Abstract: A steam generator lancing system for cleaning tubes and tubesheets of a steam generator. The lancing system includes a nozzle block including at least one nozzle adapted for fluid communication with a high pressure hose. The lancing system also includes a support assembly including a carrier for transporting the nozzle block through the steam generator and a control system operative to selectively position the nozzle with respect to the tubes and tubesheets in the steam generator. Finally, in the preferred embodiment, the lancing system includes a rocker assembly operable to rotate the nozzle about a rocker axis to improve cleaning efficiency.