Abstract: A safety system controlling extremely unlikely disturbances in high temperature reactors in addition to and independent of the normal reactor protection systems. Accident instrumentation located in the high temperature reactor monitors certain characteristic process parameters (hot gas temperature, cold gas temperature, cooling gas pressure), for values of which clearly exceed limiting values of the reactor pressure system. The measured data is evaluated electronically and power supply to the cooling gas blowers, feed water pumps and absorber rod holding devices is interrupted if predetermined limiting values are exceeded. The power supply interruption is further actuated by temperature and pressure sensitive devices located in the nuclear reactor. A manually operated emergency switch is provided to turn off the aforementioned sensibilities.

Abstract: A gas cooled high temperature reactor with a core of preferably spherical fuel elements enclosed by a graphite roof and a side and bottom reflector. In order to minimize environmental contamination by fission products, even upon (hypothetical) core overheating accidents, the upper part of the roof reflector incorporates volatile iodine and cesium iodide, suitable metal atoms or molecules of the compounds of these metals bonded into the cracked binder material of the graphite. The dilution of the doping material must be high enough (from 1:100 to 1:10,000), so that the substances (for example alkaline earth metals or rare earths) are present as individual atoms or molecules. The iodine is chemically bound to the doping atoms, and iodide formed in this matter is retained in the cracked binder material. Molecules of high temperature oxides may also be incorporated.

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: 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 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 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 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: 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: 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 process and an installation for the securing against excessive pressure in a prestressed concrete pressure vessel of a gas cooled high temperature reactor and for the prevention of activity release into the environment. The process comprises three steps and in each step pressure reducing installations become effective upon the rise of pressure in the prestressed concrete pressure vessel over a predetermined value. In the first step the pressure vessel is relieved by means of the operational gas purification apparatus and a conveying blower into the storage vessels for the cooling gas. In case of a further rise in pressure, in a second step a discharge path equipped with a safety valve and a check valve is opened, which also relieves into the storage vessels while by-passing the gas purification installation.

Abstract: Disclosed is a control system and process for operating same for nuclear reactors, particularly gas cooled nuclear reactors, comprising in the control system a means for measuring the output produced in the reactor core and the output removed by a primary circuit or a secondary circuit, a means for integrating the integral of the core produced output over the output level, during the same time, of the primary or secondary circuit of the reactor and a means for forming a control signal from the value of the integral.