Effects of texture and temperature cycling on irradiation growth in cold-worked zircaloy-2 at 353 and 553 K

Abstract

Irradiation growth and temperature cycling experiments have been performed at 353 and 553 K on specimens taken from both longitudinal and transverse direction of 25% cold-worked zircaloy-2 pressure tube. For the longitudinal data, significant positive strains occur below a dose of 10 24 n/m 2 at both temperatures, the larger strains occurring at the lower temperature. Above this dose, longitudinal growth strains increase almost linearly with irradiation. The linear rate is greater at 553 than 353 K. In transverse specimens, a small positive transient strain occurs below a dose of 10 24 n/m 2 and negative growth rates are observed above this dose. It is suggested that the transient low dose growth behaviour at 353 and 553 K contains a substantial fraction of volume increase. The effects of changes in irradiation temperature on growth strains in cold-worked zircaloy-2 have been studied. Lowering kradiation temperature produces an initial positive transient strain which is almost fully recovered on raising the temperature again. Growth data obtained on longitudinal specimens cycled between 353 and 553 K during irradiation lends strong support to a model of growth for cold worked zircaloy-2 which consists of a transient recoverable growth component due to interstitial clustering on prism planes and a non-recoverable linear component due to interstitial induced dislocation climb.