Development of numerical simulation method to evaluate heat transfer performance of air around fuel debris, 1; Effect of the debris shape

燃料デブリの空冷評価解析手法の開発,1; デブリ形状の効果

山下 晋   ; 上澤 伸一郎  ; 吉田 啓之  

Yamashita, Susumu; Uesawa, Shinichiro; Yoshida, Hiroyuki

The fuel debris retrieval method without cooling water is proposed as one candidate for decommissioning of the Fukushima Daiichi NPS, since it can reduce the contaminated water. However, there are unknown information and uncertainties to evaluate the temperature distribution in and around the fuel debris. The temperature distribution is affected by the air-cooling performance, therefore, to solve these issues, we have been developing the analysis method to evaluate the air-cooling performance around accumulated debris in the pedestal. A numerical simulation code JUPITER, which is based on a CFD technique and can treat a multi-phase, multi-component thermal-hydraulics, is applied as the basis of the developed method. In this paper, preliminary numerical simulations to evaluate the effects of debris shapes and heat source conditions on free convection were performed. In these simulations, thermal hydraulic behaviors in simplified pedestal region were calculated by developed method. As a result, it was confirmed that the flow pattern of the free convection in the pedestal clearly differed with debris shapes and the temperature distributions were strongly correlated with the velocity fluctuation around the debris surface.