"The proposed AP1000 containment design is inherently less safe than current reactors," said Arnold Gundersen, a nuclear scientist who authored a 32-page report on behalf of 12 organizations that compose the "AP1000 Oversight Group."
The coalition represented by the oversight group comprises Friends of the Earth, South Carolina's Sierra Club, Nuclear Watch South, the Southern Alliance for Clean Energy, Georgia Women's Action for New Directions, and other groups.
In a conference call with reporters, Gunderson contended the new reactors will be vulnerable to leaks caused by corrosion holes. Such issues have been identified at least 80 times during the past 45 years in conventional reactors, which have a redundant containment system that is not included in the new design.
"If you would imagine a nuclear reactor as a pressure cooker, then its containment would be the leak-tight building surrounding that pressure cooker," he said. "Containment systems are critically important because they are the last line of defense in an accident."
While the containment systems on current reactors are constructed of steel and concrete, and together form multiple barriers to radiation releases, the AP1000 design has no such sealed concrete backup barrier, he said.
"The AP1000 shield building does not collect radiation and trap it as in existing designs. Rather, the AP1000 shield building has a hole in its roof allowing radiation to escape," Gunderson said.
"The AP1000 design uses a chimney effect to draw up contaminated air that leaks out of the steel containment and releases it directly into the environment through the hole in the roof," Gunderson said.
The groups asked that the U.S. Nuclear Regulatory Commission investigate the findings and also suspend licensing activities for plants that would use the new design.
NRC spokesman Scott Burnell said the commission is always open to input throughout the licensing process for nuclear reactors.
"Any individual or group can always submit comments as part of the design and certification process," Burnell said. "It will go into the overall design and certification hopper and once we get to the point where we propose a rule that would certify the design, those comments would be taken into consideration."
The AP1000 reactors, he added, will be subject to frequent and strict inspections that should identify any corrosion issues that could cause problems, Burnell said. "It is, literally, part of the American Society for Mechanical Engineers' codes and standards that govern pressure vessels. The operating procedures would account for those standards."
Burnell also said design differences between existing reactors and the AP1000 design will make it easier to inspect corrosion-prone areas.
"On the AP1000, the gap between the containment structure and the shield building is wide enough to allow regular inspection," he said.
Southern Nuclear, which operates Plant Vogtle for its owners, has confidence in the reactor's design and in the NRC's licensing process, company spokeswoman Beth Thomas said.
"NRC is continuing its standard review process for the Westinghouse AP1000 design," she said. "A great benefit of the NRC's new licensing process is that reviews are completed prior to major construction -- as opposed to the previous licensing process used during construction of current operating plants in the U.S."