Korea Atomic Energy Research Institute

Korea Hydro Nuclear Power Co., Ltd.

Kun Woo Song

Jong Hun Kim

Jae Ho Yang

Keon Sik Kim

Ki Won Kang

Hyung Kyu Kim

Dong Seok Oh

Young Woo Rhee

Kang Hee Lee

Kyung Ho Yoon

Tae Soo Chun

Chang Hoon Shin

Young Ho Lee

Jae Yong Kim

Wang Ki In

Youn Ho Jung

Wang Kee In

Tae Hyun Chun

Chang Hwan Shin

Kyung-Ho Yoon

Ki Ju Kang

Dong-Seok Oh

Kang-Hee Lee

Kee Nam Song

Jae-Yong Kim

Young Do Lee

Soo Sung Kim

Dong Joo Kim

A dual-cooled fuel rod's spacer grid with upper and lower dimples, including a blocking area of a flow passage that coolant flows through is reduced and dual-cooled fuel rods are supported, and reduces a turbulent flow of the coolant as well as vibrations of the dual-cooled fuel rods, thereby lessening fretting damage done to the rods. The spacer grid includes a plurality of unit grid straps, each of which includes a body disposed in a vertical direction, an upper dimple protruding from an upper portion of the body, and a lower dimple spaced apart from the upper dimple in a downward direction and protruding from a lower portion of the body. The unit grid straps form a grid structure that have inner grid holes into which the dual-cooled fuel rods are held, and the held dual-cooled fuel rods are each supported in four directions by the upper and lower dimples.

Dual-cooled fuel rod's spacer grids with upper and lower cross-wavy-shape dimple

UOnuclear fuel pellets are fabricated by adding additive powder comprising Mn compound and Al compound into UOpowder.

Uranium dioxide nuclear fuel containing Mn and Al as additives and method of fabricating the same

A lower end plug for an annular nuclear fuel rod includes a support with a great slenderness ratio, a coolant inflow part with an inner inflow space and a plurality of inflow holes in a wall thereof so as to interact with the inflow space, coupled to a lower end of the annular nuclear fuel rod at an upper end thereof, and extending from an upper end of the support in a reverse conical shape such that the inflow space interact with an inner channel of the annular nuclear fuel rod, and a coupler extending from a lower end of the support and coupled with a handing tool of the annular nuclear fuel rod. Thus, although a bottoming phenomenon of the annular nuclear fuel rod occurs, the coolant can be supplied to the inner channel of the annular nuclear fuel rod through the inflow holes of the lower end plug.

Reverse conical lower end plug for an annular nuclear fuel rod

A truss-reinforced spacer grid and a method of manufacturing the same are provided, in which truss members having a small diameter are woven to form a truss structure surrounded by an external plate, and the truss structure is joined to the external plate to thereby improve the strength of the mechanical structure. The truss-reinforced spacer grid includes a truss structure in which horizontal trusses formed by horizontally weaving a plurality of truss members are vertically disposed at regular intervals, and an external plate is joined with ends of the horizontal trusses and surrounds the truss structure.

Truss-reinforced spacer grid and method of manufacturing the same

A spacer grid for nuclear fuel rods includes a plurality of unit spacer grids stacked one on top of another. Each unit spacer grid includes a plurality of unit spacer grid straps disposed at regular intervals in a row, and a plurality of fixing grid straps connected to respective opposite ends of the unit spacer grid straps so as to fix the unit spacer grid straps. Each unit spacer grid strap has convexities alternating with each other on opposite sides thereof at regular intervals, and at least one of the convexities has a diameter greater than the others. The unit spacer grids are rotated in one direction by a 90 or 180 degree angle when being stacked.

Unit spacer grid strap, unit spacer grid, and spacer grid for nuclear fuel rods

An intermediate end plug assembly for a segmented fuel rod can stably support the fuel rod to the end of its cycle even if an interval between the fuel rods becomes narrow due to application of a dual-cooled fuel rod, and reduce excess vibration induced by flows of interior and exterior channels of the dual-cooled fuel rod for obtaining high burnup and output. To this end, the fuel rod has a segmented structure so as to make its length short. A lower intermediate end plug includes at least one channel hole, through which a coolant flows into an internal channel of the fuel rod, so that a possibility of causing departure from nuclear boiling ratio (DNBR) of the dual-cooled fuel rod is reduced.

