Abstract: Ethanolamine (ETA) has been selected as the pH control agent for the secondary loop in the third generation nuclear power plant. However, the research on ETA gas-liquid partition coefficient and high-temperature degradation is not comprehensive enough to satisfy the application requirements of various parameters in nuclear power plant. In this paper, the working pressure and temperature of the secondary loop of nuclear power plant are simulated by high-pressure autoclave. The gas and liquid samples are obtained by special sampling device. The relative volatility, thermal decomposition rate and total organic carbon (TOC) content of samples at different temperatures are studied by ion chromatography and TOC analysis methods. The calculating formula for the molar ratio of total alkali in gas phase to total alkali in liquid phase is proposed to evaluate the distribution of gas-liquid alkalinity. It is indicated that the lower distribution coefficient of ETA is beneficial to the pH balance of the secondary loop. ETA exhibits good thermal stability under the oxygen-free condition, with the thermal decomposition rate less than 1%/h even at 300℃. But the thermal degradation rate of ETA increases in the presence of oxygen, with higher concentration of ammonia ion and lower content of formic acid, acetic acid and glycolic acid in the decomposition product. The experimental results can provide the reference for the chemical control of cycle water chemistry in nuclear power plant.

Key words: ethanolamine, gas-liquid partition coefficient, relative volatility, thermal decomposition, nuclear power plant, second recirculation loop