Fabrication of Graphitic Matrix Fuel Compacts Applicable to High Temperature Gas Cooled Reactors

Abstract

Canadian Nuclear Laboratories (CNL) has established a comprehensive research program to develop expertise and capabilities on fuel relevant to High Temperature Gas-cooled Reactors (HTGR). Many benefits associated with the HTGR reactor design, such as high operating temperature and inherent safety performance, rely on the robust, coated TRI-structural ISOtropic (TRISO) particle fuel. Utilizing TRISO fuel requires the particles to be contained within a suitable matrix material, typically forming a compact or pebble. Fabrication of such compacts has been explored through experimental efforts at CNL’s Chalk River laboratories and the University of British Columbia-Okanagan. These efforts have included developing methodologies to prepare suitable graphitic matrix powder precursor via jet milling, in line with those employed as part of the Advanced Gas Reactor (AGR)-5/6/7 fuel irradiation campaign in the US. The matrix precursor has been successfully used in particle overcoating trials and compact fabrication studies performed with the novel application of spark plasma sintering (SPS). The initial results show SPS was able to achieve matrix densities greater than 1.70 g·cm^-3, comparable with those achieved by more conventional fabrication methods used in the AGR program. Microstructural characterization of the compacts has been explored through non-destructive X-ray Computed Tomography and conventional microscopy methods. The results obtained through this study demonstrate that SPS may provide a promising alternative manufacturing route for TRISO-loaded compact fabrication applicable to onward studies.