PROCESSING OF GRAPHITE WITH CARBON-14 RETENTION

Waste graphite containing fragments of nuclear fuel and fission products is produced mainly as a result of operation of uranium−graphite reactors. Retention of radionuclides, including carbon-14, after disposal is an important goal of treatment procedure for such waste. Conversion of waste graphite into a stable waste form acceptable for long term storage and disposal has been previously considered from a theoretical basis. A self-sustaining transformation process involving graphite mixed with suitable reaction precursors was proposed. In the current study, such a self-sustaining process was studied both theoretically and experimentally in details. Three powdered reactant precursor mixtures were used: Al+SiO2 (#1), Al+TiO2 (#2), and Ti+SiO2 (#3). Numeric thermodynamic simulation was performed to determine equilibrium reaction temperatures and chemical compositions of the reaction products for a wide range of component ratios. The highest temperatures up to 2300 K were observed for precursor type #2. In contrast, reactions carried out using precursor type #3 demonstrated a minima