U.S. to Rejoin the ITER Fusion Project

spiro_killglance writes: "BBC news is reporting here, that the USA may be about the rejoin the International Thermonuclear Experiment Reactor project. The USA left the ITER consortinum in 1999 when it bulked at the 10 Billion dollar price tag. Canada, Europe and Japan continued in the project, downscaling it to a cheaper 4.5 Billion dollars. The project claims to be the final step before commcercial reactors are possible, although the price tags might still be daunting to utility companies. ITER is designed to generate bursts of fusion energy, producing over 10 times the ammount of energy used to generate the fusion reaction (a Q factor >10), will not quite reach ignition (a self sustaining fusion reaction, or Q=infinity), but should pave the way for devices that will."

Do we want Q=Infinity?

[Catiline]

As you run up Q, doesn't the radioactive output also rise? IIRC, the particles are mostly netrinos, but still... I don't want to give angry Luddites [slashdot.org] more reasons to want to take away my tech toys.

Not to mention which, if you thought Chernobyl was a big disaster, just imagine what would happen with a breach on one of these babies! I don't think radioactive plasma would just melt a big hole in the ground....

Re:Do we want Q=Infinity?

[bofh31337]

I haven't kept up with the current design iterations of ITER, but I think the thing to remember is we are talking about Q_effective and not Q_actual. The main confusion is when we talk about Q in science and in engineering, they both use a different definition. The scientific definition is only counting the power to the plasma and not the energy for the lasers, fuel injectors, and everything else.

Yes, I think we do.

[Spamalamadingdong]

As you run up Q, doesn't the radioactive output also rise?

Depends what the reactants are. If you are burning deuterium with tritium (or D-D) you are emitting neutrons (D-D yields He-3 and a neutron, D-T yields He-4 and a neutron). Whether you create radioactives or not depends what those neutrons hit. You can get some neutron spallation (neutron hits something in a nucleus and tosses it out, transmuting the nucleus into something radioactive) or just neutron capture; however, you could control the results by selecting the composition of the materials exposed to the neutron flux. In a D-T burner you are going to have to replace the tritium you burn, which is usually done by capturing the neutrons with lithium. IIRC, Li-6 + n -> He-4 + tritium.

The antinukes would have to be crazy to be worried about neutrinos; their favorite energy source (old Sol) streams countless numbers of them through their bodies every second. This is not to claim that some of these people aren't crazy...

Fusion plasma won't melt a hole in the ground. By the time you dump air into the vacuum of the tokamak torus, the plasma will have been quite thoroughly quenched; you might have a few micrograms of tritium to worry about, but it has a half-life of about 12 years so it isn't much of a concern except over a relatively short term.

Re:Do we want Q=Infinity?

[PhuCknuT]

Radioactive plasma wouldn't melt a big hole in the ground. It probably wouldn't even burn down the building. In the event of a containment loss, fusion will stop instantly. Hot plasma coming into contact will cold air outside the chamber would quickly cool, all you would need is a nice ventilation system.

Plasmas almost can't get out of control

[TheBoquaz]

Work was done on this question at General Atomics last year. I believe it was found that adding a very small amount of neon to the plasma will stop the reaction in a matter of nanoseconds. With no harmfull effects at all. It effectively turns the reactor into one big neon light. It was quite a thing to see (via CCTV cameras in the reactor of course). With the cost of these reactors, they don't want the plasma to even touch the wall, let alone have the chance to eat through it. It's far easier to just add a little neon to the vessel, than to try to control any sort of energy surge. It took less than 5 minutes to have the reactor ready to go again, and it worked fine.

Re:Do we want Q=Infinity?

[joshamania]

The problem with fusion reactions isn't so much controlling the reaction, but keeping the reaction going. These folks aren't wrapping a magnetic bottle around a hydrogen bomb here. A "breach" in a fusion reactor will result in the reaction stopping, and perhaps some spilled fuel locally.

Fusion reactors will not explode...the energy they create is not "explosive" but rather maintained and constant.

...ish.

scale.

[perlyking]

10 billion doesnt seem so much when you think of $379bn on "defence".

Re:scale.

[MarkusH]

10 billion doesnt seem so much when you think of $379bn on "defence".

Especially since it is now actually closer to $4.5 billion that would be spread over three years. I just hope that the US won't make any unreasonable demands to get back into the game, like demanding that it be built in the US instead of Japan or Canada like the plans is now.

Re:scale.

[AntDaniel]

In 1999, the US balked at Iter's $10bn price tag. Since it left the project, Iter scientists have revised the project and the expected cost now stands at about $4.5bn.

Sounds like my company and estimating a quote for a user. "Hmmm, it's gonna cost 15bn. I know they won't go for that so we'll tell them 10bn."
"Oh my god, they didn't go for it. Okay let's try 4.5bn"

Fusion reactor

[bofh31337]

A common misconception about fusion reactor is that there are no negative byproducts of its use. this is simply not true. The tokamak fusion reactor would have extremely dangerous core due to neutron and proton radiation. You would have to have one heck of a system of shielding for this to be useful. Any thoughts on what would work best in the fuel?

Re:Fusion reactor

[PD]

Any thoughts on what would work best in the fuel?

Spammers and trolls.

Over-simplification

[Spamalamadingdong]

A common misconception about fusion reactor is that there are no negative byproducts of its use. this is simply not true.

Is there any technology which has no negative byproducts?

