https://en.wikipedia.org/wiki/Voyager_2 "Voyager 2 is equipped with 3 Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG includes 24 pressed plutonium oxide spheres, and provided enough heat to generate approximately 157 W of electrical power at launch. Collectively, the RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years), and will allow operations to continue until at least 2020”
Полураспад 87.7 лет. Плутоний.