RESUMEN
Solvent extraction of Eu3+ and Am3+ via N,N,N',N'-tetraoctyl diglycolamide (TODGA) dissolved in different molecular diluents was studied. The diluent types used in this work were primary and secondary alcohols, secondary ketones and alkanes. Effects of concentration of extracting agent, temperature, diluent type and its carbon chain length on the extractions were determined. Distribution ratios of Eu3+ and Am3+ showed high dependence on the diluent type as well as the carbon chain length within the same type of diluent. The highest distribution ratios for both Eu3+ and Am3+ as well as the separation factors of Eu3+ over Am3+ were observed in the alkane diluents. Unexpectedly high distribution ratios for Eu3+ and Am3+ were observed in polar diluents with 5 carbon atoms in the chain, clearly standing out against the general trends. It was found that Eu3+ and Am3+ extraction via TODGA is enthalpy driven in all the studied diluents and that extraction is more exothermic in alkane diluents. Analysis of the stoichiometry of the extracted complexes shows that the average ligand number of TODGA molecules in the extracted complex is lower for Am3+ compared to Eu3+ except for with alkane diluents.
RESUMEN
The two organic ligands 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)[2,2']bipyridine (CyMe 4 -BTBP) and tri-butyl phosphate (TBP) have previously been investigated in different diluents for use within recycling of used nuclear fuel through solvent extraction. The thermodynamic parameters, KS , ΔCp , ΔH0 and ΔS0 , of the CyMe 4 -BTBP solubility in three diluents (cyclohexanone, octanol and phenyl trifluoromethyl sulfone) mixed with TBP have been studied at 288, 298 and 308 K, both as pristine solutions and pre-equilibrated with 4 mol · L -1 nitric acid. In addition, the amount of acid in the organic phase and density change after pre-equilibration have been measured. The solubility of CyMe 4 -BTBP increases with an increased temperature in all systems, especially after acid pre-equilibration. This increased CyMe 4 -BTBP solubility after pre-equilibration could be explained by acid dissolution into the solvent. Comparing the ΔH0 and ΔS0 calculated using ΔCp with the same parameters derived from a linear fit indicates temperature independence of all three thermodynamic systems. The change in enthalpy is positive in all solutions.
RESUMEN
Ruthenium is a fission product that can be released from the fuel in case of a severe nuclear accident. In this work the impact of the atmosphere composition, including air radiolysis products, on the transport of ruthenium through a primary circuit was examined. Experiments were performed at temperatures 1300, 1500 and 1700 K in a slightly humid air. In the experiments significant effect of nitrogen oxides (N2O, NO2) and nitric acid on the ruthenium chemistry in the model primary circuit was observed. The obtained results indicate a strong effect of air radiolysis products on the quantity partitioning of transported ruthenium to gaseous and aerosol compounds.