
TLD ring badges are very important for individuals involved in eluting generators, preparing kits, and injecting patients.

Monitoring
Devices: TLD
The
thermoluminescent dosimeter depends
on thermoluminescent phosphors, such as lithium fluoride, that trap
electrons freed by radiation exposure.
The
trapped electrons release light when
the application of heat frees the electrons, returning them to stable energy
states. The process can be repeated many times.
Instead
of reading the blackness (optical
density) of a film, the amount of light released versus the heating of the
individual pieces of thermoluminescent material is measured as a "glow
curve" which is then related to the radiation exposure.
Lithium
fluoride in the form of powder
compressed into pellets has advantages over film badges by being tissue
equivalent, by having an exposure range from a few hundredths of a
millisievert to over 100 Sv (10000 rem), by exhibiting little fading over
time in storage at room temperature and by being free of many of the
problems associated with film.
In
the badge, a pellet is placed behind
each of the filters so that radiation energy information is obtained as well
as consistent readings. The ability to reuse the pellets is also an
advantage.
If the lithium is enriched with Li-6, the lithium fluoride becomes very sensitive to thermal neutron interaction and a pair of pellets (one enriched and the other not enriched) can provide neutron exposure information.