Twelve irradiated specimens of thorium-11 w/o urardum were examined. Ike specimens were f<&ricated by induction melting and casting in graphite and cold su aging to about 42 per cent reduction in area. The irradiations were conducted in the VTR in capsules equipped with thermocouples. Six specimens were irradiated to hurnups ranging from 0.5 to 0.6 total a/o at average central core temperatures ranging from 1070 to 1250 F. Three specimens exhibited severe swelling or decrepitation and three appeared to be in relatively good condition. The density of these specimens decreased from 4.9 to 9.9 per cent. The remaining six specimens mere irmdiated to bumups ranging from 0.9 to 1.5 total a/o mt average central core temperatures ranging from 970 to 1100 F. These specimens were in relatively good condition, except for three that had swollen severely at one end. Density decreases ranging from 2.4 to 3.8 per cent were determined for these specimens. Swelling of all specimens appeared to be a linear function of burnup to the highest level studied (1.5 toted a/o) and at tem.peratures below about 1100 F. Swelling increased significantly above 1100 F, even at bumups as low as 0.2 a'o. Fission-gas losses averaged about 0.5 per cent for sound specimens after burnups of 1.2 to 1.3 total a/o at around 1100 F. These losses were due to diffusion and recoil; cracked specimens exhibited higher losses. VetallograpUc examination of the specimens indicated thea neither the mcttrix material nor the fuel material was seriously affected by the irradiation. Vo evidence of corrosion by the XaK heat-transfer medium was present.

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