Abstract: A process is provided for the long term shutdown of a high temperature nuclear reactor comprised of a pile of spherical fuel elements in a core by means of a neutron absorbing absorber material wherein the absorber material consisting of spherical absorber elements is introduced in the core of spherical fuel elements in the form of a column, but wherein the intermixing of the absorber material with the fuel elements is prevented. An apparatus for practicing the process is also provided comprised of a graphite side reflector concentrically surrounding a circular cylindrical core filled with a pile of spherical fuel elements of a high temperature nuclear reactor, into which at least two nose shaped projections distributed uniformly about the circumference radially project, with each of the projections comprising a vertical cavity to contain the absorber material. The vertical cavity is located in the vicinity of the core in the area of the frontal side facing the core of each projection.

Abstract: A gas cooled nuclear reactor may have a stationary pile of spherical operating elements. The reactor may be controlled and shut down by absorber rods displaceable in channels of the side reflector. The neutron sources required for the safe start-up of such pellet pile reactors, which in the case of higher capacity pile reactors are installed in bores of the side reflector, are arranged in the stationary pile, where they are more effective and do not occupy positions in the side reflector. They may be located in one or more graphite elements having the same diameter as the operating elements. These elements may be introduced and removed into and from the core together with the operating elements and remain stationary in operation.

Abstract: A roof reflector comprising at least three individual layers of tapered layer elements combined in the form of vertical columns. Each column rests on a block column of the lateral reflector. Individual elements are secured by wedges and dowels to permit vertical column movements without constraint. The top and bottom layers comprise gas collector spaces communicating with each other by passage openings in the middle layer. In the top and bottom layers are also slot-shaped passage openings leading to an from the collector spaces. Preferably, they are radially offset relative to the passage openings in the middle layer to obtain good gas mixing as it rises through the reflector.Such a roof reflector is useful for avoiding roof reflector element damage if one element is vertically displaced relative to an adjacent element. The roof elements are carefully designed to achieve this end and maintain cover utility.

Abstract: A shutdown system for a high temperature nuclear reactor where absorber material elements in the form of balls pass from an elevated reservoir into a vertical channel formed by aligned vertical cavities in horizontal, nose-shaped projections from the side reflector. The balls are transported back to the reservoir by way of a conveyor device. It must be insured that even in the case of accidents the absorber balls arrive in the cavities and that a rapid return of the absorber balls into the reservoir takes place. For the purpose, the reservoir is provided with an automatically-actuated and controllable device for releasing an opening between the reservoir and the vertical channel feed line. Below the channel is a removal tube terminating in a housing and arranged to form a pile of the absorber balls which seals the removal tube. To return the absorber balls, a metering gas acts on the pile and brings the absorber balls to a carrier gas.

Abstract: An absorber rod for nuclear reactors with a pile of spherical fuel elements, which is inserted directly into the pile, in order to affect the prevailing neutron flux by absorber material located in an annular gap between two concentric cylindrical rod elements. The absorber rod has concentric rod elements arranged in pairs, a common rod tip and common connecting pieces. The rod elements are cooled by flow of gas and the inner cylindrical rod element performs the support function, i.e., it absorbs and transmits forces and moments originating in the movements of the rod during insertion and extraction.

Abstract: A nuclear reactor installation with a simple configuration includes a transport container which may be placed on the cover of the cavity. The transport container bottom overlaps the cover access opening. A vertical displaceable pebble conveyor line extends from the pebble pile surface to the transport container interior. A blower is located between the transport container and the reactor. The blower suction line is connected to the transport container interior and the blower pressure line leads into the reactor vessel.

Abstract: A nuclear power plant with a gas cooled high temperature reactor, installed in a prestressed concrete pressure vessel with the operational and decay heat removal systems. The prestressed concrete pressure vessel has a thermal protection system, with a thermal insulating layer and a liner cooling system. The liner cooling system, which is includes water carrying cooling pipes, which along with intermediate heat exchangers and cooling water pumps make up a closed intermediate cooling loop used for removal of the decay heat in case a failure of the decay heat removal systems. The elements of the invention assure an adequate water flow for the removal of decay heat in the liner cooling system in any situation, i.e. such that the decay heat may also be removed by natural convection. These element insure a sufficient driving pressure differences and minimize pressure losses in the intermediate cooling loop.

