Abstract: A chimney arranged inside of a reactor pressure vessel of a natural-circulation boiling water reactor is provided. The chimney includes plural flow channels which guide a steam-water two-phase flow generated in a reactor core to the upper part of the reactor pressure vessel. Each of the flow channels is formed by plural flow channel separation walls whose lower-most part is supported by a chimney lattice plate. Chimney spacers that support a horizontal load are arranged between the flow channel separation walls of the adjacent flow channels. Chimney support rings that support the horizontal load are arranged at the outermost periphery of the plural flow channels that are supported by the chimney lattice plate.

Abstract: A quick disconnect for a control rod drive mechanism seismic support tie rod system that is remotely operable from a nuclear power plant's operating deck. A wall mounted anchor in the reactor cavity contains one half of a disconnect coupling that interfaces with the other half of the disconnect coupling on the ends of the tie rods employing a remote winching system that is actuated from the top of the reactor head assembly. A latching mechanism is then actuated from the refueling cavity operating deck to lock the tie rod in place and prevent displacement during a seismic or pipe break event. The tie rod may similarly be unlocked from the wall anchor and raised above the reactor head assembly as part of a reactor head disassembly operation to gain access to the core of the reactor vessel for refueling.

Abstract: An apparatus for producing polycrystalline silicon having: a bell jar having a circumferential wall forming a chamber of a reactor and a jacket covering a circumferential wall, and in which a cooling path formed between the circumferential wall and the jacket that allows cooling medium including water to flow therethrough; a coolant feeding system which is connected to the bell jar so as to feed the cooling medium to the cooling path; a coolant recovering system which is connected to the bell jar so as to recover the cooling medium from the cooling path; a pressure control part controlling a pressure in the cooling path; and a flow-rate control part controlling a flow rate of the cooling medium, wherein the cooling medium flows in the cooling path as boiling two-phase flow by controlling the pressure and flow rate of the cooling medium.

Abstract: In the boiling water nuclear plant of the present invention, a steam dryer is disposed in a reactor pressure vessel. Materials that have capability of capturing nitrogen compounds containing N-16 are supported on porous member. The porous members are placed in a region where steam goes through in the steam dryer. For example, both or either of perforated plates installed in the steam dryer is constituted of the porous member on which N-16 capture material is supported. When steam containing N-16 goes through the perforated plates, the N-16 is captured by the porous member, whereby the N-16 transfer amount into the turbine system is reduced.

Abstract: According to an embodiment, a steam separator is provided with a barrel, a swirler, a pick-off ring, a steam collecting pipe and transverse pipes. A two-phase flow of steam and water ascends inside the barrel. The two-phase flow has a swirl force imparted by the swirler. Flow near the inner surface of the barrel is separated by the pick-off ring, etc. from flow near the center of the barrel and is guided so as to descend along the outer surface of the barrel. A major part of the flow near the center of the barrel is separated from the outside flow by the steam collecting pipe and guided to the outside of the barrel through the transverse pipes.

Abstract: A device and method for stabilizing a dryer assembly in a reactor pressure vessel of a nuclear reactor including a spring assembly dimensioned and positioned within the reactor pressure vessel for applying a stabilizing force to the dryer assembly relative to the reactor pressure vessel.

Abstract: A vane configuration for a steam dryer according to an example embodiment of the invention may include a plurality of primary vanes arranged in a radial pattern around (and spaced apart from) a center line. Each of the plurality of primary vanes may be a primary corrugated sheet having alternating primary ridges and primary furrows. As a result, adjacent primary vanes may define a winding flow path, the flow path having an entrance and an exit relative to the center line. The cross-sectional area of the flow path may decrease, increase, or remain constant from the entrance to the exit.

Abstract: A device and method for stabilizing a dryer assembly in a reactor pressure vessel of a nuclear reactor including a spring assembly dimensioned and positioned within the reactor pressure vessel for applying a stabilizing force to the dryer assembly relative to the reactor pressure vessel.

