Tritium Breeding Ratio Required to Keep Tritium Balance in a D-T Fusion Reactor

The way to estimate the tritium breeding ratio in a D-T fusion power reactor to assure a self-sustainable tritium system is discussed in this paper comparing the required breeding ratio obtained from tritium balance in the fueling system of a power reactor including the plasma vessel with the attainable breeding ratio evaluated from efficiency in neutron usage and recovery efficiency of bred tritium in the blanket system. It is certified that recovery of tritium from the re-deposition layer together with suppression of the permeation loss through first wall and reduction of the total tritium inventory are effective to ease the tritium balance. It is not preferable to have the burning plasma of which overall burning efficiency is less than 0.5% from the viewpoint of tritium balance of a power reactor.