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:
ill be considered ac ceptable provided their technical basis is demon strated with appropriate data and analyses. 3.9.1 Model Evaluation Procedure for Post-CHF Heat Transfer A model to be used in ECCS evaluation to calcu late post-CHF heat transfer from rod bundles should: a. Be checked against an acceptable set of rele vant data, and b. Recognize effects of liquid entrainment, ther mal radiation, thermal nonequilibrium, low and high mass flow rates, low and high power 1.157-8 densities, and saturated and subcooled inlet conditions. The uncertainties and bias of models or correla tions used to calculate post-CHF heat transfer should be stated as well as the range of their applicability. 3.9.2 Experimental Data for Post-CHF Heat Transfer The acceptable set of relevant data should cover power densities, mass flow rates, fluid conditions, and rod bundle geometries pertinent to light-water re actor designs and applications. The following tests should be considered in establishing an acceptable set of relevant data: "* ORNL tests (Refs. 38 and 39) "* FLECHT-SEASET tests (Ref. 40) "* INEL tests (Ref. 41) "* ORNL data base (Ref. 42) 3.9.3 Post-CHF Heat Transfer from Uncovered Bundles During some time periods of small-break loss-of coolant accidents and during portions of large breaks prior to reflood, partial or complete core uncovering may be calculated to occur. Under these circum stances, special considerations for calculating heat transfer are necessary. 3.9.3.1 Model Evaluation Procedures for Heat Transfer from Uncovered Rod Bundles. A correlation to be used in ECCS evaluations to calculate heat transfer from uncovered rod bundles should: a. Be checked against an acceptable set of rele vant data, and b. Recognize the effects of radiation and of laminar, transition, and turbulent flows. Uncertainties and bias in the models and correla tions used to calculate post-CHF heat transfer should be stated, as should the range of their applicability. The correlation derived