Canadian CANDU (Canadian Deuterium-Uranium) reactor refurbishment -- or re-construction -- costs skyrocketed dramatically over budget. CANDUs were expected to operate for 40 years. However, just 20 years into operations, significant age related degradation required extensive, and exorbitant, refurbishment of the reactors if they were to continue operating.
As documented by Pat McNamara in Nuclear Genocide in Canada:
AECL's claim that the CANDU reactors would last for 40 years had no basis in fact. The first CANDU reactor was shut down in 1983 at Pickering A after 12 years of service for re-tubing. All four of the Pickering A reactors were re-tubed over the following 10 years. In 1997, all four Pickering A and three of Bruce Powers reactors were shut down for accumulated safety problems and lack of reliability.
In 1999, Ontario Power Generation estimated it would cost $1.1 billion dollars and take three years to get all four Pickering A reactors back in service. Work commenced in 1999 to bring Unit 4 of Pickering 'A' back into service at a cost of $457 million. According to the Report of the Pickering 'A' Review Panel:
"In late September 2003, the first of four Pickering 'A' reactors returned to service. Compared with the plan approved by the Board of Directors of Ontario Power Generation (OPG) in August 1999, the cost of Unit 4's return to service had almost tripled, and the return to service date has slipped by more than two years."
The cost to repair Unit 4 was $800 million dollars over budget and two years late. They spent more money fixing one reactor than the original estimate for all four reactors. OPG went ahead and fixed Unit 1 at a cost of $1 billion. Due to the delays and massive cost overruns of the first two reactors, OPG decided to permanently shut down Units 3& 4.
Spending all this money on the reactors did little to improve their performance. In the summer of 2007, Units 1 & 4 were shut down for further repairs along with one other reactor from Pickering B. Combined with the two reactors on permanent shutdown, only three of the eight reactors were generating electricity all summer.
By 2005, Bruce Power restarted reactors 3 and 4 at a cost of $720 million, which was more than double their initial estimate of $340 million. They have since announced plans to refurbish four reactors by 2013 at a cost of $5.2 billion. They started working on the first two reactors in 2007. This part of the project was supposed to cost $2.5 billion but it is already 25% over budget.
In 2008, Hydro-Quebec announced plans to refurbish Gentilly 2 at a cost of $1.9 billion. This was $700 million more than the estimate when the project was first proposed in 2004.
In February 2009, AECL was given a $100 million subsidy to address cost overruns for refurbishments at Bruce Power and Point Lepreau. This came only two weeks after AECL was given $350 million dollars by the Canadian government as announced in the January 27, 2009 budget." (excerpt from Part 4, "Nuclear Costs to Date")