Health Physics: Nuclear Radiation
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Health Physics: Nuclear Radiation
Health Physics Nuclear Radiation
Health Physics: Section 5- Nuclear Radiation
how does radiation affect humans?
it can kill or damage living cells
what can nuclear radiation be used for?
sterilise medical instruments
by killing germs
kill cancerous cells
by placing an alpha source next to the tumour or by firing a beam of gamma rays at the tumour
radiation can be used for diagnosis, how?
is injected into the patient
the tracer is carefully chosen so that is will collect in the organ being studied and an image of the organ can be then be taken with a
what is an atom?
the smallest particle into which matter can be divided
its made up of a central
what are the three types of nuclear radiation?
what happens what radiation passes through a material?
some of its
energy is absorbed
by the material.
the amount of absorption depends on the type of radiation and the material it is passing through
in an atom, what does the nucleus consist of?
in an atom, what does the electrons do?
orbit the nucleus at high speed
they are negatively charged
what is alpha absorbed by? what is its range in air?
sheet of paper
what is beta absorbed by? what is its range in air?
a few metres
what is gamma absorbed by? what is its range in air?
not aborbed in air
what is ionisation?
adding or taking away an electron from an uncharged atom
what is photographic fogging?
its used in to detect radiation in a
in a film badge different section of a piece of photographic film are covered by various thicknesses and types of absorber
which radiation causes more ionisation?
what is ionisation used to detect radiation from?
the Geiger-Muller tube
what happens in the Geiger-Muller tube?
when radiation enters the tube through the thin mica window it causes ionisation in the gas
this allows the gas to conduct and a pulse of current passes between the electrodes
this pulse of current is counted by the counter
how can the type of radiation be determined?
by which sections of the film in a film badge are blackened
the amount of radiation can be determined by how black the film is
what is scintillation?
radiation can cause some materials to scintillate.
the material absorbs the energy of the radiation and re-emits it as light.
scintillation is used to detect radiation in what?
what is a collimator?
a large piece of lead with thousands of holes in it
ensures that although gamma rays are given off in all directions, only parallel rays reach the detector
what is a detector?
converts radiation into light by scintillation
what is the electronics?
turn the pattern of light into an electrical signal, which can then be transmitted to a monitor for viewing
what is the activity of a radioactive source?
the number of atoms that decay each second
what is the half-life of a radioactive source?
the time taken for its activity to half
what is the activity of a radioactive source measured in?
how can the half-life of a radioactive source be measured?
by taking measurements of the activity of the source at regular intervals of time using a Geiger-Muller tube and counter
what happens to the activity of a radioactive source?
decreases with time
what safety precautions need to be taken when handling radioactive materials?
always handle with forceps
point source away from body
store in lead container
label all sources
wash hands after use
what is the dose equivalent of a radioactive source?
a measure of the biological risk of the source
what is dose equivalent measured in?
what does the biological effect of radiation depend on?
the type of absorbing tissue
the type of radiation
the total energy absorbed