The relationship between microcracking and mechanical properties in neutron-irradiated beryllium oxide

Abstract

Beryllium oxide bend test specimens of two grain sizes, 1—2 microns and 8—35 microns, were irradiated to fast neutron doses of up to 5 .6 x 1020 nvt (above 1 MeV) at 75 — 100ºC. Specimens were examined by X—ray line breadth (30.0 reflection), modulus of rupture, elastic modulus, open porosity, and lattice parameter measurements. The results show that there is no significant change in mechanical properties up to the dose at which microcracking is first observed i.e. .5 x 1020 nvt in the case of the fine grain size material and 1.2 x 1020 nvt in the case of the coarse grain size material. Above these doses the modulus of rupture and the apparent elastic constants fall rapidly. Microcracking occurred at an earlier dose in both materials than would have been expected from earlier work.