Tritium and fusion power

For the discussion of the sciences. Physics problems, chemistry equations, biology weirdness, it all goes here.

Moderators: gmalivuk, Moderators General, Prelates

User avatar
idobox
Posts: 1591
Joined: Wed Apr 02, 2008 8:54 pm UTC
Location: Marseille, France

Tritium and fusion power

Postby idobox » Mon Jul 16, 2012 10:41 am UTC

I just realized one thing. Everyone is looking up at ITER and fusion power to one day bring clean power to everyone, but as much as I know, everybody is working on D-T fusion, and tritium is produced in fission reactors. So when we manage to get it working, where do we plan to get our tritium from? Even if we coat the reactors with Li6, it will produce less tritium than it consumes.

If we need fission reactors to produce tritium, fusion can never be the most part of our energy mix, and we should seriously invest in better fission technology.
Unless D-T is only a step on the way to D-D or p-B

Edit
After a bit of googling, which I should have done first, I've learned that it is possible to actually create more than 1 tritium atom per released neutron.
http://fire.pppl.gov/jason_tritium_fusion_2011.pdf

Li7 can absorb a neutron, release an alpha, a triton, and another less energetic neutron
Be and Pb release two neutrons, at the cost of energy.

I have also learned that 1GW.year of thermal power requires 56kg of tritium, which is much more than I expected. The very large quantities of tritium involved also mean a lot of He3 will be produced too.
If there is no answer, there is no question. If there is no solution, there is no problem.

Waffles to space = 100% pure WIN.

gorcee
Posts: 1501
Joined: Sun Jul 13, 2008 3:14 am UTC

Re: Tritium and fusion power

Postby gorcee » Mon Jul 16, 2012 2:46 pm UTC

Yeah, basically that. One of the concepts for tritium breeding in fusion reactors that has been floating around is encapsulating the reactor in a vessel containing liquid lithium, which will serve as the heat exchanger and for tritium production. Unsure if that's still a leading idea. (Only glanced through that report).

User avatar
idobox
Posts: 1591
Joined: Wed Apr 02, 2008 8:54 pm UTC
Location: Marseille, France

Re: Tritium and fusion power

Postby idobox » Mon Jul 16, 2012 4:13 pm UTC

Liquid lithium is still the favorite, apparently, but they also talk of a Pb-Li alloy.
Apparently, Lithium high conductivity is going to be an issue with the large magnetic fields implied in magnetic confinement, and adding lead should alleviate that. I don't really see the point, but adding a neutron multiplier in the mix can probably help increase the breeding efficiency.
If there is no answer, there is no question. If there is no solution, there is no problem.

Waffles to space = 100% pure WIN.

User avatar
Minerva
Posts: 947
Joined: Sat Nov 11, 2006 2:58 pm UTC
Location: Australia
Contact:

Re: Tritium and fusion power

Postby Minerva » Mon Aug 06, 2012 2:24 pm UTC

Any practical D-T fusion power reactor must be a self-sustaining tritium breeder with a Li blanket, so its fuels are essentially lithium and deuterium.

The natural abundance of 7Li is a lot larger than 6Li, but the 7Li cross section is a lot smaller than 6Li. But 7Li gives you back the extra neutron.

All these factors work together against each other. Obviously we do need to break even on tritium formation vs. tritium consumed, but there should be enough tritium formation there to do it. But with a Li blanket completely surrounding the fusion reactor essentially all the neutrons should be captured in the Li anyway, it should be designed so that they do not get absorbed or escape anywhere else to the fullest extent practical.
...suffer from the computer disease that anybody who works with computers now knows about. It's a very serious disease and it interferes completely with the work. The trouble with computers is you play with them. They are so wonderful. - Richard Feynman


Return to “Science”

Who is online

Users browsing this forum: No registered users and 12 guests