A number of bulk analysis techniques developed particularly for the mining industry by the CSIRO Division of Mineral Physics are reviewed. With these techniques, analyses are obtained directly from 3-30 kg samples without further sample preparation, or from material located on conveyor belts. Because penetrating neutron and γ-radiation is used, measurements are obtained from a large volume of sample, which ensures that the analyses are representative of the bulk. γ-Ray techniques have been used to determine the grade of 25 kg samples of iron ore and to detect shale on conveyor belts. The bulk analyser for iron ore measures the backscattered gamma rays from a60Co γ-ray source, and an accuracy of 0.35% Fe can be obtained. The on-stream shale detector distinguishes shale from high-grade iron ore by means of the greater natural γ-ray activity of the shale. A thermal-neutron irradiation technique (called SIROSA, for CSIRO On-Stream Analysis) that uses a252Cf neutron source has been developed for the simultaneous determination of iron and aluminium (expressed as Al2O3) in iron ore on a conveyor belt. Although the speed of the conveyor has no direct effect on the iron measurements, it must not exceed about 3 m/min if good accuracy for alumina is required. Consequently, an auxiliary conveyor belt is required to avoid interference with normal ore processing. Dynamic trials have demonstrated that accuracies of 0.6% Fe and 0.1% Al2O3can be obtained. Other applications of thermal-neutron activation analysis include the determination of alumina in 10-20 kg samples of bauxite and coal with accuracies of 0.5 and 0.2% Al2O3respectively, and the determination of manganese and alumina in manganese ores. Fast-neutron activation analysis using241Am-Be neutron sources has also been adapted to bulk analysis. Successful applications include the determination of silicon (expressed as SiO2) in iron ores with an accuracy of 0.15% SiO2, and the simultaneous determination of alumina and silica in bauxites with accuracies of 0.7% Al2O3and 0.3% SiO2. A combination of fast- and thermal-neutron activation has been applied to the determination of soil in shredded sugar cane with an accuracy of 0.1% soil. © 1983.
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