Analysis of Pressure Tube Measured Data for CANDU Reactors

Abstract

Pressure tubes of CANDU reactor are deformed into the radial (diameter creep) and axial direction (elongation) due to the severe operational environments such as high temperatures, pressures and neutron irradiation during the reactor operation. Since the pressure tube deformation may affect the operational margin and reactor’s lifetime, it should be measured periodically. In this study, the measured data for the pressure tube were analyzed to understand the deformation behavior. The evaluation methodology for the pressure tube maximum diametral expansion and axial elongation was established based on the data analysis results. From the evaluation results, it was found that the diametral expansion of most pressure tubes were within the limiting value of diameter in terms of the critical heat flux experimental data base. A number of measured pressure tubes were found to exceed the data base limit. Axial elongation of most pressure tubes were found within the limits of the data base. But using a conservative methodology, which considers an increasing elongation rate as a function of operation time, some pressure tubes may be exceeding limits at the end of the reactor lifetime.