Helium diffusion and bubble nucleation in the dislocation core during irradiation

The theory of homogeneous nucleation is used to determine the relationship between the diffusion kinetics of helium and the density of helium bubbles both in the matrix and dislocations. The flux of helium atoms reaching a dislocation line is taken to be the effective helium generation rate for the dislocation. In this calculation the effect of the presence of sinks in the matrix is taken into account. Furthermore, the calculation determines the effect of continuously changing flux of helium atoms to the dislocation core due to changes in the sink strength in the grain interior as a function of irradiation time and helium generation rate. The bubble spacing on a dislocation line is then calculated in terms of diatomic nucleation using the condition of nucleation saturation.