During the early stages of nuclear energy utilization the stock of uranium has been estimated to be quite limited. Also, the major part of the uranium (99.3%) was then not usable as a fuel. In order to make use of this large part of potential fuel, the breeder reactor has been developed. By capturing neutrons, it converts uranium-238 into the fissile plutonium. Plutonium is “bred”.

kraftwerk gersteinwerk luftbild - rwe pressebilder
© rwe pressebilder

Breeder reactor

A moderator required in other reactor types is not necessary. The breeder reactor has the potential to enlarge the stock of fissile material by a factor of 100.

In contrast to all other reactor designs, the average conversion of one non-fissile atomic nucleus into more than one fissile atomic nucleus is achieved during the nuclear fission process. The respective rate amounts to 1.1 to 1.2. In a pressurized water reactor this rate typically reaches a value of 0.55.

When a breeder reactor is loaded, more fuel is being bred, than necessary for on-site demand. The additional fuel has to be extracted when recycling the fuel elements. Afterwards it can be processed into new fuel rods.

In order for the breeding process to occur, a coolant with a very high thermal conductivity is required. On the other side its neutron absorption capacity should be negligible.

Sodium, which occurs in liquid form in a temperature range of several 100°C, is a substance that satisfies these requirements. Sodium reacts explosively with water and therefore also burns in ambient air, due to its inherent humidity. Consequently, the operation of breeder reactors is quite dangerous and requires even higher security measures than regular nuclear power plants.