Activity of waste

[MCNAUGHT@lanl.gov (Mike McNaughton)]

Does anyone know the details of the log-log graph of the nuclides in
radioactive waste as a function of time, which is copied (with
modifications) in most articles on radioactive waste, e.g. in the June 1997
issue of Physics Today (special issue on radioactive waste) page 34. It
shows Cs-137 and Sr-90 dropping over hundreds of years, Am-241 over
thousands of years, Pu over hundreds of thousand of years, etc. 

In particular, I am puzzled by the "burst" of relatively short-lived
nuclides which appears (like the finale of fireworks on July 4) near the end
of the graph. Ra-226 (half life 1600 yrs) should be in secular equilibrium
with U-238, which is almost constant on the graph, so why does Ra-226
increase by several orders of magnitude to become the most hazardous
nuclide, still increasing after a million yrs? I am also puzzled by Pb-210
(half life 23 yrs) which should be in secular equilibrium with Ra-226, but
which rises more rapidly than Ra-226, and is shown as the most hazardous
nuclide at time = 100,000 yrs.

I would like to be able to reproduce these calculations, but there are some
pieces of the puzzle that I am missing. Can anyone tell me where this graph
came from originally, or who did the calculations, or how?

Thanks, mike

"Shlala gashle" (Zulu greeting meaning "stay safe") mike