Patent Number: 041394135
Section: summary

The invention relates to a blow-off device for limiting excess presure 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 outflow or outlet end thereof is immersed in a volume of water (condensate) in a condensation chamber or receptacle having a gas cushion located in a space above the volume of water, and the upper inflow or 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 outflow end of the condensation tube, for stabilizing the condensation, being provided with wall parts forming passageways extending in axial direction, and stepped from one another at the forward end thereof in flow direction of the steam, 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. In FIG. 5 thereof, the condensation tube narrows down due to tube sections of decreasing diameter that are slid one within another, ring gaps remaining free in the zone in which the tube sections overlap. In this construction, the central steam flow is not yet finely subdivided enough. It has also become known heretofore from German Published Non-Prosecuted Application DT-OS 2 457 901, to dispose in the interior of the condensation tube, a framework extending parallel to the axis thereof and formed of wall parts extending parallel to the axis of the condensation tube. A finer subdivision of the steam flows into partial steam flows is provided thereby, however, consolidation of the steam bubbles and consequent formation of larger bubbles can, nevertheless, continue to occur at the tube end because the travel time of the individual partial steam flows within the passages formed by the wall parts is virtually the same. It is an object of the invention to provide a blow-off device for limiting excess pressure in nuclear power plants, especially in boiling water-nuclear power plants which is markedly improved over heretofore known devices of this general type and which, more specifically, reliably avoids a consolidation of steam bubbles in vicinity of the end opening of a condensation tube when the steam flow has been finely subdivided into individual partial steam flows. 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 outflow end thereof 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 an upper inflow end of the condensation tube extends out of the volume of water and is connectible to a source of steam that is to be condensed or a steam-air mixture outflow end of the condensation tube, for stabilizing the condensation being provided with an assembly of wall parts forming passageways extending in axial direction for subdividing the steam flow and bubbles produced in the volume of water, the passageways of the assembly of wall parts being stepped in axial direction at both axial ends of the assembly of wall parts. The advantages attained with the invention are primarily that not only the outlet locations of the partial steam flows and bubbles are shifted or offset axially and radially relative to one another but also the inlets thereof into the passageways formed by the wall parts, so that, longer subdivision sections and considerably greater travel time differences for the individual partial steam flows are thereby produced. In accordance with another feature of the invention the assembly of wall parts constitutes a plurality of tubes in mutually stepped disposition. Such a construction is capable of being realized especially simply from the production-engineering standpoint. In accordance with additional alternate features of the invention, the plurality of tubes are in the form of a tube bundle or are telescoped one within another. In accordance with a further feature of the invention, the telescoped tubes are spaced from one another, defining annular zones therebetween, and respective intermediate metal sheets are disposed in the annular zones. In accordance with an added feature of the invention the plurality of tubes have mutually stepped configurations at the axial inflow and outflow ends thereof that are mirror-images of one another. In accordance with yet another feature of the invention, the mutually stepped disposition of the plurality of tubes has a substantially double conical structure and is formed by at least one central tube of relatively maximal length and annular zones with stepped tubes of decreasingly shorter relative length disposed around the central tube, one substantially conical end of the structure extending out of the condensation tube, the tubes of the structure extending farthest out of the condensation tube being also the tubes extending farthest into the condensation tube. In accordance with yet a further feature of the invention, the mutually stepped disposition of the plurality of tubes has an inflow half disposed and retained inside an outflow chamber defined by the lower outflow end of the condensation tube, the outflow chamber having a larger diameter than at least a part of the inflow end of the condensation tube located adjacent the outflow end thereof, the outflow chamber being further defined by a terminating annular wall of the lower outflow end, the terminating annular wall being connected to the upper inflow end of the condensation tube. In accordance with an additional feature of the invention, the intermediate metal sheets in the annular zones are formed as axially oriented, circular wave-shaped metal sheets subdividing the respective annular zones and serving as spacers. In accordance with a concomitant feature of the invention, a tube bundle is received in the passageway of the innermost of the telescoped tubes, the innermost passageway being subdivided by the tube bundle. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a blow-off device for limiting excess pressure in nuclear power plants, especially in boiling water-nuclear power 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.