The Soviet Union used radiodecay thermoelectric generators with breathtaking liberalness. Radio relay links, lighthouses, nav beacons, remote weather sensors. Approximately a thousand nuclear batteries were made and deployed. The budget for their maintenance fell with the USSR. While a lot of them have been collected, there's still hundreds still out there.
In 2001 a group of men in rural Georgia [0] stumbled across one; unaware of the nature of what they found, they took benefit from the warmth of it on a cold night. Three were sickened and one died of radiation poisoning.