Recovery of Minor Actinides from Spent Fuel via an Extraction Chromatographic Technique Using TPPEN-Immobilized Gels

Abstract

A series of separation experiments was performed in order to study the recovery process for minor actinides (MAs), such as americium (Am) and curium (Cm), from the actual spent fuel by using an extraction chromatographic technique. N,N,N′, N′-tetrakis-(4-propenyloxy-2-pyridylmethyl) ethylenediamine (TPPEN) immobilized chemically in a polymer gel (TPPEN gel), a material developed by the Tokyo Institute of Technology (Tokyo-Tech) (1,2), was used as a new extraction chromatographic agent in this experiment. Mixed oxide (MOX) fuel, which was highly irradiated in the experimental fast reactor Joyo, was used as a reference spent fuel to demonstrate the recovery of the MAs. The MOX fuel, including 29.9 wt% plutonium (Pu), was initially irradiated up to 119 GWd/MTM in the Joyo reactor, and the irradiated fuel was then prepared for the extraction experiment. The irradiated fuel was prepared for extraction experiment as follows: First, uranium (U) and Pu were separated using an ion-exchange method, and then, the platinum group elements were removed by CMPO to leave a mixed solution of MAs and lanthanides (Lns). The TPPEN gel was immersed in a 0.01 M NaNO3 solution, and the pH was adjusted to 4.0. Next, an extraction column was prepared using the TPPEN gel, and the mixed solution of MAs and Lns was passed through the column. The Lns were detected in the eluent after washing with 0.01 M NaNO3 (pH 4.0). For detecting the MAs, the pH of the eluent was changed to 2.0. These results demonstrate that the proposed recovery process for the MAs is a potential candidate for future reprocessing methods based on the extraction chromatographic technique.