Diffusion coefficient of hydrogen in alpha zirconium, Zircaloy-2 and Zircaloy-4

Abstract

The diffusion, coefficient of hydrogen in zirconium, Zircaloy-2 and Zircaloy-4 was determined in the temperature range, 275 °C to 700 °C. No measurable differences were found among the coefficients for the three materials, nor was there observed any effect of grain size or cold work. However, small differences were found depending on sample orientation in rolled sheet. Values of the Arrhenius constants, D 0 and Q, for the longitudinal, transverse and through-thickness directions were, respectively, 7.73 × 10 −3 cm 2 sec and 10,830 cal mole , 5.84 × 10 −3 cm 2 sec and 10,290 cal mole , 7.90 × 10 −3 cm 2 sec and 10,730 cal mole . These results, combined with an analysis of the crystallographic texture in the sheet, indicate that the ratio of the single crystal diffusion coefficients parallel and perpendicular to the “c” axis of the hexagonal structure, D ∥/ D ⊥, is greater than one, but probably not more than two.