Scientists and political leaders in China are searching for ways to generate enough energy to fuel the country’s rapidly growing economy while simultaneously cutting power plant emissions. China emits more carbon dioxide than any country on the planet except the United States. According to the World Bank, 16 of the 20 most heavily air-polluted cities on Earth are in China.
The Chinese are responding with nuclear power.
But not just any old nuclear power. Gone are the days of large, concrete cylinders with slim waistlines and super-hot rods cooling off in pools of water. The Chinese are implementing a revolutionary new technology known as pebble-bed nuclear reactors.
Power for the Future
In late 2003, China announced plans to build 30 nuclear power plants by 2020. To keep pace with expected economic growth, a team of Chinese scientists advising the nation’s government has estimated the country will require more than 200 new plants by 2050.
According to the September 2004 issue of Wired magazine, the Chinese scientists believe that by 2050 the nation will need to generate nearly as much nuclear power from future plants alone as is currently being generated by nuclear power across the globe.
Meeting that goal would be inordinately expensive with conventional nuclear technology. Conventional nuclear power plants rely on extremely hot fuel rods to fire the heart of the reactor. This internal fuel-rod core must be cooled in water, which becomes scaldingly hot, corrosive, and highly radioactive.
For safe containment of the radioactive byproduct, conventional nuclear power plants require pressurized water tanks, extensive containment-area sprinklers, large pressure domes, and constant monitoring. Investments in such technologies and practices by nuclear utilities have resulted in a remarkable history of safe and emissions-free power generation across the Western world. The price tag, however, has been high.
How Pebble-Bed Reactors Work
Chinese scientists are confident they can reduce the costs of nuclear power while at the same time making an empirically safe and environmentally friendly product even safer and more environmentally friendly.
The innovation, known as a pebble-bed reactor, replaces fuel rods with baseball-sized graphite balls filled with small uranium shavings. Cooling pools of water utilized in conventional reactors are replaced by inert helium. The nuclear reactions in pebble-bed reactors can safely generate one-third more energy than conventional nuclear reactors, because helium can reach much higher temperatures than the temperature at which water pools will burst containment pipes.
From a safety perspective, according to Wired, “The usual layers of what the industry calls engineered safety are superfluous [with pebble-bed reactors]. Suppose a coolant pipe blows, a pressure valve sticks, terrorists knock the top off the reactor vessel, an operator goes postal and yanks the control rods that regulate the nuclear chain reaction–no radioactive nightmare. This reactor is meltdown-proof.”
The remarkable safety of pebble-bed reactors is due to their geometry, low fuel density, and small size in comparison to conventional nuclear power plants. Explains Wired, “The key trick is a phenomenon known as Doppler broadening–the hotter atoms get, the more they spread apart, making it harder for an incoming neutron to strike a nucleus. In the event of a catastrophic cooling-system failure, instead of skyrocketing into a bad movie plot, the core temperature climbs to only about 1,600 degrees Celsius–comfortably below the balls’ 2,000-plus-degree melting point–and then falls. This temperature ceiling makes [pebble-bed reactors] what engineers privately call walk-away safe. As in, you can walk away from any situation and go have a pizza.”
According to Zhang Zuoyi, director of the Chinese pebble-bed reactor project, as quoted in the Wired article, “In a conventional reactor emergency, you have only seconds to make the right decision. With [the pebble-bed reactor], it’s days, even weeks–as much time as we could ever need to fix a problem.”
“This unusual margin of safety isn’t merely theoretical,” observed Wired. “INET’s engineers have already done what would be unthinkable in a conventional reactor: Switched off [the pebble-bed reactor’s] helium coolant and let the reactor cool down all by itself.”
Envisioned During Manhattan Project
Ironically, the theoretical basis for the revolutionary pebble-bed technology was developed at the very birth of the nuclear age. Farrington Daniels, a chemist participating in the Manhattan Project, proposed the pebble-bed concept for nuclear power before the atomic bombs were dropped on Japan. The Oak Ridge National Laboratory was sufficiently impressed that it approved funds and manpower to build a working version of the pebble-bed reactor in 1945.
However, before the reactor could be built, a U.S. Naval Academy scientist proposed the alternative method of super-hot rods and cooling-water pools. With naval backing during a time of world war, the rod-and-water approach was approved and pebble-bed technology was put into mothballs.
Now, 60 years later, pebble-bed technology is back at the scientific forefront.
Conventional nuclear power plants continue to be safely built and operated worldwide. But in the United States, no nuclear power plant has been approved for construction in the United States since 1979, largely due to the media’s mischaracterization of the Three Mile Island incident and the popularity of the fictional Hollywood film, “The China Syndrome.”
Economics Favor Nuclear Power
Andrew Kadak, who teaches nuclear engineering at MIT, is convinced pebble-bed reactors will never be a candidate for a course he teaches, “Colossal Failures in Engineering.” Kadak is currently working with the Chinese group and advising the U.S. Department of Energy, which is considering building a pebble-bed reactor at the Idaho National Engineering and Environmental Research Lab.
“The industry has been focused on water-cooled reactors that require complicated safety systems,” Kadak said. “The Chinese aren’t constrained by that history. They’re showing that there’s another way that’s simpler and safer. The big question is whether the economics will pay off.”
Most promising for the future of pebble-bed reactors is that the technology is economical as well as safe. Pebble-bed reactors do not require billion-dollar containment facilities or the multitude of other safety mechanisms required by conventional nuclear reactors.
Moreover, pebble-bed reactors utilize a modular design well-suited for economical mass-production. As noted by Wired, “Despite some attempts at standardization, the latest generation of [conventional nuclear power plants] are still custom-built onsite.
“By contrast, production versions of [pebble-bed reactors] will be barely a fifth their size and power, and built from standardized components that can be mass-produced, shipped by road or rail, and assembled quickly. Moreover, multiple reactors can be daisy-chained around one or more turbines, all monitored from a single control room. In other words, Tsinghua’s power plants can do the two things that matter most amid China’s explosive growth: get where they’re needed and get big, fast.”
“Why worry about foreign fuel supplies when you can have safe nukes rolling off your own assembly lines?” asks Wired. “Why invoke costly international antipollution protocols when you can have motor vehicles that spout only water vapor from their tail pipes? Why debate least-bad alternatives when you have the political and economic muscle to engineer the dream?”
James M. Taylor ([email protected]) is managing editor of Environment & Climate News.
