With all the talk about the LHC possibly producing mini blackholes or magnetic monopoles that could potentially cause protons to decay spontaneously, I don't have enough nuclear physics background to know whether we are inherently safe, or if there is a real risk here.
Basically it's really really safe as far as byproducts. And yeah, it's a teeny sun, that instantly goes out if you stop feeding it juice, which sounds bad, but it's all the tiny stable particles, not the big slowly decaying scary ones.
If a fusion reactor is breached, the plasma will likely dump it's thermal energy into the air (likely this will cause a minor detonation, it's strength depends on the energy in the reactor and the amount of fuel). Additionally it'll leak some short lived isotopes and maybe create a few long live ones.
All in all, a detonated fusion reactor is likely save to walk in the same year it exploded, if not significantly earlier.
As for some unexpected pathway, energies like this are reached in stars all the time, and they don't spontaneously explode on a regular basis. If you're talking about a basic science experiment being the Great Filter -- well, maybe. I'm skeptical.
Well, they kind of do…
But really, the only reason why stars manage to stay in hydrostatic equilibrium is because of gravity, which we really can’t do on Earth so we settle for fancy magnetic confinement vessels.
On global scale it negligibly increased ever-present background radiation. It's not a good thing, but far from poisoning.
As a power source fusion is pretty good, which is why it’s such a target for research.
D-T fusion, which is the easiest to achieve and perhaps sustain, directly produces He nuclei (that is, alpha particles) and rather energetic neutrons at 14 MeV. Those neutrons, aside from being a form of ionizing radiation themselves, are bound to transmute some of the surrounding material into radioactive isotopes. So, I don't think that "no toxic or radioactive byproducts" is correct. However, the results are easier to handle than those of fission reactors.
You can't dismiss the technology based on that incident. Just like we don't ban cars because a lot of people don't operate them properly.
As far as I remember from the news at the time, the tsunami was terrible, but not unprecedented. If this obvious risk was ignored, what other risks are being ignored elsewhere?
The Japanese built Fukushima to standards that they felt were acceptable, and they were wrong and now the ocean is being polluted for the next thousands of years with the continuous risk of things getting worse at Fukushima.
In the same manner, they may be building this fusion reactor or LHC with what they feel is acceptable risk, but could they be wrong, with extremely catastrophic results? This is something I don't know but would love to know the answer to.
Then don't spread FUD?
"100M degrees" (Kelvin) corresponds to 10 KeV (kilo electron volts), which is an important figure to exceed for D-T fusion. D-T fusion which is the kind of fusion the ITER Tokamak (a forthcoming fusion reactor and international megaproject) intends to demonstrate.
An older fusion experiment, JET (Joint European Torus) reached these levels, so this does not break new ground, but it is important if this Chinese Tokamak is going to provide data useful for ITER.
I will note that it's rather unusual to refer to plasma temperature in Kelvin rather than in KeV. I edited this comment with a few more details to try to make it easier for laypeople to understand.
Off topic, but this distinction made me laugh. Like the difference between Kelvin and Celsius would throw everything off.
From ITER's wikipedia page:
>The goal of ITER is to demonstrate the scientific and technological feasibility of fusion energy for peaceful use. It is the latest and largest of more than 100 fusion reactors built since the 1950s. ITER's planned successor, DEMO, is expected to be the first fusion reactor to produce electricity in an experimental environment. DEMO's anticipated success is expected to lead to full-scale electricity-producing fusion power stations and future commercial reactors.
And from DEMO's wikipedia page:
>As a prototype commercial fusion reactor, DEMO could make fusion energy available by 2033.
1: https://en.wikipedia.org/wiki/Experimental_Advanced_Supercon...
