Xavier Deschanels
Centre national de la recherche scientifique
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Publication
Featured researches published by Xavier Deschanels.
New Journal of Chemistry | 2012
Philippe Makowski; Xavier Deschanels; Agnès Grandjean; Daniel Meyer; Guillaume Toquer; Frédéric Goettmann
In the context of increasing global energy demand associated with high prices for classical fossil fuels and rising concerns about CO2 emissions, nuclear power is attracting renewed interest. Despite the recent accident in the Fukushima power plant, numerous countries maintain very ambitious nuclear programmes. The Generation IV International Forum [A Technology Roadmap for Generation IV Nuclear Energy Systems, Generation IV International Forum, 2002] (an initiative launched by the US Department of Energy in 2000 to coordinate and promote efforts to design the next generation of nuclear power plants) supports works to develop new power plant designs and innovative concepts in the nuclear fuel cycle. These new concepts aim at achieving higher levels of security and resource efficiency as well as a higher resistance towards nuclear proliferation. Because of this blossoming of new ideas, mesoporous materials, which are already widely found in applications such as catalysis, sensing and optics, are expected to make their way in the field of nuclear power production. Up to now, some (hybrid) mesoporous solids have already been investigated as solid ligands to remove actinides and fission product contaminants from liquid effluents, but also as model materials to investigate radiation defects, as possible nuclear waste disposal form and as functional materials to be placed in or close to new forms of nuclear waste matrices. This contribution aims at reviewing the applications of mesoporous materials already described in the field of nuclear industry, and to underline some promising research directions in this area.
Radiochimica Acta | 2007
Christophe Jégou; B. Muzeau; Véronique Broudic; D. Roudil; Xavier Deschanels
The effects of αβγ radiolysis of water on oxidation and dissolution of the UO2 matrix of spent fuel were investigated in aerated media. The prospect of long-term interim storage of spent fuel assemblies in pools requires prior examination of an incident scenario in which a cladding failure could eventually lead to contact between water and the fuel. Radiolytic oxidation of the matrix together with the formation of secondary phases subject to volume expansion could then no longer be disregarded, and could enhance the degradation of the failed rod. To determine the amplitude of the alteration various spent fuel leaching experiments conducted at different degrees of oxidizing conditions and of accessibility of species at the reaction interface are discussed. This work is based on modeling the radiolysis processes and on various possible interpretations of leaching test results. Properly interpreting these results implies full knowledge of the fuel sample history, and the development of a rigorous experimental approach to eliminate any artifacts (problems due to the residual inventory at the grain boundaries, or to inaccurate estimates of the actual surface area). The results indicate that despite highly variable oxidizing conditions (presence of an external γ irradiation source, addition of H2O2, aerated water) the spent fuel matrix alteration determined from the release of tracer elements such as Cs and Sr is always the same. Conversely, allowing for the alteration conditions (no solution renewal and no complexants), the uranium concentrations in solution do indeed depend on the oxidizing conditions as does the nature of the secondary phases liable to precipitate.
MRS Proceedings | 2004
D. Roudil; Xavier Deschanels; Patrick Trocellier; Fran ç ois Jomard; Annick Boutry; Christophe Jégou; Sylvain Peuget; Dominique Gosset; Pierre Nivet
The behaviour and diffusion mechanisms of helium in nuclear ceramics, such as uranium dioxide spent fuel matrix and zirconolite for the specific conditioning of minor actinides, significantly impact the possible evolution of those matrices in interim storage or disposal conditions. In the framework of spent fuel storage studies, the additional diffusion of gas and fission products in uranium dioxide matrix is also an essential aspect of the RD this parameter will have to be taken into account to dimension the waste form. Diffusion coefficients measurements between 800 C and 1000 C, investigated by SIMS in the CNRS Meudon, showed a very slow diffusion of volatile fission products Xe, I, Te and Cs, with coefficients two or three order of magnitude lower than for helium.
Journal of Materials Science | 2013
Xavier Deschanels; Damien Hérault; Guilhem Arrachart; Cyrielle Rey; Agnès Grandjean; Guillaume Toquer; Renaud Podor; Thomas Zemb; Geneviève Cerveau; Robert J. P. Corriu
We compare the influence of using either molecular or colloidal precursors on the synthesis of a ceramic material containing SiC and porous carbon. Remarkably, the temperature of synthesis for crystalline SiC is independent of the route chosen. The excess carbon in the initial mixture is the source of the excess porous carbon that binds to the crystalline domains of SiC in the final products. Interestingly, increasing the initial area of surface contact between carbon and silicon in the ceramic precursor results in different porosities in the ‘meso’ range. Simultaneous control of the size and the relative amounts of Si and C in the precursors allows control to be exerted over the nature and texture of the final powders. A simple and general mechanism is herein proposed to explain the evolution of the surface area as a function of the volume fraction of residual carbon in the synthesised ceramic.
