The radiation levels expected in ITER during the later stages of machine operation are such that maintenance work cannot be carried out by human intervention. Remote Handling (RH) was therefore defined by the ITER project, as the nominal solution for the maintenance of the reactor.

Similar considerations provided the main incentive for the development of the RH system at JET. The in-vessel maintenance and divertor modification that followed the introduction of tritium in the DTE campaign (1997) was possible only thanks to the RH methods. Even today, application of ALARA principles, encourages the JET operator to accomplish most of the in-vessel work using remote handling techniques.

“Man in the loop” strategy:

The Remote Handling system is open to manual control when a high level of human supervision and/or adaptability is required. In more routine tasks, or when there is a need for time optimisation and/or accuracy of motion, the Remote Handling system is operated in an automatic or robotic way.

JET has today the only operating platform within the fusion programme where RH techniques have been developed, tested, and improved to a stage that allows in-vessel works to be carried out fully remotely. Although ITER RH will feature a number of differences from the JET system, the experience gained by the JET RH group over many years will be of great importance for ITER. According to JET’s experience, the RH systems work efficiently when the following aspects are thoroughly considered:

Adaptability: Experimental facilities, such as JET, are subject to changes in their configuration in order to test new components and systems. To cope with the changes, from the beginning JET adopted a generic “man in the loop” RH strategy, which maximised its adaptability to the environment and minimised the need for re-configuration of the equipment from one shutdown to the next. This approach also lends itself well to RH tasks related to unexpected interventions.

Planning: In-vessel maintenance is not limited to component replacement. There are numerous supplementary tasks, e.g. inspection, cleaning, metrology or re-tightening bolts. Many of them require development of specific equipment. Installation of in-vessel services (lights, power lines etc.) should not be underestimated either.

Development: The RH equipment is of one-off nature and it is still vital to predict its reliability. At JET, the reliability was assessed and improved during long-term tests using specially built full scale mock-ups and the general scheme for new RH components is defined by the so-called “life-cycle”. The life-cycle can be divided into four phases: design based on definition of the requirements, first version system, development to maturity and, last, RH operation. This evolution can only be efficient if the R&D work is completed and interfaces between RH and machine are frozen.

Space: Designing tools to be remotely operable means providing them with specific features, which reduce the level of risk in performing the task. A common feature is that these tools require more space than would have been needed for manual tooling. The RH equipment also needs a huge amount of external backup, i.e. space outside the working zone for services, operators, mock-ups, maintenance, decontamination, commissioning etc.

Control: The local JET RH team has been playing an important role in rationalisation of the RH control systems. For example, recent developments of Virtual Reality at JET show that real improvements for RH operations can be achieved by exploiting 3D computer simulations. Virtual Reality is used extensively during RH preparation and final task execution. Nevertheless, real-time camera views remain central to the JET RH strategy in order to cope with unpredictable situations. The successful remote handling of JET has demonstrated the feasibility of remote maintenance for fusion. Many lessons have been learnt of which the JET remote handling team consider the most significant to be the necessity for rigorous preparation and attention to detail in the design, build and testing of the remote handling devices and the JET components.