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 w/o 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 w/o

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... zirconium, 700 ppm oxygen and 0.17 w/o zirconium, and 300 ppm oxygen and 0.02 w/o zirconium. Representative specimens of these alloys retained their hardness up to 900 C. The 10 and 20 w/o uranium alloys were successfully forged at 2500 F and rolled at 1800 F to sheet. Fabrication characteristics of the remaining alloys are under investigation. The 0.2 per cent offset yield strength of the 10 w/o uranium alloy was 57,200 psi at room temperature and 36,900 psi at 1600 F. For the 20 w/o uranium alloy it was 93,200 psi at room temperature and 71,000 psi at 1600 F. The corrosion life of all of the alloys Jn air at 572 F and in CO2 at 600 F was superior to that of unalloyed niobium. In 1000-hr exposures to 600 F water most of the alloys exhibited corrosion rates only two or three times greater than that of Zircaloy-2. All of the alloys appear compatible with NaK at 1600 F. The impurity combinations employed in the base niobium appeared to have no effect on the corrosion behavior and mechanical properties of the alloys.