Des progres scientifiques et techniques dans la conception des echangeurs de chaleur a surface raclee

National audienc

From the Bataille's Law to the Am-recycling integral experiments, overview of 25 years of RandD in CEA on Minor Actinides Partitioning Processes

International audienceIn Dec.1991, French Parliament voted the first French waste management Act which among others, requests the launching of a large RetD program to study the potential partitioning and transmutation of long-lived radionuclides (LLRN) in order to decrease the waste long-term toxicity and volume. Indeed, LLRN transmutation was thought to be able to reduce 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. This research has been supported since that date by the successive French governments. First it allows France to demonstrate that recycling the long lived fission products is not worth to be done, and in the new Waste Management Act voted in 2006, it was decided to focus the work on the sole minor actinides. This research effort was very significant and was for a significant part conducted within the well-known Atalante nuclear facility in Marcoule. Over the 25 years of development, different types of strategies were studied, from the early multi-stage and complex DIAMEX-SANEX-SESAME processes to the most recent innovative SANEX, covering both the grouped extraction of MA within the GANEX process and the most recent sole-Americium recycling within the EXAm process. These developments were supported by a robust and long-standing approach allowing successively the screening of the potential extractants, the quantification of their extractive properties, the development of relevant chemical models to model the actinides-extracting molecules interactions the development of specific separation equipments. At the end, all these processes were successively qualified on a few kg of spent nuclear fuel within the Atalante CBP facility. This wide research program allows France to get in hands a flexible portfolio of MA recycling processes for different types of strategies that could in the future be industrially deployed after an industrial upscaling phase. In order to complete this large program, CEA initiated in 2010 a demonstration experiment, the so-called integral experiment, which aims to re-irradiate in a Material Testing Reactor some fuel pellet manufactured from recycled Americium. A few grams of americium have already been recovered from commercial spent nuclear fuel thanks to the EXAm process and is now going to be converted in powder and pellets.This large research program also associated the European scientific community thanks to successive European Research Projects which were selected and funded by the European Commission under the coordination of CEA. With this long-standing research program, France demonstrated the feasibility of recycling minor actinides for transmutation within 4th generation fast neutrons reactors. A general overview of these 25 years of successful and innovative research history will be synthesised in this presentation

Sechage sur cylindres dans les IAA : nouvelles techniques, nouvelles perspectives

National audienc

1992-2017: 25 years of success story on Minor Actinides Partitioning Processes Development

International audienceIn the frame of the successive 1991 and 2006 Waste Management Acts, French government supported a very significant RetD program on partitioning and transmutation of minor actinides (MA) in fast reactors. This program aimed 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 radiotoxicity 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. Over the 20 years of development, different types of strategies were studied, from the early multi-stage DIAMEX-SANEX processes to the most recent innovative SANEX, from the grouped extraction of MA thanks to the GANEX process to the most recent sole Americium recycling thanks to the EXAm process. These developments were supported by a robust and long-standing approach allowing successively to screen the potential extractants, to quantify their extractive properties and develop relevant chemical models to simulate it and to address their hydrolysis and radiolysis resistance. Finally, all these processes were qualified on a few kg of spent nuclear fuel within the Atalante CBP facility. This wide research program allows France to get a flexible portfolio of MA recycling processes that could be implemented after industrial upscaling. More recently, CEA initiated a demonstration experiment, the so-called integral experiment, which aims to re-irradiate in a Material Testing Reactor some fuel pellets manufactured from recycled UAm. Most recent results on these key experiments will be presented. Finally, several European Research Projects were funded in parallel by the European Commission and allow studying alternative separation processes. A general overview of these 20 years of successful and innovative research history will be synthesized in this presentation

Explaining the persistence of informal institutions: the role of informal networks

The paper unpacks the “black box” of informal institutions and theorize about the role of informal networks in channeling continuity and change in informal institutions. Specifically, we argue that when informal institutions are enacted by informal networks that are “relatively affective” and “relatively closed,” their persistence is higher than the persistence of informal institutions that are enacted by “relatively open” and “relatively instrumental” networks

French Perspective On The Respective Interests Of Hydro- And Pyro-Chemical Processes For Recycling Future Spent Nuclear Fuels

International audienceFor more than 25 years, France has operated the treatment and recycling of spent nuclear fuels at an industrial scale in the AREVA La Hague and MELOX plants. This industrial success story has been based on the historical PUREX separation process which allows the U and Pu separation from the fission products and minor actinides thanks to their selective extraction by the TriButylPhosphate non-miscible molecules. Beyond the initial PUREX process, more innovative processes have been developed and tested at representative scale, such as (U,Pu) co-management separation process or different minor actinides enhanced partitioning processes. Liquid/liquid extraction processes hence demonstrated their suitability both to be industrially deployed and to be upgraded and extended towards additional recycling objectives for oxides fuels. In the same time, pyrochemical processes have been developed since the early 60's for recycling of the metallic fuels. Later on, this process was implemented at the pilot scale for recovering uranium from sodium bonded metallic fuel of the EBR2 reactors. Laboratory scale processes have also been developed for recovering the plutonium and the minor actinides by using a reactive cadmium cathode. More recently, Korea developed such type of processes at the engineering scale, on surrogate materials. The long term aim is to recycle current commercial spent nuclear fuels.Furthermore, most of the future 4th generation nuclear systems plan to expand the actinides recycling, for allowing a better use of natural uranium. Uranium-238 efficient consumption would hence be possible thanks to the Pu-multirecycling in fast neutrons reactors. Recycling would therefore be the core of future nuclear energy systems with a strong requirement of efficiency and safety. From the current situation, two main routes seem to be envisaged for recycling future commercial spent nuclear fuels, pyro- or hydro-processes. This paper aims to depict the respective values of both types of processes for future fuel cycles and assess what could be their most relevant potential targets