Swimming, shape-changing robots for Fukushima

Two robots have been jointly developed by Hitachi and Hitachi-GE Nuclear Energy to help investigate the Fukushima Daiichi nuclear power plant in Japan. One robot is submersible while the other is shape-changing.

Two robots have been jointly developed by Hitachi and Hitachi-GE Nuclear Energy to help investigate the Fukushima Daiichi nuclear power plant in Japan. One robot is submersible while the other is shape-changing.

The submersible robot, left, and the shape-changing robot, right (Image: Hitachi)

The robots will be used in various investigations at the plant ahead of development of remote-controlled systems for the removal of fuel from the units.

The submersible robot has been developed to identify and investigate locations of leakage in reactor buildings where radioactive water has accumulated.

Weighing just under 32kg, the robot is manoeuvred using six thrusters - four for vertical movement and two for horizontal. It is also fitted with two crawlers. The robot is capable of travelling horizontally through water or along the bottom of a pool, as well as vertically, such as up the wall, by using suction. With a height of 33cm, a length of 60cm and a width of 45cm, the robot can access narrow spaces underwater. The robot is operated via an 80-metre length of cable.

The shape-changing robot has been developed to investigate hard-to-access areas of the plant. It consists of three segments: the robot's main body and two compact crawlers. The robot can assume a long, straight shape for passing through narrow spaces, such as pipes. In tests the robot was found to be able to pass through pipes with a diameter of just 10cm. Alternatively, it can rotate its crawlers by 90 degrees in relation to its central body to assume a U-shape, with the crawlers providing better stability when travelling over flat surfaces.

The robot is 9cm in height. Depending on the position of its crawlers, it is 25cm to 64cm in length and between 6.5cm and 27cm in width. Weighing 7.5kg, the robot is operated via a 40m cable.

Robots are frequently used in nuclear and other industries to access difficult-to-reach or highly contaminated areas. At Fukushima, robots have been used to survey the damage inflicted on the plant after the 2011 tsunami and are being developed to undertake more complex tasks.

Hitachi has already supplied the remotely-controlled ASTACO-SoRa compact heavy-duty robot, which has been used for rubble clearance at the site. Others have been developed by such companies as Mitsubishi Heavy Industries, Toshiba and Honda.

Researched and written
by World Nuclear News