Design of an Innovative Moisture Separator Technology for Use in Nuclear Power Plants: Numerical Approach — Part 1

The Moisture Separator Re-heater (MSR) is a key component of Nuclear Power Plants (NPP) both in terms of performance and avoiding erosion and erosion/corrosion damage. Wet steam is usually dried in a MSR by inertial separation using separator elements. Depending on the design of a MSR, the technology of separator elements contributes significantly to its size and performance, hence is seen as a subject for in-depth investigation, improvement and innovation. Computational Fluid Dynamics (CFD) has been used to understand the working principles of moisture separating devices, in particular the OpenFOAM platform has been utilized for this scope. Eulerian/Lagrangian models, wall-droplet interaction and water film formation models have been adopted to determine the physical phenomena occurring during the moisture separation process. Additional sub-models have been implemented to make a more robust solver and to solve in a comprehensive way all the possible physical processes: in particular a two-layers turbulence model and a film breakup model have been implemented. An out-of-the-box thinking approach was adopted to devise a new proposed chevron vane. Aerodynamic principles were used to design an innovative concept of separator panel, which can entrap the moisture droplets and water rivulets through a subsequent formation of recirculating steam representing artificial slots (hidden pockets) within the separator channel. The control of the steam separation on precise regions of the separator panel wall, helps the drainage of the water film without the utilization of physical obstacles (pockets or drainage channels). To validate the results achieved from the numerical simulation and to characterize separation performance of a new kind of separator technology, a bespoke test rig has been designed, built and put into operation at typical MSR operating conditions [1]. Throttling calorimeter methodology has been adopted to measure, with very good accuracy, the residual moisture content after the separator. The design developed has shown excellent separation performance. Particularly, this solution will allow improved MSR performance and significantly reduced MSR size. This represents an innovative technology which is a major advance on current technology available within the industry. The novel design features have been patented by General Electric. The first operation of a MSR with this technology is eagerly awaited.