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JET Remote Maintenance During Active Operation

J. R. Dean, T. Raimondi

Fusion Science and Technology

Volume 11 / Number 1 / January 1987 / Pages 253-281


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As Joint European Torus (JET) is used more and more with deuterium and tritium plasmas, the machine will be irradiated by high-energy neutrons to a level that prohibits approach by human beings. All modifications and maintenance will then be carried out by remotely controlled equipment and no further attempt will be made to do hands-on work either directly or through local shielding. The remote handling equipment will comprise a series of special transporters carrying end-effectors and tools. One important transporter is a large articulated boom (arm) with nine axes of motion capable of carrying 1 tonne into the tokamak vacuum vessel and positioning it within a few millimetres. Another is the high-precision 150-tonne crane used during JET construction. These and other transporters will give access to all parts of the machine. The various end-effectors are special motorized attachments to the transporters, enabling them to carry and manipulate heavy components. An important end-effector is the (Mascot-type) force-feedback servomanipulator by which very dexterous operations can be performed and special tools placed and held in position. Most identified remote handling tasks require the combination of dexterity and load carrying provided by the manipulators in conjunction with the transporters. A range of tools, many specially designed because of space and access restrictions and the need for meticulous cleanliness, will include cutting and welding tools, largely automatic and in some cases self-propelling. Many design features have been used on JET to make remote handling possible or easier. For example, ultra-high vacuum-welded joints are made between 2-mm-thick Inconel lips, and bolted vacuum flanges have been specially developed. Remote operations will be viewed through a system of closed circuit television, some cameras being stationary and others carried on transporters. All operations will be controlled from a special central control room. A NORD 100 computer (one of JET's main array) will interconnect the control circuits between equipment and consoles and between cameras and displays. Eventually, it will also provide high-level control input to enhance operator control. Some of the remote handling equipment has been used successfully in support of hands-on work and much more will have been used and proven by the end of 1986 when the tokamak is shut down. Full remote handling will become necessary during 1990.

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