The Atomic Energy and Alternative Energies Commission (CEA) is a French Research and Development institution that plays a major role in the French nuclear energy program. CEA has been developing the CATHARE code for 45 years. It is an extensively validated thermal-hydraulic system code based on the 2-fluid 6-equation model. The CEA is currently developing new tools in CATHARE to facilitate its use for scaling analysis, which contribute significantly in the identification of dominant phenomena occurring during reactor accidental transients and in the design of experiments able to simulate major phenomena with minimal distortions. Previous published work on scaling analysis with the CATHARE code focused on the primary mass and primary pressure equations to identify the dominant terms controlling the mass inventory and the system pressure. These terms were calculated “by hand” during the post-processing phase. A new tool enables this analysis to be carried out automatically during a calculation, by fetching the thermal-hydraulics quantities at code execution. The integrated momentum equation along cooling loops is also added to the analysis. As a result, the three main equation of the CATHARE code (mass, momentum and energy) are now available for analysis. This work describes the methodology of the CATHARE scaling analysis, and the way this tool is implemented in the code. The different equation terms, the normalization strategy and the aggregation rules are fixed at code level. It is then applied to a SB-LOCA transient using the scaling equations of mass, momentum and pressure. Figures of merit and available post-processing are presented, which enables the dominant phenomena to be quantified. By reducing the impact of the user in the scaling methodology, the proposed framework significantly improves the consistency and comparability of scaling analyses. Leads for future developments are given.
Cottarel et al. (Sun,) studied this question.