In a continuing program, fabrication characteristics, physical and mechanical properties, and corrosion behavior in air, CO2, NaK, water, and steam were studied for . binary niobium fuel alloys containing 10, 20, 30, 40, 50, and 60 wt.% uranium To evaluate the effects of two major impurities of niobium, oxygen, and zirconium, three niobium base stocks, differing according to the level of these impurities, were used for each alloy. The impurity combinations employed were 600 ppm oxygen and 0.74 wt.% zirconium, 700 ppm oxygen, and 0.17 wt.% zirconium, and 300 ppm oxygen and 0.02 wt.% zirconium, Representative specimens of these alloys retained their hardness up to 900 deg C The 10 and 20 wt.% uraniuin alloys were successfully rorged at 2500 deg F and rolled at 1800 deg F to sheet. Fabrication characteristics of the remaining alloys are under investigation. The 0.2% offset yield strength of the 10 wt.% uranium alloy was 57,200 psi at room temperature and 36,900 psi at 1600 deg F. For the 20 wt.% uranium alloy it was 93,200 psi at room temperature and 71.000 psi at 1600 deg F. The corrosion life of all of the alloys in air at 572 deg F and in CO2 at 600 deg F was superior to that of unalloyed niobium. In 1000- hr exposures to 600 deg F water most of the alloys exhibited corrosion rates only two or three times greater than that of Zircaloy-2. All oi the alloys appear compatible with NaK at 1600 deg F. The impurity combinations employed in the base niobium appeared to have no effect on the corrosion behavior and mechanical properties of the alloys. (auth).