Sources may be described according to the activity and half-life of the
radionuclide they contain. Sources containing radionuclides with half-lives of
less than 100 days (e.g. 90Y, 192Ir, or 198Au used in brachytherapy) may be stored
for decay and eventually disposed of as exempt waste. Other sources such as
those containing 137Cs, 60Co or 238Pu have longer half-lives and other
management options will be required. A breakdown of different types of
sources is given in Table III–1