Optimization of tritium inventory in an isotope separation system based on Aspen Plus

The Isotope Separation System (ISS) is employed to separate unburned hydrogen isotopes and tritium from fusion devices. A key design requirement is to control the tritium holdup within the system, thereby reducing the amount of tritium fuel that must be supplied for device operation and ensuring the feasibility of tritium fuel self-sufficiency. In this study, a steady-state process model for the Internal Isotope Separation System (I-ISS) was developed using Aspen Plus software. This model was employed to estimate the tritium holdup within the distillation columns. Subsequently, an optimization analysis was conducted using the Sequential Quadratic Programming (SQP) method, with the total as the objective function. By optimizing key operational parameters such as the reflux ratio and the distillate-to-feed ratio of the columns, the total tritium holdup of the I-ISS was successfully reduced from 100.155 mol to 38.969 mol, representing a reduction of 61%. Furthermore, the effects of feed gas flow rate, composition from the Tokamak exhaust processing system, and product purity on the system's tritium holdup were investigated. The results indicate that an increase in the feed flow rate, an increase in product tritium purity, and a decrease in hydrogen content lead to an increase in tritium holdup within the system. Through process simulation and optimization, this study provides an optimized pathway for achieving system-level tritium holdup minimization in the ISS, offering crucial quantitative references for the fuel cycle design and tritium inventory assessment of future fusion device tritium plants.