Study of Fueling Scenario and Particle Balance in a Fusion Reactor

A fueling scenario in a fusion reactor has been investigated, where tritium is fueled in the main plasma and deuterium is fueled in both the main plasma and the edge plasma. The tritium fueling in the main plasma minimizes the tritium fueling rate necessary for sustaining the high tritium density in the main plasma, resulting in the minimum tritium recycling level at the fixed pumping fraction. The deuterium fueling in the main plasma sustains the high deuterium density in the main plasma, and the deuterium fueling in the edge plasma enhances the deuterium recycling level for reducing the divertor temperature. Based on this scenario, particle balance was quantitatively investigated using the SlimCS design parameters at 2.95-GW fusion output with consideration of confinement times separately estimated for the particles fueled in the main plasma and the edge plasma. The fueling rates in the main plasma were evaluated to be 2.5 × 1022/s for tritium and 1.4 × 1022/s for deuterium when the confinement times for the particles fueled in the main and edge plasmas were assumed to be 2 s and 2 ms, respectively, and the divertor pumping fraction was assumed to be 3% of the particle flux to the divertor plates. For enhancement of the recycling level, the additional deuterium fueling in the edge plasma of 3.6 × 1023/s was required in this case. In order to satisfy the tritium balance, it was necessary to suppress the tritium retention rate to <0.01% of the tritium recycling rate and the tritium loss in the tritium cycle system to below 0.2% of the tritium fueling rate with the tritium breeding ratio of 1.05.