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Comment by blakesterz | Hacker News Reader

"Current [fusion] reactors are approximately the size of a building"

I was under the impression there isn't a fusion reactor of any size anywhere yet, am I wrong?

There are many fusion reactors, just none that produce more energy than they consume.

Barring some random research breakthrough by a small team somewhere, ITER is probably the best bet for reaching positive net energy first: https://en.m.wikipedia.org/wiki/ITER

Indeed. I believe the smallest — most hobbyist fusors — are about the size of a suitcase.

Yeah, in fact many folks have created DIY fusors in their garages. Just hook any sort of energy harnessing device onto that and you can claim you've got a fusion reactor too!

https://makezine.com/projects/make-36-boards/nuclear-fusor/

There are several fusion reactors currently in existence and operational as of this day.

The problem is none of those reactors produce more energy than they consume.

Meaning they don't work. Meaning a "reactor" as we think of it—ie one accomplishing it's purpose of power generation—doesn't exist.

Nuclear reactors aren't necessarily used for power generation. The other applications of nuclear reactors are for example producing interesting elements or isotoopes, and irradiating things like cancer patients and physics experiments.

There's are also bioreactors and chemical reactors. It seems to me the term reactor is just used for a device that induces reactions.

The reactors work in that they produce measurable fusion reactions. They only don’t work in practical terms of being a power plant.

Yeah. That's exactly what I said. They don't work for what we intend to accomplish with them.

No, you said it doesn’t work as a reactor. It does.

The definition of “reactor” doesn’t require generating net positive power.

Incorrect. The experiments, largely, are not failures. The confinement devices are made to perform science. A fusion reactor power plant is expensive and it is much cheaper to design a reactor that works then to make a bunch of full-scale reactors that don’t. Also finding 10 billion dollars is hard.

Most of these devices use hydrogren most of the time, meaning the cross section of fusion even in high temperatures and densities will be low. If the goal of these devices was fusion energy they would all be using deuterium, at the very least.

The fields of plasma physics and materials have progressed to the point where a future reactor likely wouldn’t be a failure. Just look at W7-X and (in 10 years) ITER. Q=10 operation will likely be a very stressful test on ITER and it will likely only happen towards the end of its life (2035). Q=1 shots should be pretty early into tritium operation.

They may be referring to W7-X. The lower the aspect ratio of stellarators, the larger the major radius is. This makes a bigger, more expensive machine, but really blows the doors wide open on the largest engineering challenges (high neutron flux, high heat flux materials).

W7-X is this by the way:

https://en.wikipedia.org/wiki/Wendelstein_7-X

To add to what others have said, you can build a fusor [0] that sits on a tabletop. It just consumes energy, rather than producing it.

0: https://en.wikipedia.org/wiki/Fusor

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