[en] In the framework of the successive 1991 and 2006 Waste Management Act, French government supported a very significant R and D program on partitioning and transmutation of minor actinides (MA). This program aims to study potential solutions for still minimizing the quantity and the hazardousness of final waste, by MA recycling. Indeed, MA recycling can reduce the heat load and the half-life of most of the waste to be buried to a couple of hundred years, overcoming the concerns of the public related to the long-life of the waste. Within this framework, this paper aims to present the most recent progress obtained in CEA on the development of innovative actinide partitioning hydrometallurgical processes in support of their recycling, either in an homogeneous mode (MA are recycled at low concentration in all the standard reactor fuel) or in an heterogeneous mode (MA are recycled at higher concentration in specific targets, at the periphery of the reactor core). Recovery performances obtained on recent tests in high active conditions of the so-called GANEX and DIAMEX-SANEX process will be presented and discussed in light of the potential P and T scenarios. Finally, recent developments regarding the recycling of the sole Am will be presented as well as the results obtained on highly active solutions for this so-called EXAM process. This set of results gives to the French government a portfolio of potential recycling processes which could be separately and progressively implemented if decided. (authors)

[en] Recycling americium (Am) alone from spent nuclear fuels is an important option studied for the future nuclear cycle (Generation IV systems) since Am belongs to the main contributors of the long-term radiotoxicity and heat power of final waste. Since 2008, a liquid-liquid extraction process called EXAm has been developed by the CEA to allow the recovery of Am alone from a PUREX raffinate (a dissolution solution already cleared from U, Np and Pu). A mixture of DMDOHEMA (N,N'-dimethyl-N,N'-dioctyl-2-(2-(hexyloxy)ethyl)-malonamide) and HDEHP (di-2-ethylhexylphosphoric acid) in TPH is used as the solvent and the Am/Cm selectivity is improved using TEDGA (N,N,N',N'-tetraethyl-diglycolamide) as a selective complexing agent to maintain Cm and heavier lanthanides in the acidic aqueous phase (5 M HNO_3). Americium is then stripped selectively from light lanthanides at low acidity (pH=3) with a poly-aminocarboxylic acid. The feasibility of sole Am recovery was already demonstrated during hot tests in ATALANTE facility and the EXAm process was adapted to a concentrated raffinate to optimize the process compactness. The speciation of TEDGA complexes formed in the aqueous phase with Am, Cm and lanthanides was studied to better understand and model the behavior of TEDGA in the process. Some Ln-TEDGA species are extracted into the organic phase and this specific chemistry might play a role in the Am/Cm selectivity improvement. Hence the hydrophilicity-lipophilicity balance of the complexing agent is an important parameter. In this comprehensive study, new analogues of TEDGA were synthesized and tested in the EXAm process conditions to understand the relationship between their structure and selectivity. New derivatives of TEDGA with different N-alkyl chain lengths and ramifications were synthesized. The impact of lipophilicity on ligand partitioning and Am/Cm selectivity was investigated. (authors)

[en] We have conducted a long-term environmental assessment of a geological repository for Intermediate Level Wastes (ILW) arising from PyroGreen processes that has been developed to decontaminate all HLW from the pyrochemical partitioning of spent nuclear fuels (SNF). PyroGreen process has been designed so that final ILW can meet conservative acceptance criteria such as one established for the Waste Isolation Pilot Plant (WIPP) in U.S.A. The nuclide inventory of final vitrified PyroGreen waste is calculated using ORIGEN 2.1 based on the design decontamination factor of PyroGreen processes applied to 18,171 metric tons of PWR SNF with 45 GWD/MTU burnup. Using GoldSim model, the environmental impact of ILW upon geological disposal at an intermediate depth. Among radioactive nuclides, Ra"2"2"6, Rn"2"2"2 and Sn"1"2"6 are identified as key contributors to radiological dose for general public. The environmental impact of PyroGreen wastes satisfies the Korean dose limit of 0.1 mSv/year with sufficiently high margin. Sensitivity studies have shown that the predicted dose can vary significantly by distribution coefficient of Ra"2"2"6 and Rn"2"2"2, solubility limit of Se"7"9. (authors)

[en] The use of laser radiation with tunable wavelength allows the selective excitation of actinide/lanthanide species with subsequent registration of luminescence/chemiluminescence for their detection. This work is devoted to applications of the time-resolved laser-induced luminescence spectroscopy and time-resolved laser-induced chemiluminescence spectroscopy for the detection of lanthanides and actinides. Results of the experiments on U, Eu, and Sm detection by TRLIF (Time Resolved Laser Induced Fluorescence) method in blood plasma and urine are presented. Data on luminol chemiluminescence in solutions containing Sm(III), U(IV), and Pu(IV) are analyzed. It is shown that appropriate selectivity of lanthanide/actinide detection can be reached when chemiluminescence is initiated by transitions within 4f- or 5f-electron shell of lanthanide/actinide ions corresponding to the visible spectral range. In this case chemiluminescence of chemiluminogen (luminol) arises when the ion of f element is excited by multi-quantum absorption of visible light. The multi-photon scheme of chemiluminescence excitation makes chemiluminescence not only a highly sensitive but also a highly selective tool for the detection of lanthanide/actinide species in solutions. (author)

