An improved retention and alignment system for nuclear fuel rods includes an upper nozzle plate and a lower nozzle plate, nuclear fuel rods, each having an upper end and a lower end and extending axially between the upper and lower nozzle plates, a first precision magnet incorporated onto the lower end of the fuel rod, and a plurality of second precision magnets incorporated onto the lower nozzle plate in positions confronting the first precision magnets on the fuel rods. Each first precision magnet has at least one of a magnetic north or south polarity and the second precision magnet has at least one of a magnetic south or north polarity opposite the polarity of the confronting first precision magnet to effect magnetic attraction between the confronting first and second precision magnets. Grids between the upper and lower nozzle plates form cells through which the fuel rods pass. Precision magnets of the same polarity may be positioned laterally along the fuel rods and grid walls in positions confronting each other to repel the fuel rods from the grid walls to maintain fuel rod alignment and prevent contact between the fuel rods and the grids.

A nuclear reactor is designed to couple the load path of the control elements with the reactor core, thus reducing the opportunity for differential movement between the control elements and the reactor core. A cartridge core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The cartridge core barrel can be mounted to a reactor vessel head, and any movement, such as through seismic forces, transmits an equal direction and magnitude to the control elements and the reactor core, thus inhibiting the opportunity for differential movement.

An insertable flux thimble interface for use in a bottom nozzle of a fuel assembly in a nuclear reactor (i.e., a bottom nozzle insert) is disclosed herein. In various aspects, the bottom nozzle insert has properties that are different from traditional bottom nozzle flux thimble interfaces. The properties of the bottom nozzle insert may mitigate wear phenomena observed on the flux thimble. For example, the bottom nozzle insert may be constructed from material that is different from the material of the bottom nozzle. In some aspects, the bottom nozzle insert is constructed from material that has a hardness that is less than the hardness the bottom nozzle material. In other aspects, the bottom nozzle insert is constructed from a material that has a hardness that is less than the hardness of the flux thimble material.

A nuclear fuel assembly having a bottom nozzle with protrusions that extend from the upstream (lower or fluid entry) and downstream (upper or fluid exit) side of a horizontally supported perforated flow plate. The protrusions have a funnel-like shape that gradually decreases the lateral flow area on the upstream side of the perforated flow plate and gradually increases the lateral flow area on the downstream side of the perforated plate. The protrusions on the downstream side are preferably recessed to accommodate the ends of the fuel rods.

It is possible to achieve self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during a reactor operation. According to the present invention, the lower portion of the lower tie plate 7 as a part of the fuel assembly 3, which is inserted into the fuel support 9, extends, and a stable member 21 is provided around the extension portion 20, and thereby it is possible to achieve the self-support of the fuel assembly without the upper grid plate. In addition, since an increase in a weight due to extension of the lower portion of the lower tie plate 7 can prevent the floating during the reactor operation, a floating preventing mechanism using the upper grid plate is not necessary. Hence, it is possible to achieve the self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during the reactor operation.

It is possible to achieve self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during a reactor operation. According to the present invention, the lower portion of the lower tie plate 7 as a part of the fuel assembly 3, which is inserted into the fuel support 9, extends, and a stable member 21 is provided around the extension portion 20, and thereby it is possible to achieve the self-support of the fuel assembly without the upper grid plate. In addition, since an increase in a weight due to extension of the lower portion of the lower tie plate 7 can prevent the floating during the reactor operation, a floating preventing mechanism using the upper grid plate is not necessary. Hence, it is possible to achieve the self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during the reactor operation.

A fuel assembly for a boiling water reactor, having fuel rods, a tie plate, a handle device, and at least two water rods attached to the tie plate and to the handle device. A plurality of spacers, define first passages for some of the fuel rods, and second passages for the water rods. Each water rod comprises a tube part attached to the tie plate, and a solid part attached to the handle device. The tube part permits a flow of coolant. The spacers include primary spacers and a secondary spacer. The primary spacers are attached to the tube parts. The tie plate, the water rods, the primary spacers and the handle device form a support structure carrying the weight of the fuel rods. The secondary spacer is positioned at the solid part of the respective water rod.

A curvilinear electromagnetic pump is configured to follow a curve, such as by coupling multiple linear pump segments together that are offset by an angle with respect to each other. The curvilinear electromagnetic pump can curve within two dimensions, or within three dimensions. The curvilinear electromagnetic pump allows for more efficient arrangement of components and systems within a nuclear reactor vessel and allows a significantly reduced reactor vessel height as compared to a linear pump arranged vertically. The curvilinear electromagnetic pump may follow the curvature of the reactor vessel wall and may be entirely disposed near the bottom of the reactor vessel.

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.

A spring apparatus in accordance with the disclosed and claimed concept is usable in a nuclear installation. In one embodiment, the spring apparatus includes a plurality of springs that are in a compressed state and that are compressively engaged with an upper core plate of a nuclear reactor when the reactor is in a cold condition. However, when the reactor is in a hot condition, a spring of the plurality of springs is in a free state wherein a free end of the spring is in an uncompressed state and is disengaged from the upper core plate. In another embodiment, the spring apparatus employs a support apparatus that is also in accordance with the disclosed and claimed concept and that includes one or more bumpers that engage the springs of a spring pack from the underside.