Really?

Technology Review: TR10: Traveling-Wave Reactor

Technology Review has a short article about a proposed new reactor design that sounds almost too good to be true:

As it runs, the core in a traveling-­wave reactor gradually converts nonfissile material into the fuel it needs. Nuclear reactors based on such designs "theoretically could run for a couple of hundred years" without refueling, says John G­illeland, manager of nuclear programs at Intellectual Ventures.

Gilleland's aim is to run a nuclear reactor on what is now waste.

...the traveling-wave reactor needs only a thin layer of enriched U-235. Most of the core is U-238, millions of pounds of which are stockpiled around the world as leftovers from natural uranium after the U-235 has been scavenged. The design provides "the simplest possible fuel cycle," says Charles W. Forsberg, executive director of the Nuclear Fuel Cycle Project at MIT, "and it requires only one uranium enrichment plant per planet."

I wonder how you stop the reaction, though...