Optimization study on the normal conducting center post for the low aspect ratio tokamak reactor

The center post is the most critical component as an inboard part of the toroidal field (TF) coil for the low aspect ratio tokamak power plants. During the employment it will endure not only a tremendous ohmic heating due to its carrying a rather high current but also a large neutron heating and irradiation owing to the plasma operation. All of the severe operating conditions have brought about lots of challenges for the design of the center post. This paper presents detailed optimization results and design windows for the engineering design of normal conducting (NC) center post based on the analysis of thermal-hydraulic, static stress and critical buckling. At the same time a method to reduce the stress in the center post have been proposed, which can be applied to enhance the possibility of normal conducting center post in the future power plants. The optimization results have indicated that the maximum allowable current density for the 10 m-length, 0.65 m-radius and 20%-water fraction center post can reach 45.5 A/mm2 if only considered the thermal hydraulic conditions. When all the limiting conditions including the thermal hydraulic performance and static stress are taken into account the maximum allowable current density will be down to 21 A/mm2. But if the method of improvement for reducing the stress is applied in the system of the center post, the maximum allowable current density will be able to increase to 37 A/mm2 and the corresponding maximum magnet field can be improved from 8.6 to 15 T.