Nuclear fuel assembly support feature

Patent metadata

Field	Value
Publication number	US-2016180972-A1
Application number	US-201514715646-A
Country	US
Kind code	A1
Filing date	May 19, 2015
Priority date	Dec 23, 2014
Publication date	Jun 23, 2016
Grant date	—

Abstract

A nuclear fuel assembly having lateral support provided by a bimetallic spring that extends from a side of the fuel assembly under certain core conditions to pressure against an adjacent component and withdraws under other core conditions, such as shutdown, to enable the nuclear fuel assembly to be aligned or withdrawn from the core and repositioned.

First claim

What is claimed is:

1 . A nuclear fuel assembly having an elongated dimension and comprising:
a plurality of interconnected components wherein at least some of the interconnected components comprise: a top nozzle; a bottom nozzle; a plurality of guide thimbles extending between the top nozzle and the bottom nozzle; and a plurality of grids arranged in a tandem spaced relationship that extends between the top nozzle and the bottom nozzle along the elongated dimension, with each of the having a plurality of cells some of which support fuel rods and others through which the guide thimbles respectively pass and attach to the grid; wherein at least some of the interconnected components have a peripheral surface area that extends in a plane a distance along the elongated dimension; and wherein one of the at least some of the interconnected components has a bimetallic spring that moves between a first and second position relative to the plane as the fuel assembly transitions in a reactor core from a shutdown temperature to an operating temperature, with one of the first and second positions placing the bimetallic spring in contact with an adjoining component of the reactor core.

2 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is on at least one of the plurality of grids.

3 . The nuclear fuel assembly of claim 2 wherein the bimetallic springs has an elongated dimension and the elongated dimension of the metallic spring extends transverse to the elongated dimension of the nuclear fuel assembly.

4 . The nuclear fuel assembly of claim 3 wherein the metallic spring is continuous and extends across several of the grid cells.

5 . The nuclear fuel assembly of claim 2 wherein the at least one of the plurality of grids is a mid-grid.

6 . The nuclear fuel assembly of claim 2 wherein the at least one of the plurality of grids is one of an upper grid or a lower grid or both an upper grid and a lower grid.

7 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is formed in a round disc shape.

8 . The nuclear fuel assembly of claim 7 including relief holes spaced around the disc shape.

9 . The nuclear fuel assembly of claim 7 wherein the bimetallic spring is provided proximate one corner of the one of the at least some of the interconnected components.

10 . The nuclear fuel assembly of claim 9 wherein a tip of the disc shape fits in a recess in a side of the adjoining component.

11 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is formed in a rectangular shape having an elongated dimension.

12 . The nuclear fuel assembly of claim 11 wherein the elongated dimension of the bimetallic spring extends substantially parallel to the elongated dimension of the nuclear fuel assembly.

13 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is formed on at least one of the top nozzle and the bottom nozzle.

14 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is formed from FeNi36 or 64FeNi and stainless steel.

15 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is formed by coating a base metal with a low-to negative coefficient of thermal expansion material.

16 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring is formed on a corner of at least one of the plurality of grids.

17 . The nuclear fuel assembly of claim 14 wherein the bimetallic spring is formed on each corner of the at least one of the plurality of grids.

18 . The nuclear fuel assembly of claim 1 wherein the bimetallic spring does not extend substantially out of the plane at temperatures substantially below a nuclear reactor operating temperature and protrudes outwardly from the nuclear fuel assembly at operating temperatures of the nuclear reactor to an extent to contact the adjoining component of the core of the nuclear reactor.

19 . A nuclear reactor having a reactive core comprising a plurality of fuel assemblies, each having an elongated dimension and comprising:
a plurality of interconnected components wherein at least some of the interconnected components comprise: a top nozzle; a bottom nozzle; a plurality of guide thimbles extending between the top nozzle and the bottom nozzle; and a plurality of grids arranged in a tandem spaced relationship that extends between the top nozzle and the bottom nozzle along the elongated dimension, with each of the grids having a plurality of cells some of which support fuel rods and others through which the guide thimbles respectively pass and attach to the grid; wherein at least some of the interconnected components have a peripheral surface area that extends in a plane a distance along the elongated dimension; and wherein on some but not all of the fuel assemblies one of the at least some of the interconnected components has a bimetallic spring that does not extend substantially out of the plane at temperatures substantially below a nuclear reactor operating temperature and protrudes outwardly from the nuclear fuel assembly at operating temperatures of the nuclear reactor to an extent to contact an adjoining component of a core of the nuclear reactor.

20 . The nuclear reactor of claim 19 wherein the bimetallic spring does not extend substantially out of the plane at temperatures substantially below a nuclear reactor operating temperature and protrudes outwardly from the nuclear fuel assembly at operating temperatures of the nuclear reactor to an extent to contact the adjoining component of the core of the nuclear reactor.

Assignees

• Westinghouse Electric Corp

Inventors

• Payne Nathan J
• Mccarty Jeffrey M

Classifications

• G21C3/3563 Primary

  Supporting members formed only by deformations in the strips · CPC title

• G21C3/3315

  Upper nozzle · CPC title

• G21C3/30 Primary

  Assemblies of a number of fuel elements in the form of a rigid unit · CPC title

• G21C3/33

  Supporting or hanging of elements in the bundle (spacer grids G21C3/34); Means forming part of the bundle for inserting it into, or removing it from, the core; Means for coupling adjacent bundles · CPC title

• G21C3/34 Primary

  Spacer grids · CPC title