Development of numerical simulation method to evaluate heat transfer performance of air around fuel debris, 2; Validation of JUPITER for free convection heat transfer

Uesawa, Shinichiro  ; Yamashita, Susumu   ; Shibata, Mitsuhiko ; Yoshida, Hiroyuki  

A dry method for fuel debris 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 an original numerical simulation code, JUPITER, to understand the cooling performance. Since the JUPITER can simulate melt relocation behavior of a reactor core, we can estimate air cooling performance for debris in consideration of the distribution and the structure of debris. In this paper, the experiment of heat transfer and flow visualization of free convection adjacent to upward-facing horizontal heat transfer surface was conducted to validate the calculation of the turbulent free convection by the JUPITER. The experimental apparatus is composed of a closed test vessel and an upward-facing horizontal heat transfer surface at the bottom of the test vessel. In the comparison between the JUPITER and the experiment, the temperature distribution for the height direction on the steady condition was qualitatively good agreement between the JUPITER and the experiment. The velocity distribution for the height direction near the side wall also was qualitatively good agreement between the JUPITER and the experiment. Therefore, we confirmed that the turbulent free convection calculated by the JUPITER is a qualitatively valid data.