Time after time, officials at the Nuclear Regulatory Commission have decided original regulations were too strict, arguing that safety margins could be eased without peril, according to records and interviews.
The result? Rising fears that these accommodations are significantly undermining safety.
Examples abound. When valves leaked, more leakage was allowed -- up to 20 times the original limit. When rampant cracking caused radioactive leaks from steam generator tubing, an easier test of the tubes was devised so plants could meet standards.
Failed cables. Busted seals. Broken nozzles, clogged screens, cracked concrete, dented containers, corroded metals and rusty underground pipes -- all of these and thousands of other problems linked to aging were uncovered in the AP's yearlong investigation.
Yet despite the many problems linked to aging, not one official body in government or industry has studied the overall frequency and potential impact on safety of such breakdowns in recent years, even as the NRC has extended the licenses of dozens of reactors.
Industry and government officials defend their actions and insist no chances are being taken. But the AP investigation found that with billions of dollars and 19 percent of America's electricity supply at stake, a cozy relationship prevails between the industry and its regulator, the NRC.
Records show a recurring pattern: Reactor parts or systems fall out of compliance with the rules. Studies are conducted by the industry and government, and all agree that existing standards are "unnecessarily conservative." Regulations are loosened, and the reactors are back in compliance.
"That's what they say for everything, whether that's the case or not," said Demetrios Basdekas, an engineer retired from the NRC. "Every time you turn around, they say 'We have all this built-in conservatism.' "
The AP found proof that aging reactors have been allowed to run less safely to prolong operations. As equipment has approached or violated safety limits, regulators and reactor operators have loosened or bent the rules.
Last year, the NRC weakened the safety margin for acceptable radiation damage to reactor vessels -- for a second time. The standard is based on a measurement known as a reactor vessel's "reference temperature," which predicts when it will become dangerously brittle and vulnerable to failure. Over the years, many plants have violated or come close to violating the standard.
As a result, the minimum standard was relaxed -- first by raising the reference temperature 50 percent, then 78 percent above the original, even though a broken vessel could spill its radioactive contents into the environment.
"We've seen the pattern," said nuclear safety scientist Dana Powers, who works for Sandia National Laboratories and sits on an NRC advisory committee. "They're ... trying to get more and more out of these plants."
'Sharpening the pencil'
Unprompted, several nuclear engineers and former regulators used nearly identical terminology to describe how industry and government research has frequently justified loosening safety standards to keep aging reactors within operating rules. They call the approach "sharpening the pencil" or "pencil engineering" -- the fudging of calculations and assumptions to yield answers that enable plants with deteriorating conditions to remain in compliance.
"Many utilities are doing that sort of thing," said engineer Richard T. Lahey Jr., who used to design nuclear safety systems for General Electric Co. "I think we need nuclear power, but we can't compromise on safety. I think the vulnerability is on these older plants."
In public pronouncements, industry and government say aging is well under control.
"I see an effort on the part of this agency to always make sure that we're doing the right things for safety. I'm not sure that I see a pattern of staff simply doing things because there's an interest to reduce requirements -- that's certainly not the case," NRC chairman Gregory Jaczko said at agency headquarters in Rockville, Md.
Agency staff, plant operators, and consultants paint a different picture in little-known reports, where evidence of industrywide problems is striking:
- The AP reviewed 226 preliminary notifications -- alerts on emerging safety problems -- issued by the NRC since 2005. Wear and tear in the form of clogged lines, cracked parts, leaky seals, rust and other deterioration contributed to at least 26 alerts over the past six years. Other notifications lack detail, but aging also was a probable factor in 113 additional alerts. That would constitute up to 62 percent in all. For example, the 39-year-old Palisades reactor in Michigan shut Jan. 22 when an electrical cable failed, a fuse blew and a valve stuck shut, expelling steam with low levels of radioactive tritium into the air outside. And a one-inch crack in a valve weld aborted a restart in February at the LaSalle site west of Chicago.
- One 2008 NRC report blamed 70 percent of potentially serious safety problems on "degraded conditions." Some involve human factors, but many stem from equipment wear, including cracked nozzles, loose paint, electrical problems, or offline cooling components.
- Confronted with worn parts that need maintenance, the industry has repeatedly requested -- and regulators have often allowed -- inspections and repairs to be delayed for months until scheduled refueling outages. Again and again, problems worsened before they were fixed. Postponed inspections inside a steam generator at New York's Indian Point -- the country's oldest operating commercial nuclear power plant -- allowed tubing to burst, leading to a radioactive release in 2000. Two years later, cracking was allowed to grow so bad in nozzles on the reactor vessel at the Davis-Besse plant near Toledo, Ohio, that it came within two months of a possible breach, the NRC acknowledged in a report. A hole in the vessel could release radiation into the environment, yet inspections failed to catch the same problem on the replacement vessel head until more nozzles were found to be cracked last year.
Even mundane deterioration at a reactor can carry harsh consequences.
For example, peeling paint and debris can be swept toward pumps that circulate cooling water in a reactor accident. A properly functioning containment building is needed to create air pressure that helps clear those pumps. The fact is, a containment building could fail in a severe accident. Yet the NRC has allowed operators to make safety calculations that assume containment buildings will hold.
In a 2009 letter, Mario V. Bonaca, then the chairman of the NRC's Advisory Committee on Reactor Safeguards, warned that this approach represents "a decrease in the safety margin" and makes a fuel-melting accident more likely.
Many photos in NRC archives -- some released in response to AP requests under the federal Freedom of Information Act -- show rust accumulated in a thick crust or paint peeling in long sheets on untended equipment at nuclear plants. Other breakdowns can't be observed or predicted, even with sophisticated analytic methods.
Industry and government reports are packed with troubling evidence of unrelenting wear -- and repeated regulatory compromises.
Four areas stand out:
BRITTLE VESSELS: For years, operators have rearranged fuel rods to limit gradual radiation damage to the steel vessels protecting the core and to keep them strong enough to meet safety standards.
It hasn't worked well enough.
Even with last year's weakening of the safety margins, engineers and metal scientists say some plants might be forced to close over these concerns before their licenses run out -- unless, of course, new compromises with regulations are made. But the stakes are high: A vessel damaged by radiation becomes brittle and prone to cracking in certain accidents at pressurized water reactors, potentially releasing its radioactive contents into the environment.
LEAKY VALVES: Operators have repeatedly violated leakage standards for valves designed to bottle up radioactive steam in the event of earthquakes and other accidents at boiling water reactors.
Many plants have found they could not adhere to the general standard allowing each of these parts -- known as main steam isolation valves -- to leak at a rate of no more than 11.5 cubic feet per hour. In 1999, the NRC decided to permit individual plants to seek amendments of as much as 200 cubic feet per hour for all four steam valves combined. But plants keep violating even those higher limits. For example, in 2007, Hatch Unit 2 in Baxley, Ga., reported combined leakage of 574 cubic feet per hour.
CRACKED TUBING: The industry has long known of cracking in steel alloy tubing originally used in the steam generators of pressurized water reactors. Ruptures were rampant in these tubes containing radioactive coolant; in 1993 alone, there were seven. Even today, as many as 18 reactors are still running on old generators.
CORRODED PIPING: Between 2000 and 2009, the annual number of leaks from underground piping shot up fivefold, according to an internal industry document obtained and analyzed by the AP.