Grain‐Boundary Diffusion of U in Pure and Doped Uranium Carbides with Different C/U Ratios

Abstract
“The grain‐boundary diffusivity of U in UC was measured between 1200” and 2200°C in pure carbides with a wide range of C/U ratios (0.93 to 2.00) and in material doped with up to 2.4 wt% W, V, or Ta. Grain‐boundary diffusion is ∼ 103 to 105 times faster than volume diffusion, and, for UC1,0, has an activation enthalpy of 75.9 ± 9.1 kcal/mol, ∼ 55% of that for volume diffusion. In the monocarbide region, grain‐boundary mobility increases as the C/U ratio decreases and is impeded by the addition of impurities.