Alternative isotopes in RTGs?

["Donivan Porterfield, LANL CST-3" <dporterfield@lanl.gov>]

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.


Donivan Porterfield              (505) 667-4710
Los Alamos National Laboratory   (505) 665-5982 fax
MS K484, CST-3
Los Alamos, NM  87545             dporterfield@lanl.gov