A high-temperature longitudinal strain rate equation for Zr-2.5 wt% Nb pressure tubes

Abstract The pressure tubes in CANDU reactors are horizontal. Thus, if, during a postulated loss-of-coolant accident, the pressure tube temperature should rise sufficiently, the self-weight of the pressure tubes together with the weight of the fuel could cause the pressure tubes to sag. Since any pressure tube deformation would control how the core heat is transferred to the surrounding moderator, which is a large heat sink, the accurate prediction of this sag is essential. Most CANDU reactors have pressure tubes of cold-worked Zr-2.5 wt% Nb. A longitudinal strain rate equation was developed for this material using four-point bend tests. This strain rate equation was successful in predicting the longitudinal strain, due to bending, in specimens for which the temperature was ramped at 1°C/s and 5°C/s.