Abstract: A fuel pellet visual inspection device for manufacturing a nuclear fuel rod improves convenience and workability of visual inspection of a plurality of pellets by simultaneously turning over the pellet. The fuel pellet visual inspection device for manufacturing a nuclear fuel rod includes: a rotary shaft; a pair of seats hinged to the hinge shaft, arranged at both sides from the rotary shaft, and seated with a tray thereon; and a dust-collecting unit disposed under the pair of seats and collecting dust scattered from pellets.

Abstract: A passive auxiliary condensing apparatus of a nuclear power plant includes a steam generation unit configured to heat a water supplied thereto into a steam by a heat produced when operating a nuclear reactor, a water cooled heat exchange unit connected to the steam generation unit and configured to store a cooling water therein to condense the steam provided from the steam generation unit, and a steam-water separation tank including a first side connected to the water cooled heat exchange unit and a second side connected to the steam generation unit, wherein a mixture of a water and a steam provided from the water cooled heat exchange unit is separated into the water and the steam to provide only the water to the steam generation unit.

Abstract: This invention relates to a composition and method for manufacturing a large-grained uranium oxide nuclear fuel pellet containing an additive. The nuclear fuel pellet is configured such that a uranium oxide powder and an additive powder composed of an Mg compound and a Si compound or Ca compound and a Al compound are mixed together, thus increasing a grain size to thus suppress the release of fission products, thereby increasing the stability of nuclear fuel, preventing cladding tubes from breaking, and contributing to the stable operation of nuclear power plants, ultimately increasing the overall stability of nuclear power plants including nuclear fuel.

Abstract: The present invention relates to a lower end fitting for reducing flow resistance due to an in-core instrument in a nuclear fuel assembly, that is, a lower end fitting (100) having a plurality of flow holes for a nuclear fuel assembly, in which the flow holes (121) are formed under an assembly groove in which an instrumentation tube (131) for a nuclear fuel assembly is inserted, and at least two or more flow holes (121) are formed at a predetermined distance from the central axis (C) of the instrumentation tube (131).

Abstract: The present invention relates to a top nozzle and a nuclear reactor in which an in-core instrument, which is supposed to be inserted through a top head of a nuclear reactor, is inserted through a guide pin for an upper core plate. In a nuclear reactor including guide pins for aligning a top nozzle for a nuclear fuel assembly with an upper core plate of a nuclear reactor, a guide hole (210) is axially formed through the guide pins (200) and in-core instruments (10) are inserted through the guide holes (210).

Abstract: A gap control device for a Pilger die assembly of cold Pilger mills. The gap control device can independently control the height of a pair of bearing blocks which axially support an upper die. A lower plate has first and second receiving holes which respectively correspond to the upper portions of a pair of bearing blocks. First and second wedge plates are fitted into the receiving holes, and respectively have inclined surfaces on the upper portions thereof. First and second adjustment blocks respectively have inclined guide surfaces to be in surface contact with the inclined surfaces of the wedge plates, and are movable horizontally with respect to the lower plate. An upper plate is assembled to the upper portion of the lower plate to cover the adjustment blocks. First and second adjustment bolts allow the first and second adjustment blocks to be respectively manipulated in a horizontal direction.

Abstract: A method for loading fuel pellets for manufacturing a nuclear fuel rod is provided. The method includes arranging fuel pellets in a row on a tray, aligning the fuel pellets in the row on the tray such that the fuel pellets are closely in contact with one another, obtaining a total length of the pellets in the row by measuring the fuel pellets in the row on the tray, and comparing the total length with a predetermined length. When the total length is smaller than the predetermined length by a difference greater than an average unit length of the pellet, one or more fuel pellets are added in the row until to increase the total length until the difference becomes smaller than the average unit length of the fuel pellet.

Abstract: Disclosed is a fuel rod auto-loading apparatus for a nuclear fuel assembly, which disposes fuel rods in a fuel rod case in a bundle to assemble the fuel rods into the nuclear fuel assembly. The fuel rod auto-loading apparatus includes a fuel rod storage unit having a plurality of stacked racks for fuel rods, a fuel rod loading unit raised/lowered to the racks and transferring the fuel rods, a feeding unit placing the fuel rods in rows and loading the fuel rods into the fuel rod case, a fuel rod unloading unit selectively unloading some of the fuel rods stored in the fuel rod storage unit and transferring the fuel rods to the feeding unit, a fuel rod assembly lifter which is disposed parallel to the feeding unit, and a controller controlling driving of the fuel rod loading unit, the feeding unit, and the fuel rod unloading unit.

Abstract: 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.

