Pascal Baron

Recovery of Minor Actinides from HLLW Using the DIAMEX Process.

Summary In this work a hot demonstration of the DIAMEX process using the new reference molecule DMDOHEMA (N,N′-DiMethyl-N,N′-DiOctylHexylEthoxyMalonAmide) and genuine high-level PUREX raffinate as feed is reported. The continuous counter-current experiment was carried out in a 16-stage centrifugal extractor battery, installed in a hot cell. In order to produce a representative High Level Liquid Waste (HLLW) a PUREX process was applied on dissolved fuel using the same equipment. It was demonstrated that 5 extraction stages were sufficient to achieve feed decontamination factors above 2200 and 320 for Am and Cm, respectively. Co-extraction of molybdenum and zirconium, as well as of palladium, were efficiently prevented using oxalic acid and HEDTA scrubbing, respectively. However, technetium, yttrium, and to some extent ruthenium, were co-extracted. The back-extraction proved to be very efficient, yielding in 4 stages more than 99.9% recovery of Am and Cm. The extraction profiles were modeled with computer code simulations and the results compared with data obtained from an experiment using the former reference molecule DMDBTDMA (DiMethylDiButylTetraDecylMalonAmide).

DIAMEX Counter‐Current Extraction Process for Recovery of Trivalent Actinides from Simulated High Active Concentrate

Abstract The partitioning of trivalent actinides was demonstrated with a new version of the French DIAMEX (DIAMide EXtraction) process. A continuous counter‐current experiment using a 16‐stage centrifugal extractor battery was tested using 1 mol/L N,N′-dimethyl‐N,N′-dioctyl‐hexylethoxy‐malonamide (DMDOHEMA) in TPH as the extractant. A high active concentrate (HAC), obtained after concentration and denitration of a high active raffinate (HAR) with a concentration factor of 10, was used as a feed. Based on results from cold and hot batch extraction experiments and computer code calculations, a flowsheet was developed and a full test was carried out using a simulated HAC solution spiked with radionuclides (241Am, 244Cm, 152Eu, and 134Cs). In the DIAMEX process, five extraction stages were sufficient to obtain Am and Cm (feed/raffinate) greater than 5000 and for the coextracted lanthanides decontamination factors between 1100 and 4500. Co‐extraction of zirconium, molybdenum, and palladium was prevented by using oxalic acid and HEDTA. The back extraction comprising 4 stages was also efficient and the recoveries of actinides were greater than 99.8%, which can be further improved by a minor process flowsheet optimisation. The experimental steady‐state concentration profiles of important solutes were determined and compared with model calculations and good agreement was generally obtained.

Transient -and Steady-State Concentration Profiles in a DIAMEX-like Countercurrent Process for An(III) + Ln(III) Separation

A new version of the DIAMEX (DIAMide EXtraction) process is reported to separate trivalent Am,Cm (An) and lanthanides (Ln) from a PUREX (Plutonium Uranium Refining by EXtraction by tributyl phosphate) process raffinate at a high aqueous/extractant flow-rate ratio while taking care of prevent third-phase formation. The process has been modeled by a computer program and tested on a 16-stage mixer/settler battery to perform extraction, scrubbing, and stripping to obtain an Am (representing the mixture of Am + Cm) decontamination factor (feed/raffinate) higher than 103 and a Mo + Zr fission product content in the product lower than 1 wt% of that of Am. Transient and steady-state concentration profiles of the solutes have been calculated and experimentally determined, and good agreement was generally observed.