Av. Chesnokov et al., DETERMINATION OF SURFACE-ACTIVITY AND RADIATION SPECTRUM CHARACTERISTICS INSIDE BUILDINGS BY A GAMMA-LOCATOR, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 401(2-3), 1997, pp. 414-420
A gamma locator designed to conduct contamination sun ev inside buildi
ngs connected with nuclear production is developed. The device consist
s of a detector head and a remote control unit connected with a cable
( > 150 m). Tile detector head (200 x 200 x 250 mm(3); the weight is n
early 40 kg) is a collimated scintillated gamma detector installed on
a scanning unit. The gamma detector is placed in a lead shielding with
the collimator having an entrance angle near 10 degrees. The detector
head contains a TV camera and laser distance device. The remote contr
ol unit provides operation and processing of the acquired information.
The gamma detector is based on a system of CsI(Tl) scintillators and
an Si photodiode. The detector energy resolution (nearly 9% for radiat
ion of Cs-137) provides identification of gamma radiating isotopes suc
h as Co-57, Cs-137, K-40, Co-60, I-131 and Eu-154. The gamma locator t
hreshold of determination is 250 Bq/cm(2) for a IO cm(3) scintillator
and Cs-137 radiation. The system allows one to measure the effective s
urface activity density (for Cs-137 radiation) of all building surface
s and to reconstruct an exposed dose rate distribution within the volu
me of the investigated space.