Biggest Obstacle of Nuclear Fusion Overcome?

Yetihehe writes "Nuclear fusion could become a more viable energy solution with the discovery of way to prevent super-hot gases from causing damage within reactors. The potential solution, tested at an experimental reactor in San Diego, US, could make the next generation of fusion reactors more efficient, saving hundreds of millions of euros a year."

Comments

Re:biggest obstacle will be environmentalist.

[iogan]

I think maybe you're confused between fusion and fission. Environmentalists generally don't mind fusion, as it is a safe, and very eco-friendly way of producing energy. Which is, you know, what they like.

Fission, on the other hand.. is problematic. It might be the only viable alternative at the moment (well actually I'm just saying that to not get flamed) but nobody can say it doesn't have its share of problems. Waste being the biggest, safety (yeah yeah I know, pebble reactors, yada yada ;-) ) being the second biggest.

crap!

[cdn-programmer]

The biggest obstacle on nuclear fusion is neutrons. Fusion produces a lot of neutrons and the idea of neutron free fusion using He3 is so far over the horizon that it isn't worth thinking about.

Fission also produces neutrons.

Since both reactions produce neutrons they have the same issues - namely dealing with radioactive wastes.

Fisson is easy to create. A team of boy scouts can do it in their own back yard. Fusion is very difficult.

Fission can be totally safe. It can also be very dangerous. It depends on the reactor design but the issue is that the technology is already on the shelf. IE. We can do it now and we have been able to do it for 50 years.

Now the issue is that with the USA designed high pressure reactors, they only use about 2/10 of 1% of the uranium that is mined. What this means is that with a better design we can get about 475 times the milage from our uranium.

There is so much energy available to us that it is almost beyond our imagination. Consider that there are about 114 reactors in the USA which have been running say about 50 years. 50x475 = 23,750 years. There has literally already been enough uranium mined for almost 24,000 years for a well designed reactor like the IRF (Integral fast reactor - look it up in the wikipedia). If we wish to produce 100% of our energy from uranium we have enough uranium mined already for over 2,000 years. Of course the best solution is to use this energy to free up hydrogen which we can combine with carbon to produce synthetic oil (syncrude!). We need about 75 GWe reactors right now here in Alberta. We have a terrible hydrogen shortage. The price of gasoline at the pumps is a symptom of this problem.

Yet - we keep reading stories about the holly grail - Nuclear Fusion.

Yes, some day will will build a fusion reactor. The research is a good idea. But the idea that it will be problem free is a false idea. The biggest obstacle is not wear and tear due to plasma - the biggest obstacle is neutrons flying around and these are difficult to control. In fact - the best solution might be to pack a bunch of thorium around the plasma and use the neutrons to transmute it into U233 which we can cart off to a fission reactor. As an alternative we can pack U238 around the plasma and cart of the Pu239. These are viable fuel cycles - unfortunately at present they are not politically correct.

Re:crap!

[Phanatic1a]

Fission also produces neutrons.

Fusion produces orders of magnitude more neutrons.

In a fission plant, excess neutrons are bad. You want the pile to be barely critical, a stable, but not runaway, chain reaction. So you actually don't have a lot of neutrons flying out of the pile. You moderate the ones you do produce, and use them to fission additional fuel atoms.

But in a D-T fusion scheme, the bulk of the liberated energy is produced in the form of a very energetic 14 megaelectron-volt neutron. And this neutron doesn't participate in additional reactions, DT fusion isn't a chain-reaction process like fission is. The neutron will leave the plasma. Heck, ideally, that's how you get energy out of the reactor, by trapping that neutron in a surrounding blanket, causing that blanket to heat up so you can use that heat to boil water. Every single D-T fusion generates one of these neutrons, so the neutron flux will be many many times that of a fission plant.

But that's not an issue because of "radioactive waste." The wastes we're concerned about from fission aren't neutrons, they're from fission fragments and decay daughters. Some of those might emit neutrons themselves, but really, that's not the primary concern; neutron-induced radioactivity is actually pretty short-lived.

The reasons neutrons are a concern in a fusion plant is that continuous high-energy neutron bombardment does very bad things to all known materials that you might want to build a reactor vessel out of. When a neutron strikes an atom, it displaces it within the crystal lattice. If that happens once, no big deal, but in a commercial fusion reactor, the reactor vessel will experience 300 to 500 displacements per atom over the lifetime of the device. That means that, right now, we don't even know what to build one of these things out of. Austinitic steels start to swell, crack, and degrade after only about 30dpa, and the very best candidate materials we know of can only handle about 150; those might be acceptable, if the cost of changing the inner wall out isn't too high, but we just don't know.

And ITER won't even begin to explore those issues. ITER's flux will only generate 3 displacements per atom.

Fusion is very very hard. My money says that we'll never use commercial fusion power.