Uranium Shortage and D-T-Fusion Illusion

[Henning]

Just read that link on Slashdot:

The Nuclear Energy Option facts and fantasies (PDF)

From page 17 on he writes about the illusions of D-T-Fusion.

Mainly there is no tritium. In 2030 he estimates of 30kg tritium worldwide, being optimistic he writes. A 1GW reactor consumes 200kg tritium per year. With no way of producing tritium (e.g. uranium depleted), and Li+n reaction being a bad contender (see PDF).

[Tulse]

That article seems excessively bleak. There are plenty of alternative technologies, such as thorium reactors, that would avoid the issue of reduced uranium availability. Also, there is no consideration of aneutronic fusion, or even anything other than ITER. I’ll grant that these various alternative technologies will not be ready short-term, but I think it is highly likely that one or more of these options will pan out in the next decade or so.

[Henning]

That’s why I titled it “D-T-Fusion Illusion”. There is no such thing as tritium in consumable amount.

Aneutronic fusion is still a dream. We’re working on it, but the chance of success is maybe 0.00001%, 1%, 50% depending on whom you ask. So take the realistic/optimistic middle value of 1% (I’m personally much more optimistic, but that doesn’t count).

This article rules out neutronic fusion in a industrial fashion, at least its easiest way to do it (D-T-Fusion). This leaves you with D-D-Fusion. Back to specs.

I haven’t looked into thorium fission (you’ve talked about it here somewhere), but this leaves you with similar problems as uranium fission. I don’t wanna discuss it here, it’s probably ten times better. Good. Accepted.

The problem with thorium fission is, it doesn’t feed any electricity into the grid yet. You’re free to point out an experimental reactor (or actual productive reactor) to prove me wrong. But that’s not the point of this discussion.

The main points are:

* Not enough uranium for newly constructed reactors – so stop construction of new uranium fission reactors

* D-T-Fusion will never be feasible – so stop ITER or switch to D-D-Fusion

* He3 (the isotope) farming on the moon is pretty much bullshit because the transportation costs outweight the benefits by several orders of magnitude

I took the opportunity to add the last point. Just to squash any high flying dreams.

[belbear]

Henning wrote:
Mainly there is no tritium. In 2030 he estimates of 30kg tritium worldwide, being optimistic he writes. A 1GW reactor consumes 200kg tritium per year. With no way of producing tritium (e.g. uranium depleted), and Li+n reaction being a bad contender (see PDF).

You mean something like:

D+T fusion produces 1 neutron and energy,
Li+n consumes 1 neutron and energy, produces 1 Tritium
So you need to catch ALL of them neutrons to “breed” just enough tritium to keep the Tok going, which means no neutrons left to boil the water?…

So you really gonna need to keep them bad ol’ fission reactors running to make tritium?
And then to think that Sellafield & co must have released tons of it in the past…

[Henning]

Li+n -> T (plus anything else) is just the process described in the paper to produce tritium easily. Sellafield may have produced heaps of tritium, but the half life of tritium is just 12 years. That means in fifty years the tokomaks are going to be productive, none of the tritium is left.

That’s the point, you need fission reactors to feed D-T-fusion reactors. And uranium is exhausted in maybe 30 years, but you can’t store the tritium.

And thorium? Well a nice idea, I don’t know much about it. Maybe ten times better than uranium and ten times more abundant (whatever, I don’t really care at the moment). This makes it as much of a problem as uranium before: same amount of waste. But there’s no way of storing that waste safely (exception: the Swedes have a tectonic safe granite vault, but they won’t let anybody else dump their rubbish there).

So same problem with thorium as with uranium: heaps of uncontrollable waste.

[HermannH]

Henning wrote: And thorium? Well a nice idea, I don’t know much about it. Maybe ten times better than uranium and ten times more abundant (whatever, I don’t really care at the moment). This makes it as much of a problem as uranium before: same amount of waste. But there’s no way of storing that waste safely (exception: the Swedes have a tectonic safe granite vault, but they won’t let anybody else dump their rubbish there).

So same problem with thorium as with uranium: heaps of uncontrollable waste.

Actually, the amount of waste produced by a Thorium reactor is going to be very small compared to the waste from a conventional Uranium reactor. And it is relatively short lived (half time of around 500 years if I remember correctly, compared to 20,000 years for plutonium). Given that many geological formations have lasted for millions of years it should be possible to find one that is ‘almost’ guaranteed to last some 10,000 years.

In general, breeder reactors (Thorium and Uranium as well) not only use their fuel much more efficiently, they also produce less waste.

Of course uranium breeders produce loads of Pu239, which is an excellent weapons material. Thorium breeders produce U233, which is also weapons capable. This is probably one of the reasons why breeder technology hasn’t been pursued much in recent decades.

There are also some other technical challenges associated with molten salt reactors as outlined in this Wikipedia article.

If Focus Fusion (or some other fusion technology) shouldn’t pan out Thorium reactors have a good chance of being our main energy source 40 to 50 years from now. That or solar.

[Author]

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