Making, Stabilising and Understanding Unusual Intermediate Oxidation States in the Early Actinides

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Energy use, especially in the form of electricity is an essential requirement for modern life, and one that most of us could not even contemplate living without. From transport and travel to computers and televisions, the global demand for energy is on the increase. The drawback of recent technological advances however, is that greenhouse gases, in particular CO2 are emitted during the production of energy. Growing public awareness of climate change and its future impacts on the world as we know it have recently shifted the focus from fossil fuel usage to alternative energy sources, and legislation is now in place for reducing the carbon footprint. Among the alternative options, nuclear energy remains the most viable in the short term since the technology is already in place for proficient energy production. Nuclear electricity generation currently supplies around 17 % of the worldwide energy demand (18.4 % in the U.K.) and has already created a legacy of environmental problems due to high level radioactive wastes associated with waste storage and production. This proposal concentrates on the chemistry of the radioactive actinide ions (uranium, plutonium and neptunium) used in the nuclear fuel industry, ways to identify and 'clean up' toxic wastes from the environment and methods to eliminate the need for storing high level wastes in the future. Since the actinides used in current reactors are generated under conditions that are dissimilar to the natural environment, the chemistry of these metals outside of the reactor is completely different and they often exist in unusual oxidation states for a certain period of time before being further altered or reacting. In order to reduce the detrimental impact these radiotoxic wastes have on the environment, it is imperative that we understand their chemistry in full. This can only be achieved by studying the chemistry of these metals in their reactive unstable oxidation states in controlled laboratory conditions using specially designed chemistry. By doing this, we can identify methods of stabilizing these oxidation states and ways for selectively removing them from contaminated sites so that they can ultimately be recycled and used for further energy production. This project will initially examine the chemistry of uranium in the +V oxidation state by synthesizing a range of complexes stabilized by different organic groups under anaerobic conditions, and study the way the chemical groups around them inhibit or enhance reactivity. This chemistry will then be applied to the stabilization of the more radiotoxic elements plutonium and neptunium. At the core of the project is the development of a spectroscopic fingerprint (using time resolved luminescence spectroscopy) of unstable (and stable) oxidation states of these elements in order to develop a non-invasive method of identifying such species in the environment that may exist on a timescale that is too fast using current radiometric and chemical methods.