Creep Damage Analysis And Life Evaluation Of Pressure Vessel In Molten Salt Reactor Core Based On Continuum Damage Model

The structural integrity of the pressure vessel in reactor core plays an important role in the safe operation of the reactor.The normal working temperature of the pressure vessel in Thorium molten salt reactor's(TMSR)core is designed to be 650 ° C with a design life of 10 years.Because the pressure vessel needs to be in service at 650? for a long time,the analysis of high-temperature creep damage under multi-axial stress is a crucial part of the structural integrity research.Nickel-based alloys are widely utilized as heat-resistant materials,among which UNS N10003 alloy was selected as structural materials for the pressure vessel of TMSR's core due to its excellent mechanical properties and resistance to radiation embrittlement.In this study,by fitting five groups of uniaxial tensile creep test data with constant stress of 220 MPa,250MPa,275 MPa,320MPa and 380 MPa at 650?,the creep constitutive equation of UNS N10003 alloy at 650? and material parameters of Lemaitre multi-axial creep damage model were obtained.Based on national standard GB150 and ASME standard,the wall thickness of the pressure vessel was designed and analyzed.The wall thickness was set as 30 mm and is a thin-wall pressure vessel.The A7 type of lug support in national standard JB-T4712 was selected according to the inner diameter of the vessel for further analysis of the overall structure of the pressure vessel.The ABAQUS software was used to build the finite element model of the pressure vessel,and the creep behavior was simulated by combining the creep constitutive equation.Through the simulation results,the classical lug supports in the structure were further optimized.The equivalent stress of the pressure vessel under static design loadings was obtained by simulation,then,creep damage calculation and life evaluation of the pressure vessel were carried out based on Lemaitre multi-axial creep damage model.The numerical results show that the design of thin-walled pressure vessel with a wall thickness of 30 mm is safe during its design life and saves a lot of pressure vessel cost compared with other types of reactors.At the same time,when selecting lug supports to support TMSR core's pressure vessels,it is necessary to thicken the stiffen panel inside the supports with a thickness not less than 60 mm,so as to ensure the safety and reliability of the structure within the specified design life of 10 years and provide theoretical data reference for engineering practice.