Naturally Occurring Radioactive Material in Two Mine Waste Sites in Finland

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http://urn.fi/URN:NBN:fi:hulib-202006233407
Title: Naturally Occurring Radioactive Material in Two Mine Waste Sites in Finland
Author: Suominen, Topi
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2020
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-202006233407
http://hdl.handle.net/10138/316939
Thesis level: master's thesis
Discipline: Radiokemia
Abstract: Naturally occurring radioactive material (NORM) is defined by the IAEA as “Radioactive material containing no significant amounts of radionuclides other than naturally occurring radionuclides”. In the EC directive 2013/58/Euratom several industry sectors are listed that are known to often deal with NORM, either in residues, wastes, by-products, or products, the mining industry is one of these. The risk posed by NORM is defined by exposure potential and concentration. In the wastes created by the mining industry these are tied to the management of wastes and concentration of radionuclides in the exploited mineral resource. Wastes created by the mining industry are often of environmental concern as they are in many cases piled on the mining site after closure. The tailings of a mine may contain pyrite, which when oxidized creates acid mine drainage. The acidic waters in such sites can enhance the mobility of radionuclides and other harmful elements. In this thesis two mine waste sites were selected for study, which were known to have had issues with natural radioactivity. These two sites were the old Zn, Pb, Cu mine of Vihanti and the Pb, REE mine of Korsnäs. The current state of these two sites was studied. Possible transport of radionuclides or other harmful elements and the dose to a member of the public on the sites was also studied. Soil, waste, sediment, and water samples were collected from both sites and analyzed. Solid samples were analyzed using gamma spectrometry and the radionuclides of interest were: 238U, 226Ra, 210Pb, 232Th, 228Th, 228Ra. Water samples were analyzed with ICP-MS and the elements measured with this method were: Al, Si, P, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb and U. In addition, some mine waste samples were studied further using XRF and SR-XRPD methods. The results of this thesis indicate that in Vihanti, the wastes have been adequately covered, reducing the external radiation dose to near background levels. The gamma spectrometry results showed no concerning activity concentrations in soil, sediment or waste samples. Two locations were found where the ICP-MS analyses yielded high concentrations of nearly all measured elements, the pH of these sites was low as well. Signs of acid mine drainage were found in these locations, but the effects seem to be localized and no evidence of large-scale transport of contaminants through waterways was found. In Korsnäs the wastes are split into two piles, one containing tailings, and the other enriched lanthanide that was never sold. The results indicate that the lanthanide pile has been adequately covered and the external radiation dose around the pile is near background levels. While the tailings have not been covered like the lanthanide pile has, the results showed that a member of the public is unlikely to receive a dose exceeding 0.1 mSv/a from spending time on the site. Activity concentrations exceeding 1 Bq/g were detected in samples collected from the lanthanide pile, with some evidence of uranium mobilization also seen. In addition, uranium concentrations in the waters of the old open pit mine were relatively high.
Subject: Naturally occurring radioactive material
NORM
Uranium
Radium
Mining
Tailings
Mine wastes
Natural radioactivity
Vihanti
Korsnäs
Gamma spectrometry
ICP-MS
XRF
SR-XRPD


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