ULTRASOUND EFFECTS ON THE DISSOLUTION OF REFRACTORY OXIDES (CEO2 AND PUO2) IN NITRIC-ACID

Refractory oxides such as CeO2 and PuO2 are very difficult to be disso lved. They often involve the use of powerful reagents which further ma nagement is difficult (especially for nuclear waste). Concerning PuO2 used in nuclear fuels manufacturing, new dissolution techniques has be en studied using ultrasound effects (20, 500 and 700 kHz) on powder ox ides dipped into the nitric acid solutions. The experiment was tested to produce free radicals generated by cavitation (bubble implosion) to obtain either the oxidative or reducing conditions required for PuO2 dissolution. The formation of submicronic particles easier to solubili ze was investigated. To enhance the dissolution mechanism and the prod uction of free radicals, various scavengers (organic acids or alcohols ) and solubilized gases were tested. The mechanical and chemical effec ts on oxide dissolution behavior were analyzed.