Korea Atomic Energy Research Institute

Other

Korea Hydro Nuclear Power Co., Ltd.

Kee-Nam Song

Kyung-Ho Yoon

Dong-Seok Oh

Wang-Kee In

Tae-Hyun Chun

Heung-Seok Kang

Hyung-Kyu Kim

Youn-Ho Jung

Dae-Ho Kim

Kun-Woo Song

Kang-Hee Lee

Won-Jae Lee

Yong-Wan Kim

Je-Geon Bang

Jong-Wha Chang

Kyung-Jin Park

Yeon-Ho Jung

Provided is a method of designing a coaxial dual-tube type hot gas duct for a very-high-temperature reactor. When determining the outer diameter of an inner tube and the inner diameter of a pressure tube, both of which defines an annular part of the hot gas duct having a dual-tube shape, one selected from hydraulic heads, flow rates, and hydraulic heads of very-high-temperature helium gas flowing to a very-high-temperature region and low-temperature helium gas flowing to a low-temperature region is taken into consideration as well as is a relation of about heat balance model, so that it is possible to minimize flow induced vibrations caused by the flow of a fluid.

Method for designing concentric axis double hot gas duct for very high temperature reactor

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.

Fuel assembly spacer grid with swirl deflectors and hydraulic pressure springs

Growing community of inventors

Taejon-si, South Korea

Kee-Nam Song