Patent Number: 042971675
Section: summary

The invention relates to a nuclear reactor installation with a concrete cell disposed beneath the earth of a hill for enclosing activity-carrying components. Such a nuclear reactor installation is described, for example, in the German-language journal, "Atomwirtshaft", July/August 1975, pages 363 to 366. No details are given therein, however, regarding the spatial construction thereof. Furthermore, a paper with the same theme entitled "Underground Siting of Nuclear Power Reactors" has appeared which had been prepared for a Symposium in Vienna. In this paper, a nuclear reactor installation is illustrated in FIG. 1 thereof wherein not only the nuclear reactor but also the machinery building supplied thereby are disposed in the ground or earth. The construction of the machinery building is only hinted at, though. It is apparent, nevertheless, that a light structure was involved having a volume of at least the same order of magnitude as that of the concrete cell with the activity-carrying components. It is accordingly an object of the invention to provide a nuclear reactor installation of the foregoing type which is improved from the standpoint of safety engineering, at relatively low expense, over corresponding installations of the prior art. It is a further object to provide an installation of such construction, that will be less susceptible to disturbances and, in the event disturbances should occur, will be less sensitive to consequential damages. With the foregoing and other objects in view, there is provided, in accordance with the invention, a nuclear reactor installation having a concrete cell disposed beneath the earth of a hill for enclosing activity-carrying components comprising at least one additional concrete cell (auxiliary cell) disposed in the earth separated from the first-mentioned concrete cell (central cell), the additional concrete cell being one fortieth or less of the volume of the central cell, preferably one two-hundredths thereof, and being at least predominantly of shell-like construction, and including equipment of use for the nuclear reactor installation, such as secondary, emergency or auxiliary equipment, received in the additional concrete cell. This is seemingly at variance with the demand for limited expense, especially since one could believe or expect that anyway, through the underground type of construction in the earth of a hill, virtually complete protection at least against consequential damage from disturbances is provided. Actually, however, the division of secondary, emergency or auxiliary equipment into further separated concrete buildings permits first a complete exploitation of the increased security or safety connected with the underground type of construction, as explained hereinafter in clearer detail. By "separated" there is meant, in this connection, that the individual concrete buildings are "floatingly" disposed, so that they can follow movements of the earth or ground independently of one another. This can be especially ensured by means of intermediately disposed pipes or channels which are provided with movable connectors, as will be described hereinafter. Such a separation, in fact, exists also for the machinery building according to the hereinaforementioned paper prepared for the Viennese Symposium. This machinery building is not only considerably larger, however, than the auxiliary cells according to the invention. It is also constructed as a purely rectangular building with flat walls, and is in no way of shell-like construction. The conventional machinery building is therefore capable of little resistance against outer and inner pressures. This is essentially the point of the invention, as will also be explained further hereinafter. In accordance with another feature of the invention, the additional concrete cell is connected in a line through which energy is removed from the hill, and valve means are disposed in the additional concrete cell for closing off the energy removal line. In this manner, success is achieved in reliably closing off the inclusion or enclosure provided by the central concrete cell of the activity-carrying components in the sources of the line for, in contrast to an arrangement of valves within the central cell, it is impossible that valves in the auxiliary cell would be damaged or otherwise rendered inoperative due to disturbances in the central cell. The inclusion or enclosure especially reliably provided by the underground type of construction is thus, in accordance with the invention, additionlly protected through the disposition of additional auxiliary cells for the lines which extend out of the central cell. The aforementioned embodiment of the invention is especially advantageous if the central or first-mentioned cell is part of a so-called double-containment. Thus, in accordance with a further feature of the invention, the first-mentioned or central concrete cell is spaced from and surround a tight containment for enclosing activity-carrying components and defines therewith an annular space, the line extending from the containment and, in addition to the valve means in the additional or auxiliary concrete cell, further means for provided in the containment and/or in the annular space for closing off the line. The further closure means in the containment can be formed in a pressurized water reactor by the steam generating tubes which, as is generally known, separate the activated primary cooling water from the virtually activity-free secondary coolant. Additional closure valves can also be provided, however, and in fact not only inside the containment and outside the central cell, but rather, in the annular space between the containment and the central cell, so that maximal security against the liberation of activity-carriers is provided. The additional or auxiliary concrete cell, in accordance with yet another feature of the invention, has an outlet extending into the earth of the hill, the outlet having a cross section of at least 1 m.sup.2. What is achieved is that also if a rupture of the line were to occur in the auxiliary cell, no overload is conceivable which would cause a too-high pressure in the interior of the auxiliary cell and thereby cause it to burst. The outlet can be constructed as a blow-down line that is provided with a unilaterally operating closure member disposed in the interior of the auxiliary cell. By closure members there is meant not only ckeck valves but also, for example, bursting or rupture discs which, due to a bracing construction, have a lower response pressure in the one direction than in the other. The blow-down line should terminate in a gravel pile or in pipes leading to the interior of the hill. The introduction of gases and vapors which would otherwise cause excess pressure, can thereby be facilitated, because the permeability of the hill materal is limited. Furthermore, a secondary safety valve can be connected to such a blow-down line in order, for example, to attain relief when excess pressure exists in the line that is to be closed off. By means of such a blow-down line, energy, for example, in the form of steam which has been produced during emergency cooling of the nuclear reactor, can be removed. In accordance with another feature of the invention, a plurality of the additional or auxiliary concrete cells are spatially distributed around the first-mentioned or central concrete cell, the auxiliary cells being connected in respective lines thereof which energy is removed from the hill, and valve means are included which are respectively disposed in the auxiliary cells for closing off the respective energy removal lines. Preferably, the