Toshiba Corp., co-developer of the "scorpion" crawler that was demonstrated Tuesday, said the robot will venture into Unit 2 reactor's primary containment vessel in August after a month of training for its handlers.
Officials hope the robot can see the fuel in the pressure vessel in the middle of the reactor. The fuel hasn't been located exactly and studied because of the fatally high radiation levels nearby.
The difficult work of decommissioning the Fukushima plant damaged by the 2011 earthquake and tsunami will take decades.
The scorpion robot is the second to enter a primary containment vessel, after a "snake" robot was sent in April inside the worst-hit Unit 1. The robot was unable to spot melted-fuel debris there.
This time, the "scorpion" crawler, which is 54 centimetres (21 inches) long when it is stretched, will enter through a duct designed as a passageway for fuel rods.
During the demonstration at a Toshiba lab near Tokyo, the robot slid down a railing and stretched out like a bar, with a head-mounted LED showing its way. After crawling over a slight gap and landing on a metal platform, the robot lifted its tail, looking up the bottom of the control rod drive, a structure above the platform simulating where some melted nuclear fuel might be left.
The "scorpion" also demonstrated it can roll back upright if it hits an obstacle and rolls over. The ability comes from a tail joint in the middle that bends.
One operator controls the robot with a joystick, and another monitors video feed from the robot and other data. At the Fukushima plant, the robot will be operated remotely from the command centre in a separate building.
The work is planned for a full day. The robot is designed with radiation tolerance allowing it to stay more than 10 hours inside Unit 2 reactor.