Canister transfer system with independent traveling shielded bell

A transfer system for spent fuel canisters includes a carrier, a shielded bell trolley movable along the carrier and carrying a shielded bell, and a canister trolley movable along the carrier and carrying a lifting mechanism for raising and lowering the spent fuel canister into and out of the shielded bell. The canister trolley can move along the carrier independent of the shielded bell trolley and the shielded bell trolley can move along the carrier independent of the canister trolley. The shielded bell trolley and the canister trolley can be selectively interlocked for selected transfer operations.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

REFERENCE TO MICROFICHE APPENDIX

Not Applicable

FIELD OF THE INVENTION

The field of the present invention generally relates to overhead hoist or crane systems and, more particularly, to such systems for transporting canisters of spent nuclear fuel.

BACKGROUND OF THE INVENTION

Spent nuclear fuel is typically transferred in canisters which are moved by overhead hoist or crane systems. For example, see U.S. Pat. Nos. 6,674,828 and 6,788,755, the disclosures of which are expressly incorporated herein in their entireties by reference. The spent nuclear fuel remains highly radioactive and is capable of generating significant thermal energy. Therefore, the canisters are typically transferred within a shielded bell.

While prior hoist systems may adequately transfer the spent fuel canisters, they can be rather complex and expensive to produce and operate. The hoists must have a relatively high rating because it must raise both the spent fuel canister and the shield bell at the same time. For example, a hoist may need to be rated for 200 tons when the maximum weight of the spent fuel container is only 70 tons. Additionally, the hoist must have the ability to automate and have accurate reliable positioning to engage and manipulate the spend fuel canister. Accordingly, there is a need in the art for an improved system and method for transporting canisters of spent nuclear fuel.

SUMMARY OF THE INVENTION

The present invention provides a system and method for transporting canisters of spent nuclear fuel that solve at least problem of the related art. According to one embodiment of the present invention, a transfer system for moving a spent fuel canister comprises, in combination, a carrier, a shielded bell trolley movable along the carrier and carrying a shielded bell, and a canister trolley movable along the carrier and carrying a lifting mechanism for raising and lowering the spent fuel canister into and out of the shielded bell. The canister trolley can move along the carrier independent of the shielded bell trolley.

According to another embodiment of the present invention, a transfer system for moving a spent fuel canister comprises, in combination, a carrier, a shielded bell trolley movable along the carrier and carrying a shielded bell, and a canister trolley movable along the carrier and carrying a lifting mechanism for raising and lowering the spent fuel canister into and out of the shielded bell. The carrier directly supports the shielded bell trolley so that the lifting mechanism does not support the shielded bell.

According to yet another embodiment of the present invention, a transfer system for moving a spent fuel canister comprises, in combination, a bridge, a shielded bell trolley movable along the bridge and carrying a shielded bell, and a canister trolley movable along the bridge and carrying a hoist for raising and lowering the spent fuel canister into and out of the shielded bell. The bridge includes a first pair of spaced-apart rails for supporting the canister trolley and a second pair of spaced-apart rails for supporting the shielded bell trolley. The first pair of spaced-apart rails is substantially parallel to the second pair of spaced-apart rails. The bridge is movable along a third pair of spaced-apart rails substantially perpendicular to the first pair of spaced-apart rails and the second pair of spaced-apart rails. The canister trolley can move along the bridge independent of the shielded bell trolley and the shielded bell trolley can move along the bridge independent of the canister trolley.

From the foregoing disclosure and the following more detailed description of various preferred embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology of system and method for transporting canisters of spent nuclear fuel. Particularly, the invention provides a relatively low cost system which meets performance requirements. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the canister transfer systems as disclosed herein, including, for example, specific dimensions, orientations, and shapes of the various components will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity or illustration. All references to direction and position, unless otherwise indicated, refer to the orientation of the transfer systems illustrated in the drawings. In general, up or upward refers to an upward direction generally in the plane of the paper inFIG. 1and down or downward refers to a downward direction generally in the plane of the paper inFIG. 1.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

It will be apparent to those skilled in the art, that is, to those who have knowledge or experience in this area of technology, that many uses and design variations are possible for the transfer systems and methods disclosed herein. The following detailed discussion of various alternative and preferred embodiments will illustrate the general principles of the invention with reference to a transfer system for spent nuclear fuel canisters. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.

