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Re: Alternative isotopes in RTGs?



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> From: Bernard L Cohen <blc+@pitt.edu>
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> Subject: Re: Alternative isotopes in RTGs?
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> On Mon, 13 Oct 1997, Donivan Porterfield, LANL CST-3 wrote:
> 
> > 
> > Given all the attention to the Pu-238 in the Cassini RTGs
> > I was wondering what other isotopes might have been suitable
> > for this application.  Below are those alpha emitters with
> > half-lifes of 10 to 150 years.  Presumably beta emitters,
> > despite possibly having a higher energy density (MeV/Z),
> > would not be desirable due to bremsstrahlung.
> > 
> >    Po- 209   103   a
> >    Ac- 227    21.8 a
> >    U - 232    72.0 a
> >    Pu- 238    87.7 a
> >    Cm- 243    28.5 a
> >    Cm- 244    18.1 a
> >    Cf- 250    13.1 a
> > 
> > For example, in retrospect would U-232 have been a less
> > controversial isotope to use in RTGs?  This given that this
> > or the others are feasible, e.g. cost of of production and
> > other technical issues such as gamma emmissions or physical
> > properties.
> 
>     --There is no reason to believe that these would be less dangerous
> than Pu-238
> 
U-232 is very rare and would be extremely expensive to produce.  
Further, ingrowth of its daughters, particularly Tl-208, would 
require serious shielding of the RTG until launch.
  Jim Thompson> 



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