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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.
So serious question: how many oceans will that boil? It's one thing to have the moon that hot, it's another to have the head of a pin that hot. Or are the just going after temperature quantity rather than size/mass?
You're on the right track. Temperature != Heat. The plasma in the outer magnetosphere of the earth has a temperature of thousands of degrees kelvin, but it doesn't melt a spacecraft that's in it. Why? It's sparse. The average kinetic energy of particles in the plasma is high (i.e., high temperature) but the power per unit area that strikes the spacecraft is very low.
That being said, the plasma inside a Tokomak can certainly melt something. That's (part of) why there is so much effort put into magnetic confinement.
If it weren't for deadlines, nothing would be late.
You joke, but actually plasma fusion reactors are quite safe -- far safer than their fission counterparts.
Even if all of the matter inside a fusion reactor were to fuse simultaneously -- a physical impossibility -- the worst that would happen is significant damage to the reactor building. There simply isn't enough matter inside the reactor at any time to do worse.
If it weren't for deadlines, nothing would be late.
Not just instabilities, but lack of a mechanism to capture and feed the excess energy back into the device, which was not a goal of the experiment.
When all you have is a hammer, every problem starts to look like a thumb.
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.
Zirconium isn't a common structural metal.
Of course not. It is heavy and expensive. It is only used where low neutron cross section is important.
Presumably it would have to be alloyed
Yes, most commonly with tin and niobium. Sometimes with chromium, nickel, or iron.
then you have to concern yourself with the cross section of the alloying parts as well.
Indeed. Most zirconium alloys are 95% or more zirconium for this reason.
More info here: Zirconium Alloys
Zirconium sits right below titanium in the periodic table, and shares many properties, including high strength and resistance to corrosion.
Just below Zirconium is Hafnium, which has one of the biggest neutron cross sections. Hafnium is used as a neutron absorber, and hafnium salts can be used as a neutron poison to quickly shutdown thorium salt reactors in an emergency.
To sustain enough steam to power the world you would need, not unsurprisingly, the entire world's current supply of oil, gas, nuclear fission, solar, wind, hydro, etc. Because... that's pretty much what we use it to do (I'm excluding all losses here, for simplicity).
One you achieve fusion, you can literally power the entire world from 867 tonnes of hydrogen per year. That's maybe a shipping container full of hydrogen. Something we can pull out of the ocean.
For reference, we would need to burn 12 billion tonnes of oil, 10.4 billion tonnes of gas or even 7000 tonnes of uranium to do the same.
Pretty much the only thing more powerful is complete utilisation of E=mc^2 - merging antimatter and matter and capturing the blast. You'd only need 3 tonnes of antimatter to power the world in that instance.
https://www.forbes.com/sites/s...
Fusion, if it can be made to work, could power the entire world from one power station. Of course, that's not what would happen - we'd just end up USING UP all that energy and every country would have half a dozen of them. We'd end up synthesising rare materials and doing all the things we can't currently do because of the sheer amount of energy they require, rather than actually just settle on current usage coming from one place.
But it literally is an order of magnitude more energy than the nuclear reactors we have now, which are orders of magnitude more energy than even coal and oil, which are orders of magnitude more energy than anything else.
And it looks like we could viably do it inside the next century or so.
With that amount of energy, you could easily obliterate the planet, or fire things into space like they were paper planes.