RAMI analysis of the collective Thomson scattering system front-end – Part1 – Failure modes effects and criticality analysis

ITER is a tokamak nuclear fusion reactor intended to demonstrate the feasibility of nuclear fusion as a carbon-free energy source. In order to control potential technical risks, ITER subsystems are assessed through Reliability, Availability, Maintainability and Inspectability (RAMI) analysis, which includes Failure Modes Effects and Criticality Analysis (FMECA). This paper deals with the FMECA of the front-end components of the Collective Thomson Scattering (CTS) diagnostic, which involves a top-down functional breakdown of the system, identification of critical components and potential failure modes, their effects and consequences for the system. Furthermore, the FMECA methodology allows for the analysis of possible mitigation actions, which may reduce failure mode risk levels. The FMECA was performed in two stages, one concerning the failure modes of the CTS itself, and one concerning the failure modes, which may interrupt ITER operations. Results indicate that there are no failure modes that pose a significant risk to ITER operations. However, mitigation actions were required in order to reduce the risk levels of failure modes, which may compromise CTS diagnostics availability. This article covers the first half of the RAMI analysis of the CTS diagnostic, the FMECA.