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P4 page 198-199 (contamination and irradiation can cause different amounts…
P4 page 198-199
contamination and irradiation can cause different amounts of harm, based on the radiation type
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high levels of irradiation from all sources are dangerous, but especially from ones that emit beta and gamma
inside the body, alpha sources are the most dangerous, because they do all their in a very localised area. so contamination, rather than irradiation, is the major concern when working with alpha sources
beta sources are less damaging inside the body, as radiation is absorbed over a wider area, and some passes out of the body altogether.
gamma sources are the least dangerous inside the body as they mostly pass straight out (they have the lowest ionising power)
the more we understand how different types of radiation affect our bodies, the better we can protect ourselves when using them. this is why it is important that research about this is published . the data is peer-reviewed and can quickly become accepted, leading to many improvements in our use of radioactive sources
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each time a radioactive nucleus decays to become a stable nucleus, the activity as a whole will decrease (older sources emit less radiation)
for some isotopes it takes just a few hours before nearly all unstable nuclei have decayed, whilst others last for millions of years.
the problem with trying to measure this is that the activity never reaches zero, which is why we have to use the idea of half life to measure how quickly the activity drops off
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half life can also be described as the time taken for the activity (and also count rate) to fall to half of its initial value
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this radiation can be measured with a Geiger-muller tube and counter, which records the count-rate (the number of radiation counts reaching it per second
radioactive decay is a totally random. so you cant predict exactly which nucleus in a sample will decay next, or when any of them will decay
you can find out the time it takes for the amount of radiation emitted by a source to halve, this is known as the half life it can be used to make predictions about radioactive sources, even though their decays are random
half-life can be used to find the rate at which a source decays (its activity). activity is measured in becquerels, Bq (where 1 decay is 1 decay per second)
irradiation
objects near a radioactive source are irradiated by it. this simply means that they are exposed to it
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keeping sources in lead-lined boxes and standing behind barriers when using sources are common ways of reducing the effects of irradiation
in some industries the source may be in a different room and remote-controlled arms are used to handle it
contamination
if unwanted radioactive atoms get onto or into an object, the object is said to be contaminated e.g. if you touch a radioactive source without wearing gloves, your hands would be contaminated
these contaminating atoms might then decay, releasing radiation which could cause harm
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ionising radiation can enter living cells and ionise atoms within them. this can cause damage to cells (and cause things like cancer) or kill them off completely. that's why its important that you know the precautions to take when working with any sources of radiation