Document: NUREG-0800
Document ID: b8d2b8f5-432a-4c0a-81ab-20231f7d0f28
Document Type: srp
Title: PROBABILISTIC RISK ASSESSMENT AND SEVERE ACCIDENT EVALUATION FOR
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1508/ML15089A068.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
d. 7 i.e., measures that provide DI&C fault prevention, removal, and tolerance, e.g., memory allocation, network/bus design features, automatic tester system, diagnostics, and data acquisition system. 19.0-29 Revision 3 – December 2015 J. It is important to evaluate claims by applicants regarding the credit that should be given for defensive design features. Verify that key assumptions from the DI&C PRA are captured under the applicant’s design reliability assurance program (D- RAP), which is described in SRP Chapter 17, Section 17.4. The applicant should describe adequately where and how the D-RAP captures the DI&C system key assumptions, such as how future software and hardware modifications will be conducted to ensure that high reliability and availability are maintained over the life of the plant. The following 10 additional steps, as applicable, are included if a more detailed review is needed (e.g., through field audits): A. Verify that physical and logical dependencies are identified and their bases provided in the DI&C PRA. The probabilistic model should encompass all relevant dependencies of a DI&C system on its support systems. For example, if the same DI&C hardware is used for implementing several DI&C systems that perform different functions, a failure in the hardware, software, or system of the DI&C platform may adversely affect all these functions. Should these functions be needed at the same time, they would be affected simultaneously. This impact should be explicitly included in the probabilistic model. The DI&C system probabilistic model should be fully integrated with the probabilistic model of other systems. Coordinate with the I&C reviewer. B. Ensure that spurious actuations of diverse backup systems or functions are evaluated and the overall risk impact documented. C. Common cause failures can occur in areas where there is sharing of design, application, or functional attributes, or where there is sharing of environmental challenges. Review