Overview of the JET operation reliability

The JET tokamak has been in operation since 1983. Information on every shutdown, commissioning phase and experimental campaign has been logged electronically since the year 2000, a model for RAMI analyses in fusion experiments. The JET operation reliability statistics record the time taken to install major upgrades, commission systems with plasma, the downtime for maintenance and the achieved experimental campaign days. On average, JET achieves 82% of the planned experimental days during a calendar year. For unplanned interventions the systems that failed are identified together with the impact on machine availability. A total of 14 unplanned interventions are recorded over 19 years with durations of up to 8 weeks. During experimental campaigns, delays from essential subsystems are recorded; computer systems, power supplies, neutral beam systems and delays attributed to human operators. On average 21% of the time is lost due to delays during operations. From the operation reliability data, refurbishments and maintenance are planned at JET to prepare for the upcoming campaigns using deuterium-tritium mixtures.