Plurality of layers form a nuclear fission reactor structure, each layer having an inner segment body, an intermediate segment body, and an outer segment body (each segment body separated by an interface). The layers include a plurality of cladding arms having involute curve shapes that spirally radiate outward from a radially inner end to a radially outer end. Chambers in the involute curve shaped cladding arm contain fuel compositions (and/or other materials such as moderators and poisons). The design of the involute curve shaped cladding arms and the composition of the materials conform to neutronic and thermal management requirements for the nuclear fission reactor and are of sufficiently common design and/or have sufficiently few variations as to reduce manufacturing complexity and manufacturing variability.

A spot welding device for a nuclear fuel skeleton, which is assembled by spot-welding guide tubes for control rods and a instrumentation tube for measuring a state of an inside of a nuclear reactor to a spacer grid that has a plurality of cells formed in a thickness direction of a plate-shaped frame for inserting fuel rods, has a instrumentation tube hole formed at a center, and has four guide tube holes formed symmetrically above and below the instrumentation tube hole. The device includes: a welding gun including: a body, a first holder and a second holder extending from a side of the body and having respective electrodes facing each other at ends, respectively, and a driving unit disposed on the body and adjusting a distance between the electrodes; and a robot connected to the welding gun and having a rotary joint for rotating the welding gun.

A system includes a load-following nuclear power generator including a nuclear reactor configured to generate variable amounts of electricity. The system also includes an electric drive and a propeller controlled by the electric drive.

A spacer grid includes interlocked straps comprising metal sheets or plates welded together to define a spacer grid having a top and bottom. The interlocked straps define a plurality of cells comprising vertical passages connecting the top and bottom of the spacer grid. The cells include: upper dimples proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; lower dimples proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid; cantilevered upper springs having fuel rod engagement surfaces proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; and cantilevered lower springs having fuel rod engagement surfaces proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid.

A method for encapsulating a fuel rod or a fuel rod section in a container includes inserting the fuel rod or fuel rod section into the container. One of the ends of the container is connected to a purging-gas line. The container is dehydrated and purged by use of a purging gas. The ends of the container are connected to a bypass line in such a way that a closed gas circuit is produced and a hot gas is circulated in the gas circuit until the absolute moisture content reaches an end value at which the absolute moisture content no longer rises. The container is disconnected from the gas circuit and subsequently the container is closed in a fluid-tight manner at both ends.

A charging device of a welding fixture of spacer grid comprises a base frame; a conveyor for conveying a welding fixture horizontally over the base frame; and a gripper located over the base frame for gripping a welding fixture conveyed along the conveyor to charge a welding fixture into a welding chamber, wherein the gripper comprises a gripper body; and a gripping part installed horizontal to the end of the gripper body for gripping a welding fixture and capable of tilting in vertical direction to the gripper body in case more than a predetermined load is applied as a vertical load.

A charging device of a welding fixture of spacer grid comprises a base frame; a conveyor for conveying a welding fixture horizontally over the base frame; and a gripper located over the base frame for gripping a welding fixture conveyed along the conveyor to charge a welding fixture into a welding chamber, wherein the gripper comprises a gripper body; and a gripping part installed horizontal to the end of the gripper body for gripping a welding fixture and capable of tilting in vertical direction to the gripper body in case more than a predetermined load is applied as a vertical load.

A spacer grid includes interlocked straps comprising metal sheets or plates welded together to define a spacer grid having a top and bottom. The interlocked straps define a plurality of cells comprising vertical passages connecting the top and bottom of the spacer grid. The cells include: upper dimples proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; lower dimples proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid; cantilevered upper springs having fuel rod engagement surfaces proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; and cantilevered lower springs having fuel rod engagement surfaces proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid.

A spacer grid includes interlocked straps comprising metal sheets or plates welded together to define a spacer grid having a top and bottom. The interlocked straps define a plurality of cells comprising vertical passages connecting the top and bottom of the spacer grid. The cells include: upper dimples proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; lower dimples proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid; cantilevered upper springs having fuel rod engagement surfaces proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; and cantilevered lower springs having fuel rod engagement surfaces proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid.

A nuclear fuel assembly body with a lengthways axis includes first and second tubular segments made from a metal material forming the lengthways ends of the assembly body. A frame made from a metal material connects the first and second segments. The frame is openworked. A ceramic tubular internal structure is positioned between the first and second segments inside the frame.