Speaker
Description
IFMIF-DONES is a radiological facility designed to irradiate material samples under irradiation conditions similar to those expected in future fusion reactors. For this purpose, high energy neutrons are produced by an intense 40 MeV deuteron accelerator directed towards a target made of a 25 mm thickness liquid Li curtain circulating at 25 m/s, depositing a nominal power of 5 MW which is evacuated with the Li. The Back-Plate is the part of the Target Vacuum Chamber placed just downstream the Li, separating the vacuum of the accelerator and target chambers and the low-pressure He atmosphere in the Test Cell, where the irradiation modules with the materials specimens will be placed. In this context, one of the most critical accident scenarios postulates an eventual loss of liquid lithium curtain thickness without shutting down the beam, leading to a direct or partial deuteron beam impact on the Back-Plate with the consequent large power deposition into it. The present work provides a dynamic thermomechanical study of the Back-Plate response in this event, aiming at characterizing the involved timings in the impact-triggered events, such as mechanical failure due to thermal stresses, melting or vaporization. This is important to evaluate the eventual mobilisation of the Back-Plate volatilized activated material through the accelerator vacuum chambers and the available timings for both active Safety Beam Shutdown or even a "passive" shutdown due to vacuum loss in the chambers. The methodology consists in obtaining power deposition data by means of Monte-Carlo simulations (SRIM) and loading them into a Finite Element model of the Back-Plate in ANSYS to perform transient thermal and structural analyses. The results include a set of timings for melting, vaporization, and mechanical failure as function of the beam footprint area and the lithium curtain thickness reduction.
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