Press releases
Please quote Nature Materials as the source of these items.
April 2003
Radiation defects: getting back to basics
Pure carbon usually occurs in two forms, graphite and diamond, whose different structures determine their properties. So the relative softness of graphite is explained by its layered structure - sheets of graphite sliding over each other to leave a pencil mark on paper. But a new look at the response of graphite to irradiation - as experienced by graphite cores in nuclear reactors - in the May issue of Nature Materials, suggests that its behaviour is more complicated than we thought.
The damaging effects of radiation on graphite in a nuclear reactor were most dramatically seen in the Windscale reactor fire of 1957. In such air-cooled reactors, defects created by radiation store energy in the graphite cores, but if this energy is released it can cause a reactor fire. The new computer simulations by Telling and colleagues show that, contrary to the conventional view that defects in a graphite sheet remain within the plane, carbon atoms can rotate outside the layer and even form bridges between layers.
Modern nuclear reactors operate at high enough temperatures that these graphite defects are under control. Nevertheless, these findings may have implications for the decommissioning of old nuclear reactors, and for the development of devices based on carbon nanotubes (which are essentially rolled-up sheets of graphite).
