Mercury and Radioisotope Thermalelectric Generators
Country: United States
Date: Spring 2010
Why was mercury used in some radioisotope
thermalelectric generators (RTGs)?
After some extensive searching, I was unable to find a single
reference to the
use of mercury in a Radioisotope Thermoelectic Generator. Do you have
any concrete examples of this? The only use for mercury I can imagine, is to
act as a circulating cooling fluid.
The metal mercury was used in a Rankine cycle generator on the
SNAP-1 RTG to make electric power. It was never deployed. Later
RTG's seem to have used thermoelectric methods to generate the
electricity. The Rankine system is similar to a steam power plant,
but mercury metal is used instead of water. Mercury was found to be
the best working fluid under the conditions and temperatures that
space RTG systems operate. NASA tech note TN D-5092 has useful
information how to make a mercury boiler for use in space.
Nuclear reactors have also been used to generate power in space
using a mercury Rankine cycle, but these are not RTGs.
Russia has many RTGs rusting away all over their country, but I can
find no evidence that they use mercury.
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Update: June 2012