New approach to the nuclear fuel reprocessing in non-acidic aqueous solutions

A new nuclear fuel reprocessing method based on the anodic dissolution of spent fuels in aqueous alkaline solutions (Na2CO3-NaHCO3) has been proposed. Experiments of the anodic dissolution were performed by using a simulated spent fuel in a Na2CO3-NaHCO3 solution. Uranyl ions produced anodically were present in the solution as stable carbonato complexes, and at the same time, most of the simulated fission products (FP) were precipitated as hydroxo or carbonate compounds. Under this condition, Cs of an alkali metal group was dissolved in the solution and precipitated by adding sodium tetraphenylborate. Uranyl ion was recovered as hydroxo compounds by adding NaOH to the solution after removing precipitates of the simulated FP. In view of waste disposal, Tc-99 having a long half-life should be removed. Precipitation behavior of Tc(VII) was examined by using Re(VII) as a simulant of Tc(VII). It was found that Re(VII) species are completely removed as a precipitate by adding tetraphenylphosphonium chloride. A large amount of Na used in the present method was recovered as NaHCO3 by blowing CO2 into alkaline solutions. As a result, it was clarified that the proposed method is fundamentally possible as a new reprocessing method.