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:
e off conservatism in the evaluation model. The intended results of an analysis can be conservative due to a combination of code input and modeling assumptions. The amount of assessment required for a change to an evaluation model may be reduced significantly if the documented degree of conservatism is large or if the new model can be shown to give more conservative results than the previous model. However, conservatism in just one part of the evaluation model such as a heat transfer correlation can not be used to justify conservatism in the evaluation model as a whole because other parts of the model may be non-conservative and cause the overall model to be non-conservative. The degree of conservatism in the overall evaluation model must be quantified and documented for the particular application in order to justify a reduction in assessment requirements using this argument. iv. Extent of plant or operational changes that require a reanalysis The level of effort required to apply the process should be commensurate with the extent of changes made to the plant design or operation. Most of the changes to plant equipment or operations do not cause the plant to operate outside the range of validity of the evaluation model. In this case no additional development and assessment needs to be performed. This may not be the case for all changes. Examples of changes that may require changes to or additional assessment of the evaluation model are fuel bundle design changes (including grid spacer and intermediate flow mixer design changes), increases in the peak linear heat generation rate or operational changes that may cause reliance on a different safety grade trip which requires that accurate prediction of a quantity not required in the previous analysis. In these cases a limited application of the review process similar to that described in section 6.1 should be sufficient. 6. For review of a DC application, the reviewer should follow the above procedures to verify that the