Document: NUREG-0800
Document ID: fe8ec6c2-e960-404c-854f-55c77bde1672
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2400/ML24005A077.pdf
Revision Date: 2024-05
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
ould consider whether the D3 analysis demonstrates that the ATWS system (1) is not vulnerable to the same CCF as the equipment performing the reactor trip function within the proposed DI&C system, (2) is of sufficient quality and is capable of functioning under the event conditions expected, and (3) is responsive to the AOO or PA sequences. If prioritization is used, the reviewer should verify that signals to actuate components coming from the new use of the credited existing I&C system and other systems are adequately prioritized to maintain the overall defense-in-depth strategy and existing licensing basis. The reviewer should also verify that changes to an existing prioritization scheme due to the new use of the credited system are consistent with the existing licensing basis. If there are shared resources (e.g., priority modules), the reviewer should consider whether the credited existing I&C system has priority over the resources (e.g., operational control functions) in regard to its safety and protection functions, so that safety and protection functions are always carried out first. RG 1.152 provides guidance on prioritization of control and protection systems sharing components. (In some cases, certain components may have more than one safe state; the reviewer should consider whether the priority scheme describes all safe states.) BTP 7-19-25 Revision 9 — May 2024 Acceptance Criteria for Crediting Existing I&C Systems If the acceptance criteria below are met, the reviewer should conclude that the application includes a D3 assessment justifying the use of an existing I&C plant system as a diverse means. The existing I&C system may perform the same function as the one disabled by the postulated CCF, or it may perform a different function to compensate for or mitigate the loss of the disabled function. a. If the diverse I&C system uses equipment that is not safety related, the equipment is of sufficient quality to perform the necessary function(s) during the