Monday, January 14, 2008

Davis-Besse workers find small coolant leak

January 08, 2008

Workers reinforcing a pipe weld at the Davis-Besse nuclear power plant have discovered a small leak of reactor coolant coming from a crack in the weld.

The seepage is on a pipe joint inside the reactor containment building, and no radioactivity has leaked into the environment.

In a report released Monday morning by the Nuclear Regulatory Commission, plant owner FirstEnergy Corp. said a welder discovered the seepage in the weld joint of a 12-inch stainless-steel pipe early Friday.

The corrosion-resistant pipe carries radioactive coolant to an outside cooling system when the reactor is not operating.

FirstEnergy shut down Davis-Besse on Dec. 30 to meet an NRC deadline that it inspect and reinforce pipe welds in 2007. The normal refueling shutdown would have occurred in February.

Welds on joints connecting stainless steel piping have cracked at other power plants, and the agency issued a safety bulletin early last year requiring reinforcing overlays of an alloy material.

The weld in question was not leaking before workers began adding the overlay, said FirstEnergy spokesman Todd Schneider. He said it had been visually inspected in previous years during routine walk-downs of the reactor containment building.

Engineers are now doing an ultrasonic inspection of the cracked weld to determine the size and shape of the crack, said Davis-Besse spokeswoman Marla Lark-Landis. She said workers will add reinforcing overlays to the welds of 15 other pipe joints, as required by the NRC

Repair of the cracked weld will be done after crews unload the fuel rods from the reactor's core into a nearby cooling pool, she said.

All fuel rods are typically off-loaded during refueling, even though only about a third of the fuel rods are replaced, she said.

The company did not provide an estimate of how long the weld repairs would take.

Davis-Besse is about 25 miles east of Toledo and generates 898 megawatts of power.

It has operated safely since 2004 after a two-year NRC shutdown for severe corrosion problems and numerous design flaws in key safety and emergency systems.

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