Current Status of Purification of Indonesian Natural Graphite as a Candidate for Nuclear Fuel Matrix by Hydrometallurgy and Pyrometallurgy Methods

Abstract

Indonesia has natural graphite reserved in Sulawesi, Sumatera and Kalimantan islands. The highest graphite content was observed in Sanggau Region, West Kalimantan. Indonesian natural graphite has the potential to be used as fuel matrix in Pebble Bed Reactor (PBR) type - High Temperature Gas Cooled Reactor (HTGR). To increase self-reliance of graphite supply and decrease graphite import for fuel matrix purposes, it is necessary to master the purification technology of graphite. Graphite matrix in Pebble Bed Reactor (PBR) fuel has an important role. It is not only used as neutron moderator and structural material to protect nuclear fuel but also as heat transfer media. Therefore, the graphite matrix must meet the physical and chemical criteria specified for PBR fuel. This paper focuses on current status of purification of Indonesian natural graphite as a candidate for nuclear fuel matrix using hydrometallurgy and pyrometallurgy. Acid and acid mixtures such as HF, HNO3+H2SO4 and HF+HCl+H2SO4 were used for the hydromet-allurgy purification process, while Arc Plasma System were used for pyrometallurgy methods. Characterization for the purified graphite includes physical and chemical properties. The result showed that Indonesian natural graphite obtained from hydrometallurgy was classified into low nuclear grade graphite but it still could be used as nuclear fuel matrix PBR - HTGR. The graphitization degree needs to be increased and the impurity content needs to be decreased for the purified Indonesian graphite using hydrometallurgy method. The Indonesian natural graphite obtained from preliminary pyrometallurgy methods has 96.78 % graphite content according to SEM (surface) observation and the graphite content needs to be increased into nuclear grade graphite.