Detritiation of Plasma-Facing Carbon Materials in Fusion Devices: The Role of Atomic Oxygen from a Quantum Molecular Dynamics Viewpoint

Quantum molecular dynamics calculations at constant temperature have been carried out in order to study the interaction between atomic oxygen and a hydrogen saturated graphite surface. It has been shown that atomic oxygen reacts at 300 K with the adsorbed hydrogen atoms to form hydroxyl radicals and water molecules. Part of these residue radicals adsorbs on the graphite forming hydroxylated structures. A study on the stability of these structures has shown that OH radical desorption begins at 500 K and formation of water molecules occurs by reaction between a desorbed hydroxyl radical and a hydrogen atom extracted from a neighboring adsorbed hydroxyl. The water molecules only very slightly interact with the graphite surface and are ejected into the gas phase.