Document: NUREG-0800
Document ID: 4865fc6d-b85f-4173-9bca-162fa9fe67d2
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500555.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
ard Application of the Single-Failure Criterion to Nuclear Power Generating Station Safety Systems," providing supplements and an interpretation. Reg. Guide 1.153 "Criteria for Power, Instrumentation, and Control Portions of Safety Systems," endorses IEEE Std 603, "IEEE Standard Criteria for Safety Systems for Nuclear Power Generating Stations," as an alternative to ANSI/IEEE Std 279. NUREG-0493 is the first formal defense-in-depth and diversity assessment of a reactor protection system, the RESAR-414. NUREG/CR-6303, "Method for Performing Diversity and Defense-in-Depth Analyses of Reactor Protection Systems," documents several D-in-D&D analyses performed after 1990, and presents a method for performing such analyses. The Staff Requirements Memorandum on SECY 93-087 describes the NRC position on defense-in-depth and diversity. 3. Purpose The purpose of this branch technical position is to provide guidance for review of an applicant/licensee's D-in-D&D assessment and design of manual controls and displays to ensure that the requirements of the NRC position on D-in-D&D for I&C systems incorporating digital computer-based reactor trip systems (RTS) or engineered safety features actuation systems (ESFAS) are followed. This branch technical position has three objectives: • To verify that adequate diversity has been provided in a design to meet the criteria established by the NRC's requirements. • To verify that adequate defense-in-depth has been provided in a design to meet the criteria established by the NRC's requirements. • To verify that the displays and manual controls for critical safety functions initiated by operator action are diverse from computer systems used in the automatic portion of the reactor protection system and ESFAS. Appendix 7-A Rev. 4 — June 1997 BTP HICB-19-3 B. Branch Technical Position 1. Introduction Based on experience in detailed reviews, the Staff has established acceptance guidelines for D-in-D&D assessments. The Staff has