[en] Among the different bis-triazinyl-pyridine molecules studied at CEA-Marcoule, the 2,6-bis(5,6-n-propyl-1,2,4-triazine-3-yl)-pyridine (nPr-BTP) was chosen to carry out a counter-current SANEX^a test, the feed solution of which was a genuine back-extraction solution issued from a DIAMEX process. Although the observed performances were very satisfactory for the separation of actinides(III) from lanthanides(III), the extraction and back-extraction yields of americium and curium were lower than expected from calculation. The hot test actually pointed out the strong sensitivity of nPr-BTP towards air oxidation and acidic hydrolysis. Further investigations will thus be devoted to the strengthening of the molecule towards hydrolysis and hopefully lead to the formulation of a new solvent, which would be tested during year 2001 in the Atalante facility. (authors)

[en] In 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 alkyl-phosphoric acid. Aqueous solutions contain only incinerable reagents (hydroxycarboxylic acids, poly-aminocarboxylic 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

[en] The CEA has undertaken the development of the DIAMEX process as the first step in the strategy aiming at recovering minor actinides which could then be transmuted or separately conditioned. The scientific feasibility of this process was demonstrated during counter current hot tests operated in 1993. Then experimental works were conducted, on one hand to optimise the extractant formula, on the other hand to improve the flowsheet. Reference extractant and flowsheet were then chosen, respectively in 1995 and 1996. The next step, still in progress, is the demonstration of the DIAMEX technical feasibility (in 2002); this means that the flowsheet should include solvent regeneration treatments. In this aim, degradation studies were performed to quantify main degradation products, and identify those which could be disturbing in the process. This paper deals with experimental studies performed with intend to propose a regeneration treatment, included in the flowsheet, so that the solvent could be recycled. It comprises: - Quantification of the main degradation products issued from radiolysis or hydrolysis, which are methyl octyl amine (MOA) and carboxylic acids; - Effects of these products on extracting and hydrodynamics performances of the process; - Study of methods able to remove mainly disturbing degradation products. Acidic scrubbing, which are performed in the scrubbing and stripping sections of the DIAMEX process, should allow the quantitative removal of methyl octyl amine. Then basic scrubbings, which were more especially studied, should eliminate at least 80% of carboxylic acids, and part of the cations remaining in the solvent. (authors)