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KMID : 0364920140390010007
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Journal of Radiation Protection and Research
2014 Volume.39 No. 1 p.7 ~ p.13
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Characterization of Particulates Containing Naturally Occurring Radioactive Materials in Phosphate Processing Facility
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Lim HaYan
Choi Won Chul
Kim Kwang-Pyo
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Abstract
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Phosphate rock, phosphogypsum, and products in phosphate processing facility contain naturally occurringradioactive materials (NORM). Therefore, they may give rise to enhanced radiation dose to workers due to inhalation ofairborne particulates. Internal dose due to particle inhalation varies depending on particle properties. The objective of thepresent study was to characterize particle properties at the largest phosphate processing facility in Korea. A cascade impactorwas employed to sample airborne particulates at various processing areas in the plant. The collected samples were used forcharacterization of particle size distribution, particle concentration in the air, and shape analysis. Aerodynamic diameters ofairborne particulates ranged 0.03-100 μm with the highest concentration at the particle size range of 4.7-5.8 μm (geometricmean = 5.22 μm) or 5.8-9.0 μm (geometric mean = 7.22 μm). Particle concentrations in the air varied widely by samplingarea up to more than two orders of magnitude. The large variation resulted from the variability of mechanical operationsand building ventilations. The airborne particulates appeared as spheroids or rough spherical fragments across all samplingareas and sampled size intervals. Average mass densities of phosphate rocks, phosphogypsums, and fertilizers were 3.1-3.4,2.1-2.6, and 1.7 gcm-3, respectively. Radioactivity concentration of uranium series in phosphate rocks varied with country oforigin, ranging 94-866 Bqkg-1. Among the uranium series, uranium was mostly concentrated on products, including phosphoricacid or fertilizers whereas radium was concentrated on byproducts or phosphogypsum. No significant radioactivity of 226Raand 228Ra were found in fertilizer. However, 40K concentration in fertilizer was up to 5,000 Bq g-1. The database establishedin this study can be used for the accurate risk assessment of workers due to inhalation of airborne particles containing NORM.In addition, the findings can be used as a basic data for development of safety standard and guide and for practical radiationsafety management at the facility.
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KEYWORD
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Natural Radiation Safety Management Act, Naturally Occurring Radioactive Material (NORM), Phosphate processingfacility, Inhalation dose, Particle property
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