Nuclear decay and nuclear energy – WJECControlling the reaction
Nuclear fission is the splitting of a radioactive nucleus to release energy. High-energy collisions between light nuclei can result in fusion, which releases energy.
So that nuclear reactions like those seen in nuclear bombs do not happen in power stations, the nuclear reaction must be controlled.
Control rods
The moderator and control rod Neutron-absorbing rods inside a nuclear reactor. together control the rate of reaction in the core of the nuclear reactor.
Most nuclear reactors use water as a moderator, which can also act as a coolant, although some do use graphite rods.
Absorbtion rods
The control rods are neutron-absorbing rods, which are inserted into the spaces between the fuel rods, and are made from materials such as boron.
The control rods can be moved down into the reactor, which slows the reaction down by absorbing more of the neutrons, or moved up so that fewer of the neutrons are absorbed, which means that the reaction remains constant and explosions do not occur.
The nuclear fuel rods in a reactor can be radioactive for a very long time and have to be stored very carefully.