The Post-Disposal Behaviour of C-14 and Irradiated Graphite

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Graphite is a key waste form arising from the decommissioning of nuclear reactors such as the UK's Magnox and AGR nuclear power stations. This graphite contains a range of radioactive contaminants generated during its time in the reactor core. The safe disposal of this graphite is dependent on an understanding of how these contaminants behave in a disposal site. One of the most important contaminant associated with reactor graphite is carbon-14, a radioactive variant of the carbon naturally found in the environment. Carbon-14 is important from a risk point of view since it persists in the environment and can become incorporated into food through interaction with plants of microorganisms. Graphite arising from the decommissioning of nuclear reactors is currently destined for deep geological disposal, which involves burying deep underground which is very expensive. The aim of this project is to get a better understanding of how carbon-14 is incorporated into graphite, how it will be released from graphite under deep geological conditions and how the chemistry and microbiology of carbon-14 influence its transport out of a disposal site and its ultimate contact with people. It is hoped that this improved understanding may result in some graphite being disposed of safely to near-surface facilities and that more realistic estimates of the risks associated with graphite disposal can be made.