Patent Number: 052727327
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a seal for the space between an adjacent nuclear reactor vessel annular flange and a surrounding ledge or plate to provide a water barrier for supporting a liquid in a cavity called a refueling pool and, more particularly, to a permanent seal joint which is able to accommodate the radial, axial and rotational movements between the reactor vessel and the pool walls. 2. Description of Prior Art A nuclear reactor vessel is typically positioned in a cavity or containment system. The reactor vessel is spaced from the cavity wall so as to provide an annular expansion gap and permit the reactor vessel to expand each in both a horizontal and vertical direction during cyclic heating and cooling periods of the reactor. An upper annular portion of the cavity above the vessel serves as a refueling canal or pool. The refueling pool, while maintained dry during reactor operation, is filled with water during refueling of the nuclear reactor. During refueling, the head of the reactor pressure vessel is removed and the refueling pool is filled with water. The reactor pressure vessel has flanges which secure the head assembly to the body of the vessel. The cavity wall typically also has an edge or flange. During refueling operations, the annular gap between the reactor vessel and the pool floor must be closed tightly to prevent refueling water from entering the lower part of the reactor cavity. The seal between the reactor pressure vessel flange and the cavity wall flange serves as a floor for the body of water that is place in the refueling pool. Typically, this gap has been sealed using the contact seal or the gasket seal method by pressing a relatively soft material, the gasket, between the fluid passing surfaces to achieve a seal. These elastomeric seals, however, are subject to degradation and leakage. In addition, the gasket seal requires constant inspection and maintenance, which is difficult to perform in the gaskets, high dose radioactive and thermal environment and in view of the usually tight refueling schedules. It is desirable, therefore, to provide a permanent seal which overcomes the disadvantages of the gasket seal. Attempts have been made to provide permanent seals, such as the seals described in U.S. Pat. No. 5,102,612, incorporated herein by reference and U.S. Pat. No. 4,904,442. The seal described in U.S. Pat. Nos. 4,904,442 and 5,102,612 are some type of vertically extending, straight walled inner and outer seal provided on an annular ring seal. These seals, however, are subject to high stresses and do not last as long as the life of the plant. These seals fail to accommodate the radial, axial and rotational movements between the reactor vessel and the pool floor for the life of the plant and fail to withstand the required heating and cooling cycles of the plants. Thus it is a problem in the prior art to provide a permanent seal between the reactor vessel and pool floor which requires no maintenance or inspections, which can withstand the heating and cooling cycles of the plant, which can accommodate the radial, axial and rotational movements, between the reactor vessel and the pool floor for the life of the plant and which is not subject to leakage. SUMMARY OF THE INVENTION It is an object of the present invention to provide a permanent seal between the reactor vessel and the pool floor in a nuclear power plant which requires no maintenance or inspection and lasts the life of the plant. It is a further object of the present invention to provide a seal which is not subject to degradation or leakage. It is a further object of the present invention to provide a seal which can withstand the radioactive and thermal environment of the plant, including the heating and cooling cycles of the plant. It is a further object of the present invention to provide a seal which can accommodate the radial, axial and rotational movements between the reactor vessel and the pool for the life of the plant. Additional objects, advantages and novel features of the invention will be set forth in the description which follows, and will become apparent to those skilled in the art upon reading this description or practicing the invention. The objects and advantages of the invention may be realized and attained by the appended claims. To achieve the foregoing and other objects, in accordance with the present invention, as embodied and broadly described herein, a permanent seal for providing an effective water barrier over an annular space between a nuclear reactor vessel flange and a surrounding annular ledge comprising: an annular space-spanning deck structure; a first annular seal member for providing a support of the deck and a seal between the deck structure and the surrounding annular ledge; and a second flexible annular seal member for providing a seal between the deck structure and the vessel flange and wherein a portion of the second seal member is straight walled and another portion of the second seal member is force absorbing. Further, the force absorbing section may be arcuate or coil shaped.