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:
idimensional, single-dimensional approximations justified through sufficient analysis and data may be acceptable. Best estimate methods will be considered acceptable pro vided their technical basis is demonstrated with ap propriate data and analyses. Cooling water that is not expelled, but remains in piping or is stored in parts of the vessel, should be calculated in a best-estimate manner based on applicable experimental data. 3.4.2.1 Model Evaluation Procedure for ECC Bypass. A correlation or model to be used to evaluate ECC bypass should: a. Be checked against an acceptable set of rele vant data, and b. Recognize the effects of pressure, liquid sub cooling, fluid conditions, hot walls, and sys tem geometry. Uncertainties and bias in the correlations or models used to calculate ECC bypass should be stated, as well as the range of their applicability. For scaled-down PWR downcomers, correlations by Beckner and Reyes (Ref. 25) compared well to the bypass data of References 26 and 27. Correla tions of Sun (Ref. 28) and Jones (Ref. 29) compare well to counter-current flow limiting (CCFL) test data of interest to BWRs. 3.4.2.2 Experimental Data for ECC Bypass. The following tests should be considered in establishing a set of data for scaled-down PWR downcomers: "* Battelle Columbus test (Ref. 26) "* Creare test (Refs. 26 and 27) For a full-scale PWR vessel, ECC bypass data will become available from the forthcoming upper plenum test facility (UPTF) experiments performed as part of the 2D/3D program sponsored by the 1.157-7 Federal Republic of Germany, Japan, and the United States. For BWRs, the following test should be consid ered in establishing an acceptable set of relevant data: 0 SSTF test data (Refs. 30 through 32) 3.5 Noding Near the Break and ECCS Injection Point The break location and ECCS injection point are areas of high fluid velocity and complex fluid flow and contain phenomena that are often difficult to cal culate. The results of these calculations are