Patent Publication Number: US-10770192-B2

Title: Cask handling system and method

Description:
RELATED APPLICATIONS 
     This Application is a continuation of U.S. patent application Ser. No. 15/818,303 filed on Nov. 20, 2017, which is a continuation of U.S. patent application Ser. No. 13/497,737 filed on Nov. 5, 2012, now U.S. Pat. No. 9,824,781, which is a national phase application of International Application Number PCT/US2010/50397 filed on Sep. 27, 2010, which claims the priority benefit of U.S. provisional Patent Application No. 61/245,881 filed on Sep. 25, 2009, the disclosures of which is expressly incorporated herein in its entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to systems and methods for handling massive containers and, more particularly, handling storage casks for nuclear waste material. 
     BACKGROUND OF THE INVENTION 
     Nuclear power plants are required to have systems and methods for removing spent nuclear fuel from the plants so that it can be stored and/or processed. The spent nuclear fuel is typically stored in casks. While the current systems and methods may handle the casks, they have a number of problems. Existing systems have little documentation, require significant man hours, and use out-dated technology. These current methods also require a relatively large number of single use components that makes these systems expensive and difficult to maintain. Accordingly, there is a need in the art for improved systems and methods for handling casks containing nuclear waste material. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system and method that overcomes at least some of the issues of the related art. Disclosed is a method for removing spent nuclear fuel comprising the steps of moving a cask below a penetration using a transporter, raising the cask from the transporter using a handling mechanism engaging only upper trunnions of the cask so that the cask self-aligns with the penetration using gravity, securing the cask to the penetration, inserting the spent fuel into the cask, unsecuring the cask from the penetration, and lowering the cask onto the transporter using the handling mechanism. 
     Also disclosed is an upper handling mechanism for handling a sent nuclear fuel cask having pairs of upper and lower trunnions. The mechanism comprises, in combination, a fixed position frame, a tool movable in the vertical direction relative to the frame, a plurality of hydraulic cylinders for vertically moving the tool relative to the frame, and a pair of paddles pivotably attached to the tool for selectively engaging the upper trunnions of the cask. 
     Also disclosed is a method for removing spent nuclear fuel comprising the steps of moving a cask below an opening at a first station using a self-powered transporter, rotating the cask from a horizontal orientation to a vertical orientation at the first station, moving the cask below hoist at a second station using the self-powered transporter, moving the cask below a penetration at a second station using the self-powered transporter, raising the cask from the self-powered transporter to the penetration, securing the cask to the penetration, inserting the spent fuel into the cask, unsecuring the cask from the penetration, and lowering the cask onto the self-powered transporter. 
     Further disclosed is a self-powered vehicle for transporting a spent nuclear fuel cask having pairs of upper and lower trunnions. The vehicle comprises, in combination, a body, an upender secured to the body for holding the cask and moving the cask between vertical and horizontal orientations, and a plurality of independently driven and independently steered wheels on each lateral side of the body. 
     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 systems and methods for spent nuclear fuel removal. Particularly significant in this regard is the potential the invention affords for providing an, reliable and effective system and method for handling spent nuclear fuel casks. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and further features of the present invention will be apparent with reference to the following description and drawings, wherein: 
         FIG. 1  is a perspective view of fuel building or facility having a cast transfer system according to the present invention. 
         FIG. 2  is a plan view of the cask transfer assembly of  FIG. 1 . 
         FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 . 
         FIG. 3A  is an enlarged, fragment view showing a portion of  FIG. 3 . 
         FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 2 . 
         FIG. 4A  is an enlarged, fragment view showing a portion of  FIG. 4 . 
         FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 4 . 
         FIG. 6  is a perspective view of a cask transporter of the cask handling system of  FIGS. 1 to 5 , wherein the cask is held in a horizontal orientation. 
         FIG. 7  is a perspective view of the cask transporter of  FIG. 6 , wherein the cask is held in a vertical orientation. 
         FIG. 8  is a perspective view of the cask transporter of  FIGS. 6 and 7 , wherein an upender is in a horizontal orientation without holding a cask. 
         FIG. 9  is perspective view of a tire propulsion/support system of the cask transporter of  FIGS. 6 to 8 . 
         FIG. 10  is a perspective view of a rotary actuator of the tire propulsion/support system of  FIG. 9 . 
         FIG. 11  is a perspective view of a hydraulic motor of the tire propulsion/support system of  FIG. 9 . 
         FIG. 12  is a perspective view of a tire assembly of the tire propulsion/support system of  FIG. 9 . 
