Primary Loop Study of a VVER-1000 Reactor With special Focus on Coolant Mixing

In this paper a detailed model of a VVER1000 reactor pressure vessel (RPV) with the extension of simplified primary loops is presented (Loop model). The primary loop components like steam generators and pumps are modelled by the outer shapes and additional source terms for energy and momentum exchange. The RPV model part is tested without primary loops and compared with former results obtained with a coarser model. The intention of this work is to demonstrate the abilities of modern CFD tools like ANSYS CFX to model technical facilities with complex geometry such as a reactor pressure vessel with its primary loops over all relevant scales from a range of approximately 1mm up to a largest dimension of around 50m. As an example, the rotation of flow patterns at the core inlet derived from plant data obtained at the Kozloduy Nuclear Power Plant (Unit 6) is simulated. As progress against the RPV model the Loop model is able to predict a swirl of flow patterns but due to the lack of technical details like the pump impellers the swirl is overestimated.