Conference Proceedings Paper
Life Extension of CANDU® Reactor Cores
9th International Conference on CANDU® Maintenance - 2011 December 04-06
Julian Millard (Candu Energy Inc.)
Jeff Kerker (Bruce Power)
Michael Albert (Candu Energy Inc.)
Candu Energy (AECL®), in partnership with station operators, has developed a robust methodology for demonstrating the fitness of reactor core structures and associated reactivity control devices as part of conducting a station life extension project. The ageing of reactors is affected by ageing mechanisms impacted by operational history and design related factors such as materials, chemistries and stress distributions. The methodology of this life extension work is based on the IAEA TECDOC 1197; which documents practices for ageing management in CANDU reactors. This paper uses the work in Bruce Units 1 and 2, conducted from 2007 through to 2011, to explain the methodology.
The work started with analysis of operational conditions along with what forms of degradation could have occurred. The assessment and related inspections considered the safety and pressure boundary significance of each item, as well as its failure modes and margins. It then moved through both general and local inspection, focused mainly inside the calandria vessel once the calandria tubes were removed. The inspection found the bulk of the hardware to be in good condition, with a small number of remediation opportunities. As part of that remediation some foreign material was sampled and removed. The minor remediation was completed and work was completed through formal documentation of the fitness for extended life.
It has been demonstrated through these analyses and visual inspections that the reactor structures and components inspected are free of indications and active degradation mechanisms that would prevent the safe and reliable operation of Bruce A Units 1 and 2 through its next 25 years of life.
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