RAMI Analysis for PFCs of EAST Divertor

Experimental advanced superconducting tokamak (EAST) is a D-shaped full superconducting tokamak device. Plasma-facing components (PFCs) of EAST lower divertor are most likely to be damaged during the operation, which become fail easily and have to be replaced and repaired frequently. To evaluate whether the divertor is able to reach the design objective, an assessment of technical risks by means of reliability, availability, maintainability, and inspectability (RAMI) for PFCs of EAST lower divertor has to be performed. A functional analysis is carried out in a bottom–up approach, which is described using the IDEFØ methodology. Based on the functional analysis, a failure mode, effect, and criticality analysis is performed to evaluate potential causes of failures and their effects. Criticality charts highlight the risk levels of different failure modes with regard to the probability of their occurrence and the impact on the operation, and actions are taken to mitigate the major risks. According to reliability block diagrams, the availability and the reliability of functions are calculated under stipulated operating condition. The RAMI analysis results provide the reference for the coming upgrade of EAST lower divertor and will be further optimized as the upgrade of the lower divertor.