碳钢对核主泵用奥氏体不锈钢的污染研究

奥氏体不锈钢在加工、运输和装配过程中如果与碳钢直接接触,就会被碳钢污染,而导致奥氏体不锈钢耐蚀性能的改变。众所周知,核主泵用奥氏体不锈钢对耐蚀性有着非常严格的要求,本文以Z2CN18-10核主泵用奥氏体不锈钢为例,通过FeCl3腐蚀试验和电化学方法测试了被碳钢污染后其耐腐蚀性能的变化。试验结果表明:附着在不锈钢表面的碳钢对其长期总体腐蚀速率影响不大;嵌入式的碳钢颗粒会显著降低奥氏体不锈钢的点蚀电位,增大发生点蚀的倾向;硝酸钝化可部分抵消被污染不锈钢点蚀电位的降低,但该值仍远低于同样经过硝酸钝化,而未被污染的不锈钢的点蚀电位。此外,还针对碳钢污染对核电站辐射场的影响和对燃料包壳热传导效率的影响进行了讨论。

Contamination Study of Austenitic Stainless Steel for Nuclear Reactor Coolant Pump by Carbon Steel

The austenitic stainless steel can be contaminated by carbon steel if they contact with each other directly during the process of machining, transportation or assembly. Thus, the property of corrosion resistance of austenitic stainless steel will be influenced. As well known, the property of corrosion resistance of austenitic stainless for nuclear reactor coolant pump is strictly important. Therefore, the work focused on the contamination of austenitic steel, Z2CN18-10, which was used for nuclear reactor coolant pump, by carbon steel. The corrosion test of FeCl₃ and anodic polarization curve test were performed in the work. The results present that the carbon steel attached to the surface of the stainless steel doesn’t show obviously effect on the long-term general corrosion rate. The carbon steel particles embedded into the austenitic steel significantly reduce its pitting corrosion potential and increase the tendency of pitting corrosion. HNO₃ passivation can partly counteract the decrease of pitting corrosion potential value of the contaminated austenitic stainless steel samples, but which is still much lower than that from the samples of uncontaminated and passivated in the same way. In addition, the effects of carbon steel contamination on nuclear radiation field and thermal conductivity of fuel cladding were discussed.