Re:: Dose rate constants -Reply -Reply

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

One of the pedagogical excercises I like to give new staff
is to review the literature for half lives of isotopes
that have half lives between a few tens and a few hundreds of
years.  They are usually amused at how much scatter there is
in the reported values.  It usually takes quite a bit of coaxing
to get them to work out why in this modern age we haven't nailed
something that simple down.  There are two basic ways of determining
half lives. one is to measure the rate of change of decay rate
which is easy with short half lives, but it is tough to keep a
detector setup stable enough to get a good measure of the
change in decay rate as a function of time.  The second require
knowing the number of atoms of radioactive material present
and the activity of the sample.  It is tough to get weighable
quantities of many isotopes in this half-life regime.