Assessment of Fatigue Effects Induced by Fast Beam Transients in the IFMIF-DONES Li Target

One of the crucial steps toward the commercial exploitation of fusion energy is the availability of a high-intensity neutron source able to test and qualify structural materials to be used in future fusion power reactors. The International Fusion Materials Irradiation Facility-DEMO Oriented NEutron Source (IFMIF-DONES) facility, which is currently being designed within the framework of the EUROfusion Consortium, represents the European effort to develop such a neutron source. It employs a liquid lithium target struck by an accelerated deuteron (D+) beam to produce fusion-like neutrons used to irradiate materials samples. So far, a detailed investigation of the thermomechanical behavior of the IFMIF-DONES target system has been accomplished for the case of steady-state operation, considering the D+ beam steadily running at full nominal power (5 MW). However, the study of the effects generated in the lithium and in the surrounding steel structure backplate (BP) during the unavoidable beam trips needs to be carried out as well to exclude the possibility of system failure by fatigue phenomena. To this aim, a numerical assessment of the fatigue damage produced on the BP by repeated thermally induced shock waves propagating in the lithium as a consequence of accelerator fast beam trip events has been carried out following the methodology outlined in the RCC-MRx nuclear design code. In this article, the details of the calculations and the results obtained from such analysis are presented showing the capability of the system to survive for its whole expected lifetime.