Abstract: An exemplary embodiment can include an apparatus including: an internal-external hybrid nuclear reactor, which can include: at least one reciprocating internal engine; and at least one external reactor integrated with said at least one reciprocating internal engine. The reciprocating engine can receive nanofuel (including moderator, nanoscale molecular dimensions & molecular mixture) internally in an internal combustion engine that releases nuclear energy. A method of operating the hybrid nuclear reactor can include operating the reciprocating internal engine loaded with nanofuel in spark or compression ignition mode. A method of cycling the reciprocating internal engine, can include compressing nanofuel; igniting nanofuel; capturing energy released in nanofuel, which is also the working fluid; and using the working fluid to perform mechanical work or generate heat.

Abstract: A reinforcement assembly may be provided for a bracket configured to constrain a cooling pipe of a spent fuel pool of a nuclear reactor. The reinforcement assembly includes a base structure defining back slots, angled slots, side slots, and/or front slots. Back boss structures may be configured to slidably engage with the back slots of the base structure. Pipe boss structures may be configured to slidably engage with the angled slots of the base structure. Side clamps may be configured to slidably engage with the side slots of the base structure. Each of the side clamps may define a vertical slot. Vertical clamps may be configured to slidably engage with the vertical slot of each of the side clamps. Front clamps may be configured to slidably engage with the front slots of the base structure.

Abstract: Exemplary embodiments provide automated nuclear fission reactors and methods for their operation. Exemplary embodiments and aspects include, without limitation, re-use of nuclear fission fuel, alternate fuels and fuel geometries, modular fuel cores, fast fluid cooling, variable burn-up, programmable nuclear thermostats, fast flux irradiation, temperature-driven surface area/volume ratio neutron absorption, low coolant temperature cores, refueling, and the like.

Abstract: The sodium-resistant joining glass (1) is substantially free of ZrO2 and is based on a SiO2—B2O3—Na2O—Al2O3 glass system. It is suitable for producing a joint of a metal and/or ceramic component with a further joining component (2, 3, 4) using the joining glass (1). Feedthrough-devices (20) using the joining glass (1) as fixing material are also disclosed.

Abstract: A high-temperature containment-isolation system for transferring heat from a nuclear reactor containment to a high-pressure heat exchanger is presented. The system uses a high-temperature, low-volatility liquid coolant such as a molten salt or a liquid metal, where the coolant flow path provides liquid free surfaces a short distance from the containment penetrations for the reactor hot-leg and the cold-leg, where these liquid free surfaces have a cover gas maintained at a nearly constant pressure and thus prevent high-pressures from being transmitted into the reactor containment, and where the reactor vessel is suspended within a reactor cavity with a plurality of refractory insulator blocks disposed between an actively cooled inner cavity liner and the reactor vessel.

Abstract: To provide a molten salt reactor that enables heat in the molten salt reactor to be extracted without bringing metal piping for heat exchange into direct contact with a molten salt. A molten salt reactor is provided with: a moderator structure 3 which has at least one molten salt flow path 2 vertically passing therethrough, a reflector 4 which is disposed above, below and around the moderator structure with a molten salt circulation gap X therebetween, a reactor vessel 5 which houses the reflector 4, and a coolant flow path 10A through which a coolant that exchanges heat with the interior of the reactor vessel 5 through a wall of the reactor vessel 5 flows.

Abstract: The invention relates to a reactor for consuming a nuclear fuel that contains atoms of elements having a low atomic number (Z) and a low mass number (A), wherein the nuclear reactor (1) comprises a vessel (2) containing a reaction chamber (3). This reaction chamber (3) is topped and sealed by a sealed container (4), and contains the nuclear fuel, which comprises a colloidal mixture capable of producing Ultra Low Momentum Neutrons (ULMNs) by using electromagnetic radiations (5).

Abstract: A U-tube steam generator having a dual system for collecting loose parts and sludge. A loose parts collector having a water overflow edge is disposed between a feedwater inlet and a tube bundle of the steam generator. A sludge collector having a water outlet that is disposed downstream of the overflow edge of the loose parts collector and maintains a pressure differential between a water inlet of the sludge collector and the water outlet.

