Diffusivity of hydrogen isotopes in the alpha phase of zirconium alloys interpreted with the Einstein flux equation

Multiscale approach for determining hydrogen diffusivity in zirconium

“…Curves for the x-and y-direction overlap each other exactly, which is expected as the diffusion in basal plane is isotropic. The diffusion in the z-direction is quite close to the basal plane direction, which goes well with the hypothesis of McRae et al [24] and Christensen et al [10] who claim that bulk diffusivity of hydrogen in zirconium is isotropic. D 0 and Q for the basal plane and axis direction are presented in table 7 and show that the variation of the two directions is minimal.…”

“…The anisotropy of the diffusion of hydrogen in zirconium is open for debate where some researchers consider the axis direction (c-direction in figure 2(b)) to have a higher diffusion capacity compared to the basal plane (ab plane in figure 2(b), which is isotropic) directions. Christensen et al [10] holds the view that the diffusion of hydrogen in zirconium is isotropic, a view which is also held by McRae et al [24]. The latter authors also propose that the reason for the variation of diffusivity from previous studies is due to the driving force by the stress gradients in Onsager's flux theory.…”

“…simulations are at zero stress instead of constant volume). This takes the suggestions by McRae et al [24] to allow for stress-free diffusion.…”

HYDROGEN DIFFUSION IN HCP Zr

“…[35], are also included. Experimental results of hydrogen diffusion in αZr-2.5Nb [38], are shown in blue line.…”

“…In open triangles and stars D H from experimental data [36] and KMC results [35]. The experimental hydrogen diffusion coefficient in Zr-2.5Nb [38] (in blue solid line) is also shown. (c) Mean jump frequencies vs 1/T (K −1 ).…”