Robots could monitor underground pipes for radioactive leaks

Spherical robot equipped with a camera. Image: Harry Asada/d'Arbeloff Laboratory
Researchers from Massachusetts Institute of Technology have developed innovative egg sized robots designed to dive into nuclear reactors and 'swim' through pipes, checking for signs of corrosion.

The devices are equipped with cameras and are able to withstand a reactor's extreme radioactive environment, transmitting images in real time from within. The robots were developed as an alternative to traditional methods of monitoring buried piping, which involves generating a voltage gradient to identify areas where pipe coatings may have corroded and using ultrasonic waves to screen lengths of pipe for cracks. The only direct monitoring requires digging out pipes and visually inspecting them, a costly and time intensive operation.

Harry Asada, director of MIT's d'Arbeloff Laboratory for Information Systems and Technology and his graduate student, Anirban Mazumdar constructed the robot as a smooth sphere, devising a propulsion system that can harness the force of water rushing through a reactor. A special valve for switching the direction of a flow with a tiny change in pressure was devised and a network of the Y shaped valves was embedded within the hull of the robot. This was achieved using 3d printing to construct the network of valves, layer by layer.

Depending on the direction the robot is required to swim, various channels can be closed off to shoot water through a specific valve. The high pressure water pushes open a window at the end of the valve, rushing out of the robot and creating a jet stream that propels the robot in the opposite direction. As it navigates a pipe system, the onboard camera takes images along the pipe's interior which can be analysed later. The team is currently working to equip the robot with wireless underwater communications using laser optics to transmit images in real time across distances of up to 100m. It is also working on an 'eyeball' mechanism that would let the camera pan and tilt in place.
The robots are designed to be short term, disposable patrollers, able to inspect pipes for several missions before breaking down from repeated radiation exposure.

"The system has a simplicity that is very attractive for deployment in hostile environments," said Henrik Christensen, director of the Center for Robotics and Intelligent Machines at the Georgia Institute of Technology. Christensen, who was not involved in the work, observed that robots such as Asada's could be useful not only for monitoring nuclear reactors, but also for inspecting other tight, confined spaces — sprawling city sewer pipes, for example. "One would like to have a system that can be deployed at a limited cost and risk, so an autonomous system of minimal size is very attractive," he said.

Chris Shaw

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