It's not actually a reactor. The plutonium is just emitting radiation, as plutonium will do, and you harness some of the natural heat energy with thermocouples.

It's not actually a reactor. The plutonium is just emitting radiation, as plutonium will do, and you harness some of the natural heat energy with thermocouples. There's no explosion risk, although you would certainly need trustworthy shielding.