Ionising radiation Flashcards
Natural sources of radiation
cosmic radiation, animals, rocks, buildings, soil, plants
Artificial sources of radiation
X-ray machines, nuclear power, nuclear missiles, nuclear weapons testing
physical characteristics of ionising radiation
penetrating, invisible to the eye, reduces in intensity, can cause biological effects
half-value layer
thickness of a substance which will transmit one 1/2 of the intensity of the radiation incident upon it
the thicker the material is, the less photons will be passed through
half-life
time taken for half the atoms to decay
inverse square law
total amount of radiation in the beam doesn’t change, but the concentration decreases with increasing distance from the source
3 factors of radiation safety
time, distance and shielding
time
radiation dose can be reduced by limiting exposure time
distance
amount of radiation exposure depends on the distance from the source of the radiation
shielding
shielding, such as lead aprons should be used if the radiation source is too intensive
lead equivalent
the thickness of lead would absorb the same amount of radiation as the given material
radon gas
radioactive, colourless, tasteless gas which is formed by small amounts of uranium
banana dose equivalent
informal way of comparing doses of ionising radiation to the dose received by eating a single banana of average size.
useful concept to help explain relative radiation risk to the public
alpha decay
process which an unstable atomic nucleus loses energy by emitting radiation.
consists of two protons and two neutrons tightly bound together (most ionising and destructive form of ionising radiation)
beta decay
unstable atomic nucleus loses energy by emitting radiation
spontaneous emission of a fast moving particle with the mass of an electron from a nucleus
negative and positive beta particles are produced by the decay
gamma decay
unstable atomic nucleus loses energy by emitting radiation.
the spontaneous emission of a high energy photon from a nucleus
alpha radiation
helium 4 nucleus, stopped easily by a sheet of paper
beta radiation
high energy electrons or positrons, stopped by an aluminium plate
gamma radiation
high energy photon emitted by the nucleus, eventually absorbed as it penetrates a dense material such as lead
two types of radiation induced tissue damage
direct and indirect
direct action tissue damage
ionisation of macromolecules, such as DNA, RNA, proteins and enzymes
indirect action tissue damage
free radicals produced by ionisation of water
process of indirect action
- radiation - h2o loses an electron making it positive
- positive ion immediately breaks up
- electron attaches to Neuton water molecules
- resulting in negatively charge molecule dissociate
- H and OH are free radicals, which are unstable and can combine together or with oxygen to give H2O2 (hydrogen peroxide) or HO2 (hydroperoxyl radical)
direct tissue damage leads to
inhibit tumor suppression genes, which then could further produce radiation-induced cancer
