Thermal Hydraulic Analysis Of Thermal Stratification For Pressurizer Surge Line

With the continuous development of the national economy, the energy shortage hasbecome an important factor restricting the economic development in healthy, stable andsustainable way. Nuclear energy is a crucial choice to solve national energy shortageproblem. In pressurized water nuclear power reactor, the thermal stratificationphenomenon occurs in the Pressurizer surge line during the reactor operation transitionwhich will produces huge thermal shocks and results in increasing possibility of fatiguefail to surge line. Meanwhile, the potential bending distortion by effects mentioned abovewill not comply with design distortion. So it is of great importance to research on thermalstratification in the Pressurizer surge line for the safety and reliability of nuclear powerplant.Focusing of the thermal stratification phenomenon in Pressurizer surge line, thefollowing parts are analyzed in the paper. First, reason and mechanism of thermalstratification are discussed, and key parameters of this effect are given. Secondly, anumerical simulation model is built and thermal stratifications in different steady state aresimulated. The results are compared to theoretical analysis to verify the conclusion oftheoretical analysis. Thereafter, the numerical simulations are finished in different transientstate to analysis the thermal stratification phenomenon is each transient include in-lineflow condition, distribution of temperature. Improvement suggestions are proposedaccording to research results. Finally, by the chance of new nuclear power plantcommissioning, the experimentally study on temperature distribution under thermalstratification is premiered done in real plant. according to the experiment results, thetheoretical analysis and numerical simulation are verified.This research provided theoretical guidance and data input to further fatigue andstress study of the thermal stratification in Pressurizer surge line. it also provided thefoundation for the subsequent thermal stratification research and safety evaluation.Meanwhile, the results can be used to evaluate the lifetime of Pressurizer surge line ofsame type reactor. Therefore, there are theoretical value and practical meaning of thispaper.