Methods and devices to improve performances of RCCA and CEA to mitigate clad strain in the high fluence region

Patent metadata

Field	Value
Publication number	US-12046381-B2
Application number	US-202117353016-A
Country	US
Kind code	B2
Filing date	Jun 21, 2021
Priority date	Jun 21, 2021
Publication date	Jul 23, 2024
Grant date	Jul 23, 2024

Abstract

The present disclosure is generally related to methods, devices and systems for improving the performances of a Rod Cluster Control Assembly (RCCA) and/or a Control Element Assembly (CEA) to mitigate clad strain, especially in the high fluence region, during normal operation conditions and accident conditions. One method may include incorporating a device such as a powder collection and blockage device between the ceramic upper and ceramic lower absorber materials of the RCCA and/or CEA. Another method may include increasing the plenum volume by incorporating an axial hole into the top end plug extension. Another method may include increasing the plenum volume by incorporating an axial hole into the bottom end plug and optionally incorporating radial grooves in the bottom of the lower absorber material to provide a flow channel for gas expansion or generation to ensure that the lower absorber does not block the opening in the bottom end plug.

First claim

What is claimed is:

1. A Rod Cluster Control Assembly (RCCA) for mitigating clad strain, the RCCA comprising:
a control rod comprising:
a clad tube comprising an upper section and a lower section, wherein the clad tube defines an inner wall;
an upper absorber material housed inside the upper section of the clad tube; and
a lower absorber material housed inside the lower section of the clad tube;
wherein the control rod is configured to have a first annular gap between the upper absorber material and the inner wall of the clad tube and a second annular gap between the lower absorber material and the inner wall of the clad tube; and

a device positioned inside the clad tube between the upper absorber material and the lower absorber material, the device comprising:
a garter spring configured to exert an outward force against the inner wall of the clad tube, wherein the garter spring comprises coils configured to prevent powder generated from the upper absorber material from passing to the lower section of the clad tube, and wherein the coils are further configured to allow gases to pass between the upper section of the clad tube and the lower section of the clad tube; and
a spacer configured to retain the garter spring, wherein the spacer is further configured to provide a bearing surface for the upper absorber material, and wherein the spacer defines axial openings for collecting the powder generated by the upper absorber material.

2. The RCCA of claim 1 , wherein the upper absorber material is a ceramic absorber material.

3. The RCCA of claim 1 , wherein the upper absorber material is boron carbide (B 4 C).

4. The RCCA of claim 1 , wherein the lower absorber material is a ceramic absorber material.

5. The RCCA of claim 1 , wherein the lower absorber material is boron carbide (B 4 C).

6. The RCCA of claim 1 , wherein the spacer comprises at least one of 304 stainless steel, a nickel based alloy, Inconel 625, Inconel 718, a ceramic absorber material, or B 4 C absorber material.

7. The RCCA of claim 1 , wherein the garter spring comprises at least one of 304 stainless steel, a nickel based alloy, Inconel 625, or Inconel 718.

8. The RCCA of claim 1 , further comprising a plurality of the devices, wherein each of the devices are positioned inside the clad tube.

9. The RCCA of claim 8 , wherein the devices are distributed along an axial length of the clad tube.

10. The RCCA of claim 1 , wherein the first annular gap comprises a first gap width, wherein the second annular gap comprises a second gap width, and wherein the first gap width is the same as the second gap width.

11. The RCCA of claim 1 , wherein the control rod further comprises a spring positioned inside the upper section of the clad tube above the upper absorber material, wherein the spring forms a plenum above the upper absorber material, wherein the plenum comprises a plenum volume, wherein the RCCA further comprises a top end plug extension configured to attach to an upper end of the upper section of the clad tube and wherein the top end plug comprises an axial hole configured to increase the plenum volume.

12. The RCCA of claim 1 , wherein the control rod further comprises a plenum region formed inside of the lower section of clad tube and around the lower absorber material, wherein the plenum region has a plenum volume; wherein the RCCA further comprises a bottom end plug configured to attach to a lower end of the lower section of the clad tube, and wherein the bottom end plug comprises an axial hole configured to increase the plenum volume.

13. The Rod Cluster Control Assembly (RCCA) of claim 12 , wherein a portion of the lower absorber material proximate to the end of the lower section of the clad tube comprises radial grooves formed therein, wherein the radial grooves are configured to allow gas to flow into the axial hole.

14. The Rod Cluster Control Assembly (RCCA) of claim 12 , further comprising a top end plug extension configured to attach to an upper end of the upper section of the clad tube, wherein the axial hole is a first axial hole, and wherein the top end plug extension comprises a second axial hole configured to increase the plenum volume.

15. The RCCA of claim 1 , wherein the axial openings comprise circumferentially spaced openings, and wherein the spacer comprises spoked projections defining the circumferentially spaced openings.

16. The RCCA of claim 15 , wherein the spacer comprises an upper disc, a lower disk, and a body extending between the upper disc and the lower disc, wherein the spacer is retained by the garter spring between the upper disc and the lower disc, and wherein the upper disc comprises the circumferentially spaced openings.

17. The RCCA of claim 16 , wherein the device further comprises a screen mesh positioned on top of the garter spring, and wherein the screen mesh is configured to prevent the powder generated from the upper absorber material from passing to the lower section of the clad tube.

18. The RCCA of claim 17 , wherein the screen mesh comprises at least one of 304 stainless steel, a nickel based alloy, Inconel 625, or Inconel 718.

19. A control rod comprising:
a clad tube comprising an upper section and a lower section, wherein the clad tube defines an inner wall;
an upper absorber material housed inside the upper section of the clad tube; and
a lower absorber material housed inside the lower section of the clad tube, wherein the control rod is configured to have a first annular gap between the upper absorber material and the inner wall of the clad tube and a second annular gap between the lower absorber material and the inner wall of the clad tube;
a spacer positioned inside the clad tube between the upper absorber material and the lower absorber material, the spacer comprising:
an upper disc, wherein the upper disc comprises axial openings for collecting powder from the upper absorber material;
a lower disc; and
a body extending between the upper disc and the lower disc; and

a garter spring retained between the upper disc and the lower disc, wherein the garter spring comprises coils configured to prevent the powder collected by the axial openings from passing to the lower section of the clad tube, and wherein the coils are further configured to allow gases to pass between the upper section of the clad tube and the lower section of the clad tube.

20. The control rod of claim 19 , wherein the upper disc comprises spoked projections defining the axial openings.

Assignees

• Westinghouse Electric Co Llc

Inventors

• Mccarty Jeffrey M
• Do Thanh H

Classifications

• G21C7/10

  Construction of control elements · CPC title

• G21C7/103

  Control assemblies containing one or more absorbants as well as other elements, e.g. fuel or moderator elements · CPC title

• Y02E30/30

  Nuclear fission reactors · CPC title

• G21C21/18

  Manufacture of control elements covered by group G21C7/00 · CPC title

• G21C7/117 Primary

  Clusters of control rods; Spider construction · CPC title