In order to establish measures for managing materials degradation, the deg­radation mechanisms must first be fully understood. Inspection techniques, mitigation methods and repair technologies depend on knowledge grounded in experimental studies of degradation mechanisms or in field operating experience within power plants (IAEA, 2011). There are three stages to managing materials ageing in nuclear power: preventive action; monitoring and inspection; and repair and replacement. In preventive action, improve­ment of the materials, reduction of stress and improvement of water chem­istry can be used as measures to prevent cracks of Ni alloys (IAEA, 2011). Surveillance of pressure vessels can be carried out through monitoring and inspection to check the soundness of parts. For example, by checking for leakage of primary coolant through wall cracks in J-welds of the upper ves­sel head penetration (VHP) or lower bottom mounted instrumentation (BMI) nozzles, pressure boundary performance can be maintained. In the case of coolant leakage, boric acid residues on the outside of the pressure vessel or carbon steel corrosion products can be detected through visual inspection. Cracking can occur in operating power plants due to material properties or residual stress, therefore the timing of cracking can differ from the experimental result. Regardless of the cause, it is important to detect cracks as early as possible. Besides visual inspection, methods such as pene­trant testing or eddy-current testing (ECT), and ultrasonic testing (straight beam and longitudinal wave angle beam UT) can also be used. In repair and replacement, the damaged parts should be isolated from the corrosive envi­ronment, or the tensile stress upon them reduced. In the case that these two measures are inappropriate, the parts should be replaced with others made from more corrosion-resistant materials. In order to systematically manage PWR structural materials, a common objective has been established, and much research has been done as a collaborative effort between many coun­tries. The joint research programme for 2011 is as shown in Table 7.1.