A study on radon diffusion and exhalation of soils under transient conditions: Theoretical and experimental approach

A practical method is presented for the short-time transient-diffusion measurement of radon flux and concen-tration in large soil samples (porous materials) and the radon diffusion coefficients. An experimental apparatus was designed and tested to verify the theoretical validity and technical accuracy of the presented technique by the transient-diffusion method. The concentration data measured inside the accumulator determines the radon flux for various soil thicknesses. Good agreement was observed between values of the measured radon flux and those expected by the theoretical model based on the diffusion theory. The relative standard deviation of 16% was obtained in measurements with dry soil by the short-time transient-diffusion method. Diffusion coefficients of soils were derived from the curve fit of measured flux data to the theoretical expression based on Fick's law. Comparing the measured diffusion coefficient and that obtained by empirical correlation provides a good agreement with a relative uncertainty of 11%. The present transient-diffusion measurement technique could provide low cost, good precision, short time experiment, no radioactive waste (residue) generation, and good validity.