ICONE23-1744 USING THE PIRT TO REPRESENT APPLICATION AND VALIDATION DOMAINS FOR CFD STUDIES

Abstract

When using CFD for nuclear safety demonstration purposes, EDF applies a methodology based on physical analysis, verification, validation, application to industrial scale and uncertainty quantification (VVUQ), to demonstrate the quality of, and the confidence in results obtained. By following this methodology, each step must be consistent with the others and with the final goal of the calculations. The physical analysis, based on a PIRT (Phenomena Identification and Ranking Table) dedicated to the specific CFD scenario, has a key role to achieve this consistency. The goal of this paper is to describe a way to visually represent the "validation domain" and "application domain" for CFD scenarios, based on data given by the PIRT. The paper first focuses on how the PIRT can be used to describe and analyse any CFD transient. This leads to a practical definition of validation and application domain, based on the figure of merit, physical phenomena, main parameters and dimensionless numbers. Once the notion of domain is precisely defined, a step by step explanation of how these domains can be represented is given in the form of an exhaustive and quantitative chart. A generic overview of the chart is given to understand how the representation deals with validation hierarchy and application range. The representation is tested on an industrial example of a CFD application; the boron dilution transient. The representation of validation and application domain is based on nuclear reactor safety studies and the synthesis validation report of Code_Saturne (EDF in-house CFD code). An example shows how the representation is an efficient tool to evaluate the state of the art of the validation process by focusing on the overlapping of application domain with validation domain. The authors consider this representation to be a clear and simple decision making tool for those involved in safety demonstration. Decisions such as further development of experimental setup or acceptance of safety studies could be supported by this tool if shared with all parties involved. This paper is focused on CFD applications, but the graphical representation of domains as defined could be easily adapted to other scientific fields with few adjustments.