Development of numerical simulation method to evaluate molten material behaviors in nuclear reactors; Estimation of fuel debris distribution in the pedestal

原子炉内溶融物移行挙動シミュレーション手法の開発; ペデスタル内部の燃料デブリ分布予測

山下 晋   ; 吉田 啓之  

Yamashita, Susumu; Yoshida, Hiroyuki

As for the fuel debris retrieval, precise estimation distribution and characteristic of fuel debris inside the pedestal is quite important. To estimate distribution of fuel debris, since experiments cannot provide sufficient information, numerical simulation will be useful tool. There are some numerical codes for calculating conditions inside a reactor at severe accidents, however, those codes include assumptions and/or scenario related to melt relocation, and cannot simulate relocation process directly. In order to simulate the relocation and corium spreading behavior in PCVs without assumptions and inputted information, a numerical simulation code that can phenomenologically evaluate the melting phenomena is required. Therefore, a phenomenologically-based numerical simulation code for predicting the melting core behavior, including solidification and relocation based on the computational fluid dynamics, JUPITER, has been developed in JAEA. In this paper, we confirm the applicability of JUPITER to the corium spreading process inside a pedestal by simulating corium spreading behaviors and its distributions. As a result, we confirmed that JUPITER has potential to estimate the debris distribution inside the pedestal region.