Re: Alternative isotopes in RTGs?

[Vincent.King@DOEGJPO.COM (Vincent King)]

     I don't know how feasible it would be to produce the alternatives 
     listed or whether their performance characteristics would be 
     acceptable, but their use would gain you nothing from a risk 
     standpoint. Dose conversion factors for most of the isotopes listed 
     are even higher than for Pu-238 (...I guess plutonium is NOT the most 
     toxic material around then..?)
     
     The reason is the specific alpha activity....once you get a nuclide 
     with specific alpha activity high enough to give you similar thermal 
     characteristics to the Pu-238, you get similar alpha energy deposited 
     in the lungs per gram inhaled as well, so any resulting inhalation 
     dose would be about the same.
     
     Of course, the other radionuclides don't have the name-recognition 
     with the public that plutonium does, so maybe from a pure public 
     relations view, they would be better.  After all, it would be harder 
     for the "flat-earth society" to stir up opposition to something no one 
     has ever heard of...
     
     Vincent King
     vincent.king@doegjpo.com  
     
     


______________________________ Reply Separator _________________________________
Subject: Alternative isotopes in RTGs?
Author:  "Donivan Porterfield; LANL CST-3" <dporterfield@lanl.gov> at Internet
Date:    10/13/97 12:52


     
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