         FIGS. 13A to 13D  are bottom plan views of the cask transporter of  FIGS. 6 to 8 , wherein different turning conditions are illustrated. 
         FIG. 14  is a perspective view of a diesel powered generator set of the cask transporter of  FIGS. 6 to 8 . 
         FIG. 15  is a perspective view of a safety catcher of a hydraulic lift system of the cask transporter of  FIGS. 6 to 8 . 
         FIG. 16  is a perspective view of an upper cask handling station of the cask handling system of  FIGS. 1 to 5 . 
         FIG. 17  is a perspective view of a lower seismic restraint of the cask handling system of  FIGS. 1 to 5 . 
         FIG. 18  is a perspective view of a penetration upper hatch of the cask handling system of  FIGS. 1 to 5 , wherein a hatch cover is closed. 
         FIG. 19  is a perspective view of a penetration upper hatch of  FIG. 18 , wherein the hatch cover is partially open. 
         FIG. 20  is an enlarged fragmented view of a portion of the penetration upper hatch of  FIGS. 18 and 19 . 
         FIG. 21  is a schematic view of piping in a cask handling room of the cask handling system of  FIGS. 1 to 5 . 
         FIG. 22  is an electrical schematic view of a control system of the cask handling system of  FIGS. 1 to 5 . 
     
    
    
     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 cask handling system as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes 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 cask handling system illustrated in the drawings. In general, up or upward refers to an upward direction within the plane of the paper in  FIG. 3  and down or downward refers to a downward direction within the plane of the paper in  FIG. 3 . 
     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 improved 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 preferred embodiments. 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 to 5  illustrate a fuel building  10  having a fuel transfer or cask handling system according to the present invention  12 . The illustrated cask handling system  12  handles a spent fuel storage cask  14  through the process of removing spent nuclear fuel from the fuel building  10  including providing an unloaded cask  14 , preparing and opening the cask  14 , loading spent fuel into the cask  14 , sealing the cask  14 , and removing the loaded cask  14  from the fuel building  10 . The cask handling system  12  includes a self-powered mobile cask handling vehicle or cask transporter  16 , an upper handling mechanism  18 , a penetration cover  20 , a seismic restraint  22 , and a valve system  24 . 
     A preferred method according to the present invention for removing spent fuel assemblies from a fuel building  10  and transporting them to on-site facilities for the next stage of disposal is as follows. First, a complete empty cask  14  is placed onto the cask transporter  16  in the horizontal or vertical orientation by an overhead gantry crane. The cask  14  is securely attached to an upender structure  26  of the cask transporter  16  which can pivot the cask  14  about a horizontal and laterally extending pivot axis  28  so that the cask  14  can be moved between horizontal and vertical positions. Precise positioning of the cask  14  onto the cask transporter  16  is not necessary because locating the cask  14  with respect to a fuel pool  30  and penetration  32  in the building  10  is accomplished by the other equipment as described hereinafter. With the cask  14  positioned in its horizontal position, the cask transporter  16  drives to the fuel building  10 . The cask transporter  16  has the ability to drive anywhere on site and can be operated by an on-board driver or by radio remote control. The cask transporter  16  has a hydraulic power system that is powered by a self-contained motor and generator  36  (no external tractor or tugger is required). When inside the cask transfer facility  10 , the cask transporter  16  has the ability to run on remote power via an umbilical cord. The cask transporter  16  enters a cask loading hall or fuel hall  34  of the fuel building  10  and aligns itself with a pair of parallel, embedded floor rails  40 . When the cask transport  16  is aligned with the imbedded floor rails  40  and completely with the cask loading hall  34 , isolation doors are shut and temporary power is connected to the cask transporter  16  via the umbilical cord. Because the cask transporter  16  is aligned with the rails  40 , side-to-side or lateral positioning of the cask transporter  16  is automatically accomplished and precise positioning from front to back in a linear direction within the cask loading hall  34  can be obtained. 
     The upender  26  on the cask transporter  16  repositions the cask from its traveling horizontal position to its vertical position, engages upper seismic constraints, and positions the cask  14  under a first processing station which is the cask prep station  42 . At the first station  42 , a shock absorbing cover, protection lid, and fixing flange of the cask  14  are each manually removed using an auxiliary crane located in the fuel building  10 . Personnel are located above the fuel hall  34  and access the cask  14  through a hole  44  in the floor. This provides a controlled and safe work area for removing the covers and lids from the cask  14 . The cask components are stored on sliding shelves located adjacent the hole  44 . Once bolts for the biological lid of the cask  14  have been removed, the cask transporter  16  is moved by radio control to the second station which is the biological lid station  46 . 
