Electrochemical treatment of non-compact able materials contaminated with uranium compounds

Decontamination of non-compact able radioactive wastes, such as tools and equipment, aims to remove surface radioactive waste from the waste, in order to reduce the volume of waste to be conditioned and stored. The application of electrochemical techniques such as electrocoagulation (Ec) and advanced oxidation processes (Aop) in the decontamination of waste or non-compact able radioactive materials stainless steel containing uranium were studied in this work, in order to assess their technical feasibility. For the aforementioned, tests with stainless steel plates coated with WO₃ (anode function) were made for the Ec. These plates were coated with the objective of simulating a fixed contamination in their surface and to be able to determine the best conditions of removal of Tungsten by Ec as ph, electrolyte support, distance between the electrodes, cell potential and type of counter-electrode material. In the case of Ec, the mechanism that occurs is an electro dis-solving of the iron plate, with oxygen detachment at the anode and the detachment of the WO₃ layer, passing all to the solution, with the formation of iron hydroxides. For the Aop was evaluated the wear steel in presence of WO₃ using IrO₂-Ta₂O₅/Ti electrodes and boron doped diamond (Bdd), determining the best electrochemical conditions for the highest production of radicals ·OH in less time. In the case of Poa, the generation of hydroxyl radicals occurs in the modified electrode (anode) while in the plate coated with WO₃ (cathode function) H2 evolution occurs in the form of bubbles which contributes to the separation of the layer of WO₃ at the surface of the electrode and once in solution the little of organic that is had like ligand in WO₃ is oxidized by the action of the hydroxyl radicals. From the best experimental conditions to remove WO₃ by Ec and Poa, they were applied in the decontamination of stainless steel plates contaminated with UO₂(NO₃)₂, and the viability of the decontamination process by Ec and Aop was evaluated. Uranium removal efficiencies of 90% were obtained in a time of 1 h at ph 1 using 2,4 V and having a distance between anode/cathode electrodes of 1 cm for Ec and Aop process. Finally, after trying both electrochemical techniques (Ec and Aop) in the laboratory, radioactive decontamination of items contaminated with real U-238 under the conditions and previously studied parameters were determinate. (author)