Skull recycle, casting

Casting Skull Recycle. After ingot casting, a residue containing up to 5% of the plutonium feed remains behind. Usually the metal buttons fed to the casting operations retain some of the calcium used in the reduction operation, as well as other volatile metals and oxides. 

The buttons usually have a film of Pu02 as a result of exposure to glove-box air. Upon casting, this Pu02 floats and remains in the skull along with trapped plutonium metal. This portion of the skull is recycled back into the production sequence. 

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