Preparation and characterization of simulated fuel debris specific to the Fukushima accident

Takano, Masahide ; Nishi, Tsuyoshi; Onozawa, Atsushi 

Since the severe accident at the Fukushima Daiichi Nuclear Power Plant, we have been studying the characteristics of fuel debris in order to contribute to its removal operation and management. First, a series of reaction experiment on (U,Zr)O with natural sea salt were performed to clarify the chemical influence of sea salt deposit on high-temperature corium. It was found that CaO decomposed from sulphate is most reactive to form (U,Zr,Ca)O solid solution or Ca-U-O uranate on the surface, depending on the oxygen partial pressure. Then, some compacted mixtures of BC, stainless steel, Zr, and (U,Zr)O were arc-melted to investigate the boron-containing compounds in the fuel debris. ZrB and (Fe,Cr,Ni)B were found to precipitate in the alloy part of solidified sample. The phase relationships within these borides and alloy phases can be characterized by the initial B/Zr ratio in the mixture.