Phases and morphology in the simulated MCCI products prepared by arc melting method

Takano, Masahide ; Onozawa, Atsushi ; Sudo, Ayako 

To understand the characteristics of MCCI products in Fukushima Daiichi Nuclear Power Station, the simulated MCCI products in laboratory scale were prepared by arc melting of compacted powder mixtures of core materials and concrete. Stainless steel, boron carbide, metallic zirconium, (U,Zr)O, GdO, and platinum group elements were selected as the core materials. Phases, morphology, and micro hardness were analyzed on cross-section of the solidified specimens. The specimens consisted of oxide part (MO corium and silicate glass or Al-Ca-O) and metallic part (alloys and borides). The phase relationships in the MCCI products were found to be dominated by the initial concrete/Zr mixing ratio, because the dehydration of concrete is the main oxidation factor and the metallic zirconium acts as a strong reductant. Micro hardness of main phases are 7 GPa for silicate glass, 13-15 GPa for (U,Zr,Gd,Ca)O corium, and 25 GPa for ZrB and ferrous borides, respectively.