Referring now to the drawings,FIGS. 1 and 2shows a canister transfer system10according to a preferred embodiment of the present invention. The operating envelope of the illustrated canister transfer system10provides coverage of a transportation cask transfer cell, waste package transfer cell, canister staging cells, and transfer system maintenance/staging area. The illustrated canister transfer system10includes a carrier12, a first or shielded bell trolley14movable along the carrier12and carrying a shielded bell16, and a second or canister trolley18movable along the carrier12and carrying a lifting mechanism20for raising and lowering the spent fuel canister22(seeFIG. 9) into and out of the shielded bell16.

The illustrated canister transfer system10is in the form of a bridge crane, wherein the carrier12in the form of a bridge24. It is noted that the canister transfer system10can alternatively have any other suitable form and/or the carrier12can alternatively have any other suitable form. The illustrated bridge24includes end trucks riding on a pair of laterally spaced apart and parallel rails26. The illustrated rails26are straight but it is noted that any other suitable configuration for the rails26can be utilized. The illustrated rails26supported by corbels28located on laterally spaced-apart walls30. It is noted that any other suitable supports for the rails26can alternatively be utilized. The distance between the rails26can be any suitable distance such as, for example, about eighty six feet.

The illustrated bridge24is formed by box frame girders32. Girder plates are preferably continuous welded for maximum strength, stiffness, and torsional stability but can alternatively be constructed in any other suitable manner. Bumpers34are provided at the ends of the rails26which are designed to minimize impact to the canisters22being transferred. Each bridge girder32supports the two trolleys14,18. A first or inner pair of rails36is provided for the canister trolley18and a second or outer pair of rails38is provided for the shielded bell trolley14. The rails36,38are preferably fastened to the girders32with welded clips but can alternatively be secured in any other suitable manner. The rails36,38are mounted on top of the girders32so that the bridge24directly and independently supports each of the two trolleys14,18. The illustrated first pair of spaced-apart rails36is substantially parallel to the second pair of spaced-apart rails38. The illustrated first and second pairs of rails36,38extend in the lateral direction, that is along the longitudinal length of the bridge24, such that the first and second pairs of rails36,38are substantially perpendicular to the rails26for the bridge24. The illustrated first and second pairs of rails36,38are each straight but it is noted that any other suitable configuration for the rails36,38can be utilized. The illustrated first and second pairs of rails36,38are located at the same height but can alternatively be located at other heights as described in more detail hereinafter.

The canister or main hoist trolley18includes a frame or body40having a plurality of wheels42which cooperate with the rails36so that the canister trolley18can be selectively moved along the rails36. The canister trolley18can have any suitable type of drive mechanism for the wheels42such as, for example, an electric motor. The illustrated canister trolley18rides on the inner rails36of the bridge24and is preferably provided with seismic restraints.

The canister trolley18also includes the lifting mechanism20for performing various transfer operations including raising and lowering the canisters22. The illustrated lifting mechanism20is a crane or hoist system44having a remote grapple attachment or system46. It is noted that any other suitable type of lifting mechanism20can alternatively be utilized. The crane or hoist44preferably utilizes failure proof technology. The illustrated hoist44includes an upper block assembly48and a lower block assembly50that is suspended from the upper block assembly52by a reeving arrangement52. Operation of an electric motor raises and lowers the lower block50. Secured to the lower block assembly50is the grapple attachment46which is adapted to interact with the shielded bell16and the canisters22as described in more detail hereinafter. The remotely operated grapple attachment46preferably utilizes limit switches to verify grapple engagement. The grapple attachment46preferably utilizes a mechanism that includes a mechanical safe drive that will not allow the grapple attachment46to disengage when a load is suspended from the grapple attachment46. The canister trolley18can have any suitable hoisting capacity such as, for example, seventy tons. Electrical power to the canister trolley18is provided through hard-wired connections using a cable track system.

The illustrated shielded bell16is generally cylindrical shaped and has an inner wall54which forms an interior space or main shielding chamber56. The illustrated shielded bell16has a pair of opposed lifting lugs or trunnions58near its top end which are used by the trolley14to hold the shielded bell16. The shielded bell16be can have any suitable size such as, for example, a height of about twenty-five feet, an outside diameter of about ninety-four inches, and an inside diameter of about seventy two inches. The shielded bell16can be formed of any suitable material such as, for example, steel and preferably reduces radiation exposure to operating personnel by limiting the contact dose rate (exterior of the shielded bell16) to about one hundred mrems/hr. The total weight of the shielded bell16supported by the shielded bell trolley14can be, for example, about two hundred tons.

