There is no uranium or plutonium in these satellites, nor anything else radioactive. On the other hand, according to [1] the abundances on this page multiplied by [2] 40000 tons per year, the stuff naturally hitting the atmosphere each year includes 0.3 kg uranium, 1.6 kg thorium, 3 kg radioactive isotopes of potassium, 10 kg mercury, 18 kg cadmium, 50 kg lead, 72 kg arsenic, and 120 tons of chromium, among other things. This stuff burns up in the atmosphere all day long, and has for billions of years.

[1] https://periodictable.com/Properties/A/MeteoriteAbundance.v.... [2]https://link.springer.com/chapter/10.1007%2F978-1-4419-8694-...