Study on a nuclear fuel reprocessing system based on the precipitation method in mild aqueous solutions

A new reprocessing system for spent nuclear fuels based on a precipitation method is proposed to recover uranium and transuranium elements from spent nuclear fuels in high ratios and to achieve extreme safety without any potential dangers. Experiments were carried out for a simulated fuel solution containing uranium and 17 major elements. The main reprocessing processes are as follows: (a) dissolution of UO₂ fuel under mild conditions; (b) neutralization of the dissolved fuel solution with Na₂CO₃-NaHCO₃ mixed solutions, followed by the separation of precipitated fission products by centrifugation; (c) separation of cesium by a precipitation method using a tetraphenylborate ion; and (d) recovery of uranium (U) as a precipitate of the hydrolyzed compound from an alkaline solution. As a result, 99.95% of the U was recovered with the least amount of fission products, i.e., 10^-5 g or even less in the recovered 1 g of U with the only exceptions being zirconium and molybdenum.