نبذة مختصرة : In an effort to reduce the volume of nuclear wastes and to allow the reuse of remaining fissile materials, a strategy for management of high temperature reactors (HTR) fuel was developed in this study. The volume reduction passes through the separation of highly radioactive TRISO particles with fuel kernels from the slightly radioactive graphite matrix (both combined in a fuel assembly called "compact") while the total recycling option requires the separation of the valuable kernel from the particle coating as ultimate waste. The separation methods must preserve the integrity of TRISO to prevent the release of radionuclides. A thermal shock treatment between liquid nitrogen and hot water allows for a partial destruction of the compact but only few particles are separated. Alternatively, graphite erosion by a high pressure water jet presents the risk of fracturing the particles. Better is the total combustion of carbon which releases all the particles. The treatment of compacts by ultrasounds in water erodes the graphite as function of the intensity, distance and direction of attack, temperature and gas saturation, and provides clean particles. The acid attack of compacts by a mixture H2O2 + H2SO4 causes the intercalation of graphite by acid, which inflates the structure and releases the intact particles. The TRISO on one hand and coatings on the other hand were then vitrified by sintering to achieve a high density, up to a rate of 25% vol. Finally, the leaching of composites in ultrapure water at 90°C shows strong confinement properties. ; Dans un souci de réduction du volume de déchets nucléaires et de revalorisation des matières combustibles, une stratégie de gestion du combustible des réacteurs à haute température (HTR) est développée dans cette étude. La réduction de volume passe par la séparation des particules TRISO hautement radioactives et du graphite faiblement radioactif (les deux étant réunis dans un assemblage de combustible appelé "compact") tandis que le recyclage total nécessite la séparation du ...
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