The two reactors at the South Texas nuclear power plant, an hour southwest of Houston, last year churned out 21.37 billion kilowatt-hours. By 2015, its majority owner, New Jersey-based NRG Energy, hopes to at least double that capacity if it gets permission to build two more reactors on the site. The company filed the first application on Monday for a new nuclear power plant—two advanced boiling-water reactors—in more than 30 years.

"It is a new day for energy in America," David Crane, NRG president and chief executive officer, said after making the application. "Advanced nuclear technology is the only currently viable large-scale alternative to traditional coal-fueled generation to produce none of the traditional air emissions," including the greenhouse gases responsible for climate change.

Armed with the backing of the White House and congressional leaders—and subsidies, such as $500 million in risk insurance from the U.S. Department of Energy— the nuclear industry is experiencing a revival in the U.S. As many as 29 new reactors may be added to the current U.S. fleet of 104, according to Bill Borchardt, director of the Nuclear Regulatory Commission's (NRC) office of new reactors. "It is going to be significantly different than it was in the 1970s," he says.

The South Texas project is the first entirely new reactor out of the gate, though it simply fulfills the original planning for four reactors at the site. The NRC says such upgrades of existing facilities are likely to comprise the majority of new nuclear power plants, all but one—a plant near Syracuse in central New York State— are in the Southeast or Texas. "At the majority of these sites, there's strong support for nuclear power," says Loren Plisco, NRC's deputy regional administrator for construction in the southeastern region.

The inactive reactor at Browns Ferry in northern Alabama was restarted in May after being shuttered for 22 years due to maintenance issues its owner, the Tennessee Valley Authority, decided would be too costly to fix. Completion of construction of a second reactor at TVA's Watts Bar power plant near Chattanooga in Tennessee has begun as well. The TVA expects to finish construction in 2013 at a cost of $2.49 billion. Its older twin at Watts Bar required 23 years to build at a total cost of nearly $7 billion, according to the TVA.

Such long delays and ballooning costs—paired with improvements in U.S. energy efficiency and reactor accidents at Three Mile Island in 1979 and Chernobyl in 1986—helped kill the first wave of nuclear power plant construction in the U.S. And the rebirth is not without controversy: Some environmentalists oppose the new construction, noting that all of the potential risks linked to nuclear power remain. "The flaws of nuclear power—excessive cost, security threats and long-lived radioactive waste—have not been solved," says Tyson Slocum, director of Public Citizen's energy program. "More nuclear reactors will only exacerbate these problems."

In fact, the only shift in the debate is the growing acceptance of nuclear power as an alternative energy source to coal-fired generation, which spews globe-warming greenhouse gas emissions. "If we're not serious about building more nuclear energy [power plants] around the world, then we are not serious about addressing climate change," James Rogers, chief executive of North Carolina based–Duke Energy, said during remarks at the recent U.N. climate summit.

Critics, such as Amory Lovins of the Rocky Mountain Institute, an energy think tank, counter that nuclear power is an overly complicated and dangerous solution to a relatively simple problem that cannot compete with safer, lower-emitting energy generation sources, such as wind, solar, geothermal, biomass, small hydropower and cogeneration, without government subsidies.

But proponents insist that if the U.S. and other countries continue to rely on large power plants and the demand for energy continues to grow as anticipated, then coal burning and uranium fissioning are the most effective options for boiling large amounts of water to produce steam to turn turbines—and thereby produce the most electricity.

The Intergovernmental Panel on Climate Change, an international body of scientists, economists and other experts, noted in a climate change report released earlier this year that "Nuclear energy … could make an increasing contribution to carbon-free electricity and heat in the future." But these experts only expect nuclear power to account for 18 percent of worldwide power generation in 2030 under emission-reduction scenarios, up from 16 percent today.

To reach even that slightly greater portion of world energy supply, however, will require the construction of at least 50 new nuclear power plants, not including replacements of existing reactors, in the next 23 years. NRG's application calls for the construction of two new reactors based on technology developed by General Electric and already operating in Japan and under construction in Taiwan. "We wanted a technology built by someone on time and on budget," Crane says. "There was only one design that satisfied that criteria and that was [the advanced boiling-water reactor.]"

The ABWR works by using the heat generated by the controlled splitting of uranium atoms in fuel rods to directly boil water into steam that then turns turbines to produce electricity. Improvements over previous designs include removing water circulation pipes that could rupture and accidentally drain water from the reactor, exposing the fuel rods to a potential meltdown, as well as fewer pumps to move the water through the system. "ABWR has digital primary controls [for the nuclear reactor] and analog backup. We think that's safer," notes Steve Winn, NRG's executive vice president for strategy, environment and nuclear development. "Planes are mostly digital by now but they also have fly-by-wire capability."

The new reactors will also have some modifications specific to the South Texas site, including floodproofing to protect the reactor from the adjacent 7,000-acre reservoir that provides its cooling water and updates to the pumps and fuel rods employed based on the Japanese experience of operating such reactors.

The company projects it will spend $6 billion constructing the two new reactors and hopes to have the first unit online by 2014, assuming the NRC completes its review by 2010. The NRC will first check to ensure the completeness of the voluminous application over the next two months, spokesman Scott Burnell says. "The staff's estimate is that the full technical review would take two and a half years," he adds.

The project, however, must overcome other hurdles, including a lack of technical and labor expertise as well as manufacturing capacity in the U.S., along with potential public opposition. "The stakes are high," Crane says, noting that the company has already spent $40 million on preparing the application and the price tag will be above $100 million when it orders the reactor vessel next year. "All it takes is one significant thing to go wrong and your project goes away." Nevertheless, the first step on the road to a nuclear revival in the U.S. has been taken.