Abstract: A steam separator comprises an outer main swirler and an inner auxiliary swirler which is smaller than the main swirler. The swirlers are provided so as to be concentric on the inner wall at the lower side of the first stage inner cylinder. In the steam separator, when the gas-liquid two-phase flow which flows in the vicinity of the axial center of the first stage inner cylinder passes the auxiliary swirler, it is separated into steam and water by the centrifugal force. The separated water (droplets) is introduced into the main swirler. When the separated water (droplets) passes the main swirler, it is separated at the inner wall side of the first stage inner cylinder by the centrifugal force. Pressure loss in a steam separator is reduced and steam separation capability is increased without increasing the moisture from the steam separator.

Abstract: A steam dryer includes a plurality of steam dryer banks. Each steam dryer bank includes a hood, separator vanes, and a perforated plate connected to the hood to define a volume configured to receive a flow of steam. Each dryer bank forms a closed loop.

Abstract: A device and method for stabilizing a dryer assembly in a reactor pressure vessel of a nuclear reactor including a spring assembly dimensioned and positioned within the reactor pressure vessel for applying a stabilizing force to the dryer assembly relative to the reactor pressure vessel.

Abstract: A steam dryer through which steam flows vertically, in particular for a nuclear reactor, contains a plurality of water tanks for removing water which has been separated from the steam. The water tanks are disposed below dryer elements through which the steam flows. The water tanks of the steam dryer have in each case in the flow direction a cross section which is favorable in terms of flow.

Abstract: A pressure vessel of a reactor has a flow space between the reactor core and a separation device for separating water from water steam. The cross-section area of the flow section of the space expands upstream of the separation device. This makes it possible to pre-separate a water-water steam mixture coming from the reactor core. Due to the pre-separation, only the central area is provided with a cyclone device, and only drying equipment is disposed near the cyclone device. The novel approach makes it possible to reduce the height of the pressure vessel of a reactor.

Abstract: A natural circulation boiling water reactor provides to a chimney with a plurality of tubes. That is to say, each of the plurality of tubes partitions the coolant flow path above a core. Thus, unlike the conventional natural circulation boiling water reactor providing the flow path partition wall grid in which the plate members are made integral by welding and coolant flow paths are partitioned, the chimney of the natural circulation boiling water reactor can reduce the number of welded portions because the edges of the four corners of each flow path do not need to be welded. The natural circulation boiling water reactor can avoid removal as a single unit, as in the case of the flow path partition wall grid in the conventional natural circulation boiling water reactor, by detaching each tube. The chimney can be easily detached from the reactor pressure vessel.

Abstract: A chimney lattice is arranged in a reactor pressure vessel. Thermocouple extension wire pulling conduits inserting a temperature detection thermocouple and a cable connected to the thermocouple are mounted to the upper end of the chimney lattice. By mounting the thermocouple extension wire pulling conduit on the upper end of the chimney lattice, the thermocouple extension wire pulling conduit does not become an obstacle when the fuel assembly is taken out from the chimney. Because the thermocouple extension wire pulling conduit is installed at the upper end of the chimney, the replacement of the thermocouple damaged is easy.

Abstract: Migration of radioactive materials from a pressure vessel to a steam system in a nuclear power plant is suppressed by using a dryer (3) provided with corrugated plates (22) having surfaces coated with an inorganic ion-exchange material stable under a condition in which high-temperature water exist, such as TiO2.

Abstract: A main steam system around a nuclear reactor which comprises two main steam nozzles in a reactor pressure vessel, each of the main nozzles being disposed at a symmetrical position with respect to a plane parallel to steam outlet faces of steam dryers provided inside the reactor pressure vessel and passing through a center of the reactor pressure vessel; and main steam pipes each connected to the main steam nozzles.

