"It was an epoch event in the industry in that other plants owners noted it and took steps to address [the issue]. Yet, a decade later, Exelon's Dresden plant experiences an eerily similar repetition of the control-room operator problems."
The lost material was almost certainly shipped to a licensed, low-level waste disposal site, Lochbaum said.
At the Indian Point nuclear plant near New York City, the NRC found that an earthquake safety device has been leaking for 18 years.
In the event of an earthquake, Lochbaum said, the faulty safety device would not help prevent water from leaking out of the reactor. A lack of water to cool the fuel rods has been the most critical problem at the Fukushima plant in Japan after the recent earthquake and tsunami.
"The NRC has known it's been leaking since 1993," Lochbaum said, "but they've done nothing to fix it."
A spokesman at Entergy, the Louisiana-based company that runs Indian Point, told ABC News Radio this month that the container that is leaking is only filled during refueling, which occurs every two years, and leakage from the structure is captured and pumped out.
"This is something we have been aware of and the NRC is aware of, and there are no safety issues with it," the spokesman said. "There is no leak of fuel."
While declining to address specific violations, Roger Hanna, a spokesman for the NRC, said "we do require plant to comply, and we do follow up for corrections" when violations are discovered.
But NRC records examined by ABC News show that such incidents are not uncommon:
In June 2009, at the Southern Nuclear Operating Co. Inc. of Birmingham, Ala., the emergency diesel generator -- which would be used in the event of a disaster -- was deemed inoperable, after years of apparent neglect.
"Cracks in the glands of the emergency diesel generator couplings had been observed since 1988, but the licensee did not recognize the cracking was an indication of coupling deterioration," according to the NRC report. A request for comment from Southern Nuclear was not returned.
On April 19, 2010, the NRC cited the Tennessee Valley Authority Browns Ferry nuclear plant near Decatur for failing to provide "fire protection features capable of limiting fire damage."
The NRC fire protection regulations in effect today were developed as a direct result of a Browns Ferry fire on March 22, 1975.
More recently, according to a Dec. 15 report in the Decatur Daily, the NRC determined that plant management had resolved the fire-safety issues after a two-week inspection in October.
A TVA spokesman told the newspaper that the plant is safer now than when it attracted NRC scrutiny in 2009.
NRC safety records show that inadequate emergency planning was a recurring problem in the industry from 2007 to 2011. Violations included unapproved emergency plans and plan changes, inadequate fire planning and precautions, falsified "fire watch" certification sheets," inadequate flooding precautions, an insufficient tone alert radio system to notify the populace in a potential emergency and faulty assessment of containment barrier thresholds.
Corroded water pipes and cooling problems were also recurring issues.
Pietrangelo of the Nuclear Energy Institute said the industry responds when the NRC finds a safety violation.
"When we find a violation, what each licensee does is put it in their corrective action program ... the experience is shared, with not only the personnel at that site, but, also, if it's significant enough it is shared with the rest of the industry," he said.
" That's how we got better as an industry." And, he added, "The NRC can shut a plant down if it does not think that it's operating safely."