Measurement of hydrogen absorption in flowing liquid lithium in the flowing lithium retention experiment (FLIRE)

Flowing metal plasma facing components (PFCs) have the ability to withstand the extreme conditions of future tokamaks. The FLIRE facility at the University of Illinois measures the retention properties, both for helium (ash pumping) and hydrogen (recycling regime, tritium inventory), of candidate liquid PFCs, such as lithium. Results of hydrogen absorption measurements in flowing liquid lithium are presented. Absorption experiments with a flowing lithium stream passing through a low-pressure neutral deuterium gas show 0.1-0.2% D concentration retained long-term in the sample. A similar experiment with a high deuterium pressure of approximately 1 Torr shows the same long-term deuterium retention. These values indicate that the deuterium absorption rate is limited by the dissociation rate of the molecular deuterium gas on the Li surface.