Abstract: An emergency core cooling system directly injects emergency core cooling water, which is supplied from a high-pressure safety injection pump or a safety injection tank for a pressurized light water reactor, into a reactor vessel downcomer. A pipe connector is completely removed from between each direct vessel injection nozzle and each injection extension duct installed on an outer surface of the core barrel, which are opposite to each other. An emergency core cooling water intake port, through which the water is injected from each direct vessel injection nozzle, is formed on the surface of each injection extension duct facing an axis of each direct vessel injection nozzle. Thereby, a structure in which a jet of the emergency core cooling water flows into the injection extension ducts is adopted in a hydraulic connection fashion.

Abstract: An object of the present invention is to provide an accumulator including a flow damper which is capable of performing a control so that a vortex may not be formed in a vortex chamber at the time of a large flow injection without requiring huge labors and fabrication costs. The flow damper is configured of a colliding jet controller (a bevel or a projection) for controlling a colliding jet composed of a jet from a large flow pipe and a jet from a small flow pipe flowing into a vortex chamber at the time of a large flow injection so that the colliding jet may proceed directly to an outlet without forming a vortex in the vortex chamber. The colliding jet controller is provided at a junction of an inner surface of the small flow pipe and an inner surface of the vortex chamber.

Abstract: An assembly includes a base grid configured to be disposed below a pressure vessel and spaced vertically above a floor of a containment vessel to define a sump therebetween. The assembly further includes an annular wall extending vertically upwards from the floor and laterally bounding the base grid and the sump. The wall separates the sump from a suppression pool, an inlet passage extending through the wall and providing flow communication between the sump and the suppression pool, and an outlet passage extending through the wall and providing flow communication between the sump and the suppression pool.

Abstract: A power module assembly includes a reactor vessel containing a reactor core surrounded by a primary coolant. A containment vessel is adapted to be submerged in a containment cooling pool and to prohibit a release of the primary coolant outside of the containment vessel. A secondary cooling system is configured to remove heat generated by the reactor core. The heat is removed by circulating liquid from the containment cooling pool through the primary coolant.

Abstract: A nuclear facility contains a flood tank, which is provided for holding a cooling liquid, a condensation chamber, and an overflow device, which leads from the flood tank to the condensation chamber and which serves to discharge excess cooling liquid. The overflow device is provided for separating gas components out from the excess cooling liquid. In certain operating states, the cooling liquid of the condensation chamber and of the flood tank is circulated in a common cooling circuit and is fed, while being largely free of gas, once more into the condensation chamber via the overflow device.

Abstract: A boiling water nuclear reactor comprises: a reactor containment vessel including a dry well and a wet well; a vent pipe connecting the dry well and the pressure suppression pool; a gravity-driven water injection pool to hold boric acid aqueous solution; an emergency core water-injection piping system for causing the boric acid aqueous solution in the gravity-driven water injection pool to fall so as to be injected into the reactor pressure vessel in case of reactor accident; a static containment vessel cooling system pool; a static containment vessel cooling system heat exchanger; a dry well connection pipe connecting an upper part of the static containment vessel cooling system heat exchanger and the dry well; and a gas vent pipe for discharging noncondensible gas in the static containment vessel cooling system heat exchanger into the inside of the pressure suppression pool.

Abstract: A constrained feedwater sparger end bracket assembly comprises a boiling water reactor vessel, a feedwater sparger including a conduit within the vessel, a feedwater sparger end bracket assembly connected to an end of the conduit at a sparger/bracket junction, and a clamp secured on the feedwater sparger end bracket assembly. The clamp constrains the feedwater sparger end bracket assembly in directions horizontal, vertical and radial to the vessel.

Abstract: An emergency core cooling system is provided with a hybrid safety system composed of an active safety system and a static safety system for ensuring the safety against a severe natural phenomenon such as a giant earthquake and a mega hurricane. An emergency core cooling system for a boiling water reactor includes four safety divisions in total: three safety divisions for an active safety system having a high pressure reactor core cooling system, a low pressure reactor core cooling system, a residual heat removal system, and an emergency diesel generator; and one safety division for a static safety system having an isolation condenser, a gravity drop reactor core cooling system, and a static containment vessel cooling system.

