INTEGRATED RADON MONITORING BY THE DIFFUSIONAL BARRIER TECHNIQUE

In many searches for uranium in the earth by mapping of 222Rn it is difficult or inconvenient to drill conventional holes approximately 60 cm in depth. A simpler and more economical method is to use a mat to create a diffusional barrier to radon at the surface and monitor radon beneath the mat. Theory gives the effective depth to which radon is sampled as a function of mat radius, the relation being linear for radii that are small relative to the mean diffusion distance of the radon. Calculations based on this theory indicate what barrier properties are needed. For solubilities of radon that are below 100, a polyethylene mat thickness of at least 50 mum gives a barrier efficiency of more than 90%. Field experiments at two sites demonstrate that the predicted variation with mat radius occurs and that measurements are reproducible.-Authors