Abstract: Nuclear reactor and nuclear reactor cooling facilities, and also a nuclear power generation plant and a method of its operation are disclosed. The reliability of cooling function at the time of anticipated accidents is substantially improved through enhancing a cooling efficiency of the gas in the reactor container without resorting to any particular active means. Guide structure is provided for circulating the gas present in the reactor container so as to accelerate heat removal therefrom to the outside through the surface of the reactor container. The arrangement includes an internal structure for retaining a coolant in the reactor container; and upper space portion disposed over the internal structure; a first gas flow passage for directing downward the gas present in the above upper space portion; and a second gas flow passage connecting the first gas flow passage with the upper space portion.

Abstract: A satellite heat removal means can be embodied as an original nuclear system feature but is especially adapted to be retrofitted to an existing nuclear reactor system to serve optionally to supplement heat removal from the system nuclear reactor containment upon happening of a LOCA, and to assume all system containment drywell venting in the event reactor core meltdown results in breach of the containment floor structure separating the containment drywell and wetwell space which breach would deprive the containment of a space to which a non-condensable fraction of LOCA generated heated fluid in the containment could be vented, cooled and stored. The satellite heat removal means includes a structural external of but preferably situated alongside the nuclear reactor containment. A heat exchanger surrounded by a pool of cooling water is located in an upper chamber of the structure while a pool of water is present in a lower chamber of the structure.

Abstract: A reactor building for enclosing a nuclear reactor includes a containment vessel having a wetwell disposed therein. The wetwell includes inner and outer walls, a floor, and a roof defining a wetwell pool and a suppression chamber disposed thereabove. The wetwell and containment vessel define a drywell surrounding the reactor. A plurality of vents are disposed in the wetwell pool in flow communication with the drywell for channeling into the wetwell pool steam released in the drywell from the reactor during a LOCA for example, for condensing the steam. A shell is disposed inside the wetwell and extends into the wetwell pool to define a dry gap devoid of wetwell water and disposed in flow communication with the suppression chamber. In a preferred embodiment, the wetwell roof is in the form of a slab disposed on spaced apart support beams which define therebetween an auxiliary chamber.

Abstract: A reactor containment facility having a reactor pressure vessel containing a core; a dry well in which the reactor pressure vessel is arranged; a suppression chamber holding suppression-pool water and forming above the suppression-pool water a wet well; and a plurality of vent pipes allowing the dry well to communicate with the suppression-pool water; a steel wall which is in contact with the suppression-pool water of the suppression chamber and which surrounds at least the pool water so as to form a containment vessel which houses the dry well and the suppression chamber; and an outer peripheral pool containing cooling water in contact with the outer peripheral surface of the steel wall.

Abstract: A pressure suppression containment system includes a containment vessel surrounding a reactor pressure vessel and defining a drywell therein containing a non-condensable gas. An enclosed wetwell pool is disposed inside the containment vessel, and a gravity driven cooling system (GDCS) pool is disposed above the wetwell pool in the containment vessel. The wetwell pool includes a plenum for receiving the non-condensable gas carried with steam from the drywell following a loss-of coolant-accident (LOCA). The wetwell plenum is vented to a plenum above the GDCS pool following the LOCA for suppressing pressure rise within the containment vessel. A method of operation includes channeling steam released into the drywell following the LOCA into the wetwell pool for cooling along with the non-condensable gas carried therewith. The GDCS pool is then drained by gravity, and the wetwell plenum is vented into the GDCS plenum for channeling the non-condensable gas thereto.

Abstract: A passive containment cooling system includes a containment vessel surrounding a reactor pressure vessel and defining a drywell therein containing a non-condensable gas. An enclosed wetwell pool is disposed inside the containment vessel, and a gravity driven cooling system (GDCS) pool is disposed above the wetwell pool in the containment vessel and is vented to the drywell. An isolation pool is disposed above the GDCS pool and includes an isolation condenser therein. The condenser has an inlet line disposed in flow communication with the drywell for receiving the non-condensable gas along with any steam released therein following a loss-of-coolant accident (LOCA). The condenser also has an outlet line disposed in flow communication with the drywell for returning to the drywell both liquid condensate produced upon cooling of the steam and the non-condensable gas for reducing pressure within the containment vessel following the LOCA.

