Document: NRC Regulatory Guide
Document ID: 5f799693-27fd-4e13-a5e1-4c02f393d90a
Document Type: regulatory_guide
Title: Best-Estimate Calculations of Emergency Core Cooling System Performance + HISTORY –HISTORY 04/2013 – Periodic Review of Revision 0 – Reviewed with issues identified for future consideration 03/1987 – Draft RS 701-4, Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003739584.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.157
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CFR Title: 

Content:
r including the uncertainty in the comparisons of the calculational results to the cri teria of paragraph 50.46(b), in order to meet the re quirement that there be a high probability that the criteria would not be exceeded, are also described in this regulatory guide. Paragraph 50.46(a) also per mits licensees to use evaluation models developed in conformance with Appendix K. Other models, data, model evaluation proce dures, and methods will be considered if they are supported by appropriate experimental data and technical justification. Any models, data, model evaluation procedures, and methods listed as accept able in this regulatory guide are acceptable in a ge neric sense only and would still have to be justified to the NRC staff as being appropriately applied and ap plicable for particular plant applications. The regulatory position in this regulatory guide lists models, correlations, data, and model evaluation procedures that the NRC staff considers acceptable for realistic calculations of ECCS performance. It also provides a description of the acceptable features of best-estimate computer codes and acceptable methods for determining the uncertainty in the calcu lations. The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position. Any information collection activities discussed in this regulatory guide are contained as requirements in 10 CFR Part 50, which provides the regulatory basis for this guide. The information collection require ments in 10 CFR Part 50 have been cleared under OMB Clearance No. 3150-0011. B. DISCUSSION The criteria set forth in § 50.46, "Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors," and the cal culational methods specified in Appendix K were promulgated in January 1974 after extensive rulemaking hearings and were based on the under standing of ECCS performance available at that time. In the years following the