US3819066A

US3819066A - Apparatus for lowering and raising a shipping cask for spent nuclear fuel into a storage pool

Info

Publication number: US3819066A
Application number: US00179713A
Authority: US
Inventors: C Jones
Original assignee: Transfer System Inc
Current assignee: UNC NUCLEAR INDUSTRIES Inc A CORP OF; Pacific Nuclear Systems Inc
Priority date: 1971-03-15
Filing date: 1971-09-13
Publication date: 1974-06-25
Anticipated expiration: 1991-06-25
Also published as: IT958700B; FR2130194A1; CH551074A

Abstract

Apparatus and method for lowering and raising a shipping cask into a storage pool for receiving spent nuclear fuel assemblies is described. The apparatus comprises a secondary support system installed in the pool for vertical movement of the cask in the pool. The secondary support system is capable of fully supporting the cask in case of failure of the usual overhead hoist system. A feature provides for lowering and raising of the cask in at least two steps, enabling addition of an extension piece to the overhead crane hook after the cask has been at least partly immersed to avoid immersion of the crane hook, sheaves and cable into the storage pool. Still another feature is provision of a substantially water-tight removable shroud for the cask preventing direct contact of the cask exterior with the storage pool fluid to avoid contamination thereof.

Description

United States Patent [191 Jones 1 APPARATUS FOR LOWERING AND RAISING A SHIPPING CASK FOR SPENT NUCLEAR FUEL INTO A STORAGE POOL [75] Inventor:

[73] Assignee:

Cecil R. Jones, Hamden, Conn.

Related US. Application Data [63] Continuation-impart of Ser. No. 124,228, March 15,

1971, abandoned.

[52] US. Cl. 214/16 B, 187/68 [51] Int. Cl B65g l/04, G2lc 19/32 [58] Field of Search..... 214/16 B, 17 R, 17 B, 17 C,

[56] References Cited UNITED STATES PATENTS 750,597 1/1904 Carnes 187/68 3,533,911 10/1970 Fortescue et a1. 176/30 [4 June 25, 1974 Primary Examiner-Robert G. Sheridan 1 5 7] ABSTRACT Apparatus and method for lowering and raising a shipping cask into a storage pool for receiving spent nuclear fuel assemblies is described. The apparatus comprises a secondary support system installed in the pool for vertical movement of the cask in the pool. The secondary support system is capable of fully supporting the cask in case of failure of the usual overhead hoist system. A feature provides for lowering and raising of the cask in at least two steps, enabling addition of an extension piece to the overhead crane hook after the cask has been at least partly immersed to avoid immersion of the crane hook, sheaves and cable into the storage pool. Still another feature is provision of a substantially water-tight removable shroud for the cask preventing direct contact of the cask exterior with the storage pool fluid to avoid contamination thereof.

12 Claims, 11 Drawing Figures PATENIEDJUN25I974 v 3.819.066

sum 2 or 5 I --Z8a l I 2e 28 INVENTOR CECIL R. JONES BY k M'LI/W ATTORNEY PIIIIEIIIIIIIIM 3.819.066 A sum 3 or 5 I I I II|I III HOIST II III U IZO oz- PRESSURE Fig.7 88 TIE? I I I? I I I I I I I I I I I I I I I I I 183 I as i I I I2I I I I 1 ENT CEC R. J ES ATTORNEY PATENIEDJUN 2 55174 SHEET 0F 5 INVIIUOR. CECIL R. JONES ATTORNEY PATENTED June 5 1924

sum

5 or 5 INVENTOR. CECIL R. JONES ATTORNEY:

APPARATUS FOR LOWERING AND RAISING A SHIPPING CASK FOR SPENT NUCLEAR FUEL INTO A STORAGE FL This invention relates to apparatus and a method for lowering and raising a shipping cask for spent nuclear fuel into and from fuel storage pool. This application is a continuation-in-part of my prior application, Ser. No. 124,228 filed Mar. 15, 1971 now abandoned.