Abstract: A fuel assembly for a boiling water reactor which is designed to allow water, during operation of the reactor, to flow upwards through the fuel assembly while absorbing heat from a plurality of fuel rods, whereby part of the water is transformed into steam. The fuel assembly comprises a first steam pipe (10a) arranged with its longitudinal axis parallel to the longitudinal axis of the fuel assembly and the steam pipe comprises an inlet for the steam arranged in the first end of the steam pipe and an outlet for the steam arranged in the second end of the steam pipe. The fuel assembly also comprises a second steam pipe (10b) arranged above and at a distance from the first steam pipe such that an opening is formed between the steam pipes. The outlet of the first steam pipe has a diameter which is larger than the diameter of the inlet of the second steam pipe.

Abstract: A separator/injector having an outlet pressure higher than an inlet pressure thereof is introduced instead of the dynamic equipment for a reactor recirculation system that is necessary in the prior art, to achieve both liquid-vapor separation and forced circulation. A jet pump and a recirculation flow-rate control valve are provided in a lower portion of a downcomer portion of a reactor pressure vessel. A shroud head has a double-walled structure, a two-phase liquid-vapor flow that is flowing from a lower portion of the lower shroud head is accelerated by an accelerator nozzle of the separator/injector, and a liquid component of the thus-separated flow is increased in pressure and guided into a jet pump through a space formed between the double shroud heads.

Abstract: A steam/water separating device for a nuclear fuel bundle is located in a vent volume above part-length rods and includes a helical swirl vane. In one form, the swirl device lies below a vent tube and a transition element for flowing liquid laterally outwardly into the interstices of the fuel rods and steam upwardly within the vent tube. In another form, the vane depends from a cylindrical barrel open at its lower end. An annular pick-off tube extends into the open upper end of the barrel and lies in communication through a transition element with a superposed steam vent tube. An annular outlet is defined between the barrel and pick-off tube and the transition element deflects coolant water flowing through the annular outlet in a lateral outward direction for flow into the interstices of and onto the full-length fuel rods. Steam flows upwardly in the barrel through the pick-off tube into the steam vent tube.

Abstract: The steam/water separator includes a lower standpipe for receiving a two-phase mixture of water and steam at its lower end. Internal threads or elements spaced about the interior wall of the standpipe impart a swirl to the incoming mixture, producing a thin film along the walls. Standard pick-off rings or a porous wall may be employed to separate the liquid from the vapor. A central swirl is imparted to the flow in the region dominated by vapor. This combination of peripheral swirl followed by a central swirl for steam/water separation affords minimum pressure losses along the separator with reduced sensitivity to inlet and submergence conditions.

Abstract: A fuel assembly for a boiling water reactor comprises a bottom tie plate, a top tie plate, and a first and a second group of vertical fuel rods, each including a column of fuel pellets surrounded by a cladding tube. The second group of fuel rods has a shorter active length than the first group of fuel rods. Both the first and the second group of fuel rods extend between the bottom tie plate and the top tie plate. The second group of fuel rods comprises a fission gas plenum surrounded by a plenum tube arranged above the cladding tube. The main part of the plenum tube has a cross-section area which is smaller than the cross-section area of the cladding tube.

Abstract: A chimney which can be reconfigured or removed during refueling to allow vertical removal of the fuel assemblies. The chimney is designed to be collapsed or dismantled. Collapse or dismantlement of the chimney reduces the volume required for chimney storage during the refueling operation. Alternatively, the chimney has movable parts which allow reconfiguration of its structure. In a first configuration suitable for normal reactor operation, the chimney is radially constricted such that the chimney obstructs vertical removal of the fuel assemblies. In a second configuration suitable for refueling or maintenance of the fuel core, the parts of the chimney which obstruct access to the fuel assemblies are moved radially outward to positions whereat access to the fuel assemblies is not obstructed.

