26/05/2016 Nuclear Fission and Fusion L/O :- To know the process of nuclear fission and fusion

26/05/2016 Nuclear fission an fusion LO: To know the process of fission and fusion Starter: 1)If a radioactive sample of rock started with 100 counts per second and 2 hours later has a count rate of 25 counts per second, what is it’s half-life? Try these questions, have a go at the answer 1)What do you think is meant by a ‘chain reaction?’ 2)The gold that exists on our planet, where did it come from? Was it made here or somewhere else? 3)How is a nuclear bomb similar to a nuclear reactor

26/05/2016 Nuclear reactors: Remember that Nuclear power stations make electricity in a similar way to fossil fuel power stations. Order these parts: Generator, fossil fuel burner, turbine, steam boiler.

26/05/2016 The main difference is the burner. Instead of a fuel being burnt, a nuclear reaction generates heat. This heat is then used to boil water which turns a turbine which turns a generator to create electricity.

26/05/2016 The main fuels used in nuclear reactors are: Uranium And Plutonium - 239

26/05/2016 Nuclear fission – the process An atom of uranium or plutonium receives a neutron. The neutron causes it to be unstable and undergo nuclear fission. The large atom will split into 2 smaller atoms, gamma rays, kinetic energy and free neutrons. What do you think the free neutrons might do? (think back to your starter!) The free neutrons will join with other uranium or plutonium atoms to start a chain reaction

26/05/2016 Nuclear fission Uranium or plutonium nucleus Unstable nucleus New nuclei (e.g. barium and krypton) More neutrons Neutron

26/05/2016 Chain reactions Each fission reaction releases neutrons that are used in further reactions.

Controlling a chain reaction 26/05/2016 To control a chain reaction, the spare neutrons created after each atomic fission need to be absorbed. This can be done using control rods. These are suspended above the nuclear reactor. The more they are dipped into the reactor the slower the reaction occurs. (the rods are held by magnets in case of emergency – why is this?)

Nuclear bombs 26/05/2016 How is a nuclear bomb like a nuclear reactor? They both use the same fuel, they both use the same process of having a uranium or plutonium atom absorb a neutron which starts a chain reaction. So why doesn’t a reactor act like a bomb?

Fission summary 26/05/2016 Fission uses uranium or plutonium They first absorb a neutron. It is the splitting of a larger nuclei into 2 smaller nuclei, energy and neutrons The neutrons can go on and start a chain reaction

Nuclear Fusion 26/05/2016 If fission is when large unstable atoms split up and release energy, Fusion is when atoms ‘fuse’ to become larger ones. It happens in stars. (We haven’t worked out how to do it on earth YET!) (nuclear fusion may well be the long term answer to our planets fuel needs)

That gold treasure! 26/05/2016

That gold treasure! 26/05/2016 All the different elements found on earth were once made in stars billions of years ago. Long before our own sun was formed stars lived and died in this part of the galaxy. When a star explodes it can send its contents scattering across millions of miles. Our solar system is formed from the ‘debris’ or ‘left overs’ of these stars.

So the gold? 26/05/2016 So the gold that we treasure is made in the heart of long dead stars. Along with nearly every other element that we have on earth.

26/05/2016 Deep within the sun, Hydrogen atoms can fuse together to form helium. This releases huge amounts of energy. (that’s why our sun is so hot) As the hydrogen runs out the helium nuclei will start to join releasing still more energy. Eventually, large atoms all the way up to iron will be formed, when the star may die and explode scattering its contents.

26/05/2016 Nuclear Fusion in stars ProtonNeutron In a star Hydrogen atoms fuse together to create Helium atoms. This is nuclear fusion The heat of a supernova can cause larger atoms to fuse together into heavier elements.

Fusion Summary Nuclear fusion is the joining of two atomic nuclei to form a larger one. It is the main way that energy is released in stars. 26/05/2016