Vertical displacement events analysis using MAXFEA code in combination with ANSYS APDL in the final design stage of the DTT vacuum vessel

In the context of the Divertor Tokamak Test facility (DTT) project, a recently developed procedure based on the use of MAXFEA code in combination with ANSYS APDL already presented in [1] has been applied to study the EM and structural response of the DTT vacuum vessel (VV) during plasma Vertical Displacement Events (VDEs). From this study, it has emerged that the vacuum vessel mechanical response is acceptable in all of the scenarios but, during a particular event, namely the down-ward VDE slow scenario, a localized stress concentration in the lower side of the vacuum vessel has emerged. Downstream this analysis, mechanical reinforcements in this zone have been introduced in order to optimize the design. The aim of the paper is to show the successful application of this procedure in this context and its reliability as supporting tool in the final stage optimization design of these kind of components. The abovementioned down-ward VDE slow scenario is reported, showing a vertical force peak of around -10MN as the result of the combination of eddy and halo currents during the Current Quench (CQ). The structural analysis highlights that the EM loads occurring at this time instant produce a stress concentration localized in correspondence of the connection of the pedestal with the VV outer shell. This stress concentration has suggested to reinforce this zone in order to optimize the vacuum vessel design.