Uranium
Ionizing Radiation
The radiation released from radioactive atoms is called 'ionizing
radiation'. This is because when the radiation hits an atom or molecule
it converts the atom or molecule to a charged particle (ion). Ionizing
radiation is also released by nuclear
fission. Ionizing radiation is a form of energy. It travels through
space in the form of invisible particles or waves.
Ionizing radiation is a type of radiation that is uniquely
different to other forms of radiation such as heat, light, sound, microwaves,
radio waves, and radar, which are non-ionizing.
Background ionizing radiation
Like many hazardous substances such as arsenic, lead, and
mercury small amounts of ionizing radiation are everywhere. This makes
up the "background
ionizing radiation" that, to varying degrees, we are exposed to everyday.
Like hazardous substances, exposure to ionizing radiation varies from place
to place and from occupation to occupation. Because all ionizing radiation
is hazardous it is in our interest to minimize our exposure to it, even
background ionizing radiation. Sometimes this is relatively easy, sometimes
it is impossible.
Types of ionizing radiation
There are three types of ionizing radiation emitted by radioactive
isotopes. We call these three types alpha, beta and gamma. Alpha and beta
ionising radiation are defined in terms of the emission of alpha and beta
particles whreas gamma ionising radiation is defined in terms of
the emission of gamma rays. Other forms of ionising radiation defined in
terms of rays rather than particles are X-rays and cosmic rays. |
| Alpha particles are very heavy and
lose their energy quickly. They are positively charged, and are also quite
large, and therefore cannot travel very far, or pass through matter such
as a piece of paper or human skin. The entire energy from alpha radiation
is absorbed (deposited) over a very small region. It is therefore very
damaging to living cells and tissue. Extreme care must be taken not to
swallow or inhale anything likely to emit alpha particles.
Beta particles are small (and negatively charged).
They are fast moving and can travel further than alpha particles. They
can penetrate up to 1 - 2 centimetres of matter such as human skin.
Gamma rays are high energy waves, similar to light,
but have much higher energy, and can travel very long distances. Materials
such as concrete, metal, and water can stop them provided there is sufficient
thickness of the material. |
As well as being emitted during radioactive decay of radioactive
isotopes these forms of ionizing radiation are also emitted during nuclear
fission.
Neutrons are another form of ionizing radiation that is
emitted during nuclear fission.
X-rays are not emitted by radioactive isotopes. X-rays
used in nuclear medicine are produced by bombarding certain metals with
electrons.
Greater technical detail can be found on this topic by searching through
the publications at www.ccsa.asn.au
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© 2002 Conservation Council of SA.
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