US-12624708-B2 - Jet pump clamps and methods for use in a nuclear reactor jet pump

Abstract

Jet pump clamps fit to modified jet pump assemblies at the riser pipe-restrainer bracket junction. The clamp can secure the restrainer bracket and riser pipe, relieving any welds between the same stress in the same, while preventing the restrainer bracket from moving. The clamp may include multiple members on either side of the restrainer bracket that fit into surfaces of the riser pipe. When these members are drawn together through clamping action, the underlying riser pipe is compressed. Similarly, vertically-adjustable members may seat into and/or through the restrainer bracket to hold the bracket steady. Jet pump assemblies may be prepared by forming grooves in the riser pipe and hole(s) in the restrainer bracket(s) and spherical indentations about the same. Clamps may then be installed on the grooves and through the hole(s) at installation or during a maintenance outage in a commercial nuclear power plant.

Inventors

• Kayla R. KELLEY
• Mark Sumner
• Jack T. Matsumoto
• Christopher M. Welsh
• James SCAVO

Assignees

• GE-HITACHI NUCLEAR ENERGY AMERICAS LLC

Dates

Publication Date

20260512

Application Date

20231127

Claims (19)

1. 1 . A clamp for a jet pump assembly in a nuclear reactor, the clamp comprising: an upper clamp member having an inner surface shaped to fit around a riser pipe of the jet pump assembly, wherein the inner surface of the upper clamp member includes a tongue extending from the inner surface of the upper clamp member and configured to fit in a first groove of the riser pipe so as to prevent vertical movement of the upper clamp member relative to the riser pipe; a lower clamp member having an inner surface shaped to fit around the riser pipe of the jet pump assembly, wherein the inner surface of the lower clamp member includes a tongue extending from the inner surface of the lower clamp member and configured to fit in a second groove of the riser pipe so as to prevent vertical movement of the lower clamp member relative to the riser pipe; and a vertical connection between the upper clamp member and the lower clamp member configured to draw the upper clamp member and the lower clamp member vertically together.
2. 2 . The clamp of claim 1 , further comprising: a constraint configured to vertically pass through a restrainer bracket of the jet pump assembly between the upper clamp member and the lower clamp member.
3. 3 . The clamp of claim 2 , wherein the constraint includes a draw bolt passing vertically and entirely through the upper clamp member and the lower clamp member.
4. 4 . The clamp of claim 3 , wherein the constraint includes two vertically-adjustable bushings on the draw bolt between the upper clamp member and the lower clamp member, wherein the bushings are configured to seat on the restrainer bracket.
5. 5 . The clamp of claim 3 , wherein the constraint includes a crimp nut on the draw bolt configured to vertically tighten the draw bolt and lock the draw bolt relative to the upper clamp member and the lower clamp member by deformation.
6. 6 . The clamp of claim 1 , wherein the vertical connection includes a draw bolt passing vertically and entirely through the upper clamp member and the lower clamp member.
7. 7 . The clamp of claim 6 , wherein the vertical connection includes a crimp nut on the draw bolt configured to vertically tighten the draw bolt and lock the draw bolt relative to the upper clamp member and the lower clamp member by deformation.
8. 8 . The clamp of claim 1 , further comprising: three of the vertical connections, wherein all of the vertical connections are equally spaced about a perimeter of the clamp.
9. 9 . The clamp of claim 1 , wherein the upper clamp member, the lower clamp member, and the vertical connection are fabricated entirely of at least one of a stainless steel alloy, a zirconium alloy, and an aluminum alloy.
10. 10 . A repaired jet pump assembly in a nuclear reactor, the assembly comprising: a riser pipe configured to convey a fluid coolant vertically upward; two inlet mixers each at a different side of the riser pipe from one another and configured to convey the fluid coolant vertically downward; a restrainer bracket connected to the riser pipe and one of the two inlet mixers; and a clamp on the riser pipe and passing through the restrainer bracket to prevent relative movement of the riser pipe and the restrainer bracket, wherein the clamp compresses the riser pipe in the vertical direction, wherein the clamp seats into two grooves in an outer surface of the riser pipe, and wherein the clamp compresses the riser pipe by vertically compressing the two grooves together.
11. 11 . The repaired jet pump assembly of claim 10 , wherein the clamp passes through two entirely separate holes of the restrainer bracket.
12. 12 . The repaired jet pump assembly of claim 10 , wherein the clamp includes a constraint configured to pass through the restrainer bracket, wherein the constraint includes a draw bolt passing vertically and entirely through the restrainer bracket and a body of the clamp vertically above and below the restrainer bracket.
13. 13 . The repaired jet pump assembly of claim 12 , wherein the constraint includes a crimp nut on the draw bolt configured to vertically tighten the draw bolt and lock the draw bolt relative to the upper clamp member and the lower clamp member by deformation.
14. 14 . The repaired jet pump assembly of claim 12 , wherein the constraint includes two vertically-adjustable bushings on the draw bolt between upper and lower ends of the clamp, wherein the bushings are seated against sides of the restrainer bracket.
15. 15 . A method of preparing a jet pump assembly having a restrainer bracket for use in a nuclear reactor with a jet pump clamp, the method comprising: forming at least one groove in an outer surface of a riser pipe of the jet pump assembly above a restrainer bracket-riser pipe junction point; forming at least one groove in the outer surface of the riser pipe below the restrainer bracket-riser pipe junction point; and forming at least one hole passing vertically through the restrainer bracket of the jet pump assembly.
16. 16 . The method of claim 15 , wherein the formings include electrical discharge machining the grooves and the hole.
17. 17 . The method of claim 16 , wherein the formings are performed during a maintenance outage of the nuclear reactor and after the nuclear reactor has commercially generated electricity.
18. 18 . The method of claim 15 , further comprising: installing a clamp on the riser pipe and the restrainer bracket to prevent relative movement of the riser pipe and the restrainer bracket, wherein the clamp compresses the at least one groove in the outer surface of the riser pipe below the restrainer bracket and the at least one groove in the outer surface of the riser pipe above the retainer bracket together.
19. 19 . The method of claim 18 , wherein the installing includes passing a constraint of the clamp through the at least one hole in the restrainer bracket.