Abstract: An improved emergency cooling system and method is disclosed that may be adapted for incorporation into or use with a nuclear BWR wherein a reactor pressure vessel (RPV) containing a nuclear core and a heat transfer fluid for circulation in a heat transfer relationship with the core is housed within an annular sealed drywell and is fluid communicable therewith for passage thereto in an emergency situation the heat transfer fluid in a gaseous phase and any noncondensibles present in the RPV, an annular sealed wetwell houses the drywell, and a pressure suppression pool of liquid is disposed in the wetwell and is connected to the drywell by submerged vents. The improved emergency cooling system and method has a containment condenser for receiving condensible heat transfer fluid in a gaseous phase and noncondensibles for condensing at least a portion of the heat transfer fluid.

Abstract: There is disclosed a nuclear reactor installation. An accumulator-type emergency core cooling system, a gravity-driven core cooling system and an equalizing system for submerging a reactor core are provided within a primary containment vessel containing a reactor pressure vessel in which the reactor core is disposed. These cooling systems are automatically operated sequentially in accordance with the pressure in the reactor pressure vessel without the need for any particular powered source. The primary containment vessel is made of steel, and the interior of this containment vessel is divided into a space containing the reactor pressure vessel and a space containing an operation floor in such a manner that the two spaces are isolated from each other.

Abstract: A water storage tank in the coolant water loop of a nuclear reactor contains a tubular heat exchanger. The heat exchanger has tubesheets mounted to the tank connections so that the tubesheets and tubes may be readily inspected and repaired. Preferably, the tubes extend from the tubesheets on a square pitch and then on a rectangular pitch therebetween. Also, the heat exchanger is supported by a frame so that the tank wall is not required to support all of its weight.

Abstract: A nuclear reactor having a reactor vessel disposed in a containment shell is depressurized in stages using depressurizer valves coupled in fluid communication with the coolant circuit. At least one sparger submerged in the in-containment refueling water storage tank which can be drained into the containment sump communicates between one or more of the valves and an inside of the containment shell. The depressurizer valves are opened in stages, preferably at progressively lower coolant levels and for opening progressively larger flowpaths to effect depressurization through a number of the valves in parallel. The valves can be associated with a pressurizer tank in the containment shell, coupled to a coolant outlet of the reactor. At least one depressurization valve stage openable at a lowest pressure is coupled directly between the coolant circuit and the containment shell.

Abstract: A method for pressure relief of a containment of a nuclear power plant includes heating a washing fluid in a filter disposed inside a containment at a rated heating power through a thermal bridge, with a gas-steam mixture filling the containment, prior to initial operation of the filter. The thermal bridge is rendered substantially ineffective in an operating state of the filter, leaving the washing fluid with a continuous rated heating power being negligible in terms of filtration. In a nuclear power plant having a containment, a system for pressure relief of the containment includes a filter being disposed inside the containment and having a container. At least part of the container has two walls defining a chamber between the walls. A heat-conducting fluid at least partly fills the chamber during a heating period and is at least half evaporated after attainment of an operating temperature.

Abstract: A pressure control chamber of a reactor containment vessel for receiving the atmosphere of the reactor containment vessel containing leakage steam developing in the event of an accident includes a pressure control pool, and a wet well disposed above the pressure control pool. The wet well is divided into an inner peripheral portion and an outer peripheral portion. The inner and outer peripheral portions are communicated with each other via the pressure control pool. An outlet port for flowing the atmosphere of the reactor containment vessel containing the leakage steam is provided at the inner peripheral side of the pressure control pool. When the atmosphere of the reactor containment vessel containing the leakage steam is introduced into the pressure control pool in the event of the accident, this atmosphere is condensed by the water in the pressure control pool, and the gas of this atmosphere not condensed is accumulated in the inner peripheral portion of the wet well.

Abstract: A reactor pressure vessel is disposed in a reactor containment vessel and is supported by a pedestal having a cylindrical structure. The inside of the reactor containment vessel is divided into upper and lower drywells by means of a diaphragm floor. A line, a cable and a duct are disposed in and between the upper and lower drywells in the reactor containment vessel. The pedestal comprising a plurality of concrete wall sections and a plurality of connecting vent sections which are arranged alternately along a circumferential direction of the cylindrical pedestal, wherein the line, the cable and the duct are arranged in each of the connecting vent sections and a vent pipe is arranged in each of the concrete sections. A vacuum breaker is further disposed in the reactor containment vessel at a portion above the open end of the vent pipe, the vacuum breaker is connected to a fixing pipe for mounting a vacuum breaker to the pedestal and the fixing pipe has one end opened to the drywell.

