Is fusion Practical? And is it safe?

[gjonesy]

I just read an interesting article on a fusion reactor that was fired up and actually produced hydrogen plasma just like in our own sun. How practical is this technology? And is it safer than fission reactors? What's the waste products if any this will produce? I know its very early faze, but it has some interesting implications for the future.

http://www.techtimes.com/articles/1...grees-celsius-to-generate-hydrogen-plasma.htm

 

[rootone]

Experimental fusion reactors have been made for quite a long time and they work.
However the problem is that they require a lot of energy input to produce a useful amount of output.
So far there has been no reactor that would be a viable commercial power source, but work is in progress and slowly going in the right direction.
Here is a link to a huge international project which might interest you.
https://www.iter.org/

Safety and waste is of course a concern, but the hazards are less than those associated with conventional fission power plants.

 

[mgkii]

One of the major safety features of fusion, is that we have to "artificially" create the containment system that allows sufficient pressure/temperature for fusion to start. Once you lose those conditions, fusions stops - there's no concept of a run-away reaction that you might get with fiscile materials. The products of Hydrogen fusion are mostly Helium and I assume traces of slightly heavier elements; but again nothing as nasty as the products of fission.

 

[gjonesy]

One of the major safety features of fusion, is that we have to "artificially" create the containment system that allows sufficient pressure/temperature for fusion to start. Once you lose those conditions, fusions stops - there's no concept of a run-away reaction that you might get with fiscile materials. The products of Hydrogen fusion are mostly Helium and I assume traces of slightly heavier elements; but again nothing as nasty as the products of fission.

That actually sound much safer than fission, if there is no solid waste to deal with and its just producing gases, But the heat containment sounds like a very difficult issue to deal with if a reactor were to run continuously for a long period of time.

 

[phyzguy]

That actually sound much safer than fission, if there is no solid waste to deal with and its just producing gases, But the heat containment sounds like a very difficult issue to deal with if a reactor were to run continuously for a long period of time.

It's not quite so rosy as all that. The entire solid structure of the reactor gets very radioactive through neutron activation, and needs to be replaced periodically due to neutron damage. So solid radioactive waste will be produced. If the reactor is designed properly this waste is not as long-lived as that from a fission reactor, but it is significant. Also, why do you assume radioactive solids are worse than gases? Solids can be sequestered where people don't contact them, while gases will likely be dispersed in the atmosphere where everyone will breathe them. Tritium gas can be nasty in this respect.

 

[mfb]

Tritium is part of the fuel and has to be created from the reactor, so they will make sure they capture nearly all of this valueable gas. Nothing has 100% efficiency, however, so there will be tiny amounts of tritium escape, and a small but relevant risk of a larger release if it mixes with oxygen and (chemically) explodes.

I just read an interesting article on a fusion reactor that was fired up and actually produced hydrogen plasma just like in our own sun.

Wendelstein 7-X produced a hydrogen plasma, but no relevant fusion. Atoms in the sun need on average 10 billion years to fuse (that's why the sun is still a star after 5 billion years) - creating the same reaction rate in the lab means fusion rate is completely negligible. We need different fuels, deuterium plus tritium (both heavier versions of hydrogen) instead of the "normal" hydrogen. Wendelstein 7-X won't operate with tritium, to avoid the activation issue a commercial fusion reactor would have. The fusion reaction itself is well-understood, research focuses on the plasma and its stability, and you don't need fusion to study that.

 

[gjonesy]

Also, why do you assume radioactive solids are worse than gases?

I would assume that radio active gases would be captured and compressed and or contained till it could be properly disposed of, radio active solids from my understanding have to be placed in expensive custom build containers and buried deep underground. That takes up space time and money. With gases I would think there are easier and better ways of dealing with it.

 

[mfb]

Making something "solid-tight" is way easier than making it gas-tight. Every container that can store gas can easily store solid material, but not the other way round.

 

[rootone]

would it possible though to chemically combine radioactive gases with other elements to produce a more containable solid?
I know if they are isotopes of 'noble' gases this could be difficult, but I would think there should be some way of doing it.

 

[mfb]

Yes, sure, that would probably be done if radioactive waste gases are produced (something you really want to avoid).
It is even done with materials that are solid on their own, to create chemically more stable compounds.

 

[nikkkom]

I know if they are isotopes of 'noble' gases this could be difficult, but I would think there should be some way of doing it.

I think currently existing nuclear fuel reprocessing plants do intentionally emit radioactive gas, specifically Kr-85, to atmosphere. Its half-life of 10 years makes it impractical to completely "wait it out" before reprocessing, it does not form stable solid compounds, thus storing it is a problem. However, radioactive noble gases do not bioaccumulate, so venting it is not as bad as it might seem.

Thankfully, fusion doesn't produce any radioactive noble gases.