|Posted by George Freund on June 10, 2012 at 7:50 AM|
Davis-Besse nuclear plant workers on Thursday were investigating what caused a pinhole-size leak found the previous evening spraying radioactive coolant, plant operators said.
Regulators and plant operators said the leaking coolant at the plant on Lake Erie near Toledo never got outside the building and posed no safety or health threat to the public.
It's not clear how much coolant spilled out because it drained into the plant's collection system that is designed to contain any leaks, said Jennifer Young, a spokeswoman for the plant operated by a subsidiary of FirstEnergy Corp.
Workers discovered the leak in a pipe weld Wednesday night as they were getting ready to restart the reactor after a monthlong maintenance shut down. The plant was at full pressure at the time but the reactor was not yet operating, Young said. It's not known exactly when the leak began, but it had been less than 24 hours, she said.
Such leaks are not uncommon, said Viktoria Mitlyng, a spokeswoman for the U.S. Nuclear Regulatory Commission. She said nuclear plants go through an extensive startup process after outages to look for problems. The leak Wednesday will be repaired, plant operators said.
Nuclear regulators are expected to decide next year whether to renew the plant's license. Several anti-nuclear groups have charged that the plant is unsafe and should not continue to operate.
The 35-year-old plant was shut down in the fall while its reactor head was replaced. At that time, crews found cracks in the outer concrete wall that's designed to protect the reactor. FirstEnergy said a lack of exterior weatherproof coating caused the concrete to crack and traced the cracks back to a 1978 blizzard when wind, rain and a drastic temperature drop caused moisture to penetrate the concrete.
Federal regulators allowed the plant to resume electricity generation in December after determining it could operate safely and didn't need repair.
The plant also was shut down from 2002 to 2004 because of an acid leak in a reactor head. Regulators fined Akron-based FirstEnergy $5.45 million and the company agreed to $28 million in civil penalties following what the Nuclear Regulatory Commission said was the most extensive corrosion ever found at a U.S. nuclear reactor.
At full power, Davis-Besse makes enough electricity for around 750,000 customers, primarily in Ohio.
You see it was the monitoring equipment. The equipment duly reported a 'pin hole' sized leak at Davis Besse Nuclear Plant. Recordings went off the scale. The bloggers reported this wasn't the first time. The monitoring agency blamed the equipment and turned it OFF! It appears it wasn't the monitor. It was the nuclear power plant. Davis Besse has a long history of problems.
According to the NRC, Davis-Besse has been the source of two of the top five most dangerous nuclear incidents in the United States since 1979.
On March 5, 2002, maintenance workers discovered that corrosion had eaten a football-sized hole into the reactor vessel head of the Davis-Besse plant. Although the corrosion did not lead to an accident, this was considered to be a serious nuclear safety incident. The Nuclear Regulatory Commission kept Davis-Besse shut down until March 2004, so that FirstEnergy was able to perform all the necessary maintenance for safe operations. The NRC imposed its largest fine ever -- more than $5 million -- against FirstEnergy for the actions that led to the corrosion. The company paid an additional $28 million in fines under a settlement with the U.S. Department of Justice.
1977 first stuck-open pilot-operated relief valve
On September 24, 1977, the reactor, running at only 9% power, shut down because of a disruption in the feedwater system. This caused the relief valve for the pressurizer to stick open. As of 2005, the NRC considers this to be the fourth highest ranked safety incident.
1985 loss of feedwater event
On June 9, 1985, the main feedwater pumps, used to supply water to the reactor steam generators, shut down. A control room operator then attempted to start the auxiliary (emergency) feedwater pumps. These pumps both tripped on overspeed conditions because of operator error. This incident was originally classified an "unusual event" (the lowest classification the NRC uses) but it was later determined that it should have been classified a "site area emergency".
On June 24, 1998 the station was struck by an F2 tornado. The plant's switchyard was damaged and access to external power was disabled. The plant's reactor automatically shut down at 8:43 pm and an alert (the next to lowest of four levels of severity) was declared at 9:18 pm. The plant's emergency diesel generators powered critical facility safety systems until external power could be restored.
Erosion of the 6-inch-thick (150 mm) carbon steel reactor head, caused by a persistent leak of borated water.
