Diffusion of tritiated water in cement materials

Abstract

The diffusion of airborne tritiated water into cement materials is discussed in terms of unsteady state adsorption and depth profile experiments. Consistent apparent diffusion coefficients of tritiated water in cement materials were obtained from different experiments. From the comparison between experimental results, Raoult's law was found to be applicable to the vapor-liquid equilibrium between tritiated water vapor and liquid water at the surface. The results of depth profile experiments suggested that there were two different diffusion processes in cement materials; one is a fast diffusion process of a relatively small portion, and the other is a slow process having higher capacity. From the permeation experiments, in which liquid water was used, the intrinsic diffusion coefficient was observed to be a function of the porosity and found to increase from 3.19×10 −12 to 11.3×10 −12 m 2/s with a porosity increase from 0.07 to 0.28.