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:
d 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 should include a stated procedure for correcting for radiative heat transfer and for estimating the vapor temperatures. The Hot tel procedure cited in Reference 43 is a satisfactory example. The turbulent correlation may be of the general form: Nu = A Rem Prn for higher Reynolds numbers (Re), where the coeffi cients A, m, and n are modifications from the basic Dittus-Boelter form and may be functions of other variables. Pr represents the Prandtl number, and Nu is the Nusselt number. The physical properties may be defined as wall, film, or vapor values. A distinction from, and transition to, laminar convection (i.e., Re <2000) should be made, with a value of the laminar heat transfer for rod bundles that is appropriate for the applicable bundle geometry and flow conditions. Other forms and values, depending on the bun dle geometry and flow conditions, are also appropri ate. 3.9.3.2 Experimental Data for Heat Transfer from Uncovered Rod Bundles. An acceptable set of relevant data for post-CHF heat transfer from uncovered rod bundles should cover power densities, fluid conditions, and rod bundle geometries pertinent to light-water reactor design and application. The following tests should be considered in establishing an acceptable set of relevant data: "* ORNL-THTF tests (Refs. 43 and 44) "* FLECHT-SEASET tests (Refs. 45 and 46) "* ORNL data base (Ref. 42) 3.10 Pump Modeling The characteristics of rotating primary system pumps should be derived from a best-estimate dy namic model that includes momentum transfer be tween the fluid and the rotating member, with vari able pump speed as a function of time. The pump model resistance and other empirical terms should be justified through comparisons with applicable data. The pump model for the two-phase region should be