The bottom end of the illustrated shielded bell16can be attached to a chamber60to accommodate cask lids having diameters of, for example, up to eighty-four inches. A bottom plate62with an opening can be attached to the chamber to support a motorized shield gate64. The bottom plate62can have a thickness of, for example, about nine inches and the opening can have a diameter of, for example, about eighty six inches. The shield gate64can have a thickness of, for example, about twelve inches. The sliding shield gate64provides bottom shielding for the canister22once the canister22is inside the shielded bell16. A shielded skirt66is provided around the perimeter of the bottom plate62which can be raised and lowered with the help of mechanical actuators. The shield skirt66is used to close any gap between the bottom plate62and a floor surface68to prevent any lateral radiation shine during a canister transfer operation. The shielded skirt66can have a thickness of, for example, about nine inches. The bottom plate62can preferably be located about two inches above the concrete floor68where canister transfer ports are located.

The shielded bell trolley14supports the shielded bell16and includes a frame of body70having a plurality of wheels72which cooperate with the rails38so that the shielded bell trolley14can be selectively moved along the rails38. The shielded bell trolley14can have any suitable type of drive mechanism for the wheels72such as, for example, an electric motor. Electrical power to the shielded bell trolley14is provided through hard-wired connections using a cable track system. The shielded bell trolley14also includes grapple means74for interacting with the shielded bell16. The illustrated grapple means74is in the form of a pair of paddles secured directly to the trolley frame70. The paddles74include openings for receiving the trunnions58of the shielded bell16. It is noted that the grapple means74can alternatively be of any suitable type. It is also noted that if desired the shielded bell trolley14can alternatively include a crane or hoist such as that described in U.S. patent application Ser. No. 11/839,797, the disclosure of which is expressly incorporated herein in its entirety by reference.

The illustrated shielded bell trolley14rides on the outer rails38and supports the shielded bell16which includes the main shielding chamber60for shielding canisters22, a lower larger chamber76for accommodating cask lids78, and the slide gate64for providing bottom shielding for canisters22when inside the shielded chamber60. The shielded bell trolley14carries the entire load of the shielded bell16and the bridge24directly supports the shielded bell trolley14so that the hoist system44of the canister trolley18is never required to support the shielded bell16. The load path for the shielded bell16does not pass through the hoist system44or the canister trolley18. This enables the hoist system44of the canister trolley18to be sized smaller than if it must carry the load of the shielded bell16. For example, a seventy ton hoist44can be utilized when the shielded bell16weighs about two hundred tons or more. The shielded bell trolley14is preferably provided with seismic restraints. The trunnion-type attachment of the shielded bell16to the shielded bell trolley14preferably forma a swivel type joint to minimize transmission of seismic load to the trolley frame70.

All hoist, trolley and bridge drive gearing is preferably enclosed in sealed gear boxes, with oil of high flash point such as four hundred degrees Fahrenheit or better, that will not support a flame or fire. Electric power is provided by a crane cable track system80located along the runway length and supported by the facility walls30. The canister trolley18, the hoist system44, and the shielded bell trolley14are each preferably controlled from a control room with a local control station as a backup. Limit switches, load cells and interlocks are preferably provided for the operation of the two trolleys14,18.

The illustrated canister transfer system10allows for the two trolleys14,18to move independently of one another when desired and to be selectively interlocked together to operate as a single unit when performing selected canister transfer operations. To mechanically interlock the trolleys14,18together, the canister trolley18with the grapple46is first positioned concentric with the shielded bell16, wherein the central axis of the grapple46is aligned with the central axis of the shielded bell16. The two trolleys14,18are mechanically interlocked locked prior to starting a canister transfer operation by lowering the grapple46into the shielded bell16. It is noted that the trolleys14,18can alternatively be mechanically interlocked in any other suitable means.

