An Equilibration Method for Measuring Low-Oxygen Activities in Liquid Sodium

An equilibration method has been developed to measure accurately the activity of oxygen at low concentrations (<20 ppm) in liquid sodium. Vanadium wires are exposed to liquid sodium until the oxygen in solution in vanadium is in equilibrium with the active or free oxygen in sodium. The oxygen concentration in the vanadium detector is then measured by reliable techniques, and this value is related to the oxygen concentration in sodium by the equilibrium distribution coefficient. This method of analysis is specific for oxygen, and contamination problems associated with direct chemical analysis of low-oxygen sodium are eliminated. The accuracy of the method is ±15% in the range 0.5 to 15 ppm oxygen in sodium, and concentrations as low as 0.001 ppm are detectable.