Meteorological Effects on the Performance of a Solid-State α-Detector Measuring Water Samples with Predefined Radon Concentration

Abstract

Livhuwani Masevhe, Risimati Dazmen Mavunda and Simon Connell

The current study validates an α-spectrometry method by assessing the functionality and response of a solid-state alpha detector to known Radon concentrations, outdoor weather conditions and varied sample volumes. These all have an influence on the sample’s behaviour inside the detector. Five samples of water with known radon concentrations (ranged from 90.66±7.20 mBq.l-1 to 314.65±24.6 mBq.l-1) were used. The experimental setup used a radon-stripping unit connected to a continuous radon monitor, which measured the 222Rn in the water by counting α-particles emitted by its progeny in secular equilibrium. The effects of meteorological parameters such as the sample concentrations and volume, internal temperature and relative humidity inside the detector were observed. The analysis of the fluctuations of temperature and relative humidity in the detection chamber were found to be in agreement with theoretical predictions and outcomes of other previous studies. To calibrate the detector of choice, the same standard samples were measured by a liquid scintillation counter (LSC) which was considered as a reference detector in the current study. The two techniques gave similar trends in the results. The LSC results appeared to be consistently lower than those of the α-spectrometry as seen by the RAD-7 device. The α-spectrometry system based on a solid-state detector had a good resolution of the peaks (FWHM of 18.61 keV and 20.93 keV) which was better than that of LSC (FWHM 166 keV) whose peaks could not be resolved. The energy-tailing of the LCS spectrum caused by Compton Scattering led to a higher count-rate of 4.11 cpm for the LSC compared to 0.71 cpm for the RAD-7. The study demonstrated that α-spectrometry method as deployed in the RAD-7 device is the most suitable equipment for the measurement of radon concentration in water because of its superior sensitivity.

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