When nuclear fission is encouraged to happen by bombarding the nucleus with neutrons
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what is nuclear fission?
when an unstable nuclei (more than 83 protons) randomly splits in to smaller more stable nuclei
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why is energy released during a fission event?
as two smaller nuclei which are produced have a larger binding energy per nucleon
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what is nuclear fusion?
when two small nuclei combine to make a bigger nucleus
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why is energy released during a fusion event?
as two smaller nuclei join together to form a bigger nucleus which has a larger binding energy provided that the two nuclei which fuse are light enough
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how does nuclear fusion occur?
when the two light nuclei collide at very high speed to overcome the electrostatic repulsion (as both are positively charged) and then interact by strong nuclear force
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how can the energy released be calculated?
E = dmc^2 where dm is the difference between the total mass before and after the event
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what is a nuclear chain reaction?
when the neutrons from the previous fission go on to cause other nuclei to fission and so on
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what are thermal neutrons?
neutrons which are slow enough to be absorbed by a nucleus
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what is the moderator in a nuclear reactor?
(water or graphite) to slow down/ absorb neutrons to keep the reaction going at a steady rate
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what is are control rods in a nuclear reactor?
(boron) to absorb neutrons to limit the amount of neutrons which go on to cause fissions, can be used as emergency stop if they are fully inserted in the reactor
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what is the coolant in a nuclear reactor?
(water) to remove the heat caused by fission, should be a liquid or gas at room temperature and efficient at heat transfer
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what is "critical mass"?
amount of fuel needed to allow the chain reaction to continue on its on at a steady rate.
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what is the reactor shielding?
thick concrete case which absorbs all of the radiation and prevents it from reaching the people working in the plant
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why are used fuel rods more dangerous than unused ones?
unused emit alpha radiation which is weakly penetrating and can be easily contained, used emit beta and gamma radiation which are strongly penetrating
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how is radioactive waste stored and disposed?
dipped in cooling ponds when removed as they are very hot, then stored underground in sealed containers until its activity has fallen sufficiently
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Other cards in this set
Card 2
Front
what is nuclear fission?
Back
when an unstable nuclei (more than 83 protons) randomly splits in to smaller more stable nuclei
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