Development of plutonium and americium redistribution model

Sato, Takahiko; Ozawa, Takayuki   

In the MOX fuels irradiated in FBR, the enhanced concentration of plutonium and americium together with fuel restructuring caused by the steep temperature gradient in the radial direction is observed around the central void. The atoms transport caused by thermal diffusion and the pore migration toward the pellet center due to evaporation-condensation is considered as Pu redistribution mechanism. Since the redistribution mechanism for Am is expected to be similar to that for Pu as the results of JOYO irradiation test, assuming that their redistribution would be caused by the similar mechanism, we developed the redistribution model for Pu and Am. The computed radial distribution of Pu and Am concentration was compared with the results of SXMA measurements for MOX fuels, irradiation in Uninstrumented Fuel Irradiation Subassembly Type-B of JOYO. As a result, it was confirmed that the computed radial distribution of Pu and Am would be in good agreement with the observed one.