2: https://en.wikipedia.org/wiki/ITER
3: https://en.wikipedia.org/wiki/DEMOnstration_Power_Station
A high temperature plasma represents a continuous supply of fusing atoms. The current research at ITER, this place, etc. are attempts to create a persistent environment for fusion. If they can do that, then it creates an environment where research can focus on 1) reduce the energy required to hold it at that temperature (which includes limiting how much plasma leaks out, since leaking plasma drops the temperature), and 2) work out ways to extract the energy created by fusion.
As I understand (and I could be wrong, it's been years since I last read about it), ITER plans to generate a net-negative energy situation (i.e. it'll never produce energy, just consume it) but hopes to create a sustainable plasma field at temperatures that cause fusion.
The temperature of a gas is essentially a measure of the constituent particles' kinetic energy. Higher kinetic energy = higher temperature. 10keV represents enough kinetic energy for the D-T atoms to collide fast enough that they overcome the Couloumb repulsion and fuse together.
I don't know much about fusion, but my guess is the 10keV is impressive because it is a self-sustaining fusion reaction rather than being impressive because of the absolute energy of the reaction?
edit: someone down the page mentioned that containment is the issue. In a CRT you are just accelerating an electron across a few thousand volt potential and slamming it into the screen.
In order to keep the plasma at the temperatures where fusion can occur, rather extreme measures have to be taken. In the Tokamak approach, the plasma is placed in a toroidal vacuum chamber, and "suspended" in the center of the torus by using electromagnets that line the Tokamak chamber's walls. At such high temperatures the plasma is so energetic that it is very hard to contain such fast moving particles. If the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly cools down to temperatures below where fusion can happen.
The immense engineering challenge here is to heat plasma to ridiculous temperatures, and keep it confined in a very small volume at great temperature and pressure to mimic conditions that give rise to nuclear fusion in the center of stars.
I see Wendelstein 7-x is attempting 30 minute burns soon https://www.ipp.mpg.de/4413312/04_18?c=4313165
This is not exactly true. Inertial confinement fusion has conditions that are similar to stars. The engineering challenge for magnetically confined fusion to keep the low density plasma confined for long time durations for fusion.
For anyone interested in further reading, look up the Lawson Criterion.
Sounds relieving. I used to think that «if the plasma "escapes" the confinement and contacts anything (ie. the walls of the Tokamak) it rapidly…» disintegrates everything around or, when the power is huge enough, causes an apocalypse…
Nuclear fission reactions can continue on their own for quite a while. This is one of the reasons they can be so dangerous.
[1] Unstable in the sense that it is hard to maintain fusion conditions, not in the Hollywood sense that it blows up if you look at it sideways.
Now, I don't expect politics to allow sharing of fusion energy to help other countries.
You are very wrong. ITER is a $20B international collaboration to construct an energy positive fusion reactor. The participants, including China the underwriter of the experiment detailed in this thread's article, are very much sharing.
But yes, the first ones to 'crack' the problem will have a head start in the commercial fusion power plant market, but I don't think it will last very long. As you say, most of the research is being published, and even if somebody manages to initially keep that final 'dot on the i' secret, it wouldn't take other researches long to figure it out.
It's probably not that easy; the reactors are extremely complicated and expensive to build, and I'm sure operating them isn't cheap either.
And the one thing I haven't heard much about yet is the yield - how much energy can it generate vs how much will it cost to run.
I don't think it'll be economically viable. I'll be happy to be proven wrong though.
The fact is, fusion generates neutron radiation that destroys the reaction vessel, making it an unviable technology. Nobody takes it seriously as a source of energy, aside from uninformed people. As cool as the idea of controlled fusion is, it is and will remain science fiction.
And really, you just sound like every crank ever who thought X technology was totally unfeasible and always would be -- until it wasn't. So currently attempts haven't found a solution to the reaction vessel destruction problem. That does not mean someone in the future couldn't figure that one out.
This is a regular tokamak design, with a high chance of success since we understand tokamaks very well at this point. Various startups have more speculative designs that deal with the issue in other ways.
The power density of an ARC reactor will be around 0.5 MW/m^3. In comparison, the power density of a PWR reactor vessel is 20 MW/m^3.
