For the past twenty years, Cooper Nuclear Station has replaced there pumps every two years due to excessive wear. Until this year no one had looked into why CNS pumps had to be replaced so much faster then other plants. It was assumed that sand in the water was the reason for the wear. There was after all nothing unusually, the pumps always have worn that fast there. Cooper Nuclear Station spent millions replacing and repairing pumps twice as often as necessary all because of thermal expansion. The thermal expansion caused the propeller to grind into the bowl, decreasing both the life of the pump and the pump's efficiency. This problem, once identified, was easily solved with regular lift adjustments to prevent the clearance from becoming to small. This just demonstrates that application of even the simplest equation can produce a dramatic difference.