A study was made of the preparation of a uranium - 10 w/O niobium alloy by the bomb reduction of a suitable form of niobium and uranium tetrafluoride with calcium. A compound with a probable formula of Na2NbOF5 proved to be most satisfactory as the source of niobium. High yields and good metal-slag separations were obtained. Chemical analysis and density determinations showed the composition to be 10 ℗± 0.5 w/o niobium. Fifteen pounds of alloy were melted in BeO and cast into a graphite mold.

The niobium-uranium alloy is dissolved in hydrofluoric nitric acids and the fluoride removed by fuming sulfuric acid. The niobium is hydrolyzed in an acid-sulfur dioxide medium and converted to niobic oxide by ignition at 900 deg C. The method covers the determination of niobium in niobium-uranium alloys having a niobium content of 8 to 12%. Metals which hydrolyze readily in dilute acid solutions interfere with the determination. (auth).

Uranium-niobium alloys play an important role in the nation's nuclear stockpile. It is possible to chemically quantify this alloy at a micron scale by using a technique know as wavelength dispersive spectroscopy. This report documents how this technique was used and how it is possible to reproduce measurements of this type. Discussion regarding the accuracy and precision of the measurements, the development of standards, and the comparison of different ways to model the matrices are all presented.

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).

As a continuation of studies reported in BMI-1400, fabrication characteristics, physical and mechanical properties, and corrosion behavior in NaK, sodium, and water of niobium--uranium binary alloys containing up to 60 wt.% uranium were investigated. Alloys were cast by a skull melting and consumable and nonconsumable arc-melting methods. Fabrication difficulties with alloys containing greater than 25 wt.% uranium were related to coring-type microsegregation during casting. Tensile tests indicated 0.2% offset yield strengths of 16,880, 22,370 and 28,600 psi for niobium2000 deg F. Additional tensile data were obtained for alloys from 1600 to 2400 deg F. Stresses to produce minimum creep rates of 0.001, 0.01, and 0.1%/hr at 1600, 1800, and 2000 deg F were also determined. Both tensile and creep strengths were found to be sensitive to oxygen content. All alloys appeared compatible with NaK at 1600 deg F and with sodium at 1500 deg F. In 600 deg F water, most of the alloys tested exhibited negligible weight changes after 336 days' exposure. Weight changes were greater after 140 days' exposure to 680 deg F water, but corrosion rates were considered satisfactory for a clad fuel. The thermal and electrical conductivities of niobium are lowered by the addition of uranium, while the thermal-expansion characteristics are essentially unaffected. Recrystallization temperatures for 90% cold-reduced niobium-4.38, -14.3, -20, -25.0, and -30 wt.% uranium alloys are 2300, 2300, 2400, 2300, and 2200 deg F, respectively. No appreciable effect of oxygen contents ranging from 100 to 1000 ppm was observed on the composition limits of the gamma immiscibility gap in the niobium-- uranium system. (auth).