The corrosion of Zircaloy in water reactors is dependent on the water chemistry of the primary coolant and the fast neutron flux.

Under standard pressurized water reactor (PWR) coolant conditions with hydrogen overpressure, resulting in a low oxygen content in the primary coolant, the fast neutron flux has no measurable influence on the corrosion rate. Therefore, the in-pile corrosion almost follows the out-of-pile behavior. However, in some cases deviations from this general behavior have been observed. Under oxygenated coolant conditions, typically for boiling water reactors (BWRs), the corrosion is enhanced by the fast neutron flux from the early beginning. Three different types of oxide have been observed.

The dimensional behavior of Zircaloy under irradiation is governed by two processes: creep and growth. Creep is dependent on fast neutron flux and saturates with time. Total growth results from irradiation growth, anisotropic creep, and mechanical interference. Both in-pile creep and growth depend on the amount in recrystallization of the material.