     At the second station  46 , a hoist  48  with a grapple device is manually operated, aided with cameras, to maneuver the grapple to engage and remove the biological lid of the cask  14 . With the biological lid moved out of the way, a thorough visual inspection of all seals and sealing surfaces of the cask  14  is conducted by an operator using cameras. Redundant piping and hosing is connected into ports of the cask  14  at this time. The cask transporter  16  is then moved by radio control to the third station which is the cask loading station  50 . 
     At the third station  50 , the cask transporter  16  locates the cask  14  under the penetration  32  of the fuel pool  30  and personnel disconnect the cask  14  from the cask transporter  16 . In this position, the cask is located under the upper handling mechanism  18 . Hydraulically powered paddles  52  of the upper handling mechanism  18  have key slots  54  which are extended and slide over upper trunnions  56  of the cask  14  to lock the cask  14  to the upper handling mechanism  18 . With the cask  14  securely held by the paddles  52 , the cask transporter  16  is backed away and a vertical guide system or seismic restraint  22  rises from the floor and engages lower trunnions  58  of the cask  14 . As the cask  14  is raised by the upper handling mechanism  18  from the cask transporter  16 , the lower trunnions  58  engage a keyed structure  60  in the vertical guide system  22 , preventing a swinging pendulum motion in a seismic event. The cask  14  is lifted up by the upper handling mechanism  18  and proper alignment of mating surfaces is visually verified using cameras. A multi-stage redundant bladder system engages an inner face of the cask opening. Mechanical locking means engage and the paddles  52  locate the cask  14  in alignment (similar to a plumb bob) using gravity. The redundant bladder system is then inflated to secure the seal. After successful docking of the cask  14 , the penetration  32  is filled with borated or de-mineralized water. Using vent and drain valves, the cask  14  is filled with water and pressure is equalized on the two sides of the penetration upper cover  20 . At this time, all personnel are exited from the loading hall  34 . 
     The penetration upper cover  20  is opened and remains opened and monitored by cameras as spent fuel is loaded into the cask  14 . As the cask has been loaded with spent fuel and the cameras verify that the spent fuel bundles are located properly, the penetration upper cover  20  is closed. The area below the penetration upper cover  20  is drained, rinsed with de-mineralized water and allowed to dry. The water in the cask is lowered to the necessary level for the biological lid. The cask transporter  16  is then moved back to the cask loading station, the bladder seals are depressurized and the cask  16  is lowered from the seal and onto the cask transporter  16 . The paddles  52  retract from the cask  14  and mechanical means secure the cask to the cask transporter  16 . The cask transporter  16  then moves the cask  14  back to the biological lid station  46  where the biological lid is placed back onto the cask  14  and the remaining cask restraints are secured. Personnel are then allowed back into the loading hall  34 . 
     Redundant piping and hosing is disconnected from the cask ports and all ports are properly sealed. The cask transporter  16  then moves the cask  14  back to the cask prep station  42 . Remaining cask components are reassembled and properly engaged on the cask  14 . Remaining cask constraints are secured and the cask  14  is down ended to its horizontal orientation. Radiological tests are performed and decontamination is performed as necessary. The doors in the loading hall  34  are opened and temporary power to the cask transporter is removed, that is, the umbilical cord is removed. The cask transporter  16  then drives out of the fuel building  10  under its own power. The cask transporter  16  takes the cask  14  to a handling area for final disposal. 
     As best shown in  FIGS. 6 to 8 , the illustrated cask transporter  16  is a diesel/electric, self-propelled, wheeled vehicle that transports the storage cask  14  which weighs 125 tons. The illustrated cask transporter  16  includes sixteen wheels  62  which are driven by industrial hydraulic motors  64  with integral brakes for total control and greater flexibility. The illustrated cask transport  16  has four pairs of wheels  62  on each lateral side of the cask transporter  16 . A diesel powered electric generator  36  provides power to operate the cask transporter  16 . The cask transporter  16  preferably is designed to safely hold a TN32 cask  14  during a seismic event. A dynamic multiplier of 1.15 is preferably considered for impact loading during normal operations. Hydraulic fluids are preferably suitable for outdoor operation at 0 degree Fahrenheit and are preferably non-flammable with a flashpoint &gt; or =100 degrees Fahrenheit. High pressure hydraulic lines are preferably secured and protected to prevent whipping in the unlikely event of failure. Hydraulic systems preferably carry the rated load, including a 15% hoist factor. Calculated safety margins for cylinder buckling and hoop stress are preferably a minimum of 2:1 versus the buckling load limit and the material yield strength respectively. The cask transporter  16  is sized and shaped so that it is stable to ensure that an upset will not occur during normal or off normal events. 
