Nuclear Physics

Nuclear Fusion Power Closer to Reality Say Two Separate Teams

28 Jan , 2010 by

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For years, scientists have been trying to replicate the type of nuclear fusion that occurs naturally in stars in laboratories here on Earth in order to develop a clean and almost limitless source of energy. This week, two different research teams report significant headway in achieving inertial fusion ignition—a strategy to heat and compress a fuel that might allow scientists to harness the intense energy of nuclear fusion. One team used a massive laser system to test the possibility of heating heavy hydrogen atoms to ignite. The second team used a giant levitating magnet to bring matter to extremely high densities — a necessary step for nuclear fusion.

Unlike nuclear fission, which tears apart atoms to release energy and highly radioactive by-products, fusion involves putting immense pressure, or “squeezing” two heavy hydrogen atoms, called deuterium and tritium together so they fuse. This produces harmless helium and vast amounts of energy.

Recent experiments at the National Ignition Facility in Livermore, California used a massive laser system the size of three football fields. Siegfried Glenzer and his team aimed 192 intense laser beams at a small capsule—the size needed to store a mixture of deuterium and tritium, which upon implosion, can trigger burning fusion plasmas and an outpouring of usable energy. The researchers heated the capsule to 3.3 million Kelvin, and in doing so, paved the way for the next big step: igniting and imploding a fuel-filled capsule.

In a second report released earlier this week, researchers used a Levitated Dipole Experiment, or LDX, and suspended a giant donut-shaped magnet weighing about a half a ton in midair using an electromagnetic field. The researchers used the magnet to control the motion of an extremely hot gas of charged particles, called a plasma, contained within its outer chamber.

The donut magnet creates a turbulence called “pinching” that causes the plasma to condense, instead of spreading out, which usually happens with turbulence. This is the first time the “pinching” has been created in a laboratory. It has been seen in plasma in the magnetic fields of Earth and Jupiter.
A much bigger ma LDX would have to be built to reach the density levels needed for fusion, the scientists said.

Paper: Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies

Sources: Science Magazine, LiveScience

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Thameron
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Thameron
January 28, 2010 12:24 PM
“a clean and almost limitless..” Almost limitless? Maybe. Clean? Not as much as people think. You see that neutron up there in that drawing? Where do you suppose it’s going? One possible place it might be going is to collide with the nucleus of another atom and making it radioactive. Now I am no engineer so I don’t know what materials they are thinking of making these fusion reactors out of, but they have to make them out of something and if you expose a material to a strong neutron flux long enough it will become activated i.e. fusion reactors will produce nuclear waste. Probably not as much as fission reactors, but not none. So if producing less… Read more »
Vedic
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Vedic
January 28, 2010 12:50 PM

Yes, from what I understand leaving the ‘spare’ neutron is still going to leave radioactive waste…

Has anyone heard know how ‘focus fusion’ is coming along?

Manu
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Manu
January 28, 2010 1:12 PM

In a tokamak design like Iter, the neutrons will help in-situ production of tritium, in two ways: absorption by a deuterium nucleus; and reaction with lithium coating of the plasma chamber.
http://en.wikipedia.org/wiki/ITER#Reactor_overview
(see more detail on the French page)

This might be used too in a pinch machine, but I don’t see how it could be done with inertial confinement.

All neutrons wouldn’t probably be absorbed, leading to irradiation of chamber material. This is not to be shrugged off, but it’s almost nothing in comparison with fission reactors. The spent fuel from these is a bigger problem by several orders of magnitude.

Surak
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Surak
January 28, 2010 1:37 PM

My ignorant understand is that the radioactive waste from these fusion reactions generally has a much shorter half life than those of fission.

Dark Gnat
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Dark Gnat
January 28, 2010 1:37 PM

Yes, we get more radiation from the Sun and cosmic sources than what a Fusion reacotr would produce.

