I almost feel like an intruder to commment on these issues, as I am just still constructing my demo fusor, but it seems that waste, while certainly an issue, is not the main one.
Concerning Fusion, when using Deuterium or even Tritium as fuel all the reactants tend to funnel toward stable gases. I don't see actual fuel "exhaust" as being much of a threat. Now the vessel walls would be receiving the brunt of the high energy neutrons, inevitably becoming active itself. I would certainly hope to God direct conversion devices would be developed long long long before we build any type of reactot powerful enough to be lethal. There's just no sense in moving beyond the small table top model until we've perfected the technique, exhausted the experimental capacity of small work, and have to move on.
With (more) direct energy conversion from neutron to electricity, some type of medium would probably line the interior of the reactor. All of the neutron radiation is absorbed and what doesn't get turned to electricty at the end of the line may end up activiting the medium to a degree. Careful engineering here could minimize the risks I feel.
As for direct conversion, I think this is very important. This is not something that should stay on the drawing board and wait to be brought out as soon as we get break even efficiency. I could see a huge list of applications for such a technology in the way of accurate neutron counting. Having an efficient moderator catch 100% of the neutrons that come out of that poissor would really beat the heck out of trying to observe a small fraction of em.
To comment on some of the calculations earlier in this thread: It's very important to know where we stand when it comes to fusion power. 1mol of Deuterons should have a mass of about 2.01 grams. Using two nuclei for reactions, and discouting the production of Tritium, 4.02 grams could produce 6.022e23 reactions. With a 2.45MeV neutron from each reaction, one "mole of reactions" should yield 2.36e11 Joules via fast netrons. Assuming a 20,000 n/sec emmission rate (which is low, but where most amateurs would probably operate around), it would take 2.7e19 seconds (866664879265 years) to fuse 4.02 grams of D2. Even to produce one measly Joule at this rate it would take 19 months! Ok, so even us amateurs are capable of hiking the reaction rate up to several orders higher than the 20,000 n/sec figure. But still the problem is, we're not really producing anything! A reasonable estimate of efficiency for a "typical" amateur machine is about .000000008%=energy out/energy in. In short, there is still plenty of work to be done increase fusion rate per unit input power. There are a couple of ideas out there, but few amateurs seem to be actively chasing them. That's what I would like to see more discussion on: how can these machines be made more efficient? In a way we are very lucky to be the ones who "get to do the fun stuff" when it comes to the fusor. The experimental field is wide open here, and higher efficiencies must be the main issue if we ever want to bring the fusor from desktop novelty to helpful boon.
Hopefully my calculations are not filled with glaring errors, if they are, any comments, corrections, cusses are welcome.
In any event, i'd like to hear more about ideas on how the fusor can be specifically improved to be more efficient.
Adam Parker
Created on Wednesday, May 02, 2001 11:38 PM EDT by Adam L. Parker