ABSTRACT A gamma locator designed to conduct contamination surveys inside buildings connected with nuclear production has been developed. The device consists of a detector head and remote control unit connected with a cable (>100 m). The detector head (500 x 500 x 400 mm3; the weight is near 40 kg) is a collimated scintillated gamma detector installed on a scanning unit. The gamma detector is placed in lead shielding with the collimator having an entrance angle near 10º. The detector head contains a TV camera and laser distance device. The remote control unit provides operation and processing of the acquired information. The gamma detector is based on a system of scintillator CsI(Tl) and Si photodiode. The detector energy resolution (it's near 9% for radiation of Cs-137) provides identification of gamma radiating isotopes such as Co-57, Cs-137, K-40, Co-60, I-131, and Eu-154. The gamma locator threshold of determination is 250 Bq/cm2 for a 10 cm3 scintillator and Cs-137 radiation. The system allows one to measure the effective surface activity density (for Cs-137 radiation) of all building surfaces and to reconstruct the exposed dose rate distribution within the volume of investigated space.
KEYWORDS: contamination survey, gamma radiation, collimated scintillated detector, scintillator, photodiode
This paper is from the Proceedings of the HSRC/WERC Joint Conference on the Environment, May 1996, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.
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