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:
5, Attention: Reproduction and Distribution Services Section, or by fax to (301) 415-2289; or by email to DISTRIBUTION@nrc.gov. Electronic copies of this section are available through the NRC's public Web site at http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0800/ , or in the NRC's Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession # ML110550791. NUREG-0800 U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN BRANCH TECHNICAL POSITION 7-19 GUIDANCE FOR EVALUATION OF DIVERSITY AND DEFENSE-IN-DEPTH IN DIGITAL COMPUTER-BASED INSTRUMENTATION AND CONTROL SYSTEMS REVIEW RESPONSIBILITIES Primary – Organization responsible for the review of instrumentation and controls (I&C) Secondary – Organization responsible for the review of reactor systems and the organization responsible for the review of human factors engineering (HFE) A. BACKGROUND Digital instrumentation and control (DI&C) systems can be vulnerable to common-cause failure (CCF) caused by software errors or software developed logic, which could defeat the redundancy achieved by hardware architecture. In NUREG-0493, “A Defense-in-Depth and Diversity Assessment of the RESAR-414 Integrated Protection System,” the U.S. Nuclear Regulatory Commission (NRC) staff documented a diversity and defense-in-depth (D3) analysis of a digital computer-based Reactor Protection System (RPS) in which defense against software CCF (or simply CCF hereafter) was based upon an approach using a specified degree of system separation between echelons of defense. The RPS consists of the Reactor Trip System Revision 6 – July 2012 BTP 7-19-2 (RTS) and the Engineered Safety Features (ESF) Actuation System (ESFAS). Subsequently, in SECY-91-292, “Digital 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