Underwater gamma-spectrometry with HPGe and NaI(Tl) detectors

An in situ γ-spectrometer designed for underwater operations consisting of HPGe and NaI(Tl) detectors with electronics, data acquistion and processing electronics, and a supporting system consisting of a hydraulic winch with 1200 m conducting cable is described. The characteristics of the system and results obtained during operational tests and deployment in the Irish and Kara Seas are presented. The spectra measured with the HPGe detector represent the first set of high resolution sea-bed γ-spectra ever recorded in situ. Further, a possible utilisation of underwater γ-spectrometry for in situ monitoring of leakages of radionuclides from dumped or sunken nuclear objects/wastes or discharges from nuclear plants is discussed. Remote stationary γ-spectrometers operating on the sea-bed, in the open sea or in any aquatic environment with satellite data transmission would be a very efficient means of long-term monitoring. Such systems could also be equipped with other sensors, like current, temperature and salinity meters, and thus provide comprehensive information for the region.