A comparison of pulsed and steady-state tokamak reactor burn cycles. Part I: Thermal effects and lifetime limitations

Four distinct operating modes have been proposed for tokamaks, and consequently a variety of thermal environments can be postulated for future reactor subsystems. Our study concentrates on lifetime limitations associated with fluctuating thermal loads on the first wall, limiter or divertor plates, and in the breeding blanket. Simultaneous failure from thermal fatigue, radiation damage, and disruption-induced erosion is considered, and burn length goals are calculated in order to help achieve high availability for a commercial reactor. In addition, the cost of thermal storage is found as a function of the dwell period between burns of a pulsed cycle; thermal storage is shown to be an expensive requirement for pulsed reactors.