Radon corrections in geophysical surveys with a split γ-ray detector

Mijland, M.K. (2023) Radon corrections in geophysical surveys with a split γ-ray detector. Master's Thesis / Essay, Physics.

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Abstract

This thesis presents a research project conducted at Medusa Radiometrics, a company producing specialised γ-spectrometers for geophysics. These spectrometers are used as survey tools to determine concentrations of naturally occurring radionuclides, including 40K, 232Th, and 238U, in soil. The concentrations of these radionuclides serve as predictors of other soil qualities, such as sediment texture, nutrient content and more. The presence of 222Rn, a radioactive noble gas originating from the decay chain of 238U, in the atmosphere can lead to erroneous measurements of elevated 238U concentrations in the soil due to the similar γ-ray emissions. This research focused on developing a novel method using a split γ-ray detector with directional sensitivity to distinguish atmospheric 222Rn from 238U in the ground. The directional dependence was characterized by assessing the detector’s response at various angles, approximating the change with a cosine function, which turned out to be a good approximation. The method’s effectiveness was evaluated by comparing its 222Rn and 238U measurements with those from the Lutjewad atmospheric measurement station. The results showed that the 238U concentration determined by this method was nearly independent of atmospheric 222Rn concentration. Although the measured 222Rn concentration was higher than that of Lutjewad, the two concentrations were correlated with a correlation coefficient of r = 0.64, data smoothing was able to improve this to r = 0.88.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Hoekstra, R.A. and Graaf, E.R. van der
Degree programme:	Physics
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	06 Jul 2023 12:13
Last Modified:	19 Jul 2023 06:41
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/30058

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