First let me say that I know almost nothing but the basics about nuclear fission. I know more about nano robotics but I've got no degree in the matter, just a rather in depth curiosity and a lot of hours logged in researching the matter. I am pretty much clueless but who knows, maybe I'll get lucky.
So the question, or rather the idea: I know one of the current running issues for nanobots/nanites/etc. is the fact that there is a lot needing to be crammed into such a small package including a power supply. This problem is exacerbated if the idea is that these nanobots are going to be performing complex tasks that we might not be able to do otherwise, at least not easily.
So I have been thinking: what if the nanobots were their own battery? Now I know that by the law of conservation of energy this is impossible but follow me here for a minute.
The process of nuclear fission the end result of the process is minuscule compared to that in which was used to make it and is also radioactive with a extensive half life. Now what I'm wonder is if this radiation is usable as an energy source, and if so would a nanobot created with such material could used that radiation as a source of energy thus in concept be self powering