Characterisation and suitability of a CdTe detector for strontium 90 assay in groundwater

Abstract

This paper presents a design of an in-situ detector for monitoring strontium 90 activity in groundwater at nuclear decommissioning sites. Current techniques for monitoring strontium 90 activity are lab-based and are time consuming, expensive and produce secondary waste. To alleviate these problems, a proof-of-concept detector has been developed which will be deployed in-situ, directly into groundwater boreholes. A compact detector was designed, housed in a waterproof casing and its initial performance as a strontium 90 detector in water was examined. A 10 x 10 x 1 mm cadmium telluride detector was paired with a appropriate charge sensitive amplifiers and readout systems to make a 118 x 83 x 40 mm sensor which was submersed in water. A 35.79 MBq collimated strontium 90 source was used to determine that the sensor was capable of counting beta particles from a range of 49.50 mm in water. The detector was held at a reverse bias of 80 V for 290 min, the average counts observed in 5 min intervals went from 1.32×106±1.14×103 to 1.28×106±1.13×103. However, the results presented have established a viable proof-of-concept for an in-situ detector for strontium 90 assay in groundwater.