Influence of additives on low-temperature hydrothermal synthesis of UO and ThO

UOxとThOの低温水熱合成における添加剤の影響

田端 千紘; 白崎 謙次*; 酒井 宏典   ; 砂賀 彩光*; Li, D.*; 小中 真理子*; 山村 朝雄*

Tabata, Chihiro; Shirasaki, Kenji*; Sakai, Hironori; Sunaga, Ayaki*; Li, D.*; Konaka, Mariko*; Yamamura, Tomoo*

Hydrothermal reactions of uranium(IV) nitrate solutions in the presence of aldehydes yielded microparticles of UO, at temperatures as low as 100C. The synthesized products contained residual organic matter originating from aldehydes used as an additive, unless the synthesis temperature was 390C. Additionally, the residual matter could be separated from the product by heat treatment at 300C. The valence of uranium ions in the UO products was found to be higher than that reported for UO. Low synthesis temperatures resulted in the suppression of the magnetic moments of uranium ions and the occurrence of the spin interaction among the ions. Therefore, the oxidation number of uranium averaged over the entire product could become higher than 4+. A comparative study with ThO suggested that the redox reaction could be closely related to the hydrothermal synthesis reaction and particle growth of UO.