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:
omena must be consistent with the results of this process. For example, if the accident scenario identification process determines that a certain physical phenomenon is important to the scenario under consideration, the code must have a relatively accurate model for that phenomenon and a detailed assessment of that model must be provided. Phenomena that have lower ranking may be represented by models with larger inherent uncertainty. The formality and complexity of this process should be commensurate with the complexity and importance of the event under consideration. 3. Code Assessment. Assessments of all code models intended to be used in the evaluation model must be provided. All assessments must be performed with the frozen version of the evaluation model that has been submitted for review. Assessments 15.0.2-5 March 2007 performed with other versions of the evaluation model should be justified on a case by case basis because even “small” changes to the evaluation model can have unintended consequences on calculation results that were thought to not be impacted by the changes. Separate effects testing must be performed to demonstrate the adequacy of the physical models to predict physical phenomena that were determined to be important by the accident scenario identification process. Separate effects testing must also be used to determine the uncertainty bounds of individual physical models. Integral effects testing must be performed to demonstrate that the interactions between different physical phenomena and reactor coolant system components and subsystems are identified and predicted correctly. Assessments against both separate effects tests and integral effects tests must be performed with the code. All models need to be assessed over the entire range of conditions encountered in the transient or accident scenario. Assessments must also compare code predictions to analytical solutions, where possible, to show the accuracy of the numerical methods used to