Let a Thousand Reactors Bloom
Explosive growth has made the People's Republic of China the most power-hungry nation on earth. Get ready for the mass-produced, meltdown-proof future of nuclear energy.
wired.com
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... |
