For example, each atom of the Pu-238 isotope contains 144 neutrons, while each atom of the Pu-239 isotope contains 145 of these neutral particles. Radioactive isotopes are further characterized by ...

Plutonium-238 (238 Pu) undergoes α- decay with a half-life of 87.7 years and an average ray energy of 5.49 MeV, which can continuously release heat and provide a heat source for this scenario.