Replacing the entire inner vessel once a year would be an operational nightmare. For one thing, it ensures the building the reactor is in will have to be very large, with very large secondary bays where the intensely radioactive material of a spent reactor vessel can be moved and disassembled (generating radioactive fragments and dust).
http://www.askmar.com/Robert%20Bussard/The%20Trouble%20With%...
I hear sometimes contradictory hear-say on the lines of "unlimited energy", "reactor would have to be fed constantly".
If the cost is low, a brave new world with fusion replacing fossil generation as quickly as they can be built. Energy-inefficient processes like desalination and cracking water for hydrogen become attractive.
If the cost is very high, it may be that renewables have stolen fusion's market slot. In that case we'll see some national prestige projects, but against a broader renewable energy market.
Fusion might end up looking a lot like fission, but hopefully with a lower perceived safety risk and thus more public acceptance.
Granted, modern fission designs aren't actually unsafe, but that doesn't matter for PR purposes.
— random guy on Quora
https://www.quora.com/Is-there-a-limited-amount-of-fuel-for-...
The technical term for a "doughnut-shaped area" is "torus"; "tokamak" is an abbreviation for the Russian for, "toroidal chamber with magnetic coils".
- When two hydrogen nuclei combine, they produce an enormous amount of energy. That process is known as nuclear fusion.
- Light nuclei have to be heated to extremely high temperature, it is challenging to create a controlled, safe fusion reactor that offers more energy than it consumes. Once we have such we’d have a near-limitless source of clean energy.
- Nuclear fusion does produce radioactive waste. However, in contrast to fission produced wastes, they are short lived and decay to background levels in a very short time.
- Tokamaks try to do just that.
- While the products of the fusion reaction are short-lived, operating a fusion reactor will active materials in the reactor and create some longer-lived radioisotopes.
- Unlike a fission reactor, which is loaded with months to years worth of fuel, a fusion reactor would have fuel constantly injected. So operator action to stop injecting fuel would stop the nuclear reaction.
In some dystopian future, an AI figures out this is a most efficient use of matter and the entire Earth gets used as fuel for fusion reactions
>The ARC design aims to achieve an engineering gain of three (to produce three times the electricity required to operate the machine) while being about half the diameter of the ITER reactor and cheaper to construct. (Wikipedia)
It's not been built because of the $5bn or so cost, though given global warming / saving the planet type issues I'd be happy enough as a tax payer to have governments fund one and maybe knock 1% off the defence budget to counter that. It'd probably do more for world peace than churning out some more f35s.
Yes we have been building dozens of these. But that's also because it's fundamentally a very difficult project. Do you somehow expect airplanes to go from the Wright flyer to a jumbo jet in less than a dozen steps?
There's also been plenty of research into alternatives. Germany is building a stellarator.
There's also a whole cohort of startups looking at more speculative ideas.
I'm not saying there can't or shouldn't be more research into more alternatives. I am saying it's unreasonable to look at tokamak research as some sort of dead horse we're flogging.
On this note, do we have any reason to be particularly confident that magnetic confinement will ever break even and produce surplus energy? In nature fusion seems to occur through gravitational compression, so what makes us sure that we can simulate this by other means that will ever amount to more than just demonstrations?
"The ITER thermonuclear fusion reactor has been designed to produce a fusion plasma equivalent to 500 megawatts (MW) of thermal output power for around twenty minutes while 50 megawatts of thermal power are injected into the tokamak, resulting in a ten-fold gain of plasma heating power."
(somebody posted that video on another recent HN fusion thread)
Did the reactor produce more energy then was put into it? I just don't understand enough about the field to figure that out by reading the article.
Edit: I think this is what I meant: https://en.wikipedia.org/wiki/Lawson_criterion
I.e. going from sensor readings to inference of the plasma state.
I thought the stellerator had already achieved 100M Kelvin?
