Diffusion of tritiated water in cement materials

Mobility of Tritium in Engineered and Earth Materials at the NuMIFacility, Fermilab: Progress report for work performed between June 13and September 30, 2006

“…Furuichi et al (2006) conducted experiments in a packed bed of cement particles to obtain the overall mass transfer coefficients representing adsorption of water vapor onto the concrete and the isotope exchange reaction. They obtained an isotope exchange capacity about 20% of the reported value in Numata et al (1990b). Furuichi et al (2006) noted that a smaller value may have been obtained because preferential paths for the vapor existed along the walls of the cement paste tube.…”

“…Several studies have examined tritiated water vapor interaction with concrete (Numata et al, 1990a(Numata et al, , 1990bFuruichi et al, 2006). Tritiated water vapor will exchange with water in the pores that directly contact the atmosphere, or condense in the pores if the concrete is not saturated with water.…”

“…Tritiated water will also eventually reach the pores that do not contact the atmosphere by diffusing through the concrete (Dickson, 1990). Numata et al (1990b) measured the tritium concentration in cement plugs exposed to tritiated water vapor at different times, as well as the depth profile of tritium in cement plugs. They obtained apparent diffusion coefficients by fitting the experimental data with the theoretical solution (numerically solving the one-dimensional diffusion equation).…”

Effects of water-to-cement ratio and temperature on diffusion of water in hardened cement pastes

“…In the serial model, capillary pores (region2) are the dominant diffusion pathway, and only some percent of the diffusive pore volume comprised gel pores (region 1). Previous studies [11,12] …”

“…capillary porosity). Numata et al [11] and Yamaguchi et al [12] reported that the relationship between diffusion coefficients and capillary porosity can be expressed as a power function of the volume of pores, which is a well-known empirical equation called "Archie's law". Although macroscopic approach is useful and practical with a valid empirical equation, it does not elucidate the mechanisms of diffusion processes.…”