A coalition of 12 environmental groups put U.S. nuclear energy regulators on the hot seat this week by declaring that the leading design for new reactors is unsafe and appealing to officials to investigate.
“We call upon Energy Secretary Chu and Nuclear Regulatory Commission (NRC) Chairman Jaczko to recall the dangerously flawed AP1000 design before accidents occur and more tax dollars are wasted,” the AP1000 Oversight Group said.
The AP1000, designed by Westinghouse Electric Co., is considered central to the success of a domestic nuclear revival. Currently, 14 such plants are under regulatory review at seven sites across the American Southeast.
The coalition’s claims are based on a new report that disclosed a dangerous flaw in the AP1000’s “containment,” a leak-tight structure surrounding the reactor. It is supposed to stop radiation from seeping out in the event of an accident.
“They are the last line of defense,” said report author Arthur Gunderson, the chief engineer at consultancy Fairewinds Associates and a former executive at Nuclear Energy Services PCC.
Gunderson said the probability of radiation leaking out after an accident is higher in the AP1000 than in the current U.S. nuclear fleet.
The report, commissioned by the green groups, details a history of 77 instances of corrosion in containment systems since 1970, including eight discoveries of dangerously large holes and cracks.
In the existing generation of reactors, there is a redundant safety system, which can prevent major public health hazards. Containment buildings today boast a steel barrier backed up by a secondary concrete structure that can soak up leaking radiation.
The current AP100 design has no such safety reinforcement, Gunderson said.
“The steel containment in the AP1000 design has no backup secondary concrete containment behind it to capture post-accident radiation releases,” he said. “The consequences are huge.”
Surrounding the carbon steel containment wall, instead, is a suspect shield building, Gunderson said. Not only is there nothing to capture the radiation, but the “shield building has a hole in its roof that allows radiation to escape,” he said. “It’s designed to whip that material directly out the roof.”
Another alarming feature is the gap that exists between the shield building and the steel containment, the report said.
“Moisture and corrosive agents can flourish in this gap,” said Gunderson.
Eventually, rust could eat through the zinc coating applied on the containment shell and produce cracks. If an accident occurs with even a three-quarter inch hole, “the radiation dose to the population could be 10 times greater than the NRC allows,” Gunderson said.
According to Gunderson, a solution exists. Westinghouse can install filter vents in the top of the shield building to capture gases.
“This step must be taken to protect public health and safety,” he said.
Westinghouse is on its 18th design revision in two years due to previous complaints about the shield building structure, and the NRC has yet to give the design its final stamp of approval.
Still, the government is trying to move the reactor to market. In February, the Department of Energy announced an $8.33 billion loan guarantee to build an AP1000 at Southern Company’s Vogtle plant in Waynesboro, Ga.
Gunderson has submitted his 32-page report to the agency to help put the kibosh on efforts to build the plant and others under review. The AP1000 Oversight Group, meanwhile, is petitioning the Advisory Committee on Reactor Safeguards (ACRS), an independent arm of the NRC, to launch a special investigation into the defect.
“Answers are needed before the NRC can go forward with the AP1000 reactors in the Southeast,” Gunderson said.
There is still no deadline for when the NRC will approve the Westinghouse design. The company declares the AP1000 to be “the safest and most economical nuclear power plant available in the worldwide commercial marketplace.”
“Westinghouse disputes every conclusion put forth at the [AP1000 Oversight Group] press conference, although we are not surprised that an anti-nuclear group with an anti-nuclear bias would make such statements,” Vaughn Gilbert, a spokesperson for Westinghouse, told SolveClimate by email.
“The entire design of the AP1000 has been peer reviewed by well respected universities, regulators, independent experts, our customers and others,” Vaughn added. “Was the report issued by the anti nuclear group earlier peer reviewed at all?”
Vaughn said the containment vessel is built to American Society of Mechanical Engineers proven pressure vessel codes.
“The steel in question is 1.75 inches thick, manufactured and coated to preclude corrosion. In the highly unlikely event of corrosion, it would be readily identified and corrected during regular inspections well before it could in any way become an issue,” Vaughn added.
This week’s protest underlines the uphill battle that nuclear power advocates face in bringing about the trumpeted nuclear renaissance — and not just in the United States.
In February, the UK’s nuclear watchdog voiced concerns with Westinghouse that the AP1000 may not be able to withstand severe weather or a direct airplane hit.
Meanwhile, China as adopted the AP1000 as its reactor-of-choice for its coming nuclear boom. Four are already under construction there, with up to 100 more being planned to come online in the next two decades.
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