Fuel assembly and nuclear reactor core

Patent metadata

Field	Value
Publication number	US-2024404715-A1
Application number	US-202418663145-A
Country	US
Kind code	A1
Filing date	May 14, 2024
Priority date	May 30, 2023
Publication date	Dec 5, 2024
Grant date	—

Abstract

A fuel assembly includes: a square cylinder channel box having a square cross-section; and fuel rods disposed in a square lattice shape and filled with a nuclear fuel material. The fuel rods includes: a first rod disposed in an outer layer in the box and a second rod disposed in an inner layer in the box and having a larger diameter than the first rod. An absolute value of a difference between a hydraulic equivalent diameter around the first rod and a hydraulic equivalent diameter between a surface in the box and the first rod is more than or equal to a value obtained by multiplying an absolute value of a difference between the hydraulic equivalent diameter around the first rod and the hydraulic equivalent diameter around the second rod by a ratio of a cross-sectional area of the inner layer to a cross-sectional area of the entire box.

First claim

What is claimed is:

1 . A fuel assembly comprising:
a channel box that is a square cylinder having a square cross section, and a plurality of fuel rods disposed in a square lattice shape in the channel box, and filled with a nuclear fuel material inside, the plurality of fuel rods including: a first fuel rod disposed in an outer layer portion in the channel box; and a second fuel rod that is disposed in an inner layer portion in the channel box and has a diameter larger than the first fuel rod, wherein an absolute value of a difference between a hydraulic equivalent diameter around the first fuel rod and a hydraulic equivalent diameter between a wall surface in the channel box and the first fuel rod is more than or equal to a value obtained by multiplying an absolute value of a difference between the hydraulic equivalent diameter around the first fuel rod and a hydraulic equivalent diameter around the second fuel rod by a ratio of a cross-sectional area of the inner layer portion of the channel box to a cross-sectional area of the entire channel box.

2 . The fuel assembly according to claim 1 , wherein a volume of a nuclear fuel material disposed in the fuel assembly is equal to or larger than a volume of a nuclear fuel material when the first fuel rods are disposed in a square lattice shape in the channel box.

3 . The fuel assembly according to claim 1 , wherein a third fuel rod having a larger diameter than the second fuel rod is disposed in a further inner layer of a region in which the second fuel rod is disposed, and an absolute value of a difference between a hydraulic equivalent diameter around the second fuel rod and a hydraulic equivalent diameter between the first fuel rod and the second fuel rod is more than or equal to a value obtained by multiplying an absolute value of a difference between a hydraulic equivalent diameter around the third fuel rod and a hydraulic equivalent diameter around the second fuel rod by a ratio of a flow path area of a region in which the third fuel rod is disposed to a flow path area of a region in which the second fuel rod and the third fuel rod are disposed.

4 . The fuel assembly according to claim 1 , wherein the first fuel rods are disposed in 12 rows and 12 columns in the channel box.

5 . The fuel assembly according to claim 1 , wherein a lower end portion is supported by a lower fuel support member, an upper end portion is supported by an upper fuel support member, a fuel spacer that bundles the plurality of fuel rods is held, and a support rod without containing a fuel material is disposed at each of four corners of an outermost peripheral region of a fuel rod disposition in a cross section of the fuel assembly.

6 . A nuclear reactor core, wherein a plurality of the fuel assemblies according to claim 1 are loaded.

Assignees

• Hitachi Ltd

Inventors

• Narushima Yuki
• Mitsuyasu Takeshi
• Hino Tetsushi

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

• G21C5/16

  Shape of its constituent parts · CPC title

• G21C3/328 Primary

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

• G21C3/332 Primary

  Supports for spacer grids · CPC title

• Y02E30/30

  Nuclear fission reactors · CPC title