All of the 380 new calandria tubes installed as part of the major ongoing refurbishment of the Point Lepreau Candu-6 nuclear power plant in Canada are to be removed and reinstalled.
|Point Lepreau (Image: NB Power)
NB Power, operator of the 635 MWe Candu 6 reactor in the province of New Brunswick, issued a brief note confirming that refurbishment contractor Atomic Energy of Canada Ltd (AECL) had begun work on the removal of the 380 tubes.
Point Lepreau is the first Candu 6 unit to undergo major refurbishment, involving replacement of all calandria tubes, steam generators and instrument and control systems. Work began in April 2008 and was originally expected to be complete by late 2009. The project should ensure an operating life until at least 2034 for the plant, as well as a 25 MWe power uprate, but is now the subject of political fighting with the province of New Brunswick seeking federal mediation over the issue of cost overruns.
Replacement of the calandria tubes, which form channels in which uranium fuel is inserted and through which the heavy water moderator flows in the core of the reactor, has turned out to be one of the most complex aspects of the entire project. Insertion of the 380 tubes was completed in April 2010, but AECL subsequently reported that it was encountering problems with producing consistently tight seals in the tubes. An insert at the end of each tube must be rolled and tested, but as of June 2010 AECL reported that only 421 of the 760 inserts had been tested successfully. AECL had been working to address the issue by removing roughness on some tube join surfaces as well as using metal inserts to reach the proper tightness.
The likely impact of the decision to remove all the tubes on the overall schedule is not yet known, according to NB Power.
Researched and written
by World Nuclear News