Determination of terminal solid solubility of hydrogen in zirconium alloys

Zirconium alloys are widely used as the material for the fuel cladding and the structural components of nuclear power plants. Hydrides in zirconium alloys is a major parameter in assessing the potential for delayed hydride cracking in the embrittlement of fuel cladding and other structural components. Many studies on the measurements of TSSD during heating and TSSP during cooling have been carried out for Zr and its alloys, and various measuring techniques have been used. However, there is considerable scatter in the published TSS data. This may be attributed partly to the different experimental techniques used such as diffusion gradient, dilatometry, differential scanning calorimetry, dynamic elastic modulus, and so on. In this study, TSSD and TSSP of commercial Zircaloy-4 and advanced zirconium alloy which were hydrogenated up to a level of 225 ppm, were derived by differential scanning calorimetry (DSC), and best fit equations were presented. Moreover, the average precipitation rates of zirconium hydrides from the super-saturated state were assessed from the widths of the DSC peak obtained during cooldown