Movement of radon in overburden

Abstract

An analytical solution for simple one‐dimensional geometry establishes the basic theory of the movement of [Formula: see text] (radon) in overburden, involving diffusion and convection. The computer‐adapted finite‐difference method is then used to determine radon concentrations for the following more complex configurations: a two‐dimensional source, a vertical fault, a three‐dimensional source, and multilayered overburden. The key parameters are the radon concentration at the source, the diffusion coefficient of the overburden, and the geometry. This analysis indicates that if diffusion is the only transport process considered, the maximum depth at which uranium mineralization can be detected by the usual types of field equipment is limited to a few tens of meters. However, if convective transfer is also considered, radon attenuation is significantly decreased, e.g., by as much as a factor of 800 for a one‐dimensional configuration considered. It appears that an upward velocity component for the movement of radon, or geochemical dispersion of uranium and radium, are needed for long‐distance detection of uranium mineralization.

Advances in soil gas geochemical exploration for natural resources: Some current examples and practices

“…Plots for CO2 in soil gas are shown in Figure 8 Informative reviews and case histories of radon use have been published fairly recently, as the technique gained renewed interest from the energy-related research of the 1970's [Tanner, 1978;Rubin, 1978;Soonawala and Telford, 1980;Kraner et al, 1964]. The use of helium in exploration is a recent development, and case histories are few but informative [Reimer et al, 1970;Dyck, 1976 Previous studies had yielded information on the role in the formation of the uranium deposits [Bowles and groundwater chemistry, and tritium data provided infor-Braddock, 1963; Bowles, 1968].…”

Radon release from underground strata to the surface and uniaxial compressive test of rock samples

“…Due to its unique physical and chemical properties, radon gas migration is related to various factors, and no agreement has been reached on the mechanism and principles underlying this process. Various studies have proposed different mechanisms of radon gas migration from underground strata to the surface (e.g., Wilkening and Watkins, 1976;Fleischer and Mogro-Campero, 1979;Soonawala and Telford, 1980;Varhegyi et al, 1992;Folger et al, 1997;Wattananikorn et al, 1998;Cameron et al, 2002;Le and Wang, 2006), including diffusion, convection, pore fluid, advection, and micro-bubbles as carriers, relay transmission, stress compression, and cluster theory. Nevertheless, different groups have uniformly reported that radon gas can migrate to the ground via micro-cracks and pores in the underground strata.…”

Geophysical investigations for the characterization of fractured rock aquifers in Itu, SE Brazil

“…The fresh water that percolates into the rock fractures carries the radioactive gas that can travel several meters before escaping through some fracture, towards the surface, even considering the small half-life of this gas. The escape to the atmosphere occurs through the transport mechanism known as diffusion (Soonawala and Telford, 1980). Measurements were made at 5-m intervals along a line (Fig.…”