Irradiation Creep of Zr-Alloys

Irradiation creep of Zr-alloy nuclear reactor core components affects the reactor performance and also limits the reactor life in cases where those components cannot easily be replaced. For Zr-2.5Nb pressure tubing irradiation creep has been extensively studied for a range of temperatures, between 250 and 350 degrees C, and dose rates, between 1 x 10(16) and 2 x 10(18) n m(-2) s(-1) (E > 1 meV), using data from various materials test reactors and power reactors. These studies have shown that irradiation creep is controlled by a complex combination of slip and diffusional mass transport (often referred to as irradiation growth in the absence of stress). Irradiation creep is dependent on the crystallographic texture, the dislocation structure, and the grain structure; the importance of each being a function of irradiation temperature and displacement damage rate. Data will be presented, together with mechanistic modelling, to show what factors affect creep under different irradiation conditions.