Synthesis of zirconolite with U-Ce mixed oxide for stable storage of nuclear fuel materials

林崎 康平 ; 廣岡 瞬 ; 秋山 大輔*; 桐島 陽*; 齋藤 浩介

Hayashizaki, Kohei; Hirooka, Shun; Akiyama, Daisuke*; Kirishima, Akira*; Saito, Kosuke

Zirconolite (CaZrTiO, x=0.8-1.3) is expected ceramic with its high chemical stability, radiation tolerance, and ability to contain Pu as solid solution in its crystal structure. Fabrication process of zirconolite using PuO as a raw powder have been studied, while there are no studies on that using (U,Pu)O (MOX) as a raw powder. In this study, (U,Ce)O as a MOX simulant, CaO, ZrO and TiO were used as raw powder and (U,Ce)-doped zirconolite was synthesized by pressing and sintering mixtures of the raw powder. The effect of three types of sintering atmospheres; air, Ar, and Ar-H on the synthesis of zirconolite was investigated. In an air atmosphere, (U,Ce)-doped zirconolite was obtained with almost 100% yield. In an Ar and 10%H-Ar atmosphere, perovskite (nominally expressed as CaTiO), which has lower chemical stability compared with zirconolite in SATP, were obtained in 13% and 23% yield, respectively. XRD and EDX analyses revealed that the perovskite phase was formed by partial substitution of reduced cerium cations (Ce) at Ca sites. The results were attributed to the fact that more Ce was reduced in the 10%H-Ar atmosphere than Ar.