Abstract: A nuclear fission reactor combined with a propellant actuated depressurization and/or water injection valve is disclosed. The depressurization valve releases pressure from a water cooled, steam producing nuclear reactor when required to insure the safety of the reactor. Depressurization of the reactor pressure vessel enables gravity feeding of supplementary coolant water through the water injection valve to the reactor pressure vessel to prevent damage to the fuel core.

Abstract: A reactor containment vessel with a cooling system includes a communication pipe having a valve to be connected to either an emergency condenser or suppression chamber in order to improve cooling performance by removing non-condensable gas from heat exchanger tubes when a main steam line is broken. One open end of the communication pipe is opened and positioned at a low position of the dry well. The valve is constantly closed and actuated to be opened in an abnormal condition of a reactor. When the valve is opened, the communication pipe introduces the non-condensable gas existing in the emergency condenser or suppression chamber to the low area of the dry well due to a density differential between steam and non-condensable gas, thus removing the non-condensable gas from the heat exchanger tubes, and improving the cooling performance of the emergency condenser.

Abstract: A nuclear energy plant housing a boiling-water reactor utilizes an isolation condenser in which a single chamber is partitioned into a distributor plenum and a collector plenum. Steam accumulates in the distributor plenum and is conveyed to the collector plenum through an annular manifold that includes tubes extending through a condenser pool. The tubes provide for a transfer of heat from the steam, forming a condensate. The chamber has a disk-shaped base, a cylindrical sidewall, and a semispherical top. This geometry results in a compact design that exhibits significant performance and cost advantages over prior designs.

Abstract: A nuclear energy plant housing a boiling water reactor utilizes an isolation condensers with nearly horizontal condenser tubes for both isolation condenser (IC) mode and passive containment cooling system (PCCS) mode, which is entered in response to a loss-of-coolant accident (LOCA). These tubes extend between a cylindrical distributor and a cylindrical collector. In either mode, the reactor vessel is coupled to the cylindrical distributor. Steam reaching the condenser is condensed to water, which flows back to the vessel, providing a cooling effect. In PCCS mode, gas exiting the tubes is trapped and diverted into a wet well. This diversion path is not avialable in IC mode. As a result water exits the tubes more slowly in IC modes in PCCS mode. The water remaining in the tubes during IC mode renders the condenser less efficient. This lower efficiency partially offsets the greater heat exchange in IC mode due to higher temperature differentials and the relatively absence of noncondensable gases.

Abstract: The apparatus comprises a conduit connected to a containment vessel to supply air to a water bath contained in a basin. The conduit is connected to a plurality of air nozzles in the water bath, each of which forms a unit together with a perforate baffle plate disposed above the nozzle to intensively mix the emerging air with water. A set of static mixer elements enclosed by a jacket is disposed in the water bath above the baffle plate.

Abstract: Disclosed is a liquid filling apparatus for high-temperature and high-pressure vessel. The apparatus comprises a high-temperature and high-pressure vessel, a closed liquid storage tank disposed at a level higher than that at which liquid is filled into the high-temperature and high-pressure vessel, a liquid-filling flow passage for supplying liquid from the closed liquid storage tank into the high-temperature and high-pressure vessel, a pressure-feed flow passage for supplying pressure from the high-temperature and high-pressure vessel to the closed liquid storage tank, valves equipped on the liquid-filling flow passage and the pressure-feed flow passage respectively, and a liquid-filling liquid source adapted to communicate with the interior of the closed liquid storage tank via a valve, whereby the environmental surroundings of the closed liquid storage tank are lower in temperature than the interior of the high-temperature and high-pressure vessel.

Abstract: A gravity driven cooling system pool is disposed at an elevated location with respect to the locations of nuclear fuel rods in a pressure vessel. In the event of a loss of coolant in the pressure vessel, steam pressure is initially reduced by venting the steam into the containment or a closed suppression pool containing a quantity of water under a large air space. The suppression pool condenses sufficient steam to lower the steam pressure in the pressure vessel so that water can flow by gravity from gravity driven cooling system pool to flood the fuel rods in the pressure vessel. An isolation condenser is submerged in a large supply of water elevated with respect to pressure vessel. Steam is admitted to the isolation condenser, or heat exchanger, where it is cooled by boiling the water surrounding it. This steam is vented to the atmosphere. A depressurization valve vents steam fro the pressure vessel into the containment to aid pressure reduction, and thus to aid the gravity flow of coolant.

