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: A nuclear reactor installation located in the cavity of a pressure vessel comprises a nuclear reactor with a core traversed from top to bottom by a cooling gas, a plurality of main loops consisting of heat exchangers and blowers, together with auxiliary loops for the removal of decay heat. According to the invention, the auxiliary loops contain no heat exchangers but a bundle of heat pipes independent of each other, the heat absorbing part of which is arranged in the pressure vessel cavity. As a heat sink, an external cooling water loop is provided for each bundle of heat pipes in which water is circulated. The cooling water is recooled in a cooling tower. In a preferred embodiment the heat transferring part of the heat pipes of each bundle terminates in an external water reservoir to which the cooling water loop is connected. For a certain period of time, in case of a sufficient volume of water, the decay heat may be removed only by evaporation from the water reservoir.

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.

Abstract: A nuclear reactor plant housed in a steel pressure vessel with a small high temperature reactor, together with a steam generator arranged over said reactor and with at least two circulating blowers connected in parallel with each other and following the steam generator in line and is provided with a decay heat removal system located in the primary loop. This system is arranged above the steam generator and a shut-off device is provided between the two component. The shut-off device, which may actuated both passively--by difference pressure--and actively, by means of a drive, is designed so that in normal operation no hot gas may enter the decay heat removal system. In the decay heat removal mode the hot gas is conducted into the decay heat removal system and the steam generator is closed off the hot gas. Simultaneously, the cold gas coming from the decay heat removal system is returned through the steam generator or a gas conduit parallel to it, to the reactor core.

Abstract: A nuclear reactor plant housed in a steel pressure vessel comprises a small high temperature reactor and a He/He heat exchanger located above the reactor, preferably followed by two circulating blowers connected in parallel. The installation further comprises at least one decay heat removal system, following in line the He/He heat exchanger in the direction of flow and with the entire flow of primary helium constantly flowing through it. In a preferred embodiment, the He/He heat exchanger is made up of two concentrically arranged coil bundles connected in succession, through which both the primary and the secondary helium are flowing in opposing directions.

Abstract: A high temperature pebble bed nuclear reactor having a medium power capacity of 300 to 500 MW.sup.e is equipped with two different shut-down arrangements comprising reflector rods used exclusively for scram. The total shut-down reactivity of the reflector rods is proportioned in order to prevent the excessive cooling of the reactor core folowing scram. In this manner, the reactor core is rendered subcritical (in the event of accidents, for example, or at the beginning of any operating state) yet capable of returning to criticality at a reduced level of temperature and power output following the removal of heat. The use of all of the reflector rods for scram is effected only in the event of reactivity accidents. For all other scram incidents, only a portion of the reflector rods are used.

Abstract: A low capacity nuclear reactor with spherical fuel elements in a subterranean configuration. The reactor is characterized by a compact construction and extensive elimination of active operating devices, such as charging installation, gas purification devices, regulating systems and safety systems. It is particularly suitable for the generation of thermal energy for heating purposes. A core vessel contains a pile of fuel elements also contains a portion of the graphite bottom and side reflector. Channels are provided in the part of the side reflector located inside the core vessel. Trim and shutdown rods are contained in the channels. The roof reflector rests on the stationary pile of fuel elements. The entire core vessel together with the components contained therein is removed following burnoff of the fuel elements. The heat generated in the core is transferred to a cooling system mounted on the inside of a pressure vessel enclosing the nuclear reactor by a cooling gas which flows from top to bottom.

Abstract: Gas-cooled nuclear reactors include circulation systems for cooling gas to remove the heat generated in the reactor core. An improved arrangement includes a plurality of steam generators in a horizontal plane located above the horizontal plane of the reactor core. The cooling gas circulates from the bottom of the reactor core to the top. Improved heat removal is accomplished in this manner as the heated cooling gas enters the steam generators after passage through the reactor core without undergoing further circulation in a horizontal or inverse vertical direction.

Abstract: A process for the controlled discharge from a reactor containment structure of a gas cooled nuclear power plant and the installation for achieving this process include parallel discharge circuits from a reactor containment structure to a discharge stack. The flow of discharge from the reactor containment structure normally flows in a primary discharge circuit and may be directed wholly or partially to the parallel secondary discharge circuit. The secondary discharge circuit contains means for reduction of the temperature of the discharge, means for deposition of particulate fission products and they also contain means for recombination of combustible gases and means for filtration of the discharge. Nuclear power plant installations and processes for controlling the discharge from a reactor containment structure in this fashion permit safe discharge of naturally occurring leakage for gas cooled nuclear reactors, as well as leakage occurring in the event of reactor failure.

