Incorrect answer

[Jacques.Read@eh.doe.gov]

Norm posted a question (paraphrased)  "How can you tell 40-year old fission
product strontium from more recent fission product strontium? "
The answer given, namely that "You can't."  is incorrect.  30-year strontium-90
from atmospheric weapons tests is still around ( or nearly half
of it), and persists in surface vegetation.  Recent fission product strontium
will be (mostly, on a picocurie basis) strontium-89.  If the radioassay
finds Sr90 but not Sr89, then it's fallout.

Jacques Read



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