it's not an accident that even Pu-238 RTGs tend
to be located away from electronics, in fact preferably out on booms --
Right and that's what the booms on Voyagers spacecraft are for. So isn't
that a good solution for rad. damage, just put the RTG on a boom plus put a
shield between the source and spacecraft which wouldn't be that large a
cross section considering the distance and source area.
K
On Mon, Mar 1, 2021 at 8:54 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Tue, 2 Mar 2021, Michael Kelly wrote:
And, yes, Americium 241 is back in production (big time). It would
provide a more level power output in RTG applications, given a half-life
~> 5 times that of Pu 238.
Only if you use one of the "advanced" conversion technologies, rather than
the thermoelectric elements used in all flown RTGs to date. The output
loss of thermoelectric RTGs is dominated by buildup of radiation damage in
the semiconductor thermoelectric elements, *not* by Pu-238 decay. (The
decay is not insignificant but it's a lesser issue.)
Am-241 produces a lot more gammas and neutrons than Pu-238, which would
probably make it worse, not better, for that. They're also an issue for
spacecraft electronics -- it's not an accident that even Pu-238 RTGs tend
to be located away from electronics, in fact preferably out on booms --
and for pre-launch handling.
Am-241's much longer half-life is actually a *disadvantage* for missions
lasting only a decade or three, because it means much lower heat output
per kilogram.
The European interest in Am-241 is not because it's superior, but because
they have no Pu-238 production capability and decided it was hard to get
set up for it. (I'm not sure exactly why.)
Henry