The last few years have seen a growing number of liberal and environmental heavyweights publicly call for more nuclear energy to deal with climate change. Today, the pro-nuclear ranks include Bill Gates, Al Franken, Richard Branson, and Barack Obama. Also on the list are superstar economist Jeffrey Sachs, the novelist Ian McEwan, Google chairman Eric Schmidt, and Microsoft cofounder Paul Allen. There are former environmental leaders, including former Greenpeace Executive Director Stephen Tindale, and former Friends of the Earth trustee Hugh Montefiore. And there are prominent scientists including Gaia hypothesis ecologist James Lovelock, former NASA climate scientist James Hansen, much-cited climate scientist Tom Wigley, and MIT climate scientist Kerry Emanuel.

Many of these individuals recognize that one of nuclear's chief challenges is to become much cheaper, so that new nuclear plants can replace fossil fuels. In service of this goal, Breakthrough Institute has analyzed the factors that drive the cost of new nuclear plants, and has proposed a way to deal with them. The key is innovation. In particular, developing, demonstrating and deploying advanced, or what are called Generation IV, nuclear technologies. Already Breakthrough's new report, How to Make Nuclear Cheap, has received positive notices from Time, SmartPlanet, and IEEE Spectrum (a leading high-tech science magazine), and was received positively by both Republicans and Democrats at a standing-room only briefing on Capital Hill last week.

Safety is critical to the economics of nuclear, but it is not the only factor. Advanced reactors that are able to operate at ambient pressures, and with fuels that are much more resistant to melting, require fewer redundant safety systems and less substantial containment. Molten metal and salt coolants promise not only greater safety, but also allow reactors to operate at higher temperatures, making them more efficient. Smaller reactors, produced modularly, or in many cases manufactured entirely off-site, promise to eliminate the rising costs and delays that have plagued large, customized reactor builds. Reactor designs that can deliver these benefits while utilizing as much of the present light-water supply chain can be commercialized fastest and most cheaply.

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Advanced nuclear designs are not new. Many alternative designs were demonstrated by the US Department of Energy in the sixties, seventies, and eighties. Unfortunately, the antinuclear movement succeeded in halting most advanced nuclear research and demonstration projects in the early 1990s. The new documentary film, Pandora's Promise, documents the most notorious of these episodes, when Democrats in the US Senate, working with environmentalists and the Clinton White House, halted the development of the integral fast reactor, which used liquid sodium, a metal, as a coolant.

The question is not whether the world will pursue advanced nuclear reactors but rather whether the United States will. The United States developed virtually every advanced reactor design under consideration today, and we still lead the world in the technical expertise to build them. But while China, India, and South Korea are all building advanced reactors, the United States has no plan to build even a demonstration-scale plant.

That may change. A majority of Americans (57 percent) told Gallup last year they support nuclear energy — a number that rose from 46 percent in 2001 and was unchanged by Fukushima. Where liberal baby boomers grew up fearing nuclear war and power, liberal millennials born well after Three Mile Island grew up fearing climate change. The MIT and UC Berkeley nuclear engineering programs have been revitalized in recent years by climate concerned directors, Richard Lester and Per Peterson respectively, and have attracted millennial graduate students to their programs. MIT has already spun off advanced nuclear start-ups, including Transatomic, profiled last month in the New Yorker, which designed a reactor made to burn waste as fuel. UC Berkeley is working with China to demonstrate an advanced design. Meanwhile, in Washington, Sen. Ron Wyden (D-OR), Sen. Diane Feinstein (D-CA), Sen. Lisa Murkowski (R-AK), and Lamar Alexander (R-TN) introduced legislation that promises to finally resolve the dispute over waste storage.

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America's environmental movement, of course, remains stubbornly antinuclear, but it's not obvious how much that matters. Climate scientists have increasingly stepped up to act as a counterweight to antinuclear greens. In his new book, Kerry Emanuel writes, "Environmentalists must accept some measure of responsibility for today’s most critical environmental problem." Wrote Hansen, "The danger is that the minority of vehement antinuclear ‘environmentalists’ could cause development of advanced safe nuclear power to be slowed." As support for advanced nuclear as a climate solution grows, green leaders will have an increasingly hard time claiming that global warming demands continued subsidies for deploying wind and solar but not modest investments in developing and deploying advanced nuclear technologies.

By. Michael Shellenberger & Ted Nordhaus