Next Generation Safety Analysis Methods for SFRs—(2) Experimental Analyses by SIMMER-III for the Integral Verification of the COMPASS Code on Fuel-Pin Disruption and Low-Energy Disrupted Core Motion

This paper describes experimental analyses using the SIMMER-III computer code, which is a two-dimensional multi-component multi-phase Eulerian fluid-dynamics code. Two topics of key phenomena in core disruptive accidents were presented in this paper: fuel-pin disruption, and low energy disrupted core motion. Related experimental database were reviewed to select appropriate experiments. To analyze the fuel-pin disruption behavior, the CABRI-EFM1 and the CABRI-E7 in-pile experiments were selected. The SIMMER-III calculation was in good agreement with the overall fuel-pin disruption and dispersion behavior, which was characterized by a thermal pin-failure mode, observed in the CABRI-EFM1 experiment. Since the code framework of SIMMER-III cannot treat a mechanical deformation and breakup behavior, the SAS4A code was applied to the CABRI-E7 experiment, where a mechanical pin-failure mode was realized. In this study, such a failure mode was also reasonably simulated. The low-energy disrupted core consists principally of fuel particles and liquid steel (or fuel). Under such a mixture condition, significantly reduced melt penetration length was obtained in the THEFIS out-of-pile experiments. SIMMER-III well simulated the melt freezing and blockage behavior observed in the experiment.