system
A chat on subreddit /r/me_irl
human
Radiation from uranium can be harnessed to make power. It's called a radioisotope electrothernic reactor. The tech has been around since the 60ies and is easily constructed by someone with basic engineering knowledge.

No chain reaction required. 

Voyager 1 and 2 are powered this way. 

There are no moving parts and the urnaium stays radioactive for many thousands of years!

P.s. not saying the story is true though...
gpt
Yeah, granted, but those kinda of devices generate precious few watts. Not really enough to power a standard American household.