Document: NUREG-0800
Document ID: 14c7085e-8b87-4b50-97fb-a095ea003ae8
Document Type: srp
Title: describes the general procedures to be followed in reviewing any I&C system. Procedures for
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500511.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.1
CFR Part: 
CFR Title: 

Content:
m the RTS from the sensor output to the final actuation device. See Appendix 7.1-B item 8 or Appendix 7.1-C item 24. • Manual initiation capability — The ATWS mitigation systems should include the capability for initiation from the control room. • Completion of protective action — The ATWS mitigation logic should be designed such that once ATWS mitigation is initiated the mitigation will go to completion. If the applicant/licensee has provided a D-in-D&D analysis, the diversity provided in the ATWS mitigation system design should be consistent with the assumptions of that analysis. Where a D-in-D&D 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-mode 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 reactor trip systems (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. – Existing RTS sensing lines may be used for ATWS mitigation instruments. – Sensors/transmitters and sensing lines should be selected such that adverse interactions with existing control systems are avoided. – Logic and actuation device power for the ATWS mitigation system must be from an instrument power supply independent from the power supplies for the existing RTS; existing RTS sensor and instrument channel power supplies may be used provided the possibility of common-mode failure is prevented. If the ATWS system is explicitly addressed as part of a D-in-D&D analysis, then that