Measurement of low-level radioactivity in environmental samples by gamma-ray spectrometry

Abstract

A low-level high-purity Ge detection system has been set up at about 15 m above the sea level in a normal counting room where the exposure rate is about 60 nSv h −1. A background reduction is achieved by material selection, cryostat configuration and a single lead shielding. The integrated count rate within the energy interval 70 to 3000 keV is (0.498 ± 0.001) s −1. The background in this energy range is reduced by a factor of about 100. An efficiency calibration of the detector in the energy range 50 to 2000 keV and according to the Marinelli-beaker configuration, type IEC-450, filled up with different matrices and suitable radionuclides has been performed. Field sampling of phragmites communis and juncus communis and gamma-ray measurements performed on dry matrices after treatment of the fresh material, indicate low-level contents of the nuclides 134Cs, 137Cs, 60Co, 232Th, 226Ra, 7Be and 40K distributed in the plants. It can be concluded that both selected plants are suitable bioindicators to measure the distribution of some anthropogenic and natural radionuclides in the environment.