Abstract: Disclosed is a plasma welding apparatus for a guide thimble and guide thimble end plug of a nuclear fuel assembly, which includes: a welding chamber (100) includes an end-plug inserting part (110) into which the end plug (10) is inserted, a guide-thimble inserting part (120) which is provided on the same axis as the end-plug inserting part (110) and into which the guide thimble (20) is inserted and fixed, a torch assembling part (130) to which a plasma welding torch (131) is assembled so as to make a right angle with the end-plug inserting part (110) and the guide-thimble inserting part (120), and argon inflow and outflow ports (141, 142) through which argon is supplied or discharged; an end-plug transfer unit (210) supplying the end plug (10) to the end-plug inserting part (110); and an guide-thimble transfer unit (220) transferring the guide thimble (20) to the guide-thimble inserting part (120).

Abstract: An apparatus for cooling a spent fuel pool having a heat exchanger includes a cooling water pool positioned above the spent fuel pool; a floating device configured to be elevated according to a water level of a cooling water in the spent fuel pool; and an emergency cooling water supply pipe configured to form a path through which the cooling water of the cooling water pool is moved to the spent fuel pool and configured to include a floating valve that opens or closes a flow passage of the cooling water in connection with the elevation of the floating device.

Abstract: A passive cooling system of a nuclear power plant includes a steam generator, a cooling water storage tank, a water cooling heat exchanger, an air cooling heat exchanger, a divergence valve, and a cooling tower. The steam generator generates steam by heat exchange with a primary coolant system, and the cooling water storage tank stores cooling water therein. The water cooling heat exchanger is disposed in the cooling water storage tank, and the air cooling heat exchanger is connected to the steam generator. The divergence valve is controllable to divert steam from the steam generator into both the water cooling heat exchanger and the air cooling heat exchanger. Each of the cooling water storage tank, the water cooling heat exchanger, and the air cooling heat exchanger are located in the cooling tower.

Abstract: 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.

Abstract: A joint structure between 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.

Abstract: Disclosed herein are zirconium alloy compositions having a low hydrogen pick-up rate and high hydrogen embrittlement resistance. This zirconium alloy composition can be usefully used as a nuclear fuel components in a nuclear power plant because it has a very low hydrogen pick-up rate and high hydrogen embrittlement resistance under operation environments of nuclear power plant.

Abstract: A method for loading fuel pellets for manufacturing a nuclear fuel rod comprises arranging fuel pellets in a row on a plurality of trays, measuring a whole length of the fuel pellets in the row on each of the plurality of trays and obtaining a total length of the pellets by accumulating the whole length of the fuel pellets one after another for the plurality of trays, comparing the total length with a predetermined length, and increasing or decreasing one or more fuel pellets in the row of a last tray of the plurality of the trays such that the total length of the pellets is less than the predetermined length and a length difference between the total length of the pellets and the predetermined length is within a length of one fuel pellet.

Abstract: A zirconium alloy is manufactured through melting; solution heat treatment at 1,000 to 1,050° C. for 30 to 40 min and ?-quenching using water; preheating at 630 to 650° C. for 20 to 30 min and hot rolling at a reduction ratio of 60 to 65%; primary intermediate vacuum annealing at 570 to 590° C. for 3 to 4 hr and primarily cold-rolled at a reduction ratio of 30 to 40%; secondary intermediate vacuum annealing at 560 to 580° C. for 2 to 3 hr and secondarily cold-rolled at a reduction ratio of 50 to 60%; tertiary intermediate vacuum annealing at 560 to 580° C. for 2 to 3 hr and tertiarily cold-rolled at a reduction ratio of 30 to 40%; and final vacuum annealing at 440 to 650° C. for 7 to 9 hr.

Abstract: A zirconium alloy is manufactured through melting; solution heat treatment at 1,000 to 1,050° C. (?) for 30 to 40 min and ?-quenching using water; preheating at 630 to 650° C. for 20 to 30 min and hot rolling at a reduction ratio of 60 to 65%; primary intermediate vacuum annealing at 570 to 590° C. for 3 to 4 hr and primarily cold-rolled at a reduction ratio of 30 to 40%; secondary intermediate vacuum annealing at 560 to 580° C. for 2 to 3 hr and secondarily cold-rolled at a reduction ratio of 50 to 60%; tertiary intermediate vacuum annealing at 560 to 580° C. for 2 to 3 hr and tertiarily cold-rolled at a reduction ratio of 30 to 40%; and final vacuum annealing at 460 to 590° C. for 7 to 9 hr.

Abstract: A joint structure between 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.

Abstract: There are provided a method of synthesizing axial power distributions of a nuclear reactor core using a neural network circuit and an in-core monitoring system (ICOMS) using the same, in which using the neural network circuit including an input layer, an output layer, and at least one hidden layer, each layer being configured with at least one node, each node of one layer being connected to nodes of the other layers, node-to-node connections being made with connection weights varied based on a learning result, optimum connection weights between the respective nodes constituting the neural network circuit are determined through learning based on various core design data applied to the design of a nuclear reactor core of a nuclear power plant, and axial power distributions of the nuclear reactor core are synthesized based on in-core detector signals measured by in-core detectors during operation of a nuclear reactor, thereby more accurately replicating axial power distributions of the nuclear reactor core throu