Volume 46, Numéro 6, 2011ICRER 2011 – International Conference on Radioecology & Environmental Radioactivity: Environment & Nuclear Renaissance
|Page(s)||S213 - S222|
|Section||Using Data for Studies|
|Publié en ligne||9 janvier 2012|
A first order assessment of the potential radiological impact of foodstuffs grown in a catchment area influenced by mining and mineral processing industries
1 South African Nuclear Energy Corporation, PO Box 582, Pretoria, 0001, South Africa
2 North-West University, Private Bag X2046, Mmabatho, 2735, South Africa
Natural radioactivity is associated with the vast mineral resources in South Africa in such concentrations that the radionuclides from the natural uranium and thorium decay series are found to pose concern for public exposure to communities living around these areas. Consumption of water and food is usually the most important route by which natural radionuclides can enter the human body and assessment of natural radionuclide levels in different foods and diets is therefore important to estimate the intake of these radionuclides by man. Sensitive measurement of three major radionuclides (in addition to 238U, 234U, 232Th, 226Ra, 224Ra and 223Ra) is necessary to calculate the estimated annual dose with a high degree of certainty i.e. 230Th, 210Pb and 210Po, while 231Pa, 227Ac and 228Ra also require improved sensitivity. In order to evaluate the yearly dose due to an individual source at a screening level of 25 μSv/a, one is faced with a required lower limit of determination (LLD) of 0.1 to 0.5 Bq/kg for certain foodstuffs. In this study the potential radiological impact of foodstuffs grown in a catchment area influenced by mining and mineral processing industries in South Africa, was determined by measuring the natural radionuclides in a number of foodstuffs collected from the area. The radionuclides were measured by non-destructive techniques such as Instrumental Neutron Activation Analysis (INAA) and low background gamma spectrometry. The assessment of natural radionuclides in foods allowed us to evaluate the items that present the highest risk to the population, and compare this to the limits established by the National Nuclear Regulator (NNR). From the public’s point of view it is important to ensure the population that the contaminant levels in specific food as a result of mining activities, do not exceed the permissible limits. For the majority of the analysed foodstuffs, the estimated dose was less than 250 μSv/a. Overestimation of dose, due to poor measurement detection limits, was clearly indicated for some of the samples. For most of the analysed nuclides, suitable data for evaluation of the yearly dose at the screening level of 25 μSv/a was obtained by broad energy gamma analysis of ashed samples. However, nuclides such as 230Th, 210Po and 231Pa has to be analysed by radiochemical separation through acid destruction of dried foodstuffs followed by individual element separations to provide suitable data with a low enough LLD not to result in an overestimation of the calculated dose.
© Owned by the authors, published by EDP Sciences, 2011
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