Demonstration of lightweight gamma spectrometry systems in urban environments

Abstract

Urban areas present highly complex radiation environments; with small scale features resulting from different construction materials, topographic effects and potential anthropogenic inputs from past industrial activity or other sources. Mapping of the radiation fields in urban areas allows a detailed assessment of exposure pathways for the people who live and work there, as well as locating discrete sources of activity that may warrant removal to mitigate dose to the general public. These areas also present access difficulties for radiometric mapping using vehicles or aircraft. A lightweight portable gamma spectrometry system has been used to survey sites in the vicinity of Glasgow to demonstrate the possibilities of radiometric mapping of urban areas, and to investigate the complex radiometric features such areas present. Variations in natural activity due to construction materials have been described, the presence of 137 Cs used to identify relatively undisturbed ground, and a previously unknown NORM feature identified. The effect of topographic enclosure on measurements of activity concentration has been quantified.The portable system is compared with the outputs that might be expected from larger vehicular or airborne systems. For large areas airborne surveys are the most cost effective approach, but provide limited spatial resolution, vehicular surveys can provide sparse exploratory data rapidly or detailed mapping of open areas where off-road access is possible. Backpack systems are ideally suited to detailed surveys of small areas, especially where vehicular access is difficult.

Operator related attenuation effects in radiometric surveys

“…Measurements with and without human operators in radiation fields dominated by 137 Cs and 134 Cs were conducted at a ground sampled calibration site at Fukushima University (Sanderson et al 2013). These measurements are shown in Figure 5, and give reductions in the full energy intensities for 134 Cs and 137 Cs of 25-30%, which are consistent with the results of the numerical model developed in this study, and with the experimental values obtained from the substitute experimental geometry.…”

“…These measurements are shown in Figure 5, and give reductions in the full energy intensities for 134 Cs and 137 Cs of 25-30%, which are consistent with the results of the numerical model developed in this study, and with the experimental values obtained from the substitute experimental geometry. Comparisons between measurements with the backpack system and data from soil samples at the ECCOMAGS calibration sites (Sanderson et al 2004) close to the Solway Firth in Scotland (Cresswell et al 2013) have also shown reductions of 20% to 40% between the field measurements and samples. The magnitude of the observed reductions is compatible with the estimate from the model presented here.…”

Gamma-ray Spectrometry in Geothermal Exploration: State of the Art Techniques

“…Typically in areas of lower radioactivity rock, longer sample times are needed for suitably accurate results [22]. An alternative approach used by some surveys is to monitor continuously then integrate the count times in intervals, e.g., every 5-10 s [50]. Rock and soil samples can also be collected during these in-situ surveys, to compare with the in-situ gamma results or to conduct more general rock mineral analysis [32,33,44,51] and be able to quantify near surface geometrical effects [52].…”

“…Indeed some designs have been specifically mounted on backpacks and readings taken at automatic intervals [32,50]. Such portable spectrometers have precisions of approximately 0.1%-0.14% K, 0.6-0.8 ppm eU, and 0.6-1.5 ppm eTh [42,53].…”

“…The analyser measures 1024 different channels between 0.03 and 3 MeV. The surveyor weighs 1.8 kg and is compact and lightweight enough for it to be readily carried in a small rucksack [50]which is important in the highly mountainous terrains which granite often gives rise to. Seven plutons were visited in total, six of the plutons in the Grampian region of Scotland; Monadhliath, Cairngorm, Lochnagar, Ballater, Grantown, and Strathspey, and one pluton on the Isle of Mull (the Ross of Mull granite).…”