Korea Atomic Energy Research Institute

Korea Hydro Nuclear Power Co., Ltd.

Other

Kyung-Ho Yoon

Hyung-Kyu Kim

Dong-Seok Oh

Tae-Hyun Chun

Wang-Kee In

Kee-Nam Song

Kang-Hee Lee

Heung-Seok Kang

Jae-Yong Kim

Young-Ho Lee

Youn-Ho Jung

Kun-Woo Song

Dae-Ho Kim

Chang Hwan Shin

Jong-Hun Kim

Hyung Kyu Kim

Dong Seok Oh

Kun Woo Song

Wang Kee In

Tae Hyun Chun

Young Do Lee

Je-Geon Bang

Chang-Hwan Shin

Kyung-Jin Park

Yeon-Ho Jung

A dual-cooled nuclear fuel rod and a method of manufacturing the same are provided. The nuclear fuel rod includes an outer cladding tube having a circular cross section, an inner cladding tube having an outer diameter smaller than an inner diameter of the outer cladding tube, and a length longer than the outer cladding tube, and located in parallel in the outer cladding tube, a pellet charged in a space between the outer and inner cladding tubes and generating energy by nuclear fission, and first and second end plugs coupling opposite ends of the outer cladding tube to stepped outer joints formed on outer circumferences of first ends thereof and coupling opposite ends of the inner cladding tube to stepped inner joints formed on inner circumferences of the first ends thereof.

Dual-cooled nuclear fuel rod having annular plugs and method of manufacturing 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 spacer grid for dual-cooling nuclear fuel rods arranged at a narrow interval. The spacer grid solves the problem in which, since the dual-cooling nuclear fuel rods are used to improve the cooling performance and stability of nuclear fuel and obtain high burnup and output, the outer diameter of each dual-cooling nuclear fuel rod is increased, and thus the gap between each dual-cooling nuclear fuel rod and the grid strap is decreased. The spacer grid includes first grid straps and second grid straps, which are crossed and arranged in transverse and longitudinal directions at regular intervals and have the shape of a flat strip, and support structures, which are fitted into the first and second grid straps around intersections of the first and second grid straps so as to support the dual-cooling nuclear fuel rods.

Spacer grid for dual-cooling nuclear fuel rods using intersectional support structures

A perforated plate support supports dual-cooled fuel rods, each of which has concentric outer and inner tubes and is coupled with upper and lower end plugs at upper and lower ends thereof, and guide thimbles, each of which is used as a passage for a control rod. The perforated plate support is formed as a support plate having the shape of a flat plate, which includes internal channel holes, each of which has a diameter corresponding to an outer diameter of the inner tube, guide thimble holes, each of which has a diameter corresponding to an outer diameter of the guide thimble, and sub-channel holes around each internal channel hole. The upper or lower end of the dual-cooled fuel rod is coupled to the support plate such that the outer diameter of the inner tube is matched with the diameter of the internal channel hole.

Perforated plate support for dual-cooled segmented fuel rod

A spacer grid can be applied to close-spaced nuclear fuel rods. The spacer grid is directed to solve the problem in which, as the outer diameter of each nuclear fuel rod increases due to the use of dual-cooled nuclear fuel rods for improving cooling performance and obtaining high combustion and high output power, the gap between the neighboring nuclear fuel rods is narrowed to thus make it impossible to use an existing spacer grid. The spacer grid is a combination of unit grid straps, each of which has supports for supporting each of the nuclear fuel rods set in a narrow array and has a sheet shape, which are combined with each other. The supports are located at positions shifted from the longitudinal central line of each unit grid strap toward sub-channels.

Spacer grid for close-spaced nuclear fuel rods

A grid strap includes a spacer grid spring that increases the conformal contact area with a fuel rod of a nuclear fuel rod assembly. The shape of the spacer grid spring is optimized, thereby increasing the elasticity of the spacer grid spring contacting the fuel rod, expanding the conformal contact area with a contact portion between the spacer grid spring and fuel rod to obtain uniform stress distribution, and reducing excessive plastic deformation of the spacer grid spring. Further, magnitude and distribution of contact pressure between the fuel rod and the spacer grid spring are improved, thereby reducing the possibility of fretting wear caused by contact between the fuel rod and the spacer grid spring. Lastly, the elastic behavior region of the spacer grid spring is expanded, so that the fuel rod can be reliably supported until the fuel rod expires despite changes in the supporting conditions of the fuel rod.

