Abstract: A liquid fluoride salt cooled, high temperature reactor having a reactor vessel with a pebble-bed reactor core. The reactor core comprises a pebble injection inlet located at a bottom end of the reactor core and a pebble defueling outlet located at a top end of the reactor core, an inner reflector, outer reflector, and an annular pebble-bed region disposed in between the inner reflector and outer reflector. The annular pebble-bed region comprises an annular channel configured for receiving pebble fuel at the pebble injection inlet, the pebble fuel comprising a combination of seed and blanket pebbles having a density lower than the coolant such that the pebbles have positive buoyancy and migrate upward in said annular pebble-bed region toward the defueling outlet. The annular pebble-bed region comprises alternating radial layers of seed pebbles and blanket pebbles.

Abstract: A dimensional reactivity management system that takes into account the axial burnup shape data of a nuclear fuel assembly to determine the acceptability of placement of the assembly relative to other assemblies in a storage container.

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: The nuclear fuel assembly means a group of nuclear fuel rods disposed in a substantially regular array together with a support skeleton (5), the assembly having: two nozzles; guide tubes interconnecting the nozzles; and spacer grids secured to the guide tubes for holding the rods. The assembly includes at least one support skeleton reinforcing device disposed between two successive spacer grids and secured to guide tubes. The reinforcing device is disposed inside the group of rods and presents a transverse extent that is smaller than the transverse extent of the array of nuclear fuel rods.

Abstract: A method for controlling a nuclear reactor is disclosed. The method includes providing a moderator zone in a core of the nuclear reactor, providing a fuel in the moderator zone, and providing one or more housings, each having a cavity, adjacent to the fuel. The method also includes allowing movement of a moderator between the moderator zone and the cavity of the one or more housings at a lower portion of the one or more housings. The method further includes confining moderator in the cavity of the one or more housings at an upper portion of the one or more housings.

Abstract: A pressurized water reactor nuclear containment radiation shield which surrounds the upper portion of a pressure vessel in an ice condenser containment. The vertical walls of the neutron shield are formed in vertical sections with the lower and upper sections operable during outages, to open to promote air flow cooling along the walls in the vicinity of the vessel head.

Abstract: A method for carrying out a reactor internal, comprising steps of: forming a first opening portion in a ceiling of a reactor building at a position directly above an equipment pool in said reactor building; cutting a cylindrical reactor internal surrounding a core in a reactor pressure vessel disposed in said reactor building, at one position in an axial direction; surrounding said cut cylindrical reactor internal with a radiation shield; and carrying out said cylindrical reactor internal surrounded by said radiation shield out of said reactor building through said first opening portion.

Abstract: Provided is a fuel assembly 1 for a PWR nuclear reactor capable of stably creating transverse flows of coolant for pressing and securing control rods so as to restrain vibration of the control rods in order to restrain the outer surfaces of the control rods and the inner surfaces of control rod guide tubes from being worn, wherein an upper nozzle arranged above the fuel assembly comprises an adapter plate 6 constituting the lower structure of the upper nozzle, a side wall extended along the periphery of the adapter plate, an overhang projected into a space above the adapter plate from the upper part of the side wall, and apertures for attaching control guide tubes and passage holes, which are formed in the passage surface of the adapter plate, and wherein those 15A, 15B, 15C of the passage holes which are located at positions where the coolant impinges upon the overhang are generally arranged, line-symmetric with respect to diagonal lines of the passage surface serving as symmetric axes Q, and ligaments 21, 2

Abstract: The reactor vessel of a nuclear reactor installation which is suspended from the cold leg nozzles in a reactor cavity is provided with a lower thermal insulating barrier spaced from the reactor vessel that has a hemispherical lower section that increases in volume from the center line of the reactor to the outer extent of the diameter of the thermal insulating barrier and smoothly transitions up the side walls of the vessel. The space between the thermal insulating harrier and the reactor vessel forms a chamber which can be flooded with cooling water through passive valving to directly cool the reactor vessel in the event of a severe accident. The passive inlet valve for the cooling water includes a buoyant door that is normally maintained sealed under its own weight and floats open when the cavity is Hooded. Passively opening steam vents are also provided.

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: A nuclear fission reactor, flow control assembly, methods therefor and a flow control assembly system. The flow control assembly is coupled to a nuclear fission module capable of producing a traveling burn wave at a location relative to the nuclear fission module. The flow control assembly controls flow of a fluid in response to the location relative to the nuclear fission module. The flow control assembly comprises a flow regulator subassembly configured to be operated according to an operating parameter associated with the nuclear fission module. In addition, the flow regulator subassembly is reconfigurable according to a predetermined input to the flow regulator subassembly. Moreover, the flow control assembly comprises a carriage subassembly coupled to the flow regulator subassembly for adjusting the flow regulator subassembly to vary fluid flow into the nuclear fission module.

