Nuclear fuel pellet, a fuel rod, and a fuel assembly

Abstract

A nuclear fuel pellet for a nuclear reactor is disclosed. The pellet comprises a metallic matrix and ceramic fuel particles of a fissile material dispersed in the metallic matrix. The metallic matrix is an alloy consisting of the principle elements U, Zr, Nb and Ti, and of possible rest elements. The concentration of each of the principle elements in the metallic matrix is at the most 50 molar-%.

Claims

1. A nuclear fuel pellet for a nuclear reactor, comprising: a metallic matrix; and ceramic fuel particles of a fissile material dispersed in the metallic matrix, wherein the metallic matrix is an alloy of U.sub.5-6Zr.sub.3-4NbTi wherein a concentration of each element in the metallic matrix is at most 50 molar-%.

2. The nuclear fuel pellet according to claim 1, wherein the concentration of each of the elements in the metallic matrix is at least 5 molar-%.

3. The nuclear fuel pellet according to claim 1, wherein the alloy is a single phase alloy with precipitates constituting less than 5 volume-% of the alloy.

4. The nuclear fuel pellet according to claim 1, wherein the alloy is a High Entrophy Alloy; (HEA).

5. The nuclear fuel pellet according to claim 1, wherein the alloy has a body centered cubic structure.

6. The nuclear fuel pellet according to claim 1, wherein a total concentration of additional elements in the metallic matrix is at most 5 molar-%.

7. The nuclear fuel pellet according to claim 1, wherein the ceramic fuel particles are uniformly dispersed in the metallic matrix.

8. The nuclear fuel pellet according to claim 1, wherein the fissile material is selected from the group consisting of actinide oxide, actinide nitride, actinide silicide and actinide carbide.

9. The nuclear fuel pellet according to claim 1, wherein the fissile material is selected from the group consisting of UO.sub.2, U.sub.3Si.sub.2, U.sub.3Si, USi, UN, PuO.sub.2, Pu.sub.3Si.sub.2, Pu.sub.3Si, PuSi, PuN, ThO.sub.2, Th.sub.3Si.sub.2, Th.sub.3Si, ThSi and ThN.

10. A fuel rod comprising a cladding tube enclosing a plurality of nuclear fuel pellets according to claim 1.

11. A fuel assembly for use in a nuclear reactor, comprising a plurality of fuel rods according to claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now to be explained more closed through a description of various embodiments and with reference to the drawings attached hereto.

(2) FIG. 1 discloses schematically a longitudinal sectional view of a fuel assembly for a nuclear reactor.

(3) FIG. 2 discloses schematically a longitudinal sectional view of a fuel rod of the fuel assembly in FIG. 1.

(4) FIG. 3 discloses longitudinal sectional view of a nuclear fuel pellet according to a first embodiment.

DETAILED DESCRIPTION

(5) FIG. 1 discloses a fuel assembly 1 for use in nuclear reactor, in particular in a water cooled light water reactors, LWR, such as a Boiling Water Reactor, BWR, or a Pressurized Water reactor, PWR. The fuel assembly 1 comprises a bottom member 2, a top member 3 and a plurality of elongated fuel rods 4 extending between the bottom member 2 and the top member 3. The fuel rods 4 are maintained in their positions by means of a plurality of spacers 5. Furthermore, the fuel assembly 1 may, for instance when to be used in a BWR, comprise a flow channel or fuel box indicated by dashed lines 6 and surrounding the fuel rods 4.

(6) FIG. 2 discloses one of the fuel rods 4 of the fuel assembly 1 of FIG. 1. The fuel rod 4 comprises a nuclear fuel in the form of a plurality of nuclear fuel pellets 10, and a cladding tube 11 enclosing the nuclear fuel pellets 10. The fuel rod 4 comprises a bottom plug 12 sealing a lower end of the cladding tube 11, and a top plug 13 sealing an upper end of the fuel rod 4. The nuclear fuel pellets 10 are arranged in a pile in the cladding tube 11. The cladding tube 11 thus encloses the fuel pellets 10 and a gas. A spring 14 is arranged in an upper plenum 15 between the pile of nuclear fuel pellets 10 and the top plug 13. The spring 14 presses the pile of nuclear fuel pellets 10 against the bottom plug 12.

(7) An embodiment of one of the nuclear fuel pellets 10 is disclosed in FIG. 3. The nuclear fuel pellet 10 comprises, or consists of a metallic matrix 20 and ceramic fuel particles 21 of a fissile material dispersed in the matrix 20. The ceramic fuel particles 21 may be uniformly and randomly dispersed in the matrix 20.

(8) The number of ceramic fuel particles 21 in each nuclear fuel pellet 10 may be very high. The volume ratio particles/matrix may be less than 0.01:1 or 0.01:1 up to 1:0.01.

(9) The ceramic fuel particles 21 may have a spherical shape, or substantially spherical shape, or may be a form of any shape.

(10) The size of the ceramic fuel particles 21 may vary. For instance, the ceramic fuel particles 21 may have an extension, such as the diameter in the spherical example, which lies in the range from 100 to 2000 micrometers.

(11) The ceramic fuel particles 21 comprise or consist of at least one fissile material. The fissile material is selected from the group of actinide oxide, actinide nitride, actinide silicide and actinide carbide. In particular, the fissile material selected from the group of UO.sub.2, U.sub.3Si.sub.2, U.sub.3Si, USi, UN, PuO.sub.2, Pu.sub.3Si.sub.2, Pu.sub.3Si, PuSi, PuN, ThO.sub.2, Th.sub.3Si.sub.2, Th.sub.3Si, ThSi and ThN. The ceramic fuel particles 21 may thus comprise or consist of one or more of these materials.

(12) The metallic matrix 20 is an alloy consisting of the principle elements U, Zr, Nb and Ti, and possible residual elements. The alloy of the metallic matrix 20 may have a body centered cubic, BCC, structure.

(13) The alloy is may be a single phase alloy, or a near single phase alloy with precipitates constituting less than 5 volume-% of the alloy.

(14) The concentration of each of the principle elements in the metallic matrix 20 is at the most 50 molar-%, and at least 5 molar-%.

(15) The total concentration of the possible rest elements in the metallic matrix 20 is at the most 5 molar-%, preferably at the most 4 molar-%, more preferably at the most 3 molar-%, most preferably at the most 2 molar-%.

(16) The single phase alloy, or near single phase alloy, of the metallic matrix 20 is a so called High Entropy Alloy, HEA.

(17) More specifically, the single phase alloy, or near single alloy, of the metallic matrix 20 may be U.sub.5-6Zr.sub.3-4NbTi.

(18) The nuclear fuel pellet 10 may also comprise other particles than ceramic fuel particles 21, in particular absorbing particles comprising a neutron absorbing substance. Such a substance with a high neutron absorption cross-section may comprise boron, gadolinium, etc.

(19) The nuclear fuel pellet 10 may be a sintered nuclear fuel pellet 10. A powder of the principle elements and the rest elements are mixed with the ceramic fuel particles 21, and possible absorbing particles, to form a mixture. The ceramic fuel particles 21 may have been sintered in advance. The mixture is compressed to a green body, which is then sintered in a suitable oven/furnace or any other suitable method, such as spark-plasma sintering (SPS), to the nuclear fuel pellet 10.

(20) The nuclear fuel pellet 10 may also as an alternative be manufactured in other ways, for instance through casting or extrusion.

(21) The present invention is not limited to the embodiments disclosed and described herein, but may be varied and modified within the scope of the following claims.