The scanning remote gamma-spectrometer determination of the replacement of the radioactive source

The remote scanning gamma-spectrometer for radiation control at the nuclear power plants and the plants connected with the nuclear production was developed. The device consists of the detector block and the control unit connected by a cable (>100 m). The detector part (500×500×400 mm³, the weight is about 30 kg) is the collimated gamma detector installed at the scanning unit. The gamma detector is place into the lead shielding with collimator having entrance angle near 10°. The control unit (based on the IBM PC) provided the control and processing of the acquiring information. As a detector the system scintillator CsI(Tl) and Si photodiode is used. Its energy resolution for the radiation of Cs-137 (662 keV) is near 8%. The range of registering energy of gamma quanta is 100 keV-3 MeV. the device allows to measure the effective surface density of activity of the objects and the premises and also to reconstruct the distribution of the exposure dose rate within the volume of investigated space. The developed system was used for measuring the distribution of contamination levels within the machine premise of the 4-th unit after the accident at Chernobyl Nuclear Power Plant