Decontamination of liquid radioactive wastes by fixation on inorganic exchangers

An attractive method for the decontamination of large volumes of radioactive liquid is fixation on inorganic exchangers. This process can concentrate the activity into a small volume of solid waste which may be either transformed into a stable solid or incorporated into a solid matrix. The fixators are radiation resistant; most of them do not suffer chemical degradation in a large scale of pH. They can exhibit a high selectivity for certain ions. Inorganic fixators, especially insoluble ferrocyanides, seem to be promising for cesium decontamination. Polyantimonic acid is known for its good efficiency towards the fixation of strontium, but with a slow kinetics. We have studied two types of products: insoluble ferrocyanides and antimonic or phosphatoantimonic acids. Owing to the support of our anterior studies and the proposal of a new preparation process which controls the particle size and produces ferrocyanides suitable for use on columns, this work was devoted to the determination of the optimal recovery conditions of radioactive cesium and silver on several types of nickel and zinc ferrocyanides. The other purpose of our study was a comparison between antimonic acid and some new phosphatoantimonic acids in order to select the most efficient compound for the fixation of strontium. The fixation of lanthanum was also studied as a model for transuranic elements