Tritium Analysis for the US-ITER Solid Breeder Blanket

This paper presents an analysis of the tritium release and inventory in the US-ITER solid breeder blanket, based on the MISTRAL code. Since the effect of LiOT formation and precipitation at low temperature can be quite important in Li₂O, the selected solid breeder for the blanket, these processes have to be accounted for in the calculations. A simple way of estimating the LiOT precipitation as a function of temperature and moisture partial pressure was added to MISTRAL by including the calculations of T₂O, H₂O and HTO concentrations in the pore, in addition to T₂, H₂ and HT. The analysis was carried out for both steady state and transient cases. The transient cases are based on the given burn and dwell times during the Physics and Technology Phases and the corresponding temperature profile and tritium generation history in the solid breeder region. For the steady state case, a tradeoff analysis is done for the helium purge flow rate, based on an acceptable tritium inventory which imposes a lower limit on the purge flow rate and an acceptable purge pressure drop which imposes a higher limit on the purge flow rate.