STRESS-ANALYSIS OF POLOIDAL FIELD-COIL SUPPORT IN JT-60U

An iterative non-linear stress analysis considering the thermal expansion and the dynamic effect of the poloidal field coil support in JT-60U tokamak are described. In the JT -60U design, the large electromagnetic forces and smaller space between the toroidal field coil and the vacuum vessel result in a marginal design of the poloidal field coil support structures with small safety margin. Moreover, the complicated geometry of the structure is not easily modeled into the finite elements in the stress analysis and the non-linear friction force applied from the poloidal field coils is difficult to represent realistically. To accurately analyze the deformation and the stress, an iterative method which can treat the friction force as nonlinear force is proposed and applied to the actual design analysis in JT-60U. The deformation calculated from the iterative method is approximately four times of the result in the case of conservative linear friction force. Simple dynamic analysis about the combination of the poloidal field coil, support and the vacuum vessel was carried out to evaluate the dynamic effect with plasma disruption. The results indicated that the serious dynamic resonance can not be expected.