Dynamic analysis of the COMPASS-U tokamak for the design of foundation

Abstract

The COMPASS-U tokamak is currently at the final design stage. In order to design safe and reliable foundation slab for the machine, a dynamic analysis of the deformations and stresses during the most severe plasma disruptions was necessary. A global FEM model has been built including simplified geometry of the entire tokamak as well as the foundation slab and its supporting concrete pillars and the surrounding soil. Vertical forces from the worst-case axisymmetric plasma disruption scenarios were applied to the vacuum vessel and the coil system (CS, PF, TF), causing vibration of the entire tokamak. The deformations and stresses transmitted to the anchors in the reinforced concrete slab were computed. Based on the presented model, the initial thickness of the concrete slab of 1 m was decreased by 20% - to 0.8 m for the final design. Maximum tensile stress of 1.71 MPa was found in the brittle concrete, indicating that no cracking will occur during the worst-case axisymmetric disruptions. Motion of the vacuum vessel due to vertical forces was analyzed, showing maximum deformations below 1.13 mm over the course of the worst disruption. Velocities below 0.29 m/s and accelerations below 287 m/s2. The computational cost was analyzed in details, providing estimates for the computational time, RAM requirements of 25.8 GB/MDOF (77.4 GB/Mnode) and hard disc requirements for the results file of 0.5 GB/MDOF (1.5 GB/Mnode) for each transient time step.