Fuel Assembly and Reactor Loaded with the Same

Patent metadata

Field	Value
Publication number	US-2019051421-A1
Application number	US-201616078937-A
Country	US
Kind code	A1
Filing date	Feb 23, 2016
Priority date	Feb 23, 2016
Publication date	Feb 14, 2019
Grant date	—

Abstract

A fuel assembly capable of linearizing change of an infinite multiplication factor of a fuel and flattening excess reactivity while increasing average fissile plutonium enrichment of a MOX fuel, and a reactor loaded with the fuel assembly can be provided. A fuel assembly includes first fuel rods containing Pu and not containing burnable poison, a second fuel rod containing uranium and burnable poison and not containing Pu, a water rod, and a channel box accommodating the first and second fuel rods and the water rod in a bundle. The second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in a horizontal section, N2<N1 (N2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged on the outermost periphery is N1 and the number of the second fuel rods arranged adjacent to the water rod is N2, and W2<N2+W0<W1 (W2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged without being vertically and/or horizontally adjacent to each other in the horizontal section is W0, the number of the second fuel rods arranged vertically and/or horizontally adjacent to only one second fuel rod in the horizontal section is W1, and the number of the second fuel rods arranged vertically and/or horizontally adjacent to two second fuel rods in the horizontal section is W2, of the second fuel rods arranged on the outermost periphery.

First claim

1 . A fuel assembly comprising: at least, a first fuel rod containing plutonium and not containing burnable poison; a second fuel rod containing uranium and burnable poison and not containing plutonium; a water rod; and a channel box having a rectangular shape in horizontal section and accommodating the first fuel rod, the second fuel rod, and the water rod in a bundle, wherein
the second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in the horizontal section, N2<N1 (N2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged on the outermost periphery is N1 and the number of the second fuel rods arranged adjacent to the water rod is N2, and W2<N2+W0<W1 (W2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged without being vertically and/or horizontally adjacent to each other in the horizontal section is W0, the number of the second fuel rods arranged vertically and/or horizontally adjacent to only one second fuel rod in the horizontal section is W1, and the number of the second fuel rods arranged vertically and/or horizontally adjacent to two second fuel rods in the horizontal section is W2, of the second fuel rods arranged on the outermost periphery.

2 . The fuel assembly according to claim 1 , wherein
average fissile plutonium enrichment in the horizontal section is 4.0% or more.

3 . The fuel assembly according to claim 2 , wherein
the second fuel rod arranged vertically and/or horizontally adjacent to two second fuel rods in the horizontal section is arranged at a corner portion of the channel box.

4 . The fuel assembly according to claim 2 , wherein
the burnable poison contained in the second fuel rod is gadolinium.

5 . The fuel assembly according to claim 3 , wherein
the burnable poison contained in the second fuel rod is gadolinium.

6 . The fuel assembly according to claim 4 , wherein
the fuel assembly includes a nine-row by nine-column fuel grid array, and the first fuel rod includes thirty four fuel rods with fissile plutonium enrichment of 6.1 wt %, twenty fuel rods with fissile plutonium enrichment of 4.2 wt %, five fuel rods with fissile plutonium enrichment of 2.5 wt %, and eight partial length fuel rods with fissile plutonium enrichment of 6.1 wt %.

7 . The fuel assembly according to claim 4 , wherein
the fuel assembly includes a nine-row by nine-column fuel grid array, and the first fuel rod includes thirty two fuel rods with fissile plutonium enrichment of 9.3 wt %, twenty one fuel rods with fissile plutonium enrichment of 6.5 wt %, one fuel rod with fissile plutonium enrichment of 3.0 wt %, two fuel rods with fissile plutonium enrichment of 5.5 wt %, four partial length rods with fissile plutonium enrichment of 8.0 wt %, and four partial length fuel rods with fissile plutonium enrichment of 9.3 wt %.

8 . The fuel assembly according to claim 4 , wherein
the fuel assembly includes a nine-row by nine-column fuel grid array, and the first fuel rod includes thirty two fuel rods with fissile plutonium enrichment of 10.9 wt %, twenty fuel rods with fissile plutonium enrichment of 7.5 wt %, one fuel rod with fissile plutonium enrichment of 2.5 wt %, three partial length fuel rods with fissile plutonium enrichment of 10.0 wt %, and four partial length fuel rods with fissile plutonium enrichment of 10.9 wt %.

9 . The fuel assembly according to claim 4 , wherein
the fuel assembly includes a ten-row by ten-column fuel grid array, and the first fuel rod includes forty fuel rods with fissile plutonium enrichment of 9.3 wt %, twenty four fuel rods with fissile plutonium enrichment of 6.5 wt %, one fuel rod with fissile plutonium enrichment of 3.0 wt %, two fuel rods with fissile plutonium enrichment of 5.5 wt %, eight partial length rods with fissile plutonium enrichment of 8.0 wt %, and six partial length fuel rods with fissile plutonium enrichment of 9.3 wt %.

10 . A reactor of a nuclear reactor loaded with a plurality of fuel assemblies,
the fuel assembly comprising: at least, a first fuel rod containing plutonium and not containing burnable poison; a second fuel rod containing uranium and burnable poison and not containing plutonium; a water rod; and a channel box having a rectangular shape in horizontal section and accommodating the first fuel rod, the second fuel rod, and the water rod in a bundle, wherein the second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in the horizontal section, N2<N1 (N2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged on the outermost periphery is N1 and the number of the second fuel rods arranged adjacent to the water rod is N2, and W2<N2+W0<W1 (W2 is a positive integer including zero) is satisfied where the number of the second fuel rods arranged without being vertically and/or horizontally adjacent to each other in the horizontal section is W0, the number of the second fuel rods arranged vertically and/or horizontally adjacent to only one second fuel rod in the horizontal section is W1, and the number of the second fuel rods arranged vertically and/or horizontally adjacent to two second fuel rods in the horizontal section is W2, of the second fuel rods arranged on the outermost periphery.

11 . The reactor according to claim 10 , wherein
average fissile plutonium enrichment in the horizontal section is 4.0% or more.

12 . The reactor according to claim 11 , wherein
the second fuel rod arranged vertically and/or horizontally adjacent to two second fuel rods in the horizontal section is arranged at a corner portion of the channel box.

13 . The reactor according to claim 11 , wherein
the burnable poison contained in the second fuel rod is gadolinium.

14 . The reactor according to claim 12 , wherein
the burnable poison contained in the second fuel rod is gadolinium.

Assignees

• Hitachi Ltd

Inventors

• Mitsuyasu Takeshi
• Aoyama Motoo

Classifications

• G21C3/326

  comprising fuel elements of different composition; comprising, in addition to the fuel elements, other pin-, rod-, or tube-shaped elements, e.g. control rods, grid support rods, fertile rods, poison rods or dummy rods · CPC title

• G21C1/084

  Boiling water reactors · CPC title

• G21C3/623

  Oxide fuels · CPC title

• G21C3/328 Primary

  Relative disposition of the elements in the bundle lattice · CPC title

• G21C7/04

  of burnable poisons (burnable poisons in fuel rods G21C3/326) · CPC title