Abstract
For contaminated water management in decommissioning Fukushima Daiichi nuclear power stations (1F), reduction in water injection, intermittent injection water and air cooling are considered. However, since there are uncertainties of fuel debris in the primary containment vessels (PCVs), it is necessary to examine and evaluate in advance optimal cooling methods according to the distribution state of the fuel debris and the progress of the fuel debris retrieval work.
Japan Atomic Energy Agency (JAEA) has developed a numerical method by using JUPITER for estimating the thermal behavior in the air cooling, including the influence of the position, heat generation and the porosity of fuel debris. It is however difficult to perform the large-scale thermalhydraulics analysis with JUPITER by modeling the internal structure of the debris which may consist of a porous medium. In this study, we added a porous medium model to JUPITER to analyze the heat transfer of the porous medium. In this paper, we report the validation of JUPITER with the porous model and discuss the effect of various models of the effective thermal conductivity based on the array of the solid inside the porous medium to the natural convective heat transfer. To obtain validation data of JUPITER for the natural convective heat transfer analysis around the porous medium, we performed the heat transfer and the flow visualization experiments of the natural convection in the experimental system including the porous medium. In the comparison between the experiment and the simulations for various models of the effective thermal conductivity, the numerical result with the geometric mean model was the closest of the models to the experimental results.