     The illustrated cask transporter  16  can shuttle loaded and unloaded storage casks  14  between the fuel handling hall  34  and any other accessible location at the site. The illustrated cask transporter  16  has a unique turning mechanism and wheel design allows significantly more maneuverability over prior systems. The cask transporter  16  preferably includes the following features: twenty year design life; all weather design; OSHA compliant design; auto-rotating, fully loaded on concrete or other hard surface; key start switch; switch type speed control; diesel fuel tank of about forty to fifty gallons; heaters (sump pump, fuel tank, and hydraulic reservoir); dead man controls (brakes applied upon release of control, loss of fluid pressure, or loss of power); traverse speed of 0.4 mph+/−0.05 mph on level ground; manual lowering capability without power; warning lights and audible alarm (30 foot range); provisions to prevent uncontrolled lowering; portable fire extinguisher; float battery charger; access ladders and fall protection; control panel capacity nameplate (rated load, empty weight, temperature limitations); ability to traverse two inch lip of obstructions at the site; durable outdoor paint system; and non-slip walkway surfaces. 
     The illustrated cask transporter  16  includes a body  66  which is the main weldment vehicle frame. The body  66  is the center structure that ties the entire machine together. It is constructed from welded plates and structural shapes. The body  66  serves as the mounting point for all other systems of the cask transporter  16  and also serves to support the cask  14 . The body  66  is preferably a weldment constructed primarily from mild steel and structural shapes (ASTM A572 and A500C with yield strengths of 50,000 psi and welded per AWS D1.1). Welding complies with AWS D1.1. The structure is evaluated for both static and seismic load requirements. 
     As best shown in  FIGS. 9 to 13 , rubber tire propulsion/support systems of the illustrated cask transporter  16  include the wheels  62 , rotation mechanisms  68 , and hydraulic drive units  70 . The illustrated eight pairs of dual-rubber wheels  62  (four pairs on each side and sixteen total wheels) are mounted on the underside of the body  66 . The wheels  62  are preferably foam-filled aircraft tires such as those available from Michelin or equivalents that are designed for high capacities and high speeds. Because the cask transporter  16  is traveling at very low speeds, these wheels  62  are conservatively designed for this function. The foam-filled tires ensure that there is never a flat tire that could challenge the safety of the fuel assembly with a transported cask  14 . Each dual tire set is driven by the hydraulic motor  64 . Based on a dirt surface, a rotational speed of 3.056 rpm and 5% grade, each hydraulic motor  64  is approximately 5HP and is independently controlled by the PLC. Each dual wheel set is independently steered using commercially available rotary actuators  72 . The rotary actuators  72  are used to pivot a joint where a conventional mounting proves impractical due to space, weight, or motion restrictions. These rack and pinion actuators  72  provide high torque output, zero leakage drift-free positioning, and excellent shock load resistance. These types of wheel sets are highly reliable. A control system provides the signals to drive, turn and rotate the wheels  62 . Using a PLC that independently controls each of the dual wheel assemblies, the cask transporter  16  can turn as needed and drive around the entire site. The steering system provides the operator with the capacity to rotate the cask transporter  16  on itself, that is pivoting about its center (best shown in  13 D). 
     As best shown in  FIG. 14 , the illustrated cask transporter  16  includes the diesel powered generator  36  located at the rear of the body  66  to provide electrical power. The generator  16  includes a diesel engine, generator, diesel fuel tank, and all of the equipment to support the operation of the engine and generator and are all contained within a frame of a module  74 . The engine and generator are sized to manage the most demanding function as limited by the control system. The diesel engine drives the generator, which is selected to provide 460V/3-phase/60 Hertz power to the cask transporter. This electricity powers and electric motor/hydraulic pump module for the lift function of the upender  26  and either another electric motor/hydraulic pump module for the propel function of the wheels  62  or two electric propel motors. Noise suppression systems are included with the system to reduce the dba levels workers are exposed to below OSHA limits. Operation of the cask transporter  16  requires that each function (propulsion, upending, etc.) be operated separately to maximize safety. 