Fusion Power Plants would have the greatest impact on reducing carbon emissions and reliance on oil from unfriendly nations.

solrey
Member
January 28, 2010 1:41 PM
The Dense Plasma Focus is another method for achieving fusion. The progress on focus fusion appears to be going well, Vedic. The donut magnet creates a turbulence called “pinching” that causes the plasma to condense, instead of spreading out, which usually happens with turbulence. This is the first time the “pinching” has been created in a laboratory. It has been seen in plasma in the magnetic fields of Earth and Jupiter. Actually, the plasma pinch has been created in laboratory experiments for decades. Even the filaments in a novelty plasma ball are the result of the pinch effect. The first creation of a z-pinch in the laboratory may have occurred in 1790 in Holland when Martinus van Marum… Read more »
Torbjorn Larsson OM
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Torbjorn Larsson OM
January 28, 2010 1:43 PM
Well, LDX with its large plasma volume doesn’t sound like an “inertial fusion ignition” experiment. AFAIU it is a tokamak competitor. I can’t really get excited about inertial fusion reports since I learned that they have to overcome a fundamental instability, the e Rayleigh–Taylor instability of interstellar clouds and weather inversions. Before they report doing that, it’s a dud. if you expose a material to a strong neutron flux long enough it will become activated i.e. fusion reactors will produce nuclear waste Yes, that is what they will rely on to produce the needed tritium (which is radioactive), until and if they can get the cleaner deuterium-deuterium reaction going. While there’s no beef that this is a major… Read more »
Thameron
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Thameron
January 28, 2010 1:47 PM

The spent fuel obviously will not be a problem as it is with fission plants, but there will still be activation products to deal with. The vessels of conventional fission plants become very radioactive due to their neutron exposure and need to be disposed of carefully. Materials which can withstand the necessary pressures and temperatures to hold in a fusion reaction are probably somewhat constrained so they may not be able to use something more resistant to neutron activation.

My point though is that fusion energy will not be ‘clean’ in the sense that solar energy is clean i.e. producing no waste except what was necessary to make it.

Thameron
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Thameron
January 28, 2010 1:55 PM
Torbjorn – “For example, tritium has a half-life of 4.5 days” No, actually the half life of Tritium is 12.33 years. I am not sure where you got that 4.5 day figure. Tritium getting into the water (not to mention the people) is a problem that will certainly need to be addressed. My quote about the 10 years was facetious, because fusion power was always 10 years away. In truth I have no idea when or if humans will get that technology to work. As with Mars it may well be not in my lifetime. I’d love nothing more than to have us master it and put it on our interplanetary shuttles. Really I would, but I do… Read more »
doomfistinc
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doomfistinc
January 28, 2010 3:09 PM

Yeah, just forget about it. The waste products aren’t rainbows and butterflies, so we shouldn’t do it.

It is still magnitudes cleaner than anything except solar that we have access to. It isn’t like there are going to be millions of tons of garbage left over.

It IS clean. If people can label new ways to use coal as “clean”, fusion is CLEANERIFFIC^100

clatonium
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clatonium
January 28, 2010 3:20 PM

Almost limitless? Maybe. Clean? Not as much as people think. You see that neutron up there in that drawing? Where do you suppose it’s going? One possible place it might be going is to collide with the nucleus of another atom and making it radioactive.

I hear boron is an excellent neutron absorbent material. In a fission reactor its a poison, in this case it would reduce radioactive byproducts.

The Eclectic Exterminator of Stupid Electricians
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The Eclectic Exterminator of Stupid Electricians
January 28, 2010 5:40 PM
clatonium said; “Almost limitless? Maybe. Clean? Not as much as people think. You see that neutron up there in that drawing? Where do you suppose it’s going? One possible place it might be going is to collide with the nucleus of another atom and making it radioactive. I hear boron is an excellent neutron absorbent material. In a fission reactor its a poison, in this case it would reduce radioactive byproducts.’ What rubbish. Unsubstantiated fear of radioactivity by fusion is a nonsense. All of the radiation is contained in the reactor itself, and none will be dangerous to the environment. (unlike fission) Most of the radiation is caused by the gamma rays from the fusion reaction. Nonetheless, the… Read more »
Lawrence B. Crowell
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Lawrence B. Crowell
January 28, 2010 5:45 PM
Yeah that neutron is a problem in more ways than one. About 80% of the energy from this reaction is carried off by the neutron. Since the particle is neutral it is not entirely easy to get that energy. You can put heavy water around the reaction chamber and let neutrons thermalize the water. But this is an inefficient process. I spent considerable effort about 10 years ago in getting an alternative fusion process considered. The reaction involves lithium. The reactions are the following Li^7 + p –> (Be^8)^* –> 2He^4 or Li^6 + D –> (Be^8)^* –> 2He^4, where (Be^8)^* is unstable and decays into alpha particles which are charged and their energy extracted by magneto-hydrodynamic methods.… Read more »
CrazyEddieBlogger
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January 28, 2010 9:25 PM

