How does a breeder reactor work?

A breeder reactor generates more fissile material than it consumes while producing energy.

A breeder reactor is a type of nuclear reactor that has been designed to create more fissile material (fuel) than it consumes. This is achieved through a process known as breeding, where fertile material, such as uranium-238 or thorium-232, is converted into fissile material, like plutonium-239 or uranium-233, respectively. This process occurs during the normal operation of the reactor, as the fertile material is exposed to the high-energy neutrons produced during fission.

The core of a breeder reactor contains a mix of fissile and fertile materials. The fissile material, such as uranium-235 or plutonium-239, undergoes fission when struck by a neutron, releasing energy and more neutrons. Some of these neutrons are absorbed by the fertile material, converting it into additional fissile material. This newly created fissile material can then be used as fuel, allowing the reactor to produce more fuel than it consumes.

Breeder reactors are designed to maximise the number of neutrons that are absorbed by the fertile material. This is achieved by using a fast neutron spectrum, which means that the neutrons are not slowed down (or moderated) as much as in a typical thermal reactor. Fast neutrons are more likely to be absorbed by the fertile material, increasing the rate of breeding.

The use of breeder reactors could potentially greatly extend the world's supply of nuclear fuel. By converting fertile material into fissile material, breeder reactors can utilise a much larger proportion of the natural uranium or thorium resources. However, there are also significant challenges associated with breeder reactors. They are more complex and expensive to build and operate than typical thermal reactors, and the use of plutonium as a fuel raises proliferation concerns. Furthermore, the high-energy neutrons produced in a breeder reactor can cause significant damage to the reactor materials, leading to technical challenges in the design and operation of these reactors.