Alloys of uranium with niobium show good corrosion resistance in degassed, distilled water to about 315 degrees C. The alloys must be quenched from the gamma phase in order to have high temperature corrosion resistance. The corrosion resistance is destroyed by over-aging at temperatures as low as 350 degrees C. Of those tried, the alloy with best resistance to thermal aging is the uranium-5% zirconium-1.5% niobium alloy. At 290 degrees C, optimum heat treatment can result in a rate of corrosion of about 6 mg/cm sq/day. Certain moderate aging treatments, e.g., 400 degree C for two hours, result in improved corrosion resistance in the initial stages of corrosion. Alloys containing 3% niobium and small amounts of tin show promise. In addition to aging, the alloys are also sensitive to hydrogen content. Ultimate corrosion failure is believed due to absorption of corrosion product hydrodgen.