Prediction of recirculation flow rate for icing prevention in water intake supply systems of nuclear power plants

Abstract

During winter conditions, water intake structures represent one of many critical parts of hydraulic structures. Frazil ice deposits, accumulates and adhere to trash racks that can, in severe circumstances, completely prevent the water from entering the intake structure. One of the possible ways to cope with frazil ice blockage is by using waste heat of the discharge water, where a portion of the pumped water is recirculated back via a feedback loop to the intake structure. The recirculated water, serving as a heat source, can then somewhat warm the intake water and indirectly the air in the intake structure. In this work, an equation is derived that predicts the temperature of pumped water as a function of the recirculated-to-pumped water ratio and a case study on treating a water intake structure in a nuclear power plant is presented. The example demonstrates that, with a proper ratio between the pumped and recirculated flow rate, the formation of frazil ice and atmospheric icing could both be prevented.