Abstract: An improved passive cooling system for water cooled and moderated nuclear fission reaction plants provides means for enhancing the cooling arrangement for coping with loss of coolant accidents or removing decay heat during periods of reactor shutdown. The improvement comprises providing a measure consisting of a tubular sleeve, which encourages flow circulation within a pool of cooling water.

Abstract: The present invention is directed to a nuclear reactor facility wherein a nuclear reactor pressure vessel (RPV) is housed within an annular sealed drywell, an annular sealed wetwell houses said drywell, a pressure suppression pool of liquid is disposed in said wetwell and is connected to said drywell by submerged vents, a condenser line connects said drywell to an isolation condenser, and a bleedline from said isolation condenser is connected to said pool and terminates under the surface of said pool. The improvement of the present invention comprises a liquid reservoir disposed in said drywell and a standpipe disposed in said wetwell. The reservoir and the standpipe are connected by a duct which is located below the surface of said reservoir a distance, D. The area of the reservoir is at least 25 times larger than the area of said standpipe.

Abstract: A reactor containment vessel comprises typically a reactor pressure vessel housed in a dry well of the reactor containment vessel, a vent passage through which steam in the dry well is introduced into coolant accommodated in a pressure suppression chamber of the reactor containment vessel, a closed space formed at a position lower than the level of the normal liquid surface of the coolant, a first passage having an inlet opened into the pressure suppression chamber at a level higher than that of the normal liquid surface of the coolant and an outlet opened into the closed space, and a second passage communicating between the closed space and the dry well through a counter flow preventing arrangement for checking the flow directed toward the closed space, and therefore, noncondensable gas and liquid accumulated in the pressure suppression chamber are discharged into the dry well the pressure in which is higher than that in the pressure suppression chamber by making use of a difference in water head increased d

Abstract: Method and apparatus for avoiding potential accidents in water-cooled nuclear reactors of the type having an enclosing containment, due to the formation of an explosive gas mixture in the containment. Air is withdrawn from the containment and fed to at least one internal combustion engine as combustion air for the engine. The exhaust gases created by the internal combustion engine are then recycled back into the containment. The result is the lowering of the oxygen partial pressure in the containment to below the critical limit for oxyhydrogen explosion.

Abstract: The wetwell space in a suppression pool of a nuclear reactor containment is continuously ventilated by exhausting gas therefrom, while at the same time, during normal system operation atmospheric air from a source of same is admitted to the wetwell but such admission being blocked during a LOCA. All exhaust flow from the wetwell is conveyed through a conduit that outlets at a remote elevated location in the atmosphere. All exhaust flow through the conduit is before outletting therefrom passed through gas treatment operation wherein any particulates in the gas mixture are removed. Further treatment of the gas with charcoal to adsorb noble gases can be carried out. In normal reactor operation the ventilation flow rate is at minimal level. However on occurrence of a loss-of-coolant-accident, highly heated gases from the containment drywell are passed into the suppression pool where condensables condense while non-condensable gases are cooled and vent to the wetwell.

Abstract: A water cooled nuclear reactor comprises a reactor core, a primary water coolant circuit and a pressuriser arranged as an integral unit in a pressure vessel. The pressure vessel is divided into an upper chamber and a lower chamber by a casing, the reactor core and primary coolant circuit are arranged in the lower chamber and the pressuriser is arranged in the upper chamber. A movable diaphragm is positioned in the upper chamber, and is sealingly secured to the casing by a bellows arrangement to divide the upper chamber into a water filled space and a gas filled space. A plurality of surge ports interconnect the water space with the primary coolant circuit. The diaphragm moves to accommodate changes in the volume or pressure of the water in the primary coolant circuit and water space. The diaphragm is loaded by springs and dampers to prevent oscillation of the diaphragm. Alternatively the diaphragm may be an elastic membrane.

Abstract: A nuclear reactor facility including a primary containment vessel, a reactor pressure vessel installed in the primary containment vessel and accommodating a reactor core in a lower part thereof, and a vertical cylindrical wall disposed in a lower part of the primary containment vessel around and spaced from the reactor pressure vessel so as to delimit an annular space therebetween. The vertical cylindrical wall has an upper end disposed at a position higher than an upper end of the reactor core and a diaphragm extends substantially horizontally between the upper end of the vertical cylindrical wall and an inner wall of the primary containment vessel for cooperating with the vertical cylindrical wall to separate a space in the primary containment vessel around the reactor pressure vessel into a pressure suppression chamber and a drywell which includes annular space.

