Ohio: Pinhole leak of radioactive coolant found at the Davis-Besse nuclear power plant

View full sizePlain Dealer fileVapor from cooling tower at The Davis Besse nuclear power plant billows over farmland along Rt. 2 in Oak Harbor, Ohio, in January.

By John Funk Plain Dealer Reporter

Engineers at the Davis-Besse nuclear reactor near Toledo found a pinhole coolant leak in a pipe weld Wednesday evening while inspecting the plant.

Davis-Besse was preparing to resume operations after more than a month-long reactor shutdown for refueling and plant maintenance.

In a report early Thursday to the Nuclear Regulatory Commission, plant owner FirstEnergy Corp. estimated the leak of radioactive coolant inside the reactor containment building at about one-tenth gallon per minute.

Spokeswoman Jennifer Young said the leaked coolant flowed into a nearby floor drain and was captured for later processing. There were no injuries and no radioactivity escaped into the atmosphere, she said.

The leak did not occur until the cooling system was pressurized in preparation to restart the reactor, she said. Pressurization began on Tuesday.

The engineers were conducting the “walk-down inspection” while the reactor was in “hot standby” mode, with the cooling system running at normal operating pressures and temperatures.

Through the reactor had not yet been re-started, operators on Tuesday had switched on the four massive reactor coolant pumps, which pressurized the system and heated the coolant to about 300 degrees from sheer friction as the pumps pushed it throughout the nuclear core, said Young.

The company’s report to the NRC noted that the coolant was spraying from a pinhole in the socket weld of a three-quarter inch pipe at a 90 degree elbow between a reactor coolant pump and a safety valve.

When the leak was spotted, reactor operators immediately began a shutdown and engineers began repair preparations. The plant reached cold shutdown about 1 p.m. Thursday, said Young. Repairs were expected to be completed over the weekend.

FirstEnergy shut down the 908-megawatt reactor on May 6 for normal refueling, inspections and maintenance. Contractors employing more than 1,000 workers joined Davis-Besse employees to replace 68 of the reactor’s 177 fuel rods.

Contractors also were involved with preventative maintenance of major components including emergency diesel generators, valves and pumps — though not the coolant pumps and plumbing where the leak occurred. Crews also worked on the power plant’s cooling tower to improve efficiency.

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