Abstract
Nuclear power plants applying for license renewal are required to undertake a fatigue assessment of various components, which demands the fast calculation of transient thermal stress of the fatigue-sensitive components such as surge lines. In this study, the strategy of Green’s function database construction for the thermal stratification region was investigated, and the thermal stress calculation was shown to be more accurate by dividing the flow cases and thermal zones. Furthermore, a method to determine the fluid temperature for the thermal zones of the thermal stratification region was studied. In addition to the temperature of the hot leg fluid and the outlet fluid from the pressurizer, seven thermocouples installed on the outside wall in the thermal stratification region were used to determine the fluid temperature of thermal zones with stratification, and the calculation result of the fluid temperature was verified with the temperature Green’s functions.
Highlights
Nuclear power has many advantages such as strong power generation capacity, mature technology and cleanliness
Thermal fatigue is regarded as an important damage mechanism in nuclear power plants [1], and the fast calculation of transient thermal stress is a key part of the process of license renewal for nuclear power plants
This monitoring system is based on measuring temperatures by thermocouples at seven dangerous locations, applying the Green’s function method, and assuming the convective heat transfer coefficient in order to achieve fast calculation of thermal stress [5]
Summary
Nuclear power has many advantages such as strong power generation capacity, mature technology and cleanliness. In South Korea, the KFAMS project, developed by KAERI, was installed in the YGN-1 nuclear power plant in order to monitor the fatigue of the pressurizer surge line caused by thermal stratification. A FAMS fatigue monitoring system was developed in Japan This monitoring system is based on measuring temperatures by thermocouples at seven dangerous locations, applying the Green’s function method, and assuming the convective heat transfer coefficient in order to achieve fast calculation of thermal stress [5]. In CATTENOM Nuclear Power Plant Unit 1, the inclination angle of the surge line and the hot section joint of the hot leg was designed to be 45◦ to reduce the stratification of cold and hot fluids in the radial direction, caused by the density difference between hot and cold fluids [9]. We focus on a methodology to solve the thermal zone boundary problem when we calculate the transient thermal stress of the surge line with Green’s function method
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