First wall energy deposition during vertical displacement events on ITER

The beryllium (Be) first wall energy deposition and melt damage profiles resulting from the current quench phase of an unmitigated, 5 MA/1.8 T upward vertical displacement event for ITER are investigated. Time dependent 2D magnetic flux profiles are calculated with the DINA code and used as input for the SMITER 3D field line tracing software. 3D maps of the wetted area and perpendicular heat flux $q_{\perp }$ show that the majority of the energy deposition occurs on the upper first wall panels #8 and #9. SMITER simulations predict $q_{\perp ,peak}\approx 190MW{m}^{-2}$ on the surfaces of upper FWPs #8 and #9 at the end of the ∼450 ms current quench. The surface heat flux maps generated by SMITER are used as input in the MEMOS-U code, which models Be melt formation and dynamics. Simulations reveal peak surface temperatures of ∼2200 K, inward surface damage of ∼0.5 mm in depth, and average melt velocities of ∼2 m s⁻¹. Although VDEs are in principle the easiest disruptive instability to avoid, the analysis demonstrates that any non-mitigated events or intentional VDEs taking place during low I_p, early operational phases of ITER for the purposes of estimating disruption forces, must be kept to a low number. (topical issue article)