Twenty-five years after Three Mile Island's near-meltdown stopped the industry cold (not a single U.S. plant has been approved since), nuclear energy is making a serious comeback. This fall, Congress is expected to start funding a $1.1 billion project to build a new breed of nuclear reactor. The design requirements represent a quantum leap: In addition to being safer and less vulnerable to terrorism than current nuclear plants, the new reactor must do double duty-generate electricity and crank out hydrogen, the presumptive automobile fuel of the future.
An international panel of scientists, led by the Department of Energy and dubbed the Generation IV Forum, began the process in 2001 by evaluating hundreds of futuristic reactor concepts and whittling the list down to six. This fall, the DOE will choose one for a demonstration plant, to be built at the Idaho National Engineering and Environmental Laboratory.
None of the designs is a slam dunk, says Idaho Lab's nuclear energy director Ralph Bennett, but the clear favorite is the Very High Temperature Reactor (VHTR). As its name implies, the VHTR is designed to generate intense heat: cooled by helium, it would operate at 1,000°C—twice as hot as today's water-cooled reactors. Since extreme heat is required to snap the chemical bonds of various compounds and release hydrogen, the reactor is ideal for producing the new fuel, says Finis Southworth, the DOE's VHTR expert.
In addition to turning turbines to make electricity, the intense heat generated by the VHTR reactor will also power an adjacent hydrogen plant, where one of two chemical processes will produce 10 tons of hydrogen an hour, Southworth says. (The demo plant will kick out a modest 2 tons.) And the process yields hydrogen without producing greenhouse gases—the drawback of today's hydrogen plants, which create high temperatures by burning fossil fuels, such as coal and natural gas.
Another selling point: Thanks to the configuration of its ura-nium fuel, the VHTR would be meltdown-proof, claims nuclear engineer Andrew Kadak of MIT. In today's reactors, the uranium is stuffed into hollow rods of zirconium, a metal that catches fire if the coolant is somehow drained off, resulting in a potentially disastrous radiation release, like the one at Three Mile Island. In the VHTR, the uranium will be either in the form of "pebble beds"—stacked pellets of uranium covered in graphite—or "prismatic blocks"—uranium encased in 3-foot-high, 2-foot-wide hexagons of graphite.
Using graphite instead of zirconium to cradle the uranium means a Three Mile Islandâ€style disaster is impossible; instead of combusting in the absence of coolant, graphite allows nuclear heat to radiate away faster than it is produced. This "passive" safety system requires no frantic scrambling by personnel to save the day, making the VHTR more difficult to sabotage.
But the journey from drawing board to lights-on is likely to be rocky for whichever design is chosen. Skeptics point to the thorny issue of where to stash radioactive waste. (Nuclear proponents hope to bury it beneath Yucca Mountain, a federally approved storage facility in Nevada.) And a demonstration reactor will take years to build; the DOE hopes to flip the switch in 2015, just in time for the anticipated rollout of hydrogen-fueled automobiles.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.