Document: NUREG-0800
Document ID: dc63e8aa-2a74-4078-9e19-9a26ed1b4d8c
Document Type: srp
Title: Revision 6 – July 2012
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1105/ML110550791.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
tal Computer Systems for Advanced Light-Water Reactors,” the NRC staff included discussion of its concerns about CCF in digital systems used in nuclear power plants (NPPs). As a result of reviews of advanced light-water reactor (ALWR) design certification (DC) applications for designs using digital protection systems, the NRC staff documented its position with respect to CCF in digital systems and D3. This position was documented as Item 18, II.Q, in SECY-93-087, “Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs,” and was subsequently modified in the associated staff requirements memorandum (SRM). On the basis of experience in detailed reviews, the NRC staff has established acceptance guidelines for D3 assessments as described in this branch technical position (BTP). Further guidance reflected herein was established through the efforts of the DI&C Task Working Group #2 on D3 with the development of DI&C-ISG-02, “Task Working Group #2: Diversity and Defense-in-Depth Issues Interim Staff Guidance,” Revision 2. This interim staff guidance (ISG) was developed with extensive review of D3 issues including both internal review within the NRC and external input through public meetings with representatives from industry, vendors, and the general public. In summary, while the NRC considers (software) CCF in digital systems to be beyond design basis, NPPs should be protected against the effects of anticipated operational occurrences (AOOs) and postulated accidents with a concurrent CCF in the digital protection system. 1. Regulatory Basis Title 10 of the Code of Federal Regulations, Section 50.55a(h) (10 CFR 50.55a(h)), “Protection and Safety Systems,” requires compliance with Institute of Electrical & Electronics Engineers (IEEE) Standard (Std.) 603-1991, “IEEE Standard Criteria for Safety Systems for Nuclear Power Generating Stations,” and the correction sheet dated January 30, 1995. For NPPs