The US Department of Energy, authorized last year to resume production of Pu238, has just announced production of a 50-gram sample. This isn’t enough to do anything useful, but it validates the restarted production system at Oak Ridge National Laboratory. THis is vital to the future of robotic space exploration, because Pu238 is the best substance to power a spacecraft via radioisotope thermoelectric generator, and even after buying up Russia’s entire stockpile, we’re very nearly out. We have maybe enough for two or three missions, provided they happen fairly soon: the Pu238 is decaying all the time, so the longer we wait, the less of it we still have. That plutonium is presently earmarked for the next Mars rover and a probe to Jupiter’s moon Europa.
Plutonium 238 is a fairly useless isotope, from a fission standpoint. It does decay radioactively, but it can’t be made to produce a fission chain reaction. This makes it useless for nuclear reactors and for nuclear bombs. It can’t even be produced as a byproduct of Pu239 production. The only thing it is good for is RTGs, which convert the heat emitted as it decays into electricity. But people are fearful anytime radiation or plutonium are mentioned, and so the DoE has been forbidden to produce any more for a long time. But finally the blinkers have lifted, and this important resource is being produced again.
Now . . . I can haz Titan Mare Explorer, plz?