Thermomechanical failure analysis of IFMIF-DONES target under off-nominal extreme conditions

IFMIF-DONES will be a radiological facility for material irradiation replicating conditions expected in future fusion reactors. It will employ a 40 MeV deuteron beam directed at a liquid Li target circulating at 15 m/s to generate high-energy neutrons, depositing 5 MW. The Back-Plate (BP), placed immediately downstream of the Li, separates the vacuum of the accelerator and target chambers from the low-pressure He atmosphere housing the irradiation modules. A critical scenario postulates an eventual loss of liquid Li curtain thickness without shutting down the beam, risking a direct or partial deuteron beam impact on the BP causing large power deposition. This study provides the BP dynamic thermomechanical response, aiming at characterizing the involved timings in the impact-triggered events, such as mechanical failure, melting or vaporization. This is important to evaluate the eventual mobilization of the BP volatilized activated material and the available timings for beam shutdown. The methodology involves Monte-Carlo simulations for power deposition data integrated into a Finite Element model in ANSYS for transient thermal and structural analyses. Results include timings for melting, vaporization, and mechanical response as function of the beam footprint area and the Li jet thickness reduction.