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 quant ification of radioactive contamination in the ground using an above-ground detector. The accuracy of the technique, however, depends on having informa tion on the activity variation with depth. Three methods have previously be en proposed for deriving this information using information obtained in the field. This paper describes these methods and models used to approximate a ctivity-depth distributions and presents an experimental comparison for a r ange of sites of differing activity concentrations and sources of contamina tion. It was found that the Lead Plate Method in conjunction with a modifie d gaussian activity distribution model gave the best results estimating act ivity concentrations on average to within a factor of 1.5 of the true value .