Environmental Uranium Mobility

Project Team: Richard Collins, Daniel Boland and David Waite, in collaboration with Timothy Payne (Australian Nuclear Science and Technology Organisation); Australian Research Council Future Fellowship (Collins) FT110100067; 2012-2015

The disposal of radionuclides (such as uranium) in engineered/geological repositories presents a particular set of scientific and environmental challenges owing to the long-lived nature of the isotopes and thus proclivity for mobilisation to groundwaters. Whilst engineered and geological containment barriers represent one method of mitigating radionuclide mobility, incorporating the contaminant into a less-mobile form is another, more recently observed, technique. Indeed, it has been shown that when poorly-structured iron oxides (such as ferrihydrite) are recrystallised [via Fe(II)-catalysis] to a more crystalline / less reactive form (e.g. goethite or magnetite), any uranium present is essentially immobilised. However, our previous research has shown that the presence of silica has been shown to inhibit this Fe(II)-catalysed process, retaining the more reactive iron minerals (Jones et al. 2009).

As such, the major thrust of this project is to understand the fate of uranium during the iron recrystallisation process when in the presence of silica, a naturally abundant mineral. Measurements are made using x-ray absorption spectroscopy (both near and extended edge) to give a greater understanding into the structural environments of iron and uranium species.  Our initial results signify that silica does impede iron mineral transformation, with adsorbed and coprecipitated uranium only partially immobilised by the process.

Further Reading

Collins RN, T Saito, N Aoyagi, TE Payne, T Kimura and TD Waite (2011) Applications of time-resolved laser fluorescence spectroscopy to the environmental biogeochemistry of actinides.  J. Environ. Qual. (accepted 09/2010).

Boland DD, RN Collins, TE Payne and TD Waite (2011) Effect of amorphous Fe(III) oxide transformation on the Fe(II)-mediated reduction of U(VI). Environ. Sci. Technol 45:1327-1333.

Jones AM, Collins RN, Rose J and Waite TD (2009) The Effect of silica and natural organic matter on the Fe(II)-catalysed transformation and reactivity of Fe(III) minerals, Geochimica et Cosmochimica Acta, 15, 4409-4422.

Avoscan L, S Milgram, G Untereiner, R Collins, H Khodja, J Covès, JL Hazemann, M Carrière and B Gouget (2009) Assessment of uranium and selenium speciation in human and bacterial biological models to probe changes in their structural environment. Radiochim. Acta 97(7):375-383.

Boland DD, RN Collins, AM Jones, TE Payne and TD Waite (2009) Investigating the fate of U(VI) during the Fe(II)-catalysed transformation of Fe(III) minerals with X-ray absorption spectroscopy.  Proceedings of 16th AINSE Conference on Nuclear and Complementary Techniques of Analysis, Lucas Heights, Australia, November 2009. http://www.ainse.edu.au/__data/assets/pdf_file/0011/48683/NCTA-07-Boland1.pdf

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