Bentonite criticisms

In this chapter we will pay most attention to the isolation function of the innermost of the barriers, the waste matrix, and its potential interactions with the contacting water. In addition, and because of the similarities in the processes involved, we will also discuss the key processes that control the mobility of some of the critical components of waste in ground-waters. These key processes are bentonite/ groundwater interactions, which can exert a large influence on the processes controlling the master pH/pe variables, iron corrosion processes responsible for poising the redox potential of the system and the interactions between the waste matrix itself and the contacting fluids, which produce radiolysis reaction processes. 

Geothermal cements are also employed to fix the steel wellbore casing in place and tie it to the surrounding rock (8). These are prepared as slurries of Portland cement (qv) in water and pumped into place. Additional components such as silica flour, perlite, and bentonite clay are often added to modify the flow properties and stability of the cement, and a retarder is usually added to the mixture to assure that the cement does not set up prematurely. Cements must bond well to both steel and rock, be noncorrosive, and water impermeable after setting. In hydrothermal applications, temperature stability is critical. Temperature cycling of wellbores as a result of an intermittent production schedule can cause rupture of the cement, leading to movement and, ultimately, failure of the wellbore casing. 

Bourg, L,C., Bourg, A. C. M., and Sposito, G. (2003). Modeling diffusion and adsorption in compacted bentonite a critical review. J. Contam, Hydrol, 61, 293-302. 

Figure 3 summarizes the continuous underground wall construction method. In this method, bentonite or a stabilizing solution that contains a water-soluble polymer at critical micellar concentration (CMC) is added when the work is being done underground. These materials will degrade... 

Figure 10.15 Effect of bubbling rate on critical flux of bentonite suspension with submerged...

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