radioactive materials Flashcards
what are nuclear wastes categorised in according to their level of risk?
- low level waste:
slightly radioactive waste that is sealed + placed in landfills - intermediate level waste:
a lot is produced, deciding how to store = prob, most are mixed with concrete + stored in big containers - high level waste:
very radioactive waste, stored carefully. only small produced + doesn’t remain radioactive for long
what are the 3 types of ionising radiation?
alpha
- absorbed by a few cm of air or thin sheet of paper
beta
- passes through air and paper but absorbed by few cm of aluminium
gamma
- very penetrating + needs many cm of lead to absorb most of it
what is irradiation?
exposed to radiation
what is contaminated?
radioactive material on skin, clothes or entered body
rr
r
what are the uses of radiation?
- high energy gamma rays destroy cancer cells
- sterilise surgical instruments + sterilise food killing bacteria
- as a tracer in body eg PET scans
r
r
r
r
what are the dangers of radiation?
break molecules into ions which damage cells becoming cancerous or killed
a - dangerous inside, radiation absorbed by cells
b - dangerous outside, penetrate outer layer of skin, damages internal
g - if absorbed by cells but weakly ionising so can pass through body without damaging
what is sievert?
measure of a radiations dose’s potential to harm a person
based on type + amount of radiation absorbed
what is nuclear fusion?
if hydrogen nuclei brought close together, can fuse into helium nuclei which releases energy
fusion releases large amounts of energy + is the source of the suns power
what does a nucleus contain?
positive protons and neutral neutrons held together by strong nuclear force which balances repulsive electrostatic force between protons
explain nuclear energy?
energy released during nuclear fission greater than that released in a chem reaction involving a similar mass of material
what is the equation for nuclear fusion/fission?
for mass of matter, M, the amount of energy, E, produced during nuclear fission given by:
E = mc2
what is the alpha particle scattering experiment?
gold foil bombarded with alpha particles, effect on alpha particles recorded + observations provided evidence for our current understanding of atoms
what 3 observations were recorded?
most alpha particles were seen to pass straight through gold foil:
- indicates gold atoms composed of large amounts of space
some particles were deflected + few bounced back towards source
- alpha particles passed close to some positively charged within atom and were repelled by it
what were the conclusions of the experiment?
- nucleus positively charged
- electrons are arranged around the nucleus with great deal of space between them
- atoms consist of empty space with a nucleus
what do nuclear power stations don’t do?
- don’t emit smoke from chimneys as happens in fossil fuel power stations
- don’t release greenhouse gases
spent fuel rods from reactors in power stations do what?
- contain 90% uranium
- high level waste
- sent away to be reprocessed + used to make new rods
how do you calculate half life?
used to calculate how old a radioactive substance is or how long it will take to become safe
when is a substance considered to be safe?
once activity drops to same level as background radiation
some substances decay quick and could be safe in short time
those with long half life remain harmful for years
how do you measure half life?
as radioactive atom decays, activity drops + radioactivity decreases
half life is time it takes for its radioactivity to 1/2
why do experiments that measure half life need to be repeated?
need to be repeated + the activity level for each experiment averaged to give more reliable data bc there might be slight variations each time activity is measured
what are elements?
made of atoms, each contains 1 type of atom + all atoms contain nucleus and electrons
why is hydrogen different?
has no neutrons, just 1 proton + electron
what are isotopes?
atoms of same element that have diff numbers of neutrons
what are examples of when evert atom of a particular element has same number of protons?
hydrogen atoms - 1 proton
helium atoms - 2 protons
oxygen atoms - 8 protons
when is ionising radiation emitted?
when nucleus of unstable atom decays, type of radioactive decay depends on why the nucleus is unstable
the process of decay helps atoms become more stable
how alpha decay?
d
how does beta decay?
d
how does gamma decay?
d
