August, 14, 2012
MINNEAPOLIS– Operators shut down Monticello Nuclear Generating Plant to repair a gasket on a pipe flange, while in an unrelated action Tuesday, operators at Prairie Island Nuclear Generating Plant shut down Unit 1 to repair two diesel generators.
Both shutdowns were accomplished safely. Neither resulted in a radiological release, nor did they pose any danger to members of the public or plant employees.
The Monticello reactor had been operating at 10 percent power since the weekend, as workers investigated leakage to a collection point inside the plant’s steel and steel-reinforced concrete containment structure. All of the leakage was contained within the containment structure. The investigation identified a gasket on a pipe flange needed repairs, and the plant was shut down to complete the work.
At Prairie Island, operators determined during testing that both Unit 1 emergency diesel generators had exhaust leaks. The plant has additional layers of backup protection, including other diesel generators, turbine-driven pumps and portable pumps.
Whenever a generating unit is in an outage, Xcel Energy purchases electricity from the Midwest Independent Transmission System Operator or other utilities or increases production at its other generating plants to ensure an adequate power supply for customers.
The 600-megawatt Monticello plant and the 550-megawatt Prairie Island unit will be restarted as soon as repairs are complete. Neither outage is expected to be lengthy. Prairie Island Unit 2, also a 550-megawatt unit, continues to operate at full power.
Xcel Energy Media Relations
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