I’m standing 20 feet from the brightly glowing core of a laboratory nuclear test reactor the size of a van, and the Geiger counter next to me is going nuts. But no worries, I’m told. The light, visible on a nearby monitor hooked up to a camera inside the reactor, is not from nuclear fission; it is harmless emission from electrons zipping out of the core and shedding their energy into the water that surrounds it. And the stream of particles eliciting the shriek from the Geiger counter is not from the reactor at all. Just for a giggle, the reactor manager has placed the detector next to a Fiestaware cup, which happens to be one of many everyday items that are mildly radioactive. He keeps it on hand to tease visitors. I am actually getting less radiation here than I would on the beach or in an airplane.

You’ll have to forgive the folks at Oregon State University’s Radiation Center for having a little fun. Nuclear power fell into a long funk after the partial core meltdown at the Three Mile Island reactor in Pennsylvania in 1979. All new nuclear plant construction in the United States came to a halt, and before the industry could recover, the 1986 reactor breach at the Chernobyl nuclear plant in Ukraine seemed to seal the fate of nuclear power in this country. Now the technology is hot again—this time in a good way—because it produces virtually no carbon emissions and it backs us away from the turbulent politics and economics of oil.

OSU’s nuclear engineers are basking in that glow. While the industry was in deep freeze, they were pressing ahead with one of the most promising emerging technologies in energy: micro-size nuclear reactors, fully functional power plants a good deal closer to the size of the test reactor I’m standing near. It is a far cry from the standard nuclear plant—the size of a small town, cranking out enough electricity to power a major city—not to mention the even bigger plants going up in China and France.


Given the economies of scale in the power industry, why would anyone want to go teeny? “There are economies of small, too,” says Jose Reyes, chairman of OSU’s nuclear engineering department and chief technology officer at nearby NuScale Power, a commercial spin-off of the department. For one thing, Reyes explains, miniaturized nuclear plants are small enough to mass-produce, driving down costs, and they can be shipped just about anywhere by truck or boat, even to locations that are off the grid. Also, micro nukes can be designed to run a long time without maintenance or refueling. They could be sealed like a big battery and buried underground for as long as three decades, so terrorists could not get into them and nuclear waste could not get out. A spent micro nuke could simply be plucked out of the ground and shipped whole to a waste-processing or recycling facility anywhere in the world; the old one could be swapped out for a new one, cartridge-style. In contrast, a conventional nuclear plant requires several years of customized design and construction, and at the end of its life several years more are needed to dismantle it and decontaminate the massive site around it. Toshiba, Hyperion Power Generation, Sandia National Labs, and TerraPower—a company underwritten in part by Bill Gates—also have downsized nuclear reactor concepts in the works.

Micro nukes are more reliable than wind power, cheaper than solar, and much easier to operate than conventional nuclear plants.

Initially, micro nukes are likely to be installed in clusters as safer, simpler replacements for existing commercial reactors that need decommissioning. But in the coming decade, nukelets like NuScale’s may well eclipse solar and wind as the green energy of choice, bringing plentiful electricity to billions of people who lack it and possibly powering individual neighborhoods within cities.

Micro nukes that put out as little as a few mega­watts—instead of the 1,000 megawatts of a typical conventional nuclear plant—are a fresh spin on an old idea. Hundreds of similar devices are already operating around the globe. Many are laboratory test reactors like the one I stood beside at OSU; others provide power to submarines, ships, and even U.S. and Russian military outposts. These custom-built devices are not nearly cheap enough to be commercially viable, however. Moreover, the military versions generally don’t come close to meeting civilian standards for safety, usually relying on less-stable forms of uranium that could be too easily converted for use in a dirty bomb. About a decade ago, the U.S. Department of Energy and the Japanese government started quietly pushing their researchers to find a way to commercialize small nukes.

NuScale’s reactor stands to be the first of the new-age nuclear power plants to come on line. Like mainstream reactors, it is a “light water” design: The reactor is pressurized and filled with plain water that flows past the core, where the radioactive decay of uranium-235 generates intense heat. The heat boils a separate tank of water and turns it to steam, which in turn drives turbines that produce electricity. But there are differences. A conventional plant requires a vast, complex array of pumps, pipes, and valves to move enormous quantities of water between the reactor vessel, a separate steam-generating chamber, and a cooling tank. NuScale keeps things simpler with a tall, thin, single-vessel design. Water heated by the core ascends in a chimneylike metal structure inside the reactor, then spills over the top of the chimney and sinks back down along the inside walls of the reactor to repeat the journey. High pressure inside the reactor prevents the superheated water from boiling. As the water climbs over the top of the chimney in the NuScale reactor, it passes over a long coil of pipe, transferring much of its heat to water inside the coil. Lower pressure in the coil allows the water to boil, and the resulting steam travels up the pipe to power a turbine.

This simplified design is as efficient as that of a conventional nuclear plant. NuScale claims it will be able to produce power at about seven to nine cents per kilowatt-hour—roughly the same as big nuclear plants, only a few cents more than the cheapest modern natural gas–fired or coal-fired plants, and one-third the cost of a typical diesel generator. Michael Corradini, who heads the nuclear engineering program at the University of Wisconsin in Madison, notes that while the economics of micro nukes make sense, the biggest advantage to the approach may be that there is so little to go wrong with it. “The NuScale design has a lot of inherent safety, and that makes it very appealing,” he says.