[AJames]

Originally Posted by [1ponders]

The Voyagers were nuclear powered

Quite right. A couple pounds of radioactive plutonium used to power the cameras and keep the electronics warm. The plutonium is encased into stone-like material, and protected from an outer case - just on case it falls back to earth or the rocket explodes on take-off. However the older spacecraft were not made so well, especially the Russian ones due to cost cutting.
Plutonium is fairly toxic - not something that animal and human cells survive very well without chromosome damage and radiation sickness- and it doesn't take much of it either.
The reason why radioactive material is required to power the spacecraft away from the sun in the outer solar system, Nearer Earth all that is required is solar panels soaking up sunlight to generate free needed power for the satellite systems.