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:
ated with appropriate data and analyses. 3.2.1.1 Model Evaluation Procedure for Stored Energy and Heat Transfer in Fuel Rods. A model to be used in ECCS evaluations to calculate internal fuel rod heat transfer should: a. Be checked against several sets of relevant data, and b. Recognize the effects of fuel burnup, fuel pellet cracking and relocation, cladding creep, and gas mixture conductivity. The model described by Lanning (Ref. 8) com pared well to in-pile fuel temperature data. Best estimate models will be considered acceptable provided their technical basis is demonstrated with appropriate data and analyses. 3.2.1.2 Experimental Data for Stored Energy in Fuel Rods and Heat Transfer. The correlations and data of Reference 9 are acceptable for calculating the initial stored energy of the fuel and subsequent heat transfer. 3.2.2 Fission Heat Fission heat should be included in the calculation and should be calculated using best-estimate reactiv ity and reactor kinetics calculations. Shutdown reac tivities resulting from temperatures and voids should also be calculated in a best-estimate manner. The point kinetics formulation is considered an accept able best-estimate method for determining fission heat in safety calculations for loss-of-coolant acci dents. Other best-estimate models will be considered acceptable provided their technical basis is demon strated with appropriate data and analyses. Control rod assembly insertion may be assumed if it is ex pected to occur. 3.2.3 Decay of Actinides The heat from radioactive decay of actinides, in cluding neptunium and plutonium generated during 1.157-5 operation as well as isotopes of uranium, should be calculated in accordance with fuel cycle history and known radioactive properties. The actinide decay heat chosen should be appropriate for the facility's operating history. Best-estimate models will be con sidered acceptable provided their technical basis is demonstrated with appropriate data and analyses. 3.2.4 Fission