There are many different kinds of nuclear reactor design in use around the world. In general, nuclear countries have chosen certain designs and stuck with them, while others may use another kind entirely.
For example in America, typical reactors are the pressurised water reactor (PWR) and boiling water reactor (BWR) designs. In the UK though, we use gas cooled reactors (Magnox) and advanced gas reactors (AGR). They operate on similar principles, but are designed differently to achieve the same result.
Main components of nuclear power plants
Fuel
Most commonly uranium oxide (UO2), but other fuel cycles can be used such as thorium and plutonium oxide (PuO2) in fast neutron reactors (FBR). The fuel is what undergoes nuclear fission to release energy and neutrons to cause fission in other fuel atoms, continuing the process.
Moderator
The neutrons which are emitted are more effective when they are travelling more slowly - more fissions result. The moderator (which varies between reactor designs) slows the neutrons down. Moderators tend to be either water, heavy water or graphite.
Control Rods
Control rods are made from materials which absorb neutrons. They can be inserted to control the rate of reaction. If the control rods are inserted, the number of neutrons reduces so the rate of fission reduces as well.
Coolant
The reactor core gets hot, but this in itself is not useful energy. The energy is transferred to the coolant which is pumped through the reactor. The coolant is then used to boil water in a steam generator.
Containment Vessel
The reactor is housed within a strong containment vessel to prevent major accidents if something goes wrong. The containment vessel protects against radiation, but also prevents access to the reactor and nuclear fuels to prevent tampering.
Turbine
The whole point of the exercise is to generate electricity. The turbine is driven by the steam formed from the heat from the reactor.
So to sum up the process of energy transfer, this is how nuclear power plants work:
Nuclear fission produces heat which is transferred by a coolant to produce steam which is used to drive a turbine.
The image below shows a rough design for a typical pressurised water reactor. Other designs (and the source of the image below) are available from the World Nuclear Association (pdf)
Return to nuclear fission from how nuclear power plants work