The MIT Technology Review had an interesting article on a Traveling-Wave Reactor. 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. This reactor would run over 100 years between refuelings. What I think interesting is this came out of a privately funded think-tank, rather than the government labs.
Wave of the future: Unlike today’s reactors, a traveling-wave reactor requires very little enriched uranium, reducing the risk of weapons proliferation. (Click here for a larger diagram, also on page 3). The reactor uses depleted-uranium fuel packed inside hundreds of hexagonal pillars (shown in black and green). In a “wave” that moves through the core at only a centimeter per year, this fuel is transformed (or bred) into plutonium, which then undergoes fission. The reaction requires a small amount of enriched uranium (not shown) to get started and could run for decades without refueling. The reactor uses liquid sodium as a coolant; core temperatures are extremely hot--about 550 ºC, versus the 330 ºC typical of conventional reactors.
Credit: Bryan Christie Design Multimedia
Watch an animation showing the atomic reactions that would take place inside a traveling-wave reactor, and hear John Gilleland describe the processes.
A diagram of a traveling-wave reactor.
Read the full article here: http://www.technologyreview.com/energy/22114/?nlid=1842

Credit: Bryan Christie Design Multimedia


Read the full article here: http://www.technologyreview.com/energy/22114/?nlid=1842
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