Development of air cooling performance evaluation method for fuel debris on retrieval of Fukushima Daiichi NPS by dry method, 3; Heat transfer and flow visualization experiment of free convection adjacent to upward facing horizontal surface

上澤 伸一郎; 柴田 光彦; 山下 晋; 吉田 啓之

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

A dry method for fuel debris retrieval is proposed for decommissioning of TEPCO's Fukushima Daiichi NPS. However, air cooling performance has not yet been strictly evaluated for the fuel debris. We have developed an evaluation method based on a numerical simulation code, JUPITER, to understand the cooling performance. Moreover, a heat transfer and flow visualization experiment in air is also conducted in order to validate the numerical analysis. In this paper, to decide measurement targets of the experiment, we roughly estimated the heat transfer of the fuel debris exposed to the air. The rough estimation indicated that the evaluation of the free convection and the radiation heat transfer were important to understand the heat transfer of the debris. Considering the estimations, a preliminary experiment for the free convection in air adjacent to upward-facing horizontal heat transfer surface was conducted to discuss applicability of the temperature measurement systems and the flow visualization systems to the experiment for the validation of the JUPITER. By the preliminary experiment, we confirmed that heat transfer temperature, air temperature and emissivity can be measured with thermocouples and the infrared camera. The applicability of a PIV to measure velocity fields of the free convection in air was also confirmed.