The effects of preferential flow and soil texture on risk assessments of a NORM waste disposal site.

This paper investigates the environmental fate of radionuclide decay chains (specially the (238)U and (232)Th series) being released from a conventional mining installation processing ore containing natural occurring radioactive materials (NORMs). Contaminated waste at the site is being disposed off in an industrial landfill on top of a base of earth material to ensure integrity of the deposit over relatively long geologic times (thousands of years). Brazilian regulations, like those of many other countries, require a performance assessment of the disposal facility using a leaching and off-site transport scenario. We used for this purpose the HYDRUS-1D software package to predict long-term radionuclide transport vertically through both the landfill and the underlying unsaturated zone, and then laterally in groundwater. We assumed that a downgradient well intercepting groundwater was the only source of water for a resident farmer, and that all contaminated water from the well was somehow used in the biosphere. The risk assessment was carried out for both a best-case scenario assuming equilibrium transport in a fine-textured (clay) subsurface, and a worst-case scenario involving preferential flow through a more coarse-textured subsurface. Results show that preferential flow and soil texture both can have a major effect on the results, depending upon the specific radionuclide involved.

Assessment of the mineral industry NORM/TENORM disposal in hazardous landfills.

The main objective of this paper is to describe the assessment methodology utilised in Brazil, to foresee the performance of industrial landfills to disposal solid wastes containing natural radionuclides arising from milling and metallurgical installations that process ores containing NORM. An integrated methodology is utilized and issues as risk, exposure pathways and the plausible scenarios in which the contaminant can migrate and reach the environment and human beings are addressed. A specific example of the procedure is described and results are presented for actual situations. The model consists of an engineered depository constructed of earthen materials which minimise costs and maintain integrity over long-term. In order to define the landfill characteristics and the potential consequences to the environment, an impact analysis is carried out, considering the engineering aspects of the waste deposit and the exposure pathways by which the contaminant can migrate and reach the environment and human beings. Analytical solutions are used in the computer program in order to obtain fast results.