Document: NUREG-0800
Document ID: 44d6a58e-60c4-48dc-ac30-11a77c1b190a
Document Type: srp
Title: B-4
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550087.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.1
CFR Part: 
CFR Title: 

Content:
Revision 5 - March 2007 Clause 3(2) of IEEE Std. 279-1971 requires in part the identification of variables that are monitored in order to provide protective action. The tables in Sections 7.2 and 7.3 of the SAR should provide this information. Clause 3(3) of IEEE Std. 279-1971 requires in part the identification of the minimum number and location of sensors for those variables in Clause 3(2) of IEEE Std. 279-1971 that have a spatial dependence. The applicant/licensee's analysis should demonstrate that the number and location of sensors are adequate. Subsection 4.2 below discusses the consideration of the single failure criterion in the evaluation of this analysis. Clauses 3(4), 3(5), and 3(6) of IEEE Std. 279-1971 require in part the identification of operational limits, the margin between operational limits, and the level for the onset of unsafe conditions (setpoint), and limits that require protective action (safety limit - i.e., value assumed in the safety analysis) for each variable. The applicant/licensee's analysis should confirm that an adequate margin exists between operating limits and setpoints, such that a low probability exists for inadvertent actuation of the system. The applicant/licensee's analysis should confirm that an adequate margin exists between setpoints and safety limits, such that the system initiates protective actions before safety limits are exceeded. Regulatory Guide 1.105, "Setpoints for Safety-Related Instrumentation," and BTP 7-12 provide guidance on the establishment of instrument setpoints. The instrument performance data used in setpoint analyses should be consistent with the performance requirements established in the design basis as discussed in Clause 3(9) of IEEE Std. 279-1971. BTP 7-6 provides specific guidance for determining if the timing margins for changeover from injection to recirculation mode are sufficient to allow manual initiation of the transition. Clause 3(7) of IEEE Std. 279-1971 requires in part that the range of