Provided herein is a small modular nuclear reactor plant that can comprise a reactor core comprising a primary sodium comprising cool primary sodium flow and heated primary sodium flow. Heated primary sodium flow can enter one or more IHXs where heated primary sodium exchanges heat with secondary sodium flowing through at least one intermediate sodium loop. Intermediate sodium loop can comprise secondary sodium flow that can transport heat to energy conversion portion via a heat exchanger. Energy conversion portion can comprise a bypass valve. Bypass valve can bypass an energy conversion working fluid (such as S-CO2) away from a turbine during periods of adjustment as discussed herein. The plant may comprise passive load following features along with the ability to provide cogeneration heat.

Nuclear fuel assemblies include non-symmetrical fuel elements with reduced lateral dimensions on their outer lateral sides that facilitate fitting the fuel assembly into the predefined envelope size and guide tube position and pattern of a conventional nuclear reactor. Nuclear fuel assemblies alternatively comprise a mixed grid pattern that positions generally similar fuel elements in a compact arrangement that facilitates fitting of the assembly into the conventional nuclear reactor.

Nuclear fuel assemblies include non-symmetrical fuel elements with reduced lateral dimensions on their outer lateral sides that facilitate fitting the fuel assembly into the predefined envelope size and guide tube position and pattern of a conventional nuclear reactor. Nuclear fuel assemblies alternatively comprise a mixed grid pattern that positions generally similar fuel elements in a compact arrangement that facilitates fitting of the assembly into the conventional nuclear reactor.

A fuel channel for a nuclear power boiling water reactor is configured to include a bundle of fuel rods with nuclear fuel. The fuel channel is made of a sheet material and has a plurality of sides which have an elongated shape and which are connected to each other such that a corner with an elongated shape is formed where two adjacent sides meet. In one or more corners, the sheet materials from the two adjacent sides overlap with each other such that there is a corner region with double sheet material consisting of the overlapping sheet material from one of the two sides and the overlapping sheet material from the other of the two sides.

A fuel channel for a nuclear power boiling water reactor is configured to include a bundle of fuel rods with nuclear fuel. The fuel channel is made of a sheet material and has a plurality of sides which have an elongated shape and which are connected to each other such that a corner with an elongated shape is formed where two adjacent sides meet. In one or more corners, the sheet materials from the two adjacent sides overlap with each other such that there is a corner region with double sheet material consisting of the overlapping sheet material from one of the two sides and the overlapping sheet material from the other of the two sides.

Disclosed embodiments include fuel ducts, fuel assemblies, methods of making fuel ducts, methods of making a fuel assembly, and methods of using a fuel assembly. In one implementation, the fuel ducts have a first hollow structure having a first cross-sectional geometry and a second hollow structure positioned within the first hollow structure, the second hollow structure having a second cross-sectional geometry different from the first cross-sectional geometry.

Disclosed embodiments include fuel ducts, fuel assemblies, methods of making fuel ducts, methods of making a fuel assembly, and methods of using a fuel assembly. In one implementation, the fuel ducts have a first hollow structure having a first cross-sectional geometry and a second hollow structure positioned within the first hollow structure, the second hollow structure having a second cross-sectional geometry different from the first cross-sectional geometry.

A transportable nuclear power system is provided. The system includes a nuclear power generator. The nuclear power generator includes one or more fuel cartridges configured to form a critical core during a power generation operation, each of the one or more fuel cartridges containing a nuclear fuel. The nuclear power generator also includes a reactivity controller and one or more working fluid conduits, each work fluid conduit containing a working fluid circulating within each of the one or more fuel cartridges to cool the nuclear fuel and execute a thermodynamic cycle. The system also includes an Intermodal transport container including a support structure mounted inside the transport container to support at least the one or more fuel cartridges of the nuclear power generator. The one or more fuel cartridges of the nuclear power generator are contained in the transport container during the power generation operation.

To effectively reduce the radioactivity concentration in reactor water. In an embodiment, a method of repairing a fuel assembly in a nuclear reactor, comprising: applying a compound containing at least one substance selected from the group consisting of TiO.sub.2, TiCl.sub.4, Ti(OH).sub.4, TiF.sub.4, TiCl.sub.3, TiN, TiC, Ti(SO.sub.4).sub.2, Ti.sub.3O.sub.5, Ti(NO.sub.3).sub.4, Al.sub.3O.sub.3, Al(OH).sub.3, AlCl.sub.3, Al(NO.sub.3).sub.3, Al.sub.2(SO.sub.4).sub.3, WO.sub.2, WO.sub.3, WC.sub.16, WF.sub.6, (NH.sub.4).sub.10W.sub.12O.sub.41.5H.sub.2O, H.sub.2WO.sub.4 and H.sub.4WO.sub.5 to a surface of a fuel rod of the fuel assembly.

To effectively reduce the radioactivity concentration in reactor water. In an embodiment, a method of repairing a fuel assembly in a nuclear reactor, comprising: applying a compound containing at least one substance selected from the group consisting of TiO.sub.2, TiCl.sub.4, Ti(OH).sub.4, TiF.sub.4, TiCl.sub.3, TiN, TiC, Ti(SO.sub.4).sub.2, Ti.sub.3O.sub.5, Ti(NO.sub.3).sub.4, Al.sub.3O.sub.3, Al(OH).sub.3, AlCl.sub.3, Al(NO.sub.3).sub.3, Al.sub.2(SO.sub.4).sub.3, WO.sub.2, WO.sub.3, WC.sub.16, WF.sub.6, (NH.sub.4).sub.10W.sub.12O.sub.41.5H.sub.2O, H.sub.2WO.sub.4 and H.sub.4WO.sub.5 to a surface of a fuel rod of the fuel assembly.