Investigating Radiation Damage at a Solid-Liquid interface due to Neutron Irradiation using Molecular Dynamics

The study focuses on exploring the effects of neutron flux irradiation at a solid-liquid interface within a tokamak fusion system using a toy model of solid tungsten and liquid vanadium. The study is motivated by a specific type of breeder system for a tokamak fusion reactor design which utilises molten lithium as a breeder component due to several intrinsic advantages offered by lithium. To counteract some of the challenges of utilising lithium in the liquid phase, the lithium is encased in solid vanadium to provide structural support against the extreme temperature and pressures in a fusion system. Compared to other alloys, the lithium-vanadium system exhibits excellent compatibility with vanadium.

However, the damage occurring in the solid-liquid interface is largely unstudied. The aim of this work is to bridge this gap and gather data on the effect of collision cascades occurring near the solid-liquid interface through molecular dynamics. At present, no suitable binary interaction model exists for simulating a lithium-vanadium system. Hence, we study a substitute system for which a binary model exists: solid tungsten and liquid vanadium system. The binary potential simulated was an embedded atom model (EAM), specifically the Finnis-Sinclair (FS) type due to its computational efficiency. The system was modelled using molecular dynamics (MD) code LAMMPS and visualized using Ovito and python. This study focuses on the case where the Primary Knock-on Atom (PKA) is incident at the interface from the liquid bulk and evaluates the resultant characteristic damage in the system.