The tokamak fusion reactor would have extremely dangerous core due to neutron and proton radiation. You would have to have one heck of a system of shielding for this to be useful.

You could say the same thing about a solar furnace; the focus would be extremely dangerous due to thermal radiation. It doesn't mean that it isn't trivial to keep yourself safe from it. Direct neutron and proton radiation is simply not a problem. Indirect exposure, say from leakage of tritium or corrosion of used reactor parts, is another issue. Lots of chemical processes have nasty intermediate products, so it's not like industry doesn't have plenty of experience managing such things.

Any thoughts on what would work best in the fuel?

The easiest fuel to ignite is deuterium-tritium. If you are concerned about radioactive byproducts and you don't mind building a much bigger and more expensive reactor, you could use boron-11 and protium; B-11 + p -> 3 He-4 + . This would give you a neutron-free reaction, at the cost of very high temperatures required to ignite the plasma and very rapid heat loss due to X-rays from the multiply-ionized boron nuclei.

Re:Fusion reactor

[Yarn]

Deuterium/Tritium is the easiest to get fusing, but some people have suggested using helium-3. The reasons for this is that although you get less energy out, you also get far less neutron radiation. Mostly gamma rays.

Gamma rays matter less than neutrons because they don't cause what they hit to become reactive.

Re:Fusion reactor

[emmons]

UW-Madison (which has the largest fusion studies program in the nation) seems to be rather interested in H-3, so much so that the Fusion Technology Institute [wisc.edu] here has designed a device [wisc.edu] for mining H-3 from the moon. Interesting stuff, check out the website.

If only it were that simple...

[Spamalamadingdong]

... some people have suggested using helium-3. The reasons for this is that although you get less energy out, you also get far less neutron radiation. Mostly gamma rays.

It was my impression that He-3 + D -> He-4 + p + yielded all of its energy in the charged reactants, which further heats the plasma instead of being lost to the chamber wall (as photons and neutrons are). BTW, thanks for reminding me of He-3, I'd missed that earlier [slashdot.org].

Gamma rays matter less than neutrons because they don't cause what they hit to become reactive.

I hate to break this to you, but depending on the energy of the photon and the composition of the target, it can. If the gamma ray has enough energy to eject a nucleon from a nucleus in the target yielding a radioisotope, rest assured that some fraction (however infinitesimally small) will do so. Photons can also raise nuclei into metastable states, from which they decay some time later with the emission of some other form of radiation (usually another gamma ray, IIRC). If you go through a table of the isotopes, you'll find a bunch of curious things regarding various elements; you might want to do that on your own, just to make sure that your schooling isn't interfering with your education.

Re:If only it were that simple...

[Yarn]

OK, I ignored nuclear photon absorption, it's a pretty rare phenomenon, compared to neutron absorption.

I just have a tendency to ignore nuclear physics because I have messed with it so long (worked with cyclotrons in my school holidays). I'm far more interested in optics.

One interesting aspect of affects of photons on nuclei is the possibility of simulated gamma ray emission... think of the weapons you could make with that stuff!

Re:If only it were that simple...

[Winged Cat]

Problem: if you have He-3 + D, you're also going to get an occasional He-3 + He-3 or D + D, the latter of which emits neutrons...and, thus, potential radioactivity (depending on what the neutrons hit).

He-3 + He-3, with no D at all, does result in purely charged reactants.

Re:Fusion reactor

[gtg625a]

By what I am reading, when you fuse Deuterium and Tritium the only products are neutrons, alpha particles, and 17.6 MeV. The halflife of a free neutron is only 10.8 minutes and alpha radiation can be stopped with paper .... not that bad considering that halflife of most by products is thosands of years.

Re:Fusion Reactor

[Remik]

Tokamak bad...IFR good. [slashdot.org]

That's the problem

[TheBoquaz]

People are always talking about how much energy such and such reaction gives out for fusion.

They are missing the real problem. That is, how do you get the energy out? Most of that "free" energy is in the form of high energy neutrons, which hit the vessel wall. Protons are kept away from the vessel wall by the EM fields (for the most part-- it's the neutral Deuterium you have to worry about there).

Ideally, you have a substance which can absorb the neutrons and turn the energy into heat, which can be used to generate electricity, while at the same time, staying non-radioactive.

Keep in mind that the walls of most fusion reactors are kept at about 4K to sustain the superconducting magnets. There are some serious engineering issues left, even using "high temperature" superconductors.

Not so privately

[Catskul]

" Privately they are hoping that the US joins without interfering with the choice between Canada and Japan."

Privately published in a major news outlet.

we should be in this

[TheBoquaz]

Given that we spend over $500 billion on electricity every year here in the US [doe.gov], we could probably afford to spend a little more on technology that is finally coming of age. [gat.com]

Re:we should be in this

[solman]

I'm sorry to quibble, but the figure is actually between 200 and 300 billion dollars each year at least half of which is spent on DISTRIBUTING the energy, not generating it. $500 billion is the total amount spent on all end use energy sources (including gasoline for cars, etc.) and including distribution, which doesn't go away when fusion arrives. $100B would be a more appropriate number to use in the comparison.

What I wonder is why the project was originally budgeted at $10B if they could achieve nearly the same results for half as much money.

Re:we should be in this

[moonbender]

Gasoline isn't necessary once the general energy issue is solved. Fuel cells dont solve that, since the hydrogen they burn has to be created (which uses energy), but they're a viable, clean means of mobile energy transportation. Admitted, this won't be possible in the next ten years, but then again, neither will fusion power.