The flux-level effect in radiation damage in graphite

Abstract

The evidence for flux level effects in high flux neutron irradiation damage in graphite is discussed in terms of the results of transmission electron microscopy, which reveals resolvable interstitial clusters. These clusters are shown to be most naturally accounted for by a homogeneous nucleation model. Insofar as the properties studied depend on the presence of the clusters and of the isolated single vacancies from which they arise, it is shown that this model is fully consistent with the equivalent irradiation temperature correction for flux level effects up to 300° C in DIDO. Flux level effects are not expected, and have not been reported, at higher temperatures, at any rate until vacancy nucleation becomes important. It is suggested that the lines of argument adopted may be of value in establishing consistent dose scales and in investigating possible flux level effects in other materials.