Thermal fatigue fracture monitoring method for pipeline and device therefor

The present invention provides a method of and device for on-line monitoring thermal fatigue fracture of pipelines or nozzles having fluid of a nuclear power plant with temperature fluctuation flowing therethrough, during plant operation. Namely, a thin-walled portion in contact with the fluid is formed at a predetermined portion of the pipeline. The thermal fatigue fracture of the thin-walled portion is detected. The relation between the fracture of the thin-walled portion and the fracture of the thick-walled portion to which the thin-walled portion is formed is examined. With such procedures, the extent of the thermal fatigue fracture of the thick-walled portion is evaluated based on the detected thermal fatigue fracture of the thin-walled portion. In this case, it is preferred that cracks caused by thermal fatigue are monitored as the thermal fatigue fracture of the thin walled portion and, the size of the crack is detected to evaluate the extent of the thermal fatigue fracture of the thick-walled portion. The risk of occurrence of the fracture of pipelines can also be evaluated by detecting the penetration of the crack through the thin-walled portion caused by thermal fatigue. (I.S.)