Clustering of Defects in Neutron‐Irradiated Beryllium Oxide

Transmission electron microscopy and X‐ray diffraction have been combined to study clustering of defects in BeO irradiated to neutron dosages ranging from 0.5 to 11.7×10 20 nvt at pile ambient temperature (≈︁ 100°C). Dot clusters which form in the microstructure at dosages greater than about 1.0×10 20 nvt are interpreted as being small interstitial loops, oriented on basal planes. X‐ray diffraction patterns contain duplex peaks consisting of sharp components, which reflect changes in the bulk lattice, and broad components which are related to the basal clusters. The observations are consistent with a model containing interstitial basal clusters and random point interstitials, but do not necessarily rule out the presence of point vacancies.