Development of an underwater manipulator for maintaining nuclear power reactor

The safety and reliability of nuclear power plants has become more important recently. Inspection and maintenance of nuclear power plants should be continuously implemented. However, the limitation of a radiation exposure makes it difficult to work in nuclear power plants. So a robot is very useful to inspect and maintain the components of nuclear power plants because of reducing radiation exposure to human operators and improving reliability of the operation. Particularly, a nuclear reactor vessel is a restricted area because it has a high radiation level under water during an overhaul. An underwater manipulator is needed for detecting and removing a loose part in a nuclear reactor vessel. The loose part, that comes from any failed component or an item left during a construction, refueling or maintenance like metallic parts, bolts, nuts and washers, affects the safety of a nuclear power plant. An underwater manipulator is developed in this study for removing some particles at the bottom of a nuclear reactor vessel and a reactor coolant system. We developed a 5-DOF underwater manipulator. The developed underwater manipulator could work at 30 m under water with the radiation exposure.