Abstract: An embodiment of the present invention takes the form of a system that may reduce the level of flow-induced vibration (FIV) experienced by a jet pump assembly or other similar object within a pressure vessel. Essentially, an embodiment of the present invention may reduce the slip-joint leakage, which may be a cause of the FIVs, by adding a flow-limiting component to an outlet of the slip joint. This component may take the form of a collar, channel, and/or other component that may be connectable to a component of the jet pump assembly. After installation, an embodiment of the present invention may lower the amplitude of, and/or change the frequency of, the FIVs experienced by the jet pump assembly.

Abstract: The present invention provides a drain plug assembly that prevents significant quantities of corium from entering the drain line. By protecting the drain line, essentially no high-activity fission products would be released to the reactor building or the environment during a severe accident. The ceramic drain plug assembly includes a drain plug base and a drain plug supported by a steel pedestal. The lower surface of the plug has a spherical shape such that the plug can be positioned within the base to block access to the drain opening provided in a central portion of the base. During normal operation conditions, the plug is retained above the base by the pedestal. During a severe accident, when corium comes into contact with the pedestal, it will melt rapidly and the drain plug will drop by gravity, effectively closing the sump drain opening and preventing the flow of corium into the drain line.

Abstract: A nozzle apparatus of a jet pump includes a nozzle base member, and a plurality of nozzles installed to the nozzle base member and forming a plurality of narrowing portions, in which a fluid passage cross-sectional area of a driving fluid passage formed in the nozzle is reduced.

Abstract: A jet pump which can restrain self-excited vibration in a connection portion between an inlet mixer pipe and a diffuser pipe without inhibiting a structural deformation due to thermal expansion and the like includes a slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween; and a self vibration damping structure configured such that when the clearance defined by an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe is widening or narrowing due to vibration of the inlet mixer pipe or the diffuser pipe, a flow path resistance inside a clearance flow path for pumped coolant water defined by the clearance is not smaller than a fluid inertia force all over the clearance flow path.

Abstract: Zirconium-based metal alloy compositions comprise zirconium, a first additive in which the permeability of hydrogen decreases with increasing temperatures at least over a temperature range extending from 350° C. to 750° C., and a second additive having a solubility in zirconium over the temperature range extending from 350° C. to 750° C. At least one of a solubility of the first additive in the second additive over the temperature range extending from 350° C. to 750° C. and a solubility of the second additive in the first additive over the temperature range extending from 350° C. to 750° C. is higher than the solubility of the second additive in zirconium over the temperature range extending from 350° C. to 750° C. Nuclear fuel rods include a cladding material comprising such metal alloy compositions, and nuclear reactors include such fuel rods. Methods are used to fabricate such zirconium-based metal alloy compositions.

Abstract: The present invention relates to a nuclear reactor, in particular a pool-type nuclear reactor cooled with liquid metal (for example, a heavy metal such as lead or lead-bismuth eutectic) or with sodium or molten salts, having a core formed by a bundle of fuel elements and immersed in a primary fluid circulating between the core and at least one heat exchanger; the fuel elements extend along respective parallel longitudinal axes and have respective bottom active parts immersed in the primary fluid to constitute the core, and respective service parts that extend at the top from the active parts and emerge from the primary fluid; the fuel elements are mechanically supported via respective top end heads anchored to supporting structures and can be operated via handling machines.

Abstract: According to an embodiment, a pressurized water reactor plant has a primary system which includes: a reactor vessel for housing a reactor core which is cooled by a primary coolant, a single steam generator, a hot leg pipe for connecting the reactor vessel and the steam generator, cold leg pipes, at least two primary coolant pumps, and a pressurizer for pressurizing the primary coolant pressure boundary in which the primary coolant flows. The plant also has: a passive cooling and depressurization system which is a primary depressurization means for equalizing the primary system pressure to the secondary system pressure at the time of a tube rupture accident of the steam generator, and a reactor containment vessel containing the primary system and cooling the primary system by air cooling. Thus, a compact pressurized water rector with high economic efficiency, safety, and reliability can be provided.

