Since
tritium resources are very limited, economical conversion of fusion energy to electricity and/or heat must have an enough margin to keep self-fuel-sufficiency and simultaneously ensure
tritium safety. To realize this,
tritium inventory in reactor
systems, which use ¡«10
17 Bq (a few kg) of
tritium, should be kept as small as possible, under strict
accountancy or regulation of a few tens Bq (¡«pg). In present tokamaks, however, hydrogen retention rate is significantly large, i.e. more than 5 % of fueled hydrogen is continuously piled up in their vacuum vessels, which must not be allowed in a reactor. Moreover, both fuelling and burning efficiencies are very poor, only a few % or less. Accordingly, huge amount of
tritium fuel must be recycled.
In the paper, after the introduction of tritium as a hydrogen radioisotope, important issues to establish safe and economical tritium fuel cycle for a fusion reactor will be summarized considering the handling of large amounts of tritium, i.e. confinement, leakage, contamination, permeation, regulation and tritium accountancy.
