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11Phys Nuclear energy
Transcript of 11Phys Nuclear energy
Gather the energy produced from fission reactions and turn it into electricity.
Three problems exist when using U-235 fission as an energy source:
Need slow neutrons
Has to be controlled
Need to harness the energy
Now to slow down the neutrons
A moderator is used to slow the emitted neutrons, without absorbing them
Choices of moderator material:
U-235 is used as the fissile material
Requires 2.3% U-235 and 97.7% U-238
Molded into a a fuel rod
First the fuel source
Another type of reactor, called a fast breeder, doesn't use a moderator to slow the neutrons down.
This reactor takes U-238, which turns into Pt-239 when it abosrbs a neutron.
Pt-239 is a fissile material but needs fast neutrons, hence no moderator.
Is where fission occurs - gets hot!
Heat from fission
Steam turns a turbine
Which powers a generator -
The steam cools and condenses
And repeats the cycle
Contains the uranium 235 which undergoes fission when hit by a slow moving neutron
A chemical called a moderator is used to slow the fast neutrons produced during fission. Examples include water, heavy water and graphite.
Absorbs neutrons which will limit how many fission reactions are occurring (which controls energy produced)
Can raise or lower the control rods
Fission reaction of U-235 releases on average 2.8 neutrons. Each of these neutrons can cause another fission reaction, which will lead to a chain reaction.
Control rods are made from boron, cadmium or silver.