Block-type HTGR spent fuel processing: CEA investigation program and initial results

Considering the criteria put forward by the Generation IV Forum to select future nuclear systems (preservation of resources, minimization of final waste impact, economics, etc.), the impetus for the very high-temperature He-cooled reactor raises the issue of processing the fuel in the context of a closed cycle with actinide recycling. Due to the unique structure of the particle fuel used for this class of reactors, the difficulties essentially involve accessibility to the uranium kernels coated by carbon and SiC layers and dispersed in a large volume of graphite. Starting from past experience in this field, a research program has been recently undertaken by the CEA to propose attractive solutions. The mechanical extraction of compacts from the spent fuel blocks appears to be a promising approach, as well as removing the graphite from the compacts by pulsed currents to free the particles. Subsequent removal of the carbon and silicon carbide layers by high temperature oxidation or by carbochlorination to access the kernels is assessed. For actinide recycling, gelation appears to be a suitable process for fabricating the kernels. This paper provides a brief overviews of the developments currently in progress at the CEA.