Abstract

In the operating nuclear power plants, piping and components installed in the in-service testing systems connected to the reactor coolant system are potentially exposed to fatigue caused by thermally stratified flow, possibly threatening its integrity. The emergency core cooling system (ECCS) is one of candidates for which the thermal stratification phenomenon can occur. Because temperature difference between the hot coolant in the cold leg and the cold cooling water injected from the ECCS line is 200 K or more, buoyancy due to density difference may have significant influence on thermal-hydraulic characteristics of the mixing flow. Therefore, in this study, the need to consider proper buoyancy models in governing equations, especially turbulence transport equations, for accurate prediction of single phase thermal stratification in the cold leg and downcomer by ECCS injection is numerically studied using ANSYS CFX R17.2.

摘要

在运行中的核电厂中，安装在与反应堆冷却剂系统连接的在役测试系统中的管道和组件可能会因热分层流而导致疲劳，并可能威胁其完整性。紧急堆芯冷却系统（ECCS）是可能发生热分层现象的候选组件之一。由于冷段中的热冷却剂与从ECCS管线注入的冷冷却水之间的温差为200 K或更高，因此，由于密度差异而产生的浮力可能会对混合流的热工水力特性产生重大影响。因此，在这项研究中，需要在控制方程（尤其是湍流输运方程）中考虑适当的浮力模型，