The Codecontamination process is based on the co-extraction of U, Pu, and Np from spent fuel dissolved in nitric acid, followed by selective stripping to recover U/Pu/Np in a single product, stream and the remaining U in a second effluent. Codecontamination is based on well-understood solvent extraction chemistry based on the use of tributyl phosphate (TBP) as the extractant. The final process requires predictable control of the behavior of the key species involved in the separations. In terms of flowsheet design, the major factors include controlling the U:TRU ratio in the U/Pu/Np product, directing the majority of the Np to the U/Pu/Np product, minimizing the extraction of fission products (specifically Mo, Ru, and Zr), and controlling Tc behavior. Lab-scale testing is divided into three components: (1) demonstrating that extraction of the key fission products, Ru, Mo and Zr is controlled as predicted by the Argonne Model for Universal Solvent Extraction (AMUSE) code, (2) characterizing the extraction of Np as a function of redox chemistry, and (3) demonstrating the partial stripping of U in the second segment of the process. The first and third components require testing a full multistage flowsheet, while the second component is being studied using microfluidics. Multistage tests were run with a lab-scale 2-cm contactor to validate the design criteria used to develop the flowsheet. Tests of the first and second segment of the Codecontamination flowsheet are described.  A number of small-scale tests using a microfluidic system were run to bracket the stable operating regime for Np. By varying flow rates and capillary lengths, mass transfer and kinetics data could be obtained for Np in the TBP/alkane-nitric acid system.

Lab-scale testing of a codecontamination process

251st National Meeting (2016)

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