Reactors? The article doesn't mention any reactors. If you're talking about radioisotope thermoelectric generators (RTGs) used on spacecraft, they are limited

Reactors? The article doesn't mention any reactors. If you're talking about radioisotope thermoelectric generators (RTGs) used on spacecraft, they are limited to deep space (Voyager, Cassini, etc) and long duration planetary missions (Curiosity rover) only. Only a handful of 1960's military satellites used RTGs on Earth orbit [0]. RTGs also tend to be rather small, the environmental impact of the small amount of Pu-238 shouldn't be very large (compared to nuclear testing or nuclear incidents for example). There may be Hydrazine (propellant) or other nasty environmental hazards on spacecraft that would be more significant. [0] https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Nuclear_power_systems_in_space https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...