Patent Number: 041586034
Section: summary

The invention relates to a blow-off device for limiting excess pressure in nuclear power plants, especially in boiling water nuclear power plants, and more particularly wherein the blow-off device has at least one condensation tube disposed so that a lower outlet end thereof is immersed in a volume of water (condensate) in a condensation chamber having a gas cushion located in a space above the volume of water, and the upper inlet end of the condensation tube extending out of the volume of water and being connected to a source of steam that is to be condensed or a steam-air mixture, the outlet end of the condensation tube, for smoothing the condensation, being provided with wall parts forming passages extending in axial direction, delimited from one another and terminating in the water volume, the wall parts serving to subdivide steam flow from the source thereof and bubbles produced in the water volume. Such a blow-off device has become known heretofore from German Published Prosecuted Application DT-AS 2 212 761; especially in FIG. 5 thereof. In this heretofore known device, the passages terminating in the water condensate are formed by annular channels of telescoping tube sections. It has also become known heretofore from German Published Non-Prosecuted Application DT-OS 2 457 901 to subdivide more finely the outlet cross section of the condensation tube. The interior of the outlet of the condensation tube is provided with a framework of wall parts. Even if a relatively fine subdivision of the steam flow and the bubbles can be effected by means of the last-mentioned heretofore known device, the cooling and wetting of the partial flows of steam, especially for high-quantity flows of steam, are relatively slight, because all of the passages are then filled with saturated steam, the partial flows of steam being able to be reunited as bubbles as they exit from the tube outlet end. It is accordingly an object of the invention to provide a blow-off device for limiting excess pressure in nuclear power plants that is of such improved and perfected construction and operation that good cooling and wetting of the partial steam flows and partial bubbles are produced during the blow-off process, and wherein the production and attachment of the wall parts to the condensation tube is much simplified over those of the aforementioned prior art. With the foregoing and other objects in view, there is provided, in accordance with the invention, in a blow-off device for limiting excess pressure in nuclear power plants, at least one condensation tube disposed so that a lower outlet end therof is immersed in a volume of water in a condensation chamber having a gas cushion located in a space above the volume of water, and the upper inlet end thereof extending out of the volume of water and being connectible to a source of steam that is to be condensed or a steam-air mixture, the outlet end of the condensation tube, for smoothing the condensation, being provided with wall parts forming passages extending in axial direction, delimited from one another and terminating in the water volume, the wall parts serving to subdivide steam flow from the source thereof and bubbles produced thereby in the water volume, the wall parts being constructed as a tube attachment and being formed with an opening corresponding to the outlet end of the condensation tube and by means of which the tube attachment is mounted on the outlet end of the condensation tube, a first group of the wall parts in the tube attachment being disposed in alignment with the outlet end of the condensation tube, and a second group of the wall parts surrounding the first group thereof, the passages formed by the second group of the wall parts communicating laterally with the passages formed by the first group of the wall parts, the passages formed by the second group of the wall parts, at least at the upper ends thereof, communicating with the water volume. The advantages attainable with the invention are that the central steam flow through the passages formed by the wall parts of the tube attachment are not only finely subdivided, but also that the partial steam flows and the subdivided condensation bubbles are wetted and cooled inwardly from the outer periphery. In accordance with another feature of the invention, the second group of wall parts overlap the outlet end of the condensation tube in axial direction. This has advantages of providing strength and stability and, moreover, a greater cooling and wetting surface or area is afforded thereby. In accordance with a further feature of the invention, the first and the second groups of wall parts are formed of axially and radially extending plates defining sector-shaped passage cross sections. The central partial steam flows can thereby fan radially outwardly, thereby further increasing the cooling and wetting surface or area. In accordance with alternate additional features of the invention, whereby the cooling surface or area can be increased even further yet, the first and the second group of wall parts extend axially to the tube attachment, and wave-shaped metal sheets or plates are included which extend transversely to the axially extending wall parts and form zig-zag or serpentine passage cross sections. For reasons of strength and stability and for the purpose of attaining a definite axial inlet or entry of the cooling water from the water condensate of the condensation chamber into the tube attachment, there is provided, in accordance with an added feature of the invention, a tube attachment having a jacket tube enveloping the wall parts thereof. For reasons of strength and stability, it is advantageous, moreover, for the tube attachment to have a slide-on tube section which is connected to the wall parts and has an inner diameter corresponding to the outer diameter of the condensation tube per se. Thus, in accordance with a concomitant feature of the invention, a first group of wall parts is surrounded by a slide-on tube having an inner diameter corresponding to the outer diameter of the condensation tube at the outlet end thereof and being slidable onto the outlet end of the condensation tube, the second group of wall parts being secured to the slide-on tube at the outer peripheral surface thereof, the slide-on tube being formed with openings in the surface thereof through which the passages formed by the first and second groups of wall parts are in communication with one another. The tube attachment is thereby formed of two coaxial tubes, a slide-on tube, and a jacket tube, the inner space of the slide-on tube, disregarding the insertion opening for the condensation tube, being filled-in with the wall parts, and the peripheral space between the slide-on tube and the wall surface of the jacket tube being also filled in with wall parts. Although the invention is illustrated and described as embodied in blow-off device for limiting excess pressure in nuclear power plants, especially in boiling water- nuclear plants, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.