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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CFR Title: 

Content:
vision 4 – July 2023 AOOs and postulated accidents considered in previous licensing reviews for currently operating PWR and BWR designs have been grouped into the following seven types: (1) Increase in heat removal from the primary system (2) Decrease in heat removal from the primary system (3) Decrease in RCS flow rate (4) Reactivity and power distribution anomalies (5) Increase in reactor coolant inventory (6) Decrease in reactor coolant inventory (7) Radioactive release from a subsystem or component The reviewer ensures that all relevant accident types for the reactor design under review have been identified and that all potentially limiting events within these categories have been included in the analysis. The reviewer ensures that the analysis of each AOO and postulated accident encompasses a sufficient variety of cases or event scenarios, each designed to produce effects or results that challenge designated acceptance criteria. Depending upon the postulated initial conditions and equipment behavior, a given event may have the potential to challenge multiple acceptance criteria. In some cases, the same assumed initial conditions and equipment behavior will produce limiting conditions for multiple figures of merit. In other cases, different figures of merit will be challenged by different event scenarios. For example, one set of initial conditions and equipment performance assumptions could result in a turbine trip event that yields a high peak RCS pressure, and a different set of assumed conditions for the same AOO could result in minimum thermal margin. The former case tests the acceptance criterion for RCS pressure boundary integrity, while the latter case tests the safety limit that protects fuel cladding integrity. The reviewer considers the possible case variations of AOOs, and postulated accidents presented to verify that the applicant or licensee has identified the limiting cases. The reviewer evaluates applicants’ or licensees’ claims that