[en] Developing sustainable energy systems is a key driver for mitigating the global climate change in the framework of COP21 conference commitments. Nuclear energy is strongly concerned by such a perspective and we have developed a thorough approach to define relevant objectives to fulfill in order to meet such a requirement. On this basis nuclear energy systems need to be improved to increase the preservation of uranium natural resource and reduce their environmental footprints. It requires in both cases increasing energetic material recycling based first on the current LWR reactor fleet, in the future on SFR which would allow a much more efficient use of neutrons to consume uranium and produce energy. Furthermore, such reactor type would also allow minor actinides recycling, which would significantly reduce the ultimate waste toxicity and lifetime, and the repository footprint. In this perspective, recycling the actinides is clearly the cornerstone of any sustainable nuclear fuel cycle

[en] This paper addresses the radiolysis phenomenon on organic compounds leading to the formation of new molecular species such as gases and small soluble molecules. A large number of industrial and pure polymers were irradiated either with gamma radiation or swift heavy ions. Radiolytic yields were determined and the effects of the dose and the oxidation of materials were studied. A specific tool dedicated to the determination of the energy released through organic materials by alpha particles was developed. The release of chemical species such as carboxylic acids from more than twenty polymers under gamma and simulated alpha radiolysis at different cumulated dose was also described. (authors)

[en] Tridentate hydro soluble diglycolamide TEDGA (tetraethyl-diglycolamide) has been introduced in the EXAm process to complex Cm(III) and heavier lanthanides and allow the recovery of Am(III) alone. An exhaustive study has been carried out on the complexation of the ligand TEDGA with representative cations (La to Lu and An(III)) in order to enhance the knowledge on chemical mechanisms in nitrate solutions. The speciation of complexes LnTEDGA_n³⁺ has been carefully determined with different spectroscopic techniques such absorption spectrometry, ESI-MS, TRLIF and completed by molecular dynamics simulations. The equilibrium constants were measured by independent methods. By providing basic information on the structure of complexes and on the thermodynamics of the chemical systems, this study helps to support the modeling of the related liquid-liquid process. (authors)

[en] As part of the 2006 French Act on sustainable radioactive waste and waste management, CEA has been developing a process, (EXAm), in order to separate americium from curium and fission product downstream of COEX (TM) or PUREX processes. The goal is to recover Am up to 99%. The first step mainly consists of splitting americium from curium thanks to the diamide in organic phase combined with a complexing agent in high nitric acid. The low separation factor between Am and Cm leads to a very sensitive process flowsheet towards operating conditions. It is then difficult to manage high recovery yields with good purity. A model has been built taking into account complexation equilibria by TEDGA in aqueous phase and extraction equilibria in organic phase for each element. This model was put into the PAREX code to find the correct flowsheet, and then to conduct sensitivity studies regarding several parameters such as feed flow, acidity, temperature, solvent flow and reagent concentration. These studies have pointed out a high correlation between americium yield and decontamination factor and, also, an equivalence between any change of the most sensitive parameters and a change in TEDGA concentration. A running procedure was followed during two hot tests: the main concept was to start with a less efficient process and then to improve it during the test in order to reach required performances by adjusting the TEDGA flow rate. (authors)

[en] The kinetics and the mechanism degradation of erioglaucine dye in aqueous solution irradiated under γ-rays from ⁶⁰Co are investigated. From the results of the absorption UV-Vis spectra of 0.7 mM erioglaucine solution as function of dose, the concentration of erioglaucine decreases exponentially with increasing the gamma-irradiation dose and the plot on a logarithmic scale against the dose shows a clear pseudo first order rate. The apparent pseudo-first order rate constant (k(app)=1.8x10^-3 min^-1) was calculated. We also found the degradation mechanism as results of mass-spectrum analyses of the degradation products under the gamma-irradiated erioglaucine solution. The results show that the principal cleavage is the C-N bond. (authors)

[en] AREVA La Hague plants UP3 and UP2-800 started operations to reprocess spent nuclear fuel in 1990 and 1994 respectively. Aging equipment in these plants is a cause for concern as it could lead to process dysfunctions or production rate decrease. A few years ago, several columns had to be replaced in UP3-T4 plutonium purification facility because of clogging. Analyses revealed that TPH degradation products could be responsible for precipitating palladium compounds. 1 M NaOH solutions proved to be efficient to dissolve most of the precipitate. Therefore, several columns in both UP3 and UP2-800 are from now on washed periodically with 1 M NaOH solutions to avoid further clogging and to dissolve current precipitates. (authors)