Faulty work blamed for Reactor shutdown

The generator marked its 50th day out of service recently, a period in which OPG has lost as much as $30 million in revenue. And one source at the plant says that substandard maintenance triggered the unexpected shutdown.

Unit 6 was pulled out of service March 1, when OPG said a warning indicated problems with a hydrogen cooling system in the generator's rotor. The rotor spins an array of powerful magnets; electricity is generated when the spinning magnetic field interacts with stationary wire coils, which are cooled by water.

When technicians started pulling the generator apart, they discovered the problem was not with the hydrogen cooling system, but more likely occurred in the water-cooling system, OPG spokesperson John Earl said.

Because of the huge electrical charges present in the generator, the water must be kept pure. Contaminants can cause electric currents to arc and short-circuit, damaging the reactor.

"In one area of the turbine generator they did find some debris," Earl said in an interview. "What the debris is is still under investigation."

But a source at the plant says questionable maintenance is responsible for the breakdown.

The source said welds inside the generator were smoothed coarsely with a wire brush that left metal shards inside the generator.

When the generator started, the metal shards triggered short-circuits and arcs that damaged the generator and forced the shutdown.

Nuclear units are designed to run non-stop except for scheduled maintenance periods. The current shutdown was not scheduled.

Had it been running at full capacity over the past 50 days, the unit would have produced 600,000 megawatt hours of power. At the March average price of $50 a megawatt hour (5 cents a kilowatt hour), the lost revenue to date comes to $30 million.

Even assuming a substandard performance of 80 per cent capacity, losing the generator for 50 days would have cost $24 million in lost revenue.

The loss of the unit, one of four at the Pickering B station, isn't causing power shortages because demand for electricity is low at this time of year.

OPG may have recouped some revenue by producing power from other sources, such as its coal-burning plants. But burning coal is more expensive than running a nuclear plant. And because of Ontario's competitive market, it's probable that privately owned generators stepped in to fill the void.

The generator continues to cost $600,000 a day in lost revenue as it sits idle. Earl said the repair work has been done and the generator is being reassembled, but the complex job will take more time. He said OPG used the generator's unexpected downtime for other maintenance work. OPG couldn't say recently how much it has spent to repair the damage.