The CANDU TM 6 reactor system is contained within a post-tensioned concrete containment structure. The NewBrunswick Power (NBP) owned, Point Lepreau CANDU TM 6 Generating Station (PLGS) located in New Brunswick,Canada, has been in service since 1983. Investigations are being undertaken to evaluate the significance of any age-relateddegradation. Particularly, a survey is being conducted to assess the expected long term performance of the structure. Forpart of this survey, in-situ deformations that occur during normal reactor operation and a leak-rate test, for which thestructure is internally pressurized, are being measured.During the early life of the structure, deformations were measured using both embedded and surface mountedgauges on the concrete surfaces. The record shows that neither of these strategies provided results which can be used toevaluate the current stress conditions. A reason for this may be related to the type of instrumentation used.Subsequently, various types of commercially available instruments have been appraised for application at PLGS.Laboratory and in-situ tests on mechanical, vibrating wire and fibre-optic deformation measuring devices confirm that theaccuracy of the measurements can be expected to vary significantly between instrument types. In addition, for eachinstrument type, the instrument stiffness, the temperature and the manner in which the instrument is installed all stronglyinfluence output.Recently, three gauge types were retrofitted to the outside surfaces of the PLGS containment structure to provide afurther assessment of the usefulness of the instrumentation and, ultimately, the condition of the structure. Taking thedetermining factors of instrument type and environment into account, measurements were made during and following aleak-rate test. These tests have shown that all of the instrument types can be used to assess the condition of the structure. Itis shown that concrete containment structure is required to endure distortional stresses due to environmental conditions. Itis concluded that monitoring of deformations occurring in concrete containment structures during the leak-rate pressuretests as well as continuously over the period of their operating life is an essential element in a structural ageing managementprogram.
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