Temperature Analysis And Construction Control By Conventional Island Turbine Base Soleplate In Nuclear Power Station

Nuclear power plant construction is usually divided into two major parts: nuclear islands and conventional islands.Conventional islands are the workshops for the maintenance of nuclear power plant operators.The most critical part is the turbine infrastructure,which is used to withstand machine loads.Therefore,strict requirements are imposed on construction cracks and it belongs to mass concrete pouring.In the infrastructure construction of conventional island steam turbines in nuclear power plants,multiple castings are commonly used in our country,which is likely to cause adverse effects on the project quality because of long construction period.With the accelerating pace of nuclear power construction,in order to shorten the construction period,it is necessary to cast the steam turbine foundation all at once.Therefore,how to effectively control the temperature cracks has become the most important issue currently.First of all,in the early stage of concrete pouring,the cement releases a lot of heat of hydration in contact with water.After the pouring is completed,the heat will be transferred to the air as the environment changing,the temperature begins to drop.If the temperature drops too fast,a temperature gradient will be generated to generate temperature stress,which is the main reason for the current cracks in large volumes of concrete.Secondly,materials,construction processes,construction personnel,and ambient air temperature are other causes of concrete cracks.In the construction of nuclear power plants,surface cracks do not affect the use of structures,they must still be strictly controlled.Since the conditions that lead to the occurrence of cracks are numerous and different,it is necessary to analyze it in many aspects.In order to solve the problems above,this article starts from the following aspects:1.This article focuses on the temperature field and temperature stress of mass concrete,specifically expounds the formation mechanism and hazard of temperature cracks and deduces the formation process of temperature field.The finite element software was used to simulate different thickness and temperature changes derived formula,and the cooling coefficient was compared with the standard temperature drop coefficient.2.The finite element analysis software was used to simulate and analyze the temperature field and temperature stress of mass concrete,and the early temperature and temperature stress distribution of the nuclear base plate was obtained.3.Analyzing the temperature and temperature stress data obtained from the finite element simulation,and obtain the position and appearance of the most unfavorable cross section according to the stress change situation: Temperature cracks mainly occur at the position of the inside corner,starting from the vertex of the inside corner along with the casting body in the direction of 45°.The determination of the most unfavorable cross-section provides direction and basis for the development of temperature monitoring and subsequent insulation and conservation measures.4.Calculate the early temperature of concrete by using the one-dimensional difference method theoretical formula.Through the combination of theoretical numerical values and simulated temperature values,targeted construction measures for mass concrete construction are formulated.5.Monitoring the early temperature changes of concrete in the field,comparing theoretical data with actual measurement data,and adjusting dynamic maintenance work timely during actual construction.The simulated data is compared with the actual measurement data to detect the simulation degree of the model,and the temperature change is forecasted in advance.The project is selected at the initial stage of construction in order to provide a scientific basis.The results show that the temperature drop trend of the finite element simulation is approximately in common with the actual situation.Practice has shown that with the methods of finite element simulation and dynamic monitoring,it will provide a reasonable basis for the selection of construction plans,ensure the quality of concrete pouring,and supply a solid foundation for the construction of mass concrete in subsequent nuclear power plants.