An experimental comparison of in-situ gamma spectrometric methods for quantifying Cs-137 radioactive contamination in the ground

In-situ gamma spectrometry is a potentially powerful method for rapid quantification of radioactive contamination in the ground using an above-ground detector. The accuracy of the technique, however, depends on having information on the activity variation with depth. Three methods have previously been proposed for deriving this information using information obtained in the field. This paper describes these methods and models used to approximate activity-depth distributions and presents an experimental comparison for a range of sites of differing activity concentrations and sources of contamination. It was found that the Lead Plate Method in conjunction with a modified gaussian activity distribution model gave the best results estimating activity concentrations on average to within a factor of 1.5 of the true value.