Trapping and desorption of hydrogen isotopes under irradiation of zirconium by deuterium atoms of thermal energies

•Mechanism of hydrogen transport under atomic irradiation of zirconium is proposed.•The addition of oxygen causes the growth of the oxide layer and the increase of deuterium trapping.•Oxygen diffusion to the bulk provokes hydrogen transfer from the bulk to the oxide layer.•Irradiation leads to hydrogen desorption from the oxide layer by formation of HDO molecules.•Saturation of the oxide layer by hydroxyl groups creates conditions for accelerated transport of deuterium.

The results on trapping and desorption of hydrogen isotopes under irradiation of zirconium by deuterium atoms of thermal energies are presented. It is shown that the addition of oxygen to the operating gas during the irradiation causes the increase of the oxide layer thickness, the amount of hydroxyl groups in it and deuterium trapping in zirconium. Accelerated transport of deuterium atoms through the oxide layer saturated by hydroxyl groups is observed. Mechanisms of trapping and desorption of hydrogen isotopes and the role of oxygen in these processes are discussed.