Steam generator for sodium cooled fast reactor, heat transfer tubes thereof, and leak detection unit for heat transfer tube thereof

A heat transfer tube damage detection unit of a steam generator for a sodium-cooled fast reactor, detection unit comprising:

• plurality of heat transfer tubes, wherein each is formed as a dual tube having an inner tube and an outer tube enclosing the inner tube, and having flow grooves formed between the inner tube and the outer tube for flowing gas;
• a lower tube sheath for receiving the heat transfer tubes;
• a plurality of detection holes formed by penetrating the lower tube sheath that has the heat transfer tube joined so as to communicate with the flow grooves;
• a plenum selectively coupled to the detection holes using connecting tubes for the gas to flow into the flow grooves;
• and
• a pressure gauge for measuring a pressure of the gas flowing into the plenum to detect whether the heat transfer tube is damaged,
• wherein a plurality of heat transfer tube holes are formed in the lower tube sheath, in the heat transfer tubes extending into the heat transfer tube holes;
• the outer tube is joined to a first surface of the lower tube sheath and the inner tube penetrates the heat transfer tube hole to join to a second surface of the lower tube sheath;
• a gap between the heat transfer tube holes and the inner tube is in communication with the flow grooves;
• the heat transfer tube holes are radially arranged along the lower tube sheath, and
• each detection hole communicates with a corresponding heat transfer tube hole, and also communicates with its side along a radial direction of the lower tube sheath, and
• wherein the plurality of detection holes are arranged on a straight line along the radial direction and are formed at different depths in the lower tube sheath.