Mechanical and Chemical Indicators for SCC in Alloy 800 Steam Generator Tubing

合金600蒸汽发生器（SG）管材的应力腐蚀开裂（SCC）是CANDU和PWR核反应堆的主要问题。替换合金800 （A800）管也不能免疫SCC；最近在欧洲也报道了龟裂现象。为了提高对合金800在使用条件下开裂的预测，需要彻底了解这种材料的机械和化学行为的相互作用。化学环境的影响是众所周知的；在微观尺度上对机械应力的影响还不太清楚，因此它们的综合影响还没有很好地表征。目前，一个行业资助的研究项目专注于合金600 SG管材料的应力腐蚀开裂，项目团队开发了一种方法来确定微应变、晶界沉淀和显示晶间开裂的样品的微观结构。更重要的是，在理解这些参数对裂纹扩展过程的影响方面也取得了一些进展。因此，下一步是应用这些方法中的一些来研究Alloy 800 SG管材料的SCC行为，目前CANDU反应器的材料选择和先进CANDU反应器（acr）的指定材料。

Stress corrosion cracking (SCC) of Alloy 600 steam generator (SG) tubing is a major issue for both CANDU and PWR nuclear reactors. Replacement Alloy 800 (A800) tubing is also not immune to SCC; cracking has recently been reported in Europe. To improve the prediction of the onset of cracking in Alloy 800 under service conditions, the interplay of mechanical and chemical behaviour of this material needs to be thoroughly understood. The effects of chemical environments are well known; the effects on mechanical stress on a microscopic scale are less well understood and their combined effects therefore have not been well characterized. A current industry-sponsored research project has focused on this aspect for the stress corrosion cracking of Alloy 600 SG tubing materials and the project team has developed methodologies for determining the microstrain, grain boundary precipitation and microstructure of the samples exhibiting intergranular cracking. More importantly, some progress has also been made in understanding how these parameters contribute to the crack growth process. Thus, the next step is to apply some of these methodologies to study the SCC behaviour of Alloy 800 SG tubing material, the current material choice for CANDU reactors and the specified material for Advanced CANDU reactors (ACRs).