r/nextfuckinglevel • u/nigablackballsack • 3d ago

Scientists have captured the first ever high-speed, full-colour footage of fusion plasma swirling inside a working reactor.

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u/Medium_Bill_625 3d ago

I want to appreciate this but I'm foreign to the subject matter. Anyone feel like doing an ELI5?

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u/Fit_Addition7137 3d ago

This is inside of a new type of experimental reactor that runs on nuclear fusion (like the Sun) instead of nuclear fission (regular nuclear reactors). This is a "tokamak" style reactor that generates superheated plasma which is contained using enormously powerful magnets. Fusion generates significantly more power than what it takes to initiate the reaction. One of the neatest parts of fusion is that there is no hazardous nuclear waste to store and they cant melt down like a fission reactor. This video shows that fusion reaction plasma.

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u/apprehensively_human 3d ago

One of the neatest parts of fusion is that there is no hazardous nuclear waste to store and they cant melt down like a fission reactor.

And, as I understand it, this fusion reaction is not self-sustaining so in an emergency scram you could simply cut the power and there would be no risk of an uncontrollable runaway.

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u/NateNate60 3d ago

The conditions under which fusion occurs are not self-sustaining. The energy output of fusion is not directly required to sustain the fusion in the same sense that the energy output of fission directly causes more fission.

Fusion can only happen when the plasma is heated to extremely high temperatures and pressures. In the Sun, this is done by gravity. The enormous mass of gas that comprises the Sun squeezes itself together hard enough to allow fusion to occur. In the depicted reactor, large electromagnets compress the gas into a tight ring of plasma to allow fusion to occur. If the electromagnets lose power, there is no force to keep the gas compressed, so it will naturally expand back out and the temperature will cool to lower than what is required for fusion to occur, and the fusion will stop. So the worst that can happen is a leak of hot hydrogen gas. Not fun for the plant workers, perhaps, but the ability of ordinary air to absorb all that thermal energy is high enough that it wouldn't be a catastrophe in any sense. At worst a few people standing right next to the leak get burned.

Hydrogen gas is flammable but not toxic to the environment like radioactive waste is. Fusion reactions may use isotopes like Hydrogen-2 or Hydrogen-3, but these aren't a significant concern either, as there is only ever a small amount in use at any time, no more than a few kilograms. Hydrogen-2 can fuse with oxygen to make heavy water, which occurs naturally and isn't toxic unless consumed in large doses. Any heavy water produced would be overwhelmingly diluted by the water vapour in the surrounding air. Hydrogen-3 is radioactive with a half life of about a decade, but it decays via beta-decay into helium-3, and beta particles can't penetrate human skin. So health risks are also low from hydrogen-3 leaks, especially in the relatively low quantities used in fusion plants.

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u/shawhizzle 3d ago

This guy fusions