Abstract
The stud bolts tend to degrade faster by high temperature(over 45$0^{\circ}C$). Therefore, replacement cycle inspection of stud bolts were carried out various method such as ultrasonic test(UT), magnetic test(MT), wobble test, visual test and hardness test. Especially, wobble test method has been applied to determine replacement evaluation criteria of stud bolt after long time operation. We applied three different methods on the three site and the obtained data are compared with the results from the evaluation methods. From the results, the replacement criteria for stud bolts under high temperature in power plants are proposed.