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
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CFR Title: 

Content:
ing procedures applied to detailed first-principle models. These models often represent processes that occur on length and time scales that are too small to be resolved in the computation or processes that we do not have sufficient understanding to model from first principles. These models require closure relationships based on information from experimental measurements or detailed first-principle calculations. The reviewers should ensure that the range of validity of the closure relationships is specified and is adequate to cover the range of conditions encountered in the accident scenario. This is especially true of empirical correlations that are derived directly from experimental data without recourse to any physical modeling. In most applications, especially those with a large number of processes and parameters, it is difficult, if not impossible, to design test facilities that preserve total similitude between the experiment and the nuclear power plant. Therefore, optimum similarity criteria are identified and scaling rationales developed for selecting existing data or designing and operating experimental facilities. The reviewers should confirm that the similarity criteria and scaling rationales are based on the important phenomena and processes identified by the accident scenario identification process and appropriate scaling analyses. The reviewers should confirm that scaling analyses were conducted to ensure that the data and the models will be applicable to the full scale analysis of the plant transient. Scaling compromises that are identified must be addressed in the bias and uncertainty evaluation. The experimental data base must be demonstrated to be sufficiently diverse, so that the expected plant specific response is bounded and that the evaluation model calculations are comparable to the corresponding tests in non-dimensional space. This demonstration allows extending the conclusions relating to code capabilities, drawn from assessments comparing