Retardation of Tritium and Cesium in Brine‐Saturated Mudstone, Halite, and Carbonate Porous Media

Abstract

Batch and column sorption/desorption experiments were conducted to quantify the retardation of tritium and cesium in brine‐saturated mudstone, halite, and carbonate rocks from Palo Duro Basin, Texas, one of the three sites originally nominated by the U.S. Department of Energy for construction of a civilian nuclear waste repository. Retardation factors (R) were determined using six different methods, including batch sorption equilibrium, fitting of two transport models, breakthrough area integration, and pore volume displacement at C/C0= 0.5, for both the sorption and desorption parts of the breakthrough curves. The breakthrough area integration method resulted in R values consistently lower than the other methods, which were in reasonable agreement. The data indicated very small retardation for cesium in all the media, except mudstone, which exhibited moderate retardation (R < 3.5). It was shown that the small extent of cesium retardation was most possibly caused by the strong competition for sorption sites of the components of the saturated brine, which were several orders of magnitude higher in concentration than cesium. Tritium breakthrough curves for all media tested were accurately simulated by the local equilibrium advection‐dispersion model (model I). With the exception of mudstone, cesium breakthrough curves were also adequately simulated by model I. The cesium breakthrough curve for mudstone exhibited considerable tailing on the desorption side of the curve, which was best described by the two‐site kinetic sorption model II. This was attributed to chemical nonequilibrium (two types of sorption sites). Predicted breakthrough curves for cesium using model I were in good to reasonable agreement with measured breakthrough curves.

The concept of a sorption chemical barrier for improving effectiveness of landfill liners

“…According to Table 1, an upper boundary concentration of 10 mg L -1 for a period of 2 years was assumed. Hydrodynamic dispersion coefficients were determined from a set of generalised correlations that account for the combined effect of molecular diffusion and mechanical dispersion (Bear 1979;Voudrias et al 1993). The hydrodynamic dispersion coefficient accounts for the product of the dispersivity and velocity plus the diffusivity in the porous medium of the liner [5].…”

Experimental Validation of Retardation of Tritium Migration in the Chinese Loess Media

“…Van Loon and Jakob (2005) accounted tritium adsorption on clay minerals by a small but non-zero K d value on the order of 10 −5 m 3 kg −1 , which was found to reproduce the data with acceptable precision. Using batch and column experiments to quantify the retardation of tritium in brine-saturated mudstone, halite, and carbonate rocks from the Palo Duro Basin in Texas, Voudrias et al (1993) concluded that the retardation factor (R d ) of tritium was 1.0-1.1. Otherwise, adsorptions of both gaseous 3 H by soil (Garland and Cox 1980) and liquid 3 H (existing as 3 H 2 O form) by cement (Ono et al 1995) have been reported.…”

Detection of tritium sorption on four soil materials

“…In migration experiments with 32 P and 3 H, Gupta et al (1999) observed that the migrating velocity of 32 P was larger than that of 3 H by a factor of 4 .Van Loon and Jakob (2005) accounted for tritium sorption on clay minerals by a small but nonzero value (0.01 mL/g) of distribution coefficient (K d ). Using batch and column experiments to quantify the retardation of tritium in brinesaturated mudstone, halite, and carbonate rocks from the Palo Duro Basin in Texas, Voudrias et al (1993) concluded that the retardation factor (R d ) of tritium was 1.0e1.1, reflecting the small, but nonnegligible, sorption of tritium. The R d value would be 1 if there is no sorption (i.e., K d value of zero) for tritium.…”