A sludge lance for use in a steam generator having a shell enclosing a tube sheet and a plurality of substantially uniformly diametrically sized tubes extending from the tube sheet with the tubes disposed in a substantially regular pattern having substantially uniform narrow gaps between adjacent tubes, the regular pattern forming a generally, elongated central tube lane along which a divider plate extends along the elongated dimension, approximately in the center of the central tube lane and the shell having at least one access opening in-line with the central tube lane, the sludge lance comprising: a mounting assembly structured to support a drive assembly and a rail; the drive assembly structured to move the rail along the central tube lane on one side of the divider plate between the tubes and the divider plate; and a nozzle assembly having a body assembly, the nozzle assembly body assembly defining a fluid passage configured to be a conduit for a pressurized fluid employed to lance the gaps between the adjacent tubes and nozzle assembly body assembly being sized to pass between the tubes and the divider plate, the nozzle assembly being coupled to the rail; characterized by: a plunger reciprocally moveable in a cavity in the nozzle assembly body assembly and spring biased in a direction to contact the divider plate when the nozzle assembly is positioned in the central tube lane; and means for sending the pressurized fluid through the fluid passage of the nozzle assembly body assembly, wherein the nozzle assembly body assembly is configured so the pressurized fluid holds the plunger fixed with respect to the divider plate and prevents the plunger from moving in the cavity. a mounting assembly structured to support a drive assembly and a rail; the drive assembly structured to move the rail along the central tube lane on one side of the divider plate between the tubes and the divider plate; and a nozzle assembly having a body assembly, the nozzle assembly body assembly defining a fluid passage configured to be a conduit for a pressurized fluid employed to lance the gaps between the adjacent tubes and nozzle assembly body assembly being sized to pass between the tubes and the divider plate, the nozzle assembly being coupled to the rail; characterized by: a plunger reciprocally moveable in a cavity in the nozzle assembly body assembly and spring biased in a direction to contact the divider plate when the nozzle assembly is positioned in the central tube lane; and means for sending the pressurized fluid through the fluid passage of the nozzle assembly body assembly, wherein the nozzle assembly body assembly is configured so the pressurized fluid holds the plunger fixed with respect to the divider plate and prevents the plunger from moving in the cavity. a plunger reciprocally moveable in a cavity in the nozzle assembly body assembly and spring biased in a direction to contact the divider plate when the nozzle assembly is positioned in the central tube lane; and means for sending the pressurized fluid through the fluid passage of the nozzle assembly body assembly, wherein the nozzle assembly body assembly is configured so the pressurized fluid holds the plunger fixed with respect to the divider plate and prevents the plunger from moving in the cavity.