Field Measurement of Cesium-137 in Deer

The U. S. Forest Service conducts yearly white-tailed deer hunts on the Savannah River Plant to help control the indigenous deer population. Successful hunters are permitted to retain their guarry after clearance by Forest Service personnel. To be sure that carcass radioactivity is similar to that found throughout the southeastern coastal region, each carcass is radioassayed on the spot with a single channel analyzer set to measure the cesium-137 photopeak (Figure 1). This paper describes the circuitry and performance of the instrument used for the field analyses. A sodium iodide crystal with photomultiplier tube provides electrical pulses proportional to the incident gamma radiation. An amplifier is tailored to compensate the temperature-induced gain changes of the detector system, and micropower digital logic is used to form control, pulse shaping, and scaling functions. The components are interconnected with wire-wrap techniques. The resulting instrument is compact and simple to operate, and its analyses are comparable in accuracy to laboratory analyses.