[en] This paper presents a refined hydrogen diffusion model with applications in material engineering for fusion nuclear technology, since diffusion is known to be the main mechanism of hydrogen transport under static or quasi-static loading conditions. The model considers not only stress assisted diffusion (in which hydrogen transport is driven by the hydrostatic stress field) but also stress-and-strain assisted diffusion where both the hydrostatic stress and the plastic strain fields play relevant roles, thus accounting for the presence of residual stresses generated by metal working, or mechanical pre-damage in the form of cumulative plastic strain, hydrogen traps (dislocations and others) etc. The equations of stress-and-strain assisted diffusion are derived from physical and thermodynamical bases. The model is very useful to evaluate the hydrogen transport by diffusion towards the potential fracture places