Radiation Flashcards
What happens when a neutral atom (or molecule) is hit by ionising radiation
It loses an electron and becomes a positively charged ion
When does a nucleus become unstable
When it possesses either too many or too few neutrons compared to the number of protons
If a nucleus has too many protons, what radiation will be emitted
Alpha radiation
If the nucleus has too many neutrons, what radiation will be emitted
Beta radiation
What is radiation
The spontaneous and random emission of energy from the nucleus
Which types of ionising radiation are deflected by electric and magnetic fields
(And why?)
Alpha and beta
They’re electrically charged
If a nucleus has excess energy, what is emitted
Gamma ray
3 things that effect amount of deflection (Rutherford)
- the speed of the alpha particle (deflected less if going fast)
- the nuclear charge
- how close the alpha particle gets to the nucleus
Nuclear fission
When a nucleus splits into two nuclei of equal size, and two or three neutrons
What does the moderator do
Slows neutrons so that they can successfully collide with uranium nuclei and sustain the chain reaction
What do the control rods do
Limit the rate of fission by absorbing excess neutrons
Half life
The half-life of a radioactive sample is the average time taken for half the original mass of the sample to decay
How are all living things radioactive (long version)
-cosmic rays from space make some of the carbon dioxide in the atmosphere radioactive. The carbon dioxide is used by plants (plants also absorb radioactive materials from the soil) and is passed along food chains
Why does background radiation vary from place to place
Some parts of the earth’s crust have higher amounts of radioactive material
Dangers of higher doses of radiation
Higher doses tend to kill cells completely, causing radiation sickness if a large part of the body is affected at the same time
Danger of lower doses of radiation
Lower doses tend to cause minor damage without actually killing the cell. This can cause mutations in cells which then divide uncontrollably - this is cancer
Why is so much more energy released from 1g of nuclear fuel than burning 1g of fossil fuel
Atom releases more energy when it splits than when it forms a chemical bond
Fission releases more neutrons which cause a chain reaction
The right half life of the isotope used to destroy cancer cells
Must be long enough to destroy cancer cells but short enough to minimise damage to surrounding tissues
Properties of a radioactive source used to sterilise plastic syringes sealed in plastic bags
Gamma or beta so it can penetrate the plastic and kill bacteria
Long half life so doesn’t need frequent replacement
2 definitions for half life
1) the time taken for a radioactive material to lose half its radioactivity
2) the time it takes for the count rate from a sample to fall to half its starting level
Radioisotopes
Atoms with unstable nuclei which emit radiation
Disposal of used protective clothing
Sealed into containers
Buried in secure landfill sites
Disposal of material from reactors
Mixed with concrete
Stored in stainless steel containers
Disposal of used fuel rods
Kept underwater in cooling tanks (it decays so fast it gets hot)
Eventually becomes intermediate level waste
Gamma rays are used for medical tracers which help doctors identify diseased organs. Why wouldn’t an alpha source work - and why would it also be harmful?
- useless cos it would be stopped by the body’s tissues, so couldn’t detect it externally
- worse than useless cos its strong ionising power makes alpha radiation really harmful if it gets inside you
Industrial uses of gamma radiation
To find leaks in underground pipes
To measure the rate of dispersal of sewage
