Patent Number: 053234359
Section: summary

BACKGROUND OF INVENTION 1. Field of the Invention This invention relates to supports and, more particularly, to boiling water reactor control rod drive housing supports. Still more particularly, this invention relates to control rod drive housing supports with wing assemblies to limit the travel of a control rod in the event that a control rod housing is ruptured, which do not have to be removed during replacement of a control rod drive. 2. Description of Prior Art In boiling water reactors the control rod drive housing supports are generally located underneath the reactor vessel near the control rod housings. The control rod drive housing supports limit the travel of and support a control rod in the event that a control rod drive housing is ruptured. The supports prevent a nuclear excursion as a result of a housing failure, thus protecting the fuel barrier. Typically, control rod drive housing supports consist of hanger rods that are attached and supported at their upper end at a beam structure immediately underneath the reactor pressure vessel and support bars which are bolted between the hanger rods below the control rod drives. Another grid of bars is installed on the support bars to transfer the load of a ruptured control rod drive housing to the support bars. Generally, a pair of grid bars support each control rod drive. Each pair of grid bars are held together by two grid clamps and a bolt. In this support system of the prior art, when it is necessary to change or replace a control rod drive, the grid bars must be removed. In order to remove the grid bars the operator must manually unscrew the grid clamp bolt, remove the two grid clamps and then remove the grid bars, each weighing approximately forty pounds. The number of grid bars which must be removed depends on the number of control rods which must be replaced. Furthermore, since the grid bars are interlocking, they must be removed starting from the outer peripheral row. Thus, if a large number of control rod drives must be replaced or if an inner control rod drive must be replaced, a large number of grid bars must be removed. The result is a time consuming and cumbersome process. Moreover, as the grid bars are heavy and awkward to handle, a dropped bar could result in serious injury. Further still, the persons handling the grid bars are subject to substantial radiation doses. The more time a person must spend replacing the control rod drives, the more that person is subject to radiation. Thus, it is a problem in the prior art to adequately support a control rod drive housing in a boiling water reactor while allowing for quick and easy replacement of control rod drives and reducing and minimizing the amount of radiation exposure resulting from such replacement. SUMMARY OF THE INVENTION It is an object of the present invention to support a control rod drive housing in the event that a control rod housing is ruptured while at the same time allowing quick and easy replacement of a control rod drive. It is another object of the present invention to provide a control rod drive housing support which minimizes the amount of radiation which a person is subject to when replacing a control rod drive. It is another object of the present invention to provide a control rod drive housing support which need not be removed when changing a control rod drive. 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, the control rod drive housing support of this invention may comprise a first means for supporting a control rod drive; and a second means for supporting said control rod drive, the second supporting means disposed on the first supporting means wherein the second supporting means is movable on the first supporting means from a support position to a non-support position, whereby the control rod drive is supported by the first and second supporting means when the second means is in the support position and the control rod drive is not supported by the first and second supporting means and can be replaced without removing the second supporting means from the first supporting means when the second supporting means is in said non-support position. Further, the first supporting means may comprise a plurality of support members provided in rows on opposing sides of a lower portion of a plurality of control rod drives and the second supporting means may comprise a plurality of second support members disposed on the first support members, each of the second support member having a plurality of extension members for supporting the control rod drives. In addition, the first support members may have a plurality of hubs for receiving the plurality of second support members rotatably thereon and the second support members may have a hole therethrough for receiving one of the plurality of hubs rotatably therein.