The Donald C. Cook Nuclear Power Plant near Bridgman, on the shores of Lake Michigan. (Photo: Indiana Michigan Power) 
 
 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. 
 
 Buy Photo (Photo: Detroit Free Press) 
 
 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. 
 
 Read or Share this story: http://on.freep.com/1I6Ppqb ||||| UPDATE: Story has been updated to include comment from Cook Nuclear Plant spokesman. 
 
 BRIDGMAN, MI -- Donald C. Cook Nuclear Plant in Bridgman has leaked an estimated 2,000 gallons of oil into Lake Michigan since Oct. 25, according to an event notification posted on the Nuclear Regulatory Commission website. 
 
 
 
 
 
 Plant officials notified the NRC, plus state and local officials, on Dec. 20 about the leak, which is from the Unit 2 main turbine lube oil cooler. 
 
 The notification said that "no visible oil or oil sheen is present on Lake Michigan or the shore line." 
 
 The leak was isolated as of 10:30 a.m. Dec. 20, the notice said. "Leak repairs will be made to the cooler prior to placing back in service." 
 
 Plant officials notified federal, state and local officials as soon as they realized there was a leak, said Bill Schalk, the spokesman for Cook. 
 
 He said the company noticed a slight drop in its oil levels starting on Oct. 26, but "there are lots of things that can cause that." 
 
 In addition, the plant was taken offline for two days at the end of October after excessive debris from large waves from Lake Michigan damaged several water screens. 
 
 "Because of that, we didn't have a good steady stream of date to recognize that we were losing (oil)," Schalk said. 
 
 It wasn't until Dec. 16 that it was determined a leak might exist and on Dec. 19, it was traced to one of four heat-exchange tanks, where hot oil runs through hundreds of tubes and is cooled by lake water in the tank. 
 
 "We've shut off that tank, and now we need to develop a plan to find the leak," he said. 
 
 The oil was leaking at a rate of about a third of cup, or 5 ounces, an hour into the plant's lake-water discharge of 1.5 million gallons an hour. 
 
 "We take samples of lake water every day, but the leak was small enough that we didn't pick it up," Schalk said. 
 
 The estimate of 2,000 gallons of oil leakage overall is based on a calculation that the leak began Oct. 26. 
 
 "That the worse-case scenario," he said. "It wouldn't be more than that, and it's probably less." 
 
 The incident has not affected the plant's electrical production, Schalk said, and the leak was small enough that there is no cleanup involved. 
 
 "We just need to fix the tank and make sure it doesn't happen again," he said. 
 
 In August, plant officials issued a report that 8,700 gallons of diesel fuel were suspected to have been released from a buried fuel oil tank, but later said there was no leak and the report resulted from "instrumentation error." 
 
 The plant is located near Bridgman, 11 miles south of St. Joseph along the Lake Michigan shoreline. Unit 2 went into operation in 1978. 
 
 The plant is owned by American Electric Power and operated by Indiana Michigan Power, an AEP subsidiary. 
 
 Julie Mack covers K-12 education and writes a column for Kalamazoo Gazette. Email her at jmack1@mlive.com, call her at 269-350-0277 or follow her on Twitter at @kzjuliemack.
– A nuclear plant leaked oil into Lake Michigan for almost two months, and although the oil wasn't contaminated with radiation, safety groups are alarmed by how long it took the plant to spot the leak. Officials at the Donald C. Cook Nuclear Plant in southwest Michigan reported the problem to federal authorities on Dec. 20, estimating around 2,000 gallons of oil leaked into the lake starting in late October, reports the Detroit Free Press. Plant officials say the oil leaked from a cooling system at the rate of around 0.04 gallons per minute, which made the leak tough to detect amid water discharge of 1.5 million gallons of water per minute. "We take samples of lake water every day, but the leak was small enough that we didn't pick it up," a plant spokesman tells MLive.com, explaining that factors including a huge storm at the end of October made it harder to monitor oil flow. The estimate of 2,000 gallons of leakage is a "worst-case scenario" and the true figure is probably less, he says. The director of the Coalition for a Nuclear-Free Great Lakes doesn't find that reassuring. "What's concerning is they don't really know the extent of the leak," he tells the Free Press. "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."