"We could have had the worst nuclear catastrophe this nation had ever experienced," said Amy Ryder, who leads the campaign to permanently close the plant for environmental advocacy group Ohio Citizen Action.
Recently, workers found coolant leaks at the Sequoyah 2 plant in Tennessee and the Comanche Peak 1 plant in Texas. Both plants had leaked boric acid, which is an additive in reactor coolant that is highly corrosive to carbon steel.
"There's been a lengthy list of these near-misses," said David Lochbaum, a nuclear safety engineer at the Union of Concerned Scientists. "It's a growing problem. For an aging fleet of nuclear reactors, it's not unexpected."
While there hasn't been a major nuclear accident in the United States in 20 years, the consequences of such an event could be devastating. If safety systems fail, aging reactors could leak radiation, which may contaminate the water supply and cause life-threatening diseases and infections.
The 1986 meltdown of Ukraine's Chernobyl nuclear reactor spewed radiation across Europe. Since the accident, thousands of people in Ukraine, Belarus and Russia have died from radiation-related illnesses. Almost 2,000 cases of thyroid cancer have resulted from the reactor explosion, according to BBC News.
"If there's an accident, the damage is irreversible," said Ryder of Ohio Citizen Action. "I don't think the technology is worth the risk."
Critics say the U.S. Nuclear Regulatory Commission, which regulates safety at commercial nuclear power plants, should have caught the Davis-Besse problem sooner.
In fall 2001, the NRC identified 12 nuclear power plants as being highly susceptible to corrosion or cracking. The commission shut down all of these plants for inspection, except Davis-Besse.
Davis-Besse started leaking boric acid in 1996. Between 1998 and 2000, the leakage began causing problems for other equipment. In 1999, FirstEnergy, the corporation that operates Davis-Besse, found traces of rust particles in the filters of radiation monitors. These filters, which sample the air inside the reactor's containment structure, are normally replaced every two to three months. When the leakage began, the filters had to be replaced every day.
"That should have been a sign that something was not right here," Lochbaum said.
FirstEnergy ignored photographic evidence documenting rust seeping from the reactor head as early as April 2000, Ryder said.
In August, FirstEnergy admitted to NRC investigators that it placed production before public safety by deferring inspections and corrective action programs. FirstEnergy is spending more than $400 million on repairs.
By allowing safety margins to erode, FirstEnergy and the NRC have lost a great deal of the public's trust, Lochbaum said.
"Those are huge holes cut in the safety net," he said.
Rep. Dennis Kucinich (D-Ohio) recently filed a 29-page petition asking the NRC to revoke FirstEnergy's operating license. Kucinich says that the utility violated NRC rules by ignoring NRC warnings, ignoring its own monitoring systems and hiding information from the regulatory agency.
Ohio Citizen Action wants to see the reactor shut down for good, Ryder said. The group is recommending that FirstEnergy convert the plant to a different source of fuel, such as gas or coal, to produce electricity.
"Given that this technology is an unforgiving technology, we can't take chances," Ryder said. "Once these things show this type of aging, it's time for the utilities to retire them. If a reactor leaks, it's time to shut it down."
But others say old equipment shouldn't be blamed for causing the problems at Davis-Besse.
One industry insider says the problem at the Ohio plant stemmed from a human failure rather than a mechanical one. Alex Marion, director of engineering for Nuclear Energy Institute, a nuclear industry trade and lobbying group, said if Davis-Besse operators had effectively implemented its aging-management program, they might have caught the boric acid leak sooner.
"I don't think it's a problem that relates to aging management," Marion said. "It's a problem with human performance."
Davis-Besse is just one of the nuclear power plants built in the 1960s and '70s that are showing signs of wear and tear. Equipment intended to last as long as some plants' 40-year licenses is breaking in areas not anticipated when the plants were built.
Thirty years ago, utilities were quick to fix any problems related to aging, Lochbaum said. But electricity deregulation has forced some nuclear plant owners to cut costs by eliminating safety tests, trimming staff and deferring equipment repairs.
In the last 15 years, about 22 nuclear reactors have ceased operating, Lochbaum said. Several of these plants were closed because owners didn't want to pay to repair or replace aging equipment.
The Trojan Nuclear Plant closed its doors in 1993, when Portland General Electric decided not to replace an aging steam generator, which would have cost more than $100 million to repair.
But some say the problem of aging equipment may be overstated.
"With the notoriety of Davis-Besse, the situation has heightened sensitivity to any leakage that may be found," Marion said. NRC safety rules allow for some types of leaks, he said.
There are two types of "leakage" that a plant may experience: leakage within the plant and releases of radioactivity from the plant.
"Within the plant, there is a recognition that pumps and valves and other components may leak, and the NRC has imposed limits on what that leakage may be," said NRC spokeswoman Jan Strasma.
NRC has limits for both unidentified leakage (where the source is unknown) and identified leakage (where the source is known). For unidentified leakage, the limit is typically about 1 gallon per minute. If the limit is exceeded, the plant would have to shut down to find the leakage, Strasma said.
Nuclear plants routinely release gaseous and liquid radioactivity under controlled and monitored conditions, Strasma said. These releases must meet NRC limits based on potential radiation exposure to the public. The limits are designed to keep radiation exposures to the "most affected" members of the public smaller than 3 millirem for liquid releases and less than 10 millirem for gaseous releases (a millirem is a unit of absorbed radiation dose). In practice, the releases are substantially below these limits, Strasma added.
"The current plants are safe and comply with NRC regulations," Marion said. "I believe the inspection programs are adequate and sufficient."
Plant owners are always modernizing equipment with new technology, Marion added, such as digital control systems, which are more reliable and more compact than conventional systems.
But since the NRC's budget has been slashed virtually every year in the past decade, it employs fewer inspectors. Without an increase in funding to hire more inspectors, aging nuclear plants could compromise public safety, Lochbaum said.
"The NRC shouldn't have to pick between safety and business," he said.
The NRC recently announced that it would reform its regulation procedures in response to a report that found that the commission should have acted sooner at Davis-Besse. Changes will include more thorough inspections and a stricter means of making sure plant owners fix problems faster.
Three electric utilities are expected to seek NRC approval later this year to construct the nation's first new nuclear plants since the 1979 accident at Three Mile Island.
Newer facilities use "passive" design, which relies on natural forces like convection and gravity flow to distribute emergency cooling water. This reduces reliance on pumps, valves, emergency diesel generators and other components that the cooling systems in today's plants rely on.
Although the new plants may be more efficient and cheaper to bring online than conventional plants, there's no way to know if they will experience any of the same unexpected problems that Davis-Besse faces today.
"If nothing else, the industry is optimistic," Lochbaum said. But unless the industry puts in proper safeguards at new plants, he warns, "it could happen again."