Browsing by Author "Lindsay, Robert"

Now showing 1 - 7 of 7
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    High resolution gamma-spectroscopy of environmental samples
    (University of the Western Cape, 2019) Rapetsoa, Metsi Monnicca; Lindsay, Robert
    In this study, a comparison has been made between the available commercial software package Genie 2000 developed by Canberra and Virtual Gamma Spectroscopy Laboratory (VGSL) developed by the Radionuclide Development Unit of the International Data Centre of the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO) to provide quality assessment of the data delivered by eighty (80) international monitoring stations distributed around the world to monitor nuclide emissions after an illegal nuclear weapon test, either in the atmosphere, under water or underground. The lessons learned from the Proficiency Test Exercises (PTEs) will be applied to NORM nuclide analyses of environmental samples. Results provided are based on three (3) IAEA reference materials: stream sediments, milk powder, and soil. These samples contain decay products of uranium and thorium, which produce multiple gamma-rays, and thus a High Purity Germanium detector (HPGe) will be used. The study has been conducted in the South African CTBTO laboratory (ZAL14) situated at the South African Nuclear Energy Corporation SOC Ltd. The laboratory is equipped with two ultra-low background gamma-spectrometry systems accredited according to world-class standards. The CTBTO PTEs spectra and IAEA certified samples have been analyzed looking at a variety of parameter settings including sum-coincidence and matrix-dependent self-absorption using both software mentioned. Optimization of various parameters has been done by gamma-ray spectra used in the CTBTO proficiency tests over the past decade.
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    Modelling and measurement of radon diffusion through soil application on mine tailings dams.
    (University of Western Cape, 2004) Speelman, Wilcot John; Lindsay, Robert
    Radon (222Rn) has been identified as an important factor that could result in a health hazard by studies all around the world. The health risks can be minimised by preventive measures where radon is highly concentrated as in some mines and homes. A study in the diffusion of the inert gas, will give us a better understanding of its possible pathways through soil into the air surrounding mine dumps where the radon releases can become hazardous. Measuring and modelling the radon concentrations in the mine dump soil, can help to deduce the radon flux to identify the problem areas for rehabilitation especially in the cases of gold and uranium mine tailings.
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    Nanoscience teaching and research program in South Africa
    (Frontiers Media SA, 2024) Lindsay, Robert; Nel, Janske
    Since 2012, the national nanoscience teaching and training platform (NNPTTP), funded by the South African department of science and innovation (DSI), has been responsible for overseeing Africa’s first-ever master’s in nanoscience program. For over a decade, the NNPTTP has seen the cooperation of four partner universities across South Africa, namely, the university of Johannesburg (UJ), University of the Free State (UFS), University of the Western Cape (UWC), and Nelson Mandela university (NMU), culminating in over 250 graduates trained in either nanophysics, nanochemistry, or nanobiology. Originally established to train professionals for a nanotechnology-based industry, both in South Africa and internationally, the program and platform has evolved into a testament to scientific collaboration. This paper discusses the program’s framework, successes and challenges, related research, and future plans.
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    Pre-equilibrium cross section calculations with a realistic effective nucleon-nucleon interaction
    (University of the Western Cape, 1995) Karriem, Zainuddin; Lindsay, Robert
    The principle aim of this work is to improve the way in which pre-equilibrium double differential cross-sections are currently calculated [1, 2, 3, 4]. The theoretical basis for these calculations is the Multistep Direct Theory by Feshbach, Kerman and Koonin (FKK theory) [5]. This theory leads to the simplification of multistep reactions as a folding of single-step reactions through the implementation of the Distorted Wave Born Approximation (DWBA). The pre-equilibrium cross-sections are subsequently calculated with a multistep direct code.
