A new concept for An(III)/Ln(III) separation using TOGDA extractant

International audienceOne of the different options investigated by the CEA Marcoule (in the framework of the EURATOM FP7 collaborative project ACSEPT) to separate trivalent minor actinides (Am(III) to Cf(III)) directly from PUREX raffinates by solvent extraction takes advantage of both (i) the high efficiency of the TODGA diglycolamide to extract trivalent 4f and 5f elements from nitrate/nitric aqueous solutions, and (ii) the selectivity of hydrophilic polyaminocarboxylic acids that complex trivalent 5f elements in buffered conditions better than 4f elements. The extraction system was optimized (both the formulations of the organic solvent and of the aqueous scrubbing and stripping solutions) to meet the requirements of an efficient flowsheet design allowing An(III) recovery yields greater than 99.9%, with high decontamination factors versus Ln(III) in only one SANEX cycle

PALADIN: PALADIN: A one step process for actinides(iii)/ fission products separation

International audienceIn the frame of the French SPIN program, PALADIN is a one partition cycle process able to separate directly americium and curium from lanthanides(III) and other fission products mixed in concentrated nitric acid (similar to a PUREX raffinate). Batch experiments allowed us to choose and optimize every organic and aqueous reagent. Solvent is composed of a mixture of malonamide and alkyphosphoric acid. Aqueous solutions contain only incinerable reagents (hydroxycarboxylic acids, polyaminocarboxylic acids...). An inactive mixer-settlers test was carried out in order to study the behavior of some fission products. Hydrodynamics and performances were good for the main steps of the process, in particular very few fission products were found in actinides(III) aqueous outflow solution

Extractant separation in DIAMEX-SANEX process

International audienceIn the frame of the French radioactive waste management Acts of December 1991 and June 2006, minor actinide separation processes have been developed to significantly decrease the radiotoxicity of the ultimate waste produced by the nuclear industry. For actinide/lanthanide separation, several routes are possible, either with two cycles using two different solvents (generally DIAMEX for the first one, and SANEX for the second one), or with a single cycle and the same solvent during the whole process. The DIAMEX-SANEX concept described in this paper is a sort of intermediate between these two strategies: the organic phase consists of a cationic exchanger and the N,N'-dimethyl-N,N'dioctylhexylethoxymalonamide, (DMDOHEMA), which play different role in distinct key stages of the process. The main idea of this process is to split the organic phase in two solvents: one containing the DMDOHEMA, the other the acidic extractant. So this latter doesn't interact with DMDOHEMA during the first extraction step. This paper describes some results obtained with di-nhexyl phosphoric acid (HDHP), which fulfils the required criteria for the process. For instance, this reagent can easily extract lanthanides from a weak acidic aqueous solution, and it can be stripped selectively from DMDOHEMA, thanks to a basic solution

The separation of extractants implemented in the DIAMEX-SANEX process

Report Number:INIS-FR-08-1324International audienceDIAMEX-SANEX is a process developed at the CEA to recover selectively the actinides(III) after a COEX$^{TM}$ or a PUREX process, in order to significantly decrease the radiotoxicity of the ultimate waste produced by the nuclear industry. This liquid-liquid extraction process is based on the DIAMEX process, using a malonamide supplemented by an acidic extractant. Besides an actinide extraction step and a lanthanide stripping step are implemented an actinide(III) stripping step and an extractant splitting step. The latter is carried out to avoid interactions between these two extractants during the first co-extraction step of the actinides and the lanthanides. This paper gives some results obtained with din -hexyl phosphoric acid (HDHP), which fulfils the required criteria for process development. Batch experiments or cold counter-current tests showed that it is possible to separate this extractant from DMDOHEMA. HDHP can moreover maintain the lanthanides(III) in the organic phase when the actinides(III) are back extracted from the organic phase.

Selective Extraction of Rare Earth Elements from Phosphoric Acid by Ion Exchange Resins

Rare earth elements (REE) are present at low concentrations (hundreds of ppm) in phosphoric acid solutions produced by the leaching of phosphate ores by sulfuric acid. The strongly acidic and complexing nature of this medium, as well as the presence of metallic impurities (including iron and uranium), require the development of a particularly cost effective process for the selective recovery of REE. Compared to the classical but costly solvent extraction, liquid-solid extraction using commercial chelating ion exchange resins could be an interesting alternative. Among the different resins tested in this paper (Tulsion CH-93, Purolite S940, Amberlite IRC-747, Lewatit TP-260, Lewatit VP OC 1026, Monophos, Diphonix,) the aminophosphonic IRC-747, and aminomethylphosphonic TP-260 are the most promising. Both of them present similar performances in terms of maximum sorption capacity estimated to be 1.8 meq/g dry resin and in adsorption kinetics, which appears to be best explained by a moving boundary model controlled by particle diffusion

Trivalent actinides/lanthanides separation using bis-triazinyl-pyridines

International audienceThe separation of trivalent minor actinides from trivalent lanthanides is a difficult task. The present paper describes the application of a Bis-Triazinyl-Pyridine in order to separate americium(III) and curium(III) from various lanthanides(III) present in a synthetic aqueous feed solution simulating a stripping solution issued from the DIAMEX process. The performances observed during the counter-current alpha hot test, carried out at CEA Marcoule using two batteries of eight mixer-settlers, are very promising. They remain, up to now, the best An(III)/Ln(III) separation results ever obtained at such a high acidity ([HNO 3 ] initial = 1 mol/L)

Molybdenum solubility in aluminium nitrate solutions

International audienceFor over 60 years, research reactors (RR or RTR for research testing reactors) have been used as neutron sources for research, radioisotope production ($^{99}$Mo/$^{99m}$Tc), nuclear medicine, materials characterization, etc… Currently, over 240 of these reactors are in operation in 56 countries. They are simpler than power reactors and operate at lower temperature (cooled to below 100°C). The fuel assemblies are typically plates or cylinders of uranium alloy and aluminium (U-Al) coated with pure aluminium. These fuels can be processed in AREVA La Hague plant after batch dissolution in concentrated nitric acid and mixing with UOX fuel streams. The aim of this study is to accurately measure the solubility of molybdenum in nitric acid solution containing high concentrations of aluminium. The higher the molybdenum solubility is, the more flexible reprocessing operations are, especially when the spent fuels contain high amounts of molybdenum. To be most representative of the dissolution process, uranium-molybdenum alloy and molybdenum metal powder were dissolved in solutions of aluminium nitrate at the nominal dissolution temperature. The experiments showed complete dissolution of metallic elements after 30minutes stirring, even if molybdenum metal was added in excess. After an induction period, a slow precipitation of molybdic acid occurs for about 15hours. The data obtained show the molybdenum solubility decreases with increasing aluminium concentration. The solubility law follows an exponential relation around 40g/L of aluminium with a high determination coefficient. Molybdenum solubility is not impacted by the presence of gadolinium, or by an increasing concentration of uranium