Abstract: A feeding system for an absorber liquid containing a neutron poison, in particular for a quick shut-down of a nuclear reactor, has a storage container for the absorber liquid and is configured for high operational reliability with simple construction. In particular, a chemical decomposition of the absorber liquid or corrosion of the container wall of the storage container is to be excluded. For this purpose, the storage container is connected to a pressure container via an overflow line, wherein the pressure container is filled with a motive fluid.

Abstract: A nuclear power plant with an improved cooling system using nanoparticles in solid or fluid form to improve heat transfer and reduce corrosion is provided. The nanoparticles are delivered to a closed cooling circuit such as a CCWS. Methods for providing the nanoparticles are also provided.

Abstract: A nuclear power plant provides for delivery of nanoparticles to coolant found in the containment, for example during severe accident scenarios. The nanoparticles advantageously can be delivered passively or actively independently of any emergency core cooling system. The nanoparticle supply can include for example tanks storing nanofluids or solid nanoparticles, or dissolvable paints containing nanoparticles. Methods for providing the nanoparticles are also provided.

Abstract: A nuclear power plant with an improved cooling system using nanoparticles in solid or fluid form is provided. The nanoparticles are delivered in locations such as the cold leg accumulator and high and low pressure pumps of an emergency core cooling system. Motor driven valves and pressurization can aid in the delivery. Methods for providing the nanoparticles are also provided.

Abstract: An object of the present invention is to provide an accumulator including a flow damper which is capable of performing a control so that a vortex may not be formed in a vortex chamber at the time of a large flow injection without requiring huge labors and fabrication costs. The flow damper is configured of a colliding jet controller (a bevel or a projection) for controlling a colliding jet composed of a jet from a large flow pipe and a jet from a small flow pipe flowing into a vortex chamber at the time of a large flow injection so that the colliding jet may proceed directly to an outlet without forming a vortex in the vortex chamber. The colliding jet controller is provided at a junction of an inner surface of the small flow pipe and an inner surface of the vortex chamber.

Abstract: A core spray sparger T-box clamp for a sparger T-box in a shroud of a nuclear reactor pressure vessel, the sparger T-box clamp including: an anchor plate substantially aligned with a closed end of the T-box; a carrier plate slidably secured to an upper side the anchor plate and latched to the T-box; a saddle bracket secured to a lower side of the anchor plate and latched to the T-box, and a pair of clamp blocks on opposite sides of the anchor plate fixed to sparger pipes coupled to the T-box.

Abstract: A reactor feedwater system of a boiling water reactor includes: a reactor feedwater pump and a high pressure feedwater heater, that are arranged at an outside of a reactor containment vessel containing a reactor pressure vessel of a boiling water reactor, for pressurizing and heating a coolant; a main feedwater pipe for supplying the coolant, that are pressurized and heated by the reactor feedwater pump and the high pressure feedwater heater, to a side of the reactor containment vessel; and a plurality of branch pipes, that are connected to the main feedwater pipe, for pouring the coolant into the reactor pressure vessel. The main feedwater pipe is provided to the outside of the reactor containment vessel, and branching positions at which the branch pipes are branched from the main feedwater pipe are set to the outside of the reactor containment vessel, so that only the branch pipes penetrate through the reactor containment vessel and are connected to the reactor pressure vessel.

Abstract: This invention relates to a nuclear reactor plant which includes a nuclear heat source (12), and a cooling system (10). The cooling system (10) includes at least two cooling circuits (26), each of which includes a plurality of coolant chambers (18) each having an inlet (40) and an outlet (42), the coolant chambers (18) being arranged around the nuclear heat source (12). The cooling system (10) further includes pump means (52) for pumping coolant to and from the coolant chambers (18), the volumetric capacity of the coolant chambers (18) being sufficiently large such that, when in a passive mode, the temperature of a water coolant in the coolant chambers (18) will remain below boiling point for at least eight hours.