Abstract: A nuclear system of the type which includes a containment wherein a nuclear reactor pressure vessel is located has a suppression pool to which steam can be vented so that it will condense and reduce the pressure in the pressure vessel upon the happening of an accident such as loss of reactor coolant or a steam pipe failure. Steam also can be vented directly to the containment space to further reduce pressure in the reactor. When reactor pressure is lowered to a certain pressure value, a gravity supply of water from an elevated pool of water will have a sufficient head to flow against the pressure in the reactor and into the reactor to submerge the fuel rods in the reactor. One or more isolation condensers are submerged in a large supply of water this supply being elevated some distance above the pressure vessel. At least one isolation condenser has inlet thereto communicated to an open entry conduit disposed in the containment.

Abstract: A nuclear reactor system which includes a containment uses, upon loss-of-coolant event, an isolation condenser submerged in a large supply of water and elevated some distance above the system pressure vessel to effect both initial and decay heat dissipation cooling in the containment. The isolation condenser has inlet thereto communicated to an open entry conduit disposed in the containment so that steam and heated gasses in the containment space enter the isolation condenser and are cooled. Condensate resulting from the cooling is returned to an elevated system gravity coolant supply pool, which pool is used for replenishing coolant lost from the pressure vessel, the return being through a return conduit that has a lower end section configured with a water trap with non-condensable gasses present in the steam being separated from the condensate and vented to the suppression pool.

Abstract: A primary containment vessel, comprising a reactor pressure vessel in which a core is accommodated, a dry-well volume covering the upper portion of the reactor pressure vessel, a suppression chamber provided with a suppression pool surrounding an intermediate portion of the reactor pressure vessel, has a plurality of vent tubes establishing a connection between the dry-well volume and the suppression pool and an annular baffle plate disposed in the suppression pool along the side wall of the suppression chamber, having its top end positioned at a height between a free surface of the suppression pool and an outlet of the vent tube opened in the suppression pool and its lower end positioned at a height between the outlet and the bottom of the suppression pool. If a loss of coolant accident occurs, hot steam discharged into the dry-well volume is discharged into the suppression pool through the vent tube so as to heat water on the inside of the baffle plate.

Abstract: A nuclear power plant includes a containment for the retention of radioactivity having an overpressure safety outlet. A filter connected to the outlet includes a vessel for receiving a scrubbing liquid up to a given liquid level, a venturi scrubber disposed in the vessel having an outlet disposed above the given liquid level, an impact plate disposed at the outlet of the venturi scrubber for mist collection, a metal-fiber filter downstream of the venturi scrubber having at least first and second layers with a thickness of from 10 to 20 mm, the first layer being a moisture collector with a fiber thickness of from 8 to 20.mu. and the second layer being an aerosol collector with a fiber thickness of from 2 to 7.mu., and a mist collector downstream of the metal-fiber filter. The vessel has a top with a gas outlet downstream of the mist collector. A stack is connected to the gas outlet and leads to the atmosphere.

Abstract: A container-outer-periphery pool in which water is stored is provided between a primary containment vessel and a reactor building, and outside of a pressure suppression pool. Consequently, the natural heat transfer capabilities of reactor facilities is enhanced, and the inherent safety of the reactor facilities is improved.

Abstract: An emergency core cooling system for spraying cooling water onto a nuclear reactor core of a nuclear reactor includes at least one header disposed in the nuclear reactor and arranged at an upper and outer circumferential position with respect to the reactor core. A plurality of spray nozzles are mounted on the at least one header for spraying cooling water onto the reactor core. The spray nozzles have a center axis and at least one of the plurality of spray nozzles is mounted on the at least one header so that the center axis thereof extends upwardly with respect to a horizontal axis whereas at least one of the remaining plurality of spray nozzles has the center axis thereof extending downwardly with respect to the horizontal axis. Cooling water is conducted to the at least one header for enabling spraying of the water in the emergency situation.

Abstract: A closed passive nuclear reactor pressure suppression containment system segrated from the nuclear island having suppression tanks connected to the reactor compartment by one or more vent lines terminating in downcomer lines submerged into a water pool in each of said suppression tanks and a return line from each suppression tank whereby water is directed from the suppression tanks to the reactor, by gravity and without active components, to flood the reactor during a loss of coolant accident.

