Yoshiyuki Sankai, professor of engineering at the University of Tsukuba, said this means the 60-kilogramme (130-pound) tungsten vest workers at Fukushima have to wear is almost unnoticeable.

He said the outer layer of the robot suit also blocks radiation, while fans inside it circulate air to keep the wearer cool, and a computer can monitor their heart-rate and breathing for signs of fatigue.

The robot is manufactured by Cyberdyne, a company unrelated to the fictional firm responsible for the Terminator in the 1984 film of the same name.

HAL was on display as part of Japan Robot Week, which also featured small robots that run on caterpillar tracks designed to move across difficult terrain and gather information in places where it is not safe for humans.

Inventor Eiji Koyanagi of the Chiba Institute of Technology said the devices could be deployed very close to the damaged reactor core at Fukushima.

“We have to think of ways to protect nuclear workers, otherwise Fukushima won't be sorted out,” he said.

A huge tsunami in March 2011 smashed into the power plant, sparking meltdowns that forced the evacuation of a huge area of northeastern Japan.

The decommissioning of the crippled plant is expected to take several decades.