Abstract: A core spray T-box attachment assembly for a core spray nozzle includes a primary cruciform wedge and a secondary cruciform wedge in contact with the primary cruciform wedge to form a cruciform wedge subassembly adapted for insertion within a bore of the core spray nozzle to sealingly engage an interior converging portion of a safe end of the core spray nozzle. The assembly includes a spider in contact with the cruciform wedge subassembly, and a draw bolt engaging an axial bore of a center portion of the cruciform wedge subassembly and the spider to the T-box.

Abstract: A direct vessel injection-type pressurized light water reactor (DVI-PLWR), in which an emergency core cooling water (ECC) is directly injected into a downcomer of a reactor vessel, is disclosed. In order to reduce the ratio of ECC bypass from the downcomer to a broken area of a cold leg in the case of a cold leg guillotine break (CLGB), such as a double-ended guillo4tine break (DEGB), a plurality of corrugations, having a V-shaped cross-section, are vertically arranged around each of the inner surface of a pressure vessel and the outer surface of a core barrel at regular intervals, with a vertical groove formed between two neighboring corrugations. The grooves phase-separate the ECC from a high-speed lateral flow of fluid running in the downcomer, and the separated ECC stagnates in the form of vortexes in the grooves, prior to flowing down to the lower section of the downcomer due to gravity.

Abstract: In order, in a pressure accumulator, to generate a required operating pressure of a fluid situated in the pressure accumulator, a heater device is provided, disposed in an upper region of the pressure accumulator. The device generates a vapor cushion and the required operating pressure. Where necessary, when the fluid flows out, the pressure in the pressure accumulator is automatically reduced after the level has fallen below a defined filling level, as a result of the vapor condensing at a cold insulating device with a high heat-accumulation capacity. The pressure accumulator is preferably used as an emergency shut-down tank or as an emergency accumulator in a nuclear power plant.

Abstract: In order to allow a reliable and passive external cooling of a reactor pressure vessel of a boiling water reactor, outside the reactor pressure vessel a differential-pressure measurement pipe is provided and has a first and a second pipe leg which are connected to one another above a critical filling level. The first pipe leg is connected at the height of the critical filling level to the interior of the reactor pressure vessel. In a normal operating state, the differential-pressure measurement pipe is filled completely with water. In the event of the undershooting of the critical filling level, the water flows automatically out of the first pipe leg. As a result, the differential pressure between the two pipe legs rises, the differential pressure being detected by a measurement device via which the flooding of the exterior is then brought about.

Abstract: Control device for a cooling circuit which enables a pressure tank of a reactor to be cooled even when a serious failure occurs, without having to resort to the use of external energy. One or more rods is disposed below a bottom cap of the reactor pressure tank. Each rod is connected to an emergency cooling system by a transmission system. The end of each rod opposite the transmission system is arranged at a distance of approximately 3 cm from the bottom cap. A hydraulic system is used advantageously as a transmission system. Each rod is placed vertically on a hydraulic cylinder arranged in a parallel position with respect to the axis of the reactor pressure tank, and each cylinder is connected to the emergency cooling system. When several hydraulic cylinders are used, they are connected to each other by hydraulic lines.

Abstract: A direct vessel injection-type pressurized light water reactor (DVI-PLWR), in which an emergency core cooling water (ECC) is directly injected into a downcomer of a reactor vessel, is disclosed. In order to reduce the ratio of ECC bypass from the downcomer to a broken area of a cold leg in the case of a cold leg guillotine break (CLGB), such as a double-ended guillo4tine break (DEGB), a plurality of corrugations, having a V-shaped cross-section, are vertically arranged around each of the inner surface of a pressure vessel and the outer surface of a core barrel at regular intervals, with a vertical groove formed between two neighboring corrugations. The grooves phase-separate the ECC from a high-speed lateral flow of fluid running in the downcomer, and the separated ECC stagnates in the form of vortexes in the grooves, prior to flowing down to the lower section of the downcomer due to gravity.

Abstract: The present invention is characterized by a reactor cooling system, which comprises a lower drywell which is a space for containing a bottom side portion of the reactor pressure vessel, the lower drywell being disposed in a lower portion of the reactor pressure vessel; reactor recirculation pumps for circulating cooling water in the reactor pressure vessel, the reactor recirculation pump being disposed in the bottom side portion of the reactor pressure vessel in such a manner that a side of a motor portion of the reactor recirculation pump is projected into the lower drywell; and heat exchangers disposed in the lower drywell, the cooling water circulated by the reactor recirculation pump passing through the heat exchanger, wherein number of the reactor recirculation pumps is 4 or 6, and the reactor recirculation pumps are arranged with nearly equal angular spacing.

