[en] The out-diffusion of helium, introduced into polycrystalline zirconium at room temperature by ion-implantation at 100 keV to a peak concentration of 1ppm, was found to occur in two principal regions. Two evolution rate maxima, obtained during post-implantation target annealing at 2.6⁰K s^-1, were observed in close proximity at 330⁰C (0.28 Tsub(m)) and 450⁰C (0.34 Tsub(m)) comprising the principal stage, with a subordinate stage occurring at 600⁰C (0.4 Tsub(m)). These data were compared with similar maxima observed in nickel at 600⁰C (0.5 Tsub(m)) and 850⁰C (0.65 Tsub(m)). The results imply a high helium diffusivity over the 0.5 mm experimental range in comparison with nickel, and an exceptionally high diffusivity taking into account the melting temperature of zirconium. On the basis of a diffusion model proposed earlier for nickel, activation energies of 1.37 and 1.66 eV have been assigned to the principal maxima at 330⁰C and 450⁰C, and a value of 2.41 eV to the maximum at 600⁰C. The long range diffusivity of helium manifested by its thermal evolution from uniformly filled 120 mm thick foils was found to be much lower than that measured for short range migration. An empirical activation energy of approximately 3 eV was estimated for this process, thought to be a result of bubble migration. The release of helium from zirconium has been explained by comparison with nickel data. The proposed substitutional de-trapping mechanism has been invoked to account for the principal evolution rate maxima at 330⁰C. Helium release observed at 600⁰C has been explained by the annealing of radiation damage, so allowing gas trapped therein to be evolved. (author)