Abstract: A nuclear power plant with a high temperature reactor located eccentrically in a prestressed concrete pressure vessel with spherical fuel elements for a capacity of 100-300 MWth intended primarily for power generation. The plant is inherently safe even in extreme accidents due to special devices for removal of decay heat. It is provided that upon a failure of the operational decay heat removal devices, decay heat is removed through a liner cooling system of the prestressed concrete pressure vessel. The liner cooling system is connected to a water-filled elevated reservoir by an external circulation loop. The elevated reservoir is connected to a further heat sink through a recooling circulation loop. It is possible to feed water into the elevated reservoir.

Abstract: A gas-cooled high temperature reactor having a core filled with spherical fuel elements is provided comprising a graphite side reflector including at least one nose-like projection comprised of a plurality of graphite nose stones stacked one upon the other, said nose stones each including at least one vertically disposed continuous cavity aligned with at least one vertically disposed continuous cavity in adjacent nose stones, said cavity adapted to receive discrete absorber material elements introduced into the reactor core, said nose stones further including at least one vertically aligned continuous gap which extends into said nose stones from a front portion thereof and is aligned with a corresponding continuous gap in adjacent nose stones, communication between said continuous gap and said cavity being prevented, said nose stones also comprising in top and bottom surfaces thereof sealing means which enable adjacent nose stones to be stacked in a manner sufficient to seal said at least one cavity in a gas-

Abstract: A low capacity nuclear reactor with spherical fuel elements laid out in an underground configuration and characterized by a compact structure and the far-reaching elimination of active operating installations, such as a charging apparatus, gas purification installations and control systems. The reactor is particularly suitable for generation of heat for heating purposes. The graphite reflector surrounding the pile of fuel elements on all sides includes layers of spherical graphite elements with a diameter equal to that of the fuel elements. The poured part of the graphite reflector and the pile of fuel elements are located in a metal core vessel made of lattice work or perforated sheet metal and capable of supporting the entire weight of the graphite and fuel elements. The mesh or the holes of cage-like core vessel are smaller than the diameter of the spherical elements.

Abstract: A gas-cooled high temperature reactor is provided having a core filled with spherical fuel elements, in combination with a graphite side reflector including at least one nose-like projection protruding radially into the reactor core from said graphite said reflector, the at least one nose-like projection including at least one vertically disposed cavity adapted to receive discrete absorber material elements introduced into said reactor core as well as a vertically disposed continuous opening which permits communication between said cavity and the core of the reactor, said opening having a maximum width adjacent said cavity which is less than the minimum dimension of said discrete absorber material elements in order to prevent passage of said elements into said continuous opening from said cavity.

Abstract: In a nuclear reactor installation with a small high temperature reactor (26) all of the components of the primary loop, together with the control and shutdown installations (82, 92, 114, 116; 194, 198, 200) are located inside a steel pressure vessel (16) and may be installed and dismantled from above. This makes an economical subterranean construction possible.

Abstract: A concrete reactor pressure vessel for a low capacity, gas cooled nuclear reactor is provided. To assure the safe containment of the cooling gas in an economical manner and to remove the heat generated in the reactor core, the pressure vessel is equipped with reinforcing or prestressing elements. Cooling gas transfers its heat to a heat exchanger means consisting of the liner of the pressure vessel and cooling pipes mounted on the concrete side of the liner with water flowing through the cooling pipes. The heat exchanger comprises on the secondary side at least two mutually independent systems, each provided with collector pipe means located outside the reactor pressrue vessel for the forerunnings and afterrunnings of the cooling water. Each cooling pipe is connected by means of an inlet and a drain line with the corressponding collector pipe means.

