Scaling analyses of a SB-LOCA counterpart test between BETHSY and LSTF facilities and a three loops PWR

The objective of this work is to revisit the scaling analysis of a 6% Cold Leg break LOCA transient of a pressurized water reactor (PWR) using the results of a counterpart test and the support of post-test calculations with a system code. The 6.2-TC and SB-CL-21 tests performed respectively on the French BETHSY facility and the Japanese LSTF-ROSA-IV facility are analyzed. Experimental and calculated results are presented. A comparison is made with the simulation results of a commercial PWR. The transient is divided into five phases and important bifurcating events are identified. In the present work, a phenomenological analysis of the transient is conducted. The Fractional Scaling Analysis (FSA) methodology is applied at system and component scales by writing mass and pressure equations for the whole primary system and for the pressurizer. The CATHARE system thermal hydraulic code is used to estimate the effect metrics specific to this method. The relative weight of the processes that control the mass and pressure are evaluated. Some conclusions are drawn on the presence of possible distortions between the transients in the facilities and in the full-scale reactor. The key point of this study is to show the applicability of a modern top-down approach scaling method, supported by code calculations at different scales.