Cracking of U--0.75 wt. % Ti in hydrogen and water vapor

The data obtained in this investigation have shown that the crack velocity of U-- 0.75 wt percent Ti in H2 has a linear dependence on time, an exponential dependence on temperature, a power dependence on pressure, and increases as the strength of the material increases. The H2 cracking data also exhibited an anomalous behavior wherein cracking occurred in the absence of an applied load. This is attributed to corrosion product wedging. UH3 has a density of 11 g/cm3 while the U--Ti alloy has a density of 18.5 g/cm3. This corresponds to an increase in volume of 70 percent when the hydride is formed. It is felt that the reaction of the fracture surface with the H2 environment leads tothe formation of copious amounts of hydride which interferes with the relaxation of the crack opening as the stress intensity is lowered. (U.S.)