Research On Radon Gas Diffusion And Attenuation From Uranium Mill Tailings

INTRODUCTION Over the past several years, Ford, Bacon & Davis Utah Inc. (FB&DU) has been involved in research, development, and engineering activities concerning uranium mill tailings; specifically of interest in this paper are efforts in radon gas exhalation and surface flux attenuation measurements, environmental influences on radon fluxes, and basic research into radon gas behavior. Our projects have included measurements of effectiveness of specific cover material in attenuating radon surface fluxes from mill tailings, characterization of the parameters in cover materials and tailings that influence radon exhalation, long-term tailings stabilization planning, determination of the effects of moisture on radon emanation and diffusion from ores, and determinations of baseline radon fluxes. Our efforts have been sponsored by U.S. Department of Energy, the U.S. Nuclear Regulatory Commission, Tennessee Valley Authority, the commercial uranium industry, and we are presently engaged in efforts for the U.S. Bureau of Mines. Much of the material presented in this paper is taken from our published reports on radon flux attenuation and tailings stabilization (Macbeth et al., 1978; Nielson et al., 1980; Rogers et_ al., 1980; Thamer et al al., 1980). CHARACTERIZATION OF RADON GAS EXHALATION One dimensional diffusion theory based on Fick's laws is the basis for the modeling of radon gas migration through large quantities of porous tailings and cover materials applied over the large areas of tailings piles. Fick's first law relates the gaseous concentration gradients to the flux over the entire surface and defines the effective diffusion coefficient De as: [ ]