Westinghouse Electric Corporation

Lawrence A Nelson

Robert F Keating

James W Everett

George D Fulmer

George G Elder

Leonard F Ermold

John B Gunter

Susanta Sinha

Frank Sadofsky

William Woolfolk

Pedro C Olivera

Method and joint for sealing a bare hole in a nuclear heat exchanger tubesheet. The tubesheet has a plurality of holes formed therethrough, wherein at least one of the holes has been left vacant by a heat transfer tube removed from the hole. Such a hole is defined as a bare hole. One embodiment of the method of the invention comprises disposing a sleeve in the bare hole to protect the tubesheet material from the corrosive attack of the heat exchanger primary coolant and sealingly disposing a sleeve plug in the sleeve in order to seal the sleeve. A leak-tight joint is defined as the sleeve plug is sealingly disposed in the sleeve.

Method for sealing a bare hole defined by a nuclear heat exchanger

An improved, easily removable plug for plugging the open end of a heat exchanger tube in a nuclear steam generator is disclosed herein. The plug generally comprises a cylindrical shell of Inconel.RTM. having tapered side walls, a closed end, an open end, a cork-shaped expander element disposed within the shell that radially expands the tapered side walls of the shell into sealing engagement with the inner walls of a tube when axially drawn from the closed to the open end of the shell, and a wall section in the interior of the shell between the closed end and the tapered side walls for receiving the expander element when this element is pushed back from the open end of the shell back against the closed end thereof, thereby affording clear mechanical access to the interior of the tapered side walls of the shell. The improved plug is particularly adapted for use with a plug removal system that includes an expander remover that axially pushes the expander element backward against the closed end of the shell, a TIG torch for creating axially oriented weld beads within the interior of the tapered side walls of the shell in order to contract these side walls and to relax the engagement between the plug and the heat exchanger tube, and a plug puller that pulls the plug from the tube.

System for removing a plug from a heat exchanger tube

A method of controlling leakage through degraded heat exchanger tubes in the tubesheet region of a nuclear steam generator is disclosed herein. The method comprises radially expanding a section of the heat exchanger tube disposed within the bore of the tubesheet into leak resistant engagement so that the resultant leakage flow is equal to or less than an acceptable leakage flow rate. The expanded, leak resistant section is located above the degraded section of the heat exchanger tube and below the upper side of the tubesheet. The length L of the leak resistant section and the pressure P necessary to create it are determined by ascertaining a plurality of combinations of length Lx and pressure Px that would result in a sufficiently tight engagement between the heat exchanger tube and the tubesheet bore to achieve the desired leakage flow rate, and by choosing a combination of Lx, Px that results in the smallest length L without exceeding a pressure of 50 ksi (344.7 MPa).

Method for controlling leakage through degraded heat exchanger tubes in

An improved system for removing a plug from the open end of a heat exchanger tube in a nuclear steam generator is disclosed herein. It is particularly adapted for removing a plug formed from an elongated, cylindrical shell of Inconel.RTM. having a closed end, an open ends, and an expander element that radially expands the shell when axially drawn from the clossed to the open end of the shell. The system comprises an expander remover for axially pushing the expander element from the open end completely through the closed end of the plug shell, and a TIG torch for creating beads along the longitudinal axis of the plug shell which relax the engagement between the plug shell and the tube after the weld beams harden. Finally, the system includes a plug puller for pulling the loosened plug from the tube. The expander remover and plug puller maybe remotely operated by means of a robotic arm, and a compliance coupling is provided to facilitate alignment between these tools and the plugged end of a selected heat exchanger tube.

The multi-seal tube plug comprises a substantially cylindrical sheath closed at one end and having a central cavity. An expander is received within the central cavity of the sheath and acts to expand the sheath into contact with the tube. The expander comprises a plurality of radially expandable disks having a central aperture and an expander member adapted to be received within the aperture and to expand the disks. The expanded disks expand a portion of the sheath into contact with the tube to sealingly engage the tube. The expander member is preferably conical and interacts with the conical inner surfaces of the disks. An alternate embodiment of the multi-seal tube plug uses conical washers rather than radially expandable flat disks. All embodiments of the multi-seal tube plug are easily removable and do not damage the tube.

Multi-seal mechanical tube plug

The tube plug comprises a substantially cylindrical sheath closed at one end and having a relatively smooth outer surface and a central cavity. An expandable shell is received within the central cavity of the sheath. An expander member is adapted to expand the shell from within by being axially translated within the shell, the expander member also being adapted to grip the inner surface of the shell to retain the expander member in the expanded position. The outside surface of the shell is preferably provided with a plurality of lands. A second embodiment of the tube plug comprises a sleeve, a closed shell member adapted to be inserted within the sleeve, and an expander member contained within the shell. Upon axial translation of the expander member within the shell, the shell is expanded into contact with the sleeve and the sleeve is expanded into contact with the tube, thereby sealing the tube.

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Penn Township Westmoreland County, PA, United States of America

Lawrence A Nelson