On the Electrolytic Separation Factor of Tritium

Abstract

The electrolytic enrichment process of tritium is in current use for the measurement of its content in natural water. The electrolytic separation factor of tritium which can have experimental values ranging from 4 to 30 is affected by the nature of the cathode, by the electric current density, and by the nature of the electrolyte. It was recently shown that the factor took a value within a limited range when an alkaline solution was electrolyzed by the use of a nickel-cathode cell under a current density around 50 mA/cm².
To re-examine the reproducibility of the separation factor of tritium, the electrolytic enrichment experiment was made using nickel-nickel electrode cells, 0.05 N-alkaline solutions, and a current density of 50 mA/cm². The observed separation factors were within the range previously reported on nickel-cathode cells. The results, after they were corrected for the carryover of water vapor and spray droplets, were close to the thermodynamic equilibrium constants for the protium-tritium exchange reaction between liquid water and hydrogen gas at several solution temperatures in the cell ranging from 12°C to 33°C. The equilibrium conditions would be expected to prevail and to make the factor reproducible, so far as the above conditions were used.
At the current densities above 50 mA/cm² up to 100 mA/cm², on the other hand, the factors obtained in this work were slightly more than that corresponding to equilibrium, and had a tendancy to rise with increase of current density. It is considered that slow exchange by rate process are apt to take place partly at the cathode surface under the condition of such high current strength.