Radiation-Induced Dimensional Changes in Large Graphite Bars

The radiation-induced contraction of large graphite bars irradiated at high temperatures is approximately twice that of the small cylindrical samples that are conventionally studied. Although the reasons for this are not clear, the effect appears to be associated with variations in anisotropy within the large bars. These results suggest that methods of monitoring distortion of graphite-moderated reactors by use of small samples be reviewed and the data examined for information on possible explanations of this effect.