A steam generator having a primary side for circulating a heated fluid and a secondary side for circulating a fluid to be heated by the heated fluid circulating in the primary side, the steam generator comprising: a channel head for receiving the heated fluid; a tube sheet that separates the channel head from the secondary side; a tube bundle (200,300,500) having a plurality of tubes, arranged in rows and columns, the tube bundle extending from the channel head, through the tube sheet and through at least a portion of the secondary side; and a first number of solid anti-vibration bars (220,320,520); wherein the plurality of tubes comprises: a first column of tubes (210,310,510), the first column of tubes comprising a first tube (212,312) having a curved center line disposed in a first plane (216,316,516), and a second column of tubes (230,330,530), each of the first number of anti-vibration bars being disposed between the first column of tubes and the second column of tubes, the second column of tubes comprising a second tube (232,332) having a curved center line disposed in a second plane (236,336,536), the second plane being parallel to and spaced a distance (206,306) from the first plane, wherein each of the tubes has a tube outer diameter (204,304); wherein each of the first number of anti-vibration bars has a thickness (222,322,522) generally transverse to the first and second planes; wherein the thickness of each of the first number of anti-vibration bars is greater than the distance between the first and second planes minus the tube outer diameter; characterized in that each of the first number of anti-vibration bars is substantially disposed on a longitudinal axis; and each of the first number of anti-vibration bars has a curved center line intersecting the longitudinal axis. a channel head for receiving the heated fluid; a tube sheet that separates the channel head from the secondary side; a tube bundle (200,300,500) having a plurality of tubes, arranged in rows and columns, the tube bundle extending from the channel head, through the tube sheet and through at least a portion of the secondary side; and a first number of solid anti-vibration bars (220,320,520); wherein the plurality of tubes comprises: a first column of tubes (210,310,510), the first column of tubes comprising a first tube (212,312) having a curved center line disposed in a first plane (216,316,516), and a second column of tubes (230,330,530), each of the first number of anti-vibration bars being disposed between the first column of tubes and the second column of tubes, the second column of tubes comprising a second tube (232,332) having a curved center line disposed in a second plane (236,336,536), the second plane being parallel to and spaced a distance (206,306) from the first plane, a first column of tubes (210,310,510), the first column of tubes comprising a first tube (212,312) having a curved center line disposed in a first plane (216,316,516), and a second column of tubes (230,330,530), each of the first number of anti-vibration bars being disposed between the first column of tubes and the second column of tubes, the second column of tubes comprising a second tube (232,332) having a curved center line disposed in a second plane (236,336,536), the second plane being parallel to and spaced a distance (206,306) from the first plane, wherein each of the tubes has a tube outer diameter (204,304); wherein each of the first number of anti-vibration bars has a thickness (222,322,522) generally transverse to the first and second planes; wherein the thickness of each of the first number of anti-vibration bars is greater than the distance between the first and second planes minus the tube outer diameter; characterized in that each of the first number of anti-vibration bars is substantially disposed on a longitudinal axis; and each of the first number of anti-vibration bars has a curved center line intersecting the longitudinal axis.