RE: A real solution

["Heinmiller, Bruce" <heinmillerb@aecl.ca>]

I'll deny it (at least for CANDU fuel, which is unenriched in U-235 and
U-234).  I've seen a variation of this factoid before, and it may be
confusing radioactivity with some attribute of the fuel other than its
activity.  Unat, even assuming elemental U, which fuel isn't, has a specific
activity (normalized to elemental Unat) of about 12.4 MBq/kg for each of 4
nuclides (U-238, Th-234, Pa-234m, and U-234), and about 0.576 MBq/kg for
each of  2 other nuclides (U-235 and Th-231).  Spent CANDU fuel after 1000
years has a specific activity of more than 2E4 MBq/kg.

Bruce Heinmiller CHP
heinmillerb@aecl.ca

> ----------
> From: 	Bob Flood[SMTP:bflood@SLAC.Stanford.EDU]
> Reply To: 	radsafe@romulus.ehs.uiuc.edu
> Sent: 	Friday, August 18, 2000 3:41 PM
> To: 	Multiple recipients of list
> Subject: 	Re: A real solution
> 
> >I am curious, though, about the composition of spent fuel (not my
> >field).  What are the shorter half-life isotopes of concern (say those
> >that will be mostly gone within 300 years) vs. the very-long half-live
> >ones, and their relative proportions?
> 
> Some years ago I was told by someone whose opinions I respect that the
> oft-used 10,000 year worry period is way off and that spent fuel will
> decay
> to being no more radioactive than the original unirradiated fuel in about
> 300 years. I have not tested this assertion and haven't seen any other
> calculations of this sort. Can anyone confirm or deny this claim? Might
> there be a reference on this?
> ============================
> Bob Flood
> Dosimetry Group Leader
> Stanford Linear Accelerator Center
> bflood@slac.stanford.edu
> 
> 
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