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:

• a heat transfer tube that includes an inner tube, an outer tube made of material having a thermal expansion coefficient less than that of the inner tube, and helium flow grooves formed between the inner tube and the outer tube for flowing helium gas;
• a plurality of detection holes formed by penetrating a lower tube sheath that has the heat transfer tube joined so as to communicate with helium flow grooves;
• a helium plenum coupled to the detection holes for the helium gas to flow into from the helium flow grooves;
• and
• a pressure gauge for measuring the pressure of the helium gas flowing into the helium plenum to detect whether the heat transfer tube is damaged.

A steam generator for a sodium-cooled fast reactor comprising:

• heat transfer tubes of a double-wall structure each provided with an inner tube and an outer tube made of material having a thermal expansion coefficient less than that of the inner tube;
• an inner shroud in which a pressure buffer space is formed and cover gas is supplied therein;
• a heat transfer tube coil portion formed by the heat transfer tubes wound in a coil form outside the inner shroud;
• a damage detection unit provided below the heat transfer tube coil portion on one side of the lower tube sheath joined to the heat transfer tubes so as to detect whether the heat transfer tube is damaged or not;
• and
• a rupture disk provided on the top of the inner shroud so that when the heat transfer tube is damaged, the heat transfer tube is ruptured by a pressure rise due to a reaction of sodium and water, and gas generated from the heat transfer tube coil portion flows into the pressure buffer space.