X-ray fluorescence analysis in environmental radiological surveillance using HPGe detectors |
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| Institution: | 1. Nuclear Engineering Program, Federal University of Rio de Janeiro, Av. Horácio Macedo, 2030 - CT, Fundão, 21945-970 Rio de Janeiro, RJ, Brazil;2. Federal University of Rio de Janeiro, Polytechnic College, Av. Athos da Silveira Ramos, 149 - CT, Fundão, 21941-909 Rio de Janeiro, RJ, Brazil;3. Engineering Military Institute, Nuclear Engineering Department, Praça General Tibúrcio, 80, Urca, 22290-270 Rio de Janeiro, RJ, Brazil;4. State University of Rio de Janeiro, Structures and Foundations Department, R. São Francisco Xavier, 524, Maracanã, 20550-900 Rio de Janeiro, RJ, Brazil;1. Precision Stratigraphy Associates and the University of Tulsa, 149 W. Ridge Rd., Cleveland, OK, 74020, USA;2. Rebellion Energy, 5416 S. Yale Ave., Suite 300, Tulsa, OK, 74135, USA;3. Brown and Caldwell, 2 Park Way, Suite 2A, Upper Saddle River, NJ, 07458, USA;4. Laredo Petroleum, Inc., 15 W. 6th Street, Suite 900, Tulsa, OK, 74119, USA;5. Oklahoma State University, School of Geology, Stillwater, OK, USA;6. Research Institute of Petroleum Exploration & Development, Langfang, Hebei, 065007, China;1. Department of Nuclear Physics, Faculty of Physics and Engineering Physics, VNUHCM-University of Science, 227, Nguyen Van Cu Street, District 5, Ho Chi Minh City, Viet Nam;2. Nuclear Technique Laboratory, VNUHCM-University of Science, 227, Nguyen Van Cu Street, District 5, Ho Chi Minh City, Viet Nam;3. Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan |
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| Abstract: | X-ray fluorescence (XRF) has been proven to be a valuable tool for determining trace quantities of heavy metals, such as uranium and lead, in different types of samples. The present paper demonstrates the applicability of XRF spectrometry to measure the concentrations of these heavy metals in samples from natural ore and soil. The values of uranium concentrations in rock from the Peña Blanca uranium ore, in Chihuahua, México, were calculated for the purpose of precertifying the rock powders samples. The comparison with other techniques, such as inductively coupled plasma atomic emission spectrometry, atomic absorption spectrometry, alpha spectrometry and electron microscopy, was used to complete the precertification process, so that the sample powders may be used as secondary standards. The source-sample-detector geometry and the incident angle are the most important factors for obtaining low detection limits. The selected system uses a 57Co source of about 0.1 mCi to excite the K X-rays from uranium and lead. X-rays were recorded on a CANBERRA HPGe coaxial detector. The comparative results for two incident angles (90° and 180°) performed previously by other authors show that the best geometry is the backscattering geometry. In the present paper, using EGS4 code system with Monte Carlo simulation, it was possible to determine the location and distribution of background produced by the Compton edge in the optimized geometry. This procedure allowed to find the minimum detectable concentration of uranium and lead, which was experimentally calculated using standards. The possibility of performing in vivo measurements rapidly and easily, as well as the factors affecting accuracy and the minimum detectable concentration in several samples are also discussed. |
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