Breeder reactors

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Breeder reactors are nuclear fission reactors that make better use of nuclear fuels. This could solve the problem of uranium scarcity, and also reduce nuclear waste.

Breeder reactors are not currently ready for deployment.


Uranium occurs in nature as a mix of isotopes: uranium-235 (0.7%) and uranium-238 (99.3%). This proportion does not vary much within the Earth's crust.

  • Today's nuclear reactors (not breeder reactors) can only get their energy from uranium-235 (U235). Technically the nuclear reactions are a bit more complex than that, but still limited by the scarcity of U235.
  • Breeder reactors can get energy from the more abundant uranium-238 (U238).

Breeder reactors can also make use of thorium-232, which is similarly abundant.

This is a more complex process than simple nuclear reactors, because thorium and U238 are not fissile materials, only fertile materials. They have to be "bred" to become fissile materials such as U233, U235, or plutonium-239.

Breeder reactors still need some fissile material to function, but they produce more of it than what they started with. A breeder reactor's doubling-time is a useful way to measure this: how long it takes for the reactor to produce twice as much fissile material as it started with. Breeder reactors so far have a doubling-time of over 100 years, unfortunately. Example quoted from
Thorium hasn't been used in large scale reactors, however some reactors have used it successfully in the past. A light water breeder reactor in Shippingport, Pa. USA operated for 5 years, and by the end of its operation it had 1.4% more fissile fuel than it began with.

This cites another source:
World Nuclear Association. (June 19 2015). Thorium [Online], Available:
Scientists are trying to get this down to 10 years. Even in such a case, it would still take decades to breed enough fuel to meet global energy demands.

Thus we can't count on breeder reactors to solve climate change soon enough. We still have to work on other energy sources too, such as wind and solar.


Some reactor types that might show potential:

External links