Development of technology for reduction of actinide radiotoxicity

The purpose of this research project was to develop a technology of recovery of U, which occupies most of the volume in the spent fuel, from spent nuclear fuel with concepts of highly-enhanced proliferation-resistance and more environmental friendliness, which would be help in helpful for the spent fuel management in views of a volume reduction of the high level active waste and recycle of uranium. A technology with characteristics of U being dissolved alone from the spent the fuel in a carbonate system, while the TRU oxides and most of the fission products remain undissolved, and all the carbonate used in the system being recycled in a salt-free way was suggested. Four unit research items to accomplish it such as 1. a technique for a selective oxidative dissolution-leaching of uranium, 2. a technique for a high purity precipitation of uranium, 3. a technique for removal of environmentally-detrimental elements, and 4. a technique for a salt-free electrolytic recovery of used carbonate salt were carried out. The obtained results were as follows. - Evaluation of chemical characteristics and verification of insolubility properties of TRU oxides in carbonate media - Evaluation of aquatic chemical and dissolution characteristics of rare earth and transition elements in carbonate media - Measurements of the dissolution rates of U oxide and SIMFUEL and their solubilities in carbonate media - Evaluation of co-precipitation of environmentally-detrimental elements - Development of an electrolytic recycle way of used carbonate salt solution - Suggestion of a new conceptual process, named COL process