Alternating Offset U-Bend Support Arrangement

A steam generator for use in a nuclear power plant, the steam generator comprising plurality of generally parallel tubes for receiving hot primary coolant from a nuclear reactor core, and for circulating said primary coolant within the steam generator for transferring heat from the primary coolant, through the tubes, and into surrounding secondary coolant for heating the secondary coolant to produce steam;

• wherein a first vertical portion of each of the tubes is generally vertical for carrying primary coolant upwards, and wherein a different second vertical portion of each of the tubes is generally vertical for carrying primary coolant back downwards;
• wherein the plurality of tubes collectively comprise a U-bend section, the U-bend section comprising a bending, upwardly convex portion of each of the tubes which connects the first vertical portion of each tube with the second vertical portion of each respective tube for passage of primary coolant between respective vertical portions;
• the steam generator further comprising a U-bend support assembly supporting the tubes in the U-bend section, the U-bend support assembly being at least partially encompassed by the U-bend section;
• the U-bend support assembly comprising a plurality of fan bar assemblies, the fan bar assemblies being in fixed positions relative to each other;
• each fan bar assembly comprising a laterally projecting collector bar and a plurality of flat bars projecting from the collector bar, wherein each collector bar and its corresponding flat bars are all substantially within a common plane, and wherein the flat bars project generally upwards from their respective collector bar and also, optionally, towards a side;
• wherein the fan bar assemblies of the U-bend support assembly are positioned laterally adjacent to one another such that the collector bars of the fan bar assemblies are lined up parallel to other collector bars at the bottom of the U-bend support assembly, and such that the flat bars project upwards between neighboring tubes in the U-bend section and thereby limit the motion of those tubes;
• wherein the tubes in the U-bend section each pass between multiple pairs of flat bars, with each pair of flat bars being formed by flat bars of two adjacent fan bar assemblies;
• wherein each flat bar has a thickness;
• wherein within at least some fan bar assemblies the flat bars do not all have the same thickness, with some flat bars in the assembly being thick flat bars and other flat bars being thin flat bars which are thinner than the thick flat bars;
• wherein at least some pairs of flat bars are asymmetrical pairs, the asymmetrical pairs being formed by a thick flat bar of one fan bar assembly and a thin flat bar of an adjacent flat bar assembly which are adjacent to each other;
• wherein at least some of the tubes within the U-bend section each pass through a plurality of asymmetrical pairs of flat bars, with a portion of each of said tubes being laterally displaced by the thick flat bar of at least one asymmetrical pair, and with part of said tubes within the U-bend section having a serpentine shape maintained by said displacement by one or more thick flat bars.