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Title: An Integral Transform Application To Environmental Impact Assessment Of Uranium Mining Waste Disposal

Author
item COTTA, RENATO - UNIV OF RIO
item NAVEIRA, CAROLINA - UNIV OF RIO
item Van Genuchten, Martinus
item UNGS, MICHAEL - TETRA TECH INC

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2007
Publication Date: 11/9/2007
Citation: Cotta, R.M., Naveira, C.M., Van Genuchten, M.T., Ungs, M.J. 2007. An Integral Transform Application To Environmental Impact Assessment Of Uranium Mining Waste Disposal. Meeting Proceedings. 19th Int'l Congress of the Brazilian Society of Mechanical Engineering, COBEM 2007, Nov. 5-9, 2007, Brasilia, DF, Brazil, 11p. (CD-ROM)

Interpretive Summary: Regulatory bodies in most countries require a detailed environmental impact assessment when considering the disposal of solid and liquid wastes from industrial activities, including those involving radioactive materials. The assessment typically includes an analysis of the transport of contaminants released from the wastes through engineered barriers into underlying soil and groundwater systems. When radionuclides are present, one must solve the coupled system of transport equations for each species in the radionuclide decay chain for the specific hydrologic and geochemical conditions of the site being considered. In this paper we used a very flexible hybrid numerical-analytical approach that offers user-controlled accuracy and more efficient computational performance for a wide variety of problems in fluid flow, contaminant transport and heat transfer. The approach, referred to as the Generalized Integral Transform Technique (GITT) was used to solve the set of advection-diffusion equations describing the migration of radioactive decay chains in the subsurface. The solution was applied to four different scenarios for the transport of radioactive contaminants from liquid waste ponds at a uranium mining facility in Brazil. Results illustrate the considerable power of hybrid numerical-analytical solutions for evaluating relatively complex subsurface contaminant transport problems, in this case the transport of radioactive contaminant decay chains in coupled saturated and unsaturated soil-aquifer systems. The GITT approach produced analytical expressions for the concentration distributions versus distance, and analytical or numerical estimates of the concentration as a function of time. The method appears very attractive for simulating a broad range of contaminant transport problems in soils and groundwater.

Technical Abstract: In this paper we present hybrid numerical-analytical solutions for the transport of radioactive contaminant chains in the subsurface for environmental impact assessment related problems. The proposed model involves the advective-dispersive transport of multiple radionuclide species within separate but coupled saturated and unsaturated soil domains. The resulting partial differential equations are solved using the generalized integral transform technique (GITT) to yield analytical expressions for the concentration distributions versus distance, and analytical or numerical solutions as a function of time. The potential of the hybrid modeling approach is illustrated by means of an environmental impact assessment of an uranium mine liquid waste pond in Caetité, Brazil.