Other firms, among them Hitachi and Toshiba, have also rolled out their own remote-controlled bots recently. The plant was damaged during the 2011 earthquake and tsunami. Robots are already working inside the plant, but none has been specifically designed for this kind of work.
One UK expert said that working inside a nuclear reactor was "a challenge for robotics". Dubbed MEISTeR (Maintenance Equipment Integrated System of Telecontrol Robot), Mitsubishi's "tankbot" is about 1.3m (4ft) tall and has two arms with seven degrees of freedom each, able to hold loads of up to 15kg (33lb).
The robot is equipped with various tools and has electronics hardened to withstand radiation. But Jeremy Pitt, deputy head of the Intelligent Systems and Networks Group at Imperial College London, said it was still a challenge for a remotely controlled machine to successfully replace humans in such harsh conditions.
"Operating in extreme environments requires a remarkable range of human skills that might otherwise be taken for granted," he said.