Radiation hardening of vanadium by 14 MeV neutrons

Radiation hardening of pure vanadium has been studied by irradiations with 14 MeV neutrons and fission neutrons. The yield stress at room temperature increases remarkably after irradiation, while its temperature dependence decreases. Measurements of the activation parameters for deformation lead to a conclusion that the hardening is athermal and the thermal obstacles have changed to weaker obstacles. The athermal hardening calculated from the observed defect size, density and the obstacle strength parameter is too small to account for the observed hardening. It is suggested that obstacles which are invisible by TEM are present.