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The word radiation covers a lot of ground
but in the nuclear context we’re talking about ‘ionising radiation’, which
basically means streams of invisible waves or particles with sufficient energy
to knock electrons out of atoms, creating ions, resulting in chemical changes
to materials at the molecular level.
There are three different types
of naturally occurring radiation, designated Alpha, Beta and Gamma.
Alpha
particles are the biggest and composed of two protons and two neutrons but they
are also the weakest and cannot penetrate more than a few centimetres of air
and even have trouble getting through a few sheets of paper. However, that
actually makes Alpha radiation quite dangerous -- at close quarters and in very high doses -- because the particles are so big they are more likely to interact with and cause chemical and
biological changes to whatver they happen to smash into
Beta particles are essentially loose
electrons or positrons, they have more
energy and penetrating power than Alpha particles and can punch through a few
millimetres of wood or metal. Like all radiation, if there’s enough of it, it will
change or damage whatever it comes into contact with.
Gamma particles (or waves) are
essentially high-energy photons -- the same stuff as light and the gamma
radiation family also includes X-Rays. Gamma radiation has no charge but it
packs a lot of energy. However, because the particles are so small they can
pass right through matter without hitting anything, but once again if there’s enough
of it then it can and will cause chemical and biological changes
Ionising radiation sounds like a bad thing but the fact
is we are being constantly bombarded with natural radiation, from the food we eat (Brazil nuts are notoriously radioactive), rocks and
minerals, water, air, cosmic rays from outer space and a wide range of consumer products in and around the home, from smoke alarms and flourescent lamps to old clocks and watches with luminous hands. Even our own bodies are naturally radioactive, and it's not just the nicotine and tar in tobacco that can kill you. In the past sixty
years there has been a small but measurable increase in the background
radiation from such things as nuclear power generation, fallout from nuclear
weapons, moreover your exposure to ionising radiation is significantly
increased if you have an X-Ray, travel regularly by air or undergo radiological
treatment.
The
point is the human race has been exposed to low level doses of
radioactivity since the year dot. We have evolved to deal with it, it
may even have had a part to play in the evolutionary process,
it’s when we get
too much of it that things can go wrong.
Scientists can say with some certainty
how much radiation will kill you outright, and the sort of exposure
that will
make you sick but these tend to massively large doses that we are
never likely to encounter in our normal day-to-day lives. When
it comes to very low levels exposure no one can say exactly how much is
bad for
you.
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