FIGS. 3 to 5illustrate a canister transfer system100according to second embodiment of the present invention. The second embodiment of the canister transfer system100illustrates that the shielded bell trolley14can be in an under running position. Either an over running or under running configuration can be utilized depending on the total allowable head room for the application. The illustrated rails38for the shielded bell trolley14are located outward and below the rails36for the canister trolley18. Located above the shielded bell trolley14is the canister trolley18which operates independently of the shielded bell trolley14and has a telescoping mast102with a universal nose that can be attached to various tools for the work that needs to be performed. A tool box104for the tools can be located at an end of the shielded bell trolley14.

FIGS. 6 to 9illustrate a transfer system200according to third embodiment of the present invention. The third embodiment of the canister transfer system200illustrates that the shielded bell trolley14can be located inward of the canister trolley18. The illustrated rails38for the shielded bell trolley14are located inward and below the rails36for the canister trolley18. Located above the shielded bell trolley14is the canister trolley18which operates independently of the shielded bell trolley14.

A typical canister transfer operation using the canister transfer system10,100,200includes positioning the shielded bell16over a port on a concrete deck or floor68with the shielded bell bottom being about two inches above the deck68. Below the concrete deck68is a shielded transfer cell76with the port located above a loaded storage cask82. In a similar manner, an empty waste package is positioned under an adjacent port of the waste package transfer cell. Each port is equipped with a motorized shielded gate and flushed with concrete deck surface.

The transfer operation typically begins by positioning the canister transfer system10over the port with the loaded storage cask82. The shield skirt66is remotely lowered to rest on the deck68to prevent any lateral radiation shine. The shielded slide gate84on the concrete deck68is opened to access the cask lid78located below. The slide gate64of the shielded bell16is opened and the grapple46is lowered through the shielded bell16. The grapple46is engaged with a mounted lift fixture on the cask lid78. The cask lid78is raised into the larger chamber78of the shielded bell18. The deck slide gate84is closed and the shield skirt66is raised. The canister transfer system10is moved and positioned over a cask lid staging area located on the concrete deck. The cask lid78is lowered and placed in the staging area and the grapple46is raised. The canister transfer system10is moved back over the port with the loaded storage cask below82, and the canister transfer system10is positioned and aligned for canister pickup and the shield skirt66of the shielded bell16is lowered. The deck slide gate84is opened and the grapple46is lowered to engage the canister lifting feature. The canister22is pulled up into the shielding chamber56shielded bell16. Both the transfer system slide gate64and the deck slide gate84are closed. The shield skirt66of the shielded bell16is raised and the canister transfer system10is moved over the waste package port for canister loading. The canister transfer system10is positioned and aligned with the port and the shield skirt66of the shielded bell16is lowered. Both the shielded bell and deck slide gates64,84are opened. The canister22is lowered and placed into the waste package. The grapple46is then disengaged from the canister22and removed in a reverse manner.

It is apparent from the foregoing disclosure that the canister trolley18can traverse the bridge24independently of the shielded bell trolley14. This permits the canister trolley18to travel to and from the tool crib104located on the shielded bell trolley14to retrieve various tools and grapples required for removing the spent fuel canisters22from one storage cask82and transferring them to another. The canister trolley18is used to lift the canisters22as well as handling of tools and lift grapples required to remove and replace the cask lids78and to move the spent fuel canisters22. Additionally, the canister trolley18can interlock with the shielded bell trolley14so that the canisters22can be transferred from one cask82to another cask while the shielded bell16protects the area from radiation given off by the spent fuel canisters22. It is also apparent from the above disclosure that the hoist system44does not carry the shielded bell16. Thus the hoist44does not have to be rated for more than the capacity of the heaviest spent fuel canister22because it does lift or lower the shielded bell16. It is further apparent from the above disclosure that the canister extraction process can be automated. Leaving the shielded bell16in a fixed position and moving the canister trolley18with respect to a fixed position enables the canister trolley18and the hoist44to be very accurate and reliable when the bridge24does not have to move. Thus, the canister trolley18is isolated from the shielded bell16allowing them to move independently without one limiting movement of the other and when necessary the two are linked together to provide the accuracy needed to extract and manipulate spend fuel containers22.

From the foregoing disclosure and detailed description of certain preferred embodiments, it will be apparent that various modifications, additions and other alternative embodiments are possible without departing from the true scope and spirit of the present invention. The embodiments discussed were chosen and described to provide the best illustration of the principles of the present invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the benefit to which they are fairly, legally, and equitably entitled.