Modification of the Existing Yielding Creep Theory of Irradiation Creep in Zirconium and Zircaloy-2

The theory of yielding creep is modified to include a time dependence of irradiation growth. The predicted time dependence of irradiation creep is compared with the values measured in zirconium alloys by several workers. Good agreement is found for unhydrided Zircaloy. In hydrided Zircaloy we have to assume that the (unmeasured) irradiation growth rate increases with increasing hydrogen concentration.