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:
s. 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 as initiating events and during long-term core cooling modes of operation (e.g., degradation and leakage from valve or pump seals). For additional guidance related to applying the single failure criterion to systems and components see SECY-77-439 (Ref. 6), and regarding the current Commission position on the treatment of check valves in passive safety systems see SECY-94-084 (Ref. 11). C. Core, System, and Barrier Performance i. Evaluation Model. The reviewer ensures that the applicant has discussed the evaluation model used and any simplifications or approximations introduced to perform the analyses and identified digital computer codes used in the analysis. If the analysis uses more than one computer code, the applicant should describe the method used to connect the codes. The reviewer verifies that the applicant has included detailed descriptions of evaluation models and digital computer codes or listings by referencing documents that are available to the NRC. The reviewer ensures that the applicant has provided a listing of the topical reports (TRs) that describe models or computer codes used in transient and accident analyses and listed the associated NRC safety evaluations (SEs) approving those TRs. The reviewer checks that implementations of NRC-approved models or codes are within the applicable ranges and conditions and that the applicant has demonstrated compliance with each of the conditions and limitations imposed by the NRC staff in its SEs that approve the TRs. If the applicant or licensee is referencing evaluation models, analytic methods, or digital computer codes that have not been approved for use by the NRC for the intended application, then the reviewer should confirm that the application describes the models, methods, and codes and provides