Abstract: A control system for avoiding coupled neutronic-thermal hydraulic instabilities during maneuvering of a boiling water nuclear reactor that determines the average elevation in the reactor core of the coolant boiling boundary, and avoids instabilities by maintaining the core average coolant boiling boundary elevation above a target value, which is dependent on reactor design specifics but may be about four feet, in core power-flow operating regions which are subject to instabilities. The system may be implemented without physical modification of existing reactors or reactor instrumentation and control systems through use of the reactor core monitoring computer, which typically has available all core parameters necessary for the computations required in the invention.

Abstract: A jitter generating device for use in a data communication system. The device has a repeating unit with an input and an output connected in use to receive data from the data communication system and to repeat the data onto the data communication system respectively. A clock signal generator generates a clock signal which is fed to the repeating unit to control the rate at which data is output onto the data communication system. A clock phase (jitter) modulating unit modulates the phase of the clock signal output by the clock signal generator.

Abstract: An edge detector has a digital phase locking loop in which one of the signals (e.g., the data signal) is coupled to a delay chain that develops a series of incrementally phase delayed versions of the input. Adjacent phase delayed pairs are selected, one pair at a time, and are compared to the other signal (e.g., the clock signal) to determine if an edge of the clock falls between the edges of the data signal in the selected phase pair, or falls outside the edges of the selected phase pair, on one side or the other thereof. If the clock edge falls outside the selected pair, a control signal selects another pair for comparison and the process is repeated until, for example, the data edges are aligned with the positive going edge of the clock. With a clock frequency equal to twice data frequency, the data can then be sampled on the falling edge of the clock.

Abstract: A nuclear reactor has a containment vessel and a voided calandria space having a plurality of fuel channels therein. A chamber surrounding the calandria space is receptive of a light water moderator and a solid reflector in the chamber surrounds the calandria space. Each fuel channel has a solid fuel matrix having a plurality of coolant holes extending longitudinally therethrough and receptive of light water coolant, a pressure tube surrounding the fuel matrix and a calandria tube surrounding the pressure tube and forming a gap therebetween.

Abstract: In a fuel bundle for use in the core of a boiling water nuclear reactor, part length rods having a tendency to reduce pressure drop are used in combination with spacers and spacer attached devices tending to utilize pressure drop to improve critical power. The addition of the part length rods has the advantage of lowering the pressure drop. Attached devices substantially increase the pressure drop. Exemplary spacer attached mechanisms for the utilization of pressure drop are set forth including vanes--preferably swirl vanes on the spacers, decreasing the spacer pitch to increase the total number of spacers in the upper two phase region of the fuel bundle, increasing the vertical height of the spacers, and increasing the thickness of the metal from which the spacers are constructed. Two classes of separation devices are disclosed for placement in the volume overlying the end of the partial length fuel rods.

Abstract: A boiling water reactor comprises a reactor pressure vessel accommodated in a vertical fashion, a core disposed at a low portion in the reactor pressure vessel, a plurality of control rods to be inserted from an upper side of the core into the spaces between adjacent fuel assemblies and withdrawn therefrom upwardly, a shroud surrounding the fuel assemblies so as to define the core and having an upper end opening, a shroud head which closes the upper end opening of the shroud and through which the control rods are inserted or withdrawn, a separator standing upward from the shroud head to carry out gas-water separation of steam generated from the core, a fixing pedestal disposed above the separator, a control rod driving mechanism mounted on the fixing pedestal and adapted to drive the control rods, a drier unit including a plurality of drier elements annularly arranged along an upper inner wall surface of the reactor pressure vessel and adapted to dry the steam passing through the steam flow hole of the fixing

Abstract: An improved fuel rod is provided having a part-length fuel rod portion that improves performance with respect to typical part-length fuel rods without significant degradation of the benefits that are achieved by using such a system, e.g., improved fuel utilization, stability, and shut down margin. The present invention provides a fuel rod for a light water nuclear reactors that comprises a part-length fuel rod and an extension tube having at least one wall member defining an enclosed flow path therethrough, the extension tube being coupled to a portion of the part-length fuel rod so as to be disposed axially above the part-length fuel rod, and including at least one inlet opening, for allowing fluid that surrounds the rod and initially comprises a two phase mixture of steam and liquid, to enter the enclosed fluid path and at least one outlet opening located above the inlet opening, the extension tube includes means for separating at least some of the steam located in the fluid from the liquid located therein.

