An Investigation for a Potential Hydride Volume Fraction Dependence on the Hydride Solvus in Zircaloy-4 Available to Purchase

Using hydrogen diffusion couples, Naval Nuclear Laboratory has further investigated the hydride solvus in Zircloy-4. Testing involved more than 100 samples experiencing diffusion anneals conducted over weeks to months under both steady-state and thermal-cycling conditions. Hydrogen concentrations of the diffusion couples following test exposures were determined by LECO analysis techniques. Testing was designed to examine for both the temperature dependence on the solvus and for any hydride volume fraction dependence that might exist on the solvus. The resulting data indicate that the dissolution solvus increases slightly as the hydride volume fraction increases. The apparent hydride volume fraction dependence is judged to result from an increasing self-stress imposed in the material as a result of increasing hydride precipitation.