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    Radon exhalation of building materials
    (University of the Western Cape, 2018) Wentzel, Farrel Sidney; Lindsay, Robert
    Public concern about all radiation and radon exhalation from building materials has been highlighted recently. The purpose of this study is to address this public concern and to investigate the contribution of building materials to indoor radon levels. As in soil and rocks, radon gas is formed inside the building materials by decay of the parent nuclide 226Ra. It is not possible to determine the radon exhalation rate simply from the activity concentration of 226Ra, instead one must measure radon exhalation rates directly from the surface of the material. 222Rn has been identified as an important factor that could result in a health hazard by studies all around the world. The exhalation experiments were done at the UWC physics department, in the Nuclear Physics Lab. A RAD7 radon detector was used to measure the radon concentration in an air tight chamber that contained various building material samples. The RAD7 records the number of alpha particles with energy of 6.11 MeV which results from the decay of 218Po, the daughter of 222Rn. The RAD7 detector converts counts into Becquerel’s per cubic metre (Bq/m3). The building materials tested were the raw materials used in construction such as two different types of building sand, building stones, coarse aggregate, floor and roof tiles, various granites from across the world that were sourced locally and uranium bearing sandstone originating from a Beaufort-West prospecting site. Stones from this site were used as filler material in the construction of two farm houses. Most building materials were found to have a very low rate of radon exhalation. The only materials that had any significant radon exhalation were 2 granite samples with a maximum exhalation rate of 1.5 Bq.m-2.h-1 and the uranium bearing sandstone. It is safe to say that the overwhelming majority of building materials tested are safe to use but some granites may require further study. The uranium bearing sandstone is a definite radiation protection issue and should not be used in any construction.
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    Validation of Gamma Ray spectrometry process used to determine the radionuclides and radioactivity levels in decorative Granite countertops.
    (University of the Western Cape, 2016) Maibane, Kutullo Freedom; Lindsay, Robert
    Humans are continuously exposed to low level of ionizing radiation, sources include soil, medical treatment and as well as radiation emissions from natural materials like granite rocks. The radiation levels present in these granite rocks varies depending on the mineral properties and their origins. The aim of this study is to assess the radiation levels in various granite countertops available commercially in South Africa. The radiation levels present in the granite countertop samples were determined using the available low-background HPGe gamma-ray detector system at iThemba LABS. Initially, the study focused on the optimisation of the photopeak efficiencies of the detector system to match the samples, i.e. 'box-like' geometry as opposed to the traditionally used Marinelli beaker geometry. A soil sample with known activity (238U series: 940 30 Bq/kg; 232Th series: 660 20 Bq/kg and 40K: 153 8 Bq/kg) determined with Marinelli beaker geometry was used to prepare an artificial reference material for the new box geometry.
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    Variability and interannual trends in the climatology of radon-222 at two Southern Hemisphere coastal baseline sites
    (University of the Western Cape, 2021) Botha, Ryno; Lindsay, Robert
    This thesis characterises and discusses two continuous coastal Southern Hemispheric (SH) atmospheric radon (222Rn) signals. Large-scale atmospheric circulation patterns are important components of the climate system implicated in driving catastrophic events such as extreme droughts and mega-wildfires and radon measurements at coastal sites provide valuable information on interactions of terrestrial and oceanic air masses on regional to hemispheric scales. The main collaborating SH atmospheric observatories in this study are located at Cape Grim (CGO, Tasmania, 1992-2017) and Cape Point (CPO, South Africa, 1999-2017). The radon signal from a high-altitude remote island oceanic site in the Northern Hemisphere Mauna Loa Observatory (MLO, Hawaii, 2004-2015) is also incorporated for comparison purposes. The CGO radon signal is the longest and most sensitive in current existence. A variety of statistical, spectral, trend, back-trajectory and trajectory density methods are utilized in this study to illuminate features of the datasets on multiple scales. Strongly skewed radon distributions occur, with a large number of events falling into a compact range of low values (corresponding to marine air-masses) and a smaller number of events spread over a wide range of high-radon values (continental air-masses). Making use of Fast Fourier Transform power spectral analysis, prominent periodicities are identified on diurnal and annual scales. Inter-annual variations in seasonal and diurnal radon and meteorological characteristics, indicating changes in the continental/oceanic atmospheric mixing state, are evident especially during the period from 2012 to 2017, perhaps associated with the strong El-Niño southern oscillation centred on 2015. A slow but systematic decline in CGO and CPO radon levels is evident over the dataset, associated with fewer continental and more marine air-masses impacting the coastal stations. The long-term trends observed in the atmospheric radon signal may indicate changes in SH circulation patterns over time, perhaps associated with climate change effects.