[en] Research program aimed at creation of a mathematical model of extractional separation of uranium and plutonium during purex-process in a pulsed column, taking into account all variable parameters, has been developed. The modelling was realized in several stages: modelling of extractional separation of U and Pu in mixer-settlers, modelling of processes in the pulsed column, and, finally, development of complete model. The modelling was realized taking into account such values as chemical state of U, Pu, HNO₃, Tc in solution, their distribution between aqueous and organic phases, redox reactions, etc. As a result a multicomponent mathematical model permitting to calculate simple extraction operations on nuclear fuel reprocessing is created. Experimental and theoretical results are compared. 1 ref.; 3 figs

[en] The reductive plutonium stripping operations carried out in the Purex process, such as uranium/plutonium splitting, are sometimes difficult to get under control. When these operations are performed in pulsed columns, added to the complexity of the chemical reactions involved, are the specific features of this type of contactor, whose performance is governed by a set of equally complex factors. The perfect control of this process, both in the design phase and in the operating phase, requires the availability of a simulation tool incorporating the various aspects of the operation. The French Commissariat a l'Energie Atomique accordingly set up a research programme aiming to develop a mathematical model simulating the behaviour of the different species concerned in unsteady state conditions

[en] CEA has conceived a basically new annular centrifugal contactor referred to as ECRAN (initials of French words for centrifugal extractor with filled agitated rotor) with two original designs: - there are two rotors driven by the same shaft and positioned the one under the second; the upper accomplishes the separation of the phases, the lower the mixture. Depending on process operation, it is possible to design a separation rotor with high diameter and high centrifugal force and a mixing rotor allowing good mixing at a given rotor speed, - the two phases are fed at the bottom of the mixing zone by means of two channels and discharge into the separation rotor after mixing; so the emulsion fills all the mixing zone and its volume is constant at any experimental conditions. (authors)

[en] Three types of liquid-liquid extraction equipment are used in industrial reprocessing plants. Each is described below, with a special focus on pulsed columns and centrifugal extractors, which have been the subject of an extensive R and D program by the French Atomic Energy Commission (CEA). Various models have been developed to simulate equipment behavior and flowsheets. The excellent results obtained during industrial operation of the UP3 and UP2-800 plants in La Hague have confirmed the validity of the choices made during the design phases and pave the way for future improvement of the reprocessing process, from a technical and a financial standpoint

[en] In June 2006, a new act on sustainable management of radioactive waste was voted by the French parliament with a national plan on radioactive materials and radioactive waste management (PNG-MDR). Concerning partitioning and transmutation, the program is connected to 4. generation reactors, in which transmutation of minor actinides could be operated. In this frame, the next important milestone is 2012, with the assessment of the possible transmutation roads, which are either homogeneous recycling of the minor actinides in the whole reactor fleet, with a low content of M.A (∼3%) in all fuel assemblies, or heterogeneous recycling of the minor actinides in about one third of the reactor park, with a higher content of M.A. (∼20%) in dedicated targets dispatched in the periphery of the reactor. Advanced processes for the recycling of minor actinides are being developed to address the challenges of these various management options. An important part of the program consists in getting closer to process implementation conditions. The processes based on liquid-liquid extraction benefit from the experience gained by operating the PUREX process at the La Hague plant. In the field of extracting apparatus, a large experience is available. In the field of extracting apparatus, a large experience is already available. Nevertheless, the processes present specificities which have to be considered more precisely. They have been classified in the following fields: - Evolution of the simulation codes, including phenomenological representations: with such a simulation tool, it will be possible to assess operating tolerances, lead sensitivity studies and calculate transient states; - Definition of the implementation conditions in continuous contactors (such as pulse columns), according to the extractant physico-chemical characteristics; - Scale-up of new extractants, such as malonamides used in the DIAMEX process, facing purity specifications and costs estimation; - Solvent clean-up studies to assess long term behavior of the separation systems towards radiolysis and hydrolysis: the first question is to assess basic scrubbing efficiency to remove acidic degradation products (coming from radiolysis and hydrolysis). The irradiation loop settled in Marcoule since 2004 will be helpful for that. In addition, the need for complementary treatments such as soft or flash distillations will be considered. - Liquid waste management: the question is to assess the impact of organic reagents introduced in the various steps of the flowsheet (especially downstream steps). If necessary, complementary treatments will be developed. - Transitional operations: the recovered actinide flow must be compatible with downstream co-conversion processes. This paper describes the studies already started or planned till 2012 in each field, to move toward potential industrialization (authors)

