Experimental study of sodium/carbon dioxide reaction

Supercritical carbon dioxide (CO2) is being investigated as a material for a secondary cooling system of sodium (Na)-cooled fast reactor to avoid Na/water reaction. In this type of reactor, however, it is necessary to consider the consequences of Na/CO2 reaction, which might occur in the case of tube rupture in a heat exchanger between primary and secondary systems. Experiments were carried out with test equipment for the Na/CO2 reaction, which can handle 1-5 g order of Na and measure temperatures using thermocouples. The solid products of the Na/CO2 reaction sampled from the equipment were analyzed by X-ray diffraction (XRD) and chemical analysis. The parts of exhaust gases were analyzed by gas chromatography. From these experimental results, we proved that the reaction proceeded between liquid Na and CO2. The Na/CO2 reaction stopped only the pool surface reaction with a small quantity of aerosol emission when the initial temperature of Na was lower than 570degC. On the other hand, the reaction continuously proceeded with an orange-cooled flame and aerosol release when the Na initial temperature was higher than 580degC, and the reaction products expanded to the margin of the Na pool tray. (author)