Dislocation Bias in an Anisotropic Diffusive Medium and Irradiation Growth

An understanding of the mechanisms producing dimensional changes in reactor structural materials is of major importance for reactor design purposes. When a crystalline material is irradiated by energetic neutrons, ions or electrons, damage is produced in the form of atomic displacements, which subsequently evolve into a supersaturation of freely migrating vacancies and interstitials * in the temperature range under consideration. The consequent macroscopic behaviour of the material depends on the migration of these point defects and their eventual annihilation at crystal defects such as dislocations, voids and grain boundaries. In principle, the kinetics of the point defects and, hence, the behaviour of the irradiated material can be calculated by solving the corresponding drift-diffusion problem. However, in practice, a complete solution of this problem is difficult because of the complicated interaction fields and boundary conditions usually encountered in irradiation damage experiments. So far, the most detailed and successful way of describing the