Document: NUREG-0800
Document ID: f4b8f0c1-9a14-46be-88c9-a6cb74d64dff
Document Type: srp
Title: Rev. 4 — June 1997
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500499.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
ng additional redundancy. • Isolating the control system from channel failure by using data validation techniques to select a valid control input. 25. Section 7.3 — Completion of Protective Action The Staff review of this item should include review of functional and logic diagrams to ensure that "seal-in" features are provided to enable system-level protective actions to go to completion. The seal-in feature may incorporate a time delay as appropriate for the safety function. Additionally, the seal-in feature need not function until it is confirmed that a valid protective command has been received, provided the system meets response time requirements. 26. Section 6.4 — Derivation of System Inputs A safety system that requires loss of flow protection would, for example, normally derive its signal from flow sensors. A design might use an indirect parameter such as a pressure signal or pump speed. However, the applicant/licensee should verify that any indirect parameter is a valid representation of the desired direct parameter for all events. Rev. 4 — June 1997 SRP 7.1-C-13 Even a directly measured variable should be reviewed and its response to postulated events compared with the credit taken for the parameter in the events for which it provides protection. For both direct and indirect parameters, the applicant/licensee should verify that the characteristics (e.g., range, accuracy, resolution, response time, sample rate) of the instruments that produce the protection system inputs are consistent with the analysis provided in Chapter 15 of the SAR. 27. Section 6.5 — Capability for Testing and Calibration The most common method used to verify the availability of the input sensors is by cross checking between redundant channels that have available readout. When only two channels of readout are provided, the applicant/licensee should state the basis used to ensure that an operator will not take incorrect action when the two channel readouts differ. The