Document: NUREG-0800
Document ID: a59a01e7-d1e2-4946-bebf-a5fff5731c47
Document Type: srp
Title: of the SAR.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500493.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.3
CFR Part: 
CFR Title: 

Content:
d from Staff Requirements Memoranda (SRM) and the associated SECY memoranda. Specific positions are not necessarily separated from explanatory material in these documents. The quotes given here do not include the explanatory material provided in the SECY or SRM. The quotes may also combine material from the SRM and SECY to fully represent the NRC position. a. Item II.Q, "Defense Against Common-Mode Failures in Digital Instrumentation and Control systems" of Staff Requirements Memorandum on SECY-93-087, “Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs” 1. The applicant shall assess the defense-in-depth and diversity of the proposed instrumentation and control system to demonstrate that vulnerabilities to common-mode failures have adequately been addressed. 2. In performing the assessment, the vendor or applicant shall analyze each postulated common-mode failure for each event that is evaluated in the accident analysis section of the SAR using best-estimate methods. The vendor or applicant shall demonstrate adequate diversity within the design for each of these events. 3. If a postulated common-mode failure could disable a safety function, then a diverse means, with a documented basis that the diverse means is unlikely to be subject to the same common-mode failure, shall be required to perform either the same function or a different function. The diverse or different function may be performed by a non-safety system if the system is of sufficient quality to perform the necessary function under the associated event conditions. 4. A set of displays and controls located in the main control room shall be provided for manual, system- level actuation of critical safety functions and monitoring of parameters that support the safety functions. The displays and controls shall be independent and diverse from the safety computer system identified in items 1 and 3 above. Applicability — RTS, ESFAS, diverse