Development program to recycle and purify plutonium-238 oxide fuel from scrap

Nuclear Materials Technology (NMT) Division has initiated a development program to recover and purify plutonium-238 oxide from impure sources. A glove box line has been designed and a process flowsheet developed to perform this task on a large scale. The initial effort has focused on purification of {sup 238}PuO{sub 2} fuel that fails to meet General Purpose Heat Source (GPHS) specifications because of impurities. The notable non-actinide impurities were silicon and phosphorus, but aluminum, chromium, iron and nickel were also near or in excess of limits specified by GPHS fuel powder specifications. Among actinide impurities, uranium is of paramount concern because {sup 234}U is the daughter of {sup 2238}Pu by alpha decay, and is the largest actinide impurity. An aqueous method based on nitric acid was selected for purification of the {sup 238}PuO{sub 2} fuel. All aqueous processing used high purity reagents, and was performed in PTFE apparatus to minimize introduction of new contaminants. Impure {sup 238}PuO{sub 2} was first dissolved in refluxing HNO{sub 3}/HF and then the solution was filtered. The dissolved {sup 238}Pu was adjusted to the trivalent state by an excess of reducing reagents to compensate for radiolytic effects, precipitated as plutonium(III) oxalate, and recovered by filtration. The plutonium(III) oxalate was subsequently calcined to convert the plutonium to the oxide. Decontamination factors for silicon, phosphorus and uranium were excellent. Decontamination factors for aluminum, chromium, iron and nickel were very good. The purity of the {sup 238}PuO{sub 2} recovered from this operation was significantly better than specifications. Efforts continue to develop the capability for efficient, safe, cost-effective, and environmentally acceptable methods to recover and purify {sup 238}PuO{sub 2} fuel in a glovebox environment. Plutonium-238 materials targeted for recovery includes impure oxide and scrap items that are lean in {sup 238}Pu values