Nuclear Fusion Power

Someone told me that the fuel that will be used in the new commercial nuclear fusion power stations will not run out, unlike the Uranium currently used in the fission ones which will run out in 1000 years.

I would have thought the new fusion ones would also use Uranium but don't know that.

Is he right or wrong (about the fuel lasting forever) ?

PS : Hope I've got the fusion and fission things the right way around.



EDIT - Made the question clearer



[edit on 19/6/04 by Hyperen]

Well, nuclear fusion is heat generated by the fusion of Hydrogen into Helium. (Actually, I think they use "heavy hydrogen", also called Deuterium, and Tritium) In that case, no, since Hydrogen is the most plentiful element in the universe, we'll effectively never run out. The problem is effeciently producing hydrogen and it's fusable counterparts.

Fission, on the other hand, relies on mined material, uranium (238, I believe) which we will run out of, since it's mined.

Ouizel was pretty much on with the basics. There's many types of fusion, but the most promising to start use deuterium (D, proton+neutron), and tritium (T, proton+2 neutrons). Couple of the reactions:

D + D -> T + p
D + D -> He3 + n
D + T -> He4 + n
D + He3 -> He4 + p

Notice that the first D + D reaction (known as DDp) releases a tritiuim, which can then react with another deuterium nucleus to produce a helium-4 nucleus (alpha particle). This is important since the alpha particle is the most promising for harnessing the energy.

Anyways, deuterium is obtained from heavy water (D2O), which can be manufactured from light water (H2O). Also, there is a considerable quantity of deuterium in the ocean, which would, for essential purposes, be limitless. There is thought to be a large amount of He3 on the moon, so there have been proposals to use that for interplanetary missions.

I should note that inertial confinement fusion, which uses particle beams or lasers to compress a small deuterium pellet, might use a little bit of uranium as an ablative layer. This means that it acts as a pusher - as the laser heats it, it vaporizes, resulting in a compressive reactive force.

Regarding fission, we will run out of uranium sooner than that if the US gov't doesn't allow us to reprocess fuel. We waste a lot of potential fuel with this once-through cycle, and we also generate a lot of excess waste. Additionally, if the breeder reactor program is restarted, we'd essentially never run out of fuel, as breeder reactors can us thorium, which is much more abundant than uranium.

Hope I didn't get too technical - let me know if anything is unclear.

Yes, 1000 years isn't the expected run-time for Fission plants as they currently stand, it is actually a little less than 40.

Originally posted by PurdueNuc
Hope I didn't get too technical - let me know if anything is unclear.

Not at all. It's nice to have someone that really knows their stuff.

Originally posted by ViendinYes, 1000 years isn't the expected run-time for Fission plants as they currently stand, it is actually a little less than 40.

Where did you come across 40 years? That seems very low to me

[edit on 20/6/04 by Hyperen]

I remember seeing on a progam on Discovery once a while back, that was pretty much painting a dire picture of Fission power in general, and I remember they said we have about 200-250 years left of Uranium.

Originally posted by sardion2000
I remember seeing on a progam on Discovery once a while back, that was pretty much painting a dire picture of Fission power in general, and I remember they said we have about 200-250 years left of Uranium.

All of these calculations are based on "financially recoverable uraranium" -which in turn is based on the realative costs of other fuels. As oil/coal rise in price, the amount of uranium that is financially benefiial to mine increases, increasing the time that we can operate.

If it were the only fuel left, and we had to mine every last bit of uranium - 1000 years or more is reasonable, with the current price of oil 250 years sounds about right.

But that is why the numbers will change all the time. Reactors are also contiuosly made more or less efficient by safety standards. Also, if you eliminate the option of re-processing spent fuel (which still contains a lot U-235 and U-233, both fissile), the running time will drop dramatically. The US, of course, does not reprocess - but many other countries do.

Fusion... I believe that can use H 1-1 for that as an initial basis, just means that you get less energy out, as you need to fuse two h 1-1 into an H 2-1 which releases some funky particles... But admitedly, H 2-1 is used because you get more energy out and it's also straight available from the sea.

edit: Only problem with this is that you are continuously producing Helium.... And technically there will be a date when we run out of hydrogen for fusion... But then we can switch into lithium or something, we can use any element down to Iron? or lead, cant remember which is the most stable.

[edit on 20-6-2004 by browha]