BACKGROUND

Field

The present disclosure relates to a method and apparatus for repairing a jet pump slip joint.

Description of Related Art

Boiling water reactors may include jet pumps having a slip joint feature in which flow through the pump is able to leak out of the slip joint. Leakage is limited to clearances between an inlet mixer and a diffuser. Leakage may result in leakage flow induced vibration, which leads to wear and degradation of the jet pump.

SUMMARY

At least one example embodiment relates to a method of repairing a jet pump slip joint.

In at least one example embodiment, a method of repairing a jet pump slip joint includes removing an inlet mixer from a bore of a diffuser, machining an inner surface of the bore of the diffuser so as to remove damaged metal and form a substantially smooth inner surface, machining an outer surface of the inlet mixer so as to remove damaged metal from the inlet mixer and form a substantially smooth outer surface, and inserting a bushing in the bore of the diffuser. The bushing includes a grooved flange on an upper surface. The grooved flange is configured to receive a gripping portion of a clamp. The bushing includes an internal groove on an inner, bottom surface of the bushing. A seal is inserted in the internal groove of the bushing.

In at least one example embodiment, the method may also include inserting the inlet mixer through the bushing and into the bore of the diffuser. The method may also include clamping the bushing to a collar of the diffuser such that the seal is compressed. The method may also include inserting the gripping portion of the clamp in the grooved flange of the upper surface of the bushing, and securing a gripping collar to the collar of the diffuser.

In at least one example embodiment, the method may also include mounting a slip joint clamp around the bushing, the diffuser, and the inlet mixer.

At least one example embodiment relates to a jet pump slip joint repair assembly.

In at least one example embodiment, a jet pump slip joint repair assembly includes at least one clamp and a bushing configured to be inserted in a bore of a diffuser and to surround a portion of an inlet mixer. The clamp includes a gripping surface and a gripping collar. The bushing includes a generally cylindrical sidewall. The sidewall is configured to surround the portion of the inlet mixer. The bushing also includes a grooved flange on an upper surface of the sidewall. The grooved flange is configured to receive the gripping surface of the clamp. At least one cutout is between adjacent portions of the grooved flange. The at least one cutout is configured to receive at least one portion of a slip joint clamp. The bushing also includes a groove on an inner, bottom surface of the sidewall. The assembly also includes a seal in the groove. The seal is flexible and formed of a metallic material. The seal is configured to be compressed when the at least one clamp engages the bushing.

In at least one example embodiment, the assembly includes at least two clamps. The at least two clamps apply at least about 2,000 pounds force to the bushing. When the bushing is inserted in the bore of the diffuser, a gap is formed between the grooved flange of the bushing and a top edge of the diffuser.

In at least one example embodiment, the gripping surface extends from a gripping body and the gripping body is configured to be inserted in the gripping collar. The gripping body has a generally square-shaped cross-section so as to reduce rotation of the gripping body in relation to the gripping collar. In at least one example embodiment, the gripping body has a generally non-round cross-section so as to reduce rotation of the gripping body in relation to the gripping collar.

At least one example embodiment relates to a jet pump slip joint.

In at least one example embodiment, the jet pump slip joint includes a diffuser including a bore extending therethrough. An inner surface of the bore has a substantially smooth surface. The jet pump slip joint also includes a bushing inserted in the bore. The bushing includes a generally cylindrical sidewall, a grooved flange on an upper surface of the sidewall, at least one cutout between adjacent portions of the grooved flange, and a groove on an inner, bottom surface of the sidewall. The grooved flange is configured to receive the gripping surface of the clamp. The jet pump slip joint also includes a seal inserted in the groove of the bushing, an inlet mixer inserted into the sidewall of the bushing and the bore of the diffuser, and at least one clamp engaged with the diffuser and the bushing. The at least one clamp is configured to compress the seal.

In at least one example embodiment, the seal is formed of a flexible, metallic material.

In at least one example embodiment, the at least one clamp includes a gripping surface and a gripping collar. The gripping surface extends from a gripping body. The gripping body has a generally square-shaped cross-section so as to reduce rotation of the gripping body in relation to the gripping collar.

In at least one example embodiment, the jet pump slip joint may also include a gap between the grooved flange of the bushing and a top edge of the diffuser. The jet pump slip joint may also include a slip joint clamp extending at least partially around the diffuser and the inlet mixer, at least a portion of the slip joint clamp positioned within the at least one cutout of the bushing.

