ROLE OF INTERNAL-STRESSES IN THE TRANSIENT OF IRRADIATION GROWTH OF ZIRCALOY-2

A ''self-consistent'' polycrystalline model is used to simulate irradi ation growth of Zircaloy-2 samples irradiated at about 330 K. The pred ictions of the model are compared with experimental measurements obtai ned from specimens irradiated in the Advanced Test Reactor (ATR) at Id aho Falls. Three types of material are studied here, i.e, annealed, co ld worked in tension and cold worked by rolling. In general, the growt h rate attains a steady state value after it goes through a transient that depends on the initial state of the material. The transient growt h behaviour is explained in terms of the evolution of intergranular re sidual stresses that are present in the sample, and in terms of the di slocation structure. From this study, information regarding irradiatio n creep and growth mechanisms occurring at the single crystal level is obtained.