乙醇胺汽液分配系数及高温分解特性的试验研究

中国第三代核电选定乙醇胺（ETA）作为二回路碱化剂，但目前有关ETA汽液分配系数、高温分解特性研究不够全面，难以满足各种参数核电站的应用需求。采用高压釜模拟核电站二回路的工作压力与温度，采用特制取样装置得到了试验中汽、液两相样品，利用离子色谱、总有机碳（TOC）分析等手段研究了汽、液两相样品在不同温度下相对挥发度、热分解率及TOC含量；同时提出汽相总碱与液相总碱浓度比计算公式，用以评价汽液两相碱化剂的分布状况。研究结果表明：ETA汽液分配系数低，有利于提高二回路系统液相的pH值。在无氧条件下ETA的热稳定性好，即使300℃下热分解率也不超过1.0%/h；但含氧会加速ETA分解，其分解产物中存在较高质量浓度的铵根和较低质量浓度的甲酸、乙酸和乙醇酸。所得试验数据可以作为核电站二回路水化学控制参考依据。

Experimental Study on Gas-Liquid Partition Coefficient and Thermal Decomposition Characteristics of Ethanolamine in High-Temperature Aqueous Systems

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.