Patent Number: 044951477
Section: summary

The invention relates to a heat-retarding closure system for pressure relief openings of partitions, especially of those in nuclear reactor buildings, in the area where the main coolant nozzles of the reactor pressure vessel penetrate the biological shield, with lightweight construction closure elements which can be pushed outwardly out of their anchors by an overpressure on the reactor side. It has become known through German Published, Prosecuted Application DE-AS No. 21 60 991 to use a closure system for pressure relief openings in the biological shield of a nuclear reactor pressure vessel, in which several shielding chambers filled with shielding material are provided in the biological shield which are spaced around the periphery of the reactor pressure vessel and are sealed gastightly to the outside by glass panes of a predetermined blowout pressure. A similar closure system is shown in German Published, Prosecuted Application DE-AS 27 19 923, in which the shielding elements closing the relief openings are formed of a lattice structure, the grid meshes of which are filled with granular shielding material. The grid structure is anchored in the opening of a partition by means of a frame, and the grid meshes are closed by sheet metal panels which are pushed out together with the granulate filling upon the occurrence of a given overpressure. The present invention also starts from lightweight-construction closure elements which can be pushed outwardly out of their anchors by overpressure from the reactor side. However, the closure elements are particularly heat-retarding. They are disposed especially in the area where the main coolant nozzles of the reactor pressure vessel penetrate the biological shield. In case of a postulated fracture (improbable per se) of a main coolant line, coolant would flow through a leak fixed in its size at a certain area, e.g. 200 cm.sup.2, between a double pipe and the main coolant nozzle into an annular space formed by the reactor pressure vessel and the biological shield. The overpressure built up thereby must be relieved in inherently safe fashion. Together with the outer supporting shield to which the supporting structure of the reactor pressure vessel is mounted and anchored, the biological inner shield forms the entire biological shield. However, the objective is not merely the relief of possibly occurring overpressure; in addition the nozzle space must be insulated against heat removed to the outside. The nozzle space insulation thus forms the separation of the area under compression from the annular gap which receives its geometry or shape from the supporting shield and the inner shield. It is accordingly an object of the invention to provide a heat-retarding closure system for pressure relief openings of partitions, especially in nuclear reactor buildings, which overcomes the hereinafore-mentioned disadvantages of the heretoforeknown devices of this general type, and through which a convection-tight closure of the pressure relief openings is made possible and which has the same effectiveness with regard to its heat retardation as the adjoining heat retarding system. Other requirements which the invention is intended to meet are the following: Blowout pressures for the closure system that are precisely determinable mathematically and experimentally; construction of the closure elements and closure system in a manner which makes cocking or canting within the pressure relief opening during the pushout process impossible; and finally, as lightweight a construction of the closure elements as possible which, when tripped, are pushed out of the pressure relief opening, in order to prevent damage to components of the environment. With the foregoing and other objects in view there is provided, in accordance with the invention, a heat retarding closure system for partitions having pressure relief openings formed therein especially in nuclear buildings where main coolant nozzles of a reactor pressure vessel penetrate a biological shield, comprising lightweight construction closure elements having a side facing the reactor and anchors for holding the closure elements, the closure elements being pushable out of the anchors by an overpressure in a given pressure difference direction on the reactor side, and an outer sealing blowout skin, the closure elements being in the form of heat-retarding cassette inserts having a front surface with a peripheral shearing edge formed thereon resting against the blowout skin, and the blowout skin having a given thickness in the given pressure difference direction enabling the cassette insert to shear off the blowout skin and be pushed out of the anchors or seat when a given permissible pressure difference is at least reached or exceeded. In accordance with another feature of the invention, the cassette insert contains retarding material in the form of mineral fibers. In accordance with a further feature of the invention, the cassette insert is formed of metal and includes layered and mutually spaced apart retarding foils in the interior thereof in the retarding direction for retarding pressure in the pressure difference direction, the foils forming retarding cells. In accordance with an added feature of the invention, the anchors are in the form of an expendable partition seat having an outside and an inside and being conically shaped from the inside to the outside or truncated pyramoidally shaped. In accordance with again another feature of the invention, the cassette insert has a partition area and the blowout skin is in the form of a glass blowout pane being clamped and sealed to the partition area. In accordance with again a further feature of the invention, the blowout skin is a metallic blowout foil. In accordance with again an added feature of the invention, the cassette insert includes a peripheral sheet metal envelope having a front surface and the shearing edge projects from the front surface of the envelope. In accordance with a concomitant feature of the invention, one of the foils is a front foil forming the shearing edge, the front foil having a doubly chamfered rim being substantially V-shaped and having a relatively greater thickness of its wall as a pressure foil than the others of the foils. The advantages achievable by the invention are to be seen primarily in that the cassette inserts are lightweight elements of high heat retarding ability, through which pressure relief openings are now made possible even in the nozzle space area, particularly in pressurized-water reactors. 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 heat-retarding closure system for pressure relief openings of partitions, especially in nucler reactor buildings, 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.