Description

RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Application 63/427,993, filed Nov. 25, 2022 and incorporated by reference herein in its entirety. BACKGROUND FIG. 1A is a front view of a related art nuclear boiling water reactor (BWR) jet pump assembly 8. The major components of jet pump assembly 8 include riser pipe 3 and two inlet mixers 4 that insert into respective diffusers 2. Shroud support plate 1 receives fluid from diffusers 2 and supports the same, allowing jet-pump driven fluid flow through an annulus housing jet pump assembly 8. Jet pump restrainer brackets 5 are welded to riser pipe 3 to stabilize movement of inlet mixers 4 and reduce movement of and leakage at the slip joint that exists at the interface between inlet mixers 4 and diffusers 2. Restrainer brackets 5 minimize relative movement between inlet mixers 4 and restrainer brackets 5 to minimize leakage or damage around the slip joint. FIG. 1B is a top view of jet pump restrainer brackets 5 as viewed from line B-B of FIG. 1A. As seen in FIG. 1B, each bracket 5 may be welded directly to opposite sides of an outer perimeter of riser pipe 3. One or more guide ears 6 and/or other alignment structures may ensure that inlet mixer 4 and diffuser 2 properly align and/or remain confined by corresponding bracket 5. G. L. STEVENS et al, “Jet Pump Flaw Evaluation Procedures” 8th International Conference on Nuclear Engineering, January 2000, and G. SOTO-MENDOZA et al., “Cross Flow Analysis over the Jet Pumps of a BWR-5 Reactor” Science and Technology of Nuclear Installations, Vol. 2021, Mar. 27, 2021, describe other related art jet pump assembly operations and are incorporated by reference herein in their entireties. This background provides a useful baseline or starting point from which to better understand some example embodiments discussed below. Except for any clearly-identified third-party subject matter, likely separately submitted, this Background and any figures are by the Inventor(s), created for purposes of this application. Nothing in this application is necessarily known or represented as prior art. SUMMARY Example embodiments include jet pump clamps, modified jet pump assemblies accommodating the same, and methods of forming and installing such clamps and assemblies in a nuclear reactor. Example embodiment clamps are installable on the riser pipe and restrainer bracket joined to the riser pipe. The clamp can wholly replace welds and other connections between the restrainer bracket and riser pipe, relieving stress in the same and holding the bracket and riser pipe in secured orientations. Clamps can also compress the riser pipe inside the clamp, relieving vertical strains on the pipe that may cause crack propagation. Example embodiment jet pump assemblies may include indentations in an outer surface of the riser pipe that receives portions of the clamp and vertically secures the pipe and clamp. Different members of the clamp may be drawn together to push the pipe together vertically, providing the vertical compression through these indentations. The assemblies may further include restrainer brackets at the clamps with one or more vertical holes through which the clamp can pass and seat. Example embodiment clamps may include holding members that can be adjusted vertically to meet the restrainer bracket and seat onto either side of the holes in the same. This may secure the restrainer bracket and riser pipe in all directions. Example embodiment clamps may tighten and hold through a variety of structures, including adjustable draw bolts passing through all structures that can be tightened with threaded crimp nuts. The draw bolts and any other biasing structure may seat against the clamp body and restrainer bracket with washers that match a surface of the body and bracket, including partially spherical surfaces. Example methods may prepare jet pump assemblies and/or install clamp components on the same. Example methods can be performed at any time, during jet pump assembly fabrication, installation, or maintenance outage. Grooves in the riser pipe and hole(s) in the restrainer bracket(s), as well as surfaces about the same, may be formed through any shaping process, including forging and machining. Clamps may then be installed on the grooves and through the hole(s) in any manner, and eventually biased to impart internal compression on the riser pipe about the restrainer bracket, while holding the bracket and riser pipe immovable relative to each other. BRIEF DESCRIPTIONS OF THE DRAWINGS Example embodiments will become more apparent by describing, in detail, the attached drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus do not limit the terms which they depict. FIG. 1A is an illustration of a related art jet pump assembly for use in a nuclear power plant. FIG. 1B is a detail of the related art jet pump assembly of FIG. 1