Irradiation behaviour of hot-pressed dispersions of (U,Th)Be13 in beryllium - second irradiation experiment.

Fuel specimens having uranium—thorium beryHides as the fissile bearing phase were irradiated at 400 to 700 ºC to burn—ups between 7 and lla/0 uranium in a predominantly thermal flux, two specimens of massive (U.;Th)Be 13 exhibited good dimensional stability and low fission gas release. Dispersion specimens containing 20, 35, and 50v/o (U,Th)Be13 swelled by 3 to 18 per cent0 and released up to 33 per cent, of the gaseous fission products. The results indicate that the mixed beryllide is an inherently good fuel material and lead to the conclusion that the poor irradiation stability of hot—pressed specimens may not be typical of (U,Th) Be 13— Be dispersions prepared by other techniques