Federal nuclear power regulators have allowed the nation’s aging reactors to stay in operation without major overhauls by repeatedly weakening or failing to enforce safety standards, a yearlong investigation by the Associated Press has found.
The AP said that numerous decisions by the Nuclear Regulatory Commission to ease safety rules, after concluding that original requirements were too strict, have raised concerns among some experts that the risk of a serious accident has grown.
Examples abound of the NRC accommodating the nuclear industry, which accounts for 19 percent of the nation’s electricity, by loosening safety requirements. For instance, valves designed to bottle up radioactive steam in the event of earthquakes or other accidents have been allowed to leak far more vapor than previously permitted — and plants have violated even the more lenient standards.
Likewise, when steam generator tubes cracked and leaked, a more lenient test was devised so the tubes could meet standards.
The investigation — which included a review of 226 preliminary notifications about emerging safety problems issued by the NRC since 2005 — also turned up failed cables, broken seals, damaged nozzles, clogged screens, cracked concrete, dented containers, corroded metals, rusty underground pipes and thousands of other problems linked to aging.
Despite the problems linked to aging reactors, the AP said, no government or industry body has studied the potential safety impact of the deterioration in recent years, even as dozens of reactors have had their licenses renewed by the NRC.
“We’ve seen the pattern,” said nuclear safety scientist Dana Powers, who works for Sandia National Laboratories and sits on an NRC advisory panel. “They’re … trying to get more and more out of these plants.”
On the other hand, many authorities say the nation’s nuclear plants are safe even under the revised standards. The AP said a recurring pattern is that, as nuclear operations fall out of compliance with safety requirements, studies are conducted by industry and government that find the original rules to be “unnecessarily conservative,” justifying looser regulations.
For example, in 2010 the NRC weakened, for a second time, its safety margin for acceptable radiation damage to reactor vessels. The standard is based on a vessel’s “reference temperature,” which predicts when it will become vulnerable to failure. Over the years, many plants have violated or come close to violating the standard, and the NRC responded by raising the reference temperature by 78 percent.
Although the current disaster at Japan’s Fukushima Daiichi nuclear plant prompted an NRC study that is due out next month, the nation’s potential nuclear safety problem has been years in the making.
When U.S. commercial nuclear reactors were being built in the 1960s and 1970s, they were licensed for 40 years with the expectation they would be replaced. But high costs, and concerns raised by the Three Mile Island accident in 1979 derailed those plans.
Instead, licenses for 66 of the nation’s 104 nuclear power plants have been extended by 20 years, and renewal applications are under review for 16 others. As of today, 82 of the nation’s reactors are more than 25 years old.
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