Abstract: In a steam generator utilized with a liquid sodium cooled nuclear reactor, provision is made to vent the violent sodium water reaction emanating from a tube rupture casualty. The steam generator includes a sodium plenum at the bottom thereof containing a conventional rupture disk for venting sodium, steam, and reaction products including hydrogen immediately upon a tube rupture casualty. The invention includes providing an alternate concentric flow path interior to the steam generator and parallel to the tube bundle. This alternate concentric flow path extends from the upper portion of the steam generator down into the lower head or plenum adjacent to the pressure relief diaphragm. This alternate path is partially filled with sodium during normal reactor operation.

Abstract: A suppresion chamber in a nuclear reactor containment includes a heat exchanger disposed in a gas space above water in the suppression chamber. A gravity-driven pool contains a supply of make-up water that is gravity fed to the heat exchanger through a conventional level-maintaining valve such as a float valve. A top header in the heat exchanger includes a free surface area for permitting separation of steam from water, thereby permitting venting of vapor only, while retaining the liquid coolant in the heat exchanger. A downcomer tube permits return of excess water to a lower location for further use in the heat exchanger. The heat exchanger is normally sealed, whereby internal surfaces in the heat exchanger require only a small amount of low-volatility corrosion inhibitors to prevent corrosion on internal surfaces thereof. Locating the heat exchanger in the gas space in the suppression chamber reduces the amount of corrosion on its external surfaces.

Abstract: A passive cooling system for the contaminant structure of a nuclear reactor plant providing protection against overpressure within the containment attributable to inadvertent leakage or rupture of the system components. The cooling system utilizes natural convection for transferring heat imbalances and enables the discharge of irradiation free thermal energy to the atmosphere for heat disposal from the system.

Abstract: A self-actuating passive pressure relief device for nuclear reactor containments is described. The pressure relief device passively releases gases from within a reactor containment when the containment pressure exceeds a designated threshold pressure. The pressure relief device automatically reseals itself when the containment pressure drops below the threshold pressure. Any containment gases that are vented by the pressure relief device from the containment are scrubbed and cleansed before they are released into the atmosphere. To accomplish this, a sealed fluid chamber is placed in direct communication with the reactor containment for holding a liquid material such as water. A standpipe having its lower end extend into the sealed container and has an opening below the normal operating liquid level within the chamber.

Abstract: A passive cooling system for the contaminant structure of a nuclear reactor plant providing protection against overpressure within the containment attributable to inadvertent leakage or rupture of the system components. The cooling system utilizes natural convection for transferring heat imbalances and enables the discharge of irradiation free thermal energy to the atmosphere for heat disposal from the system.

Abstract: A method and apparatus for pressure relief of a nuclear power plant includes the feeding of fluid from an outlet opening of a containment through a filter to a stack. The filter is operated with sliding pressure regulated as a function of the pressure in the containment.

Abstract: A depressurization valve for use in relieving completely the pressure in a simplified boiling water reactor is disclosed. The normally closed and sealed valve is provided with a valve body defining a conduit from an outlet of a manifold from the reactor through a valve seat. A closing valve disk is configured for fitting to the valve seat to normally close the valve. The seat below the disk is provided with a radially extending annulus extending a short distance into the aperture defined by the seat. The disk is correspondingly provided with a longitudinally extending annulus that extends downwardly through the aperture defined by the seat towards the high pressure side of the valve body. A ring shaped membrane is endlessly welded to the seat annulus and to the disk annulus. The membrane is conformed over the confronted surface of the seat and disk in a C-sectioned configuration to seal the depressurization valve against the possibility of weeping.

Abstract: Two systems of low-pressure core spray appratuses have coolers, and are adapted to supply cooling water to a core spray header provided in a core-surrounding cylindrical shroud in a reactor pressure vessel. Two systems of high-pressure core flooding apparatuses and one system of high-pressure coolant injection apparatus are adapted to supply the cooling water to a region formed between the shroud and reactor pressure vessel. The elevation of the openings, which are in the reactor pressure vessel, of the high-pressure core flooding apparatuses and high-pressure coolant injection apparatus are higher than that of the core spray header. A pipe for returning the cooling water in the reactor pressure vessel to the above-mentioned coolers is connected to either the portion of the interior of the reactor pressure vesssel which is below the core or the portion of the interior of the reactor pressure vessel which is between the walls of the shroud and reactor pressure vessel.

