Nuclear "Waste" is actually great stuff for power generation, just as long as the waste
is primarily an Alpha or Beta emitter. Gamma and Neutron emissions can cause
structural damage over time, and can result in the creation of isotopes which are
radioactive. In other words, choose your materials carefully or your machine could
become radioactive.
Traditionally, NASA has used RTGs (Radioisoptope Thermal Generators) for their
space-based power needs. These use a simple thermocouple to convert heat into
electricity. Unfortunately, these are also tremendously inefficient, converting only
about 10% of the energy into power. This means that 3.8 kilograms of Plutonium-238
(not useful for nukes, half-life of ~80 years, Alpha Emitter) only produces about 75W
of electricity. The SNAP-27s used in the Apollo missions are still providing a constant
70W of power to instruments on the moon. RTGs have also been used in pacemakers
and earthbound remote research stations. The later form tends to use the less
powerful Strontium-90 (beta emitter) as a fuel source.
NASA has recently begun looking at SRGs (Stirling Radioisotope Generators) for space
missions, because the SRGs are far more efficient and fuel conservative. The current
designs produce about 50W per 600 grams of Pu-238. None have yet flown, however,
because NASA is concerned about the vibrations interfering with the operation of
delicate instruments.
More info:
http://me.eng.sunysb.edu/~mec290/rtgs/page5.html
http://www.nasm.si.edu/exhibitions/attm ... s27.1.html
http://www.grc.nasa.gov/WWW/RT2002/5000/5490thieme.html
P.S. A lot of good power generating materials are thrown away because of the public's
fear of all things radioactive. A perfect example of this problem, was the protests
over the launch of the Casinni probe. Despite the fact that the RTGs were packed in
cases that could survive an explosion and unprotected reentry, people's primal fears
had them convinced that the RTGs were going to kill everyone. Even if the Plutonium
did escape, it wouldn't have caused as much harm as people believe. Here's a writeup
on that:
http://www.llnl.gov/csts/publications/sutcliffe/