Fundamental considerations on melting simulations of fuel assemblies in nuclear reactors

Yamashita, Susumu   ; Yoshida, Hiroyuki  ; Takase, Kazuyuki

In the Fukushima accidents, fuel bundle reached a high temperature caused by falling off the function of the cooling effect by loss of coolant located in the reactor. As a results, a melting occurred in arbitrary fuel bundle and it spread to whole fuel bundle, then, it is inferred that the reactor core was fall. In order to elucidate the development of such melting phenomena, we need numerical simulation code which can be circumstantially estimated melting phenomena. We carried out fundamental investigations for the numerical analysis method to which estimate influences of melting of a fuel canning material and a solidification of a molten material for fuel rods placed in the fuel bundle. As a result, we confirm that the a series of physical properties, melting by heat fluxes on the fuel rod and solidifications in the bottom of the under side of the numerical domain were numerically simulated.