certain generic issues for such facilities it sets forth fire protection features required to satisfy Criterion 3 of appendix A to this part.

Criterion 3 of appendix A to this part specifies that “Structures, systems, and components important to safety shall be designed and located to minimize, consistent with other safety requirements, the probability and effect of fires and explosions.”

When considering the effects of fire, those systems associated with achieving and maintaining safe shutdown conditions assume major importance to safety because damage to them can lead to core damage resulting from loss of coolant through boiloff.

The phrases “important to safety,” or “safety-related,” will be used throughout this appendix R as applying to all safety functions. The phrase “safe shutdown” will be used throughout this appendix as applying to both hot and cold shutdown functions.

Because fire may affect safe shutdown systems and because the loss of function of systems used to mitigate the consequences of design basis accidents under postfire conditions does not per se impact public safety, the need to limit fire damage to systems required to achieve and maintain safe shutdown conditions is greater than the need to limit fire damage to those systems required to mitigate the consequences of design basis accidents. Three levels of fire damage limits are established according to the safety functions of the structure, system, or component:

Safety function Fire damage limits
Hot Shutdown One train of equipment necessary to achieve hot shutdown from either the control room or emergency control station(s) must be maintained free of fire damage by a single fire, including an exposure fire. 1
Cold Shutdown Both trains of equipment necessary to achieve cold shutdown may be damaged by a single fire, including an exposure fire, but damage must be limited so that at least one train can be repaired or made operable within 72 hours using onsite capability.
Design Basis Accidents Both trains of equipment necessary for mitigation of consequences following design basis accidents may be damaged by a single exposure fire.