Abstract: A liquid receiver which acts as a pressure relief valve for radioactive vapor or gases from a nuclear reactor comprises a container 4 holding liquid 3 and nozzles 13 which discharge vaporous or gaseous coolant from an outlet 2 from the reactor into the liquid 3. So that the liquid 3 does not lose its barrier capability during a temporary rise of pressure or at low outflow rates of the coolant from the outlet but can be expelled independently of the nature and temperature of the coolant, the nozzles 13 are mounted on a nozzle ring 11 which has a vertical axis and all the nozzles are directed tangentially in the same direction to generate a cyclone effect in the container 4. This causes the liquid 3 to have its surface lowered from the static level 5 to the rotational surface 15. This reduces the length of the path of the escaping gas or vapor through the liquid 3.

Abstract: A pressurized water nuclear reactor comprises a normally vertical main vessel externally duplicated by a confinement enclosure. The main vessel contains a simplified primary circuit essentially incorporationg the reactor core and an annular steam generator arranged in such a way that the circulation of water, pressurized once and for all during the sealing of the vessel, takes place by natural convection. All the auxiliary circuits, conventionally ensuring cooling on shut down of such a reactor are eliminated, said cooling being ensured by a special arrangement of the space formed between the vessel and the enclosure and by the fact that the latter is immersed in an external cooling liquid, no matter what the slope of the reactor. The shut down of fission reaction in the core is ensured by systems of absorbing elements and by the automatic displacement of part of the reflector in the case of a slope of the reactor.

Abstract: A pressurized water nuclear reactor has a reactor vessel arranged in a pool, which is filled with a neutron absorbing liquid, for example borated water. The reactor vessel is closed except for tubes connecting it with a tray above it. The coolant in the circuit rises from the vessel to the tray, gives up its heat by flashing, and flows back to the bottom of the vessel, driven by natural circulation. The tray is separated from the pool by a vapor-filled bell, which surrounds it. In the bell the vapor gives up its useful heat to a condenser. The relatively low boron content of the cooling circuit, compared to the pool, is achieved by continuous dilution of the condensate from vapor additionally generated out of the pool water. The dilution process is an equilibrium with continuous inflow of the pool water. The inflow is automatically controlled by the pool level, which rises when the pool water is pressed out from below the bell by overproduction of vapor.

Abstract: A high-temperature gas cooled nuclear reactor system comprises a containment building, a concrete reactor pressure vessel inside the containment building, and a safety relief valve connected to the concrete reactor pressure vessel. The spring of the safety valve consists of a material with a spring constant decreasing as temperature rises. A heat exchanger is provided in close proximity to cool the spring of the safety valve which is subject to the heat of the reactor coolant escaping when the safety valve is open. The heat exchanger of the safety valve is connected to a liner cooling system of the concrete reactor pressure vessel.

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 passive safety system for a nuclear reactor is comprised of a first subsystem for circulating water solely by natural convection from a first branch to a second branch of a reactor coolant circuit with the circumvention of a steam generator for removing decay heat from the reactor coolant circuit at any pressure. The first branch guides heated water from the reactor vessel into the steam generator and the second branch guides cooled water from the steam generator into the reactor vessel. The first subsystem includes a heat exchanger for cooling water flowing from the first branch and prior to being introduced into the second branch and a first valve for allowing flow of water from the first branch into the second branch solely in response to a parameter value pertaining to operational safety. There is also provided a second subsystem for introducing stored cold water solely by gravity into the reactor vessel for making up for lost water in the reactor coolant circuit at any pressure.

Abstract: A pressure control system for a pressurized water nuclear reactor and method for quickly closing the valves associated with the pressurizer thereof has a temperature detection device on the loop seal of each valve and a valve responsive thereto to change water to the loop seal upon a temperature rise therein and stop the flow of water to the loop seal upon a temperature drop therein. The rapid formation of water seals in the loop seals for the valves protects the valve seats from wear and degradation and prolongs the life thereof.

Abstract: An improved pressure control system for a pressurized water nuclear reactor plant contains a novel, two stage sparger in the pressurizer relief tank. The two stage sparger has a primary conduit and secondary conduit, both of which have orifices through the walls thereof, and an interconnecting valve that is responsive to a pressure differential between the two conduits. The secondary conduit is preferably of a diameter less, but with a larger area of flow therefrom, than the primary conduit and is bifurcated, with two leg sections extending back towards the primary conduit.