Patent Number: 056339011
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT The permanent pool cavity seal according to the invention is generally comprised of seal plate 10, inner seal ring 13, outer seal ring 14, J-shaped flexible ring 11, support ring 12, leveling screw support arm 15, leveling screw 16, and means for covering and sealing access hole 32 in seal plate 10. Seal plate 10 is an annular member preferably formed from stainless steel, which is 1.5 inches in thickness for withstanding the weight of the water and the impact of any fuel which may be dropped during the refueling operation. Seal plate 10 is formed from a plurality of arcuate plates such that they form an annular seal plate 10 when positioned adjacent to each other around reactor vessel 26. The arcuate plates are splice welded together before being welded respectively to support ring 12 and J-shaped flexible ring 11. Seal plate 10 is provided with a plurality of access holes 32 spaced around its circumference. Access holes 32 provide access to nuclear instruments positioned therebelow in the refueling pool cavity 21 between reactor vessel 26 and concrete shielding structure 25 and allow circulation of air from beneath reactor vessel 26 during normal reactor operations. Each access hole 32 in seal plate 10 has two annular concentrically disposed grooves 30, each containing an O-ring 31 to provide the seal around its circumference. Each access hole cover 28 is secured in its associated access hole 32 by bolts 35 and has a hole 29 and hole plug 33 which is fastened by bolts and which provides means to check the seal condition before the refueling cavity is flooded. Seal plate 10 is provided with an annular support ring 12 and an annular J-shaped flexible ring 11 that extends axially from the seal plate. Support ring 12 is preferably formed from the same material as seal plate 12. Support ring 10 is formed from a plurality of arcuate plates such that they form the annular support ring 12 when positioned adjacent to each other on the refueling pool floor 23. The arcuate plates are splice welded together before being welded to seal plate 10. J-shaped flexible ring 11 must also be structurally flexible enough to accomodate the radial and axial thermal expansion or contraction of the reactor vessel 26. J-shaped flexible ring 11 is preferably formed from stainless steel which has 0.1 to 0.2 inches thickness. J-shaped flexible ring 11 is formed form a plurality of arcuate plates such that they form an annular J-shaped flexible ring 11 when positioned adjacent to each other on the reactor vessel flange 27. The arcuate plates are splice welded together before being welded to seal plate 10. Seal plate 10 is welded respectively to support ring 12 and J-shaped flexible ring 11 before in-place installation. Outer seal ring 14 and inner seal ring 13 are preferably formed from the same material as seal plate 10. Outer seal ring 14 and inner seal ring 13 are formed from a plurality of arcuate plates that form the outer seal ring 14 and inner seal ring 13 respectively, when positioned adjacent to each other. The arcuate plates forming the outer and inner seal rings are splice welded together before being attached by bolts 36 and sealingly welded to reactor vessel flange 27 and embedded ring 24 in refueling pool floor 23, respectively. A plurality of support arms 15 underneath the seal plate 10 are provided to support seal plate 10. Each support arm 15 extending from the refueling pool cavity wall 25 toward the seal plate 10 adjacent the J-shaped flexible seal 11 may have at least a leveling screw 16 to adjust the level of seal plate 10.