Waste rock interactions

Waste-Rock Interactions. Under the heading of waste-rock... 

However, the contributions of sulfate, acid and metals from ground and surface waters that interact with the numerous tailings and waste rock dumps located... 

Reconnaissance studies have shown that surface waters originating from waste rock and tailings dumps are typically characterized by low pH, high sulfate levels and variable metal contents. Consequently, the aim of this study is to investigate the nature of ground water interactions with... 

The near field of the repository includes the engineered barrier system (EBS, i.e., canister and buffer) and the waste form. Also included in the near field is the interface between the buffer and the host rock, denoted as excavation disturbed zone (EDZ). In terms of waste/water interactions, the geochemical evolution of the near field is essential as it controls the composition of the fluids that will eventually contact the waste. 

Data from in-situ leach mining and restoration of roll-front uranium deposits also provide information on the potential mobility of the waste if oxidizing ground water should enter the repository. Uranium solids probably will be initially very soluble in carbonate ground water however, as reducing conditions are re-established through water/rock interactions, the uranium will reprecipitate and the amount of uranium in solution will again equilibrate with the reduced uranium minerals ... 

The mode of fluid flow in the aerated zone may be changed by the hydraulic aspects of fluid waste disposal. Constant release of large amounts of fluids may cause a local rise in the hydraulic head. Coupled with chemical fluid-rock interactions, this may form new high-conducting conduits that can lead the contaminants directly into the saturated zone. In other cases, fine particles that come with the contaminating fluids can clog pores in the aerated zone and reduce through-flow. 

In sum, there are four major sources of soluble salts in river basins (i) meteoric salts (ii) salts derived from water-rock interaction (e.g., dissolution of evaporitic rocks) (iii) salts derived from remnants of formation water entrapped in the basin and (iv) anthropogenic salts (e.g., waste-water effluents). Meteoric salts are concentrated via in-stream net evaporation and evapotransprra-tion along the river flow. In addition, meteoric salts can be recycled through irrigation in the watershed and development of saline agricultural drainage water that flows to the river. 

Gardiner, M.A. and Myers, J., 1992. Geochemical modeling of the deep injection well disposal of acid wastes into a Permian aquifer/aquitard system in Texas, USA, in Yousif K. Kharaka and Ann S. Maest, eds, Proceedings - International Symposium on Water-Rock Interaction, vol. 7, pp. 385-388. 

Metcalfe, R., Kunimaru, T., Llama, K., Amano, K., Iwatsuki, T., Milodowski, A.E. Gillespie, M R. 2001. Water-rock interaction around a fault implications for waste disposal. Water-Rock Interaction 1 2 1343-1346. 

Eikenberg, j. Lichtner, P. C. 1992. Propagation of hyperalkaline cement pore waters into the geologic barrier surrounding a radioactive waste repository. In Kharaka, Y. K. Maest, A. S. (eds) Water-Rock Interaction. Balkema, Rotterdam, 377-380. 

Chemical reactions may result from interactions among and between the three phases of matter solid, liquid, and gas. The major interactions that occur in the deep-well environment are those between different liquids (injected waste with reservoir fluids) and those between liquids and solids (injected wastes and reservoir fluids with reservoir rock). Although gases may exist, they are usually dissolved in liquid at normal deep-well pressures. 

Waste-brine mixture interactions with rock... 

Microbiological interactions with the waste/brine/rock system... 

Each interaction involves numerous chemical processes. The dominance of a specific interaction depends on the type of waste, the characteristics of the brine and rock in the reservoir, and environmental conditions. Table 20.14 describes some of the more common processes that may result in incompatibility. 

The geochemical interactions possible between an injected waste and the reservoir rock and its associated fluids can be quite complex. Thus a combination of computer modeling, laboratory experimentation, and field observation will inevitably be necessary to satisfy current regulatory requirements for a geochemical no-migration deep-well injection. This section covers the computer methods and models available for predicting geochemical fate. 

Spycher, N. and Larkin, R.S., Investigation of chemical interactions between waste, native fluid, and host rock during deep well injection, in Underground Injection Science and Technology, Tsang, C.F. and Apps, J.A., Eds., Elsevier, New York, 2007. 

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