Abstract: The present invention is directed to a modular steam separator with integrated dryer especially adapted for separating and drying steam exiting the core of a nuclear boiling water reactor. The instant modular separator with integrated dryer has a standpipe with a proximal end that is connectable to the upper plenum of the core of the nuclear reactor and a distal end that is connected to a proximal end of a steam separator. A distal end of the steam separator is connected to a steam distribution channel that extends in fluid communication to a steam dryer. The steam dryer has a steam vent for passage of dry steam to the steam dome of the reactor and a water drain connected to the reactor's downcomer region.

Abstract: A phase-separator assembly for a boiling-water nuclear reactor includes a steam-separator and a dryer. The steam separator and dryer are mechanically coupled so that relative vertical movement is permitted therebetween. The mechanical coupling limits this relative vertical movement. When installed in a reactor, the steam separator and dryer are independently supported. The dryer is supported so as to define a gap between the dryer and steam separator that optimizes their collective performance. When in storage, the dryer is not independently supported. Instead, the dryer is dropped to a minimum height above the steam separator, providing for compact storage.

Abstract: A latch assembly removably joins a steam separator assembly to a support flange disposed at a top end of a tubular shroud in a nuclear reactor pressure vessel. The assembly includes an annular head having a central portion for supporting the steam separator assembly thereon, and an annular head flange extending around a perimeter thereof for supporting the head to the support flange. A plurality of latches are circumferentially spaced apart around the head flange with each latch having a top end, a latch hook at a bottom end thereof, and a pivot support disposed at an intermediate portion therebetween and pivotally joined to the head flange. The latches are pivoted about the pivot supports for selectively engaging and disengaging the latch hooks with the support flange for fixedly joining the head to the shroud or for allowing removal thereof.

Abstract: A natural circulation boiling water reactor system comprises a reactor vessel enclosing a reactor core, for generating steam to drive a turbine which can drive a generator to generate electricity. The vessel includes a chimney for guiding the recirculating water and steam vertically above the core and a dryer for helping to remove water from steam exiting the vessel toward the turbine. In contrast to prior reactor systems, the chimney is height-staggered so that its central sections are taller than its peripheral sections. Likewise, a dryer is elevation-staggered. This staggering minimizes carryover, water in the steam flow to the turbine, and carryunder, steam in the water recirculating through the core. In addition, the staggered chimney causes the fastest recirculation flow through the hottest portions of the core. The overall effect is a more efficient reactor system.

Abstract: Part length water regions are located above part length fuel rods in boiling water nuclear reactor fuel bundles. The part length water regions include discrete containers having entry ports at the top of the part length water regions for capturing water, and vent ports for permitting internally generated steam to escape. The advantages of improved neutron moderation in the upper portion of the fuel assembly are maintained while the uranium fuel removal requirements are minimized.

Abstract: A fuel bundle for a boiling water nuclear reactor having an improved water rod is disclosed, this water rod having two discrete compartments upper and lower for containing water. The bottom compartment flows moderator from the bottom of the fuel bundle through the water rod compartment to discharge points located through the water rod side walls between the upper most spacers; the top compartment opens upwardly and is naturally filled with liquid moderator settling out of the upwardly flowing moderator during reactor operation. There results the requisite presence of liquid moderator within the water rod for supplying the upper two phase region of the fuel rod with nearly full moderator density. At the same time, water flow through of the water rod from the bottom of the fuel bundle to the upper two phase region of the fuel bundle improves the thermal hydraulic performance.

