Nuke plant reports 2-month oil leak into Lake Michigan

An oil cooling system on the turbine of a southwest Michigan nuclear power plant leaked oil into Lake Michigan for about two months, according to plant officials.

Officials with the Donald C. Cook Nuclear Plant near Bridgman reported the leak to the U.S. Nuclear Regulatory Commission, as well as state and local authorities, on Dec. 20, according to an event notification posted on the NRC's website. Plant officials believe 2,000 gallons of oil leaked into the lake, and a retroactive examination of system oil levels leads plant personnel to believe the leak may have been ongoing since about Oct. 25, said Bill Schalk, communications manager for the Cook Nuclear Plant.

"One of the first things we did when we looked at the potential for a leak is examine the lake," he said. "Oil floats on top of the water and you see a sheen, but we could find no evidence of oil in our reservoirs, in the lake or on the beach. It has been dispersed."

The leak involved an oil cooling system on the two-turbine plant's Unit 2 main turbine. The series of tubes runs in a heat exchanger where hot oil is cooled by water from Lake Michigan. It's believed the oil leaked into a tube or tubes and was mixed into the cooling water, Schalk said. The turbine system is separate from the plant's radioactive facilities, so the leaked oil is not contaminated with radiation, he said.

Plant officials extrapolate that the oil leaked at about 0.04 gallons per minute, which did not allow detection in the total water discharge flow of 1.5 million gallons of water per minute, Schalk said.

It took time to identify the existence of a leak because a variety of factors can account for changes in oil levels in the system, he said, including lake temperatures and the fact that the plant temporarily shut down on Nov. 1 due to storms in the region.

"About a day and a half from when we really believed in earnest there could be a leak, we discovered it" on Dec. 20, Schalk said.

The exact location of the leak has not yet been determined, but workers isolated the cooling system tank in which the leak is occurring, he said.

"We won't return that tank to service until we are certain we have found the leak, and there is no more potential for leaking," Schalk said.

Three other tanks also cool turbine lubrication oil at the plant, so it is able to continue operating at full power, he said.

The Berrien County Sheriff's Department's Office of Emergency Management, Michigan Department of Environmental Quality, the U.S. Environmental Protection Agency and NRC were all notified of the leak, Schalk said.

The Cook Nuclear Plant is operated by Indiana Michigan Power Co., a unit of American Electric Power headquartered in Columbus, Ohio. Its two nuclear power units have operated since 1975 and 1978 respectively, and together generate more than 2,150 megawatts of power, enough electricity for 1.5 million average homes, according to the plant's website. NRC licenses for plant operation expire in 2034 for Unit 1; 2037 for Unit 2.

Both the DEQ and EPA will require follow-up reports on the oil leak within the next month, Schalk said.

Michael Keegan, director of the nonprofit Coalition for a Nuclear-Free Great Lakes, is troubled by news of the leak.

"What's concerning is they don't really know the extent of the leak," he said. "Nearly two months later is the first determination they make that they have an oil leak? It speaks to the quality assurance of all of their other systems."

The fact that the oil is not recoverable is also problematic, Keegan said.

"There's a belief some have that the solution to pollution is dilution. It's not," he said.

Contact Keith Matheny: 313-222-5021 or kmatheny@freepress.com. Follow on Twitter @keithmatheny