Condensation induced water hammer is one kind of water hammer caused by cavity collapse, which occurs frequently in engineering pipelines and can bring about enormous damage. Due to the vapor condensation, the form...Condensation induced water hammer is one kind of water hammer caused by cavity collapse, which occurs frequently in engineering pipelines and can bring about enormous damage. Due to the vapor condensation, the formation and collapse of cavity are transient and of two phase character. In order to simulate the process of cavity formation and collapse, a physical model is suggested. In the model, the cavity boundary is treated as free surface of a calculating field. A numerical solution of the Navier Stokes equation is obtained by using a modified VOF (volume of fluid) method, in which the vapor condensation is considered. With the method, formation and collapse of the cavity are described, and the highest pressure is acquired. The numerical simulation results coincide with experimental results.展开更多
The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This conce...The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This concerns the Westinghouse standard three-loops plant for which the RHR is the low pressure part of the St （safety injection）. In some cases one or both RHR trains may become inoperable for SI function. As a response to this letter, Westinghouse Electric Belgium is providing RELAP5 analyzes for Westinghouse NSSS （nuclear steam supply system） European plants to assess the thermal hydraulic behavior of the RHR suction piping system for ECCS （emergency core cooling system） initiation events postulated to occur during startup/shutdown operations. Several concerns including condensation induced water hammer and voiding at the RHR pump have been investigated. As a conclusion, the analysis allowed to define the bounding hot leg temperature conditions under which both RHR trains remain safely operable. These bounding conditions are then implemented by the customer in their OPs （operating procedures） to achieve safe operations and successful accident management.展开更多
文摘Condensation induced water hammer is one kind of water hammer caused by cavity collapse, which occurs frequently in engineering pipelines and can bring about enormous damage. Due to the vapor condensation, the formation and collapse of cavity are transient and of two phase character. In order to simulate the process of cavity formation and collapse, a physical model is suggested. In the model, the cavity boundary is treated as free surface of a calculating field. A numerical solution of the Navier Stokes equation is obtained by using a modified VOF (volume of fluid) method, in which the vapor condensation is considered. With the method, formation and collapse of the cavity are described, and the highest pressure is acquired. The numerical simulation results coincide with experimental results.
文摘The Westinghouse Nuclear Safety Advisory Letter NSAL-09-8 investigated the possibility of presence of vapor in RHR （residual heat removal） system in modes 3/4 LOCA （loss-of-coolant accident） conditions. This concerns the Westinghouse standard three-loops plant for which the RHR is the low pressure part of the St （safety injection）. In some cases one or both RHR trains may become inoperable for SI function. As a response to this letter, Westinghouse Electric Belgium is providing RELAP5 analyzes for Westinghouse NSSS （nuclear steam supply system） European plants to assess the thermal hydraulic behavior of the RHR suction piping system for ECCS （emergency core cooling system） initiation events postulated to occur during startup/shutdown operations. Several concerns including condensation induced water hammer and voiding at the RHR pump have been investigated. As a conclusion, the analysis allowed to define the bounding hot leg temperature conditions under which both RHR trains remain safely operable. These bounding conditions are then implemented by the customer in their OPs （operating procedures） to achieve safe operations and successful accident management.
