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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Content:
al 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 50.36(c)(2)(ii)(C), the technical specifications must include limiting conditions of operation (LCOs) for equipment credited in the transient and accident analyses. The reviewer ascertains that the applicant has evaluated the effects of the most limiting single failures and operator errors and that the applicant’s or licensee’s application contains sufficient detail to permit independent evaluation of the adequacy of systems, as they relate to the subject events. A single failure is an occurrence which results in the loss of capability of a component to perform its intended safety functions.7 For single failures in electrical and instrumentation and control (I&C) 6 Emergency response guidelines or emergency procedure guidelines may not be available during initial licensing review. For passive reactor designs, such guidelines are not applicable because operator actions should not be credited in the Chapter 15 safety analysis. 7 Appendix A to 10 CFR Part 50, “Definitions and Explanations,” gives a more complete definition of “single failure.” 15.0-10 Draft Revision 4 – July 2023 components, both passive and active failures should be considered in addition to the initiating event. The failure may be postulated to occur at any time during the event. An active failure in a fluid system means the failure of a component that relies on mechanical movement for its operation to complete its intended function on demand, or an unintended movement of the component. Examples of components that require mechanical movement include air-operated valves, check valves, and pumps. A passive failure in a fluid system means a breach in the fluid pressure boundary or a mechanical failure which adversely affects a flow path. Passive failures in fluid systems should be considered