Influence of pre-existing defects on thermal transport in nuclear graphite

Nuclear graphite is a critical material in high-temperature nuclear reactors due to its superior thermal and mechanical properties. The manufacturing process leaves multi-scale ‘pre-existing’ defects that can affect thermal transport characteristics. Because these defects are remnant of graphitization temperature, they cannot be thermally annealed. This study employs a non-thermal electron wind force (EWF) annealing technique to avoid this obstacle. 2 min of EWF treatment of the as-received graphite IG-110 at temperatures below 100 °C led up to 67% increase in thermal diffusivity and ~ 35% decrease in electrical resistivity in average. Differential scanning calorimetry also showed similar outcome for specific heat. X-ray diffraction characterization was performed by fitting a bi-modal crystallite size distribution model to reveal the enhancement in crystallinity after the EWF treatment. The findings emphasize the potential of EWF annealing for optimizing thermal performance in nuclear graphite and its implications for reactor efficiency and safety.. Authors: Warner, Luke [Pennsylvania State Univ., University Park, PA (United States)]; Liu, Gongyuan [Pennsylvania State Univ., University Park, PA (United States)]; Wonderling, Nichole M. [Pennsylvania State Univ., University Park, PA (United States)]; Du, Jing [Pennsylvania State Univ., University Park, PA (United States)]; Windes, William E. [Idaho National Laboratory (INL), Idaho Falls, ID (United States)] (ORCID:0000000188030885). DOE Contract: AC07-05ID14517; NE0009129. Subjects: Annealing; Crystallographic structure; Materials Science; Nuclear Chemistry; Nuclear Energy; Nuclear Transport; Nuclear Waste; Nuclear materials; Thermal Process Engineering; Thermal diffusivity; X-ray diffraction (XRD); defects; high temperature; high temperature nuclear reactors; nuclear graphite; thermal transport