<p>In order to assess the risks that are associated with a deep repository of nuclear waste, it is important to know how different radionuclides behave in different environments. Since some of the most critical radionuclides in nuclear waste such as Ra-226 occur naturally in the environment, it is possible to study their behaviour directly. Peat lands are thought to be one of the most critical ecosystems due to their capability of accumulating large amounts of radioactivity and the possible exposure pathways to man.</p><p>Klarebäcksmossen is a peat land situated close to the nuclear power plant in Oskarshamn, which is one of two areas in Sweden where site investigations for a future deep repository are being conducted. In this study a complete peat-gyttja-clay profile from Klarebäcksmossen has been analysed for a large number of both natural and artificial radionuclides using gamma spectrometry. The degree of isotopic disequilibrium between different nuclides in the uranium-thorium series has been used to assess radionuclide migration and accumulation throughout the core.</p><p>The measurements indicate that uranium has been accumulated in the gyttja, but mobilised from the clay. Radium, on the other hand, has been leached from the gyttja layers, and the strikingly low Ra-226/Pb-210 ratios show that it might have been very recently. Alternatively, there is a very extensive migration of Rn-222.</p><p>In the peat low levels of radioactivity were found for most radionuclides, but with clear differences between minerotrophic and ombrotrophic peat. This may indicate that the uptake of radionuclides by peat mainly is passive. The accumulation rate for the peat has also been determined using Pb-210 dating.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-88889 |
| Date | January 2005 |
| Creators | Lidman, Fredrik |
| Publisher | Uppsala University, Department of Earth Sciences, Uppsala : Institutionen för geovetenskaper |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, text |
| Relation | UPTEC W, 1401-5765 ; 05 019 |
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