Abstract: A spacer grid includes intersecting straps defining cells with springs and dimples arranged to hold fuel rods passing through the cells. The springs are dual cantilevered springs with a bridge section between the distal end of the spring and the base. The distal portion of the spring is less stiff than the bridge section. The bridge section creates a bump which acts as a stop or travel limiter to prevent loss of grip force due to excessive spring deflection.

Abstract: A nuclear power plant is provided including a BWR, a reactor cooling system cooling the BWR, an HWC hydrogen injection system connected to the reactor cooling system and an alcohol injection system connected to the reactor cooling system. Methods for providing methanol and hydrogen are also provided.

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: Nuclear reactor systems and methods are described having many unique features tailored to address the special conditions and needs of emerging markets. The fast neutron spectrum nuclear reactor system may include a reactor having a reactor tank. A reactor core may be located within the reactor tank. The reactor core may include a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium. A pump may circulate the liquid sodium through a heat exchanger. The system may include a balance of plant with no nuclear safety function. The reactor may be modular, and may produce approximately 100 MWe.

Abstract: A power module includes a reactor vessel containing a coolant and a reactor core located near a bottom end of the reactor vessel. A riser section is located above the reactor core, wherein the coolant circulates past the reactor core and up through the riser section. In one embodiment, a coolant deflector shield includes flow-optimized surfaces, wherein the flow-optimized surfaces direct the coolant towards the bottom end of the reactor vessel. In another embodiment, the reactor housing includes an inward facing portion that varies a flow pressure of the coolant and promotes a circulation of the coolant past a baffle assembly and towards the bottom end of the reactor vessel.

Abstract: A high-temperature nuclear reactor, cooled by a liquid fluoride salt, is described. The reactor uses an annular fuel pebble comprised of an inert graphite center kernel, a TRISO fuel particles region, and a graphite outer shell, with an average pebble density lower than the density of the liquid salt so the pebbles float. The pebbles are introduced into a coolant entering the reactor and are carried into the bottom of the reactor core, where they form a pebble bed inside a plurality of vertical channels inside one or more replaceable Pebble Channel Assemblies (PCAs). Pebbles are removed through defueling chutes located at the top of each PCA. Each PCA also includes channels for insertion of neutron control and shutdown elements, and channels for insertion of core flux mapping and other instrumentation.

Abstract: This invention relates to a method of preparing nuclear fuel including the step of depositing at least two adjacent series of layers (16, 18) around a kernel (12) of fissile material, each series comprising a layer of pyrolytic carbon (16) contiguous with a layer of silicon carbide (18) and each layer (16, 18) having a thickness of at most (10) micrometers, such that alternate layers of (16, 18) of pyrolytic carbon and silicon carbide are deposited around the kernel (12). The invention extends to a nuclear fuel element (10).

Abstract: A method of storing heat includes moving a portion of a heated fluid from at least one reactor core to at least one tank having solid media, storing heat from the portion of the heated fluid in the solid media, and transferring the stored heat from the solid media to a fluid that can be used by a power plant to generate electrical energy. A system for storing heat in a nuclear power plant includes at least one tank comprising solid media structured and arranged to store heat and an arrangement structured and arranged to pass a first fluid through the at least one tank, transfer heat from the first fluid to the solid media, store the heat in the solid media, and transfer the heat from the solid media to a second fluid. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.

Abstract: A jet pump has a plurality of nozzles installed to a nozzle base, a throat and a diffuser. A first nozzle straight-tube portion, a first nozzle narrowing portion, a second nozzle straight-tube portion, a second nozzle narrowing portion, and a nozzle lower end portion formed in those nozzles are disposed in this order from the nozzle base to a ejection outlet. A narrowing angle of the second nozzle narrowing portion is larger than of the first nozzle narrowing portion. The jet pump forms, in a lower end portion of the throat, a flow passage narrowing portion having a flow passage cross-sectional area that gradually diminishes. This flow passage narrowing portion is inserted into an upper end portion of the diffuser.