Abstract: A method and system of regulating an output voltage of a boiling water reactor nuclear reactor plant recirculation system motor generator are provided. The method includes sensing an alternator output voltage and transmitting an alternator output voltage signal to a voltage regulator circuit, sensing an alternator speed and transmitting an alternator speed signal to the voltage regulator circuit, comparing the alternator output voltage signal to the alternator speed signal with a volts per hertz divider network electrically coupled to the alternator output voltage sensing circuit and the alternator speed sensing device, adjusting a capacitive reactance of the voltage regulator with a lead compensation circuit electrically coupled in series with the volts per hertz divider network, and adjusting a current in a control winding of a saturable reactor.

Abstract: A fixture for cooling a core of a nuclear reactor, in particularly for a boiling water reactor, has spray nozzles and are disposed above the core. It is provided that the distributor pipes are mounted in displaceable fashion. In this manner, mechanical damage from thermal expansion and contraction is limited or avoided altogether.

Abstract: The invention relates to a control device for a cooling circuit. The inventive control device ensures in a simple and reliable manner that the pressure tank of a reactor can be cooled even when a serious failure occurs, without having to resort to the use of external energy. According to the invention, at least one rod (9) is disposed below the bottom cap (6) of the reactor pressure tank (1). Said rod is connected to the emergency cooling system by means of a transmission system. The end of the rod (9) opposite the transmission system is arranged at a distance of approximately 3 cm from the bottom cap (6). A hydraulic system is used advantageously as a transmission system. The rod (9) is placed vertically on a hydraulic cylinder (7) arranged in a parallel position with respect to the axis of the reactor pressure tank (1), said cylinder being connected to the emergency cooling system. When several hydraulic cylinders (7) are used, they are connected to each other by means of hydraulic lines (8).

Abstract: A nuclear reactor containment cooling system includes a containment vessel having a drywell and a wetwell, a cooling condenser submerged in a cooling pool of water located outside the containment vessel, a vent line extending from the condenser to a suppression pool disposed in the wetwell, and at least one drain line extending from the condenser to a condensate drain tank located in the drywell. An end of the drain line is vertically submerged below the surface of a pool of water in the drain tank. To enhance flow, a blower can be located in the drain line. The containment cooling system can include a drywell gas recirculation subsystem coupled to the vent line, and including a suction pipe coupled to the vent line, at least one valve located in the suction pipe, at least one blower coupled to the suction line, and a discharge pipe in flow communication with the drywell.

Abstract: In order to allow a reliable and passive external cooling of a reactor pressure vessel of a boiling water reactor, outside the reactor pressure vessel a differential-pressure measurement pipe is provided and has a first and a second pipe leg which are connected to one another above a critical filling level. The first pipe leg is connected at the height of the critical filling level to the interior of the reactor pressure vessel. In a normal operating state, the differential-pressure measurement pipe is filled completely with water. In the event of the undershooting of the critical filling level, the water flows automatically out of the first pipe leg. As a result, the differential pressure between the two pipe legs rises, the differential pressure being detected by a measurement device via which the flooding of the exterior is then brought about.

Abstract: The present invention is used to reduce thermal load itself, being the cause to generate stress, which develops near liquid surface in a nuclear reactor wall and to contribute to further improvement of safety. A partition member (5) is arranged above a coolant liquid surface (9) in an annulus space (3) between a reactor vessel (1) and a guard vessel (2), a low-temperature gas is circulated through the annulus space above the partition member to cool down, the gas is circulated through the annulus space from under the coolant liquid surface to the partition member, and the high-temperature gas heated under the coolant liquid surface is used to raise the temperature above the coolant liquid surface.

Abstract: A method for operating a system having a plurality of modes and interlocks between the modes is provided. The method includes operating the system in a first mode and switching the system to a second mode without going to a standby mode.

