A New, Much Safer Nuclear Reactor Design From China
But they're also pursuing a second, more audacious course. Physicists and engineers at Beijing's Tsinghua University have made the first great leap forward in a quarter century, building a new nuclear power facility that promises to be a better way to harness the atom: a pebble-bed reactor. A reactor small enough to be assembled from mass-produced parts and cheap enough for customers without billion-dollar bank accounts. A reactor whose safety is a matter of physics, not operator skill or reinforced concrete. And, for a bona fide fairy-tale ending, the pot of gold at the end of the rainbow is labeled hydrogen.
A soft-spoken scientist named Qian Jihui has no doubt about what the smaller, safer, hydrogen-friendly design means for the future of nuclear power, in China and elsewhere. Qian is a former deputy director general with the International Atomic Energy Agency and an honorary president of the Nuclear Power Institute of China. He's a 67-year-old survivor of more than one revolution, which means he doesn't take the notion of upheaval lightly.
"Nobody in the mainstream likes novel ideas," Qian says. "But in the international nuclear community, a lot of people believe this is the future. Eventually, these new reactors will compete strategically, and in the end they will win. When that happens, it will leave traditional nuclear power in ruins."
Now we're talking revolution, comrade.
Known as China's MIT, Tsinghua University sprawls across a Qing-dynasty imperial garden, just outside the rampart of mirrored Blade Runner towers that line Beijing's North Fourth Ring Road. Wang Dazhong came here in the mid-1950s as a member of China's first-ever class of homegrown nuclear engineers. Now he's director emeritus of Tsinghua's Institute of Nuclear and New Energy Technology, aka INET, and a key member of Beijing's energy policy team. On a bright morning dimmed by Beijing's ever-present photochemical haze, Wang sits in a spartan conference room lit by energy-efficient compact fluorescent bulbs.
"If you're going to have 300 gigawatts of nuclear power in China - 50 times what we have today - you can't afford a Three Mile Island or Chernobyl," Wang says. "You need a new kind of reactor."
That's exactly what you can see 40 minutes away, behind a glass-enclosed guardhouse flanked by military police. Nestled against a brown mountainside stands a five-story white cube whose spare design screams, "Here be engineers!" Beneath its cavernous main room are the 100 tons of steel, graphite, and hydraulic gear known as HTR-10 (i.e., high-temperature reactor, 10 megawatt). The plant's output is underwhelming; at full power - first achieved in January - it would barely fulfill the needs of a town of 4,000 people. But what's inside HTR-10, which until now has never been visited by a Western journalist, makes it the most interesting reactor in the world.
In the air-conditioned chill of the visitors' area, a grad student runs through the basics. Instead of the white-hot fuel rods that fire the heart of a conventional reactor, HTR-10 is powered by 27,000 billiards-sized graphite balls packed with tiny flecks of uranium. Instead of superhot water - intensely corrosive and highly radioactive - the core is bathed in inert helium. The gas can reach much higher temperatures without bursting pipes, which means a third more energy pushing the turbine. No water means no nasty steam, and no billion-dollar pressure dome to contain it in the event of a leak. And with the fuel sealed inside layers of graphite and impermeable silicon carbide - designed to last 1 million years - there's no steaming pool for spent fuel rods. Depleted balls can go straight into lead-lined steel bins in the basement.
Wearing disposable blue paper gowns and booties, the grad student leads the way to a windowless control room that houses three industry-standard PC workstations and the inevitable electronic schematic, all valves, pressure lines, and color-coded readouts. In a conventional reactor's control room, there would be far more to look at - control panels for emergency core cooling, containment-area sprinklers, pressurized water tanks. None of that is here. The usual layers of what the industry calls engineered safety are superfluous. 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.
Zhang Zuoyi, the project's 42-year-old director, explains why. 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 dense core of a conventional reactor, the effect is marginal. But HTR-10's carefully designed geometry, low fuel density, and small size make for a very different story. 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 HTR-10 what engineers privately call walk-away safe. As in, you can walk away from any situation and go have a pizza.
"In a conventional reactor emergency, you have only seconds to make the right decision," Zhang notes. "With HTR-10, 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. INET's engineers have already done what would be unthinkable in a conventional reactor: switched off HTR-10's helium coolant and let the reactor cool down all by itself. Indeed, Zhang plans a show-stopping repeat performance at an international conference of reactor physicists in Beijing in September. "We think our kind of test may be required in the market someday," he adds.
wired.com
Rock_nj: I'm not a big fan of nuclear, but this sounds pretty interesting. A design that is suppossedly free of meltdown potential with passively designed safety systems and doesn't have potential for steam leaks, is much less expensive to build and operate, etc. This is a form of nuclear power that might just gain acceptance, even in the U.S. |