Abstract: In a fuel bundle for use in the core of a boiling water nuclear reactor, part length rods having a tendency to reduce pressure drop are used in combination with spacers and spacer attached devices tending to restore pressure drop to improve critical power. The addition of the part length rods has the advantage of lowering the pressure drop. Attached devices substantially recapture the pressure drop. Exemplary spacer attached mechanisms for the recapture of pressure drop are set forth including vanes--preferably swirl vanes on the spacers, decreasing the spacer pitch to increase the total number of spacers in the upper two phase region of the fuel bundle, increasing the vertical height of the spacers, and increasing the thickness of the metal from which the spacers are constructed. Two classes of separation devices are disclosed for placement in the volume overlying the end of the partial length fuel rods.

Abstract: A nuclear reactor with a recirculating heat transfer fluid has a bi-level core which provides enhanced flexibility in fuel arrangement. The bi-level core includes a first core, a plurality of steam separators disposed above the first core, and a second core disposed above the steam separators all inside a single pressure vessel. The steam separators receive a steam and water mixture from the first core and separate the water from the steam. The separated steam is channeled to the second core which cools the second core resulting in the generation of superheated steam. Preferably, fuel bundles of the second core are arranged in vertical alignment with fuel bundles of the first core. This permits a fuel bundle of the first core to be accessed by removing only the adjacent fuel bundle of the second core. During refueling operations, fuel bundles can be shifted from one core to the other, providing additional flexibility in arranging units at various states of burnup.

Abstract: A natural circulation boiling water reactor system comprises a reactor vessel enclosing a reactor core, for generating steam to drive a turbine which can drive a generator to generate electricity. The vessel includes a chimney for guiding the recirculating water and steam vertically above the core and a dryer for helping to remove water from steam exiting the vessel toward the turbine. In contrast to prior reactor systems, the chimney is height-staggered so that its central sections are taller than its peripheral sections. Likewise, a dryer is elevation-staggered. This staggering minimizes carryover, water in the steam flow to the turbine, and carryunder, steam in the water recirculating through the core. In addition, the staggered chimney causes the fastest recirculation flow through the hottest portions of the core. The overall effect is a more efficient reactor system.

Abstract: A natural circulation boiling water reactor system using free-surface steam separation incorporates a series of tubes near the inner wall of its reaction vessel extending from a downcomer to well-above the downcomer. These tubes allow steam bubbles which would otherwise be trapped within the downcomer to escape from the recirculating water toward the steam exit of the vessel. This lowers the volume of steam in the downcomer, lowering the water velocity required to maintain a given volume of water recirculation. The reduced water velocity results in less carryunder which results in smaller voids in the reactor core. The smaller voids provide longer fuel burnups and enhance reactor stability.

Abstract: The present invention is directed to gas-liquid separators especially adapted for the separation of steam exiting the core of a nuclear boiling water reactor that utilizes natural circulation. Such separator has a barrel having a longitudinal axis and width, has an inlet and an outlet, and has a plurality of spaced-apart pickoff rings in fluid communication with annular flow discharge passages. The improved separator of the present invention comprises the pickoff rings having curvilinear shape to direct flow into the flow discharge passages. A twisted strip swirler is positioned along the axis of the barrel after the initial pickoff ring and does not extend the full width of the barrel. The width of the barrel increases at each succeeding pick-off ring from the barrel inlet to the barrel outlet. Advantageously, a low expansion angle exists between the rings and the top of the separator barrel.

Abstract: A steam separator for a boiling water reactor includes a pressure vessel and a chimney spaced radiallly inwardly therefrom to define a downcomer therebetween for recirculating water, the chimney being disposed above a reactor core for channeling upwardly therefrom steam voids and water flow. An annular partition wall is spaced radially between the vessel and he chimney to define an annular collection chamber having an inlet for receiving a portion of the steam voids and water flow from the chimney, a steam outlet for discharging the steam voids from the chamber, and a flow outlet for discharging the water flow from the chamber into the downcomer.

