John Spears
Toronto Star
October 26, 2002

A safety defect discovered at the Darlington nuclear generating station in mid-August triggered a warning that the huge plant could have been pulled out of service during a summer of record electricity demand.

No shutdown was ordered, the plant continued to operate and the province’s lights stayed on. But the impact of the warning, which came after an employee happened to see a shaft of light shining through a hole into a supposedly steam-proof room containing vital safety equipment, highlighted Ontario’s shortage of electricity during peak demand periods.

Darlington is Ontario Power Generation’s second-biggest generating station, producing up to 3,524 megawatts of power at any given time. During the summer, the province was using up to 25,000 megawatts, of which up to 4,000 had to be imported.

The Independent Electricity Market Operator, also known as IMO, which runs the province’s power grid, had to ask consumers on four separate occasions this summer to curb their use of power because demand was outstripping supply.

One of those appeals was issued Aug. 12, the day after the safety problem was discovered at Darlington, throwing its continued operation temporarily into question.

Ontario Power Generation reported the safety problem within four hours to the Canadian Nuclear Safety Commission, or CNSC, according to John Earl, a spokesperson for Ontario Power Generation.

"We reported that, along with an action plan," Earl said. "We put forward in the plan how we wanted to monitor, identify and repair these openings."

The plan involved a commitment to inspect all 282 steam-proof rooms at the complex by Aug. 23 and repair all holes within four hours of finding them. Ontario Power Generation also alerted the IMO that Darlington might have to shut down.

"It was a possibility that they would have to remove some or all of the generation from service," IMO spokesperson Ted Gruetzner said in an interview yesterday. "It was a notification to say that we have this problem, that we’re speaking to the CNSC."

Earl said the safety commission had staff on the spot.

If the commission has deep concerns, it can order a nuclear-station operator to show cause why the station should not be shut down. No such order was issued in this case.

Ontario’s shortage of generating capacity has been well documented.

IMO chief Dave Goulding said last month the province is "kept alive by its neighbours" any time the temperature rises above 30 degrees because local generators can’t keep up with the demand.

But the lines that carry imported power were loaded to their limits during the summer. If Darlington had shut down, imports could not have been used to replace the output.

Gruetzner acknowledged that losing Darlington would have put severe pressure on the province’s electric grid, but declined to speculate whether blackouts would have occurred.

The full plant inspection prompted by the employee’s original discovery on Aug. 11 revealed "many more gaps beyond the license limit of 75 square centimetres," according to a CNSC report.

Darlington’s generators are driven by steam, which is heated by its nuclear reactors. Rooms containing important equipment must be steam-proof in case a steam vessel ruptures and spews scalding, wet vapour over the sensitive equipment.

A report filed with the CNSC says the gap in the steam-proof room was found during a "routine inspection."

But according to a transcript of a question and answer session before the commission last month, Darlington vice-president Dominic Iafrate gave a somewhat different account.

"It was due to a very alert operator who, on a Sunday afternoon, looked up and saw a little bit of light coming through that penetration and thought something was amiss," he said.

Some of the holes may have existed since the complex was built. The building in question has a corrugated steel roof and U-shaped gaps where it meets the top of the wall, and "these were not sealed," according to Iafrate.

Norman Rubin of Energy Probe said the incident highlights the dilemma created by reliance on nuclear power. When serious safety problems occur, regulators can be faced with throwing the electricity grid into disarray if they apply safety standards rigorously and order a shutdown.

He said the problem could have been discovered easily if OPG had ever performed the simple test of vacuuming air out of the rooms and checking whether air was leaking back in.