Rotating Drum Raw Water Strainer Fluid Mechanics and Debris Cleanout

McGuire nuclear station and Alden have completed an extensive computational and experimental study characterizing the operating fluid mechanics and debris clean out behavior of a rotating drum strainer. The raw water strainer is installed on the suction side of the nuclear service water (RN) system pump. The strainer consists of a cylindrical shell inside of which a rotating drum is installed that is equipped with approximately 1500 filter media openings. Process supply water spills through the rotating drum openings on its way to the RN pump suction inlet, thus removing debris greater than approximately 3/16^″. As the drum loads with debris, the operating pressure drop through the drum increases. At a preset drum pressure drop level, the backwash supply system is activated and sprays water through two supply shoes into backwash exit channels from which the debris laden water can be evacuated. The study was initiated to determine fluid dynamics and debris clean-out performance under various conditions. With definitive operating mechanics identified, an improved drum clean-out procedure and system was developed. The study combined the strengths of analytical CFD modeling with extensive experimental validation and debris testing. The study has proven to be valuable to the plant engineering team to help reduce required backwash supply flow, backwash channel exit flow (and hence horsepower) and to conclusively demonstrate the cleaning capabilities of the installed rotating drum strainer design.