Document: NUREG-0800
Document ID: ecf7a8d4-0097-4a93-8609-630545f03f70
Document Type: srp
Title: REGULATORY TREATMENT OF NONSAFETY SYSTEMS FOR PASSIVE
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1308/ML13081A756.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.3
CFR Part: 
CFR Title: 

Content:
those sections, to verify that the applicant has correctly identified the SSCs that require evaluation of risk-significance based on their contribution to initiating event frequencies. The staff then verifies that the applicant has completely addressed the following screening criteria for assessing risk significance of those SSCs with respect to initiating event frequency: a. Does the calculation of the initiating event frequency consider the nonsafety-related SSCs? b. Does the unavailability of the nonsafety-related SSCs significantly affect the calculation of the initiating event frequency? c. Does the initiating event significantly2 affect the CDF and the LRF? The staff verifies that the applicant has included nonsafety-related SSCs in the scope of the RTNSS program that satisfy the screening criteria listed above (RTNSS “C”). 6. The PRA and Severe Accident staff reviews the applicant’s evaluation of potential uncertainties associated with assumptions made in the PRA regarding passive systems and verifies that the applicant has included nonsafety-related SSCs in the scope of the RTNSS program to compensate for the uncertainties in the PRA and in the modeling of severe accident phenomenology, or provided a reasonable justification for not doing so (RTNSS “C”). 7. The staff verifies that the applicant included any nonsafety-related SSCs credited in meeting the Commission’s containment performance goals in the scope of the RTNSS program (RTNSS “D”). The goals are: 2 An SSC failure that is a dominant contributor to an initiating event is significant if the initiating event contributes 10 percent or more to at-power or shutdown internal events CDF. 19.3-11 Draft Rev.0 – June 2013 a. The containment should maintain its role as a reliable, leak-tight barrier by ensuring that containment stresses do not exceed American Society of Mechanical Engineers service level C limits for a minimum period of 24 hours following the onset of core damage, and that