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RE: Ancient radiation levels were higher than today's levels
....I take it that includes the shorter-lived isotopes of uranium, such as
U235 -- what about longer-lived TRANS-uranics, like Pu-244 ? Are these
assumed to have vanished long BEFORE the formation of the solar system ?
(ie. ~ten half-lives, ~1GY)
And what about short-lived isotope deposition POST-formation of the planets
- from near-by supernova explosions - do we have any clue how many such
events there might have been & how much each one contributed ? What about
more common occurrences of Oklo-style radioisotope generators 4GY ago ?
Dear Jaro,
We did account for the different isotopic composition of U in the past (up
to about 17% when life first showed up). We did not look at Pu-244, I-129,
or possible supernova-deposited nuclides. We're working on those now.
Specifically, we're currently looking at gamma dose from supernovae and
gamma ray bursts within our galaxy and at the effects of changing
atmospheric composition. future work will look at the deposition of
supernova debris and the formation of cosmogenic radionuclides in the wake
of such events. To be honest with you, I feel somewhat sheepish that we
haven't thought about other Oklos - have to think about that one.
We will be presenting a paper at the upcoming IRPA Congress on the
supernova/GRB dose calculations - it's been accepted, the math is done, and
we just have to finish writing!
Sincerely,
Andy
Andrew Karam, CHP (716) 275-1473 (voice)
Radiation Safety Officer (716) 275-3781 (office)
University of Rochester (716) 256-0365 (fax)
601 Elmwood Ave. Box HPH Rochester, NY 14642
Andrew_Karam@URMC.Rochester.edu
http://Intranet.urmc.rochester.edu/RadiationSafety
We cannot prove that those are in error who tell us that society has
reached a turning point, that we have seen our best days. But so said
all before us, and with just as much apparent reason. On what principle
is it that, when we see nothing but improvement behind us, we are to
expect nothing but deterioration before us? Lord Thomas B. Macaulay,
1830
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