The NRC identified the leak in fall 2001 but let the plant keep operating. An NRC Inspector General's report in 2002 found the agency's willingness to keep the plant running "was driven in large part by a desire to lessen the financial impact on (plant operator FirstEnergy) that would result from an early shutdown."
In a statement last month, the NRC blamed FirstEnergy fe for providing "inaccurate and misleading information," including its "explanation of the leak."
FirstEnergy says it has made extensive staffing and procedural changes to prevent such situations in the future.
Stuart Richards, deputy director of the NRC's inspection unit, says such shutdowns show "that if the NRC feels plants shouldn't be operating, we'll take appropriate actions."
Richards notes that Davis-Besse was the last plant to be shuttered for at least a year and that similar safety problems have decreased. Plants were shut down an average of 1.5% of the time because of safety lapses in 2006, down from 10% in 1997, NRC figures show.
NRC credits a more precise oversight system, launched in 2000, that increases inspections at poorly performing plants. However, one key safety measure — of problems that the NRC says increase the annual risk of a meltdown from an average of 1 in 17,000 to up to 1 in 1,000 — has doubled the past six years to an average of 18 a year.
There have been 337 such "precursors" since 1988, including failures of pumps that supply water to reactors in a crisis, the NRC says. Each plant's emergency cooling system typically has several backups, such as pumps or power generators.
NRC spokesman Scott Burnell says the increase in such problems is insignificant because 22 of the incidents stemmed from two causes the agency was aware of, rather than a rash of separate problems.
Half the problems stemmed from the loss of power — needed to run critical cooling systems — and most of those occurred during the massive electricity blackout that struck the northeastern USA on Aug. 14, 2003. The other half involved cracks in nozzles that, in some cases, let water seep from a reactor.
Lochbaum says that such explanations by the NRC do not ease his concerns about plants' safety. He blames the increasing "precursors" on scaled-back inspections by the NRC and plant owners.
From 1993 to 2000, routine NRC inspection hours declined by 20%, partly because of budget constraints, the NRC acknowledges.
Although the hours spent inspecting plants rose 11% from 2001 to 2005, most of the increase stemmed from more attention to post-9/11 security checks, rather than the operation of the plants.
NRC and industry officials acknowledge they're inspecting many parts of nuclear plants less frequently since 2000. But they say inspections are more effective because they now focus on critical gear whose failure poses the greatest risk to the public.
Questions about standards
In its report, the UCS says the NRC has not consistently enforced many of its safety regulations for nuclear plants.
The group says that since 1981, for example, the NRC has issued about 1,000 exemptions to plants that failed to meet fire-protection rules that went into effect after a 1975 blaze at the Browns Ferry plant in Alabama.
The NRC says the waivers were granted to older plants that couldn't make certain structural changes such as separating primary and backup safety gear. Waivers permit alternative fire-prevention methods, such as sprinklers or smoke alarms.