STRUCTURAL ANALYSES AND INTEGRATED DESIGNOF THE MITICA INJECTOR ASSEMBLY

In the framework of the activities foreseen for PRIMA (Padova Research on Injector Megavolt Accelerated) the MITICA neutral beam injector plays the role of main experiment, aiming to build, operate, test and optimize a full power and full scale prototype of the ITER Heating Neutral Beam Injector. MITICA is a complex system designed to deliver 16.7 MW to the ITER plasma for duration up to 1 hour. It is composed of a vacuum vessel, a 1 MeV ion beam source, three beam line components to neutralize and characterize the beam and two large cryopumps on the two sides of the injector beam line components. The beam source is electrically fed by dedicated 1 MV Power Supplies through high voltage transmission line. The entire MITICA system will be housed in special buildings, suitably designed to provide all the necessary supports, interfaces and shielding walls for nuclear radiation safety. Therefore an integrated design of the MITICA system and relevant buildings shall be developed and verified carefully, considering all the different configurations, operational modes and load combinations. An integrated model of the MITICA assembly including buildings, vessel, HV Bushing (HVB), Transmission Line (TL) and HVB support structure has been developed. The model takes into account properly constraints to ground and surrounding buildings, to study and verify the static and seismic response of the whole assembly. After an overall description of the system and of the main design assumptions, this paper presents the numerical models and the results of MITICA assembly integrated analyses. The modeling choices are described in detail together with all the materials properties and boundary conditions. In particular modeling of three bellows elements included in TL is presented. Assumptions and benchmark analyses for validation are reported, as well. TL supports inside the experiment building, their positions and constrained degrees of freedom are discussed in a dedicated section. The load cases are then defined and the numerical analyses described. Load definition and analyses have been performed considering the requirements of both the American Standard and the National Standard NTC 2008 for the seismic verification of structures subject to design response spectra. The obtained results are finally shown in detail and discussed, also comparing some different design options for design optimization.