In 1997, the JET device was operated for an extensive campaign with deuterium–tritium (D–T) plasmas (the DTE1 campaign). A comprehensive network of machine protection systems was necessary so that this experimental campaign could be executed safely without damage to the machine or release of activated material. This network had been developed over many years of JET deuterium plasma operation and therefore the modifications for D–T operation was not a significant problem. The DTE1 campaign was executed successfully and safely and the machine protection systems proved reliable and robust and, in the limited cases where they were required to act, functioned correctly. The machine protection systems at JET are described and their categorisation and development over time are summarised. The management, commissioning and operational experience during DTE1 are discussed and some examples of fault scenarios are described. The experience with protection systems at JET highlights the importance of correct design and philosophy decisions being taken at an early stage. It is shown that this experience will be invaluable data input to the safe operation of future large fusion machines.

The remote maintenance of a tokamak type fusion experiment requires a system to satisfy unscheduled repair after failure, scheduled replacement of parts due to consumable depletion or erosion and modification of the tokamak in accordance with experimental requirements. The preparation of remote handling equipment includes the design and manufacture of new equipment, proving of equipment reliability, development and proving of operating procedures, training of operators and setting up an operations support system. The remote handling system is required to be prepared in a time frame dictated by the lead time of the components to be handled. The remote handling philosophy has a direct influence on the design of remote handling equipment, the design of tokamak components, and the remote handling operations. The principle of component handling using teleoperation is characterised as the man-in-the-loop. The handling task is performed by an operator using a manipulator which provides force, and visual and audio feedback of sufficient resolution to create the atmosphere for the operator of actually being in the task environment.

The First Tritium Experiment (FIE) on JET (ref. 1) used Neutral Beam Injection (NBI) not only to heat the plasma using 14 beams of energetic deuterium, but also to supply the tritium via the remaining two injectors which were specially modified for this purpose. This represents a significant advance in the technology of NBI and in this paper we describe the Tritium Gas Introduction System (TGIS), which was an essential feature of this development.