number of auxiliary cells correponds to the number of lines, it being advantageous for steam power plants to conceive of the live steam line, on the one hand, and the feedwater line, on the other hand, as one pipe system which passes through a common auxiliary cell. Besides such special auxiliary cells provided for the closure, other auxiliary cells may be provided wherein exclusively emergency equipment, for example, for emergency cooling, are accommodated, or auxiliary equipment, for example, groundwater filtering equipment, if these are to be especially safety housed independently of the central cell. In accordance with a further feature of the invention, the auxiliary cell is connected in a line extending to the central cell for removing energy from the hill, the line extending through movably sealed pipes. What is attained thereby is not only that the line per se remains free from the pressure of the earth and from movements thereof, but rather also, that accessibility for inspections is provided. Channels built with the aid of such pipes, such as concrete pipes, for example, wherein the lines run, should also, at least by creeping, be accessible for inspection personnel. The pipes are advantageously of pressure-tight construction, the pressure tightness being not only determined with respect to the weight of the earth located above the pipes, but also with respect to the conceivable inner pressure, which might be produced in the event of a line rupture. The elastic joint connectors provided at the connecting locations cannot only be obtained through the hereinaforementioned seals but also, under suitable conditions through the construction of the connecting locations per se, for example, in the form of universal or ball-and-socket joints. Through the movable sealing of the pipes, which can be effected with yieldable sealing materials, such as rubber or with impermeable coverings in the form of clay strata or also tarpaulins or sheets formed of synthetic or plastic material, assurance is provided that relative movements, at least within limits, are possible, as may be produced by settling of the earth or by earthquakes. Notwithstanding these seals, and in accordance with an added feature of the invention, the pipes and the connecting openings produced accordingly at the central and the auxiliary cells are disposed above the maximal groundwater level or water table. In accordance with an additional feature of the invention, the auxiliary cell is accessible only from the outside of the hill and not, however, from the central cell. What is achieved thereby is that the effects of disturbances in the interior of the central cell cannot have any effect upon the devices of the auxiliary cell. On the other hand, it should also not be possible that through the access to the auxiliary cell, any disturbances should be produced in the central cell which could release activity, as a result of military action or sabotage, for example. In accordance with another feature of the invention, a well extends from the auxiliary cell into groundwater in the earth, which will usually be present underneath the nuclear reactor installation. With such a well which is disposed in the auxiliary cell and protected therein uninfluenced by the activity in the central cell, the groundwater level can be influenced so as to prevent a further spread or distribution of the radioactivity. In addition, such a well can also serve for emergency and/or aftercooling. In accordance with a further feature of the invention, a plurality of redundant, spatially separated emergency cooling devices are mounted in the auxiliary concrete cells and a system of lines extending out of the central cell and associated with said emergency cooling devices. The hill serves in devices according to the invention for enclosing or at least for delaying activity which can hypothetically occur by failure (a) of the primary components of the nuclear reactor, PA1 (b) of the containment enclosing these primary components, and PA1 (c) of the concrete building of the central location. In accordance with the invention, another control is provided, however, also for this, in all probability, impossible situation, from a practical standpoint. Thus, impermeable partitions, especially formed of clay, are disposed in the hill for separating regions of varying activity in case of a disturbance, the auxiliary cells being disposed in regions of minimal activity separated by the partitions. What is attained thereby is that the auxiliary cells are still relatively well accessible even in the event of the most unlikely disturbance, so that, for example, the inclusion or enclosure of the activity in the region of the auxiliary cells, it controllable somewhat through these extending lines and is accessible for maintenance. Further in accordance with the invention, the lines extend through recesses formed in the partitions, the recesses being considerably smaller than corresponding dimensions of the auxiliary cells, so that the necessary seals for the partitions are small. In accordance with an added feature of the invention, the partitions cover connections to the auxiliary cells so as to effect an additional sealing action. For the case of a live steam line and/or a feedwater line that have already responded or been activated, a conical attachment location with a closure valve mounted thereat is provided because, with such a conical fastening location, a mechanically stable construction is able to be well united with a pressure-tight closure. For the same reasons, there is provided in accordance with an additional feature of the invention, that the line extends to the central cell and is formed as a double-wall pipe. The effect thereon is that in the event of a break in the line, the pressure released to the outside only acts upon the double-wall pipe which can be constructed so as to be adequately pressure-tight, without great expense, whereas otherwise one would have to contend with pressure increases in the concrete channel which could cause consequential damage. As noted hereinbefore, the auxiliary cells should only be accessible from the outside in order to avoid effects from the region of the central cell or into that region. For the same reason, and in accordance with yet other features of the invention, the auxiliary cells are connected only through pressure-free access means or through pressure-tightly closed sluice passages or locks. In accordance with yet a further feature of the invention, mechanically sturdy baffle plates are provided for preventing penetration of solid material into the auxiliary cells and the lines respectively connected thereto. Although the auxiliary cells with their small volume, also during unified spatial removal from the central cell, are generally covered to such a height by the earth of the hill that mechanical effects from the outside are unlikely, it can be advantageous for the earth of the hill located above the auxiliary to have a tight cover layer or stratum that is bridged by a closable outlet or discharge line. The closable discharge lines ensures pressure relief during blow-down of steam from the auxiliary cell, which is produced during a line break, because an air cushion present in the hill can be pushed out without raising the cover layer of the hill. The instant application is one of three application simultaneously filed by the applicant, related generally to the same subject matter although directed to different inventions therein. Other features which are considered as characteristics for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in nuclear reactor installation, 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.