Measurement and analysis of the elongation of Zircaloy-2 pressure tubes in pickering generating station units 1 and 2

Zirconium alloy components in the core of CANDU ∗ reactors change shape as a result of neutron irradiation. Dimensional changes in the pressure tubes of the reactors at the Pickering Generation Station have been measured as part of the general maintenance program carried out by Ontario Hydro. The techniques used to measure pressure tube elongation, and the results obtained for Pickering units 1 and 2 over the past six years, are presented. The data are interpreted using a detailed analysis which accounts for the manner in which the elongating pressure tubes interact with the calandria tubes and end shields of the reactor. The free elongation rate obtained from the analysis has been used, with other pressure tube data, to calculate the material dependent constants in the equations which define irradiation enhanced creep and growth in the cold-worked Zircaloy-2 pressure tubes of the Pickering unit 1 and 2 reactors.