Abstract: In a cooling structure and a cooling method for a control rod drive mechanism and in a nuclear reactor, a housing (59) in which magnetic jacks are housed is fixed to an upper portion of a reactor vessel (41), and an air intake unit (102) that takes cooling air into the housing (59), a first exhaust duct (104) that is arranged side by side with the air intake unit (102) in a circumferential direction of the housing (59), into which cooling air in the housing (59) is suctioned through a first inlet (109) at a lower portion thereof, and that guides the cooling air upward, a second exhaust duct (105) that is disposed below the air intake unit (102), into which cooling air in the housing (59) is suctioned through a second inlet (110), and that guides the cooling air to the first exhaust duct (104), and a discharging unit (111) that is formed at an upper portion of the housing (59) and discharges cooling air in the first exhaust duct (104) to the exterior are provided.

Abstract: The geometric dimensions and shape of a device for removing solid particles from the cooling medium that is circulated in the primary circuit of a nuclear reactor, in particular a boiling water nuclear reactor, are such that the device can be inserted in lieu of a fuel element or fuel assembly into an empty fuel element or assembly position of the reactor core of the nuclear reactor.

Abstract: Hard stops are useable in an operating nuclear reactor to separate and bias restrainer brackets and inlet mixers. Hard stops include a lip clamp that clamps to a restrainer bracket and a wedge member that biases against the inlet mixer. The wedge member and lip clamp are engaged such that the two components can slide against one another to bias the restrainer bracket and inlet mixer. The lip clamp includes a clamp arm and an engagement member to clamp opposite sides of the restrainer bracket. Ratchet assemblies maintain selective positioning various components of the hard stops. Hard stops may be used in several different numbers, positions, and configurations in repair or modification systems. Hard stops may be installed by determining location on an outside of a restrainer bracket for the hard stop, securing the hard stop at the location, and biasing the hard stop between two components at the location.

Abstract: A power module assembly includes a reactor core immersed in a coolant and a reactor vessel housing the coolant and the reactor core. An internal dry containment vessel submerged in liquid substantially surrounds the reactor vessel in a gaseous environment. During an over-pressurization event the reactor vessel is configured to release the coolant into the containment vessel and remove a decay heat of the reactor core through condensation of the coolant on an inner surface of the containment vessel.

Abstract: A pressurized water reactor (PWR) includes a pressure vessel and a nuclear reactor core disposed in the pressure vessel. A baffle plate is disposed in the pressure vessel and separates the pressure vessel into an internal pressurizer volume disposed above the baffle plate and an operational PWR volume disposed below the baffle plate. The baffle plate comprises first and second spaced apart plates and includes a pressure transfer passage having a lower end in fluid communication with the operational PWR volume and an upper end in fluid communication with the internal pressurizer volume at a level below an operational pressurizer liquid level range. A vent pipe has a lower end in fluid communication with the operational PWR volume and an upper end in fluid communication with the internal pressurizer volume at a level above the operational pressurizer liquid level range.

Abstract: Example embodiments relate to a method and apparatus for reducing electrostatic deposition of charged particles on wetted surfaces that are exposed, periodically or substantially continuously, to high velocity fluid flow within a coolant flow path in a nuclear reactor. The method may include depositing a first or base dielectric layer and a second or outer dielectric layer on a conductive surface that forms a portion of a high velocity flow path to attain the apparatus. The first dielectric layer material is selected to provide improved adhesion and insulation to the conductive surface and the second dielectric layer material is selected to provide suitable adhesion to the first dielectric layer and improved corrosion and/or mechanical resistance in the anticipated operating environment.

Abstract: A natural-circulation type boiling water reactor includes a plurality of divided chimneys provided above a reactor core and a number of fuel assemblies are charged in the reactor core. The natural-circulation type boiling water reactor is provided with a pressure equalization structure arranged on rectangular-columnar lattice plates of the divided chimneys for equalizing pressures in divided chimney portions so as to equalize the pressures of the divided chimneys with the pressure equalization structure.

Abstract: The repairing method includes removing a connection portion with respect to an in-core instrument tube in a groove-welding portion, removing the in-core instrument tube from a lower mirror, removing the groove-welding portion and processing a plug attachment opening, and fixing a plug to the plug attachment opening by welding.

