Study on tritium production using a high-temperature gas-cooled reactor for fusion reactors: Evaluation of tritium outflow by non-equilibrium diffusion simulations

Performance of tritium production for fusion reactors, using a high-temperature gas-cooled reactor (HTGR) is examined. From the viewpoints of tritium recovery and environmental safety, tritium outflow from Li rods should be suppressed to the same level as the liquid radioactive waste from the pressurized water reactors (PWRs) in Japan. Methods for suppressing tritium leakage from Li rods are studied. The tritium outflow is reevaluated accurately on the basis of non-equilibrium simulations and the influence of coolant temperature on tritium leakage is clarified. The approach using Zr in the Li rod to reduce the tritium pressure and the resulting suppression of tritium leakage are also investigated. The results of the non-equilibrium simulation show that the tritium outflow is approximately 40% lower than the outflow reported in a previous study. Although the electric power generation efficiency is reduced, lowering the coolant temperature to 600 K results in a reduction of the tritium outflow to ∼1/30 compared to the outflow in the case of a coolant temperature of 800 K. The incorporation of Zr into the Li rod can suppress tritium outflow (to ∼1/200 compared to the case without Zr) to below the outflow level in PWRs in Japan.