Document: NUREG-0800
Document ID: 1877a6e5-f5a2-4394-bd63-c323831e96d0
Document Type: srp
Title: INTRODUCTION - TRANSIENT AND ACCIDENT ANALYSES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2231/ML22319A149.pdf
Revision Date: 2023-07
Chapter: 15
Section ID: 15.0
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nly safety-related systems or components for use in mitigating AOO and postulated accident conditions and has included the effects of single failures in those systems and components. In the event that applicants or licensees propose an exception to allow credit for the operation of certain non-safety-related equipment, the reviewer should review the technical justification and ensure the safety analysis does not credit the non-safety-related SSC as a frontline mitigating system or as being within the primary success path necessary for satisfying the acceptance criteria in Table 15.0-1. For instance, NUREG-0138 (Ref. 9), Issue 1, discusses credit for non-safety-related components in the main steam and feedwater systems as a backup protection when the single failure criterion is applied to the analysis of a postulated main steam line break. NUREG-0138 contains guidance on considerations for component type and reliability, and technical specification surveillance requirements. Considering the set of permissible equipment operating configurations applicable to each event, the reviewer verifies that the applicant has analyzed the performance of non-safety-related systems or components in the operating condition that leads to the most limiting results. For instance, the reviewer should verify that the analysis considers non-safety-related systems normally in operation at the time of the event as continuing to function; such systems should not be assumed to experience a random and independent failure that would result in the prevention or termination of the event (e.g., assumed continued operation of the main feedwater control system for the analysis of inadvertent control rod withdrawal event). Non-safety-related systems that are in a standby mode during normal operation should not be considered a primary success path or support a mitigating system in the safety analysis. For LAR, OL, DC, and COL reviews, in accordance with Criterion 3 specified in 10 CFR