A Consideration on Increasing Current Density in Normal Conducting Toroidal Field Coil for Spherical Tokamak Power Plant

The center post is the most critical component as an inboard part of the toroidal field coil for the low aspect ratio tokamak. During the discharge it endures not only a tremendous ohmic heating owing to its carrying a rather high current but also a large nuclear heating and irradiation owing to the plasma operation. All the severe operating conditions, including the structure stress intensity and the stability of the structure, largely limit the maximum allowable current density. But in order to contain a very high dense plasma, it is hoped that the fusion power plant system can operate with a much high maximum magnetic field BT ≥12 T-15 T in the center post. A new method is presented in this paper to improve the maximum magnetic field up to 17 T and to investigate the possibility of the normal conducting center post to be used in the future fusion tokamak power plant.

Feasibility Study on Welding Structure of the HT-7U Toroidal Field Coil Case

The Toroidal Field (TF) coil case of the HT-7U superconducting tokamak device is made of austenitic stainless steel 316LN and is designed to operate at cryogenic temperature (4 K). 316LN can retain high strength and fracture toughness at 4 K. Feasibility study on technical process of welding has been experimentally considered as a hopeful joint method for suppression of post-welding deformation and reduction of over-heating. Meanwhile the final range of stress intensity and the stress intensity factor (K) for pre-cracks of welding structure have been determined by using J-integral. These related results are optimistic and have shown that there's no problem in strength and fracture toughness at the vicinity of the pre-crack tip. This paper introduces the welding structure of TF coil case in detail.

Finite Element Analyses and Instrumentation Layout for Single Coil Testing of TF Coils in HT-7U

The HT-7U tokamak is a magnetically-confined full superconducting fusion device, consisting of superconducting toroidal field (TF) coils and superconducting poloidal field (PF) coils. These coils are wound with cable-in-conductor (CICC) which is based on UNK NbTi wires made in Russian '. A single D-shaped toroidal field magnet coil will be tested for large and expensive magnets systems before assembling them in the toroidal configuration. This paper describes the layout of the instrumentation for a superconducting test facility based on the results of a finite element modeling of the single coil of toroidal magnetic field (TF) coils in HT-7U tokamak device. At the same time, the design of coil support structure in the test facility is particularly discussed in some detail.

Buckling Analysis of TF Coil Inner Leg for Central Solenoidless Tokamak

The central post is one of the critical components for the low aspect ratio tokamak, which endures not only a tremendous ohmic heating because it carries a rather high current, but also a large neutron heating and irradiation owing to the plasma operation. The DS copper alloy Glidcop AL-25[8] was chosen as the conductor material for its adequate mechanical properties and physics properties. The central post has a cylindrical structure with lots of cooling channels. The length of the central post for the next generation of nuclear fusion spherical tokamaks will be more than 10 m or 20 m. The structural stability is very crucial. When the applied load is larger than the structure critical buckling load, the device will lose its stability and collapse. In order to calculate the critical buckling load, a 1/6-segment finite element model was used and the force acting on the central post was simulated. The results showed that the vertical compressive stresses mainly affect the stability of the central post. The linear buckling analysis results with finite element method based on small deformation theory were given in this paper. The relation curves and functions for buckling factor, depending on the different lengths and the radius of the central post, the diameter of cooling channel and the maximum allowable current density, were also shown.