Numerical Analysis of Tritium Transport Characteristics in Fluoride-salt-cooled High-temperature Reactor

Tritium control is one of the most critical issues which limit the development of fluoride-salt-cooled high-temperature reactor (FHR). In order to control tritium effectively, the transport characteristics of tritium in fluoride salt must be known. In this paper, the transport characteristics of tritium in the primary loop of FHRs were expounded, including tritium production and speciation, the absorption and desorption by graphite, dissolution and diffusion in molten salt and permeation through structural materials. A series of reasonable mathematical and physical models were established for tritium transport characteristics analysis of TFHR and the TAPAS code for FHRs was developed based on FORTRAN code. The preliminary verification of the code was conducted by comparing calculation results with experiment data, and the results prove the fidelity and accuracy of TAPAS. The tritium transport characteristics in TFHR were analyzed by TAPAS. The initial tritium production rate of TFHR is 5.54×10^-8 mol/s. Tritium in the primary coolant loop is mainly in the form of T₂. The corrosion reactions always occur at the entrance of hot legs. After 25 EFPD operation, tritium absorption by graphite attends its limiting value. When the reactor operates at steady state, the permeation rate of T₂ can be regarded as a constant, which is 8.35 μmol/EFPD. This study can contribute to the design and radiation protection of FHR.