Study On Forming Technology And Performance Of Coil Frame Under Special Service Conditions

As a low-carbon,efficient and reliable energy source,nuclear power is of great significance for promoting energy transformation,slowing down climate change,ensuring energy supply and promoting sustainable economic development.Efficient and safe use of nuclear energy plays an important role in promoting China to achieve the goal of "double carbon",especially to achieve "carbon neutralization" by 2060.Control rod drive mechanism(CRDM)is the core component of the nuclear power plant,and its function is to control the reaction rate of the reactor.Therefore,the safe operation of CRDM is directly related to the safety of the whole nuclear power unit.The third generation nuclear power technology of AP1000 puts forward higher requirements for nuclear power equipment and materials,but at present,the stability and heat resistance of coil frame products supporting yoke coil components in CRDM need to be further improved to meet the new requirements of the third generation nuclear power technology for the long-term safe and stable operation of CRDM.Therefore,it is necessary to study the stability and heat resistance of coil frame products in long-term high temperature environment,so as to ensure the safe operation of the third generation AP1000 nuclear power plant.In this study,the CRDM yoke coil frame of pressurized water reactor(PWR)nuclear power unit is taken as the research object.Through the design and optimization of the whole process of coil frame manufacturing and development,the CRDM coil frame which meets the requirements of the third generation of AP1000 nuclear power plant is obtained.Firstly,the comprehensive performance of the coil frame material was evaluated,and the curing thermal behavior of the coil frame material SI 9041 A was studied by differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).Then the integral structure of the coil frame is designed and optimized,and the molding process of the coil frame is numerically simulated and analyzed by Moldflow simulation software.According to the material characteristics and the results of numerical simulation analysis,the orthogonal test method is used to analyze the process parameters that affect the forming performance of the coil frame,and the forming process of the coil frame is optimized.Finally,the thermal stability and mechanical properties of the coil frame products were characterized by TGA test and tensile test,and the effects of different post-curing process parameters on the forming properties of the coil frame were studied.The research results of this project provide specific process parameters and method guidance for the actual production and research of CRDM coil frame products.The main contents and conclusions of this paper are as follows:(1)Based on the analysis of the comprehensive properties of the material,the long glass fiber reinforced silicone resin molding material(SI 9041A)was selected as the development material of the coil frame.The approximate gel temperature,curing temperature and post-treatment temperature of SI 9041 A molded plastics were obtained by DSC non-isothermal test and extrapolation,which were about100 °C,127 °C and 173 °C,respectively.TGA test showed that the cured SI9041 A moulding material had good thermal stability when the temperature increased to 215-325 ℃.When the temperature is 150 °C,the weight loss rate of curing reaction of SI9041 A is the highest.(2)The integral structure of the coil frame is designed by the UG software,and the molding process of the coil frame is simulated by the CAE software Moldflow,so that the forming process is visualized.The draft angle of the lead part of the coil frame is optimized,and the filling process,fiber orientation distribution and pressure distribution of the SI 9041 A molding plastic are obtained,and the molding pressure of the product is determined to be 60 MPa.(3)The factors affecting the bending strength and surface quality of the coil frame are analyzed by orthogonal test,and the optimum forming process parameters are obtained.The optimized process parameters are as follows: molding temperature(130 °C),preheating time(30 s),holding time(15 min),mold closing speed(12mm/s).The causes of common defects in the coil frame are analyzed and summarized.(4)The influence of different post-curing parameters on the forming performance of the coil frame was explored,and the mechanical properties and thermal analysis experiments of the coil frame were carried out.The results show that the thermal oxidative degradation and weight loss curing of silicone resin are the main reasons that affect the formability of the coil frame.Compared with post-curing at room temperature,when cured at 175 ℃ for 24 hours,the tensile strength and thermal stability of the coil frame were significantly improved,the tensile strength increased by 122%,and the mass fraction of thermal weight loss decreased to the minimum,at a high temperature of 350 °C.the weight loss rate decreased by 80%.Finally,the post-curing parameters of magnetic yoke coil frame molding are curing temperature175 ℃ and baking time 24 hours.