The performance of a typical drain system was checked through a pressure drop analysis and the determination of valve sizing coefficients. The operation checks that two-phase flow does not occur upstream of the control valve. Erosion checks are performed at any elbow installed downstream of the control valve where flashing may take place. The analysis does not cover the performance of the feedwater heater or moisture separator and reheater drain systems under transient conditions such as load rejection, i.e., turbine trip. It is believed that accurate valve sizing and appropriate drain cascade are vital to proper drainage.

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