Patent Number: 062018477
Section: description

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a top sectional view of a boiling water nuclear reactor pressure vessel 10. Reactor pressure vessel 10 includes a vessel wall 12 and a shroud 14 which surrounds the reactor core (not shown) of pressure vessel 10. An annulus 16 is formed between vessel wall 12 and shroud 14. The space inside annulus 16 is limited with most reactor support piping located inside annulus 16. Cooling water is delivered to the reactor core during a loss of coolant accident through core spray distribution header pipes 18 and 20 which are connected to downcomer pipes 22 and 24 respectively. Downcomer pipes 22 and 24 are connected to shroud 14 through lower T-boxes 26 and 28 respectively, which are attached to shroud 14 and internal spargers 30. Distribution header pipes 18 and 20 diverge from an upper T-box assembly 32. Particularly, T-box 32 includes, in one embodiment, a T-box housing 34 having first, second, and third ends 36 (shown in FIG. 2), 38, and 40. First end 36 of T-box housing 34 is coupled to a safe end 42 of core spray nozzle 44. Ends 38 and 40 are configured to be in substantial alignment and configured to couple to core spray line header pipes 18 and 20 respectively. Header pipes 18 and 20 are coupled to second and third ends 38 and 40 by pipe connectors 46 and 48 respectively. Pipe connectors 46 and 48 may be any pipe connectors known in the art, but preferably, are pipe connectors such as described in co-pending U.S. patent application Ser. No. 08/909,283, entitled PIPE CONNECTOR ASSEMBLY, filed Aug. 11, 1997, and assigned to the present assignee. FIG. 2 is a sectional side view with parts cut away of T-box assembly 32. In one embodiment, T-box assembly 32 includes in addition to T-box housing 34, a cruciform wedge 50 and a draw bolt 52. T-box housing 34 is configured to be positioned so that first end 36 is located inside core spray nozzle 44 and engages core spray nozzle safe end 42. Particularly, safe end 42 includes a first end 54, a second end 56, and a bore 58 extending between ends 54 and 56. Bore 58 includes a tapered portion 60 located between ends 54 and 56. First end 36 of T-box housing 34 engages core spray nozzle safe end 42 at first end 54 forming a metal-to-metal interface 62. T-box housing 34 also includes a cover opening 64 that is in substantial alignment with first end 36, and is configured to receive a T-box cover plate 66. T-box cover plate 66 includes a draw bolt opening 68 configured to receive draw bolt 52. First end 36 of T-box housing 34 also includes a plurality of positioning lugs 70 (one shown) configured to engage core spray nozzle 44 to center T-box housing 34 in core spray nozzle bore 72. Draw bolt 52 is configured to extend through a bore 74 of a central member 76 of cruciform wedge 50. Draw bolt 52 comprises a cap portion 78 located at a first end 80 configured to be larger than the diameter of bore 74 through central member 76 of cruciform wedge 50. A second end 82 of draw bolt 52 is configured to extend through draw bolt opening 68 in T-box cover plate 66 and to threadenly engage a draw bolt nut 84. Referring to FIG. 3, cruciform wedge 50 includes central member 76 having bore 74 extending therethrough. First, second, third and fourth web members 86, 88, 90, and 92 extend from central member 76. Web members 86, 88, 90, and 92 are configured so as to form an X shaped configuration. Support members 94 and 96 extend between ends 98, 100, 102, and 104 of adjacent web members 86, 88, 90, and 92. Particularly, support member 94 extends between first and second web members 86 and 88, and support member 96 extends between third and fourth web members 90 and 92. Support members 94 and 96 are configured to conform to bore 58 of core spray nozzle safe end 42. Particularly support members 94 and 96 are configured to engage tapered portion 60 of safe end bore 58 (shown in FIG. 2). Additionally, web members 86, 88, 90, and 92 are configured to be contoured to minimize flow resistance. To replace a core spray line in nuclear reactor pressure vessel 10, the existing T-box/thermal sleeve combination is removed from core spray nozzle safe end 42 by conventional underwater plasma arc cutting and/or electric discharge machining (EDM). Typically, a small portion of end 54 of safe end 42 is also removed. First end 54 is then prepared, usually by EDM, to mate with first end 36 of T-box housing 34. Particularly, first end 54 of safe end 42 is machined so as to form a metal-to-metal interface 62 with first end 36 of T-box housing 34. T-box assembly 32 is used to connect core spray lines 18 and 20 to safe end 42 of core spray nozzle 44 by coupling first end 36 of T-box housing 34 to safe end 42 and coupling ends 38 and 40 to core spray distribution header pipes 18 and 20. Particularly, to couple first end 36 of the T-box housing 34 to safe end 42, cruciform wedge 50 and draw bolt 52 are inserted into safe end bore 58. Cruciform wedge 50 is configured with webs 86, 88, 90, and 92 in an X-shaped configuration and only two support members 94 and 96 connecting web members 86, 88, 90, and 92 to permit wedge 50 to be inserted into safe end bore 58. Wedge 50 is inserted in an orientation that positions the axis of bore 74 of central member 76 of wedge 50 perpendicular to the axis of bore 58 of nozzle safe end 42. Wedge 50 is then tilted so as to move central member bore 74 into co-axial alignment with safe end bore 58, and support members 94 and 96 into engagement with tapered portion 60 of safe end bore 58. Draw bolt 52 is then inserted through bore 74 of wedge central member 76 with threaded end 82 of draw bolt 52 extending away from safe end 42 and towards T-box housing 34. This may be accomplished by attaching a thin wire (not shown) to threaded end 82 of bolt 52 and threading the wire through wedge central member bore 74 before inserting wedge 50 and draw bolt 52 into safe end 42. After wedge 50 has been tilted to its operational position the wire may be pulled through central member bore 74 which in turn pulls threaded end 82 of draw bolt 52 through wedge bore 74 and into position with cap portion 78 of bolt 52 engaging central member 76 of wedge 50. T-box housing 34 is then positioned with the alignment lugs 70 engaging the inside surface of core spray nozzle 44 and first end 36 of housing 34 engaging first end 54 of safe end 42. T-box cover plate 66 is then positioned over cover opening 64 with threaded end 82 of draw bolt 52 extending through draw bolt opening 68 in cover plate 66. Draw bolt nut 84 is then threaded onto bolt 52 and tightened to a predetermined torque. Core spray header pipes 18 and 20 are then coupled to ends 38 and 40 of T-box housing 34 to complete the installation. The above described T-box assembly 32 facilitates replacing core spray lines 18 and 20 without removing core spray nozzle safe end 42 or draining reactor 10. In addition T-box assembly 32 facilitates attaching core spray lines 18 and 20 to safe end 42 without welding. From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.