Extruder system for high-throughput/steady-state hydrogen ice supply and application for pellet fueling of reactor-scale fusion experiments

Abstract

Pellet injection systems for the next-generation fusion devices, such as the proposed International Thermonuclear Experimental Reactor (ITER), will require feed systems capable of providing a continuous supply of hydrogen ice at high throughputs. A straightforward concept in which multiple extruder units operate in tandem has been under development at the Oak Ridge National Laboratory. A prototype with three large-volume extruder units has been fabricated and tested in the laboratory. In experiments, it was found that each extruder could provide volumetric ice flow rates of up to ∼1.3 cm3/s (for ∼10 s), which is sufficient for fueling fusion reactors at the gigawatt power level. With the three extruders of the prototype operating in sequence, a steady rate of ∼0.33 cm3/s was maintained for a duration of 1 h. Even steady-state rates approaching the full ITER design value (∼1 cm3/s) may be feasible with the prototype. However, additional extruder units (1–3) would facilitate operations at the higher throughputs and reduce the duty cycle of each unit. The prototype can easily accommodate steady-state pellet fueling of present large tokamaks or other near-term plasma experiments.