某核电机组凝结水溶解氧超标问题分析及试验研究

Analysis and Experimental Study of the Problem That the Dissolved Oxygen Content of Condensate Water in a Nuclear Power Unit Exceeds the Standard

结合核电机组的运行特点与溶解氧存在机理,对某核电机组凝结水溶解氧超标问题进行系统性分析和试验研究。着手从漏气量检查、凝汽器性能确认、真空泵抽气能力等3方面进行了分析,研究发现漏气量应参照ASME PTC12.2的规定控制,核电机组凝汽器过冷度对凝结水溶解氧的影响约为理论计算值的1/5-1/3,通过提升真空泵抽气能力提高凝汽器真空度约4 k Pa时能同比降低溶解氧量约5×10^(-9)。通过减小漏气量、提升真空泵抽气能力最终将溶解氧控制在3×10^(-9)的期望值内,有效处理核电机组凝结水溶解氧超标问题。避免了因凝结水溶氧超标带来的压水堆核电机组产生水腐蚀产物的严重后果。为后续类似问题的处理以及在行业内制定严格的凝结水溶氧控制标准提供了借鉴。

In combination with the operation features of nuclear power generation units and the mechanism governing the presence of dissolved oxygen,a systematic analysis and experimental study were performed of the problem that the dissolved oxygen content of condensate water in a nuclear power unit exceeded the standard. The analysis begun from the following three aspects: inspection of the leakage flow rate,verification of the performance of the condenser and the air extraction capacity of the vacuum pump. It has been found that the air leakage flow rate shall comply with the requirements as stipulated in ASME PTC 12. 2 and the influence of the supercooling degree of the condensate water in the condenser of a nuclear power generation unit on its dissolved oxygen content is about 1 /5 to 1 /3 of the value theoretically calculated. When the vacuum degree in the condenser decreases by 4 k Pa through increasing the gas extraction capacity of the vacuum pump,the dissolved oxygen content can decrease by about 5 ppb accordingly. Finally,through reducing the leakage flow rate and increasing the gas extraction capacity of the vacuum pump,the dissolved oxygen content was controlled within the value of 3 ppb as expected,thus the problem that the dissolved oxygen content of condensate water in the nuclear power unit exceeds the standard can be dealt with effectively and the serious consequence of water corrosion products in the pressurized water reactor nuclear power units due to the dissolved oxygen content exceeding the standard can be avoided,thus offering reference for subsequent treatment of similar problems and formulation of a strict condensate water dissolved oxygen content control standard in the industry.