Abstract
This paper presents the results of an attenuation model for remote depth estimation of buried radioactive wastes using a Cadmium Zinc Telluride (CZT) detector. Previous research using an organic liquid scintillator detector system showed that the model is able to estimate the depth of a 329-kBq Cs-137 radioactive source buried up to 12 cm in sand with an average count rate of 100 cps. The results presented in this paper showed that the use of the CZT detector extended the maximum detectable depth of the same radioactive source to 18 cm in sand with a significantly lower average count rate of 14 cps. Furthermore, the model also successfully estimated the depth of a 9-kBq Co-60 source buried up to 3 cm in sand. This confirms that this remote depth estimation method can be used with other radionuclides and wastes with very low activity. Finally, the paper proposes a performance parameter for evaluating radiation detection systems that implement this remote depth estimation method.
Highlights
Wastes generated during the nuclear fuel cycle can end up in the soil, resulting in large-scale land contamination
Co-60 source buried up to 3 cm in sand. This confirms that this remote depth estimation method can be used with other radionuclides and wastes with very low activity
This maximum detectable depth of 3 cm achieved for 9-kBq Co-60 source buried in sand is a significant improvement over the technique reported in [12], which achieved a similar maximum depth limit for a 40-kBq Co-60 source buried in sand
Summary
Wastes generated during the nuclear fuel cycle can end up in the soil, resulting in large-scale land contamination This is the case in the beaches of Dounreay in Northern Scotland where wide-spread radioactive soil contamination has been reported [1,2]. This was caused by the so-called Dounreay particles resulting from the processing of the fuels from the Material Test Reactor at the Dounreay nuclear facility. The characterisation of these subsurface wastes has continued to be a major nuclear decommissioning challenge [6] This is mainly because of the difficulty in estimating the depth of penetration of these contaminants without having recourse to destructive methods such as logging or core sampling [7,8]. Reported non-intrusive depth estimation methods for such wastes are either based on empirical models [9,10] or are limited to a maximum depth of 3 cm [11,12]
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