Unsteady flow analysis of secondary steam inside a moisture separator

Abstract: A variety of method are applied in order to assess the force loads induced by the unsteady flow of steam on a plate structure inside a moisture separator at Forsmark nuclear power plant. The plate structure is suffering from cracks and structure failure which are to be investigated to see if they arise from fatique loads induced by the fluid flow. Both steady turbulence modeling (RANS) and scale resolving simulations (LES) are performed using STAR-CCM+. A conservative thermal expansion analysis is conducted in order to investigate the displacement of the moisture separator. The obtained results shows that the amplitude of the flow induced force loads are not expected to cause the structure failure. In the frequency content of the forces clear spikes are present, which may suggest that fatique loads are the problem. However, the force amplitude is considered to small in order to cause failure to the plate structure. The thermal expansion analysis show large displacements of the moisture separator structure, but the methods applied are very conservative. A more advanced methodology when investigating the thermal expansion is recommend as future work.