Breedin' (its not what you think)

Andrew · Senior Member

Breedin' (its not what you think)

GoogleNaut · Guru

If you mean using some source of neutrons (like a fusion reactor) to breed fissile isotopes to be used as nuclear reactor fuel, then yes this is quite possible. It has been suggested to use a thorium fuel cycle in which Th-232, (which is more abundant than uranium,) absorbs a neutron becoming Th-233 which decays by emitting an electron to become U-233 which is a fissile isotope. Conventionally, U-238 is hit with neutrons that cause it to become U-239 which decays quickly to Neptunium-239 by beta decay, and then decays over several days again to become Pu-239 which can be extracted from spent fuel to make either nuclear weapons, or nuclear fuel.

I think there are some other interesting breeding chains possible but as far as I know only the Thorium cycle and the Uranium cycle have been extensively explored, while the uranium breeder cycle is the only one to have been tried...

A coupled uranium and thorium breeder cycle with deep-burn reactors should provide our civilization with energy reserves for several thousand years. I think we would be a foolish race not to exploit this important energy source.

10kBq Jaro · Senior Member

GoogleNaut wrote:
as far as I know only the Thorium cycle and the Uranium cycle have been extensively explored, while the uranium breeder cycle is the only one to have been tried...

Actually, the MSRE (Molten Salt Reactor Experiment) was used at Oak Ridge to try breeding of U233 from Th232.
There is a discussion forum on this & related subjects at http://www.energyfromthorium.com/forum/index.php

You are invited to participate !

Andrew · Senior Member

What are the main technical, economical and political hurdles about breeding fuels, especially Th-232-> U-233 ?

10kBq Jaro · Senior Member

Andrew wrote:

What are the main technical, economical and political hurdles about breeding fuels, especially Th-232-> U-233 ?

The main economical hurdle is that uranium is cheap, while breeding cycles using either U238/Pu239 or Th232/U233 generally aren't -- the two main reasons being that they typically require enriched uranium or reprocessed plutonium to get started, and reprocessing of solid (oxide) fuels is expensive.

On the positive side, the fuel processing hurdle can be overcome with non-oxide fuels -- either liquid fluoride salt fuels (in Molten Salt Reactors, MSRs, as discussed in the above-mentioned forum), or uranium metal alloy fuel, as used in the IFR (Integral Fast Reactor).

If the current relatively high prices of uranium from mines can be sustained for a number of years, and if the cost (monetary & political) of permanent storage of un-reprocessed spent nuclear fuel becomes too high, then the incentives for diversifying the current nuclear reactor fleet into plants capable of recycling will naturally increase -- hopefully some will eventually be built, whether in the US or elsewhere.....

GoogleNaut · Guru

Interestingly enough there was a recent Scientific American article on reprocessing nuclear fuels. As I recall (I wish I knew which month it was--I think the last 6 months or so...) the author looked at solid metal fuel blends burned in a liquid metal (bistmuth/lead) cooled, fast spectrum reactor. The interesting thing about this technology is that reprocessing can be done on site--spent fuel rods are run through a metal-salt bath and then electrolyzed to 'refine' the materials in the rod. Fission products are deposited on the bottom of the tank as 'sludge' and 'clean' fuel is deposited on the opposite electrode. Eventually the 'refined' material is extracted from the salt bath, cleaned of salt residues, and then melted in an induction furnace to form a new fuel rod. The fission product sudge at the bottom of the salt tank are then processed into glass pucks and then shipped off to storage in a waste reprository. But since the 'waste' is mostly fission products, the storage time can be safely reduced to just a few centuries or so--almost all the actinides are recycled back into the fuel load...

The idea behind this method of fuel reprocessing is interesting, especially in light of the idea that almost all fissile materials will be consumed in a 'deep burn,' which hopefully will reduce the nuclear weapons proliferation crowd.

Also having the ability to reprocess fuels onsite reduces the need to transport spent fuels back and forth--and using direct metal alloys makes it possible to come up with different blends--so even former nuclear weapons materials may be 'downblended' or 'demilled' and used as a useful, energy producing 'fuel.' Although the article looked at uranium mostly, I think that something very similar can also be used with thorium. If that can be done, then humanity will have plentiful fissile fuels for atleast 500 years and maybe closer to 1000 years...