Quantitative evaluation of fatigue impact on CS and TF coils in pulsed tokamak power plant

Fatigue issue of a pulsed operation tokamak is studied for the major radii R_p = 10 m, 11m and 12m in this paper. By study of central solenoid coil (CS) fatigue, it is clarified that pulse cycle number of the reference of 10m throughout 30-year operation period is about 50,000 and its allowable stress amplitude for CS fatigue is about 300MPa. This constraint has actually no impact on the CS designs of the reference tokamaks. Allowable length of toroidal field coil (TFC) maintenance port of the reference 10m tokamak is calculated to be 13.3 m, which is corresponding to 92% of TFC height. Also the minimum width of each cryostat post which supports the overturning force of TFC is found to be 2.3m to prevent its fracture. This result indicates that fatigue may have impact on rather outer support structure of TFC than TFC itself. This construction cost for strengthening cryostat post could reach a few of hundreds million dollars according to a rough calculation.