masterstheses by Rikus le Roux
inproceedings by Rikus le Roux
articles by Rikus le Roux
phdtheses by Rikus le Roux
Papers by Rikus le Roux
Journal of food composition and analysis, Jul 1, 2024
Applied Radiation and Isotopes, Mar 1, 2022
Gamma-ray detection systems are exposed to extreme environments during in situ measurements and t... more Gamma-ray detection systems are exposed to extreme environments during in situ measurements and the NaI(TI)-detectors in these systems are frequently subjected to significant temperature fluctuations. Several elements within these detectors are sensitive to temperature deviations, which ultimately causes a drift in gamma-ray spectra. This study aimed to determine the relationship between temperature deviation and spectrum drift and found a linear relationship over a wide range of energies. It was found that an increase in the detector temperature shifts the gamma-ray spectrum to lower channels, whereas a decrease in the detector temperature shifts the spectrum to higher channels. Using this information, a novel drift correction method based on the Gaussian distribution of the 1460 keV gamma-peak of 40K was developed. Dividing the peak into five regions of interest (ROI), a weighted gain correction factor is calculated based on the comparative skewness of the measured data and the sensitivity of the drift. The detector gain is then adjusted by the same factor to correct the drift in gamma-spectrum. This method was first tested in a simulated in situ environment, followed by in situ measurements along a beach. As expected, the gain adjustments followed the trend in detector temperature. The corrected counts in each of the five bins also presented good results and a close fit to the Gaussian distribution.
Arabian Journal of Geosciences
There has been a growing interest in the effect of radon gas on humans visiting caves. A radon su... more There has been a growing interest in the effect of radon gas on humans visiting caves. A radon survey was consequently done in the Sudwala tourist cave close to Nelspruit in the eastern part of South Africa to determine the radon exposure of tourists and guides. The Sudwala cave, which evolved in karst geology, is a popular tourist destination. Twenty-eight electret ion chambers were placed in various locations throughout the cave for a period of 24 h. Radon concentrations varied between a minimum of 255 Bq/m3 and a maximum of 1822 Bq/m3 with a geometric mean of 750 Bq/m3. The radon levels were found to be relatively stable up to 600 m from the entrance, after which they sharply increased. This suggests that different processes disperse radon in the initial and deeper parts of the cave. It was concluded that this is the result of natural cave ventilation which is caused by changes in ambient barometric pressure. Despite the measured level being higher than the World Health Organizat...
Journal of Radioanalytical and Nuclear Chemistry
Health Physics, 2022
South Africa has rich coal deposits concentrated in the northeast of the country, and as a result... more South Africa has rich coal deposits concentrated in the northeast of the country, and as a result, most of the country’s coal mining is located in this region. Two of the principal coalfields exploited are the Witbank and Highveld coalfields, located in the Mpumalanga province. Coal contains trace quantities of the naturally occurring radionuclides whose mass concentration can be enhanced by anthropogenic activity. The radioactive fallout from these activities could lead to elevated radon concentrations indoors. Two towns, Secunda and eMalahleni, were identified due to their proximity to coal-based industries. A previous study investigated whether these industries caused elevated radon levels in Secunda homes but found a lower-than-expected average concentration of 76.4 ± 7.6 Bq m−3. This was attributed to either the prevailing wind depositing the radioactive fallout to neighboring towns, such as eMalahleni, or the type of industrial activity. This paper builds on this study by inve...
Health Physics, 2021
Secunda is a town built amid the coalfields of the Mpumalanga province of South Africa. Surroundi... more Secunda is a town built amid the coalfields of the Mpumalanga province of South Africa. Surrounding the town are 11 coal-fired plants (CFPs) contributing around 59% of the country’s energy needs. It is also home to Sasol Synfuels, which produces synthetic gas through coal gasification and natural gas reforming. Coal, like most materials found in nature, contains trace elements of the naturally occurring primordial radionuclides 40K, 238U, 232Th, and their decay products. The milling and combustion of coal in a CFP increases the mass concentration of these trace elements, and the residuals end up on ash heaps as fly ash, bottom ash, and boiler slag. A small percentage of fly ash also ends up in the atmosphere. This paper sets out to determine the anthropogenic impact of the industrial activity on indoor radon in the town of Secunda in the Mpumalanga region of South Africa. Measurements were done in 37 homes during July when higher indoor radon levels are expected due to homes typical...
Applied Radiation and Isotopes, 2021
Gamma-ray detection systems are exposed to extreme environments during in situ measurements and t... more Gamma-ray detection systems are exposed to extreme environments during in situ measurements and the NaI(TI)-detectors in these systems are frequently subjected to significant temperature fluctuations. Several elements within these detectors are sensitive to temperature deviations, which ultimately causes a drift in gamma-ray spectra. This study aimed to determine the relationship between temperature deviation and spectrum drift and found a linear relationship over a wide range of energies. It was found that an increase in the detector temperature shifts the gamma-ray spectrum to lower channels, whereas a decrease in the detector temperature shifts the spectrum to higher channels. Using this information, a novel drift correction method based on the Gaussian distribution of the 1460 keV gamma-peak of 40K was developed. Dividing the peak into five regions of interest (ROI), a weighted gain correction factor is calculated based on the comparative skewness of the measured data and the sensitivity of the drift. The detector gain is then adjusted by the same factor to correct the drift in gamma-spectrum. This method was first tested in a simulated in situ environment, followed by in situ measurements along a beach. As expected, the gain adjustments followed the trend in detector temperature. The corrected counts in each of the five bins also presented good results and a close fit to the Gaussian distribution.
PhD (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015
Radiation Protection Dosimetry, 2020
Granite commonly contains high concentrations of uranium, with consequent high exhalation of rado... more Granite commonly contains high concentrations of uranium, with consequent high exhalation of radon. The geology of the West Coast peninsula of South Africa is dominated by granite, and a recent article predicted potentially high indoor radon concentrations in this region’s two largest towns, Vredenburg and Saldanha. This research aimed to measure indoor radon levels in these towns. Measurements were first done for a minimum of 3 d during warmer months, with houses typically being more ventilated. Thirty-four homes in Vredenburg and 27 in Saldanha were measured, and the average indoor radon determined to be 40 and 58 Bq m−3, respectively. The measurements were then repeated during the colder months, and an increase in average radon concentration of 173 Bq m−3 for Saldanha and 153 Bq m−3 for Vredenburg was found. The granite geology and lifestyle of occupants during the colder months seem to contribute towards elevated levels of indoor radon concentrations.
South African Computer Journal, 2019
The dynamic reconfiguration of an FPGA has many advantages, but the overhead from the process red... more The dynamic reconfiguration of an FPGA has many advantages, but the overhead from the process reduces the functional density of applications. Functional density is an indication of the composite benefits a reconfigured application obtains above its generic counterpart and measures the computational throughput per unit hardware resources. Typically, only quasi-static applications obtain a functional density advantage by dynamically reconfiguring its parameters. Contributing to the functional density reduction of applications with tight time constraints is the overhead to generate a new configuration, and the time it takes to load it onto the device. Normally these applications have to reuse their hardware numerous times between configurations before obtaining a functional density advantage. The most promising reconfiguration method to improve functional density with minimal hardware reuse was one that extracts certain characteristics from the bitstream and then implements a bitstream...
Journal of Radiation Research and Applied Sciences, 2019
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masterstheses by Rikus le Roux
inproceedings by Rikus le Roux
articles by Rikus le Roux
phdtheses by Rikus le Roux
Papers by Rikus le Roux