The irradiation behaviour of cold-pressed and sintered beryllium oxide dispersion fuels.

Abstract

Coarse and fine dispersions of (U.Th)O2 in BeO, prepared by cold-pressing and sintering, were exposed to fission fragment damage by irradiation in a thermalised neutron flux. Irradiation temperatures were between 610ºC and 720ºC and fission densities of 3 x 1019 to 2 x 1020 fissions per cm3 of compact were achieved. The dimensional stability of all specimens was very good and the greatest volume expansion was one per cent. Estimated thermal stresses ranged up to 32,000 p.s.i. but no thermal stress failure occurred. The fine and the most dilute coarse dispersions released only 0.1 per cent, of the fission gases but the remaining coarse dispersions released from 0.6 to 4.9 per cent. Coarse fuel particles were generally cracked after irradiation and by microscopy, fission fragment damage to the fuel — BeO interfaces was observed in the high burn—up specimens. Fission gas bubbles developed in coarse fuel particles on post—irradiation annealing at 1250ºC and 1500ºC.