Another interesting Fusion approach is General Fusion – http://www.generalfusion.com/t5_general_fusion.php

The idea is completely out of left field, but after it settles down in your brain it is actually pretty sensible. loud, but sensible.

LC – I’ve heard about Li fusion a bit before, I’d love to hear more.

CrazyEddieBlogger
Member
January 28, 2010 9:38 PM

here’s a nice movie showing General Fusion’s progress so far

http://link.brightcove.com/services/player/bcpid3924348001?bctid=5659122001

The Eclectic Exterminator of Stupid Electricians
Member
The Eclectic Exterminator of Stupid Electricians
January 28, 2010 9:42 PM

The best thing about lithium fusion is it might help with the availability of commercial helium !!

DrFlimmer
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DrFlimmer
January 29, 2010 3:29 AM
But, unlike Hydrogen and its isotopes, Lithium is quite less abundant. This is a massive problem! Btw: Fusion plants are always 50 years away from now… whenever “now” is. Hopefully this doesn’t go on forever . Indeed, fusion would solve almost every problem, we face today. Hopefully we achieve it, before it’s too late! (Hm. Shall I, or shall I not? Ah, what the heck: “Pinched plasma” would not really work to get fusion. Such pinches are highly unstable. They can actually squeeze the plasma, but only to split and cut it. “Sausage instability” – as a keyword. I don’t think this would work for fusion. You need a stable plasma – instabilities are the things you want… Read more »
Lawrence B. Crowell
Member
Lawrence B. Crowell
January 29, 2010 5:01 AM
Lithium is actually rather abundant, though not as abundant as heavy water. In fact it is a component of metal ions in sea water. The D-T cycle energetically is D + T –> He^4(@ 3.5MeV) + n(@ 14.1 MeV) while a lithium cycle woiuld be Li^6 + D –> (Be^8)^* –> 2He^4(@ 22.4 MeV) The input energy of the D+T cycle is about 1MeV and for the Li cycle this is 2-3 times as much. In the Li cycle the energy output per nucleon mass is half that of the D-T cycle, making it appear less attractive. So from one perspective the Li cycle is less effective, but the energy output is not in an electrically neutral neutron… Read more »
Richard Kirk
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Richard Kirk
January 29, 2010 5:18 AM
I have had a quick look at the General Fusion site. I would have thought a converging shockwave would have to be amazingly symmetric to converge successfully. A real shock wave would surely suffer from Rayleigh-Taylor instabilities. I was more convinced by the Bussard “PolyWell” proposal put to Google. That, and Bussard was a cool guy. Lawrence’s HMD generator is neat. It always seems a shame to generate even fission energy, and then just use it to heat a steam engine. Much nicer if we can get some of the energy out directly. As for regular fusion – the gamma and the neutron are both very penetrating radiations. I worry that it may not produce regular waste, but… Read more »
Aodhhan
Member
Aodhhan
January 29, 2010 6:34 AM

Something so simple, made so complex.

It boils down to making the most energy with as little fuel as possible.

Every solution has waste, and some have kewl ways of dealing with it.

LBC….
You’ll soon find out Li-6 is being tossed out in lieu of Li-7. While both are stable, an exothermic reaction typically isn’t something most people want to deal with at a large scale. Unless you’re building bombs. smile

…also your Li-6 equation has one too many arrows wink
Should be: reactants –> products + energy

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