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Science P2 Topic 5

Edexcel GCSE additional science physics: nuclear fission and fusion

What are nucleons? sub-atomic particles within the nucleus i.e. neutrons and protons
What is the atomic number of an element? It is the number of protons in an atom of the element, and is equal to the number of electrons
What is the mass number of an element? The number of nucleons (neutrons + protons) in an atom of the element
How do you work out the number of neutrons in an element? Mass number - atomic number
What are isotopes? Atoms of a single element with different numbers of neutrons (making the mass number different) e.g. lithium-6 and lithium-7
What is ionising radiation? Radiation that has enough energy to make atoms lose electrons to become positively-charged ions
What is radioactive decay? The random process where an unstable nucleus in a radioactive material decays by releasing ionising radiation to become more stable
What are the features of the 3 types of ionising radiation? 1) alpha particles- very ionising, stopped by paper, emitted from nucleus, 2 protons + 2 neutrons 2) beta particles- electrons emitted from a nucleus, stopped by a few mm of aluminium 3) gamma rays- electromagnetic waves, stopped by lead/concrete
What are some dangers of ionising radiation? Can cause skin burns (reddened skin) and can mutate DNA inside cells causing cancer
What is nuclear fission? The process where a large, unstable nucleus splits into two smaller, daughter nuclei - neutrons are released as well as a lot of energy (thermal and kinetic)
What is the difference between a controlled and uncontrolled nuclear chain reaction? Uncontrolled: lots of neutrons are released from each fission reaction which cause even fission and will result in an explosion. Controlled: another material is present to absorb all neutrons bar 1, so only 1 is absorbed by another nucleus
How does a nuclear reactor keep a controlled nuclear reaction? Control rods are present- they contain elements that absorb extra neutrons, and they can be lowered into the core to decrease fission levels and raised out to increase the levels
What is the purpose of the following features of a nuclear reactor core: concrete shielding, fuel rods, moderator? Concrete shielding- prevents stray neutrons and radiation escaping. Fuel rods- contain pellets of radioactive fuel e.g. uranium, plutonium. Moderator- slows neutrons down so they are more likely to be absorbed
How is the thermal energy released by nuclear fission used to generate electricity? A coolant (water at high pressure) is pumped through the core and becomes superheated- it's pumped to a heat exchanger where it is used to produce steam, which drives a turbine and turns a generator that transfers kinetic energy into electrical energy
What are some advantages of using nuclear power to generate electricity? * there is currently a large supply of radioactive fuel * no greenhouse gases are released
What are some disadvantages of using nuclear power to generate electricity? * expensive to build and decomission * constant danger of radioactive materials escaping * waste has to be buried safely for a long time * energy to create fuel rods was probably produced in a way that released greenhouse gases
What is nuclear fusion? the process whereby two smaller nuclei fuse to become one larger one, and lots of energy is released
How do stars get their energy? Nuclear fusion
What conditions are needed for nuclear fusion? * high pressures to increase densities of the nuclei, allowing them to get closer to each other and collide more easily * they need to be at a very high temperature to allow them to travel fast and overcome electrostatic repulsion
Why is electrostatic repulsion a problem? • These conditions are hard to sustain on Earth so producing fusion power is very difficult
What is the peer-review process? where scientists repeat the experiments done by another scientist and they must get the same results to validate the evidence e.g. this failed for the theory of 'cold fusion'
Created by: 11043