Well, that was a lesson on how crappy Google has gotten with historical, even recent historical data. All searches for Fukushima robots were events of the last two days. At least adding "2012" let me find some things.

Here's a very simple article on radiation hardening, which incidentally describes the danger to electronics.

https://spectrum.ieee.org/tech-talk/semiconductors/design/ra...

iRobots entered the main building in 2011. What happened just now is robot actually entered or surveyed the actual reactor vessel, in the building.

https://spectrum.ieee.org/automaton/robotics/industrial-robo...