Anisotropy of irradiation creep and growth of zirconium alloy pressure tubes

Abstract

Irradiation creep and growth anisotropy factors calculated from crystallographic texture and grain shape measurements, together with measured axial and transverse strain rates of zirconium alloy pressure tubes in CANDU ∗ ∗ CANada Deuterium Uranium. power reactors, have been used to calculate proportions of creep and growth. Using the irradiation creep and growth rates derived for cold drawn Zr-2.5%Nb and cold drawn Zircaloy-2 pressure tubes, we have defined ideal textures and grain shapes resulting in minimum axial and transverse strain rates. For the conditions of stress, temperature and fast neutron flux under which CANDU pressure tubes operate, proportions of growth are too small compared to the creep to get the ideal of zero axial and transverse strains. The closest approach to this ideal is when basal poles are in the radial/transverse plane, regardless of grain shape of alloy. The most favourable grain shape is plate shaped with the plates oriented in the axial/radial plane.