Document: NUREG-0800
Document ID: 96afb1d6-6ce9-41e4-b4ec-1fc7747bc0b2
Document Type: srp
Title: Revision 8 – January 2021
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2033/ML20339A647.pdf
Revision Date: 2023-05
Chapter: 7
Section ID: 7
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Content:
l control system), these systems need not meet augmented quality standards. However, if the applicant credits NSR systems that are not in continuous use (i.e., that are normally in standby mode), then the reviewer should verify that the applicant demonstrated that the system will reliably perform its intended function. For example, the applicant may credit the plant ATWS system as a diverse means of achieving reactor shutdown, provided that the ATWS system is capable of responding to the same analyzed events as the proposed DI&C system. In this case, the reviewer should 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 system and other systems are adequately prioritized to ensure the overall defense-in-depth strategy and existing licensing basis is maintained. 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 system has priority over the resources in regard to its safety and protection functions, such that these functions are always carried out first. DI&C-ISG-04 provides guidance on prioritization of control and protection systems sharing components. Note: In some cases, certain components may have more than one safe state; the reviewer should consider whether all safe states were described in the priority scheme. Acceptance Criteria If the acceptance criteria below are met, the reviewer should conclude that the