Nuclear Research: Minerals, Sulfide, and Radwaste Disposal
Waste and clean-up 3rd August 2017
Nuclear and radiochemistry research is a diverse and unique field of study. This month we’ve asked some PhD students to summarise their research and how this may apply to the nuclear industry. Luke Townsend discusses his work on the ‘Long-term Fate of Radionuclides during Sulfidation’.
When anyone mentions nuclear power, one of the first issues people tend to bring up is that of nuclear waste and how damaging it can be to the environment. It’s no secret that the UK has plenty of radioactive waste being stockpiled in interim storage, but what isn’t often common knowledge is that there is a plan for disposing of it all. Currently in the UK we’re in the process of carving out a pathway to a Geological Disposal Facility, or GDF. Whilst this road has been somewhat problematic to tread in the past, meandering in various directions with numerous dead ends, over recent years a firm plan and research programme has been set in place to make safe radwaste disposal a reality.
In order to achieve this goal, we require a thorough understanding of all the aspects involved in such a task; from what the waste containment material should be, to how the environment may be impacted by leaving waste in the ground for millions of years. Exploring the environmental questions is where my PhD project comes into play, though this may not be entirely obvious from the title of ‘Long-term Fate of Radionuclides during Sulfidation’.
Millions of years after radwaste has been disposed of, all the containment will have corroded away leaving the waste, and therefore radionuclides, open to the external environment. In the deep subsurface, two key components in this scenario will be present; iron oxide minerals that are ubiquitous throughout the environment, and bacteria that possess the ability to produce sulfide through metabolism of sulfate, known as sulfate-reducing bacteria (SRB). The project aims to understand how the presence of sulfide can affect radionuclides, namely uranium and technetium, in an environment relevant to geological disposal of radioactive waste. Research has been done previously showing how radionuclides may interact with iron oxide minerals1-3 or with sulfide,4 however, studies of the entire system are rare within the literature5,6 leaving a lot to be explored.
Whilst the science involved in this project aims to study some fairly fundamental systems, the work performed will have significant ‘real world’ applications. The research will build into the safety case used by the government body Radioactive Waste Management (RWM) when initiating the implementation of a UK GDF. Furthermore, areas of the research could prove useful in the future when studying and remediating areas of radionuclide contaminated land.
(1) Marshall, T. A., Morris, K., Law, G. T. W., Livens, F. R., Mosselmans, J. F. W., Bots, P. & Shaw, S. (2014). Incorporation of Uranium into Hematite during Crystallization from Ferrihydrite. Environmental Science & Technology, 48(7), 3724-3731.
(2) Marshall, T. A., Morris, K., Law, G. T. W., Mosselmans, J. F. W., Bots, P., Parry, S. A. & Shaw, S. (2014). Incorporation and Retention of 99-Tc(IV) in Magnetite under High pH Conditions. Environmental Science & Technology, 48(20), 11853-11862.
(3) Marshall, T. A., Morris, K., Law, G. T. W., Mosselmans, J. F. W., Bots, P., Roberts, H. & Shaw, S. (2015). Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste. Mineralogical Magazine, 79(6), 1265-1274.
(4) Hua, B., Xu, H., Terry, J. & Deng, B. (2006). Kinetics of Uranium(VI) Reduction by Hydrogen Sulfide in Anoxic Aqueous Systems. Environmental Science & Technology, 40(15), 4666-4671.
(5) Alexandratos, V. G., Behrends, T. & Van Cappellen, P. (2014). Sulfidization of lepidocrocite and its effect on uranium phase distribution and reduction. Geochimica et Cosmochimica Acta, 142, 570-586.
(6) Alexandratos, V. G., Behrends, T. & Van Cappellen, P. (2017). Fate of Adsorbed U(VI) during Sulfidization of Lepidocrocite and Hematite. Environmental Science & Technology.
(7) Video from ‘https://www.gov.uk/government/news/geological-disposal-understanding-our-work’