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:
rnal oxidation from both steam and U0 2 fuel. The data of Reference 11 are considered accept able for calculating the rates of energy release, hydro gen generation, and cladding oxidation for cladding temperatures greater than 1900 'F. 3.2.6 Heat Transfer from Reactor Internals Heat transfer from piping, vessel walls, and inter nal hardware should be included in the calculation and should be calculated in a best-estimate manner. Heat transfer to channel boxes, control rods, guide tubes, and other in-core hardware should also be considered. Models will be considered acceptable provided their technical basis is demonstrated with appropriate data and analyses. 3.2.7 Primary to Secondary Heat Transfer (Not Applicable to Boiling Water Reactors) Heat transferred between the primary and secon dary systems through the steam generators should be considered in the calculation and should be calcu lated in a best-estimate manner. Models will be con sidered acceptable provided their technical basis is demonstrated with appropriate data and analyses. 3.3 Reactor Core Thermal/Physical Parameters 3.3.1 Thermal Parameters for Swelling and Rupture of the Cladding and Fuel Rods A calculation of thle swelling and rupture of the cladding resulting from the temperature distribution in the cladding and from the pressure difference be tween the inside and outside of the cladding, both as a function of time, should be included in the analysis and should be performed in a best-estimate manner. The degree of swelling and rupture should be taken into account in the calculation of gap conductance, cladding oxidation and embrittlement, hydrogen gen eration, and heat transfer and fluid flow outside of the cladding. The calculation of fuel and cladding temperatures as a function of time should use values of gap conductance and other thermal parameters as functions of temperature and time. Best-estimate methods to calculate the swelling of the cladding should take into account spatially varying