Document: NUREG-0800
Document ID: 2bca792d-0e88-4e2d-b437-be572ed57a48
Document Type: srp
Title: REVIEW OF TRANSIENT AND ACCIDENT ANALYSIS METHODS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0708/ML070820123.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.0.2
CFR Part: 
CFR Title: 

Content:
antities. Even when the mathematical equations conserve mass, momentum, and energy, the numerical method used to solve the equations may not conserve any of these quantities. The reviewers should also confirm that all code options that are to be used in the accident simulation are appropriate and are not used merely for code tuning. The reviewers should ensure that all code closure relationships based in part on experimental data or more detailed calculations have been assessed over the full range of conditions encountered in the accident scenario by means of comparison to separate effects test data. Scaling analyses may be needed to demonstrate that the assessment results apply to the full-scale plant accident conditions. Even closure relationships such as equations of state and material properties, which are based on interpolating functions, need to be assessed against standards for the properties. For example, a relatively small error in thermodynamic properties such as phasic densities as a function of temperature and pressure may cause a larger error when propagated to a neutron kinetics model in a main steamline break or an anticipated transient without scram (ATWS) calculation. 15.0.2-11 March 2007 The reviewers should ensure that integral test assessments properly demonstrate physical and code model interactions that are determined to be important for the full size plant accident scenarios. The integral test will usually not be full-scale, and therefore will contain scaling distortions. These distortions can affect both local and overall elements of the analysis, such as two-phase flow regime transitions and global dynamic response of the test facility, when compared to the full scale plant. The reviewers should ensure that the documentation contains comparisons of all important experimental measurements with the code predictions in order to expose possible cases of compensating errors. Such errors may result in good predictions of key parameters, derived