     As best shown in  FIG. 15 , the illustrated cask transporter  16  employs automatic drop protection to prevent uncontrolled lowering of the cask  14  during any system failure, such as loss of pressure to the cylinders or other catastrophic failure of the lifting system  26 . The cask transporter  16  preferably is equipped with a separate safety system. This safety system holds the cask  14  in a safe condition in the unlikely event that a hydraulic cylinder fails or other structural parts of the lifting system  26  fail to function. Separately mounted from the hydraulic cylinder, the safety system employs two commercially available SITEMA safety catchers  76 . Conventional locking devices fitted to the hydraulic presses (such as locking bolts or latches) often operate at the top, or a few more positions. Form fitting systems have a gap in safety between where power is disrupted and the hole slide hits a locking point. These obvious disadvantages are avoided by using SITEMA safety catchers  76 . These safety catchers  76  prevent the cask  14  from crashing down at any stage of ascent or descent, are mechanically safe and reliable, and do not have a ratchet. A high safety standard, along with improvements in productivity, is achieved through: the load is supported on a holding shaft separate from the cylinder; the SITEMA safety catcher clamps without a ratchet, so that a safe clamping condition is attained throughout the entire stroke and a productively increase is offered as the actual stroke can be limited to the length that is absolutely necessary; the clamping system is held open by hydraulic or pneumatic means so that when pressure drops, the cask  14  is immediately secured; the energy of a falling or sinking load is used to generate the clamping force which only happens if the load starts to move downward from the secured position (when the safety catcher is without pressure). In this case, the cask  14  is securely stopped almost instantly with help of the self-intensifying clamp movement; and SITEMA braking operations are fully operational at all cylinder speeds and usually a deceleration of 1 to 3 g (acceleration due to gravity) is achieved and the resulting braking distance is not more than a few centimeters. 
     The illustrated cask transport  16  includes operator control system  78  including control panels and a generator module console. The operator control system is ergonomically mounted on the top deck  18  of the cask transporter  16  to provide user friendly operation from a swiveling operator&#39;s chair  82 , in a location providing an unobstructed view of cask handling operations. Next to the operator&#39;s chair  82  is a stationary control console that has auxiliary indications. The operator&#39;s chair  82  can rotate approximately 270 degrees and automatically reverses the joy stick controls based on the orientation of the chair  82 . The operator&#39;s control is provided with a protective cover to prevent weather damage. Hydraulics are operated by manipulation of solenoid valves that port fluid to extend and retract from commercially available hydraulic cylinders, such as those available from Parker. Counter-balance and pressure compensated flow valves ensure that the hydraulic system only operates when commanded, and is fail safe on the loss of pressure from leaks or pump failure. Operating pressure will be displayed on the stationary console plus additional warning lights for low hydraulic level and other fault conditions. The speed of the cask transporter  16  is controlled by a joy stick that is located on the operator&#39;s chair  82 . Based on the position of the joystick, a 0-10 VDC signal is sent to a proportional valve that drives the eight hydraulic motors  64  either in forward or reverse. The joystick is spring-returned to neutral (0 position) to act as a dead-man switch. Steering is controlled by a multi-axis joystick that feeds a proportional signal though a PLC, such as those available from Allen Bradley, or equivalent that separately steers the eight pairs of wheels  62 . The PLC program individually controls the wheels  62  so that they are rotated correctly based on their position on the cask transporter  16 . Hydraulic fluid drives the eight rotary actuators  72 , such as Parker HTR series hydraulic rotary actuators, with electronic feedback to properly position the wheels  62 . A separate 75 HP motor drives a 28 gallon piston pump that is connected to a 80 gallon HPU reservoir for steering and propulsion. The tank comes with heat exchanger and heaters to accommodate any environmental extreme. Strainers and filters are preferably provided. 
     Controls for the cask transporter  16  are designed to be fail-safe, so that loss of power will shut down the system and prevent an uncontrolled movement of the cask  14 . All safety interlocks and controls of the cask transporter  16  are hard wired between the specific relays, drives, circuit breakers, and other electrical equipment. The control system is designed per NEC standards and mounted within a minimum of NEMA 4 enclosures. Wiring is mounted in rigid conduit except for necessary flexible connections and at the interface between the conduit and the equipment. The cask transporter  16  is also grounded for personnel and equipment protection. 
