Thermal Aging Effect of CDSS on the Integrity of the PWR Primary Pipe With Damage Tolerance Method

The structure integrity of the primary pipe from the Pressure Water Reactor (PWR) will be one of the most serous problems for the life extension of the reactor for that the toughness of the Duplex Stainless Steel will reduce sharply for thermal aging effect for a long time service at 350°C high temperature. To evaluate the structure integrity of the primary pipe, the material properties, such as the basic mechanical properties, the Charpy impact energy and the fracture properties for different aging times are investigated by macro mechanical tests. The stress analysis of the primary pipe for internal pressure, thermal stress and static stress for weight are performed. With the damage tolerance method, the residual toughness of the material and primary pipe structures are investigated according to the stress analysis of the material and the damage mechanics. From the experimental results, it is found that the strength increases while the toughness decreases with the increment of the accelerated aging time. The safety factor of the structure strength increases while that of the toughness decreases.