Abstract: A fuel assembly for a pressurized water nuclear reactor contains a multiplicity of fuel rods which are guided in a plurality of axially spaced spacers which in each case form a square grid, composed of grid webs, with a multiplicity of cells arranged in rows and columns. In each case one control rod guide tube is guided through a number of these cells. At least one spacer is configured to be mechanically stronger in a first partial region than in a second partial region. In this second partial region, the spacer is provided with at least one resisting element which protrudes into a flow sub-channel formed between the fuel rods and increases the flow resistance. The resisting element counteracts a reduction associated with the mechanically weaker configuration, in the flow resistance in the second partial region and in this manner effects a homogenization of the hydraulic behavior of a spacer which is mechanically inhomogeneous on account of the varying mechanical configuration.

Abstract: A jet pump diffuser weld repair device includes a lower ring section and an upper ring section respectively sized to fit around a circumference of the diffuser on opposite sides of the weld to be repaired. The lower and upper ring sections are provided with a plurality of aligned gripper slots. A corresponding plurality of grippers are fit into the gripper slots, where at least one of the gripper slots and the grippers defines cam surfaces shaped to drive the grippers radially inward as lower and upper ring sections are drawn toward each other. A plurality of connector bolts are secured between the lower ring section and the upper ring section. Tightening of the connector bolts draws the lower and upper ring sections toward each other.

Abstract: The present invention is directed to a cooling system for removing heat from a Fischer-Tropsch (F-T) slurry reactor. The cooling system including at least one downcomer having an upper portion, a lower portion, and a diameter; the at least one downcomer disposed within the F-T reactor to deliver a coolant downward through the F-T reactor at a predetermined velocity, the at least one downcomer extending a length within the F-T reactor wherein the coolant is introduced into the upper portion of the at least one downcomer in a substantially liquid phase; the diameter of the at least one downcomer and the pressure of the introduced coolant cooperate to increase the coolant velocity thereby generating backpressure in the at least one downcomer to maintain the coolant in the substantially liquid phase along the length of the at least one downcomer.

Abstract: The invention provides at least two electrochemical sensors positioned in a nuclear reactor or in a system adjacent to the nuclear reactor, wherein at least one of the at least two electrochemical sensors has a heated zirconium electrode, and the at least two electrochemical sensors produce voltages proportional to an electrochemical corrosion potential for a surface that each of the at least two electrochemical sensors are installed upon. The invention also provides an arrangement configured to accept the voltages produced by the at least two electrochemical sensors, wherein the arrangement is configured to determine an electrochemical corrosion potential of a zirconium fuel rod in the nuclear reactor based upon the voltages of the at least two electrochemical sensors.

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 method for attaching a core spray sparger T-box clamp for a sparger T-box in a shroud of a nuclear reactor pressure vessel assembling the anchor plate, bearing plate and saddle bracket; positioning the assembly of the anchor plate, bearing plate and saddle bracket in front of the T-box such that the saddle bracket is below a sidewall of the T-box; elevating the assembly to seat the saddle bracket against a lower surface of the sidewall and sliding a locating pin on the saddle bracket into an aperture in the sidewall; lowering a carrier plate onto an upper surface of the sidewall and attaching the carrier plate to the anchor plate, wherein a locating pin on the carrier plate slides into an aperture on the upper surface, and advancing the bearing plate to the T-box to bias a bearing plate against a cover plate of the T-box.

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: A control rod includes a tie-rod, a handle mounted to an upper end portion of the tie-rod, either a connector plate or a fall velocity limiter mounted to a lower end portion of the tie-rod, sheaths having a U-shaped cross-section, welded intermittently to the tie-rod at a plurality of locations in the axial direction of the tie-rod, and having an upper end welded to the handle and a lower end welded to either the connector plate or the fall velocity limiter, and a neutron absorbing member disposed inside each of the sheaths. An upper end of a weld portion located at uppermost position in an axial direction of the tie-rod among a plurality of weld portions between the tie-rod and the sheath is disposed at a position within a range between 0.8 and 13% of total axial length Ls of the sheath below an upper end of the sheath.

Abstract: An embodiment of the present invention may reduce the level of vibration experienced by a line, such as, but not limiting of, a pipe, a cable, tubing, or the like, that is connected to at least one separate structure. For example, but not limiting of, the structure includes: a reactor pressure vessel, a sparger pipe, steam generator, a pipe, a pressure vessel, a heat exchanger, a pump, a condenser, a tank, or the like. An embodiment of the present invention may provide support and a preload to the line at a new location or may replace an existing support, such as, but not limiting of, a weld; which may alter the natural frequencies to avoid resonance from occurring when the structure(s) is excited.