Spacer grid spring for increasing the conformal contact area with fuel rod

A spacer grid used for placing and supporting fuel rods in nuclear reactor fuel assemblies is disclosed. The spacer grid of this invention has a plurality of inner strips intersecting each other to form a plurality of guide tube cells and a plurality of fuel rod cells, with a plurality of mixing blades projecting upward from the inner strips at intersections of the inner strips. The spacer grid further includes a plurality of perimeter strips to encircle the intersecting inner strips. Each of the perimeter strips is fabricated with a plurality of unit intermediate strips and a plurality of unit corner strips, with a grid spring provided on each of the unit strips. The grid spring includes a vertical opening formed at a central area of each of the unit strips, a vertical support part extending vertically between the central portions of top and bottom edges of the vertical opening, and a fuel rod support part provided at a central portion of the vertical support part while being bent to have an outward rounded cross-section. The vertical support part is bent at two steps, and the fuel rod support part is bent to be in equiangular contact with each of the fuel rods, thus accomplishing a uniform contact pressure distribution when the fuel rod support part is in contact with each of the fuel rods.

Spacer grid for nuclear reactor fuel assemblies

A duct-type spacer grid for nuclear fuel assemblies is disclosed. In this spacer grid, a plurality of duct-shaped grid elements, individually having an octagonal cell, are closely arranged in parallel and are welded together, thus forming a matrix structure. The grid elements do not pass across the center of the subchannel of the assembly, thus effectively reducing pressure loss. Each of the grid elements is formed as an independent cell, and so they effectively resist against a lateral impact. A plurality of integral type swirl flow vanes, having different heights or same height, axially extend from the top of the grid to be positioned within each subchannel. The swirl flow vanes are bent outwardly, and so they do not contact the fuel rods during an insertion of the fuel rods into the cells. In the spacer grid, the fuel rods are supported within the cells by line contact springs without using any dimple. The spacer grid thus uniformly distributes its spring force on the fuel rods and almost completely prevents damage of the fuel rods due to fretting wear.

Duct-type spacer grid with swirl flow vane for nuclear fuel assembly

A nuclear fuel spacer grid, fabricated by intersecting a plurality of zircaloy or inconel grid strips and used for placing and supporting a plurality of elongated fuel rods within a nuclear fuel assembly, is disclosed. In the spacer grid of this invention, each of the grid strips is not cut away to form separate springs or dimples for supporting the fuel rods, but has an axial slot extending from one end of each strip to a length. The grid strips are intersected at the slots prior to being welded together into a single grid structure at a welding tap formed at an outside end or a middle portion of each of the slots. Each of the grid strips also has a dipper-shaped coolant mixing vane, or a dipper vane, at each of the upper and lower ends thereof. The spacer grid thus maximizes the thermal hydraulic coolant mixing effect within a fuel assembly and stably supports the fuel rods within the assembly while improving the mechanical/structural strength of the assembly, such as a buckling strength.

Nuclear fuel spacer grid with dipper vanes

Duct-type spacer grid with swirl flow vanes for nuclear fuel assemblies

A fuel assembly spacer grid including swirl deflectors respectively arranged at interconnections between interconnecting longitudinally and laterally-extending straps on upper ends of the interconnecting straps adapted to support fuel elements of a nuclear fuel assembly. Each of the swirl deflectors has four vanes bent to have an air vane shape. By virtue of this configuration, an improvement in the efficiency of the spacer grid cooling the fuel elements. The spacer grid also includes springs each configured to generate not only a main spring force caused by a displacement of the spring occurring when the spring comes into contact with a fuel element placed in a reactor core, but also an additional spring force caused by hydraulic pressure applied to the spring. Each spring, which is in a fixed state at one end thereof, has a free bent portion at the other end. By virtue of such a spring configuration, it is possible to compensate for a reduction in the initial spring force of the spring resulting from a change in the property of the spring material. The spring has a curved contact portion configured in such a manner that it is in conformal surface contact with a circumferential surface of the fuel element, thereby enhancing vibration suppressing and abrasion resistance forces.

Growing community of inventors

Daejeon, South Korea

Kyung-Ho Yoon