Chemical types of bounding of natural radionuclides in TENORM
Duisburg-Essen (2007), 192, A-33 S.
Dissertation / Fach: Geowissenschaften
Fakultät für Biologie » Geologie
Wiegand, Jens (Doktorvater, Betreuerin)
Gellermann, Rainer; Hirner, Alfred V. (GutachterIn)
The investigation of the TENORM samples for their initial activity concentrations, the chemical types of bounding the contained natural radionuclides occur, the resulting radon emanation coefficients and finally the transfer factors, leads to the following statements: • Phosphate industry: 1. In dependence from the geological origin, the used raw materials and the produced fertiliser can contain enhanced initial activity concentrations, the latter mainly uranium 2. From the raw materials 226Ra can be easily mobilised, in case of the phosphogypsum waste and produced fertiliser attention must be paid for 238U and 210Pb 3. Highly contaminated raw materials can result in enhanced radon emanation rates, also the fertiliser can contribute to some radon enhancement 4. There is a well developed transfer factor for 226Ra from all materials involved into plants • Aluminium industry: 1. In dependence from the geological origin, the used raw materials can contain enhanced initial activity concentrations 2. 226Ra is the relevant radionuclide and can be easily mobilised from the raw materials and the waste as well 3. Highly contaminated raw materials can result in strongly enhanced radon emanation rates, 4. Transfer factors are established for 226Ra into water from both types of bauxites • Refractory industry: 1. Enhanced initial activity concentrations occur in the additive zircon sand and the fused zirconia mullite products 2. 226Ra is the relevant radionuclide being present in all materials but not really leachable, 210Pb can be easily mobilised from the filter dust waste in some extent 3. The radon emanation rates are generally low 4. 228Th is transferable into water and plants • Crude oil exploitation: 1. Enhanced initial activity concentrations especially of 210Pb occur in the sludge and scale wastes 2. 210Pb is the relevant radionuclide being present in all materials and is mostly bound to organo-sulphur compounds, relatively few amounts are easily mobilisable 3. The sludge can cause really high radon emanation rates 4. The sludge releases both radium isotopes and 228Th as well for water • Hard coal extraction: 1. Enhanced initial activity concentrations of 226Ra can occur close to the mining water discharge point and along the riverbanks 2. 226Ra is the relevant radionuclide being enhanced present in all materials, but is not mobilisable, 228Th is found under easily available, reducible and oxidisable conditions • Thorium compounds industry: 1. Strongly enhanced initial activity concentrations of 228Ra and 228Th can occur in soils being influenced by former thorium processing 2. 228Ra and 228Th are proven to be available especially for plants 3. The resulting transfer factors for the pathway “solid-plant” concern all radionuclides • Uranium industry: 1. Strongly enhanced initial activity concentrations occur in the uranium ores and the tailing wastes, unwanted by-products can be contaminated partly 2. All uranium radionuclides are not preferably bound in the raw materials, especially 226Ra and 210Pb can be easily leached from the tailings, the unwanted by-products dead rocks mainly contain the uranium radionuclides bound to sulphides, sediments show uranium radionuclides being bound to oxides, the most of them is strongly fixed 3. The uranium ores and tailing wastes cause really high radon emanation rates, in case of dead rocks they are lower, contaminated sediments can show enhanced emanation rates 4. Important transfer factors are set from tailings into water for 226Ra and into plants for uranium and lead, from sediments 226Ra can be transferred into plants • Investigation procedure: 1. The developed investigation procedure as presented in this study to determine simultaneously many radionuclides in extraction liquids by gamma-spectrometry is more applicable and reliable for highly contaminated samples 2. The influence of different grain sizes on the radionuclides’ mobilisation potential is rather low 3. Uranium oxides can not be cracked by scientific extraction procedures 4. Some limitation of the investigation procedure seems to be given by the low amounts of starting material for the extraction procedures as proposed in their instructions and the resulting small extraction liquid volumes For all those reasons, TENORM must be controlled not only for their initial activity concentrations, radon releases and the resulting radiological hazard, but for their radionuclide mobilisation potential and environmental influences, too.