Plutonium processing pelletized

In their manufacture uranium(IV) oxide is mixed with the appropriate quantity of plutonium(IV) oxide, the mixture pressed into pellets and then sintered (termed coprocessing in the USA). Uranium(IV) oxide is produced by one of the above-described processes and plutonium(IV) oxide from the aqueous nitrate solution produced during reprocessing by precipitating it as plutonium oxalate and calcining the oxalate. 

The extended radiation time for the domestic fuel increases the quantity of fission products and the higher actinides. Pure plutonium product poses nuclear weapons proliferation risk and is the primary reason reprocessing is not practiced in the United States. The modified PUREX process has been practiced on an industrial scale in Europe and supports the production of mixed uranium-plutonium fuel. Blended UO2 and PUO2 powder is compacted and sinter to form the mixed oxide (MOX) fuel pellets much like the enriched UO2 fuel. Natural and depleted uranium can be used to prepare MOX fuel and is the demonstrated option to recover fuel values from spent fuel. 

The process developed by Belgonucleaire (Fig. 1) is called MIMAS for MIcronized MASter blend. The MIMAS MOX pellets are composed of a solid solution of UO2 and PUO2 homogeneously dispersed in a UO2 matrix. This result is achieved through two blending steps (1) the primary (or master) blend is obtained by ballmilling and (2) the secondary (or final) blend is used to produce the specified plutonium content in the pellets. 

Recently, we have modified our production equipment for a better mechanization of all mass storage and we have developed new process equipment for visual inspection of the pellets and for opening the plutonium cans. 

The main process of plutonium immobilization in the United States is the mixing of plutonium oxide with ceramic precursors to form ceramic pellets. These pellets will potentially immobilize the plutonium for hundreds of millions of years. The ceramic processing consists of five basic steps depicted in Figure 2. 

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