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Graduation date: 1968

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / Radiostrontium (90Sr and 89Sr) has been released to the environment by global fall-out following atmospheric nuclear explosions, by waste discharges and fall-out from the Chernobyl. 89Sr, with a half-life of 50.5 days, quickly decays to undetectable levels, while 90Sr is radiobiologically more important because of its longer half-life of 28.78 years, and because it behaves chemically similar to Ca, and accumulates in bones and teeth. Cost effective and relatively simple procedures for determination of radiostrontium are desirable. An accurate determination of radionuclides from various sources in the environment is essential for assessment of the potential hazards and suitable countermeasures both in case of accidents, authorised releases and routine surveillances. Reliable radiochemical separation and detection techniques are needed for accurate determination of alpha and beta emitters. Rapid analytical methods are needed in case of an accident for early decision-making. At the Koeberg Nuclear Power Station (KNPS), 90Sr analysis are performed on liquid effluent samples making use of the traditional fuming nitric acid method, and subsequent counting of particulate samples on an alpha/beta proportional counter. This method is often at times very time – consuming, and involves many precipitation steps. The use of fuming nitric acid is also very dangerous and could lead to severe personnel injuries in the event of an accident. This project focussed on the application of Sr-Spec resin in the analysis of 90Sr. This work presents the methods for 90Sr analysis for both effluent samples as well as environmental samples. This research also focussed on the calibration of the different radiometric instruments, which are the Liquid Scintillation Counter, the Alpha/Beta Counter as well as the Gamma Detector.

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The use of cosmogenic beryllium-7 (7Be) as a soil and sediment tracer relies upon a number of important assumptions which to date have not been fully underpinned by supporting data. As a catchment management tool 7Be offers unique potential to assess the effects of recent land use or climate change but further research is required to provide confidence in key data and elucidate sources of uncertainty. Through a range of laboratory and field studies, this thesis aims to explore knowledge gaps relating to i) the temporal and spatial dynamics of 7Be activity in rainfall which has importance in the context of estimating fallout input during erosion studies ii) adsorption behaviour in soils which is of critical importance when considering tracer stability at the field and catchment-scale and iii) the reliability of erosion estimates using 7Be inventories at the slope-scale to address the current lack of model validation. Findings showed temporal and spatial variability of 7Be fallout emphasising the need for regular site-specific sampling to determine fallout flux during erosion studies. Data supported the assumption of rapid tracer adsorption upon fallout although highlighted the potential for 7Be mobility under changing environmental parameters, thus, raising questions with regard to tracer stability at the catchment-scale. Field investigations demonstrated the potential for current models to overestimate erosion rates by failing to accurately represent key model components, namely, 7Be depth distributions, particle size enrichment and fallout input dynamics. Where these factors cannot be determined directly, a range of erosion estimates should be given based upon realistic sensitivity analysis of model components. In this manner, reported uncertainties will reflect field processes rather than propagated analytical uncertainty alone.

Graduation date: 1963