In a number of robotic industrial applications, human workers are replaced by machines mostly because the latter are more efficient, precise, productive, and can do monotonous tasks without getting tired.
However, in nuclear applications, the objective is more to extend the presence of robots or to enable them to reach areas where the thermal or radiation environment limits the presence of a human.
Robots do tasks such as handling heavy radioactive loads and performing tricky repair and maintenance operation in contaminated areas. Presently, a number of sophisticated robots have been developed for use in nuclear power plants.
A demonstration at Toshiba’s technical center in Yokohama in February, 2013 showed a Toshiba decontamination robot to be used in the Fukushima nuclear power plant. The crawler robot is capable of blasting dry ice particles against contaminated walls or floors:
The robot is theoretically capable of cleaning a space at the rate of 2 m2/h; however, the present system can hold ice for only half an hour. The robot will be tested by engineers at a separate nuclear plant after which it will be introduced to the Fukushima nuclear plant.
The EU launched the TELEMAN research program in 1989 and the program has succeeded in developing a number of robots for nuclear power plants. TELEMAN 18 is a smart internal gripper-and-arm system to enable remote handling in hostile environments.
Dutch, Belgian, Danish and British researchers together developed a system to perform repairs on nuclear installations by guiding the arm and gripper simultaneously.
TELEMAN 44, named as ROBUG has eight legs with suckers and can tread through crowded areas and also climb walls. TELEMAN 48 was equipped with optical systems and sensors and finds applications external to the nuclear industry.
The Messina robot, TELEMAN 50 was developed under the supervision of the Forschungszentrum in Karlsruhe, in partnership with the Fraunhofer- IPA and CEA.
The Messina robot is operational and can transport bulky, heavy loads in hostile environments. It includes four cars that can move vertically allowing the convoy to climb obstacles that are easily identified by the control and optical systems.
The wheels to this convoy are clover-leaf-shaped and are developed to climb up and down steps. The train is capable of changing direction, follow a corridor path, avoid collisions and many other actions.
A man–machine interface is meticulously designed that helps the person supervising Messina to control all activities with very high accuracy.
MIT researchers developed a robot prototype in 2011 for improving nuclear power plant safety. The robot is a tiny egg-shaped structure with cameras and developed for withstanding radiation.
This robot is designed to swim through cooling pipes in a nuclear power plant and check for leaks, corrosion or other problems.
This robot moves around in the water with an advanced valve system and does not have any external appendages, which is one of the major features to this robot. Closing off a number of channels allows this robot to shoot water through a specific valve.
A window is opened at the valve end by the high pressure water that rushes out of the robot and forms a jet stream, which in turn moves the robot in the opposite direction.
Robots used at the Fukushima power plant include the following:
Initially 510 PackBot robots were used at the nuclear power plant. This robot captured images that were seen by operators present a safe distance away.
Later, Quince, a tractor tread robot developed at Tohoku University and the Chiba Institute of Technology, was used for investigating harder-to-reach places. The robot uses four small tracks and two main treads to move through difficult terrain and is suitable to work under high-radioactivity conditions.
An unmanned water cannon truck with a German-concrete pumping vehicle, remote-control systems by Toshiba and shields that block radioactivity have been applied on site.
Six mobile robots ranging from heavy construction vehicles to lightweight surveillance machines as well as a remote-controlled Bobcat payloader with night-vision cameras, thermal-imaging systems and radiation detectors.
Swedish company, Brokk AB provided robots for rubble removal at Fukushima.
The following video is a great demonstration of the type of robots that are used against high radiation:
Robots can be used for the following applications in nuclear power plants:
Underwater inspection and surveillance
Remote operation and maintenance
Improved monitoring of health physics tasks
General operation and maintenance tasks
Preprogrammed inspection of controlled radiation areas
Cooling tower basin sediment cleaning.
Japanese Company Mitsubishi recently revealed a radiation-resistant robot that can clean up the crippled Fukushima nuclear power plant.
The robot is named MEISTeR (Maintenance Equipment Integrated System of Telecontrol Robot), is of height 1.3 m and can hold loads of up to 15 kg. The robot is fully equipped with sophisticated tools and has hardened electronics for resisting radiation.
Operating in such challenging environments requires a great number of human skills that may be taken for granted otherwise.
It is important that these robots have conscious reasoning mechanisms such as learning with subconscious sensing mechanisms. Experts believe that it is better to design custom robots performing specific tasks. In case nuclear robots leak hydraulic fluid they must send an alarm before they fail so that they can be recovered quickly.