Document: NUREG-0800
Document ID: 11a2be5f-50e6-47c7-beee-25b5049ab4bb
Document Type: srp
Title: REACTOR TRIP SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350474.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.2
CFR Part: 
CFR Title: 

Content:
hannel protective action. Where it is determined that the spatial dependence of a parameter requires several sensor channels to assure core protection, the redundancy require- ments are determined for the individual'case. In certain designs adequate monitoring of core power requires a minimum number of sensors arranged in a given configuration to provide adequate protection. This aspect of redundancy is dealt with in coordination with the CPB to establish redundancy requirements. The redundancy requirements when considered strictly from an electrical' point of view, is only necessary to assure that at least two redundant logic trains (minimum degree of redundancy of one) are provided to initiate reactor trip. From this standpoint the review may be reduced to a simple analysis in which redundant paths for sensors to logic and to actuation devices are identified to assure that the RTS functional requirements are met. 7.2-4 Rev. 2 - July 1981 2.- System Conformance with the Single Failure Criterion In evaluating the. adequacy 'of the RTS system in meeting the single failure criterion, both electrical and physical independence must be considered. a. Electrical Independence To assure electrical independence, the design bases governing the electrical independence of redundant sensors, logic elements, and actuation channels are required to satisfy Paragraph 4.6 of IEEE Std 279,.which states that, "channels that provide signals for the same protection function shall be independent, and the likelihood of interaction between channels is considered," and the requirement of Paragraph 4.7.2. This paragraph requires that, "the transmission of signals from protection system channels that are used for other purposes (non-protective), such as control or readout and indi- cation, are properly isolated to ensure that no credible failure at the output of an isolation device shall prevent the associated protective channel from meeting performance requirements." Examples of credible