Although solvent extraction is a very efficient process used to separate plutonium from neptunium and fission products, it does not yield the levels of purity required for the plutonium product to be used in Radioisotope Thermoelectric Generators (RTGs) and for recycling neptunium. Ion exchange has become an indispensable method to purify neptunium and plutonium as part of the plutonium-238 production program at Oak Ridge National Laboratory. Fission products are removed by solvent extraction, follow-on separations are accomplished using ion exchange. The multiple oxidation states of neptunium have specific redox properties yielding different affinities to the anion exchange resin. Thus, very clean plutonium and neptunium products can be obtained during the elution of the column. Further purification is achieved using a cation exchange resin. The resin is used to immobilize the plutonium before calcination. This step also lets any neptunium go through the column. Plutonium obtained during the third plutonium-238 production campaign at Oak Ridge National Laboratory met all the product specifications given by Los Alamos National Laboratory. In addition, very clean neptunium containing less than 10 ppm of plutonium-238 was recently produced to make targets for test irradiations in the Advanced Test Reactor at Idaho National Laboratory.

Cation exchange applications for processing plutonium-238

2019 Spring National Meeting

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