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
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CFR Title: 

Content:
accident evaluation that provides input on the expected environments that need to be considered. F. The PRA reviewer should confirm that the impact of external events (i.e., seismic, fire, high winds, flood, and others) on DI&C has been addressed in the PRA. The DI&C reviewer confirms that an appropriate failure mode and effects assessment for external hazards has been performed for the purpose of supporting treatment of DI&C in the PRA. A specific concern is the impact of fire on DI&C systems. G. Important scope, boundary condition, and modeling assumptions need to be determined and evaluated. Verify that the assumptions made in developing the PRA model and data are realistic, and that the associated technical justifications are sound and documented. The reviewer should pay attention to assumptions about the potential effects from failure of defensive measures.7 A DI&C defensive measure may have the unintended consequence of causing spurious trips or spuriously failing functional capabilities. The applicant should describe the segregation process that prevents this from occurring. The PRA reviewer should work with the I&C reviewer to evaluate the process discussed by the applicant. H. The PRA reviewer should evaluate the treatment of the recovery actions taken for loss of DI&C functions, referring to RG 1.200 and good practices in human reliability assessment (HRA) for additional guidance. Coordinate the review with staff evaluating areas such as main control room design, and minimum alarms and controls inventory. If recovery actions are modeled, they should consider loss of instrumentation and the time available to complete such action. I. Verify that a method for quantifying the contribution of software failures to DI&C system reliability was used and documented. 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.