Ooops: "FirstEnergy Falls After Report of Nuclear Reactor Cracks" [View All]

FirstEnergy Falls After Report of Nuclear Reactor Cracks

October 13, 2011, 7:42 PM EDT

By Julie Johnsson and Mark Chediak

Oct. 13 (Bloomberg) -- FirstEnergy Corp. fell after a report that engineers discovered cracks in the concrete shell of its Davis-Besse nuclear plant.

FirstEnergy fell 2.8 percent to $43.76 at the close in New York. The Akron, Ohio-based power company had earlier dropped 5 percent, its biggest intraday decline since Aug. 8, according to data compiled by Bloomberg.

Contractors on Oct. 10 discovered a hairline crack measuring about 30 feet (9.1 meters) long as they sliced a hole into the plant’s outer shell in order to install a new reactor vessel head, said Jennifer Young, a FirstEnergy spokeswoman.

The damaged structure poses no safety hazard to Davis- Besse, located 21 miles (34 kilometers) southeast of Toledo, Young said. The cracked shell is the outermost of several layers of steel and concrete that protect the reactor, which has been shut down since Oct. 1 in preparation for the repair work....

Cracks found in critical reactor parts at Davis-Besse power plant

March 15, 2010, 11:21 AM


AK HARBOR, Ohio -- Inspectors at the Davis-Besse power plant have found cracking in critical parts that is similar to what caused massive corrosion at the plant eight years ago.

The FirstEnergy Corp. plant near Toledo has been down since Feb. 28 for regular refueling, maintenance and safety inspections, including ultrasonic inspections of 69 control rod "nozzles" in the reactor lid.

The problem parts are known as "nozzles" because of their shape. They are corrosion-resistant alloy steel tubes that penetrate the reactor's heavy carbon steel lid. They allow reactor operators to adjust the nuclear fission by moving control rods into and out of the reactor core.

The cracked parts pose no threat to the public.

"There are indications of cracking in 13 of 54 nozzles checked so far...

-The Three Mile Island nuclear plant experienced a loss of coolant accident in March 1979. Emergency pumps automatically started to replace the water flowing out the leak. Operators turned off the pumps because instruments falsely indicated too much water in the reactor vessel. Within two hours, the reactor core overheated and melted, triggering the evacuation of nearly 150,000 people.

-At the Callaway nuclear plant in 2001, workers encountered problems while testing one of the emergency pumps. Investigation revealed that a foam-like bladder inside the RWST was flaking apart. Water carried chunks of debris to the pump where it blocked flow. The debris would have disabled all the emergency pumps during an accident.

-At the Haddam Neck nuclear plant in 1996, the NRC discovered the piping carrying water from the RWST to the reactor vessel was too small. It was long enough but it was not wide enough to carry enough water during an accident to re-fill the reactor vessel in time to prevent meltdown. The plant operated for nearly 30 years with this undetected vulnerability.

-At several US and foreign nuclear power plants, including the Limerick nuclear plant 8 years ago, the force of water/steam entering the containment building during a loss of coolant accident has blown insulation off piping and equipment. The water carried that insulation and other debris into the containment sump. The debris clogged the piping going to the emergency pumps much like hair clogs a bathtub drain. According to a recent government report, 46 percent of US nuclear plants are very likely to experience blockage in the containment sumps in event of a hole the size found at Davis-Besse opens up. For slightly larger holes, the chances of failure increase to 82 percent.<1>


From Union of Concerned Scientists -- Aging Nuclear Plants -- Davis-Besse: The Reactor with a Hole in its Head

Davis Besse: Incident history
...Erosion of the 6-inch-thick (150 mm) carbon steel reactor head, caused by a persistent leak of borated water.
Reactor head hole

In March 2002, plant staff discovered that the boric acid 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<10> of the carbon steel reactor pressure vessel head over an area roughly the size of a football (see photo). This significant reactor head wastage left only 3/8 inch of stainless steel cladding holding back the high-pressure (~2500 psi) reactor coolant. A breach would have resulted in a loss-of-coolant accident, in which superheated, superpressurized reactor coolant could 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 may 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: (1) the containment sump that allows the reactor coolant to be reclaimed and reinjected into the reactor; (2) the high pressure injection pumps that would reinject such reclaimed reactor coolant; (3) the emergency diesel generator system; (4) the containment air coolers that would remove heat from the containment building; (5) reactor coolant isolation valves; and (6) the plant's electrical distribution system.<11> Under certain scenarios, a reactor rupture would have resulted in core meltdown and/or breach of containment and release of radioactive material. 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.<12> The U.S. Justice Department investigated and penalized the owner of the plant over safety and reporting violations related to the incident. The NRC determined that this incident was the fifth most dangerous nuclear incident in the United States since 1979.<3>