Patent Number: 
Section: claims

1. A method for sealing an opening extending radially from an outer circumferential surface to an inner circumferential surface of a tubular object in a nuclear power plant, the method comprising:inserting a stopper from outside of the outer circumferential surface through the opening into the tubular object; andactuating a fastener from the outside of the circumferential surface to force the stopper radially outward to seal the opening, wherein the tubular object is part of a feedwater sparger assembly of a nuclear reactor. 2. The method as recited in claim 1 wherein the stopper includes an outer ring having a shape matching a shape of the inner circumferential surface of the tubular object surrounding the opening, the actuating of the fastener forcing the outer ring against the inner circumferential surface of the tubular object surrounding the opening. 3. The method as recited in claim 1 wherein the stopper includes a threaded hole passing therethrough receiving the fastener, the actuating of the fastener including torquing the fastener in the hole. 4. The method as recited in claim 1 wherein the opening has a first length extending between longitudinal edges of the opening and a first width extending between lateral edges of the opening, the first width being less than the first length, the first length defining a maximum perimeter dimension of the opening and the first width defining a minimum perimeter dimension of the opening. 5. The method as recited in claim 4 wherein the stopper has a second length extending between longitudinal edges of the stopper and a second width extending between lateral edges of the stopper, the second width being less than the second length, the second length defining a maximum perimeter dimension of the stopper and the first width defining a minimum perimeter dimension of the stopper, the second length being greater than the first length, the second width being greater than the first width, the second width being less than the first length. 6. The method as recited in claim 5 wherein the inserting of the stopper through the opening includes orienting the stopper widthwise and passing the stopper through the opening such that the lateral edges of the stopper face the longitudinal edges of the stopper as the stopper is inserted through the opening. 7. The method as recited in claim 1 wherein the tubular object has a curved shape such that a center axis of the tubular object follows an arced path while extending longitudinally from a first end to a second end of the tubular object. 8. The method as recited in claim 1 further comprising sliding a strongback onto the fastener before the actuating of the fastener. 9. The method as recited in claim 8 wherein the actuating of the fastener forces surfaces of the strongback against the outer circumferential surface of the tubular object and moving the strongback and the stopper closer together. 10. The method as recited in claim 1 wherein the actuating of the fastener causes the fastener to contact the inner circumferential surface of the tubular object opposite of the opening. 11. The method as recited in claim 10 wherein after the fastener contacts the inner circumferential surface of the tubular object opposite of the opening the fastener is further torqued to compress the fastener between the stopper and the inner circumferential surface of the tubular object opposite of the opening. 12. A method for removing material from an inaccessible region of an enclosure in a nuclear power plant, the method comprising:cutting through a wall of the enclosure to form an opening passing through the wall;removing the material through the opening;inserting a stopper into the enclosure through the opening from outside of the enclosure; and thenactuating a fastener from the outside of the enclosure to force the stopper against the wall to seal the opening. 13. The method as recited in claim 12 wherein the cutting through the wall is performed by electrical discharge machining. 14. The method as recited in claim 12 wherein the enclosure is a tubular object, the stopper including a surface matching an inner circumferential surface of the tubular object, the actuating of the fastener including forcing the surface of the stopper against the inner circumferential surface of the tubular object. 15. The method as recited in claim 12 wherein the stopper includes a threaded hole passing therethrough receiving the fastener, the actuating of the fastener including torquing the fastener in the hole. 16. The method as recited in claim 12 wherein the opening has a first length extending between longitudinal edges of the opening and a first width extending between lateral edges of the opening, the first width being less than the first length, the first length defining a maximum perimeter dimension of the opening and the first width defining a minimum perimeter dimension of the opening, the stopper having a second length extending between longitudinal edges of the stopper and a second width extending between lateral edges of the stopper, the second width being less than the second length, the second length defining a maximum perimeter dimension of the stopper and the first width defining a minimum perimeter dimension of the stopper, the second length being greater than the first length, the second width being greater than the first width, the second width being less than the first length. 17. The method as recited in claim 12 further comprising sliding a strongback onto the fastener before the actuating of the fastener, the actuating of the fastener forcing surfaces of the strongback against an outer circumferential surface of the tubular object and moving the strongback and the stopper closer together. 18. The method as recited in claim 12 wherein the actuating of the fastener causes the fastener to contact an inner circumferential surface of the tubular object opposite of the opening and after the fastener contacts the inner circumferential surface of the tubular object opposite of the opening the fastener being further torqued to compress the fastener between the stopper and the inner circumferential surface of the tubular object opposite of the opening. 19. A mechanical seal assembly for plugging an opening in a tubular object by contacting an inner circumferential surface of the tubular object, the mechanical seal assembly comprising:a stopper configured for insertion into an interior of the tubular object for plugging the opening, the stopper including a surface configured for matching the inner circumferential surface of the tubular object; anda fastener passing through a hole in the stopper such that the fastener is actuatable from outside of the tubular object to force the surface of the stopper against the inner circumferential surface of the tubular object, wherein the tubular object is part of a feedwater sparger assembly of a nuclear reactor and the mechanical seal assembly is configured for use in on the feedwater sparger assembly.