Irradiation Growth of Zircaloy

Abstract

Data on irradiation growth of Zircaloy is presented. Irradiation growth is defined as irradiation-induced changes in dimensions in the absence of an applied stress. It is shown that the primary variables are fluence, irradiation temperature, amount of prior cold work, heat treatment, and texture. For recrystallized Zircaloy: growth (a) increases as f, the fraction of basal poles in measurement direction, decreases; shrinkage is possible for large f-factors, (b) increases with increasing temperature up to about 300°C, above which it decreases, (c) tends towards saturation for fluences greater than about 1 × 1021 neutrons (n)/cm2(E> 1 MeV). For cold worked/ stress relieved material: growth (a) increases linearly with fluence up to at least 3 × 1021 n/cm2, and (b) increases linearly with increase in the amount of cold work. For recrystallized material, all irradiation growth is recovered during suitable thermal anneals, while for cold worked material only a portion of the growth is recoverable. Rapid recovery occurs above 350°C (644°F) with an activation energy of 1.67 eV. Mechanistic implications of the gathered data are discussed.