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

[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?

[Rick Modena]

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

[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.

[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]

That.

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

[Big A]

...

[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

[diablo rojo]

Seriously. I mean there's the whole "bottling a star" aspect, which in itself seems sci-fi, but that one piece of equipment will use both the hottest and coldest things in the universe at -452.2*F and +180,000,000*F at the same time.

I'm failing to understand how you contain a temperature that hot? Did we finally create Unobtanium?

[Strychnine]

Seriously. I mean there's the whole "bottling a star" aspect, which in itself seems sci-fi, but that one piece of equipment will use both the hottest and coldest things in the universe at -452.2*F and +180,000,000*F at the same time.

[Sean88gt]

Jesus. The majority of us are talking monkeys.

[Strychnine]

OK, fuck this.


I hate you, Aaron.

Germany is about to start up a monster machine that could revolutionize the way we use energy


for more than 60 years, scientists have dreamed of a clean, inexhaustible energy source in the form of nuclear fusion.

And they're still dreaming.

But thanks to the efforts of the max planck institute for plasma physics, experts hope that might soon change. Last year, after 1.1 million construction hours, the institute completed the world's largest nuclear-fusion machine of its kind, called a stellarator.

The machine, which has a diameter of 52 feet, is called the w7-x. And after more than a year of tests, engineers are finally ready to fire up the $1.1 billion machine for the first time. It could happen before the end of this month, science reported. Known in the plasma physics community as the "black horse" of reactors that use nuclear fusion, stellarators are notoriously difficult to build. The gif below shows the many different layers of w7-x, which took 19 years to complete:





from 2003 to 2007, as the project was being built, it suffered some major construction setbacks — including one of its contracted manufacturers going out of business — that nearly canceled the whole endeavor. Only a handful of stellarators have been attempted, and even fewer have been completed. By comparison, the more popular cousin to the stellarator, called a tokamak, is in wider use. Over three dozen tokamaks are operational around the world, and more than 200 have been built throughout history. These machines are easier to construct and, in the past, have performed better as a nuclear reactor than stellarators. But tokamaks have a major flaw that w7-x is reportedly immune to, suggesting that germany's latest monster machine could be a game changer.


how a nuclear-fusion reactor works

the key to a successful nuclear-fusion reactor of any kind is to generate, confine, and control a blob of gas, called a plasma, that has been heated to temperatures of more than 180 million degrees fahrenheit. At these blazing temperatures, the electrons are ripped from their atoms, forming ions. Normally, the ions bounce off one another like bumper cars, but under these extreme conditions the repulsive forces are overcome.



the ions are therefore able to collide and fuse together, which generates energy, and you have accomplished nuclear fusion. Nuclear fusion is different from what fuels today's nuclear reactors, which operate with energy from atoms that decay, or break apart, instead of fusing together. Nuclear fusion is the process that has been fueling our sun for about 4.5 billion years and will continue to do so for another estimated 4 billion years.

Once engineers have heated the gas in the reactor to the right temperature, they use super-chilled magnetic coils to generate powerful magnetic fields that contain and control the plasma. The w7-x, for example, houses 50 six-ton magnetic coils, shown in purple in the gif below. The plasma is contained within the red coil:




the difference between tokamaks and stellarators

for years, tokamaks have been considered the most promising machine for producing energy in the way the sun does because the configuration of their magnetic coils contains a plasma that is better than that of currently operational stellarators.




but there's a problem: Tokamaks can control the plasma only in short bursts that last for no more than seven minutes. And the energy necessary to generate that plasma is more than the energy engineers get from these periodic bursts. Tokamaks thus consume more energy than they produce, which is not what you want from nuclear-fusion reactors, which have been touted as the "most important energy source over the next millennium."

because of the stellarators' design, experts suspect it could sustain a plasma for at least 30 minutes at a time, which is significantly longer than any tokamak. The french tokamak "tore supra" holds the record: Six minutes 30 seconds.

If w7-x succeeds, it could turn the nuclear-fusion community on its head and launch stellarators into the limelight. "the world is waiting to see if we get the confinement time and then hold it for a long pulse," david gates, the head of stellarator physics at the princeton plasma physics laboratory, told science.

Check out this awesome time-lapse video of the construction of w7-x on youtube, or below:

[Strychnine]

Nope.. not yet... seriously, i just want to post something without that bullshit playing.

[Strychnine]

One more oughta do it...

[Strychnine]

Taking up space here to get off of the page with autoplay.

[46Tbird]

Crystal with "Forbidden Symmetry" Found in 4.5-Billion-Year-Old Meteorite



A crystal with an “unorthodox” arrangement of atoms has been discovered inside an ancient meteorite that crashed into a remote area of northeastern Russia thousands of years ago. This is only the second time a natural so-called quasicrystal has been found. The work is published in Scientific Reports this week.

To understand the difference between crystals and quasicrystals, imagine a tiled floor. Hexagon-shaped tiles (with 6 sides) fit neatly next to each other to cover the entire floor. But if you lay down pentagons (5 sides) or decagons (10 sides) next to each other, you’ll end up with gaps between the tiles. In ordinary crystals, the atoms are packed closely together in a repeated and orderly fashion. But with quasicrystals, “the structure is saying ‘I am not a crystal, but on the other hand, I am not random either,'” Princeton’s Paul Steinhardt says in a news release.

Researchers used to think that these structures were too fragile and energetically unstable to be formed through natural processes. That is, until Steinhardt and colleagues stumbled on a crystal with these “forbidden symmetries” in 2009 in a rock collected years earlier in Chukotka, Russia. Called icosahedrite, that quasicrystal had the 5-fold symmetry of a soccer ball, and it originated in an extraterrestrial body formed around 4.57 billion years ago.

Based on experiments with X-rays, the newly discovered quasicrystal has a structure that resembles flat 10-sided disks stacked in a column (pictured to the right). This 10-fold symmetry is an impossible structure in ordinary crystals. "When we say decagonal, we mean that you can rotate the sample by one-10th the way around a circle around a certain direction and the atomic arrangement looks the same as before,” Steinhardt explains to Live Science.

..

http://www.iflscience.com/space/crystal-forbidden-symmetry-found-45-billion-year-old-meteorite