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Dec14-06, 07:01 AM
Astronuc's Avatar
P: 21,866
Comparing 4.468 Billion years to 1600 years - that's 6 orders of magnitude.

The ratio of U-238 to Cs-137 or Sr-90 is even greater, 8 orders of magnitude.

Then there are radionuclides that have half-lives of months, weeks, days, hours and seconds. The short the half life, the greater the specific initial or equilibrium specific activity. However, the shorter the half-life, the faster the particular radionuclide decays. On the other hand, that may mean decaying into another radionuclide of longer half life, before decaying into an inert isotope.