Primary in-reactor creep of Zircaloy-2 exhibits approximately linear plots of log(creep strain, ϵ) against log (test time, t) that fit relations of the type ϵ = βt^m. For longitudinal specimens of cold-worked Zircaloy-2 at about 570 K, neutron flux of 1 × 10¹⁷ n m^-2 s^-1 (E > 1 MeV) and stresses σ below 310 MPa, the parameters β and m are given by β = (1.5 × 10^-5) exp[(1.055 × 10^-2)σ] and m = 0.24 + (4.5 × 10^-4)σ Increasing the neutron flux from 1 to 3 × 10¹⁷ n m^-2 s^-1 or temperature from 490 to 620 K increases the value of β but has little effect on the time exponent m.

Primary creep of annealed Zircaloy-2 at temperatures between 470 and 570 K shows an abrupt decrease in the time exponent after about 10 h. Irradiation before stressing decreases primary creep strain of annealed and of cold-worked Zircaloy-2 at stresses above 300 MPa, but slightly increases primary creep of cold-worked Zircaloy-2 below about 200 MPa.