Acidic organophosphorus separation of americium and curium

Unmet Need: Acidic separation of americium from curium for closing fuel cycle

The separation of americium from curium has been a challenging step for completely closing the nuclear fuel cycle. Both elements are most stable in the trivalent oxidation state in acidic solution. Compounding this issue is their nearly identical ionic radii. The identical charge and nearly identical ionic radii of trivalent americium and curium give rise to very similar chemical behavior in solution which makes separation by solvent extraction difficult. Insoluble bismuthate powder is used to oxidize americium, but is continuously required to maintain the oxidation state and leads to reduced distribution ratio.

The Technology: Utilizing copper periodate oxidant for americium oxidation

This invention utilizes a more soluble copper(III) periodate salt as the Am oxidation and uses acidic cation exchangers to allow extraction at a pH of approximately 2 which increases the residence lifetime of the Cu(III) species and allows for the intrinsic buffering capacity of the periodate ion. With this system Am distribution ratios of ~10 are observed and stable up to at least 70 minutes with no signs of decrease, while separation factors between Am and Cm of more than 1000 have been observed at the radiotracer levels. Separation factors of this magnitude are well beyond that of any currently known solvent extraction based process.

Applications:

• Ease of closing fuel cycle of nuclear energy.

• Nuclear waste and groundwater remediation.

• Separated americium is used in smoke detectors.

Advantages:

• Separation factors greater than 1000 for Am/Cm.

• Low pH and extractant concentration dependence.

• System stable for at least an hour.

• Lower acidity retains oxidant.

• Works at room temperature.

• Works with commercially available chemicals.