CsI(Tl) with Photodiodes for Identifying Subsurface Radionuclide Contamination

Abstract

A cylindrical (15 x 61 mm) CsI(Tl) scintillation detector with two side-mounted photodiodes has been developed to collect spectral gamma-ray data in subsurface contaminated formations at the U.S. Department of Energy's Hanford Site. It operates inside small-diameter, thick-wall steel pipes pushed into the ground to depths up to 20 m by a cone penetrometer system. The detector provides a rugged, efficient, magnetic-field-insensitive means for identifying gamma-ray-emitting contaminants (mainly 137Cs and 60Co). Mounting two 3 x 30-mm photodiodes end-to-end on a flat area along the detector's side provides efficient light collection over the length of the detector. © 1995 IEEE.