Detection of leaks in heat exchanger tubes - particularly for sodium/sodium exchangers in rapid neutron reactors

摘要

Leaks in the tubes of a shell and tube heat exchanger, esp. one in which the hot and cold heat transfer fluids are liquid sodium, may be detected without dismantling by lowering the level of sodium in the tubes until it coincides with the level of the tops of the tubes; lowering the temp. of the sodium below the tubes so that a disc of solid sodium covers the bottoms of the tubes; applying a pressure by injecting an inert gas above the tubes and examining the level of liquid sodium in the tubes. A leak in any tube will be detected by a drop in the level of the liq. sodium in that tube. The examination is done by the use of a television camera or an endoscope. The appts. for lowering the temp. of the sodium below the tubes consists of a vertical cylindrical central shaft and a number of movable paddles each fixed to the end of a vertical shaft, each such shaft being in a guide, attached to the central shaft, so that it can pivot around, and move along, its longitudinal axis. Each paddle is hollow, and has inlet and outlet pipes for cooling liquid, and internal baffles. Each paddle is in the shape of a sector of a ring the inner dia. of which is about equal to that of the central shaft, the outer dia. being about twice that of the central shaft. The lower face of each paddle is covered with an insulating coating.