Patent Number: 046541896
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in or relating to high temperature reactors. More particularly, the present invention is concerned with medium power nuclear reactors in which the primary circuit is enclosed by a prestressed concrete pressure vessel or similar prestressed concrete reactor vessel, and this is supported on foundation walls. A reactor protection building surrounds the prestressed concrete reactor vessel, and is associated with a reactor auxiliary building. The reactor includes a reactor core which is made up of a bed of spherical full elements or pebble bed, which once through the reactor core under the force of gravity, and includes a charging installation for the introduction, as well as means for the withdrawal of operating elements. The pertaining charging conduits, pellet tubes, and exit pipes, as well as functional components for closing, metering, counting, distributing, and collecting of the operating elements are associated with the charging installation. The reactor also includes armored ducts which penetrate the prestressed concrete pressure vessel. 2. Background of the Art Feed apparatus, or similar charging installations, for nuclear power reactors of medium power in pebble bed reactors are known, such apparatus are designed in accordance with modular design principles, and contain functional components, which can be moved by drives, for the introduction, withdrawal, distribution, and sorting of fuel elements. The functional components exhibit bores for the passage of pellets, and they are set in a block, or a plate, which is respectively provided with connecting bores for the pellets. Such feed apparatus are shown in West German Utility Model No. 6,753,677; West German Auslegeschrift No. 1,589,532; and West German Offenlegungsschrift No. 2,357,426. The feed apparatus which is described in West German Offenlegungsschrift No. 2,357,426 is used, for example, in the nuclear power plant THTR-300, in which the feed station for the operating elements, fuel pellets and pure graphite pellets, is arranged in an auxiliary building and at a lower elevation than the high temperature reactor (HTR). A central withdrawal duct is provided in this HTR for the removal of the operating elements, and the duct leads to a burn-up measuring apparatus which is arranged in the charging room beneath the prestressed concrete pressure vessel. Because the fuel pellets are passing several times through the reactor core, until they have reached the desired final degree of burn-up, such a measuring apparatus is a necessity. For the same reason, a feed device is installed in the charging room, for conveying those operating elements which can still be used to the reactor core. The device is also used for fresh operating elements. In order to prevent damage of the operating elements due to impinging on the upper surface of the pebble bed or filling, the upper ends of the feed conduits exhibit a delay or deceleration apparatus. The state of the art further includes German Pat. No. 1,281,046 which also shows a feed apparatus for a so-called pebble bed reactor. The withdrawal and sorting device for the fuel pellets therein is also arranged beneath the reactor core and also exhibits a burn-up measuring apparatus. In accordance with the burn-up readings, the pellets are transferred again into the core, or they are separated from the cycle. SUMMARY OF THE INVENTION It is therefore a general object of the present invention to provide an installation for introduction and withdrawal of operating elements in a high temperature reactor of the type briefly described in the foregoing, which can be built and operated more economically than known installations. In accordance with one aspect of the present invention these objects are attained by an installation for the introduction and for the withdrawal of operating elements which comprises: (a) at least two input stations, with each input station being arranged within said reactor protection building and above said prestressed concrete pressure vessel; and for each input station, at least one distributor block operatively connected thereto; (b) a plurality of charging hatch blocks, with at least two charging hatch blocks being operatively connected to a pertaining distributor block; and each charging hatch block having means for containing functional components for closing, metering, and counting, and said means being adapted to be positioned on said prestressed concrete pressure vessel ceiling; and means operatively connected within a corresponding armored duct, said means including a selector, and charging conduits operatively connected thereto; (c) said charging conduits being shaped as helical conduits, and each charging conduit being adapted to be followed beneath said prestressed concrete pressure vessel ceiling by at least one inlet pipe which is adapted to be disposed in a random or meandering configuration; (d) a plurality of exit conduits, discharge separators, and singularizers, with pertaining exit conduits being operatively connected in said prestressed concrete pressure vessel bottom to pertaining ones of said armored ducts, and wherein in each pertaining exit pipe a pertaining scrap separator is operatively connected to at least one pertaining singularizer; (e) a first exit hatch block arranged outside of said prestressed concrete pressure vessel and within said foundation walls, said first exit hatch block being connected to a pertaining scrap separator and a shielded exit hatch channel, said channel being adapted to pass through said reactor protection building, and said first exit hatch block being adapted to contain functional components for shutoff and counting; (f) a second exit hatch block arranged outside of said foundation walls and inside said reactor protection building, and adapted to be operatively connected to said exit hatch channel and at least one exit station operatively arranged in said reactor auxiliary building, said second exit hatch block being adapted to contain functional components for metering, counting, and shutoff; and (g) wherein pertaining charging hatch blocks and said first exit hatch block are respectively equipped with closing devices, said devices being of at least two different configuration types, whereby for charging and withdrawal operations standard devices are used, and for isolating/closing of the primary cycle, for the control of the non-standard conditions, special devices are used. In accordance with the present invention, several important advantages are gained in such high temperature reactor with charging installation for introduction and withdrawal of operating elements. Thus, a delay or deceleration apparatus for operating elements is obviated at the entry into the reactor core, due to the particular configuration of the various charging and inlet pipes and the conduits. The utilization of selection switches allows the reduction in number of required functional components. The mechanical elements of the selection switches, as well as the elements of the combined singularizers/scrap separators, are integrated in a practical manner in the prestressed concrete pressure vessel because they are interiorly arranged in armored duct passages, in such a way that problems generally do not arise during charging, or similar feeding operations, and during removal operations with respect to the sealing of the primary circuit. The first exit hatch block, for one is arranged below the pertaining level of the prestressed concrete pressure vessel and, accordingly, is easily accessed. It is also located within the space enclosed by thick foundation walls, and these provide a shield for it at the same time. The input stations are also installed outside of the prestressed concrete pressure vessel, such that a simple pipe compensation is possible for the succeeding pebble tubes and similar ducts. The conduits which are subjected to pressure during normal operation are arranged within the reactor protection building. Of particular advantage is the utilization of various shutoff devices at the functional components. For operational charging and withdrawal sequences or procedures, one can use armatures and similar equipment, for example, ball cocks, ball valves, and the like. These close the charging hatch portion at the commencement in the distributor blocks and at the terminus in the charging blocks. In the case of incorrect start-up, or in the case of failure of one of these armatures, gas in the hatch is set free and passes into the reactor protection building because the entire input assembly is arranged in this building. Further standard armatures are adapted to close the exit hatch stretch between the first and the second exit hatch block. In the latter is done the withdrawal of the operating elements from the reactor protection building into the reactor auxiliary building in which the exit station is disposed. When gas is set free into the reactor auxiliary building, due to control errors or due to failure of an armature, only the contents of a hatch is released. All pebble tubes which lead out of the prestressed concrete pressure vessel are adapted to be directly closed by special armatures at the interface locations of pertaining passages through the pertaining vessel walls, for example, double-seat closing armatures and similar shutoff valves. These armatures ensure the safe isolation of the primary circuit even in the case of disruptive situations, they are designed in accordance with disruption-incident requirements and similar fail-safe considerations, and they are arranged within the charging hatch locks and in the first exit hatch block. The configuration of all components which follow in line behind the special armature, beginning at the prestressed concrete pressure vessel, is done in accordance with the operational requirements. The German Patent Application No. P 3,344,527.3 describes a high temperature reactor in which the charging installation for introduction and withdrawal of operating elements can be used. The subject matter of this application is incorporated herein.