     The upender  26  is powered by dual hydraulic brake-motors coupled top a planetary gear set to drive a pinion/bull gear ensemble. Encoders are integrated into each drive and set up as a master/slave configuration to ensure the upending is done in unison. Rotation is about a point approximately within three inches or about 80 centimeters of the center of gravity, therefore necessary power is kept to a minimum. In case of failure of one drive system, the other brake motor can hold the cask  14  by itself and can be driven to lower the cask  14  back down to a safe position. In addition, the fuel building crane can also be used to lower the cask  14  in case of a catastrophic failure. To prevent shock to the fuel assembly and cask  14 , shock absorbers have been incorporated into the bed for safety. The upender  26  can be extended approximately forty inches or about one meter so that the cask  14  can be raised to the upper elevation at the cask preparation station  42 . Dual eight inch double acting cylinders lift the cask  14  using non-flammable hydraulic fluid at a pressure of greater than 80% of the maximum operating pressure. Safety catchers  76  are incorporated into the cylinders so that a failure of a cylinder rod will nit be catastrophic. On loss of power, the cylinders can be manually lowered to put the cask  14  in a safe condition. When the cask  14  is on the upender  26 , it is captivated in several locations. On the bottom of the cask  14 , an “L” shaped platform  84  is hydraulically operated to latch the lower portion of the cask  14 . This prevents the cask  14  from sliding and keeps the trunnions  56 ,  58  in their respective pockets in the bed. A second hydraulic assembly latches the rear upper trunnion  56  and prevents the cask  14  from tipping forward under even the worst anticipated seismic event. The locks fail safely in case of loss of power or loss of hydraulic fluid. On the bottom of the upender carriage is an alignment or guide tool or assembly. This hydraulically activated alignment assembly lowers onto the rails  40  that are embedded in the floor of the fuel hall  34  to guide the cask transporter  16  in precise alignment. This assembly is only a guide and does not have driven wheels. A single hydraulic cylinder is used to raise (store) and lower (engage) the assembly. 
     At the first or cask prep station  42 , the cask  14  is moved to the vertical position. The cask transporter  16  aligns the cask  14  with the hole  44  in the ceiling of the fuel hall  34  and the fuel building crane is used to perform cask component removal/replacement work. The cask  14  is positioned so that the crane can take each lid out of the cask  14 , bring it up through the hole  44  and place it on a rolling shelf. Operators can easily access the top of the cask  14  to remove bolts and prepare the cask for insertion of the fuel assemblies. 
     After the biological lid&#39;s bolts are removed, the cask  14  proceeds to the second or biological lid station  46  to have the biological lid removed and the seals inspected. Using the Hevi-Lift Hoist  48  or the equivalent mounted onto a bridge and trolley assembly, a grapple can be maneuvered to attach to the biological lid and remove it from the cask  14 . The Hevi-Lift Hoist  48  is a 7.5 to 10 ton unit that has multiple single failure proof components in order that the lid cannot be dropped onto spent fuel. The hoist  48  has multiple brakes (CD brake, load brake and regenerative braking) coupled with a duel rope system to ensure that the breakage of rope will not drop the load. The hoist  48  is operated with a variable frequency drive, such as a Smartorque drive, or equivalent for precise positioning. The bridge and trolley are very short spans providing approximately one foot (or about 0.3 meters) of travel in the X and Y plane. The bridge and trolley are over sized to allow for a 10:1 design factor based on ultimate strength and are operated using a standard starter and relay rather than VFD. The grapple is designed to meet the requirements of ASME N14.6-1993, “Special Lifting Devices for Shipping Containers Weighing 10,000 pounds or More” and ASME BTH-1, “Design of Below the Hook Lifting Devices”. The grapple is designed to interface with the round lug on the top of the geological shield. The device has jaws that meet the standard configuration profile. The jaws of the grapple pass through the opening (ID) in the canister lifting lug and come to rest on the top of the lid. As the weight of the grapple shifts from being held by the hoist due to being carried by the lid, the linkage of the system of the grapple moves downward and disengages the mechanical latch. The mechanical latch works by using a T-shaped rod and cam profile that has the ability to move up and down, and to rotate. Similar to operating a ball point pen, the cam mechanism in the latch alternates from extending and retracting the T-shaped rod. When the grapple travels downward, it activates the latch to move the wedge configuration to drive the jaws outward until full stroke is obtained (approximately 2 inches). Once the grapple is attached to the lug, it is mechanically locked and cannot open as a result of operator error. This is efficient because the mechanical principle of wedges (incline planes) gives a mechanical advantage based on the weight of the load lifted. The jaws cannot disengage while lifting the load. When disengaging the cask, the reverse sequence occurs. On the downward motion of the grapple, the weight of the unit applies a vertical force on a linage series which in turn applies a horizontal force to retract the jaws. This all occurs simultaneously leaving the jaws retracted and the grapple in the unlatched position. The grapple can then be lifted free of the lid. 
