AN ALTERNATIVE PROCESS TO IMMOBILIZE INTERMEDIATE WASTES FROM LWR FUEL REPROCESSING

A new concept for converting the intermediate wastes which result from light water reactor (LWR) fuel reprocessing into a single phase material, sodium zirconium phosphate ([NZP]), has been established. This conversion utilizes such waste materials as metals (zirconium alloy, stainless steels, and nickel alloy), spent solvent tri-butyl phosphate (TBP), and concentrated solution of sodium nitrate, and is accomplished using a minimum amount of additional chemicals. The resulting multi-component [NZP] material is homogenous, and has a high mechanical, physical and chemical stability. In addition, the [NZP] can accommodate almost all kinds of fission product cations in the crystalline structure without significant change in its stable lattice structure; as a result, the [NZP] has a high leach resistance appropriate for geological disposal, eliminating the need for additional barrier materials. Taking into account of the equal contribution by boiling water reactors (BWR) and pressurized water reactor (PWR), the amount of immobilized intermediate wastes is predicted to be 1110 kg/MTU (metric ton of uranium before irradiation). After compositional formulation and synthesis of this mineral-like material, X-ray analysis was conducted to ensure single-phase and was followed by processing, microwave-sintering and characterization to demonstrate the fundamental technical feasibility of this concept