Transient analysis of tritium transport characteristics in fluoride-salt-cooled high-temperature reactor

Tritium control is a challenging issue for the commercialization of Fluoride-salt-cooled High-temperature Reactor (FHR). In this paper, the tritium behaviors in a FHR system are briefly introduced. A tritium transport characteristics analysis code (the updated TAPAS code)is developed and validated to research the dynamic responses of tritium behaviors during reactor accidents. Two typical accidents for the FHR are simulated, including unprotected reactivity insertion accident (URIA)and unprotected overcooling (UOC)accident. Numerical results show that tritium transport characteristics are strongly coupled under transient conditions; they are quite different from those of normal operation, ranging from tritium production and speciation, adsorption by graphite, chromium corrosion and deposition to tritium permeation through structural materials. The results are discussed in detail in comparison with our previous study. Based on current calculation models, the T₂ permeation rate decreases under the URIA and UOC, therefore, extra safety facilities for tritium control under these two transient conditions are not necessary. This study may provide a valuable reference for the tritium control in the FHR.