JET data collection on component malfunctions and failures of neutral injectors and power supply systems

The overall objective of this task of JET Fusion Technology Task Force is to develop a fusion specific data collection (i.e. component failure database) with data coming out from operating experiences gained in the Joint European Torus (JET). The activity is related to JET Neutral Beam Injectors and Power Supply systems and, it is the extension of the previous activity, which interested Vacuum and Active Gas Handling systems. Failures and malfunctions occurred in the years of operations, including information on failure modes and, where possible, causes of the failures, have been identified. The whole sets of components, which the failures/malfunctions are related to and their total operating time and total number of cycles performed have been analyzed. Main statistical values, such as failure rates and corresponding standard errors and confidence intervals, associated to the components have been estimated. About one hundred failures were identified since the beginning of operations up to March 2004 for the NBI mechanical components installed in the two NBI boxes. For a NBI Unit of 8 PINIs per Unit, failure rates of 1.7E-4/h of full operating day (16 h/day) and 7.1E-2/h of pulses were estimated, while the failure probability on demand results 7.6E-5/pulse. About 1000 failures and malfunctions were identified in the period January 1997 - May 2003 for the Coil PS systems, while for the NBI PS systems the identified troubles were about 900. Generic malfunctions, such as \u201cAlert Alarm\u201d or \u201cErratic Alarm\u201d and \u201cFailure to preset\u201d the systems to operate, have been differentiated from troubles related to \u201cFailure to operate\u201d or \u201cSpurious operation\u201d of the systems. As well as, failures of low level components (e.g.: circuit breakers, solid state devices, capacitors, Instrumentation and Control devices, etc.) have been identified by the specific failure modes