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IFMIF - DONES

The implementation of the nuclear fusion as power source requires the development of materials able to withstand the aggressive environment of the reaction chambers. High neutron fluences of energetic neutrons, photons and implantation of ions will produce a unique combination of events with challenging manifestation at macroscopic level. Erosion of the first wall, embrittlement and cracking of structural materials, and coloring and darkening of optical elements are the most obvious consequences. The radiation source with the features to advance in the field was conceived in the IFMIF project.

IFMIF is a lineal accelerator of deuterons to 40 MeV with two lines impacting in a lithium target with a current of XX d/s. The result is a source of 14 MeV neutrons with an intensity of XX n.s, and a fluence level of XX n expected. The radiological implications of such accelerator are paramount. One the one hand, the accelerator will present losses of deuterons along the line, which will produce neutrons after impacting with the vacuum pipe, magnets, scrappers and other components of the accelerator. On the other hand, the goal of the facility is the neutron production in the test cell. And finally, the deuterons beam must be stopped after the target using a beam dump specially conceived. It also leads to a significant neutron source. These three sources of neutrons produce a cascade of challenging phenomena.

The neutrons produce prompt photons, and the combined fields of neutrons and prompt photons must be shielded to protect the workers and the environment as the facility operates. This impacts noticeably the accelerator bunker. At the same time, the neutrons induce the activation of the air and the materials. Ventilation system design must consider this effect, as well as the in-situ maintenance activities. The design of the accelerator and the facility is affected by these considerations to minimize exposures. The beam dump must be designed carefully, as it receives a large nuclear heat load.