Abstract: A core spray sparger assembly for supplying coolant to a nuclear reactor. The nuclear reactor includes fuel assemblies, a top guide, coolant supply pipes and a shroud head. The core spray sparger assembly includes at least one coolant manifold, at least one coolant coupling in fluid communication with the coolant manifold, and at least one mounting device configured to couple the coolant manifold to the nuclear reactor. The core spray sparger assembly further includes a plurality of fluid conductors in a parallel array positioned above the fuel assemblies, the fluid conductors in fluid communication with the coolant manifold, and a plurality of nozzles in fluid communication with the fluid conductors.

Abstract: A beam pipe (46) for guiding in an accelerator-driven nuclear system an accelerated particle beam (44) through a coolant in a primary vessel (12) onto a spallation target (30) comprises, preferably near its tip end (48), a temperature triggered flooding device, including for example a melt-rupture disc. In case of an abnormal temperature increase in the system, the temperature triggered flooding device establishes, below the normal coolant level (16), a flooding communication between the vessel (12) and the interior of the beam pipe (46), thereby flooding the interior of the beam pipe (46) with the coolant (14) contained in the vessel (12).

Abstract: A core spray sparger for use in a nuclear reactor pressure vessel. The core spray sparger includes a plurality of core spray lines, a coupling apparatus, a bracket assembly, and an end clamp assembly. The core spray line includes a core spray line end cap.

Abstract: A flexible penetration attachment for BWR wet-well strainers is provided that causes a suction pipe to communicate with liquid in the wet-well through an aperture in a wet-well wall. The penetration includes a boot for defining an outer circumference of the aperture. A suction pipe having an outer surface extends through the aperture such that an annular space is defined between the aperture outer circumference and the suction pipe outer surface. A resilient seal having a generally U-shaped cross section with first and second ends is placed within the annular space. The first end is fixedly secured to the outer surface of the suction pipe and the second end is fixedly secured to the aperture outer circumference such that the suction pipe may move in response to a force applied to the suction pipe.

Abstract: A core spray sparger T-box attachment assembly for a nuclear reactor pressure vessel includes a downcomer pipe coupling and a sparger T-box clamp. The downcomer pipe coupling includes a cylindrical outer housing, a center portion, and a plurality of vanes extending the outer housing to the center portion. The outer housing is coupled to a downcomer pipe and includes an extending flange. A draw bolt threadedly engages an axial bore in the center portion, and connects the downcomer pipe coupling to the sparger T-box clamp. The sparger T-box clamp includes an anchor having a draw bolt opening, and a plurality of legs extending from a face of the anchor. Clamp blocks are connected to the anchor. Stop bolts extend through stop bolt openings in the clamp blocks. Clamping elements are connected to the clamp blocks by clamp bolts. A seal plate having a draw bolt opening is coupled to the anchor with a plurality of adjusting screws.

Abstract: The present invention provides a boiling water-type nuclear power plant comprising: a passive safety system having depressurization valves and a gravity driven core cooling system as an emergency core cooling system; a passive containment vessel cooling system in which reactor steam released in the containment vessel is cooled by a heat exchanger in a cooling water pool installed in the upper portion of the containment vessel; and a containment vessel flooding system which injects cooling water into a dry well of the containment vessel on an accident; wherein a containment vessel spray cooling system for injecting cooling water into the containment vessel via a pump is further added as a safety system.

Abstract: A T-box assembly includes a T-box housing, a thermal sleeve coupled to the T-box housing, a cruciform wedge, a spider threadedly engaging the thermal sleeve, and a draw bolt coupling the cruciform wedge and the spider. At least one spring washer is located between the end of the thermal sleeve and the end of a core spray nozzle safe end. The T-box housing includes a cover opening having a plurality of breach lock lugs extending into the cover opening. A T-box cover plate includes a head portion and an insertion portion. A plurality of breach lock lugs extend from the periphery of the insertion portion. A plurality of ratchet teeth extend around the periphery of the head portion. A lock spring includes an engagement portion having a plurality of ratchet teeth sized to mesh with cover plate ratchet teeth.

