Study of self-absorption for the determination of gross alpha and beta activities in water and soil samples

Source thickness is important in determinations of gross alpha and beta activities in soil or water samples because of self-absorption and energy losses. Its influence was studied theoretically, experimentally, and with Monte Carlo simulations. No problems were found for gross beta activity determinations using sources with mass thicknesses up to 25 mg/cm2. However, to simultaneously determine gross alpha activity, the results appear to indicate that about 10 mg/cm2 should be the upper limit to avoid problems.