Document: NUREG-0800
Document ID: 2717fe7f-71fd-4f1e-bd08-7685b24763ba
Document Type: srp
Title: Standard Review Plans are prepared for the guidance of the Office of Nuclear Reactor Regulation staff responsible for th
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0301/ML030160606.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15
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Content:
pplication to model situations where radiation heat transfer is not significant even though the field equations are valid. The reviewer must therefore ensure that the field equations of the evaluation model are adequate to describe the set of physical phenomena that occur in the accident and ensure that the closure relationships are valid over the full range of conditions encountered during the accident. The modeling must be consistent with the results of the accident scenario identification process in that there must be models for all important phenomena in the accident scenario. Components and physical phenomena that are identified as being important in the accident scenario identification process must be modeled with a high degree of fidelity. Phenomena of lower importance may be represented by less accurate models. The reviewers should determine if the simplifying assumptions and assumptions used in the averaging procedure are valid for the accident scenario under consideration. Simplifying assumptions and averaging are often applied to detailed physical and mathematical modeling to obtain simplified mathematical models that can be solved more readily and with less computational effort. Examples of common simplifications are incompressible flow models, one-dimensional flow models, common two-phase flow models such as the homogeneous equilibrium model (HEM), drift flux, and the two-fluid model, and simplified reactor kinetics models such as point kinetics or one-dimensional kinetics. Even models commonly thought of as detailed models usually contain simplifying assumptions and averaging procedures applied to first-principles models. Reviewers should confirm that justifications are provided for all simplifications, assumptions, and averaging. The reviewers should confirm that the level of detail in the model is equivalent to or greater than the level of detail required to specify the answer to the problem of interest. For example, a one-dimensional flow model can