Climbing Service Robot for Duct Inspection and Maintenance Applications in a Nuclear Reactor

Abstract

SADIE climbing robot was commissioned by Magnox Electric plc to perform non-destructive testing of various welds on the main reactor cooling gas ducts at Sizewell 'A' Power Station in the UK. The size of the vehicle was 640 mm x 400 mm x 180 mm and was able to carry the necessary equipment for the range of tasks required, including pre-inspection preparation and ultrasonic weld inspection. The robot uses a sliding frame mechanism actuated by servo motors for precise position of the frames, and pneumatic cylinders for compliant leg control. Vacuum grippers are used for climbing vertical surfaces and magnetic rollers are used for stabling the robot during maintenance operations where large vibration forces can be generated by the tool packages. The vehicles can operate at any orientation whilst negotiating compound curves. A part of the requirement was that the robot would need to climb upside down at the top of the duct to inspect some of the welds. It was therefore necessary to develop a force controlled foot change over sequence in order to prevent the robot to push itself off the climbing surface.