Abstract: Systems and methods for providing and using molten salt reactors are described. While the systems can include any suitable component, in some cases, they include a graphite reactor core defining an internal space that houses one or more fuel wedges, where each wedge defines one or more fuel channels that extend from a first end to a second end of the wedge. In some cases, one or more of the fuel wedges comprise multiple wedge sections that are coupled together end to end and/or in any other suitable manner. In some cases, one or more alignment pins also extend between two sections of a fuel wedge to align the sections. In some cases, one or more seals are also disposed between two sections of a fuel wedge. Thus, in some cases, the reactor core can be relatively long (e.g., to be a pipeline reactor). Other implementations are also described.

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: 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: 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: 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 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: 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 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 method and apparatus for a deposition solution injector for a nuclear reactor that may inject an ambient temperature deposition solution into a high temperature, high pressure feed-water flow line. The method and the apparatus ensures that the deposition solution is delivered in a location within the feed-water that is beyond a boundary layer of flowing water, to prevent smearing of the solution and prevent clogging of the deposition solution within the injector. The axial cross-sectional profile of the injector, and the location of an injection slot on the injector, may reduce vortex eddy flow of the feed-water into the injector to further reduce injector blockage.

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.

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 nuclear reactor can include a pressure vessel for containing a pressurized moderator at a first pressure. The nuclear reactor can also include a plurality of fuel channels for a coolant fluid at a second pressure. The plurality of fuel channels are fluidly connected at inlet ends thereof to a coolant supply conduit and are adapted to receive nuclear fuel bundles and to be mounted within the pressure vessel and surrounded by the moderator. The outlet ends of the fuel channels are fluidly connected to a coolant outlet conduit to enable the coolant fluid to circulate from the coolant supply conduit through the fuel channels to the coolant outlet conduit. The plurality of fuel channels maintain separation between the coolant fluid circulating within the fuel channels and the moderator.

Abstract: An embodiment of the present invention provides an apparatus and system for repairing and/or maintaining a position of a first component in relation to a second component. The first and second components may be located within a reactor pressure vessel of a nuclear powerplant. The apparatus and system may attach at least one bearing plate to a horizontal surface of the first component. The apparatus and system includes structure to apply a pre-load to the first component. This may assist in maintaining the position of the first component relative to the second component.

Abstract: A pressure-tube nuclear reactor can include an outer shell having an interior to contain a moderator at a first pressure and a coolant plenum to receive the coolant fluid at a second pressure, the second pressure being greater than the first pressure. The reactor also includes a plurality of pressure tubes. Each pressure tube is received within and extends through a corresponding shell tube and is configured to releasably retain at least one fuel bundle. A first end of each pressure tube being coupled to the plenum tubesheet in fluid communication with the plenum chamber and a second end of each pressure tube fluidly connected to a coolant conduit to enable the coolant fluid to flow between the coolant plenum and each pressure tube and to flow from the nuclear reactor for further processing.

Abstract: An embodiment of the present invention takes the form of an apparatus or system that may reduce the level of vibration experienced by an inlet riser or other similar object within a reactor pressure vessel. An embodiment of the present invention may eliminate the need for welding the riser brace to the inlet riser. An embodiment of the present invention provides at least one riser brace clamp that generally clamps the riser brace to the inlet riser. After installation, the riser brace clamp may lower the amplitude of, and/or change the frequency of, the vibration experienced by the inlet riser.

Abstract: Example embodiment clamps may be used to clamp two components together, with a degree of freedom of motion between the clamped components, including both rotational and translational motion. Example embodiment clamps may clamp a BWR jet pump sensing line to a diffuser as a repair or installation of a sensing line support. Example clamps may include a ball subassembly that holds a component and allows rotation and twisting of the component within the clamp. Example clamps may further include jaws holding the ball subassembly and a biasing element that permits tightening of the clamp.

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.

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: Method and apparatuses are provided for removing thermal energy from a nuclear reactor, which are fault tolerant. The apparatus includes at least one heat pipe configured to absorb thermal energy produced by the nuclear reactor. In addition, the apparatus includes a first compartment thermally coupled to the at least one heat pipe. The first compartment is configured to contain a first gas. Furthermore, the apparatus includes a second compartment thermally coupled to the at least one heat pipe. The second compartment is configured to contain a second gas and configured to isolate the second gas from the first gas.