Abstract: The invention relates to a gas cooled high temperature reactor located in the cavity of a pressure vessel, with spherical fuel elements, and removal apparatus for fuel elements. The latter is made of at least one ceramic pebble outlet tube extending through the graphite structural parts of the nuclear reactor (bottom reflector, bottom layers) and a number of metal pebble outlet tubes installed through the bottom of the pressure vessel. They are arranged coaxially in the liner of the passage through the vessel. To be able to dismantle the metal pebble outlet tubes, they are constructed of several releasably interconnected tube segments. Between the uppermost tube segment and the corresponding ceramic pebble outlet tube a compensating tube is provided and connected with the tube segment by means of a sliding joint. The other end of the compensating tube is fastened to the thermal bottom shield.

Abstract: A nuclear power plant (heating plant) with a helium cooled high temperature reactor with spherical fuel elements, located in a cylindrical prestressed concrete pressure vessel, suitable for supplying heat (for local or remote heating or the generation of process steam) with a capacity of approximately 50 to 300 MWth. The high temperature reactor core is located out of center in the prestressed concrete pressure vessel, with at least two heat exchangers installed adjacent and offset in the upward direction relative to it. The heat exchangers are each connected on the secondary side to an intermediate circulation loop including an intermediate heat exchanger and circulating pump, and have an auxiliary circulation loop with a recooling system connected in parallel with them for the removal of decay heat. The auxiliary loops are closed in normal operation.

Abstract: The invention relates to a nuclear power station for a gas cooled high temperature pebble bed nuclear reactor. The nuclear power station is characterized by a combination of features, whereby the system inherent properties of a high temperature reactor are utilized to make possible the economical operation of a nuclear power station of medium capacity (300-600 MW.sub.el) while maintaining a high standard of safety. The characteristics comprise a reactor protection building equipped with pressure relief means in combination with filters, several auxiliary cooling systems separate from the operating cooling systems for the removal of decay heat in the case of accidents, and the utilization of a liner cooling system for the prestressed concrete reactor pressure vessel to assure the removal of the decay heat in case of a failure of the auxiliary cooling systems.

Abstract: A single loop nuclear power plant with a helium cooled high temperature reactor for generation of electric current, designed for a capacity of 1-5 MWe. The plant, which in addition to the high temperature reactor includes a gas turbine assembly and a heat exchange apparatus, is housed in two pressure vessels located above each other and connected in a releasable manner. The lower pressure vessel contains the high temperature reactor and is charged with the primary gas. The other circulation components are located in the upper pressure vessel which is filled with a protective gas. The gas turbine, the radiators, the high temperature compressor, the intermediate radiators, and the low pressure compressor, are arranged above each other in this sequence and aligned with the high temperature reactor. the recuperator is laterally arranged. A generator may also be located in the upper pressure vessel or in a container set upon the upper pressure vessel.

Abstract: A gas cooled high temperature nuclear reactor utilizes an independent cooling system for the safety enclosure surrounding the reactor vessel. The cooling system comprises means for circulating cooling medium at least on the reactor side of a concrete safety enclosure shell and a separate closed cooling loop for circulation of separate cooling medium through a reservoir of the first cooling medium and to the outside of the entire nuclear reactor installation.

Abstract: A nuclear reactor installation with a high temperture, gas cooled nuclear reactor supported in a cavity on a segmented bottom plate held by a centered point of fixation. The first heat exchangers of the primary circulation loop are arranged in the cavity around the nuclear reactor, with the associated first blowers being supported in first passages of the pressure vessel roof. The second heat exchanger for the removal of the decay heat are arranged similarly, with the associated second blowers located in passages of the pressure vessel bottom. The blowers are equipped with contactless magnetic bearings for the rotors. The drives of the core rods and the reflector rods are designed for a banking operation. Simultaneously, the side reflector is supported by means of radial supports on the thermal side shield elastically and secured against rotation. The measures described provide a simplified configuration without affecting safety.

Abstract: A roof reflector for a small, high temperature reactor with a hot gas collector space arranged above the roof reflector comprises a side reflector arranged under the roof reflector around a reactor core with a thermal side shield arranged around both the side reflector and the roof reflector. The roof reflector is composed of individual, mutually supporting, wedge-shaped graphite blocks and is supported on the thermal side shield by means of springingly elastic fastening elements in a radially expandable manner.