Document: NUREG-0800
Document ID: 643ab154-682e-480f-a57b-a5fd7390a34e
Document Type: srp
Title: REVIEW OF TRANSIENT AND ACCIDENT ANALYSIS METHODS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0535/ML053550265.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.0.2
CFR Part: 
CFR Title: 

Content:
ly acceptable model. b. The complexity of the event being analyzed. 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. 15.0.2-15 Initial Issuance - December 2005 6.1 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 would be an example of a significant change that would require an extensive review for the new evaluation model. 6.2 Complexity of the event The level of effort involved in applying the development process should be commensurate with the complexity of the evaluation model. At first glance the review process may seem too