June 29, 2005

Greenpeace on Fusion.

Tim Worstall has picked up Greenpeace's oppersition to Fusion. But if you want the source here is the original press release, containing this jem:
Fusion energy - if it would ever operate - would create a serious waste problem, would emit large amounts of radioactive material and could be used to produce materials for nuclear weapons. A whole new set of nuclear risks would thus be created.
So many errors in such a short space.

"if it would ever operate":
It does opperate, now. JET has been producing reliable fusion for years. Fusors for decades and on the kind of bugets that mean you can build one yourself in your garage. The problem is getting more energy out than you put in. JET could just about hit break even, and Iter is set to go beyond that.

"would create a serious waste problem"
The ash is Helium, a gas that is chemically inert, non-toxic, and non-radioactive. This is the gas used by deep sea divers for years as a replacement for nitrogen to avoid the bends.

The actual reaction produces high energy neutrons, which can alter the isotpes of the materials used to make the structure and turn it radioactive. But being locked into the structure reach the outside, and tend to have short haft-lives. Calculations show that after you switch the reactor off for about 20 any radioactive isotopes within the stucture will have decayed back to the original non-radioactive isotopes.

Most of the neutrons are absorbed in a lithium blanket turning the lithium to helium and tritium, which is radioactive. But the tritium is feed back into the reactor as it is one of the fuels, it never gets into the enviroment. So there is some radioactive material produced, but it is never released and most of it isn't "waste" it's fuel.

"could be used to produce materials for nuclear weapons"
How? For atomic fission weapons you need heavy isotopes, Uranium or Plutonium. Fussion reactors generate helium. Any isotope changes in the structure are never going to produce elements this heavy.

To generate weapons grade Plutonium you do need high energy neutrons, which could be found from fusion reactors. This is why the military funded fussion research in the 1950's. Until they found fussion reactors are simply not very good at this role, so they stopped funding. Nobody is every going to use a fusion reactor for generating weapons grade Plutonium for the simple reason that they arn't good at it, and there are other methods that are.

Now for fussion weapons you need exactly the same fuel as for fussion reactors. So by burning it you are destorying "materials for nuclear weapons" not producing them.

It appears that when the BBC quoted them they got rid of the more stupid stuff and left just the more plausible reasons for not liking Iter. However in the light of that press release their real objection seems to be "nuclear bad, change scary".


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