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Flashcards in Nuclear Fission And Fusion Deck (14):

What is nuclear fission

Unstable heavy nucleus split into two lighter nuclei releasing vast amounts of energy and neutrons


Advantages of nuclear fission

Large amounts of energy per KG of fuel compare to fossil fuels

No CO2 released


Disadvantages of nuclear fission

Long-lived radio active waste

High decommissioning costs

Danger off nuclear accident (chain reaction out of control)


Explain how nuclear fission happens

Heavy nucleus being struck by a slow neutron. The heavy nucleus splits and fragments move apart at very high speeds carrying a vast amount of energy. At the same time two/three fast neutrons are also emitted. These neutrons go on to initiate further fission and so create a chain reaction.


What is fission used for

Generate electricity


What happens in a nuclear reactor

✨Uranium 235 or Plutonium 239 are used as fuels in the nuclear reactor

✨unstable atoms with heavy nuclei are bombarded with slow moving neutrons

✨this causes the nuclei of the atom to split into two less massive nuclei

✨realises large amounts of energy - called nuclear fission

✨several neutrons released

✨these neutrons can be reabsorbed by other nuclei causing further fission and creating a chain reaction


What is nuclear fusion

Is the combining of two light nuclei into a heavier nucleus. Once again there is a slight loss of mass and a release of energy.


Advantages of nuclear fusion

✨4x more energy per kg than fission

✨no long lived radioactive waste

✨no danger of uncontrollable chain reaction

✨readily available raw material (sea water)


Disadvantages of nuclear fusion

✨not commercial available

✨high temps and pressure required to make the reaction happen


Explain how nuclear fusion works

At the centre of the sun, the temperature is very hot. At this temperature the nuclei of the atom in a gas are stripped of their orbiting electrons and they move at a very high speed. The charged gas nuclei forms a state of matter called a plasma. Being positively charged the nuclei would normally repel each other but if they are moving fast enough they can fuse to form a new nucleus.


How is nuclear fusion produced

The stars eg sun

The nuclei move with such Kinetic speed they overcome to electrostatic repulsive force between them


Why do we not use nuclear fusion reactors

Expensive to build and the system to used to contain the plasma will be equally as expensive because of the very high temperatures needed for the nuclei to fuse.


Arguments in favour of nuclear energy

✨produces vast amounts of energy and electricity

✨produces very little CO2

✨provides employment for the unemployed

✨high density source of energy. 1kg of uranium produces as much energy as 20,000kg of coal

✨it is always available


Argument against nuclear energy

✨disposing of nuclear waste can be dangerous and expensive

✨many people are concerned about living close to nuclear power plant and storage facility’s used for radioactive waste

✨past accidents have made people scared of nuclear power inc the disaster at Chernobyl in the Ukraine and the earthquake and tsunami in japan in 2011 when several reactors were damaged leading to a meltdown and release of radiation