Irradiation Damage Study of nc-SiC with Molecular Dynamics Cascade Simulations

Paul Kamenski, Izabela  Szlufarska, Dane Morgan, Materials Science and Engineering

     The increasingly harsh radioactive environment found in nuclear fusion reactors, as compared to current fission reactors is calling for the study and development of novel materials to withstand increased radiation damage. Silicon carbide (SiC) is known to have excellent mechanical properties at high temperatures, and due to its small cross section for interactions with cosmic rays and neutrons, SiC has been proposed for use in fusion reactors. Nanocrystalline (nc) SiC has been experimentally shown to exhibit super-hardness and increased fracture toughness, exceeding that of single crystal SiC, also verified and analyzed through computer simulations. These previous results provide good promise for the use of nc-SiC as a structural reactor material; however, no studies have been done regarding the effects of irradiation on nc-SiC.

     Since the primary radiation damage event, when a nuclear reactor byproduct transfers its energy to the surrounding structural material, occurs on a picosecond timescale and angstrom length scale, this phenomenon cannot be studied directly through experiments. Fortunately, this timescale is the exact timescale in which molecular dynamics simulations of materials intrinsically function.

 Nanocrystalline Sample. This system contains 1,871,135 atoms, has a box length of 28.3 nm and an average grain size of 10 nm.

     Continuing the motivation for our computational studies, if new materials, such as nc-SiC, are designed to be more resistant to the damage caused by irradiation, they could extend the production lifetime of nuclear reactors. This would also reduce the safety risks for reactor employees switching out spent fuel rods and reduce the risk for a major accident. Financially, longer lifetime reactors would enhance electricity supply and keep prices low for home and business owners. Finally, regarding environmental concerns for electricity production, nuclear power plants, from cradle to grave, emit less than a tenth of the CO₂ that coal power plants emit.

     With these motivations in mind, our research will utilize molecular dynamics cascade simulations, designed to accurately depict the atomistic effects of irradiation. This work will complement the primary damage cascade studies that have been done on nc bcc and fcc metals and for a single grain boundary (GB) in SiC by previous groups, providing a holistic picture regarding the suitability of nc-SiC as a structural material in nuclear reactors. In general, by means of analyzing atomic scale events, our long term goal is to build a multi-scale model to describe the kinetics of primary damage defects in irradiated nc-ceramics, ultimately to design damage-resistant materials.