Method of installing an external dashpot tube around a control rod guide tube in a nuclear fuel assembly

Patent metadata

Field	Value
Publication number	US-11289211-B2
Application number	US-201916558510-A
Country	US
Kind code	B2
Filing date	Sep 3, 2019
Priority date	Jan 12, 2017
Publication date	Mar 29, 2022
Grant date	Mar 29, 2022

Abstract

Methods of installing an external dashpot tube around a control rod guide tube in a nuclear reactor fuel assembly are disclosed herein. The nuclear reactor fuel assembly may include a top nozzle, a bottom nozzle, and a plurality of grids. The various methods may comprise inserting a guide tube into a skeleton of the nuclear reactor fuel assembly to a lower middle grid, the lower middle grid being second closest grid to the bottom nozzle of the plurality of grids. The various methods may also include installing an external dashpot tube over the guide tube after it has been inserted to the lower middle grid; inserting the guide tube with the installed external dashpot tube to the bottom nozzle; attaching the guide tube to the skeleton; and bulging the guide tube onto the external dashpot tube.

First claim

What is claimed is:

1. A method of installing a control rod guide assembly in a nuclear reactor fuel assembly including a top nozzle, a bottom nozzle, and a plurality of grids arranged between the top nozzle and the bottom nozzle, the method comprising:
providing a guide tube and an external dashpot tube;
inserting the guide tube into a skeleton of the nuclear reactor fuel assembly to a lower middle grid, the lower middle grid being a grid of the plurality of grids that is the second closest grid to the bottom nozzle;
after the guide tube is inserted to the lower middle gird, installing the external dashpot tube over the guide tube;
after the external dashpot tube is installed over the guide tube, inserting the guide tube into the skeleton to the bottom nozzle;
attaching the guide tube to the skeleton; and
bulging the guide tube onto the external dashpot tube;
wherein the guide tube comprises an upper portion having a first external radius, a lower portion having a second external radius less than the first external radius, and a transition portion disposed between the upper and lower portion;
wherein the guide tube linearly transitions between the first external radius and the second external radius in the transition portion;
wherein the guide tube is monolithic through the first portion, the second portion, and the transition portion;
wherein the plurality of grids comprise a bottom grid that is the closest grid to the bottom nozzle; and
wherein, after bulging the guide tube onto the external dashpot tube, the external dashpot tube is disposed around a portion of the guide tube in an area beginning at the bottom grid and extending toward the top nozzle.

2. The method of claim 1 , wherein installing the external dashpot tube over the guide tube includes installing the external dashpot tube over the lower portion of the guide tube.

3. The method of claim 1 , wherein the bulging the guide tube onto the external dashpot tube includes forming a first bulge in upper halves of the guide tube and the external dashpot tube and forming a second bulge in lower halves of the guide tube and external dashpot tube.

4. The method of claim 1 , wherein the external dashpot tube includes at least one weep hole formed therein.

5. The method of claim 4 , wherein the at least one weep hole includes a first weep hole and a second weep hole, and wherein the first weep hole is formed in an upper half of the external dashpot tube and the second weep hole is formed in a lower half of the external dashpot tube.

6. The method of claim 3 , wherein the external dashpot tube includes at least one weep hole formed therein, and wherein the at least one weep hole is formed between the first and second bulges in the external dashpot tube.

7. The method of claim 1 , wherein, after bulging the guide tube onto the external dashpot tube, the external dashpot tube extending from the bottom grid towards the top nozzle and ends before reaching the lower middle grid.

8. The method of claim 2 , wherein the lower portion of the guide tube is substantially cylindrical and the external dashpot tube is substantially cylindrical.

Assignees

• Westinghouse Electric Co Llc

Inventors

• Aleshin Yuriy
• Millare Brian
• Bausch Michael O
• Lunde Carter Eliot

Classifications

• G21C3/326 Primary

  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

• G21C7/20

  Disposition of shock-absorbing devices (shock-absorbers in general F16F ){; Braking arrangements} · CPC title

• G21C9/02

  Means for effecting very rapid reduction of the reactivity factor under fault conditions, e.g. reactor fuse; {Control elements having arrangements activated in an emergency}(control elements per se G21C7/00) · CPC title

• G21C3/3305

  Lower nozzle · CPC title

• G21C3/322

  Means to influence the coolant flow through or around the bundles · CPC title