Experimental determination of zirconium hydride precipitation and dissolution in zirconium alloy

Synchrotron X-Ray transmission diffraction experiments were performed to study hydride precipitation and dissolution in the zirconium/zirconium-hydride system while it occurs. Evidence was found that the hysteresis between the terminal solid solubility for precipitation and dissolution is not observed when hydride particles are already present at the beginning of sample cooldown. Furthermore, experimental results show that, during a temperature hold, the concentration of hydrogen in solid solution becomes lower than the terminal solid solubility for hydride precipitation and eventually reaches the terminal solid solubility for hydride dissolution, indicating that the latter is the actual thermodynamic solubility limit.