This has been stated in book ten when the Chee are introduced, but I don't think it has in any other book. The fact that Eric can keep his Yeerk alive without letting it go in the pool has gotten me thinking in past occasions.
Depending on how large a scale this could be done, it could have really helped the Yeerk Peace Movement. In fact, it might have been a way to end the war, if robots could be designed that could be controlled by Yeerks and produce enough radiation to sustain one Yeerk life. If it's possible for a Yeerk to control a robotic brain, that is.
It also could have enabled Aftran to join the Animorph group, and continue to lead the YPM she founded. Instead of becoming a whale nothlit.
What do you guys think?