Nuclear work is a whole different kettle of fish - you need to harden all of the sensitive parts of the system. Cameras will fail (or their lenses will frost over), circuitry will fail, and your robot needs to be able to be decontaminated when it gets back.

Fukushima has lots of problems for robots - hard radiation, not enough in air bandwidth to support radio communication and control, and terribly difficult maneuvering and communication conditions.