The hot isostatic pressing process has been applied at temperatures up to 1500°C for the fabrication of high temperature fuel rods composed of UO2 clad in columbium and UO2 in iron-aluminum type alloy. The fused UO2 powder apparently becomes quite plastic at temperatures above 1200°C and can be isostatically compacted at 1500°C to 98% of its theoretical density. Columbian tubes particularly lend themselves to the fabrication of fuel rods by simultaneously compacting and cladding UO2 powders in the tubes, but the cast iron-aluminum type alloy that was used was unsatisfactory because of its brittleness.