Optimization of oxygen and hydrogen analysis in salts by inert gas fusion

The presence of hydrogen and oxygen in molten salts can result in corrosion of structural materials, thus it is important to quantify these impurity levels to ensure degradation remains within design limits. No current standards are available for measuring oxygen and hydrogen content in metallic halide salts. Inert gas fusion (IGF) is recognized to be an effective way to measure bulk concentrations of oxygen and hydrogen in salt samples. However, analysis results are sensitive to sample preparation and measurement parameters.

This study investigates the influence of variances in sample weight, sample form, grinding preparation, capsule type, and analysis temperature on the measurement results. Accuracy and precision of sample preparation and analysis methods were verified for both hydrogen and oxygen by spiking sodium fluoride, respectively, with cesium bicarbonate and uranium dioxide. As-received sodium fluoride and an in-house prepared fuel salt mixture (uranium tetrafluoride, potassium fluoride, and sodium fluoride) were used for interlabratory round robin studies to validate sample preparation and analysis methods for IGF analysis of salts. Sample preparation for both oxygen and hydrogen analysis were determined to be analogous with one another. Analysis temperature directly effected the measurement results by influencing the selective formation and release of analyte products, along with the efficiency of fusion at high temperatures.

Data presented within this work lay the foundation to develop a standardized method for analysis of light element impurities (oxygen and hydrogen) by IGF within salts.