Availability of the EU-DEMO Electron Cyclotron Heating Transmission Line and Launcher Systems by Fault Tree and Reliability Block Diagram Analyses

European DEMOnstration (EU-DEMO) fusion reactor is currently progressing through its conceptual design phase. Reliability assessments play a key role in demonstrating that the system architecture can fulfill its intended functions over a defined lifespan. In the current approach, availability assessments begin with a failure mode and effects analysis (FMEA) to systematically identify potential failure events affecting system performance. Fault tree (FT) models are developed for subsystems exhibiting multiple failure modes, while the overall system configuration is modeled using a reliability block diagram (RBD). This study focuses on the electron cyclotron (EC) heating system, which supports plasma heating during ramp-up and ramp-down phases, stabilizes neoclassical tearing modes, and mitigates radiative instabilities. The analysis targets the current design of the transmission line (TL) and launcher subsystems, excluding gyrotrons from the current scope. Availability simulations have been performed over a 20-year operational period. Parametric analyses are also conducted to quantify the sensitivity of availability to maintenance duration and restoration parameters, providing key insights into design robustness and operational planning.