Re: RADSAFE digest 1577

[Dick King <king@reasoning.com>]

> 
> Date: Tue, 14 Oct 1997 15:21:55 -0600
> From: "David W. Lee" <lee_david_w@lanl.gov>
> To: radsafe@romulus.ehs.uiuc.edu
> Subject: Re: Alternative isotopes in RTGs?
> Message-ID: <3.0.1.32.19971014152155.006ea58c@esh-mail.lanl.gov>
> 
> 	I surmise that Pu-238 emerged as the RTG isotope of choice based on
> consideration of the following information regarding many potential
> candidate isotopes:
> 
> ISOTOPE  Half-life (y)	SpA (Ci/g)	Energy Output	   Daughter      How Produced

...

> 
> Cm-243		29.1		50.56		1.75		   Pu-239		reactor prod
> 											from U-238

> 	For a power consuming, multi-year space mission, in order to maintain a
> stable level of heat, I would tend to select those isotopes of half-lives
> approximately 100 y, then of those, select the one with the highest heat
> output.

Well, we could probably live with a few decades or longer.  This is, after all,
"only" a fifteen year mission [including the extended plan].

>		   This small group includes Po-209, U-232, Pu-238, and Pu-239.
> Eliminate Po-209 due to difficulty to produce and eliminate U-232 due to
> eventual Rn gas buildup which might cause RTG rupture.

Cm-243 looks tempting.

However, there's one criterium you left out.

Helium buildup can also be an irritation.  You therefore want the alpha
particles to be as energetic as possible so you get maximal energy output for
each unit of helium production.

How do these stack up.

-dk