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:
The scope and depth of applying the review process to the evaluation model can be based on a graded approach. The following attributes of the evaluation model should be considered when determining the extent to which the full review process may be reduced for a specific application. A. Novelty of the revised evaluation model compared to the currently acceptable model. B. The complexity of the event being analyzed. 15.0.2-14 March 2007 C. The degree of conservatism in the evaluation model. D. The extent of any plant design or operational changes that would require a reanalysis. Each of these attributes is discussed in the following sections. i. Novelty of the evaluation model or changes to the model The level of effort involved in the review process should be commensurate with the extent of the changes made to an evaluation model. Small changes to a robust time tested evaluation model component such as a change to a simple heat transfer or drag correlation (possibly required by an error correction) may not require a full review of the entire evaluation model. In this case, scaling would only have to be considered within the context of how well the new model scales to full plant analysis if the model is developed from a reduced scale test program. Consideration would also have to be given to how well the assessment cases for the model represent full scale plant conditions. A small subset of the entire code assessment matrix may be adequate to test the phenomenon that are affected by the model changes or the new model. Another subset of the code test cases may need to be performed to ensure that other parts of the model are not inadvertently impacted by the changes. The impact of any changes due to an error correction would have to be evaluated for the current license analysis of record. A large model change may require application of the review process on a much larger scale. Changing models from an equilibrium, drift flux model to a two fluid, non-equilibrium model