WASHINGTON -- For 10 years the Nuclear Regulatory Commission ignored a deterioration problem that affects the reactor vessels of two-thirds of the nation's nuclear power plants. While France and Japan moved swiftly to correct the problem in their plants after it first surfaced in 1991, the NRC has rejected efforts to replace the equipment in US plants, even though the problem emerged this spring at a nuclear plant in South Carolina.

"The federal agency entrusted to ensure that our nuclear reactors run safely should not turn a blind eye to a serious safety problem," said David Lochbaum, Nuclear Safety Engineer at the Union of Concerned Scientists.  "We're lucky an accident hasn't occurred."

The deterioration problem, which is found in the nation's pressurized water reactors, is in the joints between the reactor vessel and the tubes that house control rods. These joints, or nozzles, are subject to severe stress from heating and are susceptible to cracking -- as was found in a French plant in 1991. If these cracks were to grow large enough they could lead to an ejection of the control rod, leakage of reactor cooling water, and failure of emergency systems, which could lead to a reactor meltdown.

"Instead of a band-aid fix, the NRC needs to follow the lead other countries have taken in protecting public safety by replacing the cracked reactor vessel heads." said Lochbaum. "Anything short of replacing this broken equipment needlessly endangers the public."

Cracks discovered this spring at Oconee Unit 3 in South Carolina extended nearly 45 percent of the way around two nozzles. With a crack this large the massive pressure in the reactor could result in a catastrophic rupture. In 1994 the NRC wrote a report on this type of cracking, based on an inspection of a single US nuclear plant, and claimed that cracks as large as the one at Oconee were not likely. In contrast, similar plants in Europe and Japan underwent aggressive safety precautions when the problem was discovered.

"Waiting a decade until an expected problem crops-up is bad enough," Lochbaum said. "Waiting until an accident occurs is worse."