TORONTO--Facing a $1.6-billion repair bill, the government of Ontario decided last week to mothball two 540-megawatt Canada Deuterium-Uranium (CANDU) nuclear reactors more than a decade before their projected retirement date. The decision could be a mortal blow for the domestically engineered reactors, whose unique design allows them to be refueled without going off-line.
The reactors, manufactured by the government-owned Atomic Energy of Canada Limited (AECL), are two of eight located at the Pickering Nuclear Station in the Toronto area. Built in the 1970s, they've been idled since 1997 largely because of thinning in the hundreds of pipes carrying heavy water coolant from the reactor core. Two years ago, three other laid-up Ontario reactors were restarted after refurbishments costing billions of dollars, and their operators now say more repairs are not far off. Some 34 large commercial versions have been built and installed around the world, including 20 in Ontario.
Experts point to the corrosive effect of the heavy water coolant as a major culprit, with the reactor's design contributing to the large repair bills. "Just getting at the pipes is fantastically difficult, dangerous, and expensive," says Frank Greening, former head of nuclear cooling systems analysis at Ontario Power Generation (OPG), the government utility that owns all of Ontario's CANDUs. Even for reactors where the coolant feeder pipes haven't yet deteriorated, says John Luxat, president of the Canadian Nuclear Society and OPG's former head of nuclear safety, "the costs of demonstrating [their safety] are becoming a problem."
Ken Petrunik, AECL's chief operating officer, says the CANDUs, which cost about $1.5 billion new, "perform well in their early years" and that their ability to refuel on-line has yielded "better performance results than any other reactor type in the world." He downplays the impact of Ontario's decision to mothball two reactors by noting that AECL is only weeks away from launching a sales campaign for an advanced version of the CANDU reactor that will compete with new designs from other countries (Science, 19 August, p. 1168).
Still, CANDU's future seems dim. In January the reactor company's U.S. partner, Dominion Resources of Richmond, Virginia, decided to abandon plans to seek a U.S. license for its next-generation CANDU. And in May, Chinese authorities announced that they weren't interested in buying any units beyond the two 700-megawatt units already operating near Shanghai.
More on the CANDU reactors