The relationships between fueling (gas injection and pellets of various sizes and velocities), pumping in the divertor chamber (constrained by fuel processing and divertor design), core density (constrained by the desired fusion power and helium ash accumulation), separatrix density (constrained by divertor operation and density limits) and plasma confinement models are examined for the International Engineering Tokamak Reactor (ITER) Engineering Design Activity (EDA) for guidance in the definition of design requirements for the pumping and fueling systems. Various combinations of gas and pellet injection are found to meet the constraints for operation at 1500 MW of fusion power and 1 bar·l/s (5.3 × 1022 atoms/s) of DT pumping. Very low pumping reduces fuel processing requirements, but can lead to excessive helium accumulation depending on the particle transport properties. Isotopic tailoring of the fuel sources, e.g., 20–30% of the input fuel stream as tritium pellets and the rest as deuterium gas, can maintain the core fuel species mixture in the optimum range for fusion production (at least a 40–60 mixture) while reducing the tritium concentration in the edge region to 20–30%. This should reduce the tritium inventory in the plasma facing components, since that is typically governed by the fuel density mix near the plasma edge. A high density, low temperature ignited regime supported by deep pellet injection is shown to exist under some low confinement conditions.
