承压热冲击下DVI接管动态应力特性研究

压力容器直接注入（DVI）接管在热冲击下的动态应力特性对于反应堆压力容器（RPV）结构完整性评估具有重要意义。建立了含DVI接管的RPV压力壳热流固耦合数值计算模型，并进行了验证分析；然后研究了蓄压安注箱（ACC）和堆芯补水箱（CMT）安注时RPV筒体和DVI接管热工水力特性；最后分析了热冲击下RPV筒体和DVI接管连接高应力区的温度分布、等效应力和等效塑性应变分布特性。研究结果表明，ACC安注阶段RPV筒体和DVI接管连接区存在较大的温度梯度和等效应力，且发生了局部塑性变形。若发生承压热冲击事件，应控制好DVI接管连接区温差，确保反应堆压力容器的结构完整性。本文开发的热冲击下热流固耦合数值计算模型和计算方法可用于核岛内DVI接管与RPV筒体的安全性评价，也可用于类似承压结构在热冲击下的动态应力特性分析。 

Study on Dynamical Stress Characteristics of DVI Nozzle Subjected to Pressurized Thermal Shocks

The dynamic stress characteristics of direct vessel injection (DVI) nozzle under thermal shock are of great significance for the structural integrity evaluation of reactor pressure vessel (RPV). The thermal-fluid-solid coupling numerical calculation model of the RPV pressurized shell containing the DVI nozzle is firstly established and verified. Then the thermal hydraulic characteristics of RPV cylinder and DVI nozzle of ACC and CMT are studied; Finally, the distribution characteristics of temperature, equivalent stress and equivalent plastic strain in the high stress zone of RPV cylinder and DVI nozzle under thermal shock are analyzed. The results show that there is a large temperature gradient and equivalent stress in the connection area between RPV cylinder and DVI nozzle during ACC safety injection, and local plastic deformation occurs. In case of pressurized thermal shock event, the temperature difference in DVI nozzle area shall be controlled to ensure the structural integrity of reactor pressure vessel. The thermal-fluid-solid coupling numerical calculation model and method developed in this paper can be used for the safety evaluation of DVI nozzle and RPV cylinder in nuclear island, and can also be used to analyze the dynamic stress characteristics of similar pressure-bearing structure under thermal shock.