Patent Number: 056339011
Section: summary

FIELD OF THE INVENTION The present invention relates to a permanent pool cavity seal for a nuclear reactor. BACKGROUND OF THE INVENTION A pressurized light water reactor operation is an established operation which is normally carried out with a high degree of reliability. In such reactors, a reactor vessel is positioned in a refueling pool cavity formed by a wall of the concrete shielding structure in a containment device. The refueling pool cavity has instruments positioned therein for monitoring reactivity. The refueling pool and the refueling pool cavity accomodate thermal expansion of the reactor during operation and provide a path for air flow from the bottom of the reactor vessel. Prior to refueling the reactor, the refueling pool is flooded with berated water to provide neutron shielding while the reactor vessel head is removed. To protect instrumentation in the refueling pool cavity, it is necessary to install a seal plate over the cavity before the water is added. During normal reactor operations the reactor vessel is subjected to radial and axial thermal expansion. Consequently, the seal plate currently in use for refueling operation can not be left installed around the reactor vessel and the refueling pool floor in the concrete shielding structure after refueling because it is unable to accomodate the thermal expansion of the reactor vessel. Attempts made at developing a permanent pool cavity seal, that does not require removal after refueling, have, as yet, not been completely successful. SUMMARY OF THE INVENTION The present invention provides a nuclear reactor containment arrangement wherein a permanent pool cavity seal extends across an annular gap between a reactor vessel having a peripheral wall and a horizontally extending flange, and a refueling pool wall which is a concrete shielding structure in the containment organization. The seal plate has a J-shaped flexible ring having an inner downwardly and then horizontally extending section welded at its inner periphery to an inner seal ring which is bolted and sealingly to the reactor vessel flange, and a support ring having an outer downwardly extending cylindrical section welded to an outer seal ring which is bolted and sealingly welded to a ring embedded in a refueling pool floor. The J-shaped flexible ring allows movement of the reactor vessel during thermal expansion and contraction. The permanent pool cavity seal which it provides, is strong and flexible. The permanent pool cavity seal, as it must be, is structurally strong enough to withstand the weight of the water and the impact of the heaviest object which might be dropped inadvertently thereon, without an ensuing a complete or sudden loss of shielding water, and, preferably, with the sealing integrity being substantially maintained. An inner portion of the seal plate overhangs the J-shaped flexible ring to protect it against an object being dropping thereon. The permanent pool cavity seal is also structurally flexible enough to accomodate the redial and the axial thermal expansion and contraction of the the reactor vessel relative to the concrete shielding structure during reactor operation, while substantially maintaining its sealing integrity. A cooperating access hole and access hole cover in the seal plate provide access to the refueling pool cavity. A plurality of support arms underneath the seal plate are provided. Each support arm may have at least a leveling screw to adjust the level of seal plate. This provides a permanent pool cavity seal which allows flooding of the refueling pool for refueling with it only being necessary to remove the access bole covers for normal reactor operations.