Deuterium diffusion in Zr oxide layer irradiated with Zr and O ions

The effects of irradiation on hydrogen absorption of zirconium alloys for fuel claddings of light water reactors were investigated by the irradiation of sample specimens with 8.0 MeV Zr or 4.0 MeV O ions. The specimens were preliminary steam-corroded and covered with a 1.6 – 1.8 μm thick oxide layer. After irradiation, the deuterium depth profiles in the oxide layer were observed in situ by nuclear reaction analysis where the specimen was continuously exposed to deuterium plasma or vacuum. The oxide layer consisted of an outer non-protective layer with high hydrogen diffusivity and an inner barrier layer with low hydrogen diffusivity. The thickness of the barrier layer increased between 0.5 and 2 dpa until most of the oxide layer became occupied with the barrier layer. This phenomenon is related to irradiation defects and not to the irradiated ions. It is possible that the hydrogen absorption rate in reactors is less than that expected from out-of-pile experiments under conditions without irradiation. (author)