On Thursday afternoon, the Davis-Besse nuclear power plant in Ohio lost its Safety Parameter Display System (SPDS) during a failure of the plant’s hard drive. According to the Event Report submitted to the NRC, data from the SPDS “was not available in the Control Room or in the emergency response facilities.” A second system, the Emergency Response Data System, remained available. However, the plant had to do “dose assessment using manual inputs” during the time the SPDS was down.
At a little past 9 pm, operators restored the SPDS. Since the anomaly took just under eight hours to correct, Davis-Besse will probably retract the Event Report, since the requirement to report is in effect if the problem takes more than eight hours to repair. Despite the probable retraction, this remains a significant amount of time to be without a key safety system.
The Davis-Besse nuclear plant has had significant safety problems since it opened.
In 1977, a valve in the reactor’s feedwater system became stuck in the open position. (Through 2005, the NRC still considered this the fourth worst nuclear safety incident in the U.S.)
In 1985, operator error caused a loss of feedwater incident. Although initially classified as an Unusual Event, a subsequent NRC review upgraded the incident to a Site Area Emergency.
In 1998, a tornado struck the Davis-Besse switchyard, resulting in a loss of offsite power.
In 2002, plant operaters discovered that a boric acid leak had corroded a football-sized segment of the reactor vessel head, leaving less than half an inch of metal standing between the plant and a reactor vessel breach. Davis-Besse procurred a replacement vessel head from an abandoned nuclear project in Michigan. (More about that in a minute.)
In 2003, the plant lost safety equipment for five hours when the Slammer worm infected its computer system.
In 2006, three former employees were indicted for making false statements in the investigation of the boric acid corrosion.
In 2008, the plant reported tritium leaks to the NRC.
In 2010, the replacement reactor vessel head obtained from Michigan was found to have cracks in 24 of 69 control rod drive mechanism nozzles.
And in 2011, a 30-foot crack was discovered in the reactor’s concrete containment building.