Proposed is a device for assembling and disassembling a top nozzle of a nuclear fuel assembly wherein the top nozzle of the nuclear fuel assembly is assembled and disassembled with improved convenience, and the load value is measured to ensure stable operations without damaging components. To this end, the device includes a pedestal including a threaded hole through both sides, a screw bar screw-coupled to the threaded hole to reciprocate in a straight line, a top nozzle plate configured to be detachably coupled to the screw bar and to be able to be hooked by and coupled to the top nozzle of the nuclear fuel assembly, and a load cell provided between the top nozzle plate and the screw bar to measure a load value applied to the top nozzle plate hooked on the top nozzle.

The present invention provides a top nozzle for use with PWR nuclear reactors and power plants, and in particular, VVER nuclear reactors. The top nozzle includes a plate portion having a peripheral portion; a hub portion spaced from the plate portion; a plurality of support portions extending from the plate portion to the hub portion; and at least one deflector portion extending inwardly from the peripheral portion at an acute angle with respect to the plate portion.

A combination of a top nozzle and a guide thimble of a nuclear fuel assembly and, more particularly, a structure for joining an inner-extension tube, the top nozzle and the guide thimble. When an inner-extension tube head, which is provided as a means for facilitating removal of the top nozzle of the nuclear fuel assembly from the guide thimble, is removed from an inner-extension tube body to separate the top nozzle from the nuclear fuel assembly, the inner-extension tube body is prevented from undesirably rotating, so that the guide thimble and the inner-extension tube body can maintain the joined state.

Proposed is a device for assembling and disassembling a top nozzle of a nuclear fuel assembly wherein the top nozzle of the nuclear fuel assembly is assembled and disassembled with improved convenience, and the load value is measured to ensure stable operations without damaging components. To this end, the device includes a pedestal including a threaded hole through both sides, a screw bar screw-coupled to the threaded hole to reciprocate in a straight line, a top nozzle plate configured to be detachably coupled to the screw bar and to be able to be hooked by and coupled to the top nozzle of the nuclear fuel assembly, and a load cell provided between the top nozzle plate and the screw bar to measure a load value applied to the top nozzle plate hooked on the top nozzle.

Disclosed is a nuclear fuel assembly suitable for a small modular reactor (SMR), wherein the nuclear fuel assembly includes a spacer grid having 1717 lattice cells, a plurality of fuel rods, each arranged within an associated lattice cell of the spacer grid, guide tubes, each arranged and fixed within an associated lattice cell of the spacer grid, and a top nozzle and a bottom nozzle fixed to an upper end and a lower end of each guide tube, respectively, wherein, with respect to a center cell of the spacer grid, each of eight guide tubes is arranged in an associated one of principal axis directions Ixx and Iyy, each of four guide tubes in an associated one of on-diagonal directions Ixy, and each of 16 guide tubes in an associated one of off-diagonal directions Ixxy and Ixyy.

A segmented fuel assembly for use in a nuclear reactor is disclosed. The segmented fuel assembly comprises a lower nozzle, an upper nozzle, a plurality of guide tubes positioned intermediate the lower nozzle and the upper nozzle, and a plurality of fuel segments positioned intermediate the upper nozzle and the lower nozzle. The plurality of guide tubes are arranged in a first array. Each guide tube defines a longitudinal axis. Each fuel segment comprises a body defining a plurality of coolant flow channels and a plurality of guide tube openings. The guide tube openings are arranged in a second array corresponding to the first array. The guide tubes are positioned in the guide tube openings.

The fuel assembly includes a base material formed of a zirconium alloy and a coating layer, and the coating layer includes a chromium layer formed of chromium or a chromium alloy and a corrosion-resistant layer formed of zirconium alloy or a titanium alloy. The method for producing a fuel assembly includes a step of preparing the base material, a step of forming the chromium layer on a surface of the base material that would otherwise be in contact with cooling water, a step of forming the corrosion-resistant layer on a surface of the chromium layer, and a step of assembling the fuel assembly using the base material. The chromium layer and the corrosion-resistant layer are formed according to a thin plate cladding method, a physical vapor deposition method, a thermal spraying method, a cold spraying method, or a plating method before the assembling using the base material.