Thermal fatigue in pipelines caused by thermal stratification

This work refers to a bibliographic research and experiments arranges to study the damages in horizontal pipe subjected to thermal stratification. Thermal stratification is a very common industrial phenomenon, in nuclear or conventional industries, so it is important to take care of it. The thermal stratification phenomenon is associated to fluid flowing in low velocities and at different temperatures. If the thermal stratification exist in a horizontal pipe, it is subjected to longitudinal and circumferential nonlinear tensions and to thermal cycling in the interface of the fluids. The nuclear power plants designed up to 80's, just linear tensions were used in the calculations, and some fails occurred. The first one was reported in 1988 in Farley 2 nuclear power plant. After that the NRC published a bulletin to recommend evaluations and corrections of the pipes where thermal stratification is present. In a nuclear power plant the most probably pipes where thermal stratification can be present are the hot legs and cold legs, the pressurizer surge line, the residual heat removal circuit and the injection nozzle of the steam generator. The proposed studies are related to PhD curse that will be studying the damages caused to the pipe material due to thermal stratification, plotting the S-N curves of the material and developing a software to simulate the thermal stratification damages in pipes. A experimental circuit is being built where thermal stratification could be established and studied. (author)