Document: NRC Regulatory Guide
Document ID: 30181e34-3bc1-46b8-8de9-ef073c34bc13
Document Type: regulatory_guide
Title: Bypassed and Inoperable Status Indication for Nuclear Power Plant Safety Systems + HISTORY - HISTORY 10/2008 – DG-1205 , Proposed Revision 1 (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0821/ML082140114.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.47
CFR Part: 
CFR Title: 

Content:
ctures, systems, and components of the nuclear power plant, such as by tagging valves and switches, to prevent inadvertent operation. The provisions of 10 CFR 50.34(f)(2)(v), “Additional TMI-Related Requirements,” also require automatic indication of bypassed and operable status of safety systems. IEEE Std 603-1991 uses the term “safety systems” rather than “protection systems” to define its scope. The standard offers the following definition of a “safety system”: “…a system that is relied upon to remain functional during and following design basis events to ensure: (i) the integrity of the reactor coolant pressure boundary, (ii) the capability to shut down the reactor and maintain it in a safe shutdown condition, or (iii) the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the 10 CFR Part 100 guidelines.” In addition, IEEE Std 603-1991 defines a “safety function” as “one of the processes or conditions (for example, emergency negative reactivity insertion, post-accident heat removal, emergency core cooling, post-accident radioactivity removal, and containment isolation) essential to maintain plant parameters within acceptable limits established for a design basis event.” The standard also defines a “division” as “the designation applied to a given system or set of components that enable the establishment and maintenance of physical, electrical, and functional independence from other redundant sets of components.” IEEE Std 279-1971 states that a “protection system” encompasses all electric and mechanical devices and circuitry (from sensors to actuation device input terminals) involved in generating those signals associated with the protective function. These signals include those that actuate a reactor trip and that, in the event of a serious reactor accident, actuate engineered safety features, such as containment isolation, core spray, safety