Tritium removal from liquid metals by sorption on yttrium

Molten lithium appears to be the most promising blanket material for breeding tritium in fusion reactors. One of the more promising techniques for recovering tritium from liquid lithium involves sorption on a hydrogen-gettering metal. Tritium sorption from molten lithium and potassium has been studied in a batch contactor at temperatures of 300 and 4000C using metal sorbent samples of yttrium and zirconium. Yttrium has shown significant removal rates from both molten lithium and potassium. The data indicate that sorption by yttrium is a feasible method for the recovery of tritium from molten lithium. Sorption rates from potassium (potential coolant material), however, do not appear to be sufficiently high for a practical recovery process. Tritium-sorption rates from lithium (833 +- 54 ppb tritium) were considerably higher than those from potassium. Twenty-one sorption runs were made at 3000C using the same yttrium sample (3.45 g, 13.1 cm2). The tritium concentration in the lithium decreased with time as if there were two first-order processes. The reaction half-time increased from 24 min (for the first half hour of contact time) to 20 hr (for contact times > 2 hr). Runs with contact time of less than or equal to 30 min were used to obtain a mass transfer coefficient of 6 x 10-4 cm/sec. The driving force was assumed to be the tritium concentration in the lithium; the ratio of the lithium; the ratio of the yttrium surface area to lithium volume was 0.82 +- 0.02 cm-1. The controlling mass transfer resistance appears to be the liquid lithium phase. The mass transfer rate could then be increased significantly with forced convection. During the sorption experiments, the estimated accumulation of tritium in the yttrium was 0.78 Ci, and the tritium recovered after dissolution of the yttrium sample was 0.90 Ci