The only problem is its radio active and that means that when it decays it tends to fall apart. It is of course Plutonium and here to spell it out is Cambridge University's Ian Farnan. Plutonium's ...

Beginning in the late 1950s, the U.S. met this challenge by developing nuclear batteries known as radioisotope thermoelectric generators (RTGs) and producing plutonium-238 (Pu-238) as their fuel, ...