Analysis of the effects of hydrostatic stress on swelling

The effects of hydrostatic stress on void growth during irradiation has been studied using a diffusion model similar to that developed by Bullough and Perrin. Pressure effects were introduced into the theory via the boundary values assigned to the vacancy and interstitial concentrations in close proximity to voids and dislocations. General conclusions of the analysis were: 1. At irradiation temperatures equivalent to the maximum swelling rate and above, the void growth rate increases linearly with hydrostatic tensile stress. Using estimated parameters for stainless steels no effect was found for temperatures below about 450°C.2. For constant structure, the stress effect was found to have the temperature dependence associated with self diffusion.3. The stress effect may be recognized as a form of Nabarro Herring creep and is therefore independent of damage rate. Stress effects could thus, in principle, be measured during postirradiation annealing experiments.Because of the uncertainties associated with many of the parameters incorporated in the swelling model, it was not possible to provide a reliable quantitative description of the effects of stress.