Abstract: Disclosed is a prestressed concrete pressure vessel having a vessel opening which is closed by a concrete cover. Two separate gaskets are disposed between the cover and the pressure vessel, and bordering on an annular channel. The annular channel is connected with a gas detector by means of a connecting channel. At the same time, the inner area of the cover rises from the pressure vessel at a slight angle. The vertical prestress by which the cover is pressed down is larger than the force acting against it (the internal pressure). Additionally, the horizontal annular prestress of the cover is larger in its upper region than in the lower region. In this manner, a constant seal is combined with means for monitoring the seal.

Abstract: The invention concerns a steam generator heated by the cooling gas of a nuclear reactor and arranged in the reactor pressure vessel within a vertical shaft. A blower associated with the steam generator is installed above it. The hot gas is conducted to the steam generator in the form of a helical bundle in the downward direction, with the hot gas being conducted initially downward through an annular channel and entering the bundle of heat exchanger tubes at a uniform velocity. The annular channel is sealed in upward direction by means of a sliding seal, which also serves as an earthquake support. In order to provide access to the feed water and live steam lines in view of the blower arranged on top, the two lines are conducted laterally out of and through the reactor pressure vessel. By means of the special fixation of the individual tubes of the heat exchanger bundle in vertical plates and the presence of an expansion zone for the recycling pipes, differential thermal expansion may be kept small.

Abstract: A nuclear reactor plant with a small high temperature reactor, principal heat exchangers located above the small high temperature reactor and housed in a steel pressure vessel, and a plurality of decay heat exchangers also located in the steel pressure vessel and connected on the cooling water side with an external recooling heat exchanger each, in a geodetically higher location. The object of the invention is to obtain a high degree of availability of the decay heat removal installations. This object is attained by the specific layout and connection of the components of the plant, which permits the operation of the decay heat exchangers both on the primary gas and the water side by natural convection only. The decay heat exchangers and their secondary circulation loops are active during power operations, so that potential failures and leaks are detected immediately. No special actuating measures are necessary to activate the decay heat removal operation.

Abstract: A graphite roof reflector for a small, high temperature reactor is arranged under the hot gas collector space and is therefore exposed to high thermal and radiation loads. In order to make possible the satisfactory support over the entire operating life of the reactor, the roof reflector is assembled from a center part and an annular part, which are supported in a different manner. The annular part is supported on the side reflector of the reactor. The center part is suspended by means of tie rods from a cover located over the hot gas collector space. The tie rods are placed into bores of the cover through which cold gas flows.

Abstract: Disclosed is a nuclear power plant comprising a high-temperature pebble bed reactor contained in a cylindrical steel pressure vessel in which an upper part of the cylindrical steel pressure vessel, which contains a heat utilization system, is retracted and equipped with a cover upon which circulating blowers are placed. The heat utilization system comprises, in a known manner, a single steam generator. The steam generator comprises at least two sub-systems independent of one another, with their own distributors and collectors, and with their own inlet and outlet lines. A first shut-down arrangement comprises a plurality of absorber rods insertable into bores of the side reflector from above and comprises rod drives arranged outside the steel pressure vessel in the area of its retracted upper part. A second shut-down arrangement comprises small absorber spheres for introducing into the core of the reactor, and several storage containers and annular conduits for said spheres.

Abstract: A cost-effective configuration of a metal liner for a reinforced concrete pressure vessel is disclosed wherein only stud shear connectors and cooling tubes of the liner cooling system are used to anchor the liner and the passages provided in the liner and the wall of the vessel. In the areas of the introduction of forces, stud connectors of different stud rigidities are used. In the anchoring of loads which is again effected by stud connectors only, further transmission is obtained by means of reinforcing rods.

Abstract: The invention concerns a nuclear power plant located in an underground cavity, with a small high-temperature reactor which, together with a heat exchanger apparatus, is housed in a steel reactor pressure vessel. The reactor core comprises spherical operating elements which pass through the reactor several times. In order to provide unimpaired access to the components of the primary loop from above, the loading installation of the small high-temperature reactor is designed in a specific manner. It comprises a section located in a loading space under the reactor pressure vessel including a discharge device and a conveyor device. An addition device for fresh operating elements and a collector vessel for used operating elements are arranged either outside the underground cavity or, in the alternative, in the loading space.