Strength of irradiated beryllium oxide fuelled with UO2-ThO2.

The mechanical strength of hot-pressed and cold-pressed and sintered dispersions of (U,Th)O2 in BeO was measured before and after irradiation using the diametral compression test. The addition of more than 5 volume per cent. (U,Th)02 lowered the unirradiated strength to about 60 per cent, of the strength of BeO. Irradiation resulted in a marked drop in strength of all coarse dispersions. Hot-pressed fine dispersions behaved similarly to coarse dispersions of the same composition but the cold-pressed fine dispersions exhibited an apparent increase of strength on irradiation. High temperatures favoured the retention of strength during irradiation