Reactor fuel is usually uranium 235 or plutonium 239. Neutrons are fired in to split the the atoms producing new elements and a large amount of energy as well as more neutrons which split more atoms. The rate of production of energy has to be controlled. The control rods contain boron which will absorb surplus neutrons, to slow the reaction down and reduce the amount of heat produced the rods are lowered further. If more energy is needed then the rods are raised.
A coolant, usually gas or water, is pumped through the reactor core to absorb the heat. Water in the heat exchanger removes the heat energy from the coolant. The water is very hot and under very high pressure and is used to drive a steam turbine, which drives a generator to produce electricity.
- Causes no atmospheric emissions
- A flexible and reliable source of energy
- Fuel can be recycled to some extent
- Low cost power production once a power station is set up
- The fuel is easy to transport
- There is a chance of high risk disaster due to accident, earthquake or tidal wave
- The waste produced is highly radioactive and will remain so for a long time
- Leaks can cause contamination of the environment
- The power station is expensive to build
- The lifetime of a nuclear power plant is limited and it is expensive to demolish at the end of its life.
Natural gas fired power stations are relatively cheap to build and the waste gases contain much less sulphur dioxide and carbon dioxide than coal.
The turbine generator typically has a two stage system like this:
- Air is pushed into the turbine burner
- Gas is injected into the burner creating high temperatures and pressures
- The expanding hot gas rushes out, driving the turbine blades which can then be used to drive a generator
- The hot gases are used to heat water, creating the steam to drive another turbine and another generator in exactly the same way as is done in coal power stations. The use of these two types of generator together makes gas power stations very efficient
- •When gas burns relatively little carbon dioxide is produced and few other pollutants.
- •It is very easy to transport
- •Gas power station are relatively quickly and cheaply constructed.
- •It is a concentrated source of energy (burning a small amount of gas produces a large amount of heat).
- •Gas power stations are relatively efficient.
- •There is a good supply at present
- •It is not a renewable source and the world will run out eventually
- •It is not easy to store
- •It does contribute to global warming.
- •A lot of the worlds gas comes from politically unstable countries.
- •The world price varies beyond our control.
Coal fired power stations
Some advantages of coal are that it -
- Burns easily.
- Is widely available.
- Has large reserves and fairly cheap.
- Is fairly easy to transport and store.
- Needs power stations which are not complex to build and they can be turned up and down easily, depending on demand.
Some disadvantages of coal are:
- It is Non-renewable and will run out.
- Coal mining is a dangerous occupation.
- Burning coal releases a large amount of carbon dioxide, a greenhouse gas, contributing to global warming.
- Burning produces sulphur dioxide which causes acid rain.
- Mining of coal damages the surrounding environment.
You can download a PDF copy of these notes which is easy to print here:Non renewable energy resources