Physicochemical properties of dicesium tetravalent plutonium hexanitrate in uranium crystallization process

Tetravalent Pu reacts with Cs ions to form the crystalline precipitate of Cs2Pu(NO3)6under certain chemical conditions during the U crystallization process. The Cs2Pu(NO3)6precipitate reduces the decontamination factor (DF) of Cs to U in the crystal after being washed. The solubility and thermal properties of Cs2Pu(NO3)6 were studied with the aim of providing a characterization estimate. The solubility of Cs2Pu(NO3)6 increased with decreases in HNO3 concentration. Loss in weight of the compound caused by thermal degradation of Cs2Pu(NO3)6 to Cs2PuO2(NO3)4 was observed at 245 deg. C in thermal analysis. A uranyl nitrate hexahydrate (UNH) crystal was obtained by cooling irradiated fast reactor core fuel dissolver solution. The DF of Cs decreased with increasing the HNO3 concentration of the mother liquor because more Cs2Pu(NO3)6 precipitates with high concentration of HNO3.