Abstract: Disclosed is a breeding nuclear fuel mixture including metallic thorium useable in a nuclear power plant, prepared by mixing uranium dioxide (UO2) or plutonium dioxide (PuO2) having ceramic properties with metallic thorium (Th), in order to enable thorium breeding by neutrons released during nuclear fission of U or Pu and conversion of the bred thorium into a novel nuclear fissile material, i.e., U-233, thereby ensuring continuous nuclear fission. The foregoing nuclear fuel mixture may be burned at a reactor core of a nuclear power plant through thorium breeding over a long period of time. Therefore, when the inventive breeding nuclear fuel mixture is employed in a nuclear power plant, utilization of the nuclear power plant may be increased while maximizing conservation of limited uranium resources.

Abstract: 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.

Abstract: A grid with coolant deflecting channels for used in nuclear fuel assemblies is disclosed. In the grid, two sets of intersecting grid strips are arranged in sets at right angles to each other prior to being encircled by four perimeter strips, thus forming a plurality of four-walled cells individually placing and supporting an elongated fuel rod therein. Each of the grid strips is made up of two narrow sheets which are deformed at a plurality of regularly spaced portions to provide nozzle-type coolant deflecting channels. The channels individually have an upright Y-shaped or reversed Y-shaped configuration capable of so deflecting coolant as to mix low temperature coolant with high temperature coolant. The channels thus form a uniform temperature distribution within a fuel assembly. The channels are so inclined with respect to the axes of the fuel rods as to form wide and linear positioning springs at middle portions thereof.