Patent Number: 
Section: description

FIG. 1 is a schematic, partial sectional view, with parts cut-away, of a reactor pressure vessel (RPV) 20 for a boiling water reactor. RPV 20 has a generally cylindrical shape and is closed at one end by a bottom head and at its other end by removable top head (not shown). A top guide (not shown) is spaced above a core plate 22 within RPV 20. A shroud 24 surrounds core plate 22 and is supported by a shroud support structure 26. An annulus 28 is formed between shroud 24 and side wall 30 of RPV 20. An inlet nozzle 32 extends through side wall 30 of RPV 20 and is coupled to a jet pump assembly 34. Jet pump assembly 34 includes a thermal sleeve 36 which extends through nozzle 32, a lower elbow (only partially visible in FIG. 1), and a riser pipe 38. Riser pipe 38 extends between and substantially parallel to shroud 24 and RPV side wall 30. A riser brace 40 stabilizes riser pipe 38 within RPV 20. Jet pump assembly 34 also includes inlet mixers 42 connected to riser pipe 38 by transition assembly 44. Inlet mixers 42 are coupled to corresponding diffusers 46 by slip joints 48. Each diffuser 46 includes four guide ears 50 equally spaced around diffuser 46 at slip joint 48. FIG. 2 is a top sectional view of jet pump 34 with a seal assembly 52 attached in accordance with an embodiment of the present invention. FIG. 3 is a front sectional view of jet pump 34 and seal assembly 52. Referring to FIGS. 1 and 2, seal apparatus 52 includes a split seal ring 54 and a segmented diaphragm spring 56 engaging split seal ring 54 at an inner circumference 58 of diaphragm spring 56. Diaphragm spring 56 has a first surface 60 and a second surface 62, and includes a plurality of latch assemblies 64 spaced circumferentially around an outer circumference 66, with each latch assembly 64 configured to engage a diffuser guide ear 50. A seal ring engagement portion 68 depends from second surface 62 of diaphragm spring 56 and extends around inner circumference 58. Seal engagement portion 68 is configured to engage seal ring 54. A support portion 70 depends from second surface 62 of diaphragm spring 56 and extends around outer circumference 66. A plurality of slots 72 extend from inner circumference 58 to support portion 70 of diaphragm spring 56. Slots 72 are spaced circumferentially around inner circumference 58. Each latch assembly 64 includes a substantially L-shaped latch block 74 coupled to first surface 60 of diaphragm spring 56, and a latch bolt 76. An opening 78 extends through upper latch block 74. Latch bolt 76 extends through opening 78 and extends through a corresponding latch bolt opening 80 in support portion 70 of diaphragm spring 56. Each latch bolt 76 includes a head 82 and a plurality of ratchet teeth 84 spaced around a periphery of latch bolt head 82. A locking spring 86 is coupled to upper latch block 74 adjacent opening 78. A retention stub 88 extends from one side of locking spring 86. Retention stub 88 is sized to engage ratchet teeth 84 to lock latch bolt 76 in place and prevent latch bolt 76 from loosening. Upper latch block 74 also includes a release opening 90 located adjacent locking spring 86. Release opening 90 is sized to receive a release tool (not shown) which moves locking spring 86 to disengage retention stub 88 from ratchet teeth 84 to enable latch bolt 76 to be loosened. Referring also to FIG. 4, latch assembly 64 further includes a latch arm 92 coupled to latch bolt 76. Latch arm 92 includes a slot 94 sized to receive a diffuser guide ear 50. Latch arm 92 includes a first engagement finger 96 and a second engagement finger 98 on opposite sides of slot 94. First engagement finger 96 includes an angled end portion 100 to permit latch arm 92 to swing from an open position 102 to a closed or engaged position 104 without guide ear 50 interfering with first engagement finger 96 by contacting an outer surface 106 of first engagement finger 96. A threaded latch bolt opening 108 extends through latch arm 92. Latch bolt 76 extends through and threadedly engages opening 108. A bolt retention collar 110 is attached to latch bolt 76 to retain latch bolt 76 in latch bolt opening 80 in support portion 70 of diaphragm spring 56. Seal apparatus 52 is installed on slip joint 48 by positioning split ring seal 54 and diaphragm spring 56 on an end 112 of diffuser 46 with a spring slot 72 engaging each diffuser guide ear 50. Latch bolt 76 of each latch assembly 64 is tightened so that latch arms 92 swing into position and engage a corresponding guide ear 50. Inlet mixer 42 is installed through split ring seal 54 and diaphragm spring 56 and into diffuser 46 to form slip joint 48. Latch bolt 76 is tightened further to capture the latch arm slot 94 against guide ear 50 to engage seal engagement portion 68 of diaphragm spring 56 with seal ring 54. An elastic deflection of diaphragm spring 56 maintains a sealing force on ring seal 54 while accommodating the minor thermal differential changes in component dimensions during operation of the reactor. Latch bolt 76 is locked in place by locking spring 86 engaging ratchet teeth 84 of clamp bolt head 82. The above described seal apparatus 52 restricts leakage flow between inlet mixer 42 and diffuser 46 at slip joint 48 to prevent oscillating motion and to eliminate high level flow induced vibration. Additionally, the wedging action of seal 54 in the slip joint opening provides a rigid resistance to oscillating motion. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.