It's useless science Friday in my head - Welcome to the show.

[NoClassic]

I believe that is the primary functions of the magnets. The plasma is kept is suspension so it is never in contact with any of the reactor vessel material.

http://www.ipp.mpg.de/748929/plasmagefaess

[Big A]

...

[Strychnine]

That.

The plasma never touches a material. It is contained with the magnetic field.

[Grimpala]

That.

The plasma never touches a material. It is contained with the magnetic field.

So hypothetically, what occurs with a 'melt down' of this machine?

[Strychnine]

So hypothetically, what occurs with a 'melt down' of this machine?

Nothing really. If the plasma touches the walls it will cool and stop the reaction.

One researcher has described the magnetic confinement problem in simple terms, likening it to squeezing a balloon – the air will always attempt to "pop out" somewhere else. Turbulence in the plasma has proven to be a major problem, causing the plasma to escape the confinement area, and potentially touch the walls of the container. If this happens, a process known as "sputtering", high-mass particles from the container (often steel and other metals) are mixed into the fusion fuel, lowering its temperature.

At these temperatures, electrons are entirely separated from the atomic nuclei and the gas becomes a plasma, but if the plasma touches a metal wall of the reactor, it immediately cools off, stopping any fusion reactions.

Edit: I was just thinking about losing the magnetic con Apparently someone on Reddit went super deep on an answer to that.


Generally this;

The answer is pretty much "very little". The plasma has a high temperature, but the amount of energy in it isn't massive, so there's very little chance of it breaching the vessel. Plasma strikes on the inner wall are things which happen in research reactors already.

But worst case?

The magnetic field is supported by superconducting magnets which have to be kept at temperatures close to absolute zero in order to carry the electric current that produces the field. The heat of the escaped plasma will cause the wires to stop superconducting and all of the energy of the magnetic field will very quickly be dumped into heat in the wires, boiling off the cryogens. This is called a quench and it can seriously fuck up the magnet and cryogen system. (Come to think of it, if the reactor has an outer cryogen tank that's basically at absolute zero and a plasma at some hundred million degrees then this reactor probably has one of the steepest temperature gradients in the universe- this kind of thing just doesn't happen naturally).

Anyway- the expanding cloud of gas. When the gas expands it cools very very quickly and ceases fusing almost immediately, stopping the fusion reaction dead in its tracks. Unfortunately, the fuel is a mixture of hydrogen isotopes- deuterium with one proton and one neutron, and tritium with one proton and two neutrons. Deuterium is stable and found in nature and is actually harvested from the hydrogen in sea water since that's a readily available source, but tritium is actually unstable and highly radioactive.

A tritium leak into the environment is bad because hydrogen is so reactive it makes it really hard to clean up. Greenpeace has a good fact sheet about the risks of tritium leaks, and as pro-nuclear energy as I am, I have to acknowledge that tritium leaks are really fucking bad.

When radioactive material gets out into the environment you want it have a very very short half life, or a very very long one. That way it'll either all decay away immediately, or it'll decay so slowly that it's not really irradiating anything. Tritium has a half-life of 12 years, which is neither fast nor slow, it's right in the sweet spot of being terrible. That tritium will bond with oxygen to make water molecules. Radioactive water molecules. These will make their way into the water table and are impossible to remove because they look just like any other water molecule... except sometimes it'll spit out a high energy electron. If this water is in your body, then that radioactive decay will shoot a high energy electron through you, destroying organic molecules and scrambling your DNA. At the least, this can increase your risk of cancer a marginal amount. At its worst, it could kill you.

Best case scenario: the reactor is destroyed but the gas is contained by some secondary containment vessel so the tritium leak doesn't happen, and the gas can be collected and processed properly. Anyway, even in worst case scenario I can imagine for a fusion reactor failure is still a million times less dangerous than fission reactor meltdown.

[Rick Modena]

That 7-x looks like the Millennium Falcon...wait... maybe that's what powers the Falcon... C8<[

[Grimpala]

Nothing really. If the plasma touches the walls it will cool and stop the reaction.

Edit: I was just thinking about losing the magnetic con Apparently someone on Reddit went super deep on an answer to that.

But worst case?

Sounds like this is significantly safer than fission. How long before this is a viable mass energy source?

[Ruffdaddy]

Sounds like this is significantly safer than fission. How long before this is a viable mass energy source?

Itll be ready about the time renewables are main stream enough to make it obsolete

[Strychnine]

Sounds like this is significantly safer than fission. How long before this is a viable mass energy source?

There are a bunch of companies out there working on fusion reactors and I think all are targeting 2020-2025

LPP Fusion (Lawrenceville Plasma Physics) - the target is to make LPP Fusion with a commercial system 4 years after net energy gain is proved. The hop is two years to prove net energy gain. Then 2019-2022 for a commercial reactor (2022 if we allow for 3 years of slippage). They could lower energy costs by ten times.

Lockheed Compact Fusion has a target date of 2024 and made big news recently with some technical details and an effort to get partners.

Helion Energy 2023 (about 5 cents per kwh and able to burn nuclear fission waste)

Tri-Alpha Energy (previously talked about 2015-2020, but now likely 2020-2025)

General Fusion 2023 (targeting 4 cents per kwh)

EMC2 Fusion (Released some proven physics results, raising $30 million)

Dynomak Fusion claims that they will be able generate energy cheaper than coal. They are not targeting commercialization until about 2040.

MagLIF is another fusion project with good funding but without a specific target date for commercialization.

There is Muon Fusion research in Japan and at Star Scientific in Australia.
There is the well funded National Ignition facility with large laser fusion and there is the International Tokomak project (ITER).

General Fusion in Vancouver has its funding with Jeff Bezos and the Canadian Government. (As of 2013, General Fusion had received $45 million in venture capital and $10 million in government funding)

IEC Fusion (EMC2 fusion) has its Navy funding (about $2-4 million per year)

As of August 15, 2012, the Navy had agreed to fund EMC2 with an additional $5.3 million over 2 years to work on the problem of pumping electrons into the whiffleball. They plan to integrate a pulsed power supply to support the electron guns (100+A, 10kV). WB-8 has been operating at 0.8 Tesla

http://nextbigfuture.com/2015/08/lockheed-martin-compact-fusion-reactor.html

[Forever_frost]

I'm really waiting for things like this to be done in orbit so if they go out of control, it's not that big of a deal. Tritium in the water supply sounds like a very bad thing

[Craizie]

I'm really waiting for things like this to be done in orbit so if they go out of control, it's not that big of a deal. Tritium in the water supply sounds like a very bad thing

A hail of radioactive debris sounds lovely.

[Grimpala]

It's like the CERN Project. If a group of scientists screw up, we all go. I wouldn't mind it if someone killed every one of them.

I believe, but don't hold me to it, that they have created a few very small black holes. I don't think they were very stable and did not last very long.

Sent from my HTC One_M8 using Tapatalk

[Strychnine]

It's like the CERN Project. If a group of scientists screw up, we all go. I wouldn't mind it if someone killed every one of them.

I'm confused. Are you saying you think the science being done at CERN poses a threat to humanity and that you would rather see the scientists dead than continue their work

[YALE]

Yes. Kill them with fire!

Are you talking about the possibility that the large hadron collider might create a black hole? That isn't a risk. It was a theory supported by bad math.

Itll be ready about the time renewables are main stream enough to make it obsolete

We still need it for space travel.

A hail of radioactive debris sounds lovely.

It doesn't make radioactive waste material like a fission reactor.

[Grimpala]

It doesn't make radioactive waste material like a fission reactor.

I think he's talking about a melt down in space which then rains radioactive debris into the atmosphere.