Dissolution plutonium dioxide

Complete dissolution of plutonium residues, especially high temperature calcined plutonium dioxide contained in residues such as incinerator ash, continues to cause problems, despite continued research since the Manhattan Project (9). Methods to improve the Rocky Flats system include the use of additives (e.g., cerium) and electrochemistry, other solvents (HCl-SnCl2) as well as high-temperature fusion methods (10). High pressure dissolution, HF preleaching, fluorination, and other methods are being investigated. 

The NSD is specifically involved with the assessment of accident risk for the Minatom nuclear power installations and nuclear material transportation. Similar work has been performed for several installations for instance, the dissolution installation at the RT-1 plant and the installation for plutonium dioxide production at the MCIW radiochemical plant. 

Ag(ll) is a strong oxidant which can be used for the treatment of organics in waste and the gasses (NOx, SO2), as well as the dissolution of plutonium dioxide in the nuclear industry. Ag(II) can be generated electrochemically or chemically. The efficiency of the chemical process is low. 

Since the water movement will be very slow compared with the rate at which the wastes dissolve, we are concerned first and foremost with equilibrium solubility. Also, if only to relate behaviour on the geological time scale to that on the laboratory time scale, we will need to know about the mechanisms and kinetics of dissolution and leaching. The waste forms envisaged at present are glass blocks containing separated fission products and residual actinides fused into the glass and, alternatively, the uranium dioxide matrix of the used fuel containing unseparated fission products and plutonium. In the... 

Metal-complexation/SFE using carbon dioxide has been successfully demonstrated for removal of lanthanides, actinides and various other fission products from solids and liquids (8-18), Direct dissolution of recalcitrant uranium oxides using nitric acid and metal-complexing agents in supercritical fluid carbon dioxide has also been reported (79-25). In this paper we explored supercritical fluid extraction of sorbed plutonium and americium from soil using common organophosphorus and beta-diketone complexants. We also qualitatively characterize actinide sorption to various soil fractions via use of sequential chemical extraction techniques. 

As far as reprocessing in the U/Pu fuel cycle is concerned, several chemical separation techniques have been proposed and developed in the past few decades. The most efficient process to date remains the PUREX process (Plutonium and Uranium Recovery by Extraction). This process uses nitric acid HNO3 and organic solvents to dissolve and extract selectively U and Pu, resulting in two separate product streams (U on one side and Pu on the other side of the process chain). As far as reprocessing in the Th/ U fuel cycle is concerned, THOREX (Thorium Oxide Recovery by Extraction) technology must be used, also based on dissolution in nitric acid and solvent extraction (however, with special care for the extraction of Pa, for the separa-tion of U and U, and for the dissolution of thorium dioxide in pure nitric acid). 

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