     Once the biological lid has been removed, the cask transporter  16  moves the cask  14  to the third or upper cask handling station  50  where the cask  14  is positioned against a penetration seal. As best shown in  FIG. 16 , the upper cask handling station  18  includes a weldment  86  that has four hydraulic cylinders  88  that raise and lower the cask engagement tool  90 . The cask engagement tool  90  includes the two pivoting paddles  52  with the key slots  54  that fit over the upper trunnions  56  on the side of the cask  14 . With the cask  14  aligned under the upper cask handling station  18 , the ten inch diameter cylinders  88  lower the paddles  52 , and an electro-mechanical actuator pivots the paddles  52  down about their horizontal pivot axes and over the trunnions  56 . The cylinders  88  then rise slightly to ensure proper fit and take some initial cask load. The cask  14  is disengaged from the cask transporter  16 , which backs away from the cask  14 . With the entire cask  14  suspended from the upper cask handling station  18 , the cylinders  88  raise the cask  14  into the penetration seal. The cylinders  88  rise together based on a linear encoder in each rod that feeds back to the control system to ensure proper alignment. In addition to the linear encoders, the upper cask handling system  18  ensures proper alignment with guide tubes that are positioned at each of the four corners. Gravity ensures the cask  14  hangs straight down since the round trunnions  56  seated in the round key slots  54 . As the cask  14  is raised, it interfaces with a stainless steel penetration lower flange that has a multi-level seal system. Once the cask  14  is seated, the seals are filled with air to seal the interface between the penetration lower flange and the cask  14  so that there is no leakage even with the pressure resulting from a significant water column. In between the seals are leak detection sensors that provide assurance that the main and backup seals are tight. With the cask  14  properly seated, tapered shear pins are inserted between the stationary structure and the lift frame  18  to lock the cask  14  in place. This provides assurance that even during a seismic event, the cask  14  will not become disengaged from the penetration seal. 
     Once the cask  14  has been raised and seated on the penetration seal, the lower seismic restraint  22  engages the lower trunnions  58  of the cask  14  to securely hold the assembly. This carbon steel weldment  92  is mounted permanently to the floor in the fuel hall  34  below the penetration  32 . As best shown in  FIG. 17 , the seismic restraint  22  includes two horizontally moving arms  94  that extend out at the height of the trunnions  58 . The cask transporter  16  straddles the lower seismic restraint  22  when it delivers the cask  14 . After the cask transporter  16  has released the cask  14  and backed out of the way, the restraint  22  actuates to engage the trunnions  58  using an ACME screw to bring the arms  94  over the trunnions  58 . A separate locking plate operated by a mechanical-electrical actuator locks both arms to the cask  14  so the unit can handle seismic forces in all three planes. Once the cask  14  is filled with fuel assemblies, the lower seismic restraint  22  releases the cask  14  by shifting locks and retracting the arms  94  from the cask  14 . The cask  14  can then be lowered onto the cask transporter  16  and the loaded cask  14  can be removed from the fuel hall  34 . 
     As best shown in  FIGS. 18 to 20 , the penetration upper hatch or cover  20  includes a rim  96 , a cover  98  with latches  100 , o-rings  102 , latch cylinders  104 , a hatch cylinder  106 , a hydraulic power unit  108 , piping  110 , and leak sensors  112 . The rim  96  is a stainless steel weldment sized to fit the hole at the upper penetration  32 . It houses the o-ring seals  102 , provides a base for installation of the hatch cylinder  106  and the latch cylinders  104 , and offers a pivot for the cover  98 . The cover  98  is a stainless steel weldment. It mates with the rim  96  at the pivot points, through the hatch cylinder  106 , through the latch cylinders  104 , and at the o-ring seals  102  where it provides sealing. The o-rings  102  are fabricated o-rings of about a 1.0 inch cross section. The o-rings  102  are fabricated to three different diameters to provide three concentric sealing surfaces. Material is compatible with the water of the spent fuel building and a high radiation application. The latch cylinders  104  are stainless steel water hydraulic cylinders of 3.25 inch bore and 3.5 inch active stroke. They are front flange mounted and rear flange retrained to decrease deflection when operating. The rod is 2.0 inches in diameter with a ¾×15 degree end taper. This taper forces the cover tight against the o-ring seals providing a positive seal. The hatch cylinder  106  is a stainless steel water hydraulic cylinder of 4.0 inch bore, 16.0 inch active stroke, and 1.5 inch diameter rod. It is mounted to the rim  96  at its base end and to the cover  98  at its rod end providing the force to open and close the cover  98 . The hydraulic power unit (HPU)  108  is a motor driven water hydraulic pump which provides flow and pressure to operate the cylinders  104 ,  106 . It incorporates water hydraulic valves to operate the latch cylinders  104  or the hatch cylinder  106 . Piping  110  to the cylinders  104 ,  106  is stainless steel tubing fabricated to the dimensions of the SFB transferring flow and pressure from the HPU  108  to the cylinders  104 ,  106 . The leak sensors  112  are switches which provide a signal to the system when sensing a leak through the o-rings  102 . 
