Effect of metal fission products on the thermal transport of SiC/PyC nanocomposites: Insight from molecular dynamics simulations

Abstract

The High-Temperature Gas-cooled Reactor (HTGR) is a generation-IV advanced nuclear reactor, which has a special nuclear fuel design, and the tiny TRISO particle (∼1 mm) is adopted. Each TRISO particle is coated with four layers, and silicon carbide (SiC) and pyrolytic carbon (PyC) are the two main components. The heat transfer process at the SiC/PyC interface is important to compute the temperature distribution inside the TRISO particle, but it is quite difficult to research this phenomenon based on experimental results. However, the Molecular dynamics (MD) method could be seen as a viable simulation scheme in micro-scale phenomena. The non-equilibrium molecular dynamics (NEMD) was employed to compute the temperature profile and interfacial resistance of SiC/PyC nanocomposites. In addition, seven atomic models embedded with noble metal fission products, including silver (Ag), palladium (Pd), and ruthenium (Ru), were built, with both aggregated nanoparticle state and atomically dispersed state being investigated. The phonon density of states was used to quantify differences in heat transfer performance. The results show that the Kapitza resistance of the SiC/PyC interface decreases gradually with increasing temperature due to the weakening of phonon scattering, but the FP atoms could reduce the heat transfer capability of SiC/PyC nanocomposites; the dispersed atoms have a more significant effect than the FP nanoparticle as an integral part. This study reveals the mechanism underlying the fission products’ influence on the heat transfer characteristics of TRISO coating layers, providing a theoretical basis for enhancing the comprehension of their interaction.