In December 20, 1951, just outside the tiny town of Arco, Idaho, four 100-watt lightbulbs strung on a single cord flickered to life and then glowed brightly, becoming the first appliances ever powered by nuclear energy. The small group of scientists watching, employees of the Idaho National Laboratory (INL), toasted to a future powered by the splitting of atoms.

It would be a dream deferred. Nuclear power stalled in America amid highly publicized accidents and concerns about radioactive waste. But scientists at the INL quietly soldiered on, and now the tide may be turning: The imperative to limit greenhouse-gas emissions is sparking an atomic renaissance on the very site of nuclear energy’s birth.

Buoyed by an allocation of $1.25 billion in funding for reactor research from the 2005 Energy Policy Act, INL scientists are working to improve safety, boost efficiency, minimize waste, and decrease cost in a new generation of nuclear reactors. Even if renewable energy goes mainstream, INL researchers still believe nuclear will be essential for supporting the electrical grid’s base load—that portion of the nation’s electricity that must be supplied at a constant rate, in contrast to the variable supplies from the sun and wind. “Nuclear is the major base load–producing energy source that could reduce greenhouse-gas emissions,” says Kathryn McCarthy, INL’s deputy director for nuclear science and technology.

Unlike burning coal or other fossil fuels, fission—the breaking apart of atomic nuclei, the process underlying nuclear energy—emits no carbon dioxide. A nuclear reactor generates power from a cluster of fuel rods inside its core, each filled with uranium oxide. Every time an incoming neutron bombards one of the uranium atoms, the atom splits in two, expelling energy and releasing more neutrons, which in turn collide with other atoms and establish a chain reaction. The cumulative heat from this process boils water into steam, which spins a turbine to create electricity.

The fission of an atom of uranium is 10 million times as potent as burning an atom of carbon from coal, making nuclear power efficient and inexpensive—in principle, at least. The average cost of generating nuclear energy in the United States was less than two cents per kilowatt-hour in 2006, according to the Atlanta-based utility data provider Ventyx, which puts it on par with coal. Critics like Rocky Mountain Institute cofounder and chief scientist Amory Lovins dispute this apparent parity, arguing that the price of nuclear energy would increase if more plants were built. The current cost of delivering nuclear-generated electricity is low in part because many plants were paid for long ago, Lovins notes.

Nuclear’s day-in, day-out reliability makes it an essential companion to renewable energy, argues Burton Richter, winner of the 1976 Nobel Prize in Physics. “The sun doesn’t shine at night, and wind power is highly variable,” he says. “To meet our emissions goals, we’re going to have to grasp every arrow in the quiver, and nuclear is one of those arrows.”

Before that can happen, though, nuclear power will have to overcome the unresolved issue of how to dispose of radioactive fuel waste. In February President Obama deep-sixed the government’s long-standing plan to bury waste at Nevada’s Yucca Mountain after opponents argued that the strategy was too risky. “Now it’s time to start over and find a viable way to deal with used nuclear fuel,” says Patrick Moore, chief scientist at the sustainability consulting firm Greenspirit Strategies and a cofounder of Greenpeace. But finding an alternate solution could take years, and some observers concerned about nuclear waste’s effects on human health do not want to plunge ahead in the meantime. “I think there’s a solution out there; I just don’t think we’ve landed on it yet,” says Mary Woollen, executive director of the nonprofit group Keep Yellowstone Nuclear Free. “It’s foolhardy to ramp up the scale of nuclear power before the waste issue is resolved.”

That is exactly what the INL scientists are aiming to do, however, confident that their work is essential to the planet’s well-being. Their efforts focus on two new designs: the very-high-temperature reactor (VHTR) and the sodium-cooled fast reactor (SFR). Both incorporate inherent safety features to prevent core overheating and the release of radioactive material. The hope is that these new approaches will finally erase the memory of Three Mile Island and Chernobyl and eliminate some of the political opposition that has stymied the American nuclear power industry for three decades.

The VHTR, which is still in the planning stage, has a reactor core made of graphite, a substance that remains strong and stable even at high temperatures. Helium gas cools the reactor and transports heat to outside the core. The reactor uses uranium dioxide fuel particles that are also coated with graphite so they will not crack and release fission products even in extreme heat. As a result, VHTR plants will be able to heat helium to a temperature of up to 1000 degrees Celsius (1800°F)—nearly three times as high as existing reactors can go. The heat from the helium can then be used to create steam to drive a turbine. Unlike reactors of the Chernobyl type, the VHTR has a negative temperature coefficient, meaning that as the core temperature rises, nuclear reactions inside naturally begin to slow down. This feature ensures that the reactor never approaches a temperature that would trigger a meltdown. “No matter what humans do wrong,” McCarthy says, “if anything abnormal happens, the plant will shut itself down.”

The VHTR should produce electricity about 40 percent more efficiently than do most reactors in the United States. The heat it generates would also be useful for nearby industrial plants. VHTR plants could even produce hydrogen for fuel using high-temperature steam electrolysis, which breaks apart the bonds of water molecules; this process is 50 percent more energy-efficient than existing hydrogen production methods. In 2005 the Department of Energy authorized INL to build a VHTR plant. The prototype should be completed sometime between 2018 and 2021.

But first the INL team must surmount a slew of technical obstacles. For instance, hardy new alloys may be necessary to protect some surfaces inside the reactor. “Right now, materials don’t always exist to go with the kinds of temperatures and pressures they are talking about,” Richter says. Even if such materials are found, he adds, they might add millions of dollars to the still-unknown cost of constructing a VHTR power plant.