Slashdot Mirror
China's Fusion Reactor Reaches 100 Million Degrees Celsius (abc.net.au)
hackingbear shares a report from the Australian Broadcasting Corporation: The team of scientists from China's Institute of Plasma Physics announced this week that plasma in their Experimental Advanced Superconducting Tokamak (EAST) -- dubbed the 'artificial sun' -- reached a whopping 100 million degrees Celsius which is six times hotter than the core of the Sun. This temperature is the minimum required to maintain a fusion reaction that produces more power than it takes to run. The Chinese research team said they were able to achieve the record temperature through the use of various new techniques in heating and controlling the plasma, but could only maintain the state for around 10 seconds. The latest breakthrough provided experimental evidence that reaching the 100 million degrees Celsius mark is possible, according to China's Institute of Plasma Physics. "While the U.S. is putting new restrictions on nuclear technology exports to China, inventions and findings of EAST will be important contributions to the development of the International Thermonuclear Experimental Reactor (ITER)," writes Slashdot reader hackingbear. The reactor is currently being built in southern France with collaboration from 35 nations. According to the Australian Broadcasting Corporation, it is expected to be "the first device to consistently produce net energy, producing 500 megawatts of clean and sustainable power."
The protons in the core of the sun are in a temperature distribution, like a bell curve, and the average of this bell curve is way to cold for fusion. The only reason fusion happens is there are so many protons, a very few have freakishly high temperature way up the high end of the bell curve. Only those statistical outliers are fusing.
The Sun can be cooler because it has a couple of things going for it: it's optically dense and gravitationally confined. That is, the core is SO big and SO dense that radiation doesn't just leak heat out into space. So the plasma doesn't cool down immediately. Also, the plasma density is maintained by the weight of all the mass of the rest of the star.
Lab experiments, and in fact any plasma on earth, have neither of these advantages going for them.
That is why the Sun can maintain its fusion reaction and why it is so hard to create fusion on earth.
Fusion reactors are still generating neutrons.. activation is still a problem.
Most of the neutrons are absorbed by the lithium blanket. The lithium splits into helium-4 and tritium. The tritium is collected and fed back into the reactor.
Most structural parts exposed to thermal neutrons are made of zirconium, which has a very small neutron cross-section.
There is some problems with neutron activation from a fusion reactor, but way less than with fission reactors. There is no danger of a "meltdown" or any other catastrophic failure. The biggest concern is a tritium leak, but tritium isn't very dangerous, dissipates rapidly, doesn't bioaccumulate, and has a half-life of only 12 years.
Would I be willing to live next to a fusion reactor? Sure.