Potential Exposures to Radionuclides Originating from Technologically Enhanced,
Inclusive Dates: 09/25/03 12/15/05
Background - This research addressed the human health risks and environmental management issues related to the disposal of technologically enhanced, naturally occurring radioactive materials (TENORM) in municipal solid waste landfills. TENORM is generated by a number of human activities, including oil and natural gas production, drinking water treatment processes, and waste water treatment plants. The economics of TENORM disposal provide an incentive to allow its disposal in nonhazardous waste landfills that also receive municipal solid waste as opposed to special waste facilities. Published assessments of the human health risks associated with the disposal of TENORM in municipal solid waste landfills have failed to consider passive and active emissions of landfill-generated gases. Neglecting the effect of landfill gas generation on radon could create a serious flaw in these risk and exposure assessments.
Approach - The project evaluated the geochemical characteristics of TENORM that were derived from oil and gas production and from the treatment of groundwater to remove radium. This information was used to define the physical state of the waste material that would be placed in a landfill. Next, the physical and chemical processes affecting the fate and transport of radon originating from TENORM were represented in a numerical model capable of simulating 1) internal landfill gas pressures and flow rates as a result of landfill gas generation and 2) the resulting transport of radon resulting from molecular diffusion and advective transport in the landfill gas.
Accomplishments - A new numerical model (BIGEM) was developed and used to simulate radon emissions and atmospheric radon concentrations on and downwind of a landfill receiving TENORM. Two TENORM disposal scenarios were considered: 1) disposal in a discrete layer and 2) commingling of the TENORM throughout the refuse. Although other disposal scenarios are possible, these were considered to be likely bounding conditions in terms of radon emissions. Two cover construction scenarios were considered: 1) a so-called "RCRA" cover consisting of (from top to bottom) a vegetative soil layer, a gravel drainage layer, and a compacted clay layer; and 2) an alternative cover consisting only of soil. The results indicated that landfill gas generation could result in atmospheric radon concentrations exceeding ambient levels both on the landfill and several hundred meters downwind from the landfill.