The solubility and diffusion coefficient of helium in uranium dioxide

► The solubility and diffusivity of He in single-crystal UO2 were determined. ► The determined He solubility lay within the scatter of the available data. ► The determined He diffusivity was in good agreement with recent experimental data. ► The He behavior was analyzed in terms of a simple interstitial diffusion mechanism. ► The experimental diffusivity was much lower than that analyzed theoretically.