Document: NUREG-0800
Document ID: 06884384-e650-488f-bf96-f48afd211643
Document Type: srp
Title: Revision 5 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550075.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
y also include automatic calibration tests such as the use of fundamental physical principles in Johnson noise thermometry to calibrate resistance temperature detectors (RTDs). The design of automatic self-test features should maintain channel independence, maintain system integrity, and meet the single-failure criterion during testing. The scope and extent of interfaces between software that performs protection functions and software for other functions such as self-test should be designed to minimize the complexity of the software logic and data structures. The safety classification of the hardware and software used to perform automatic self-testing should be equivalent to that of the tested system unless physical, electrical, and communications independence are maintained such that no failure of the test function can inhibit the performance of the safety function. The positive aspects of self-test features should not be compromised by the additional complexity that may be added to the safety system by the self-test features. The improved ability to detect failures provided by the self-test features should outweigh the increased probability of failure associated with the self-test feature. Self-test functions should be verified during periodic functional tests. Surveillance Testing Systems should be able to conduct periodic surveillance testing consistent with the technical specifications and plant procedures. As delineated in Regulatory Guide 1.118, periodic testing consists of functional tests and checks, calibration verification, and time response measurements. As required by IEEE Std. 279-1971, Clause 4.13, or IEEE Std. 603-1991, Clause 5.8.3, and as stated in Regulatory Guide 1.47, if the protective action of some part of a protection or safety system is bypassed or deliberately rendered inoperative for testing, that fact should be continuously indicated in the control room. Provisions should also be made to allow operations staff to confirm that the system