An American Electric Power (NYSE:AEP) subsidiary has informed the Nuclear Regulatory Commission (NRC) that roughly 2,000 gallons of oil has leaked into Lake Michigan since late October from the D.C. Cook nuclear power station in Michigan.
“At 1212 EST on December 12, 2014, D.C. Cook notified the State of Michigan and local authorities of an oil leak from the Unit 2 Main Turbine Lube Oil Cooler to Lake Michigan,” according to an “event notification” report posted Dec. 22 by NRC.
“Approximately 2000 gallons have leaked into Lake Michigan since October 25, 2014. No visible oil or oil sheen is present on Lake Michigan or the shore line. The leak is currently isolated as of 1030 EST on December 20, 2014. Leak repairs will be made to the cooler prior to placing back in service,” according to the event report.
“The leak was isolated immediately upon discovery, repair plans are under development,” a plant spokesperson said early Dec. 22. “It’s not possible to determine exactly how much oil leaked or during what period. The 2,000 gallons is a projected calculation based on the as-found rate going back to an initial level decline indication on Oct. 25,” the spokesperson added.
Other federal agencies, including the Environmental Protection Agency (EPA) and the Federal Emergency Management Agency (FEMA) were also notified, according to the report.
The turbine lube oil system contains approximately 25,000 gallons of non-radioactive oil, the utility said in a statement later Dec. 22. The hot oil runs across tubes in a heat exchanger that is cooled by water from Lake Michigan. It is believed the oil leaked into a tube or tubes and was mixed into the cooling water. The leak, calculated at approximately 0.04 gallons per minute, could not be detected in the total water discharge flow of 1.5 million gallons per minute.
“We had been actively troubleshooting the level decline and closely monitoring our water discharge before we identified there actually was a leak and found the likely source,” said plant Environmental Manager Jon Harner. “Our searches haven’t detected any oil on the beach or in the lake. We’ll continue to monitor the situation.”
A repair plan is being developed and a formal causal analysis will be done. There are four coolers for the lube oil system so the unit can safely remain at full power.
D.C. Cook Units 1 and 2 are pressurized water reactors (PWRs) operated by AEP utility subsidiary Indiana Michigan Power. Both units are located in Bridgman, Mich., and were commissioned in the 1970s. Each unit has an operating capacity of more than 1,000 MW, according to GenerationHub data.
The utility is also involved in what it calls a “life-cycle management” program for the Cook units, which involves extensive capital spending on the nuclear station to better prepare it for its extending operating life.
In 2005, Cook received license renewals from NRC that will allow the two units to run to 2034 and 2037 respectively. That is an additional 20 years beyond their original licenses.