Abstract: In a fuel bundle for a boiling water reactor having one or more part length rods in the two phase region, a steam vent tube is introduced overlying the part length rods. The fuel bundle includes a lower tie plate for admitting water moderator and supporting a plurality of fuel rods in upstanding side-by-side relation, an upper tie plate for permitting water and steam to be discharged from the top of the fuel bundle and maintaining the fuel rods in upstanding side-by-side relation, a surrounding fuel channel for confining moderator flow along a path over the fuel rods and between the tie plates, and dispersed vertically intermittent spacers for maintaining the fuel rods in their designed side by side relation. One or more fuel rods extends from the lower tie plate vertically less than the full length to the upper tie plate ending interior of the fuel bundle at a disposition where the upper end of the part length rods is braced in the vertical position by a spacer.

Abstract: The present invention is directed to a separator for dividing a steam/water mixture into its liquid and steam components. The inventive separator comprises a pipe having an annular spiral strip which is attached to its inside wall, said pipe being in fluid communication with ports for removal of liquid water divided from said mixture. The width of the annular spiral strip preferably is about 1/10th to 1/20th of the diameter of the pipe to which it is attached. A method for dividing steam/water mixtures into their liquid and steam components by passing such mixture through the inventive separator forms yet another aspect of the present invention.

Abstract: A natural circulation boiling-water reactor system using free-surface steam separation incorporates a steam separator near the inner wall of its reaction vessel and extending into a downcomer. Steam so collected supplements the main steam flow from the reactor vessel to drive a turbine, which in turn drives a generator. A flow controller opens and closes a valve to adjust the flow of steam from the steam collector to the turbine. The flow controller can be programmed to implement a predetermined power output level or to adjust power output as a function of load or time. When this level is exceeded, as indicated by feedback from the generator, the flow controller valve is constricted. The auxiliary steam flow to the turbine is directly decreased, reducing power output. Concomitantly, less steam is removed from the steam collector, and thus from the downcomer. As a result there is more carryunder steam, which reduces the power generated at the reactor core.

Abstract: An improved separating system for boiling water nuclear reactors comprising a combination of mechanical steam separators with liquid water collecting and transferring devices.

Abstract: A boiling water nuclear fission reactor is disclosed with a unique steam-water separating system. The steam-water separation means comprises an assemblage of open troughs positioned above the fuel core which reduces the amount of steam recycled through the coolant circuit.

Abstract: A natural circulation type boiling light-water reactor comprises a pressure vessel, a reactor core disposed within said pressure vessel to heat light water so as to generate main steam, a steam outlet provided in a wall of said pressure vessel for drawing out the main steam therethrough to supply the same to a turbine system, and a steam path along which the main steam flows from the reactor core to the steam outlet. The reactor further comprises a steam guide for prolonging the steam path and/or a radially increased chimney for reducing the velocity of the main steam flowing through the steam path. These causes radioactive isotope .sup.16 N contained in the main steam to flow within the pressure vessel for a time period exceeding its own half-life, so that the inventory of .sup.16 N in the main steam directed towards the turbine system is reduced remarkably. In consequence, shield structures for piping and turbine systems can be reduced in size and weight.

Abstract: A steam separating system for boiling water nuclear reactors comprising a combination of mechanical steam separators with steam collecting and transferring units.

Abstract: The improvement in a nuclear reactor having a calandria tank containing moderator and a plurality of coolant flow channels which penetrate through the calandria tank and are loaded with fuel assemblies, the moderator and the coolant being isolated from each other. The improvement is constituted by a pressure container surrounding the outside of the calandria tank, a gap between the calandria tank and the pressure container being charged with the coolant; a recirculation pump for recirculating the coolant through the coolant flow channels; and a steam separator which is positioned inside the pressure container and separates the coolant flowing through the coolant flow channels into steam and water; whereby an improved nuclear reactor having a unitary pressure container structure is constructed.