Capsule Test for Investigating the Sodium-Carbon Dioxide Interaction

The utilization of modular sodium-to-supercritical CO2 heat exchangers may yield significant improvements for an overall plant energy utilization. The consequences of a failure of the sodium CO2 heat exchanger boundary, however, would involve the blowdown and intermixing of high-pressure CO2 in a sodium pool, causing a pressurization which may threaten the structural integrity of the heat exchanger. Available data seems to indicate that the chemical reaction between sodium and CO2 would likely produce sodium oxides, sodium carbonate, carbon and carbon monoxide. Information on the kinetics of the sodium/CO2 reaction is virtually nonexistent. A small-scale capsule test has been conducted at KAERI to explore the basic nature and extent of the sodium-CO2 chemical reaction, for a preliminary assessment of the pressurization issue. The experimental study was carried out by using an experimental apparatus for about 30 g of sodium. A number of experiments were carried out with the sodium temperature ranging from 200 deg C up to 600 deg C, with an operating pressure of up to 40 kg/cm2. The results show that the carbon dioxide reacted readily with the liquid sodium under the experimental conditions. It seems that the interaction reaction of Na-CO2 was slow at 200oC and became faster above 300 deg C. The reaction phenomena of 300 deg C and 400 deg C were similar. At 600 deg C the reaction of Na-CO2 occurred very rapidly. (authors)