Void formation in nickel irradiated with nickel ions

The formation of voids in nickel has been studied under the radiation conditions simulating the reactor ones. A commercially pure nickel has been annealed and then irradiated with helium ions for the concentrations ranging from 10-4 to 10 at%. The samples have been further irradiated with 49 keV nickel ions at a temperature of 500 deg C by integral doses from 2x1016 to 1.6x1017 ion/cm2. It is shown that for one and the same radiation dose the void density increases and the void size-decreases as the helium concentration grows. Moreover, as the dose grows the increased swelling is observed. It is also found out that for one and the same dose the swelling of nickel, preliminary saturated with helium, is essentially lower than in the case of a helium-free material. Typical functions for swelling against helium concentration and the radiation dose, are shown as well as the normalized functions of a void-size distribution