Abstract: A heat removal system for the under reactor pressure vessel area of a boiling water nuclear reactor system that provides both protection of the containment boundary from attack by molten core debris and cools the molten core debris to prevent a breach of the containment boundary in the unlikely event of a severe accident where the molten core penetrates the lower head of the reactor vessel is described. The heat removal system includes a glass matrix slab positioned adjacent the floor of the containment and a plurality of heat tubes at least partially embedded in the glass matrix slab and extending into the area under the nuclear reactor pressure vessel. The cooling system also includes a passive containment cooling system, and fused vent pipes connecting the suppression pool with the drywell.

Abstract: A T-box/thermal sleeve assembly replaces a damaged T-box/thermal sleeve in a core spray nozzle of a nuclear reactor. To replace the parts, the T-box and a portion of the extant thermal sleeve are removed from a location within the reactor vessel wall. The end of the thermal sleeve remnant is smoothed and a groove is formed along its interior surface. A replacement T-box/thermal sleeve and collet assembly are inserted into the nozzle bore from the interior of the vessel wall. The collet has axially projecting fingers with radial flanges for engaging in the groove to form a mechanical connection between the thermal sleeve remnant and the T-box/thermal sleeve replacement. A Belleville spring washer is interposed between the assembly and thermal sleeve remnant to place both parts in compression. A retention sleeve is screwthreaded within the replacement thermal sleeve to lock the fingers from radial movement.

Abstract: A passive pulse generator can be connected to a line in order to activate a safety fitting in a nuclear power plant. The line can be closed by a closure element. In the event of a temperature change in the vicinity of the pulse generator, the closure element is actuated solely as a result of a thermal volume change of an actuating element, so that the line is released. The pulse generator therefore activates the fitting passively, without additional control pulses. A method for activating a fitting with a passive pulse generator is also provided.

Abstract: A collar clamp assembly is disclosed for repairing and providing a temporary seal around leaking pipe coupling areas of an internal core spray system of a nuclear reactor. The clamp assembly includes first and second housings having respective first and second ends and a pair of longitudinal edges between the ends. The housings have a tongue and groove mating configuration along the longitudinal edges to seal and accommodate variations in the outside diameter of the core spray piping. A plurality of threaded fasteners are used to secure the first and second housings together to form a closed conduit shaped to receive a length of the core spray piping, including the leaking pipe coupling. First and second seals are located at first and second longitudinally spaced positions, respectively, on each of the first and second housings and extend around the closed conduit.

Abstract: A nuclear reactor plant with a light water reactor comprises a containment (1) having an upper space (2) and a lower space (3). The lower space is separated from the upper space by a separating member (4) and arranged to house a cooling medium (16). Furthermore, the plant comprises a reactor vessel (9) housing a reactor core (10) and provided in the upper space (2). The separating member (4) comprises a portion (7) which is arranged to be located at such a position that the surface portion (7) facing the lower space (3) is in contact with the cooling medium (16). The reactor vessel is provided above the portion (7).

Abstract: Modified passive containment cooling systems for cooling a reactor core of a boiling water nuclear reactor are described. The reactor core is positioned in a reactor pressure vessel which is located in a drywell of the nuclear reactor. The passive containment cooling system (PCCS), in one form, includes an IC/PCC pool, a GDCS pool, a suppression pool, and a condensate drain tank. The IC/PCC and the GDCS pool each are substantially isolated from the drywell, and the suppression pool is separated from the drywell by a wall having a spill-over hole therein. An equalizing line extends between the suppression pool and the RPV and is configured to transport water from the suppression pool to the RPV. The condensate drain tank is positioned in the drywell and includes a base wall having a sidewall extending therefrom to define a fluid retaining cavity. A steam inlet line extends from within the drywall to a set of passive containment cooling condensers, which condense steam generated within the drywall to water.

