The U.S. Nuclear Regulatory Commission approved Westinghouse's AP1000 nuclear reactor design, clearing the way for construction of the first U.S. reactors in three decades.

While the NRC had approved an early version of the reactor in 2006, it was modified to meet NRC's new and additional requirements, including a steel reinforced concrete structure approximately 3 feet thick protecting the steel containment vessel housing the reactor.

The reactor's passive design, which relies on gravity to deliver water, and on evaporation and condensation to re-circulate it until generators or outside power can be used "allows the plant to cope with a Fukushima-type event," Westinghouse, a unit of Toshiba Corp., said in a statement.

NRC Chairman Gregory B. Jaczko said the design had fully addressed safety concerns.

"The design provides enhanced safety margins through use of simplified, inherent, passive or other innovative safety and security functions and also has been assessed to ensure it could withstand damage from an aircraft impact without significant release of radioactive materials," he said in a statement.

But in an opinion filed in November 2010, John Ma, an NRC technical expert, argued that "structural integrity cannot be assured" if the shield building were hit by a tornado, earthquake or any of several other known hazards "because it has not been demonstrated that the building can absorb and dissipate energy," The Wall Street Journal reports.

U.S. Energy Secretary Steven Chu applauded the NRC approval, saying the Obama administration and the Energy Department "are committed to restarting America's nuclear industry."

The approval also clears the way for construction of two reactors planned for the Southern Company's plant near Augusta, Ga., and another two at the Summer plant of South Carolina Electric and Gas in Fairfield County, S.C. The four facilities will add an estimated 4,600 megawatts of generating capacity to the Southeast electrical grid, says the Nuclear Energy Institute.

In a statement issued by Westinghouse, Marilyn Kray, president of NuStart Energy Development, a consortium of utilities and reactor vendors, said, "The AP1000 is the reactor design that will set the foundation for the next generation of nuclear plants in the U.S."

China is in advanced stages of constructing four units of the earlier AP1000 version, reports The New York Times, with the first unit slated to go online in 2013.

The NRC's go-ahead, considered the "gold standard" of regulatory approvals, will also help Westinghouse sell more reactors overseas, Westinghouse President and Chief Executive Officer Aris Candris told Platts.