Physics(sp) Question - Fusion Reactors

[Singular Quartet]

Do Fusion reactors produce radiation?

If they do, do they produce in amounts comparable to fission reactors?

[Enlightenment-alternate]

Do Fusion reactors produce radiation?

Yes.

If they do, do they produce in amounts comparable to fission reactors?

Depends on the type of fusion. This is pretty much the limit of my knowhow so you'll have to either hope for someone else to chip in or go research the products of the various fusion reactions.

[The Dark]

They produce radiation, but not (IIRC) radioactive waste. That's a big reason for research on them, because they produce more power and safer by-products. As said above, though, you'll need to find someone with more knowledge than me to get more information.

[Durandal]

Do Fusion reactors produce radiation?

Yes. The release of photons is EM radiation. Though fusion produces no dangerous radiactive waste.

If they do, do they produce in amounts comparable to fission reactors?

Not even close.

[ClaysGhost]

Fusion reactors do produce radiation when only hydrogen is fused to form helium-4. There is a reaction involving helium-3 and hydrogen that produces protons, not neutrons, and this is good because not only can you completely stop the protons using electric fields, you can also directly convert their kinetic energy to electrical energy via these same fields; rather nicer and more efficient than the neutron equivalent (water heating). However, helium-3 is rare, and proponents tend to start talking about mining the atmosphere of Jupiter for He-3 when this is mentioned (a sure sign that someone has gone raving mad, Peter F. Hamilton please take note).

There are probably other reactions that do not produce neutrons, but they will likely require higher ignition temperatures, which is difficult to arrange.

Fusion reactors also produce radioactive waste, because the reactor structure itself is continually illuminated by hard neutrons, eventually requiring that the afflicted sections of the reactor be replaced (and the old radioactive structure be disposed of). However, I would naively expect the quantity of waste involved would be far lower than for a fission reactor, since the waste is irradiated reactor sections, not irradiated fuel, and less of one is produced than t'other.

The key benefits of fusion reactors are their stable and (very, very) common fuel (unless He-3 is used), the physical impossibility of any kind of chain reaction (rather than just the engineering impossibility that is striven for in current fission reactors), and I expect the high power output. The lower radiation output is also another benefit, although most people should probably still be more worried about the radiation they receive from the Sun than from a nuclear fission power station.

[Darth Wong]

Fusion reactors make lots of neutron radiation, but nowhere near as much waste (and all of the waste they do make is short-lived waste, unlike the long-lived waste of a fission reactor).

[kojikun]

doent He[3] fusion reactors require Lithium shielding? cant that be used to produce more fusion fuel? I'll check my books to find what im thinking of..

[Darth Wong]

You're talking about a breeder blanket. Mondo materials-science research is underway on this subject.

[Crayz9000]

If I recall, when the fusion reactor nears the end of its lifespan, the only radioactive parts that must be disposed of are the internal components of the reactor.

[Pu-239]

Look here
US to rejoin ITER fusion project

[kojikun]

great now we can spend huge amounts of money on fusion that barely works and is effectively a dead end.

[Darth Wong]

great now we can spend huge amounts of money on fusion that barely works and is effectively a dead end.

If you've got a better idea, please feel free to provide it. Many of the "desktop fusion" ideas work, but they A) still don't get break-even and B) aren't scalable to the level we want.

[kojikun]

many of the desktop fusion ideas also get exactly 0 funding. which seems more promising: a billion dollar barely break even reactor the size of a house or a 50 dollar basketball sized reactor that achieves fusion with neon-sign transformer power?

somehow i suspect the basketball sized one is better given the low amounts of power required to start fusion. especially when the big ones need massive quantitied of power just to initiate fusion let alone break even.

[Darth Wong]

many of the desktop fusion ideas also get exactly 0 funding. which seems more promising: a billion dollar barely break even reactor the size of a house or a 50 dollar basketball sized reactor that achieves fusion with neon-sign transformer power?
somehow i suspect the basketball sized one is better given the low amounts of power required to start fusion. especially when the big ones need massive quantitied of power just to initiate fusion let alone break even.

Not when your objective is to create massive quantities of power. If you can use 500 watts to initiate fusion but you only get 100 watts out, what's the point? At least there are theoretical possibilities for getting break-even and decent scaling out of the big-iron concepts. It's also far easier to convert energy into electricity when there's lots of it, due to thermodynamic efficiencies.

[kojikun]

when you put 500MW in and get 501MW out, and youre using technology you've spent 50 years and 10 billion dollars working on, is it worth the money?

We've not even researched many of the table-top designs on the scales of Toks and IFs so its not even guaranteed that they'll FAIL! Thats not to say theyll ever break even either, but theyre damned worth working on, especially since they tend to cost practically nothing, can be made with readily abailable materials, and can achieve fusion using less energy then Toks.

[Darth Wong]

when you put 500MW in and get 501MW out, and youre using technology you've spent 50 years and 10 billion dollars working on, is it worth the money?

We've not even researched many of the table-top designs on the scales of Toks and IFs so its not even guaranteed that they'll FAIL! Thats not to say theyll ever break even either, but theyre damned worth working on, especially since they tend to cost practically nothing, can be made with readily abailable materials, and can achieve fusion using less energy then Toks.

Oh good, let's throw money toward anything which has no established track record and no theoretical roadmap toward break-even or commercial viability, based on the fact that it's not guaranteed they'll fail

[kojikun]

hardly, im not suggesting that we pump a billion into them, not at all. but fusion had to start somewhere, its not as if Toks existed then someone said "Hey! These make fusion!" they were designed on theory and even to this day completely fail to achieve their goal of usable fusion. And how much has been spent?

