Document: NUREG-0800
Document ID: 106978f1-fb10-4fa9-ad95-601f3c16bd36
Document Type: srp
Title: Revision 5 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550072.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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Content:
lear Regulatory Commission, Washington, DC 20555, 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 # ML070550072. 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 Secondary – Organization responsible for the review of reactor systems A. BACKGROUND Digital instrumentation and control (I&C) systems can be vulnerable to common-cause failures caused by software errors, 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 staff documented a diversity and defense-in-depth (D3) analysis of a digital computer-based reactor protection system in which defense against common-cause failures was based on an approach using a specified degree of system separation between echelons of defense. Subsequently, in SECY 91-292, "Digital Computer Systems for Advanced Light-Water Reactors," the Staff included discussion of its concerns about common-cause failures in digital systems used in nuclear power plants. As a result of the reviews of advanced light-water reactor (ALWR) design certification applications for designs that use digital protection systems, the staff has documented its position with respect to common-cause failures in digital systems and defense-in-depth. This position was documented BTP 7-19-2 Revision 5 - March