MRS Proceedings | 2006
D. Roudil; Christophe Jégou; Xavier Deschanels; Sylvain Peuget; Caroline Raepsaet; Jean-Paul Gallien; Véronique Broudic
During the initial period after disposal, in which no mass transfer occurs with environmental materials, spent fuel undergoes modifications mainly arising from the effects of α self-irradiation damage. To simulate this aging phenomenon and estimate the consequences on the matrix, an experimental study was carried out in which old UO 2 samples doped with short-lived actinides were characterized and analyzed. Changes that occur rapidly at the beginning of the aging process were identified in two lots of actinide-doped samples. Volume and microscopic swelling increased, reaching a maximum relative level of 1.5%. At the same damage level, microscopic swelling remained below 0.9%, suggesting that helium formation and atomic defects have a role in this regard. Similarly, the sample microhardness rapidly increased by up to more than 12%. Characterizing 238 PuO 2 sources showed at very high integrated and instantaneous doses, irradiation damage and helium accumulation at the grain boundaries resulted in grain decohesion or even powder formation. Helium mobility appeared to be modified by the presence of defects, and local implantation experiments were devised in the CEAs Pierre Sue Laboratory at Saclay to quantify this thermally enhanced diffusion component. The physical condition of the sintered PuO 2 pellets after 30 years of storage revealed a purely athermal diffusion mechanism, depending on the sample α activity.
Journal of Nuclear Materials | 2001
David Simeone; Xavier Deschanels; Dominique Gosset; J.P. Bonal; E. Berthoumieux
Abstract HfB2, a solid poor in boron, was irradiated by thermal neutrons in an experimental reactor. Using a nuclear microprobe, we have tracked lithium atoms produced by the 10 B ( n , α ) 7 Li reaction and compared the calculated and measured 7Li profiles in HfB2 irradiated samples. This comparison shows that Li atoms do not diffuse during irradiation (323 K). The comparison of non-annealed and annealed irradiated HfB2 plates clearly shows that lithium atoms do not migrate out of samples even at high temperatures (1273 K). These results associated to previous transmission electron microscopy (TEM) observations seem to show that lithium atoms are trapped by dislocation loops created by displacement cascades during neutron irradiation.
American Mineralogist | 2018
Anne-Magali Seydoux-Guillaume; Xavier Deschanels; Cedric Baumier; Stefan Neumeier; William J. Weber; Sylvain Peuget
Abstract Monazite, a common accessory rare-earth orthophosphate mineral in the continental crust widely used in U-Pb geochronology, holds promise for (U-Th)/He thermochronology and for the immobilization of Pu and minor actinides (MA) coming from spent nuclear fuel reprocessing. Previous results obtained on natural and plutonium-doped monazite have demonstrated the ability of this structure to maintain a crystalline state despite high radiation damage levels. However, the low critical temperature (180 °C), above which amorphization cannot be achieved in natural monazite under ion irradiation, does not explain this old and unsolved paradox: why do natural monazites, independent of their geological history, remain crystalline even when they did not experience any thermal event that could heal the defects? This is what the present study aims to address. Synthetic polycrystals of LaPO4-monazite were irradiated sequentially and simultaneously with α particles (He) and gold (Au) ions. Our results demonstrate experimentally for the first time in monazite, the existence of the defect recovery mechanism, called α-healing, acting in this structure due to electronic energy loss of α particles, which explains the absence of amorphization in natural monazite samples. This mechanism is critically important for monazite geo- and thermochronology and to design and predictively model the long-term behavior of ceramic matrices for nuclear waste conditioning.
Journal of Nuclear Materials | 2004
D. Roudil; Xavier Deschanels; Patrick Trocellier; Christophe Jégou; Sylvain Peuget; Jean-Michel Bart
Journal of Nuclear Materials | 2008
Valérie Picot; Xavier Deschanels; Sylvain Peuget; Benoit Glorieux; Anne-Magali Seydoux-Guillaume; Richard Wirth
Journal of Nuclear Materials | 2014
Xavier Deschanels; Anne-Magali Seydoux-Guillaume; Valérie Magnin; A. Mesbah; M. Tribet; M.P. Moloney; Y. Serruys; Sylvain Peuget