Relationship between melting points and crystal structures of uranyl nitrate complexes bearing cyclic urea precipitants

Suzuki, Tomoya; Takao, Koichiro*; Kawasaki, Takeshi*; Sasaki, Yuji  ; Harada, Masayuki*; Nogami, Masanobu*; Ikeda, Yasuhisa*

An advanced reprocessing system for spent FBR fuels has been proposed on the basis of selective precipitation ability of pyrrolidone or cyclic urea derivatives. In this process, U and Pu are recovered through two precipitation process after dissolution of spent FBR fuels in HNO solution. In our previous study, it was found that hydrophilic compounds which can form uranyl nitrate complexes with high melting points have high selective precipitation ability to U(VI). In this study, molecular and crystal structures of uranyl nitrate complexes bearing cyclic urea ligands were examined to clarify requirements for forming the U(VI) complexes with high melting points.