The pump exit port is on the top of the pump. They could have used a 90° elbow in the system, but it looks like it was easier to install a U bend than an elbow. Makes a more compact system and allows the polishing feedwater pipe to sit closer to the pump. An elbow would have required more space between the pump and the pipe. The U bend also allows more tolerance for misalignment of the piping. Also for maintenance it's easier to handle the U bend than an elbow. Hydraulically it makes no difference.