IN-SITU SPECTROMETRY OF CS-137 IN THE SOIL BY AN UNFOLDING METHOD

The approach is based on in-situ measurements performed with a portabl e high-resolution germanium gamma-spectrometer and on calculations of the depth distribution by an unfolding method. To unfold the depht dis tribution of Cs-137 concentration in soil four detector responses and the iterative procedure SAND II were used. The detector responses cons ist of the responses to primary 662 keV photons and to photons scatter ed in soil with the rest energies of 620-655 keV. ?he detector is used with and without collimator. The method is sufficiently sensitive for measurements of Cs-137 concentration in son 10 years after the Cherno byl accident. The results are compared to laboratory analyses of colle cted soil samples and with a standard method of in-situ spectrometry.