Abstract: It is possible to improve the workability and the stress corrosion resistance by easily performing a repairing operation in a nozzle repairing method and a nuclear reactor vessel. The repairing method includes: removing a first connection portion ((trepanned portion) 208) with respect to an in-core instrument tube (204) in a groove-welding portion (206); removing the in-core instrument tube (204) from a lower mirror (66); leaving and grooving a second connection portion ((existing welding portion) 211) with respect to the lower mirror (66) in the groove-welding portion (206); inserting a new in-core instrument tube (204A) into an attachment hole (203); and groove-welding (so as to form a new groove-welding portion (213)) the inner side of the lower mirror (66) so as to fix the new in-core instrument tube (204A).

Abstract: The invention relates to an inexpensively-/easily-decommissionable nuclear power plant, where a nuclear isle of one or more nuclear power-stations is installed in caverns, and further, side by side with them, a center for characterizing, treating and conditioning radioactive wastes and two repositories are installed in suitable caverns, with a final repository being adapted to store low-intermediate level nuclear wastes and a temporary repository being adapted to store spent fuel, high-level long-life radioactive materials and, in case, spare nuclear rods for reactor refueling.

Abstract: A nuclear reactor having a liquid metal or molten salt coolant in a riser space 130?, has a cylindrical containment vessel 134 with a reactor vessel 120?, at least two lobes 121, preferably three to nine lobes 121, each lobe 121 interconnected with the other lobe(s) and each containing a fast reactor core, 116?, 116?, 116? and 116??.

Abstract: An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accommodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through which the dowel pins pass.

Abstract: The present invention relates to a longitudinally divided emergency core cooling (ECC) duct in order to efficiently inject safety water to core of a pressurized light-water nuclear reactor. The ECC duct includes side supports for preventing the flow-induced vibration in the annular downcomer, and has structural stability while thermally expanding and contracting. A longitudinally divided ECC duct for emergency core cooling water injection of a nuclear reactor is provided on the periphery of a core barrel of a nuclear reactor, includes an emergency core cooling water inlet facing a direct vessel injection nozzle, and extends in a longitudinal direction of the core barrel. The longitudinally divided ECC duct is divided into a plurality of longitudinally-divided ducts in the longitudinal direction of the longitudinally divided ECC duct.

Abstract: A debris exclusion and retention device traps and retains foreign material within the lower tie plate of the fuel assembly utilizing the existing flow paths within the lower tie plate, and without redirecting coolant flow. Flow through the inlet nozzle of the lower tie plate into an enlarged lower tie plate housing creates strong jet impingement against the center of the lower tie plate grid or debris filter, if present, which has a tendency to push debris to the periphery of the lower tie plate. Low flow zones around the periphery of the lower tie plate allow debris to fall back toward the inlet nozzle. The retention device traps and retains debris in these low flow zones without impacting existing flow patterns in the lower tie plate. Thus, the retention device has minimal or no impact on lower tie plate pressure drop.

Abstract: A boiling water reactor has a core disposed in the reactor pressure vessel and loaded with a plurality of fuel assemblies including transuranic nuclides. A ratio of Pu-239 in all of the transuranic nuclides included in the fuel assembly, which is loaded in the core, with a burnup of 0 is 3% or more but 45% or less. In the fuel assembly having a channel box and a plurality of fuel rods disposed in the channel box, a transverse cross section of a fuel pellet in the fuel rod occupies 30% or more but 55% or less of a transverse cross section of a unit fuel rod lattice in the channel box.

Abstract: A reactor vessel includes a plenum and a reactor core with first and second sets of channels. A blanket salt flows through the first set of channels, and a fuel salt flows through the second set of channels. The plenum receives the blanket salt from the first set of channels. The blanket salt provides a breed-stock for a fission reaction in the fuel salt and transfers heat generated by the fission reaction without mixing with the fuel salt.

Abstract: A nuclear reactor includes a nuclear reactor core comprising fissile material and a pressure vessel containing the nuclear reactor immersed in primary coolant water at an operating pressure. The pressure vessel has a vessel penetration passing through a wall of the pressure vessel. An electrical feedthrough seals the vessel penetration and has an outside electrical connector mounted at the pressure vessel. The outside electrical connector is at atmospheric pressure. The electrical feedthrough may include a flange disposed inside the pressure vessel and sealing against an inside surface of the wall of the pressure vessel. The outside electrical connector of the electrical feedthrough may be inset into the wall of the pressure vessel.

