Re: Alternative isotopes in RTGs?

[MCNAUGHT@lanl.gov (Mike McNaughton)]

When considering alternative nuclides for Cassini, there are several
additional questions to consider. For example:
1. is the daughter short-lived or long-lived? U-232 and Ac-227 daughters are
short lived, so each decay is soon followed by a string of decays emitting
betas and high-energy gammas. In contrast, the first Pu-238 daughter is long
lived, so the grand-daughters do not grow in.
2. What is the spontaneous fission cross section? (this could be a problem
for Cf-250)
3. What is the availability. Po-209 looks like it would work, but is it
available?

>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.  
>
>   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


"Shlala gashle" (Zulu greeting meaning "stay safe") mike