Intermediate end plug assembly for segmented fuel rod and segmented fuel rod having the same

There is provided a method of producing UOpowder having large surface area and small particle size by oxidizing defective UOpellets and manufacturing nuclear fuel pellets which are stable in a pore structure and high in density through the use of a mixture comprising UOpowder and UOpowder. The method includes producing an U308 powder having a surface area of at least 1 m/g by oxidizing defective UOpellets at a temperature of 300 to 370&#xb0; C. in such a way that a maximum weight increase rate per 1 g of the UOpellets is up to 0.06 wt %/min; producing a mixed powder by mixing the UOpowder with an UOpowder by 2 to 15 wt %; producing a compact by compression molding the mixed powder; and sintering the compact in a reducing gas atmosphere at a temperature of 1600 to 1800&#xb0; C. In addition, a small amount of an Al-compound may be added to the oxidized UOpowder before the UOpowder is mixed with the UOpowder. The additive such as Al is mixed with the UOpowder and then mixed with the UOpowder to produce the pellets by a conventional production method. This ensures a stable pore structure, high density and a considerable increase in a crystal grain size.

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A method for manufacturing an annular nuclear fuel pellet is provided. In the method, an annular nuclear fuel green compact whose lateral cross-section is a trapezoid is prepared. The thickness of the annular nuclear fuel green compact reduces along one direction of the central axis, and a green density of the nuclear fuel green compact increases along one direction of the central axis. The annular nuclear fuel green compact is sintered under a reducing gas atmosphere so that the annular nuclear fuel pellet is obtained. According to this method, the annular pellet which has uniform inner and outer diameters and small diametric tolerances along the pellet height is fabricated without grinding the pellet surfaces.

Method for manufacturing sintered annular nuclear fuel pellet without surface grinding

An apparatus and method for welding strap connections between inner grid straps of a spacer grid using a laser tool, and a spacer grid manufactured by the same, in which the strap connections between the inner grid straps of the spacer grid are seam-welded continuously or intermittently using the laser tool, so that the structural strength of the spacer grid is increased, a spattering phenomenon, in which a welded material is spattered during welding, is reduced, and thermal deformation is reduced. Further, fine welding is possible, and thus the welded bead of each strap connection between the inner grid straps can have a small size, and the number of welding defects can be reduced. In addition, the flow resistance of a coolant is reduced, and thereby the pressure drop of the coolant can be reduced As a result, the load on a flow pump for the coolant can be reduced, and economic efficiency and safety can be improved.

Apparatus and method for welding strap connections between inner grid straps of spacer grid using laser tool, and spacer grid manufactured using the same

A method for fabricating a sintered duplex nuclear fuel pellet includes the steps of: preparing a first powder composed of a material selected from the group consisting of UOand UO&#x2014;ErO, and a second powder composed of UO&#x2014;GdOand a sintering additive; producing a duplex compact consisting of an annular outer portion composed of the first powder and a cylindrical inner portion composed of the second powder; and sintering the duplex compact under a reducing gas atmosphere, wherein the sintering additive contains manganese of 0.001% to 2% by weight based on the total weight of the cylindrical inner portion.

Fabrication method of sintered duplex nuclear fuel pellet

The present invention relates to a nuclear fuel body comprising tungsten network and a method for manufacturing the same, more particularly, a nuclear fuel body in which tungsten network is continuously formed over the entire or some parts of a sintered body and a method for manufacturing the same. The sintered body in the nuclear fuel body of the present invention contains tungsten network having excellent heat conductivity, leading to the enhancement of heat conductivity of the nuclear fuel sintered body itself with decreasing the temperature of the nuclear fuel, so that it can contribute to the improvement in safety and performance of nuclear fuel.

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Daejeon, South Korea

Kun Woo Song