Nuclear fuel cladding undergoes waterside corrosion during normal operating conditions
in pressurized water reactors, whereby the zirconium (Zr) in the fuel cladding
reacts with the oxygen present in water, creating zirconia (ZrO2) and releasing hydrogen.
Part of the hydrogen created by the corrosion reaction can be absorbed into the fuel
cladding. Once in the cladding, hydrogen redistributes by solid state diusion in the
metal, in response to gradients of concentration, temperature and stress. Once the local
hydrogen solubility is exceeded, zirconium hydride precipitates are formed.