Materials Degradation in Nuclear Power Systems: Steam Generator Tube Integrity Research
Materials degradation (especially corrosion and cracking) of structural materials in nuclear power plants is one of major issues for plant safety and long-term operation. In pressurized water reactors, a steam generator (SG) consisting of thousands of metal alloy tubing is a major structural component. SG tubes in nuclear power plants have a long history of materials degradation due to stress corrosion cracking (SCC). To detect various forms of tube degradation including SCC, periodic inspections using non-destructive examination techniques, such as eddy current (EC) testing, are commonly employed.
Therefore, it is critical to evaluate and validate the reliability of the EC testing methods used for assessing the structural integrity of the SG. Once inspection identifies any cracks, it is necessary to decide whether the crack is small enough to leave and continue operation. Analytical or numerical modeling efforts have been conducted to determine the crack size limits from the structural integrity point of view. In this talk, steam generator tube corrosion and cracking research related to the in-service inspection is discussed. Specifically, an experimental method to produce SCC tube samples representative of the field ones is introduced. Modeling and experimental activities related to the SG tube structural integrity are also reviewed.