Slashdot Mirror
Nuclear Fusion Real Soon Now
Mr. A. Coward writes "Researchers at the
National Ignition Facility are attempting to produce nuclear fusion. They'll focus 192 amplified lasers on a pellet of frozen hydrogen. 'NIF experiments will be the first to create fusion that gives off more energy than it takes in.' That will have to be quite a bit, since it will take 500 trillion watts to ignite the pellet in the first place. The facility has been plagued with delays, and so far only 4 of the 192 lasers have been completed. Researchers believe they will first achieve fusion sometime around 2014."
Umm, fusion is most certainly NOT impossible. Stand outside tomorrow around noon and look up at the sky. See that big burning thing that hurts your eyes? That's a nuclear fusion reaction.
Ahh, hasn't break even been passed experimentally quite some time ago?
m l
http://www.jaeri.go.jp/english/fusion/fusion.ht
This claims break even in 1996, and 1.25 power increase in 1998 in the JT-60 tokamak..
And this article seems to be stating they plan to hit breakeven in 2014 or further out.. hmmm.. perhaps they mean some special kind of break even, like the first ones using our method, or in the US, or something like that..
National Ignition Facility home page
National Ignition Facility project status and photo gallery with lots of pictures
LLNL Science on High Energy Lasers
Fusion happens commonly in research labs. What hasn't happened yet, is getting more energy out than it took to create the fusion, in a controlled, energy-generating environment.
Let's see...
Assuming that '500 trillion' means 500 x 10^12 watts... They said it would be for a 'few billionths' of a second: maybe 2 x 10^-9 seconds?
Am I counting wrong, or does that come out to about a million watt-seconds, or 0.277 kilowatt-hours?
I consume more energy than that makin' coffee.
Never attribute to malice that which can be explained by mere idiocy.
As Mr. Potts says, Watts are a unit of power. 500 trillion Watts is the power being put into the reaction by the lasers. Energy is not the same thing as power. Power is energy divided by time.
According to the article, the beams will be fully on "only for a few billionths of a second". For a naive estimate of the total energy being output by the lasers, we can simply multiply (500 GW) * (2 ns).
Now, this yields a quantity with dimensions of energy: (500 GW) * (2 ns) = (1 kJ). To get a handle on this, it is the amount of energy that is output in heat and light by a 100W light bulb shining for ten seconds.
For a scenario Slashdotters are familiar with, it's the amount of heat generated by a 1 GHz Athlon thunderbird in 12 seconds.
Power is not the same as energy. It is energy per unit time. It is rubbish to say there will have to be a large energy output because the input power is high. By way of example, 500 trillion watts for a femtosecond = 500 joules. This is not an unreasonable amount of energy, contrary to the attempt to imply otherwise by shouting '500 trillion'.
Actually, if you read the article 2014 is someone else's estimate, and the scientists hope for results substantially sooner.
/.er actually read the article?
I know, I know, suggest a
Ooh, a sarcasm detector. Oh, that's a real useful invention.
Compare this to the efforts of JET the Joint European Torus project, which achieved breakeven (Q=1) during 1997 (good explanation of fusion milestones here). JET's successor, ITER aims to achieve Q of at least 10, paving the way for commercial-scale power generation.
The only thing that worries me about ITER is the level of bureaucracy exhibited, but perhaps this is to be expected from a multi-national consortium.
ITER are standing on the shoulders of giants, NIF are discussing specifications for a step-ladder.
Strictly speaking, while maser is now also a word, 'microwave laser' is a perfectly valid term since the word 'microwave' merely describes a type of light (with light generically referring to photonic waves, i.e. EM waves).
"Stumble before you crawl"
I'm sorry, I just can't let this go uncorrected. A fusion power plant is incapable of 'meltdown' in any way, shape or form. Fission plants can meltdown because they contain all of their fuel within the reactor vessel (think "all my gas is stored in my engine"). A fusion plant, on the other hand has its fuel piped to the reaction chamber ("my gas is in my gas tank, at the other end of the car"). At any given point there will be less than 10mg of plasma in the reaction vessel. This is not enough to damage the vessel, let alone melt anything at all.
Since 3D Realms announced Duke Nukem Forever and Valve announced Team Fortress 2...
Karma: It's all a bunch of tree-huggin' hippy crap!
I think he ment things like fuel cell cars. Yes they exist, but they still arn't practical, and probably never will be. Since the whole fuel cell car idea is flawed. IE it's not freedom from fossil fuels since the practical way to get hydrogen is from fossil fuels. And even then that takes a lot of energy. They also arn't that efficient, 60% peak and thats not factoring the energy used to make the hyrdogen.
