“The Third Phase” of Extraction Processes in Fuel Reprocessing, (III)

Abstract

The coordination and complexation behavior of Zr-dibutylphosphate was investigated by ³¹P-NMR measurement, in order to clarify the mechanism of the previously reported phenomena that the precipitates once formed at low HDBP/Zr mole ratio of 2 in an organic solution disappears with increasing HDBP/Zr. As the results of ³¹P-NMR spectrum measurements, following two steps were identified. (1) Species having Zr:DBP=1:3 immediately reacts with free HDBP to form species having Zr : DBP=1:4 with increasing HDBP/Zr, (2) Under the presence of higher HDBP/Zr concentration, species having more DBPs than 4 to one Zr are observed. DBP⁻ (or HDBP) ligands in these species bridge two Zr ions to form three-dimensional net-work structure and have an interaction with HDBP in the solvent. Consequently, the mechanism was elucidated for the re-dissolution of Zr-DBP precipitates with sufficient free HDBP producing highly viscous oilyliquid.

KEYWORDS:

• third phase
• solvent extraction
• fuel reprocessing
• phosphorus 31
• nuclear magnetic resonance
• redissolution
• DEP
• THP
• precipitates
• concentration dependence
• zirconium complexes