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
CFR Part: 
CFR Title: 

Content:
rts of the Commission's regulations, to delineate techniques used by the staff in evaluating specific problems or postulated accidents, or to pro vide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions different from those set out In the guides will be acceptable If they provide a basis for the findings requisite to the issuance or continu ance of a permit or license by the Commission. This guide was issued after consideration of comments received from the public. Comments and suggestions for Improvements In these guides are encouraged at all times, and guides will be revised, as ap propriate, to accommodate comments and to reflect new Information or experience. Written comments may be submitted to the Regulatory Publications Branch, DFIPS, ARM, U.S. Nuclear Regulatory Commission, Washing ton, DC 20555. use either Appendix K features or a realistic1 evaluation model. These realistic evaluation models2 must include sufficient supporting justification to demonstrate that the analytic techniques employed realistically describe the behavior of the reactor system during a postulated loss-of-coolant accident. Paragraph 50.46(a)(1) also requires that the uncertainty in the realistic evaluation model be quantified and considered when comparing the results of the calculations with the applicable limits in paragraph 50.46(b) so that there is a high probability that the criteria will not be exceeded. This regulatory guide describes models,3 correla tions,4 data, model evaluation procedures, and meth ods that are acceptable-to the NRC staff for meeting the requirements for a realistic or best-estimate calcu lation of ECCS performance during a loss-of-coolant accident and for estimating the uncertainty in that 1For the purpose of this guide, the terms "best-estimate" and "realis tic" have the same meaning. Both terms are used to indicate that the techniques attempt to predict realistic