Data collection on component malfunctions and failures of JET ICRH system

Abstract

The paper presents the collection and the analyse of data coming out from operating experiences gained in the Joint European Torus (JET) for the Ion Cyclotron Resonance Heating (ICRH) system. The main goal of the activity is to enrich the data collection on failures of components used in fusion facilities. Alarms/failures and malfunctions occurred in the years of operations from March 1996 to November 2005, including information on failure modes and, where possible, causes of the failures, have been identified. About 3400 events classified as alarms or failures related to specific components or sub-systems were identified by analysing hand-written logbooks made available by the ICRH operation staff. By analysing the tick sheets covering the whole considered time interval it results that the ICRH was operated during about 12,000 plasma pulses. Main statistical values, such as rates of alarms/failures and corresponding standard errors and confidence intervals, have been estimated. Failure rates of systems and components have been evaluated both with regard to the ICRH operation pulses and operating days (in which at least one ICRH module was requested to operate). Failure probabilities on demand have been evaluated with regard to number of pulses operated.