     Operation of the penetration upper hatch cover  20  begins with the cover  98  closed and locked. When it is desired to open the cover  98 , the operator activates the valve operating the latch cylinders  104 . These cylinders  104  retract, pulling their rods (pins) from the cover latches  100 . Sensors confirm when the cover is unlatched. The operator then activates the hatch cylinder  106 . This cylinder  106  pulls on the cover lever and opens the cover  98 . The cover rotates from zero degrees through about 105 degrees at full open. Sensors confirm that the cover is fully open and the penetration  20  is ready for passage of the fuel assemblies. Fuel is passed through the penetration  20  until the spent fuel cask  14  is full, and must be removed. To close the penetration  20 , the operator activates the hatch cylinder  106  to close the cover  98 . The cylinder  106  moves the lid  98  until the CG is past center and then restrains the lid  98  as it lowers down onto the o-ring seals  102  of the rim  96 . A hatch cylinder pin may be manually pulled to allow the cover  98  to close in an emergency. The illustrated embodiment has three o-rings  102  arranged circumferentially about the hatch opening. These o-rings  102  seal on their tops and bottoms against the cover  98  and the rim  96 . The operator activates the latch cylinders  104  which drive their tapered rods (pins) into the latches  100  of the cover  98 . This taper further forces the lid  98  tight against the o-rings  102  ensuring their complete seal. Sensors indicate when the latches  100  are fully engaged. Since there is no residual force attempting to release the latch cylinders  104 , the lid  98  will remain closed and sealed during any unforeseen conditions. Hand pumps can release the latches  100  during emergency situations. 
       FIG. 21  illustrates piping of the cask handling room  50 . The piping system includes valves for filling the cask  14  including venting, valves to spray down the annulus and cask  14  with de-mineralized water, and a pressure gauge and level indicator for the cask  14 . Double valves are provided so that a failed unit can be isolated. Most of the valves are manual and located outside the fuel hall  34 . Those valves and gauges inside the fuel hall  34  that are not accessible when personnel are not allowed in the vicinity are electrically operated. 
       FIG. 22  is an electrical schematic of the control system of the cask handling system  12 . The cask handling system control is housed in a floor mounted NEMA  12  enclosure/main control console. The enclosure/main control console contains two PLCs, an operator interface and all video camera controls with LED flat screen monitors. The control system employs two independent PLCs. The first PLC is an Allan Bradley ControLogix PLC or the equivalent and is dedicated to the control and operation of the cask handling system  12 . The second PLC is an Alan Bradley dual processor GuardLogic PLC or the equivalent and is used for monitoring all safety related devices and functions. This PLC, when used with safety I/O blocks is safety certified SIL-3 per IEC 61508. Both PLC processors will communicate over an Ethernet/IP network. The operator interface consists of an Allan Bradley Panelview Plus LED touch screen monitor or the equivalent that is in direct communication with the operational PLC over an Ethernet/IP network. This interface is programmed with various operator control screens as well as screens for operational interlocks, fault messages, and troubleshooting aids. All motion is interlocked in the PLC program to assure all operations are performed in the proper sequence. A hard wired safety emergency stop pushbutton is located at each of the three working stations as well as at the remote main control console. When any of the emergency stop buttons are pressed, all motion relating to the cask handling system will stop. The camera system will consist of several strategically placed video cameras for monitoring various cask loading operations and overall cask handling status. Where necessary, cameras will be radiation hardened and incorporate a pan/tilt/zoom feature. Camera joystick controls along with the associated flat panel color viewing monitors are located at the remote man control console. Once inside the fuel hall, the cask transporter is powered via a plugged in power cable and control and control of the cask transporter will be accomplished by means of a control chief radio remote control box. In addition, the main control console PLC will monitor various functions of the on board cask transporter PLC over a connected network communication cable. 
     It is apparent from the above disclosure that the improved cask handling system  12  utilizes a number of innovations to reduce the time to perform the task and significantly reduces the number of components. The sealing process where the cask  12  is interfaced to the spent fuel pool is simplified to allow gravity to help align the system to prevent any leakage. The self-powered mobile cask handling vehicle  16  handles the cask  14  at a number of stations and transports the casks  14  throughout the site. 
     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.