Abstract: A riser cone has a lower end sized to engage a cylindrical lower riser section of a nuclear reactor and an upper end sized to engage a cylindrical upper riser section of the nuclear reactor. The riser cone defines a compression sealing ring that is compressed between the lower riser section and the upper riser section in the assembled nuclear reactor. In some embodiments the riser cone comprises: a lower element defining the lower end of the riser cone; an upper element defining the upper end of the riser cone; and a compliance spring compressed between the lower element and the upper element. In some embodiments the riser cone comprises a frustoconical compression sealing ring accommodating a reduced diameter of the upper riser section as compared with the diameter of the lower riser section.

Abstract: A fixed cluster for the core of pressurized-water nuclear reactor including rods and a holder for rods. The holder includes: an upper head; fins extending radially towards the outside from the upper head; systems for mounting the rods and distributed on the fins; and at least two abutment elements on the upper plate of the core, each of the abutment elements protruding longitudinally from a respective fin beyond the mounting systems so as to be vertically oriented towards the top when the fixed cluster is provided on a nuclear fuel assembly.

Abstract: A core of a light water reactor having a plurality of fuel assemblies, which are loaded in said core, having nuclear fuel material containing a plurality of isotopes of transuranium nuclides, an upper blanket zone, a lower blanket zone, and a fissile zone, in which the transuranium nuclides are contained, disposed between the upper blanket zone and the lower blanket zone, wherein a ratio of Pu-239 in all the transuranium nuclides contained in the loaded fuel assembly is in a range of 40 to 60% when burnup of the fuel assembly is 0, sum of a height of the lower blanket zone and a height of the upper blanket zone is in a range of 250 to 600 mm, and the height of said lower blanket zone is in a range of 1.6 to 12 times the height of the upper blanket zone.

Abstract: A dynamic port that extends from the bottom wall of an oil reservoir that surrounds the lower guide bearing of a reactor coolant pump and is in fluid communication within an oil level gauge. The dynamic port is rotatable into and out of the oil flow path to adjust the dynamic oil level shown by the oil level gauge when the pump is at operating speed to be substantially equal to the static oil level when the motor is at rest.

Abstract: Example embodiments are directed to upper tie plates for debris mitigation and fuel bundles that use the upper tie plates. Example embodiment tie plates may include a plurality of debris capture elements that overlap each other so as to create debris traps for particulate debris that would fall onto the fuel bundle. Example embodiment fuel bundles may use the upper tie plates for debris mitigation.

Abstract: A jet pump sensing line support clamp may be used for sensing line repair, replacement, and damage prevention or reduction. The clamp may affix to jet pump sensing line supports and confine the individual jet pump sensing lines. The clamp may provide for further access or securing of the lines in the support through the clamp. Methods of installing the clamp may include attaching and tightening the clamp against the sensing lines.

Abstract: A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.

Abstract: A hold-down spring unit for a top nozzle of a nuclear fuel assembly. The hold-down spring unit is coupled to the upper end of the top nozzle of the nuclear fuel assembly. The hold-down spring unit includes a first spring which provides a hold-down force upon the nuclear fuel assembly under start-up conditions or hot full power conditions of a nuclear reactor, and a second spring which provides an additional hold-down force upon the nuclear fuel assembly under start-up conditions of the nuclear reactor. The hold-down margin under start-up conditions or hot full power conditions is reduced, thus enhancing the mechanical and structural stability of the nuclear fuel assembly.

Abstract: A nuclear reactor module includes a reactor core and a reactor housing that surrounds the reactor core about its sides, wherein the reactor housing is configured to direct coolant through the reactor core. A neutron reflector is located between the reactor core and the reactor housing, wherein the neutron reflector has a plurality of inlet ports facing the reactor core. The neutron reflector also has a plurality of outlet ports fluidly connected to the inlet ports to direct a portion of the coolant through the neutron reflector.