In this talk, we first present a simulation method for the dynamics of dislocation arrays. In this numerical method, dislocation arrays are considered as continuous surfaces in 3D, and the level set representation is used for these dislocation array surfaces. Simulations are performed for dislocation arrays bypassing different particles under applied stress. We also consider systems of parallel straight dislocation walls and develop continuum descriptions for the short-range interactions of dislocations by using asymptotic analysis. We then investigate the defect sink properties of low-angle GBs under both non-irradiation and irradiation conditions, and show the influence of low-angle tilt GB structure on the sink efficiency.