Fusion power does even come into play, since the only true break from fossil fuels and to make it renewable is from splitting water. And that means we need a super clean, cheap and massive amount of power. Hense fusion, and even then you are still wasting energy making hydrogen, just means we have clean energy, even though making the hyrdrogen and then running the fuel cell puts us at a loss. So we can't really expect the promise of fuel cell/ hydrogen economy to come true till fusion gets up and running.
Also far as hydrogen fuel cell cars they were promisied long ago, first 2000, then they all said 2004, now they say end of decade. Having worked on hybrid cars for years I and most anyone I know who works on hybrids and fuel cells agree fuel cell cars arn't going to happen. Especialy since a hydrogen IC engine beats a fuel cell in about all ways. Sure there is prototypes, and very complete ones at that, (fuel cell ford focus) and even some test fleets, but they are still nothing practical.
For now the hydrogen economy is a nice fun thing for people like George Bush to throw out there. Make it sound good, oil companies love it, it's all good.
The future for fuel cells are in laptops and cell phones were you by a small hydrogen cartrige. For uses where portable power is needed, and it must be clean. Things like stationary fuel cell powerplants are the silliest things ever. Since they need powerplant to make the hydrogen to power them.
IANAP just a technician on Omega so I'm not exactly sure of the intricate details of the problems with computer simulations etc. but from what I gather the computer simulations of ICF targets are notoriously difficult to match with experiments due to the incredibly complex problem of modeling hydrodynamic instabilities in the implosion.
- "Hear that?! The percolations are imminent! Cease your ingress!"
You can buy pure heavy water for about $300 per Kg. Making tritium from that is simple. The AC is delusional, you don't need to make it atom-by-atom. Just put some heavy water need a reactor for a couple of days and you're all set!
As I source I give you this link Heavy Water: A Manufacturers Guide for the Hydrogen Century.
As for his "ideal" proton-proton reaction. First of all it's not in the slighest bit ideal. A Deuterium-Deuterium reaction is the ideal one. You can't make a proton-proton reaction anyway - you need neutrons. And guess what you do with the neutrons? You attach them to protons and make: you guessed it, deuterium!
The only thing the sun does, which we would not do in a lab is convert protons to neutrons by adding electrons. That's the only thing that you are not going to see mass produced in a lab. The sun does not do proton-proton fusion, you can't do that. What the sun does it take protons convert half ot them to neutrons, and hook them up with protons to make deuterium. Then it does deuterium-deuterium fusion.
-Ariel
Fusion power generation, as currently being developed is nothing like this. It's still a sensible investment for the next few centuries and as a step to better things, but it's not the panacea you suggest and you harm the credibility of science and technology by claiming it is.
Likely 21st century fusion power plants will burn tritium and deuterium. While both are isotopes of hydrogen and deuterium is acceptably common in the universe (1 in 10000 or so atoms if I recall correctly) we are not burning hydrogen. Tritium is radioactive with a 12 year half-life, so is basically not found in the universe except where it is being formed (in stars mostly). To make commercial quantities of it, you irradiate lithium 6 with neutrons producing helium and tritium. Lithium is reasonably common on Earth, but not super-abundant. The costs of extracting and purifying lithium, and in particular lithium 6 are not negligible, although we are unlikely to run out for a while.
So, effective fuel is lithium and deuterium. Both are reasonably plentiful, but neither is cost-free.
Now the tricky bit. The deuterium-tritium reaction produces a helium nucleus (alpha-particle) which is no problem and a neutron. We need a decent proportion of those neutrons to breed more tritium, but inevitably, some of them will end up hitting things other than the lithium target. When they do, they tend to make what they hit radioactive. Thus, once your reactor has been running for a few years, all of the inner structure, the lithium tanks and so on, are medium-level radioactive waste. The neutron irradiation also weakens these structures, so they need periodic replacement. Gigawatt for Gigawatt, it's a lot less radioactive waste than a fission reactor produces (and no plutonium to manage), but its not nothing, and the cost of the equipment and expertise to manage this periodic replacement with acceptable staff safety and so on is also not nothing.
Water, by the way, is not a byproduct of fusion reactors.
The final issue is safety. Here the big win is that there are no realistic disaster scenarios on the scale of a fission reactor melt-down or someone using reactor-produced plutonium to make a fission bomb. There are all the hazards common to fossil fuels and fission associated simply with running a large industrial plant -- things falling on people, leaking chemicals, etc. A tritium leak is still a real hazard, and a molten lithium leak or fire would be pretty unpleasant, and the medium-level waster would need to be managed, but it is a lot better than fission.
So, not a panacea, but a likely move forward, and I don't think we do any good by describing it as a panacea and rasing false expectations.