An Ontario nuclear station has still not implemented one of the key safety recommendations resulting from the massive blackout that blanketed much of northeastern North America in 2003, Canada's nuclear watchdog says.

When the blackout hit, operators had problems shutting down the reactors at the Pickering B station because there was no backup power to operate the cooling system. The reactor had to be cooled by convection — letting cool water dilute the warm water inside the tubes.

A report for the Conservative government of Ernie Eves recommended that large natural gas-fired generators be built at the station, east of Toronto, to run the cooling system and ensure the reactor wouldn't overheat if there were another big blackout.

But nearly three years after the blackout, the work has yet to be completed.

Until the gas-fired generators are constructed, the Canadian Nuclear Safety Commission says, the Pickering B site will not meet its standards.

A spokesperson for Ontario Power Generation, which owns the plant, said a temporary generator was installed shortly after the blackout, but permanent backup power will not be finished until next year.

The commission also found some problems at Ontario's Bruce and Darlington nuclear stations, but said overall Ontario's nuclear plants operated safely last year.