What is a Nuclear Breeder Reactor?

Uranium 235 is a practical nuclear fuel. This means that slow neutrons will cause the uranium 235 atom to fission and produce more slow neutrons, and these slow neutrons will cause further fission of other uranium atoms and continue the fission process. For the same reason, uranium 233 and plutonium 239 are also practical nuclear fuels.

Breeder reactor

Uranium 235 is a practical nuclear fuel. This means that slow neutrons will cause the uranium 235 atom to fission (one into two) and produce more slow neutrons, and these slow neutrons will further cause the fission of other uranium atoms to continue the fission process. For the same reason, uranium 233 and plutonium 239 are also practical nuclear fuels.

Unfortunately, the amount of naturally occurring uranium 233 and plutonium 239 is really small, and the amount of uranium 235, although considerable, is also quite rare. In any specimen of natural uranium, only seven of every 1,000 uranium atoms are uranium 235 and the rest are uranium 238.

Uranium 238 is the most common type of uranium, but it is not a practical nuclear fuel. Uranium 238 can also undergo fission under the action of neutrons, but only fast neutrons can do this. Those uranium 238 split into two halves produce some slow neutrons, which are not enough to cause further fission. Uranium 238 can be compared to damp wood: you can burn it, but it will eventually go out.

However, assuming that uranium 235 is separated from uranium 238 (this is a rather difficult task), and uranium 235 is used to build a nuclear reactor, at this time, those uranium 235 atoms that constitute the reactor fuel will be fissioned and will Numerous slow neutrons were emitted in all directions. If the reactor encloses a shell made of ordinary uranium (most of which is uranium 238), neutrons injected into the shell will be absorbed by uranium 238. These neutrons are unlikely to force uranium 238 to fission, but they will cause another change in uranium 238, which will eventually produce plutonium 239. If these plutonium 239 are separated from uranium (a fairly easy task), they can be used as practical nuclear fuel.

A reactor that can produce new fuel in this way to replace the used fuel is a breeder reactor. A properly designed breeder reactor produces more plutonium 239 than uranium 235 is consumed. In this way, all the uranium on the planet-not just the rare uranium 235-can be turned into a potential fuel source.

Naturally occurring tritium is composed entirely of tritium 232. Plutonium 232, like uranium 238, is not a practical nuclear fuel because fast neutrons are required to cause it to fission.

However, if plutonium 232 is placed in the envelope of a nuclear reactor, the plutonium 232 atom will absorb slow neutrons, and although it does not fission, it will eventually become uranium 233 atom. As uranium 233 is a practical fuel that can be easily separated from plutonium, the result is another breeder reactor, which will turn the existing plutonium resources on Earth into a potential nuclear fuel.

The total amount of uranium and plutonium on Earth is about 800 times more than that of uranium 235. That said, if a breeder reactor is used properly, the potential energy on Earth can be increased by 800 times through nuclear fission power plants.