Abstract: Downcommer coupling apparatus and methods for replacing a core spray line downcommer pipe coupled to a shroud T-box are described. In one embodiment, the coupling apparatus includes a wedge flange, a wedge, a wedge housing, a pipe seal, a cylindrical pipe, an elbow, a lower flange, and a shroud seal. The downcommer pipe is connected to the coupling apparatus by extending the pipe through the wedge flange, the wedge, and the wedge housing. The wedge has a plurality of flexible thinned segments that extend into the wedge housing to secure the downcommer pipe to the wedge housing. Wedge flange bolts extend through the wedge flange, the wedge, and the wedge housing to rigidly secure the downcommer pipe to the coupling apparatus. Dowel bolts extend through the wedge housing and the downcommer pipe to provide vertical and torsional load transfer from the downcommer pipe to the coupling apparatus. The lower flange is configured to receive the shroud T-box.

Abstract: A T-box assembly to facilitate attaching a core spray line to a reactor core spray nozzle safe end without welding is described. In one embodiment, the T-box assembly includes a T-box housing, a cruciform wedge, and a draw bolt. The T-box housing is configured to be positioned so that a first end is located inside a core spray nozzle and engages the core spray nozzle safe end. Two other ends are configured to be in substantial alignment and configured to couple to core spray line header pipes. The T-box housing also includes a cover opening configured to receive a T-box cover plate. The T-box cover plate includes a draw bolt opening configured to receive the draw bolt. The first end of the T-box also includes a plurality of positioning lugs configured to engage the core spray nozzle to center the T-box housing in the nozzle bore. The cruciform wedge includes four web members extending from a central member and configured so as to form an X shaped configuration.

Abstract: A gap forming structure for use with water cooled nuclear reactors is invented to prevent overheating and ultimately structurally failing of the lower head of a reactor vessel in a nuclear reactor core meltdown accident by virtue of a cooling effect in the gap structure for facilitating the retention of accumulated molten core debris. Single layer or multilayer gap structures can be installed either inside or outside the vessel lower head by joining, or fastening structures or secured to the instruments/control guide tubes within the vessel. The water cooling capacity inside the gap can prevent the vessel lower head from overheating and subsequently failing and thus defend against severe accidents by preventing the lower head of the reactor vessel from rupturing.

Abstract: A nuclear reactor coolant system includes a primary coolant circuit connected to a secondary coolant circuit. A desired amount of coolant is bled from the primary circuit to the secondary circuit for purification and controlling chemical composition of the coolant. Variable speed charging pumps are provided in the secondary circuit to pump coolant back into the primary circuit at variable pressures and flow rates. A pressurizer level control system is also disclosed for controlling pump speeds.

Abstract: Coupling apparatus and methods for replacing a core spray line downcomer pipe coupled to a shroud T-box are described. In one embodiment, the coupling apparatus includes a seal ring, a mating flange, a housing, at least one coupling bolt, at least one spherical washer, and at least one lateral pin. The thermal expansion coefficient of the coupling bolt is lower than the thermal expansion coefficient of the seal ring, mating flange, and housing. After extending the downcomer pipe into the housing, the seal ring is inserted into the opposite end of the housing adjacent the downcomer pipe. The seal ring is then seated on the mating flange seat. The two seats allow the downcomer pipe to be rotational misaligned with the coupling apparatus. The coupling bolts extend through the mating flange and the housing to rigidly secure the downcomer pipe to the coupling apparatus.

Abstract: A gravity driven suction pump for a nuclear reactor condenser is described. The gravity driven suction pump is utilizes the potential energy of the condenser condensate to move condensible and noncondensible gases through the condenser. The gravity driven suction pump includes a drain line having a venturi section and a suction line extending from the condenser into the venturi section. The venturi section alters the flow velocity of condensate in the throat of the drain line and creates a pressure differential through the suction line to drain the noncondensible gases from the condenser.

Abstract: Modified passive containment cooling systems for cooling a reactor core of a boiling water nuclear reactor are described. The passive containment cooling system (PCCS), in one form, includes a vent line coupled to the vacuum breaker. The vent line includes a first end, a second end, and a passage extending between the first and second ends for transporting noncondensibles between the first and second ends. The first end is coupled to PCCS condenser, and the second end is submerged in a suppression pool. A branch extends from an intermediate portion of the vent line and is coupled to the vacuum breaker. The branch includes a first end, a second end, and a passage extending between the first and second ends. The first end of the branch is coupled to the intermediate portion of the vent line so that the branch passage is in communication with the vent line passage.