Washing of uranyl nitrate hexahydrate crystals with nitric acid aqueous solution to improve crystal quality

結晶品質向上に向けた硝酸水溶液による硝酸ウラニル六水和物結晶の洗浄

中原 将海; 中島 靖雄  ; 小泉 務

Nakahara, Masaumi; Nakajima, Yasuo; Koizumi, Tsutomu

Ceを含んだ硝酸ウラニル溶液を用いた洗浄試験では、母液に留まるCeは硝酸ウラニル六水和物結晶の表面に付着し、低HNO濃度の洗浄液による洗浄操作により除去できる傾向を示した。照射済高速炉燃料溶解液を用いた晶析試験では、液体不純物の除染係数は結晶洗浄操作により向上した。一方、固体不純物の除染係数は、数回の洗浄操作に伴い減少した。これは、硝酸ウラニル六水和物結晶が固体不純物よりもHNO溶液に溶けやすいことに起因するものと思われる。

In the crystal washing experiment using the uranyl nitrate solution containing Ce, the Ce in the mother liquor was attached to the surface of the uranyl nitrate hexahydrate crystals and tend to be removed by the washing operation with low HNO concentration washing solution. In the crystallization experiments using the dissolver solution of irradiated fast reactor core fuel, the decontamination factors of liquid impurities were improved by crystal washing. On the other hand, the decontamination factors of solid impurities decreased with several washings because uranyl nitrate hexahydrate is more soluble than the solid impurities in an HNO solution.