It’s still too early to know whether the disaster at Japan’s Fukushima Daiichi power plant will have the effect of making the world more cautious about using nuclear energy or speed efforts to create a safer alternative to existing reactor technology. In last weekend’s Ideas section, a graduate student from MIT who has been studying the history of nuclear engineering told us she hopes it’s the latter, and that the nuclear industry can break out of the so-called "technological lock-in" that has caused it to stagnate since World War II. Ashley Finan told us about a number of different kinds of reactors being developed, including one being built in China, called the pebble-bed reactor, which was featured in the Times on Thursday.
The pebble bed model is a type of high-temperature gas-cooled reactor, or HTGR for short. Unlike the vast majority of nuclear reactors around the world, which use water to both cool their fuel rods and moderate the fission process, HTGRs can be cooled passively in the event of an emergency even if there’s no electricity to power the process.
As the Times describes it:
Rather than using conventional fuel rod assemblies of the sort leaking radiation in Japan, each packed with nearly 400 pounds of uranium, the Chinese reactors will use hundreds of thousands of billiard-ball-size fuel elements, each cloaked in its own protective layer of graphite.
The coating moderates the pace of nuclear reactions and is meant to ensure that if the plant had to be shut down in an emergency, the reaction would slowly stop on its own and not lead to a meltdown.
The reactors will also be cooled by nonexplosive helium gas instead of depending on a steady source of water — a critical problem with the damaged reactors at Japan’s Fukushima Daiichi power plant. And unlike those reactors, the Chinese reactors are designed to gradually dissipate heat on their own, even if coolant is lost.
HTRGs like the one being built in China have been attempted before, starting in Germany in the 1960s, but all efforts so far have stalled or been abandoned. In the United States, the Department of Energy is currently working with General Atomics and Westinghouse on related concepts as part of the so-called "Generation IV" initiative.
People like Finan, who see the world’s dependence on conventional light water technology as something of a historical accident, hope these innovative designs will gain traction in the coming years, and help break the nuclear industry out of its rut. For now, it looks like China may be leading the way.