How does nuclear radiation cause ionisation?
- unstable nucleus decays and gives off one or more kinds of nuclear radiations
- radioactive materials give out nuclear radiation over time
- three types: alpha, beta, gamma
- radiation causes atoms to lose or gain electrons, turning them into ions
What are the properties of alpha particles?
- relatively big, heavy and slow moving
- 2 protons and neutrons
- because of size they are stopped quickly (do not penetrate far into materials)
- alpha particles stopped by paper and skin
- strongly ionising (knock electrons off lots of atoms before slowing down)
What are the properties of beta particles?
- just electrons
- small, move quite fast
- beta particles penetrate moderately before colliding
- so moderately ionising
- stopped by a few millimeters aluminium
What are the properties of gamma radiation?
- after spitting out alpha and beta particles the nucleus may need to get rid of extra energy
- does this by emitting gamma ray
- very high frequency EM radiation
- no mass or charge
- highly penetrating , weakly ionising
- stopped by thick concrete or a few cm of led
What are some uses of alpha radiation?
- smoke detector
- smoke detector have weak source of alpha radiation close to two electrodes
- radiation ionises air and current flows between electrons
- if there is a fire, smoke absorbs the radiation
- current stops and alarm sounds
What are some uses of beta radiation?
- medical tracers
- controlling the thickness of paper
How do tracers work?
-radioactive source swallowed by patient or injected into
-it can be followed round the body using an external radiation detector
computer converts readings to a TV display showing where the strongest reading is coming from
-should only be radioactive for a few hours
How is the thickness of paper controlled?
- direct radiation at paper and put a detector on the other side connected to a control unit
- if paper too thin, radiation detected will be to more, so control unit opens the rollers
- if paper too thick, less radiation detected, control unit pinches rollers up to make thinner
- use radioactive substance that doesn’t decay to quickly or the strength will gradually fall
What are some uses of gamma radiation?
- high doses of gamma kill all living cells
- used to treat cancer: directed carefully at the cancer at just the right dosage to kill cancer without damaging other cells
- sterilise medical instruments:kill all microbes without damaging equipment, strongly radioactive source needed that lasts long, so no need to replace often
- non-destructive testing
How does non-destructive testing work?
- to check turbine blades for cracks
- direct gamma rays at blades
- if too much radiation gets through the blade to detector on other side, you know the blade is cracked or there is a fault in the welding
How do nuclear power stations work?
- same way as most , but the boiler is different
- nuclear fission produces the heat to make steam
- water used a coolant to take away heat produced by fission process
- heat is used to produce steam to drive turbine and generator
What are some advantages of nuclear power?
- no CO2 produced
- nuclear reactions produce lots more energy than chemical reactions
- nuclear fuel is relatively cheap
- plenty of uranium left in ground
What are some disadvantages of nuclear power?
- power station are expensive to build and maintain
- takes long to start up nuclear power station than fossil fuel power stations
- processing uranium before use causes pollution
- risk of leaks of radioactive material, or major catastrophe (Chernobyl disaster)
- radioactive material can cause cancer and radiation sickness
- radioactive waste is difficult and dangerous to dispose or reprocess
- old, inefficient power stations have to be decommissioned (shut down and made safe) expensive
- uranium is non-renewable, although there is plenty left
How is nuclear fuel used to make nuclear weapons?
- used uranium from power stations can be reprocessed to make more uranium and some plutonium
- plutonium can be used to make nuclear bombs
How can you protect yourself when using radioactive material?
- store safely in a labelled led box
- keep exposure time short
- use tongs, never allow skin contact
- keep at arms length, as far away from body as possible
- pointing away from you
- don’t look directly at it
How do industrial workers protect themselves against nuclear radiation?
- wearing full protective suits to prevent tiny radioactive particles being inhaled or lodged onto skin or under finger nails, e.g.
- lead-lined suits and lead/concrete barriers and thick led screen, shield workers from gamma rays in highly radioactive areas
- use remote-controlled robot arms to carry out tasks in highly radioactive areas
How is radioactive waste disposed?
- low-level waste is buried in a secure landfill site
- high-level waste is sealed in glass blocks, then into metal canisters, then they could be sealed deep underground
What is high-level waste?
- really dangerous
- stays highly radioactive for years
Why is it difficult to bury of high level waste?
- difficult to find suitable places to bury
- site has to be geologically stable (e.g.not prone to earthquakes), big movements in rock can disturb canisters and allow radioactive material to leak out
- people who live nearby object
What else can you do to radioactive waste?
- reprocess to reclaim useful radioactive material
- but still leaves some waste
Why do you use beta radiation when controlling thickness?
- beta will be partly blocked by paper and cardboard
- if it went straight through (gamma) then reading wouldn’t change at all as thickness changes
Why is beta and alpha radiation used as tracers?
-this radiation passes out of the body
What is nuclear fission?
- atoms in nuclear fuel (uranium) splitting in two
- releasing lots of energy
What is low level waste?
-things like paper, clothing, glows, syringes, etc
