Nuclear fission 1
Nuclear fission is the splitting up of a big atomic nuclei.
Nuclear power stations generate electricity usin nuclear reactors.
In a nuclear reactor, a controlled chain reaction takes place in which an atomic nuclei splits up and releases energy in the from of heat.
The heat is used to heat water to make steam, which is used to drive a steam turbine connected to an electricity generator.
The fuel that's split up is usually uranum - 235 though sometimes it can be plutonium - 239.
The chain reactions 2
For nuclear fission to happen, a slow moving neutron must be absorbed into a uranium or plutonium nucleus. The addition of one of these nucleus makes it unstable causing it to split.
Each time a uranium or plutonium nucleus splits up, it spits out two or three neutrons.
One of the neutrons which have been spat out, might hit another nucleus, causing it to split again.
When a large atom splits in two, it will form two smaller nuclei. These new nuclei are radioactive because they have the wrong number of neutrons in them.
Nuclear fission 3
A nucleus splitting (called a fission) gives out a,ot of energy.
The main problem with nuclear power is that it causes alot of waste. The products left over from nuclear fission are highly radioactive so they can't just be thrown away. They are difficult and expensive to dispose of safetly.
Shutting down a nuclear plant safetly takes decades.
Nuclear fusion 4
Nuclear fusion is the joining of small atomic nuclei.
Two light nuclei like hydrogen, can join to create a large nucleus. This is called nuclear fusion.
Fusion releases a lot of energy (even more than nuclear fission).
Fusion doesn't leave behind a lot of radioactive waste and there's plently of hydrgoen around to use as fuel.
Fusion can only happen at high temperatures - about 10,000,000 degreese celsius.
You need an extremely stong magnetic field for fusion as you can't hold the hydrogen at high temperatures.