Ohio’s long troubled Davis-Besse nuclear plant is facing new technical problems, in addition to its economic issues. The U.S. Nuclear Regulatory Commission July 27 announced it has launched a “special inspection” at the plant.
The NRC said the site inspection “will focus on two separate issues: multiple diesel generator failures during testing and maintenance; and a complicated reactor trip on July 8.” The regulators have dispatched six inspectors to the plant.
The NRC said, “In the past 24 months, Davis-Besse experienced four failures of emergency diesel generators to operate in accordance with specifications during NRC-required testing and one failure of a station blackout diesel generator during maintenance. Davis-Besse has two emergency diesel generators, which would provide emergency power during the loss of offsite power, and one station blackout diesel generator, which would provide power in case both emergency diesel generators failed.”
Station blackout, the loss of offsite power, is a dangerous condition that threatens the ability of plant operators to shut down the reactor. That’s why the NRC requires a depth of diesel backup generators to provide station power in an emergency.
The NRC said that as it was planning to look into the diesel failures, “Davis-Besse experienced an unplanned reactor trip. During the plant’s response to the trip, certain pieces of equipment did not function as designed. Operators took action to address the equipment issues, and the reactor was shut down safely and placed in a stable condition. After making the necessary repairs, the reactor returned to power.” But the “complications” of the scram led the agency to add that to its special investigation.
A FirstEnergy Corp. spinoff, Energy Harbor Corp., runs the plant, but FirstEnergy dispatches its power and bids the plant into the PJM Interconnection wholesale markets. It has been unsuccessful in winning in those auctions.
Davis-Besse is an 894-MW Babcock & Wilcox pressurized water reactor located on Lake Erie. It began service in 1978. It is the same design as the two B&W Three Mile Island reactors near Harrisburg, Pa. On March 28, 1979, a stuck valve on TMI’s Unit 2 led to a meltdown and the plant has never operated since.
Davis-Besse had a precursor accident in September 1977, when a pilot operated relief valve on the pressurizer stuck open, forcing the reactor shut down. It was only operating at 9% power at the time.
Other notable accidents at the plant include:
*A 1985 loss of main feedwater pumps and an operator error tripped off the emergency feedwater pumps. The NRC eventually determined this was a “site area emergency.”
*A 2002 discovery of a hole in the reactor head from leaking borated water that eventually ate through some six inches of six inches of the carbon steel pressure vessel. The plant was closed for two years, the repairs cost some $600 million. The NRC determined that this was one of the worst reactor accidents in U.S. history and fined FirstEnergy $5 million, then the largest NRC fine. That incident led in 2006 to a “deferred prosecution agreement” with the U.S. Justice Department, which found that plant operators had provided the NRC with false information about their actions. That resulted in a $28 million settlement with the DOJ.
–Kennedy Maize