A method of handling spent nuclear fuel assemblies immerses the spent nuclear fuel assemblies in water in a relatively short time period when compared to traditional methods. A spent nuclear fuel assembly is removed from a nuclear reactor core, inserted into a sodium removal machine having a receiver, a cleaning vessel, and an elevator. A cleaning fluid is applied to the cleaning vessel and fuel assembly, and the fuel assembly is flushed with water while in the cleaning vessel. The cleaning vessel is at least partially submerged in the spent fuel pool during cleaning to provide passive heat removal. The cleaning vessel is lowered by an elevator into the spent fuel pool. The fuel assembly may then be loaded into a rack and/or a cask for long-term storage.

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 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 control rod drive replacement device is provided. The control rod drive replacement device includes a first channel for mounting on a support under a nuclear reactor pressure vessel; a first control rod drive extractor removably received in the first channel, the first control rod drive extractor including a first housing configured for receiving a first control rod drive, the first housing being movable between a horizontal orientation in which the first housing is aligned within the first channel and a vertical orientation in which the first housing is aligned for receiving the first control rod drive from the nuclear reactor pressure vessel; a second channel connected on top of the first channel under the nuclear reactor pressure vessel; and a second control rod drive extractor removably received in the second channel, the second control rod drive extractor including a second housing configured for receiving a second control rod drive, the second housing being movable between a horizontal orientation in which the second housing is aligned within the second channel and a vertical orientation in which the second housing is aligned for receiving the second control rod drive from the nuclear reactor pressure vessel.

A fuel assembly for a nuclear power boiling water reactor, including: a fuel channel defining a central fuel channel axis, fuel rods, each having a central fuel rod axis, at least 3 water channels for non-boiling water, each water channel having a central water channel axis and each water channel having a larger cross-sectional area than the cross-sectional area of (the average) fuel rod. The fuel rods comprise a first group of full length fuel rods and a second group of shorter fuel rods. The fuel assembly comprises at least 5 fuel rods which belong to said second group and which are positioned such that the central fuel rod axis of each of these at least 5 fuel rods is closer to the central fuel channel axis than any of the water channel axes of the water channels.

Proposed is a fixing device for use to handle a spent nuclear fuel assembly and a method for installing same, capable of improving structural reliability of the spent nuclear fuel assembly, the fixing device including: a housing (100) provided with a plurality of free end portions (110), stopper protrusions (120), a first male thread (131), and a female thread (132); a rod member (200) having a length longer than the housing (100), the rod member being provided at a tip end thereof with a pressurization protrusion (210) having an outer diameter larger than an inner diameter of the free end portions, and provided with a second male thread screw-assembled with the female thread (132), thereby being screw-assembled with the housing (100); and fixing members (310 and 320) to fix the housing (100) to the nuclear fuel assembly by being screw-assembled with the first male thread of the housing (100).

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 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 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.

Provided is a remotely operated manipulator which can be applied to a space which is wider on a back side than at an opening part, which has a simple structure, high stiffness, and high reliability. The remotely operated manipulator of the present invention includes: a circular base fixed to a wall surface; a beam which rotates on the circular base; a trolley which moves on the beam; and a mast which is raised and lowered with respect to the trolley and is mounted with a tool unit at a tip. Stiffness is improved by directly fixing the beam to the wall surface by a beam fixing device. Further, a work region is expanded by mounting a bending mast on the tip of the mast.