Validation of the CATHARE 3 code based on Rod Bundle Heat Transfer (RBHT) benchmark data using two-fluid and three-field models
Résumé
The Rod Bundle Heat Transfer (RBHT) facility at the Pennsylvania State University has provided data since 2001 for the study and modeling of reflood conditions. The RBHT experiment allows to study predominant phenomena for this kind of transient scenario: effect of the spacer grids, impact of the heat transfers (convection/vaporization/radiation), influence of droplet size and breakups. In the context of a benchmark organized by the OECD/NEA, new data were recently produced, including tests with oscillating boundary conditions, typical of reflooding scenarios. For the CEA, which develops and validates the CATHARE 3 system code, these data are a valuable aid for the development and the validation of reflooding models (interfacial friction, heat transfers, droplet size, film sputtering). The instrumentation of the experiment (which enable to record the clad temperature, the vapor temperature or the droplet diameter) allows a relative separation of the different effects acting on the transient. This article is therefore a validation study of the CATHARE 3 code on the RBHT open test series, using both two-fluid model and the three-field model, where the liquid phase is split into a continuous field and a dispersed field (droplets), implemented in the code. In general, quench front and wall temperatures evolutions are correctly predicted, except for the tests at high reflooding rate. An analysis of models and their limits is proposed, as well as a sensitivity analysis. Particular attention is paid to the differences between the two-fluid model and the three-field model.
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