title: Determining the radon exhalation rate from a gold mine tailings dump by measuring the gamma radiation.
abstract: The mining activities taking place in Gauteng province, South Africa have caused millions of tons of rocks to be taken from underground to be milled and processed to extract gold. The uranium bearing tailings are placed in an estimated 250 dumps covering a total area of about 7000 ha. These tailings dumps contain considerable amounts of radium and have therefore been identified as large sources of radon. The size of these dumps make traditional radon exhalation measurements time consuming and it is difficult to get representative measurements for the whole dump. In this work radon exhalation measurements from the non-operational Kloof mine dump have been performed by measuring the gamma radiation from the dump fairly accurately over an area of more than 1 km(2). Radon exhalation from the mine dump have been inferred from this by laboratory-based and in-situ gamma measurements. Thirty four soil samples were collected at depths of 30 cm and 50 cm. The weighted average activity concentrations in the soil samples were 308 ± 7 Bq kg(-1), 255 ± 5 Bq kg(-1) and 18 ± 1 Bq kg(-1) for (238)U, (40)K and (232)Th, respectively. The MEDUSA (Multi-Element Detector for Underwater Sediment Activity) γ-ray detection system was used for field measurements. The radium concentrations were then used with soil parameters to obtain the radon flux using different approaches such as the IAEA (International Atomic Energy Agency) formula. Another technique the MEDUSA Laboratory Technique (MELT) was developed to map radon exhalation based on (1) recognising that radon exhalation does not affect (40)K and (232)Th activity concentrations and (2) that the ratio of the activity concentration of the field (MEDUSA) to the laboratory (HPGe) for (238)U and (40)K or (238)U and (232)Th will give a measure of the radon exhalation at a particular location in the dump. The average, normalised radon flux was found to be 0.12 ± 0.02 Bq m(-2) s(-1) for the mine dump.
authors.affiliation: Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
authors.forename: Joash N
authors.initials: JN
authors.lastname: Ongori
authors.affiliation: Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa. Electronic address: rlindsay@uwc.ac.za.
authors.forename: Robert
authors.initials: R
authors.lastname: Lindsay
authors.affiliation: Department of Physics, Stellenbosch University, Private Bag X1, Matieland, Stellenbosch 7602, South Africa.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Newman
authors.affiliation: Department of Nuclear Physics, iThemba Laboratory for Accelerator Based Sciences (LABS), P. O. Box 722, Somerset West 7129, South Africa.
authors.forename: Peane P
authors.initials: PP
authors.lastname: Maleka
mesh_terms: D005720:Gamma Rays; D006046:Gold / Q000737:chemistry*; D008906:Mining; D011886:Radon / Q000032:analysis*; D013019:South Africa
chemical_list: D006046:Gold; D011886:Radon
keywords: Gamma-ray spectrometry; Gold mine tailings; Radon; Radon exhalation; South Africa