Module 104 Internal Dose Control
primarily decays by emitting an
alpha particle. Many uranium
decay products also decay by
emitting alpha particles.
Alpha particles are highly charged
and will only travel about 2 inches
in air. Alpha particles are also
stopped by the dead layer of skin.
This means that alpha particles
external to the body are not a
health concern. It also means that
alpha particles are hard to detect
because the detector must be close
to the source of the material
emitting the alpha particle.
There are many detector types
available for detecting alpha
contamination. Two of the most
commonly used types are
scintillation detectors and gas
proportional counters. A thin
window Geiger-Mueller (GM)
detector, such as a pancake probe,
will also detect a small portion of
the alpha radiation emitted.