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 Critical Channel Power (CCP) enhancement system is provided for a pressurized fuel-channel-type water-cooled nuclear reactor of the type adapted to be refuelled on-line by the insertion and removal of fuel bundles onto and from of a plurality of said fuel channel assemblies, each of said fuel channel assemblies. A means is provided for interlocking fuel bundles into pairs having their fuel elements aligned, thereby lowering the hydraulic resistance in the fuel channel and enhancing CCP. The means for interlocking prevents misalignment of the paired bundles during their residence time inside the reactor due to continuous rocking and vibration of the fuel bundles exposed to very high coolant mass flow rate and misalignment due to axial separation of bundles impacting upon one another during fuelling operations.

Abstract: A spacer for maintaining a pressure tube in spaced relation with a caland tube of a nuclear reactor. The spacer comprising a split ring adapted to be disposed about the outer surface of said pressure tube. The ring has a central annular body portion with a raised bearing surface thereon adapted to contact the inner surface of said calandria tube and prevent contact between said outer surface and said inner surface. An annular land projecting from each side of said central body portion is adapted to receive a collar thereon effective create an interference fit between said ring and said pressure tube and thereby constrain axial movement of said spacer on said pressure tube. The spacer of the present invention maintains its location on the pressure tube and does not suffer the axial movement which characterizes some conventional spacers. The bearing surface can have a coating to reduce wear and heat transfer.

Abstract: The present invention relates to a miniaturized nuclear utilizing improved pressure tube structural members. More particularly, the present invention relates to a new miniaturized nuclear reactor utilizing novel structural members that are used to support the loads and stresses of multiple nuclear reactor fuel channel pressure tubes and calandria tubes in a moderator.

Abstract: The present invention relates to a structural member for nuclear reactor pressure tubes. More particularly, the present invention relates to a new structural member that is used as a beam designed to support the loads and stresses of multiple transversely disposed nuclear reactor fuel channel pressure tubes.

Abstract: A nuclear reactor using gas as a primary coolant and a liquid as a moderator and/or reflector. Gas coolant flows through inlet passages around the outlet plenum to a distributor plate. The gas is directed between fuel element housing thimbles and fuel elements therein, through the fuel elements, and into the reactor outlet plenum. Fins on the thimble housings conduct heat to the gas from a liquid moderator circulating in the core. The use of a liquid moderator enhances safety, allows the fissile material and reactor mass to be reduced and eliminates problems associated with cooling of a solid moderator.

Abstract: A water cooled nuclear reactor comprises a reactor core, a primary water coolant circuit and a pressurizer arranged as an integral unit in a pressure vessel. The pressure vessel is divided into an upper chamber and a lower chamber by a casing, the reactor core and primary coolant circuit are arranged in the lower chamber and the pressuriser is arranged in the upper chamber.A plurality of pipes interconnect a steam space of the pressuriser with an upper portion of the primary coolant circuit via ports in the casing. A plurality of re-entrant surge ports interconnect a water space of the pressuriser with a lower portion of the primary coolant circuit. The surge ports have low flow resistance for water from the water space to the primary coolant circuit and high flow resistance in the opposite direction.

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: 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.

Abstract: A method for repositioning garter springs around the pressure tubes of Candu-type nuclear reactors. A primary coil having a high permeability core is inserted into the pressure tube. The coil is energized by an alternating current of a frequency and amplitude sufficient to produce a primary alternating electromagnetic field that penetrates the wall and induces an eddy current in the garter spring. A secondary alternating electromagnetic field is also produced and is reactive with the primary field to produce a travelling electromagnetic field of sufficient intensity and of such direction that the resultant of the electromagnetic forces acting on the garter spring causes the spring to move along the tube.

Abstract: The invention provides an electromagnetic technique for repositioning garter springs, located between the coolant tubes and calandria tubes of fluid cooled nuclear reactors in which the garter springs are not directly accessible by mechanical means. An electromagnetic coil is advanced along the selected fuel channel to a position adjacent the garter spring, and a current pulse is passed through the coil thereby to exert an electromagnetic repulsive force on the garter spring having a component in the direction of the required displacement.

Abstract: A pressurized water nuclear reactor comprises a reactor vessel arranged in a pool made in the form of a pressure vessel, the pool being filled with a strongly neutron-absorbing liquid, for example borated water. The reactor vessel, in addition to being connected to a primary system, is provided with a lower shutdown opening, arranged below the reactor core, for pool liquid and with an upper shutdown opening, arranged above the core, for pool liquid.