The Leak Before Break(LBB) Assessment Of Nuclear Piping Containing Crack And The Crack Growth Simulation By Using Molecular Dynamics

Three-dimensional crack behavior simulation analysis and anti-crack fracture design have been a main subject in fracture theory and engineering application. Piping system is a key part of nuclear power engineering. Utilizing the three-dimensional finite element analysis software ANSYS and the specialized crack analysis programs Franc3 D, three-dimensional crack behavior and leak before break(LBB) case were simulated and evaluated of a pipe with a crack in waste heat exhaust system of China Experimental Fast Reactor(CEFR).In fast reactor, the piping is working under a high temperature. Therefore, the code RCC-MR.A16 was adopted in this article that is suitable for materials and structural safety design at high temperature. Material used in this article is modified 9Cr1Mo-T91/P91. The analysis model of pipe section was built in three-dimensional entity structure containing a cracks and the high temperature and creep effects were considered. The simulation results show that creep contributes more effect on crack growth than fatigue. The evaluation results on LBB of studied T91 steel pipe with a crack-like defect can satisfy the need of LBB design guidelines. The research results can be referenced in pipe material choose, safety assessment and structural integrity evaluation of a pipe containing defects at high temperature in a fast reactor design.Molecular dynamics is mainly dominated by molecular simulation, Newtonian mechanics is the main motion rule to calculate the molecular system.according to the temperature and the initial atomic speed, the simulation calculate various macroscopic properties of the simulation model under different loads. In this paper,using simulation software LAMMPS,we made molecular dynamics simulation of the three-dimensional model of crack extension under the condition of different temperature and loading rate. Finally we get model transformation rules and the atomic motion situation of crack tip under different temperature and loading rates.