Kinetic study of sodium-water surface reaction by differential thermal analysis

Kikuchi, Shin  ; Seino, Hiroshi ; Kurihara, Akikazu ; Ohshima, Hiroyuki

For the purpose of elucidating the mechanism of the sodium-water surface reaction in a steam generator of sodium-cooled fast reactors, kinetic study of the sodium (Na)-sodium hydroxide (NaOH) reaction has been carried out by using Differential Thermal Analysis (DTA) technique. The parameters, including melting points of Na and NaOH, phase transition temperature of NaOH, Na-NaOH reaction temperature, and decomposition temperature of sodiumhydride (NaH) have been identified from DTA curves. Na, NaOH and NaO as major chemicalspecies were identified from the X-ray diffraction (XRD) analysis of the residues after the DTA experiment. It was inferred that NaO could be generated as a reaction product. Based on the measured reaction temperature, the rate constant of sodium monoxide (NaO) generation was obtained by the application of the laws of chemical kinetics. From the estimated rate constant, it was confirmed that NaO generation should be considered during the sodium-water reaction.