Document: NUREG-0800
Document ID: 1df526d9-2ae0-4da2-b936-2e24b038ca8c
Document Type: srp
Title: DIVERSE INSTRUMENTATION AND CONTROL SYSTEMS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070650035.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.8
CFR Part: 
CFR Title: 

Content:
procedures. • Independence from the protection systems - Diverse actuation systems functions should be independent and diverse from the RTS and ESFAS. ATWS mitigation systems should be diverse from the RTS. For ATWS mitigation systems, 10 CFR 50.62 requires diversity from the sensor output to the final actuation device. See SRP Appendix 7.1-C, subsections 5.6 and 6.3 and SRP Appendix 7.1-B, subsection 4.6. • Potential for inadvertent actuation - The diverse I&C systems design should limit the potential for inadvertent actuation and challenges to safety systems. • Manual initiation capability - The ATWS mitigation systems and DAS should include the capability for initiation from the control room. • Completion of protective action - The ATWS mitigation logic and DAS should be designed such that, once initiated, the mitigation function will go to completion. • D3 analysis - The I&C functions credited with providing diversity should be consistent with the assumptions of the applicant/licensee’s D3 analysis. For example, diverse I&C system equipment should be environmentally qualified for the environments in which the D3 analysis assumes they will operate. When a D3 analysis is not provided, the following diversity criteria should be met: - Equipment diversity should be provided to the extent reasonable and practicable to minimize the potential for common-cause failures. - Equipment diversity is required from the sensors/transmitters to and including the components used to interrupt control rod power or vent the scram air header. - For interruption of control rod power, obtaining circuit breakers from different manufacturers is not, in and of itself, sufficient to provide the required diversity. - For mitigating systems other than diverse RTSs (e.g., auxiliary feedwater), diversity is required from the sensors to, but not including, the final actuation device. - Sensors need not be of a diverse design or manufacturer. 7.8-8 Revision 5 - March 2007 - Existing