I'm not calling for Toks to be abandoned and table-tops to take over all fusion research, I just want to see one alongside the Toks and IFs and ZPinches. If I can build one (and have) then surely PRINCETON can.

[Shaka[Zulu]]

when you put 500MW in and get 501MW out, and youre using technology you've spent 50 years and 10 billion dollars working on, is it worth the money?

We've not even researched many of the table-top designs on the scales of Toks and IFs so its not even guaranteed that they'll FAIL! Thats not to say theyll ever break even either, but theyre damned worth working on, especially since they tend to cost practically nothing, can be made with readily abailable materials, and can achieve fusion using less energy then Toks.

Oh good, let's throw money toward anything which has no established track record and no theoretical roadmap toward break-even or commercial viability, based on the fact that it's not guaranteed they'll fail

actually Lord Wong, the Farnsworth Fusor does indeed have something of an established track record... particularly when Westinghouse (IIRC) was backing the work of Farnsworth, Hirsch & Meeks. They had quite a bit of success (that current Fusors are only now just beginning to replicate at the university level) before their collective plug was pulled and all the hardware & paperwork was torched. I find it so disgusting, that in order to find major corporate backing so many gifted scientists & engineers have to sign over all their IP rights, words actually fail me. Where O where are the Nikola Teslas, Wright Brothers & Einsteins of the Modern Age???

[Shaka[Zulu]]

hardly, im not suggesting that we pump a billion into them, not at all. but fusion had to start somewhere, its not as if Toks existed then someone said "Hey! These make fusion!" they were designed on theory and even to this day completely fail to achieve their goal of usable fusion. And how much has been spent?

I'm not calling for Toks to be abandoned and table-tops to take over all fusion research, I just want to see one alongside the Toks and IFs and ZPinches. If I can build one (and have) then surely PRINCETON can.

you built one??? WHEN??? got any pics????? I am totally green with envy!

as for the rest, I have to agree. Toks were among the second generation of plasma devices used in fusion research, and after a great deal of effort put forth by then soviet scientists was adopted as the toy of choice in the fusion race. There is in fact a great deal of animosity held by the tok crowd against anything that might threaten their research grants... Princeton would rather not even acknowledge the existence of tabletop devices much less actually pursue them! (think of the impact on the grants man!)

[Shaka[Zulu]]

come to think of it, even toks were at one time (large) tabletop devices!

Koji man... IIRC we live in the same neck of the woods... Im gonna have to see this thing for myself!!!

[Darth Wong]

actually Lord Wong, the Farnsworth Fusor does indeed have something of an established track record... particularly when Westinghouse (IIRC) was backing the work of Farnsworth, Hirsch & Meeks. They had quite a bit of success (that current Fusors are only now just beginning to replicate at the university level) before their collective plug was pulled and all the hardware & paperwork was torched. I find it so disgusting, that in order to find major corporate backing so many gifted scientists & engineers have to sign over all their IP rights, words actually fail me. Where O where are the Nikola Teslas, Wright Brothers & Einsteins of the Modern Age???

Being exaggerated, as usual. The Farnsworth fusor made fusion. So did a lot of other devices. But even in principle, it cannot achieve break-even. It's a favourite toy of people who want to demonstrate that fusion can be performed easily, so easily that there are online manuals on how to build one (for cheap, as a high school science project!). But what good is it, if the grid design inherently limits efficiency?

These stories of the grand conspiracy of silence, people trying to suppress this revolutionary technology, etc. are a lot of bullshit. If it was commercially viable, they would go for it. But it has inherent flaws which mean that it will NOT be commercially viable. Now, if they can find a way to eliminate the grid-loss problem, sure. Think of something, and I'm sure funding can be secured for experiments. But until then, there's no reason to expect funding for that or any other project which has not at least demonstrated some kind of roadmap to commercial viability.

[GrandMasterTerwynn]

Do Fusion reactors produce radiation?

If they do, do they produce in amounts comparable to fission reactors?

Yes. By definition, a hydrogen --> helium fusion reactor would produce copious quantities of alpha radiation (which is just helium nuclei.) Fortunately, alpha radiation has almost no penetration. It also produces high-energy photons.

Also, some fusion processes tend to generate a lot of spare neutrons. So, as a result, one would tend to get some induced radioactivity in the structures and components of the reactor.

[Shaka[Zulu]]

I never said it was a conspiracy of silence... the phenomenon is more akin to a business interest seeking to make sure that anything it decides not to do -- for whatever reason -- isnt capitalized on by competitors... especially if said business interest goes OUT of business. Investors really hate to see rivals succeed using ideas and techniques that they paid the $ for in the first place, so they seek to force the rivals to spend $ in duplicating the R&D. There isnt any shadowy reasoning going on beyond that.

[kojikun]

lord wong, you are quite right, the farnsworth design simply cannot work, but there are permutations thereupon which have yet to be tested which may proove beneficial. for instance, a combination of both magnetic and electrostatic confinement, where plasma is confined both by magnetic fields as well as fusion-achieving electrostatics may prove to provide more power out then in. there are also ways by which energy can be added to the fuel without increasing the power put into the device. specifically, instead of having the fuel oscillate once per cycle, push the fuel in continuously with multiple stages like a particle accelerator and let overpressure do the rest. in such a manner you would get more energy in the fuel with the same power.

*edit*

btw there are also farnsworth designs that use no grids. instead they focus large numbers of electrons in the center that act as "virtual grids". because of the small size of the electrons, when the protons move inwards theres effectively no grid related inefficiency. tho personally i dont like the spherical design for various reasons.