Patent Number: 052020827
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a typical pressurizer 10 used in a nuclear reactor coolant system. Pressurizer 10 is a vertical, cylindrical vessel with replaceable electric heaters 12 in its lower section. Heaters 12 extend through heater sleeves 14 in the vessel wall 16 into the lower portion of pressurizer 10. Heater sleeves 14 extend through the vessel wall 16 which is approximately six inches thick and made of carbon steel or low alloy steel. A plurality of nozzles such as that indicated by the numeral 15 may also extend through a bore in the vessel wall at a variety of locations on the pressurizer. Only one is shown for ease of illustration. As seen in FIG. 2, a cladding 18 normally made from stainless steel is used on the interior surface of the wall 16 for corrosion protection. For ease of illustration, heater 12 is not shown in FIG. 2. For purposes of simplicity, the followng description is directed to the replacement of a heater sleeve. As seen in FIG. 2, the invention is generally indicated by the numeral 20. Replacement heater sleeve 20 is generally comprised of first seal ring 22, sleeve 24, flange 26 on sleeve 24, and means 28 for providing a seal between flange 26 and the exterior surface of pressurizer 10. The following work must be performed before replacement heater sleeve 20 can be installed. The original electric heater 12 and original heater sleeve 14 exterior of pressurizer 10 are removed. A portion of original heater sleeve 14 in heater sleeve bore 30 is removed and heater sleeve bore 30 is partially tapped adjacent the exterior surface of vessel wall 16 to provide threaded area 32. First seal ring 22 is positioned against original heater sleeve 14 inside heater sleeve bore 30. Sleeve 24 is threaded into bore 30 such that the upper end of sleeve 24 presses against first seal ring 22 to create a seal between original heater sleeve 14 and sleeve 24. Sleeve 24 is provided with threads 33 that threadably engage threads 32. It should be understood that reference to upper or lower ends of parts are merely for ease of reference and should not be considered as limiting to the elements of the invention. Sleeve 24 has flange 26 adjacent its lower end and positioned thereon such that flange 26 is located very near the external surface of pressurizer vessel wall 16 when sleeve 24 is in the installed position described above. Means 28 for providing a seal between flange 26 and the exterior of pressurizer 10 is incorporated into flange 26 and is generally comprised of second seal ring 36, disk 38, and jack bolts 40. Disk 38 is slidably received in a groove that extends around the upper end of flange 26. Second seal ring 36 is received in the groove on disk 38. A plurality of jack bolts 40 are threadably received in bores 42 spaced circumferentially around flange 26 (illustrated in FIG. 3). As seen in FIG. 2, each jack bolt 40 extends through bore 42 to bear against disk 38. In this manner, jack bolts 40 may be tightened or threaded into bores 40 a sufficient distance to cause disk 38 to in turn apply pressure to second seal ring 36. This forms a seal between flange 26 and the exterior of pressurizer 10. The provision of two seals, one at first seal ring 22 and one at second seal ring 36, serves to insure that pressurized coolant inside pressurizer 10 will not leak out of pressurizer 10 between replacement heater sleeve 20 and heater sleeve bore 30. To replace a defective heater sleeve, the original heater 12 is removed. The original heater sleeve 14 exterior of pressurizer 10 and a portion of original heater sleeve 14 in heater sleeve bore 30 are removed. Heater sleeve bore 30 is partially tapped to provide threaded area 32 at its lower end. First seal ring 22 is positioned in heater sleeve bore 30 against original heater sleeve 14. Sleeve 24 is installed in heater sleeve bore 30 by threading sleeve 24 thereinto such that the upper end of sleeve 24 presses against first seal ring 22. This creates a seal between original heater sleeve 14 and sleeve 24. It should be understood that sleeve 24 and first seal ring 22 may be simultaneously installed in heater sleeve bore 30. Jack bolts 40 are then used to cause disk 38 to bear against second seal ring 36. This provides a seal between flange 26 and the exterior of pressurizer 10 A replacement heater is then installed through replacement heater sleeve 20. The replacement heater is welded in place utilizing weld prep 44 provided at the lower end of sleeve 24. Flange 26 and disk 38 have their surfaces that face or may contact the exterior of pressurizer 10 shaped to closely match the contour of that portion of pressurizer 10 where the work is being performed. The use of a replacement heater sleeve that has the same diameter as and is installed immediately adjacent the original heater sleeve maintains the original heater alignment and precludes the need for special alignment procedures. It should be understood that the method and apparatus described and illustrated are applicable to the replacement of a heater sleeve or a nozzle. The terms heater sleeve and nozzle should be considered as interchangeable for the purposes of this description since it is common in the industry to refer to a heater sleeve as a heater nozzle. Therefore, reference to the replacement of a nozzle in the claims should be understood as being applicable to a nozzle or a heater sleeve. Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.