Research on the stability of fuel debris consisting of oxides and alloys, 13; Leaching behavior of FPs from the simulated debris

Sasaki, Takayuki*; Tonna, Ryutaro*; Kobayashi, Taishi*; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Watanabe, Masayuki   ; Kumagai, Yuta   ; Kusaka, Ryoji  

Fuel debris containing alloy phases is expected to be formed in the Fukushima Daiichi Nuclear Power Plant. In this study, two series of simulated debris samples comprising uranium-zirconium-stainless steel were synthesized. One series of the samples was prepared by the irradiation method, where the samples were irradiated by thermal neutron for fission generation. The other was prepared by the doping method, where stable isotopes of FPs were added during the synthesis. We performed leaching tests as an aging treatment, and then measured structural changes in the samples and the elution rates of U and FPs contained in the samples. Moreover, in order to evaluate the colloid formation of these elements, particle size distribution was analyzed by an ICP-MS method combined with filtration using different pore-size filters or size exclusion chromatography. Based on the results, the chemical stability of the simulated debris and the speciation of the eluted nuclides were discussed.