Patent Number: 054003741
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to cranes for use in environments such as encountered in a boiling water nuclear reactor (BWR). More specifically, the present invention relates to a water proof cover arrangement for a heavy-duty overhead crane which prevents crane components from becoming radioactively contaminated when lowered into water which fills the reactor pressure vessel and surrounding reactor cavity. 2. Description of the Relevant Art Movement of large pieces of equipment and components of a boiling water reactor is accomplished by flooding the reactor cavity and pressure vessel in a manner wherein radioactive emissions are suppressed and it is possible to remove the reactor head and perform routine maintenance, refuelling and the like. These procedures however, require that large pieces of equipment, such as steam seperators, be lifted out of the reactor pressure vessel and transferred to pools which are provided adjacent to the vessel and that form part of the reactor cavity. To achieve this transfer, it is necessary to use a heavy-duty overhead crane which comprises a part of the reactor system and which is mounted above the reactor cavity. Due to the limited space available within the reactor pressure vessel and the geometry of the pool of the reactor cavity within which the loads are temporarily stored, it is sometimes necessary to lower the crane hook below the surface of the water. Because the water is radioactive, it is undesirable for the crane hook, hook block or cables which supports the hook block, to come into direct contact with the water, as such contact causes contamination and demands that these pieces of apparatus be thoroughly washed or otherwise suitably decontaminated after each use. U.S. Pat. No. 5,170,899 issued on Dec. 15, 1992 in the name of Baversten (the same inventive entity as named on this application), discloses an arrangement wherein a telescopic cover arrangement is provided on the hook box connected to the load to be lifted by the crane. The telescopic arrangement is arranged to be extendible when the hook is lowered below the surface of the water in a manner which encloses the hook, hook block and the lower portions of the suspending cables and provides an air space thereabout. However, in order for this telescopic arrangement to be effective, a water-tight interface must be provided between the two moving elements. Further, in order achieve extension and contraction of the arrangement a remotely controlled servo which is either hydraulic or pneumatically operated, is required. This construction, however, requires both a precise seal and the provision of the remotely controlled hydraulic or pneumatic servo. The construction is thus relatively complex and expensive. SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a watertight cover for apparatus such as a crane hook, hook block and cables, which does not interfere with the crane operation and which is both relatively simple and inexpensive. It is a further object of the present invention to provide a watertight cover arrangement which extends or deploys automatically in response to immersion in water and therefore obviates a need for a remotely controlled servo device for such purposes. In brief, the above objects are achieved by an arrangement wherein a bellows-like construction which automatically extends upon immersion in water, is used as part of a water-tight enclosure for lifting equipment and the like. The lower end of the bellows is connected to the top of a tubular member which extends up from a hook box or like type of container-like structure, in a manner to form a hermetic seal. The upper end of the bellows-like arrangement is provided with a buoyant member which provides sufficient lift that, when the lifting equipment is lowered into the water to a predetermined depth, the buoyant member floats on the surface of the water in a manner which extends a corrugated tubular portion of the arrangement and prevents radioactive water from spilling over into the box thus preventing contamination of a hook, hook block and associated apparatus which are enclosed therein. More specifically, a first aspect of the present invention resides in a cover for a hook box which encloses a hook and hook block, and which features: a rigid tubular member which is fixedly connected to the hook box in a manner which establishes a water-tight seal therebetween; an expandable bellows member having a lower end and an upper end, the lower end being connected to the rigid tubular member in a manner which defines a water-tight seal, the bellows member and the rigid tubular member defining an air space which extends upwardly from the hook box in a manner which encloses the hook box and cables which interconnect the hook block with an overhead crane; and a buoyant member which is disposed about the upper end of the bellows member and which is effective to expand the bellows in response to the hook box being lowered into water by a predetermined amount. A second aspect of the invention resides in a nuclear reactor system which features: a reactor pressure vessel disposed in a reactor cavity, the reactor cavity including a separator pool which is separated from the reactor pressure vessel by a separator pool threshold; an overhead crane which is disposed above the reactor cavity and which is arranged to lift and transport a device that is normally disposed in the reactor pressure vessel, from the reactor pressure vessel to the separator pool while the reactor cavity is filled to a predetermined depth with water, the overhead crane including: a hook block which is suspended from the crane by cables; a hook operatively connected with the hook block and engageable with the device; a hook box which encloses the hook; a tubular extension which extends upwardly from the hook bock and which encloses the hook block and a portion of the cables; and a bellows arrangement provided at the upper end of the tubular extension, the bellows arrangement including: a flexible corrugated tube section, the flexible corrugated tube section having a lower end which is connected to the tubular extension in a manner which provides a watertight connection; and a buoyant member which is connected to an upper end of the corrugated tube section and effective to float on the surface of the water and cause the flexible corrugated tube to extend when the hook box is lowered to a predetermined depth below a surface of the water. Another aspect of the invention resides in a method of preventing radioactive contamination of a hook, a hook block and associated cables, by: enclosing the hook and hook block in a hook box on which a tubular extension has been provided; providing a bellows arrangement at the top of the tubular extension; and using a buoyant member which forms part of the bellows arrangement and which floats on the surface of water used to suppress radioactive emissions, to elongate a flexible tubular portion which forms part of the bellows arrangement when the hook box submerges by a predetermined amount below the surface of the water. A further aspect of the present invention resides in an apparatus for preventing contamination of a hook, a hook block and associated cables, which features: enclosure means which encloses the hook and the hook block, the enclosure means including a hook box and a tubular extension which is provided on the hook box and which extends up and around the hook block and cables which support the hook block; and bellows means at the top of the tubular extension, the bellows means including a buoyant member which is effective to float on water and provide sufficient lift to elongate a flexible corrugated tubular portion of the bellows arrangement when the hook box submerges by a predetermined amount below a surface of the water and thus prevent the hook, hook block and cables from coming into contact with the water. Yet another aspect of the present invention resides in an enclosure for a device which features: a container-like structure which encloses the device; a flexible corrugated tube member which is sealingly connected to the container-like structure; and floatation means for causing the flexible corrugated tube member to extend upwardly when the container-like structure is immersed in water and prevent water from entering the container-like structure and coming into contact with the device.