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:
most significant failure modes of the DI&C are documented with a description of the sequence of events that need to take place to fail the system. The sequence of events should realistically represent the system’s behavior at the level of detail of the model. C. The DI&C system CCF events should be identified by the applicant and the bases for grouping of CCFs should be provided. Review the discussion of how the applicant determined the probabilities associated with CCFs. The PRA reviewer should work closely with the I&C reviewer responsible for implementing SRP Section 7.1, “Fundamental Design Principles,” to evaluate the applicant’s justifications. 19.0-28 Revision 3 – December 2015 D. Uncertainties in DI&C modeling and data should be addressed in the DI&C risk assessment. It is expected that the DI&C risk assessment will address uncertainties by at least performing a number of sensitivity studies that vary modeling assumptions, reliability data, and parameter values both at the component and system level. The reviewer should evaluate the sensitivity studies performed by the applicant on the PRA models and data to assess the effect of uncertainty on CDF, risk, and PRA insights. Sensitivity studies may be particularly helpful in assessing the effectiveness of design attributes. Additional support for the review and treatment of uncertainties is provided by NUREG-1855, Volume 1, Main Report: “Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision Making,” dated March 2009. E. The DI&C reviewer should confirm that DI&C system equipment is capable of meeting its safety function in environments associated with accident sequences modeled in the PRA. This is done in collaboration with the reviewer for the PRA and severe 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,