2002 reactor head hole
In March 2002, plant staff discovered that the borated water that serves as the reactor coolant had leaked from cracked control rod drive mechanisms directly above the reactor and eaten through more than six inches (150 mm) of the carbon steel reactor pressure vessel head over an area roughly the size of a football (see photo). This significant reactor head wastage on the interior of the reactor vessel head left only 3⁄8 inches (9.5 mm) of stainless steel cladding holding back the high-pressure (~2500 psi, 17 MPa) reactor coolant. A breach most likely would have resulted in a mass loss-of-coolant accident, in which superheated, superpressurized reactor coolant would have jetted into the reactor's containment building and resulted in emergency safety procedures to protect from core damage or meltdown. Because of the location of the reactor head damage, such a jet of reactor coolant might have damaged adjacent control rod drive mechanisms, hampering or preventing reactor shut-down. As part of the system reviews following the accident, significant safety issues were identified with other critical plant components, including the following:
the containment sump that allows the reactor coolant to be reclaimed and reinjected into the reactor;
the high pressure injection pumps that would reinject such reclaimed reactor coolant;
the emergency diesel generator system;
the containment air coolers that would remove heat from the containment building;
reactor coolant isolation valves; and
the plant's electrical distribution system.
The resulting corrective operational and system reviews and engineering changes took two years. Repairs and upgrades cost $600 million, and the Davis-Besse reactor was restarted in March 2004.
The U.S. Justice Department investigated and penalized the owner of the plant over safety and reporting violations related to the incident. The company paid $28 million in fines under a settlement with the U.S. Department of Justice. The NRC determined that this incident was the fifth most dangerous nuclear incident in the United States since 1979. The NRC imposed its largest fine ever -- more than $5 million -- against FirstEnergy for the actions that led to the corrosion.
2003 Slammer worm
In January of 2003 the private network became infected with the slammer worm, which resulted in a five hour loss of safety monitoring at the plant 
2006 Criminal prosecutions
On January 20, 2006, the owner of Davis-Besse, FirstEnergy Corporation of Akron, Ohio, acknowledged a series of safety violations by former workers, and entered into a deferred prosecution agreement with the U.S. Department of Justice. The deferred prosecution agreement relates to the March 2002 incident (see above). The deferment granted by the NRC were based on letters from Davis-Besse engineers stating that previous inspections were adequate. However, those inspections were not as thorough as the company suggested, and as proved by the material deficiency discovered later. In any case, because FirstEnergy cooperated with investigators on the matter, they were able to avoid more serious penalties. Therefore, the company agreed to pay fines of $23.7 million, with an additional $4.3 million to be contributed to various groups, including the National Park Service, the U.S. Fish and Wildlife Service, Habitat for Humanity, and the University of Toledo as well as to pay some costs related to the federal investigation.
Two former employees and one former contractor were indicted for statements made in multiple documents and one videotape, over several years, for hiding evidence that the reactor pressure vessel was being corroded by boric acid. The maximum penalty for the three is 25 years in prison. The indictment mentions that other employees also provided false information to inspectors, but does not name them.
2008 discovery tritium leak
The NRC and Ohio EPA were notified of a tritium leak accidentally discovered during an unrelated fire inspection on October 22, 2008. Preliminary indications suggest radioactive water did not infiltrate groundwater outside plant boundaries.
2010 Replacement reactor head problems
After the 2002 incident, Davis-Besse purchased a used replacement head from a mothballed reactor in Midland, Michigan. Davis-Besse operators replaced the original corroded reactor head before restarting in 2004. On March 12, 2010, during a scheduled refueling outage, ultrasonic examinations performed on the control rod drive mechanism nozzles penetrating the reactor vessel closure head identified that two of the nozzles inspected did not meet acceptance criteria. FirstEnergy investigators subsequently found new cracks in 24 of 69 nozzles, including one serious enough to leak boric acid. Root cause analysis is currently underway by the Department of Energy, First Energy, and the NRC to determine the cause of the premature failures.  Crack indications required repair prior to returning the vessel head to service. Control rod drive nozzles were repaired using techniques proven at other nuclear facilities. The plant resumed operation in 2010. The existing reactor vessel head was scheduled for replacement in 2011.
2011 Shield Building cracks
An October 2011 shutdown of the plant for maintenance revealed a 30 foot long hairline crack in the concrete shield building around the reactor vessel.
2012 Reactor Coolant Pump Seal Pinhole Leak
On June 6, 2012, an approximately 0.1 gpm pinhole spray leakage was identified from a weld in a seal of the Reactor Coolant Pump during a routine Reactor Coolant System walkdown inspection. The plant has entered limited operations, and root cause analysis is underway. 
A is the location of Davis Besse. There was never anything wrong with the monitors. They went ballistic. The regulators went into sleep mode and they switched off the equipment. That left people in the dark. Millions were exposed to harmful radiation effects. They were never told. If that isn't cause to change the channel, I don't what is. But the Bible said it comes like a thief in the night. That's exactly what happened here. We were up late and rose again early. We are watchmen on the wall.