3-D Transient Coupled Sealing Analysis For The Model Of Reactor Pressure Vessel

This paper comes from the project of "the 3-D Program Development for Transient Sealing Analysis in Reactor Pressure Vessel". This project is the subproject of the national defense key technology pre-research project on the program development of reactor design in the tenth Five-year Plan. The aim of this research project is to develop advanced program system of sealing analysis for the nuclear pressure vessel, to improve the design quality and level, to ensure the reliability of the sealing system in the advanced pressurized water reactor vessel, to increase the design quality and ensure the design reliability of the nuclear vessel sealing system.The sealing failure of flange is the primary failure mode of the nuclear reactor pressure vessel because it works in formidable environment with high temperature, high pressure and radioactive working substance. The sealing analysis involves not only the elasto-plastic nonlinear between sealing surfaces, thermal nonlinear and transient characteristics of thermal transfer, but also couple interaction among them. Till now, no matter the domestic or the foreign commercial software doesn't has the comprehensive function. The main task of this paper is to improve and extend the sealing analysis program based on the developed 3-D program system of reactor pressure vessel, to increase analysis functions as well as solving scale and speed.The main work of this paper includes:①The automatic modeling program of finite element analysis for the reactor pressure vessel model is developed and improved. The finite element mesh for arbitrary region of the model can be generated based on the mapping mesh method. Using this program, the parametric FE model and calculation data of the RPV model can be obtained.②An efficient linear equations solver is developed. It includes a block elimination LDLT decomposition and solution program as well as a corresponding bandwidth optimization program. It can enlarge the solving scale and improve the solving efficiency. ③The following function expansion and algorithm improvement has been done to the 3-D Transient Sealing Analysis program: restart function is added to realize the breakpoint control, the contact state correction method of the plane bolt and the spherical bolt at the pre-tension work condition is improved to simulate the real situation better.④Several 3-D node-variable quadratic isoperimetric elements are added to the element library of the program, such as the 10-node tetrahedron quadratic element, the 15-node pentahedron quadratic element and the 20-node hexahedron quadratic element. The shape functions of the isoperimetric elements are deduced and added to the corresponding module of the program. ⑤The improved transient sealing analysis program for reactor pressure vessel is applied to analyze the 1/4 structure of the model under the cool and the thermal work conditions. The scale of the calculation module is more than 100 thousand degrees of freedom. The load cases include bolt pre-tensioning, compression, heating, thermostated heating and cooling process. The computational results are compared with the experimental data including stress, temperature, bolt force and separation, which are obtained from the pressure vessel module by the China Nuclear Power Operation Research Institute. Either under cooling or heating cycle, the computational results are in good concordance with the experimental data in both the qualitative regularity and the quantitative data.