EFFECT OF VACANCY LOOPS ON SWELLING OF IRRADIATED MATERIALS

Calculations by Bullough, Eyre and Krishan [1] indicated that the vacancy loops produced in damage cascades might be important up to the peak swelling temperature during neutron irradiations. This represents a potential source of error for electron irradiation experiments, which do not produce damage cascades. More realistic calculations by the present authors, using revised electron swelling data for 316 stainless steel, can satisfactorily explain the observed neutron and nickel ion swelling behaviour of this steel if much smaller vacancy clusters are produced, in accord with Straalsund. The calculations show that the athermal production of vacancy loops does not affect neutron swelling above ≈ 450°C, so that electron simulations are valid at elevated temperatures. Ion simulations are more complicated because the effect of the vacancy loops is temperature shifted upwards by at least 150°C, and is in danger of overlapping the high temperature cut-off in some cases. © 1979.