SACSESS : the EURATOM FP7 project on actinide separation from spent nuclear fuels

Recycling of actinides by their separation from spent nuclear fuel, followed by transmutation in fast neutron reactors of Generation IV, is considered the most promising strategy for nuclear waste management. Closing the fuel cycle and burning long-lived actinides allows optimizing the use of natural resources and minimizing the long-term hazard of high-level nuclear waste. Moreover, improving the safety and sustainability of nuclear power worldwide. This paper presents the activities striving to meet these challenges, carried out under the Euratom FP7 collaborative project SACSESS (Safety of Actinide Separation Processes). Emphasis is put on the safety issues of fuel reprocessing and waste storage. Two types of actinide separation processes, hydrometallurgical and pyrometallurgical, are considered, as well as related aspects of material studies, process modeling and the radiolytic stability of solvent extraction systems. Education and training of young researchers in nuclear chemistry is of particular importance for further development of this field

Structure and separation quality of various N- and O-donor ligands from quantum-chemical calculations

Although BTP (2,6-di(1,2,4-triazin-3-yl)pyridine) has been proven to be a highly effective N-donor ligand for the selective An(III)/Ln(III) separation, the origin of its selectivity is still under discussion. We present in this paper quantum-chemical calculations at the density functional theory (DFT) and MP2 level which highlight the role of the aquo ions in the separation process. Furthermore these data will be the reference for future force-field development to investigate the differences in An(III) complexation reactions compared to their Ln(III) counterparts

Cs Extraction from Chloride Media by Calixarene Crown-Ethers

Asse II salt mine, in Germany, contains low and intermediate-level radioactive waste that must be retrieved in the upcoming years. Potentially contaminated salts and brines will require treatment, with 137Cs being the main contaminant. Cs+ is problematic to selectively recover due to its chemical similarity with Na+ and K+ which are present in high quantities in a salt mine. This paper offers a novel solution for Cs+ separation from concentrated chloride salt media by solvent extraction with calixarene-crown-ether extractants in an alcoholic diluent. The proposed solvent extracts Cs+ at elevated chloride concentrations (3–4 M) while back-extraction is achieved by contacting the solvent with dilute (0.01 M) hydrochloric acid

Die Legitimation des Briefmonopols zur Finanzierung des Universaldienstes im Briefverkehr

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Stoichiometry of An(III)–DMDOHEMA complexes formed during solvent extraction

N,N’-Dimethyl,N,N’-dioctylhexylethoxymalonamide (DMDOHEMA) is used to separate An(III) and Ln(III) from fission products in several liquid–liquid extraction processes that aim at recycling actinides. The stoichiometry of the extracted complexes is important for a complete understanding of the processes. The presented work focuses on the complexation of Cm(III) with DMDOHEMA studied by TRLFS in mono- and biphasic (solvent extraction) systems. The formation of [Cm(DMDOHEMA)n]3+ (n = 1–3) in 1-octanol containing 1.7 mol L−1 of water with log β’1 = 2.6 ± 0.3, log β’2 = 4.0 ± 0.5, log β’3 = 4.3 ± 0.5 was confirmed. In addition, fluorescence lifetime measurements indicated the formation of a 1 : 4 complex. Furthermore, solvent extraction experiments were performed, varying the proton and nitrate concentrations. TRLFS measurements of organic phases confirmed the existence of two species, [Cm(DMDOHEMA)3(NO3) (H2O)1–2]2+ (dominant at high proton and nitrate concentrations) and [Cm(DMDOHEMA)4(H2O)]3+ (dominant at low proton and nitrate concentrations). To support the proposed stoichiometries, vibronic sideband spectroscopy (VSBS) was employed, allowing the observation of vibrations of functional groups coordinated to the probed metal ion. Clear differences between the vibronic side bands of the 1 : 3 and 1 : 4 complex in the range of 900–1300 cm−1 were observed. Vibrational spectra calculated by DFT complimented the experimental data and confirmed the proposed stoichiometries. They revealed a monodentate coordination mode of the nitrate and two water molecules in the 1 : 3 complex

Modelling of Innovative SANEX Process Maloperations

The innovative (i-) SANEX process for the separation of minor actinides from PUREX highly active raffinate is expected to employ a solvent phase comprising 0.2M TODGA with 5 v/v% 1-octanol in an inert diluent. An initial extract / scrub section would be used to extract trivalent actinides and lanthanides from the feed whilst leaving other fission products in the aqueous phase, before the loaded solvent is contacted with a low acidity aqueous phase containing a sulphonated bis-triazinyl pyridine ligand (BTP) to effect a selective strip of the actinides, so yielding separate actinide (An) and lanthanide (Ln) product streams. This process has been demonstrated in lab scale trials at Jülich (FZJ). The SACSESS (Safety of ACtinide SEparation proceSSes) project is focused on the evaluation and improvement of the safety of such future systems. A key element of this is the development of an understanding of the response of a process to maloperations. It is only practical to study a small subset of possible maloperations experimentally and consideration of the majority of maloperations entails the use of a validated dynamic model of the process. Distribution algorithms for HNO3, Am, Cm and the lanthanides have been developed and incorporated into a dynamic flowsheet model that has, so far, been configured to correspond to the extract-scrub section of the i-SANEX flowsheet trial undertaken at FZJ in 20131. Comparison is made between the steady state model results and experimental results. Results from modelling of low acidity and high temperature maloperations are presented