According to this site, "Helium can be formed by a set of reactions that cannot occur in the Sun's interior because it doesn't have any free neutrons" (rxn 3):

 

Thus, could you enrich your cooling water, with tritium, to absorb all the excess neutrons, fusing into Helium, and converting wasted neutrons, into usable heat energy ??

That sounds fine in theory, but the 'free neutrons' would have to have some kind of speed in order to properly instigate the reactions. I'm not talking speed of light speeds, but fast enough to escape the heavy water entrapment around the outer edges and destabilise further materials, unless you could construct the activated volume in a linear fashion with the neutron gun pointing down the middle of a cylinder of heavy water or something.

 

As it is, the current proposed fusion systems already use neutrons in their process - one of the technological obstacles to overcome at the ITER is the shielding used for the interior of the torus. It has to cope with high energy neutrons, and this equates to the interior surface becoming 'radioactive' (although its not quite the same, as with Radioactivity you are dealing with the weak nuclear force, not an abundance of high energy neutrons).

 

Edit: I just realised that I had mused on something similar to your suggestion a while back when considering what could replace the materials on the inner skin of the ITER. What if some form of liquid could be used to moderate the spare neutrons from the reaction on the entire inner surface of the torus?

 

There are some amazingly obvious problems with that. You have shielding hanging upside down, for one. Water can't do that...

 

Even putting the liquid behind a glass or some other material is still going to heat up the glass tremendously from the actual fusion process, let alone the neutron bombardment. I think this is why they are still attempting to develop materials to withstand the reaction properly

Edited August 3, 201114 yr by PerpetuallyConfused

Enrich cooling water with tritium:

 

Tritium reacts with deuterons. Tritium-neutron reaction isn't considered.

The other drawback is that everyone lacks tritium, which is very slow to produce.

You'll get richer by adding deuterium in cooling water and filtering out tritium than consuming the scarce tritium.

 

ITER:

 

A liquid wall is feasible provide the liquid flows quickly within a curved wall. It has been proposed but has some drawbacks.

Anyway, neutron irradiation produces radioisotopes which are truly radioactive and this is a huge worry.

Tokamak designers "hope" (computational models) to have materials whose radioactivity will decrease within a century, but that's all.

Worse: tritium regeneration must be done at the tokamak, it needs a neutron multiplier which is lead, and lead irradiation by fast neutrons would be as dirty as uranium fission at identical power:

http://saposjoint.ne...php?f=66&t=2450

and I have only checked very few reactions.

 

A liquid inner face won't have the structural difficulties but it must be reprocessed to separate unwanted nuclides. One should also check its vapour pressure, and contamination of the plasma.