Hydrogen Isotope Separation by Catalyzed Exchange Between Hydrogen and Liquid Water

Abstract

Abstract The discovery, at Chalk River Nuclear Laboratories, of a simple method of wetproofing platinum catalysts so that they retain their activity in liquid water stimulated a concentrated research program for the development of catalysts for the hydrogen-water isotopic exchange reaction. This paper reviews 10 years of study which have resulted in the development of highly active platinum catalysts which remain effective in water for periods greater than a year. The most efficient way to use these catalysts for the separation of hydrogen isotopes is in a trickle bed reactor which effects a continuous separation. The catalyst is packed in a column with hydrogen and water flowing countercurrently through the bed. The overall isotope transfer rate measured for the exchange reaction is influenced by various parameters, such as hydrogen and water flow rates, temperature, hydrogen pressure, and platinum metal loading. The effect of these parameters as well as the improved performance obtained by diluting the hydrophobic catalyst with inert hydrophilic packing are discussed. The hydrophobic catalysts can be effectively used in a variety of applications of particular interest in the nuclear industry. A Combined Electrolysis Catalytic Exchange - Heavy Water Process (CECE-HWP) is being developed at Chalk River with the ultimate aim of producing parasitic heavy water from electrolytic hydrogen streams. Other more immediate applications include the final enrichment of heavy water and the extraction of tritium from light and heavy water. Pilot plant studies on these latter processes are currently in progress.