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The effect of microbial action on nuclear waste management: is there enhanced leaching from bitumen and increased radionuclide movement through geologic media?

University of British Columbia

Long-term management of nuclear wastes demands absolute physical isolation of noxious radionuclides from the biosphere until decay to safe levels has occurred. Due to the extremely long half-life of some isotopes, the required isolation may be on the order of millennia. Past research on radioactive wastes has centered on the physicochemical mechanisms that may effect a premature return of radionuclides to the environment. However, biological action in a radwaste disposal site may have two major effects: 1) physical destruction of the solidifying matrix through solubilization or oxidation; and/or 2) enhanced movement of radionuclides through (adsorbent) geologic media by production of various chelating agents. The work presented here is focused on both these microbiological processes. ⁶⁰Co and ¹³⁷Cs encapsulated in bitumen was allowed to undergo microbial attack by a selected hydrocarbonoclastic culture under idealized environmental conditions. The radionuclides released by this process were then evaluated for their ability to bind with selected geologic media. In order to compare the effect of reduced adsorption due to microbial action, synthetic chelating agents were used as a standard. The same hydrocarbonoclastic culture used for these experiments was also tested for its sensitivity to y-irradiation. Subsequent analysis showed microbial attack of bitumen did not enhance the release of the ions. However, a decreased adsorption to the geologic media was observed but the effect was much less than that observed for the synthetic chelating agents. The level of r-radiation expected in the final waste repository will not effect the viability of the organisms tested.

Text

2010-04-16

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http://hdl.handle.net/2429/23745

Civil Engineering

University of British Columbia

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