title: The effects of preferential flow and soil texture on risk assessments of a NORM waste disposal site.
abstract: 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.
authors.affiliation: Brazilian Nuclear Energy Commission, CNEN, Rua General Severiano 90, Rio de Janeiro, Brazil.
authors.forename: E M
authors.initials: EM
authors.lastname: Pontedeiro
authors.forename: M Th
authors.initials: MT
authors.lastname: van Genuchten
authors.forename: R M
authors.initials: RM
authors.lastname: Cotta
authors.forename: J
authors.initials: J
authors.lastname: Simunek
mesh_terms: D008906:Mining; D011868:Radioisotopes; D012037:Refuse Disposal; D018570:Risk Assessment; D012987:Soil
chemical_list: D011868:Radioisotopes; D012987:Soil