[en] R and D studies are conducted at CEA/DEN to assess the potentialities of the pyrochemical processes which could be an advantageous alternative to hydrometallurgy for the reprocessing of: (i) targets as well as dedicated fuels for M.A transmutation if multiple recycling is considered, (ii) Generation IV gas cooled reactors. This paper gives an overview of the major experiments performed either in molten fluorides or chlorides. (authors)

[en] This conference dealt with 3 main topics: analytical innovation in separation processes (hyphenated techniques, analytical chips,...), actinide recycling (extraction, interfaces, processes,...) and chemistry and thermodynamics of actinides. This document is composed of the slides of the presentations

[en] The extension of the UP2 plant at La Hague includes a new plutonium purification cycle using multistage centrifugal extractors to replace the previous cycle that used mixer/settler banks. This type of extractor is suitable for the treatment of fuel containing a high proportion of plutonium-238, as its short residence time limits solvent degradation. This paper deals with the research done to devise its flowsheet, the centrifugal extractors in which it is operated, as well as the feedback of six years of industrial operation

[en] Mass production of hydrogen is a major issue for the coming decades particularly to decrease greenhouse gas production. The development of fourth-generation high temperature nuclear reactors has led to renewed interest for hydrogen production. In France, the CEA is investigating new processes using nuclear reactors such as the Westinghouse hybrid cycle. A recent study was devoted to electrical modeling of the hydrogen electrolyzer, which is the key unit of this process. An extensive literature review led to the choice of electrolyte and electrode materials, and the preliminary design of a new cell for production of hydrogen was evaluated. This paper describes an improved model coupling the electrical and thermal phenomena with hydrodynamics in the electrolyzer. The hydrogen electrolyzer chosen here is a filter press design comprising a stack of cathode and anode compartments separated by a membrane. Hydrogen is reduced at the cathode and SO₂ is oxidized at the anode. In a complex reactor of this type the main coupled physical phenomena involved are forced convection of the electrolyte flows, a plume of hydrogen bubbles that modifies the local electrolyte conductivity, and irreversible processes (Joule effect, over-potentials, etc.) that contribute to local overheating. The secondary current distribution was modeled with a commercial FEM code, Flux Expert^R, which was customized with specific finite interfacial elements capable of describing the potential discontinuity associated with the electrochemical over-potential. Since the finite-element method is not capable of properly describing the complex two-phase flows in the cathode compartment, the Fluent^R CFD code was used for thermohydraulic computations. In this way each physical phenomenon was modeled using the best numerical method. The coupling implements an iterative process in which each code computes the physical data it has to transmit to the other one: the two-phase thermohydraulic problem is solved by Fluent^R using the Flux Expert^R current density and heat sources; the secondary distribution and heat losses are solved by Flux Expert^R using Fluent^R temperature field and flow velocities. The computations use two different meshes and interpolations from one mesh to the other require a 3D algorithm to localize the calculation points. A set of dedicated library routines was developed for process initiation, message passing, and synchronization of the two codes. The first results obtained with the two coupled commercial codes give realistic distributions for electrical current density, gas fraction and velocity in the electrolyzer. A design optimization phase is in progress before proceeding to the final design and manufacturing of a pilot electrolyzer. (authors)

[en] Liquid-liquid extraction is the central technology in metal recycling. An important application is the recovery of major actinides uranium and plutonium. The viscosity increase of the organic phase when liquid-liquid extraction processes are intensified causes difficulties for hydrometallurgical processes on industrial scale. In this work, we have analyzed this problem for the example of N,N-dialkyl-amides in the presence of uranyl nitrate experimentally. Furthermore, we present a minimal model at nanoscale that allows rationalizing the experimental phenomena by connecting the molecular, mesoscopic and macroscopic scale and that allows predicting qualitative trends in viscosity. This model opens broad possibilities in optimizing constraints and is a further step towards knowledge-based formulation of extracting microemulsions formed by microstructures with low connectivity, even at high load with heavy metals