BACKGROUND OF THE INVENTION Spent nuclear fuel assemblies after removal from power-generating nuclear reactors are stored in a fuel storage pool usually located adjacent the reactor well. Disposal of such fuel involves its placement in a shipping cask, followed by shipment of the cask to a fuel reprocessing plant. Such casks are usually made of lead, and have a sufficient length to accommodate the conventional fuel assemblies. A typical cask having an inside diameter of about 3 to feet, an outside diameter of about 5 to 8 feet, and a length of about to 17 feet, would weigh from about 70 to 120 tons. To maintain a protected environment, the cask is lowered into the fuel storage pool, the spent fuel assemblies placed into the cask and the cask closed, all while under water, and then the loaded cask removed from the pool, decontaminated, and made ready for shipping. To prevent exposure of the spent fuel rods which are still radioactive, generally the pool has a depth more than the combined length of the cask and the fuel assemblies, for example forty feet in depth. Lowering and raising of the cask is accomplished by the. usual overhead crane and attached hoists.

The above procedure involves a number of serious problems. Firstly, there is no double load path for the cask during its lowering and raising into and from the pool. Should the hoist cables fail, the falling cask could have catastrophic effects, such as for example cracking of the pool floor causing draining of the shielding pool water and exposure of the radioactive fuel assemblies stored therein. Secondly, the pool water is often contaminated due among other things to leaking fuel rods in the spent fuel assemblies. This contaminates the cask surface, requiring its decontamination after removal from the pool. Thirdly, most existing power stations do not have sufficient headroom in the reactor building to accommodate a hoist capable of handling a solid extension piece of some twenty feet in length attached to the crane hook in addition to the fifteen or so feet of height of the cask. What this means is that the hook, sheaves and cables of the hoist attached to the cask necessarily become immersed in the pool, causing their contamination. Decontamination of such equipment, especially cables, is extremely burdensome.

The main objects of the present invention are apparatus and methods for handling a shipping cask to be loaded with spent fuel assemblies in a storage pool providing one or more of the following:

1. continuous double load path for cask support providing protection against accidental failure or operator mishandling of the primary support overhead hoist system;

2. avoidance of immersion of the overhead crane hook, sheaves and cables into the storage pool fluid; and

. 3. avoidance of direct contact between the cask exterior and the storage pool fluid.

SUMMARY OF THE INVENTION These and other objects of the invention as will appear hereinafter are achieved by installing in the stor age pool a secondary cask support system for lowering and raising of the shipping cask and capable of fully supporting the cask at all times in case of failure of the primary overhead hoist. A further feature of the invention is the provision of at least one intermediate stop arrangement in the pool cask support system enabling the cask to be lowered and raised in two or more steps whereby an extension piece can be added to the overhead crane hook after the cask has been partially lowered into the pool to avoid immersion of the crane hook, sheaves and cables into the storage pool fluid. Still another feature of the invention is a cable-less secondary cask support system affording reduced maintenance. A further feature is a secondary cask support employing hydraulic cylinders wherein the direct cask support is secured to and movable with the cylinders rather than to the pistons. A further feature of the latter construction is a hydraulic cylinder construction whose length need be no greater than substantially onehalf the pool depth. Still a further feature of the invention is the provision of a substantially water tight removable shroud surrounding the cask to prevent direct contact between the pool fluid and the cask outer surface to avoid contamination thereof.

Other features and advantages of the invention will I become apparent from the following detailed descriptionof several embodiments thereof taken in conjunction with the accompanying drawings wherein:

DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic front elevation view of a first embodiment of the apparatus of the present invention for lowering a spent nuclear fuel shipping cask into a storage pool.

FIG. 2 is a plan view of the apparatus shown in FIG. I.

FIG. 3 is a side elevation view of the apparatus shown in FIGS. 1 and 2.

FIG. 4 is an enlarged, fragmentary elevation view taken along line 44 of FIG. 1.

FIG. Sis an enlarged, fragmentary elevation view taken along line 55 of FIG. 3.

FIG. 6 is an enlarged sectional view taken along line 66 of FIG. I to illustrate the counterbalancer and velocity limiter employed in the apparatus shown in FIG. 1.

FIG. 7 is a diagrammatic front elevation view of a second embodiment of the present invention.

FIG. 8 is a perspective view of the upper part of the apparatus shown in FIG. 7.

FIG. 9 is a fragmentary view of part of the platform and cylinder support of the apparatus of FIG. 7.

FIG. 10 is a partial front elevation view of the apparatus of FIG. 7 with the platfonn at mid position.

FIG. 11 is front partially sectional, partially elevation view of the shroud surrounded cask.

DESCRIPTION OF CABLE EMBODIMENT Illustrated in FIGS. 1-3 is one form of an apparatus 10 of the present invention for lowering a spent nuclear fuel shipping cask 15 into a conventional fuel storage pool P containing relatively pure water W. Conventionally, an irradiated fuel shipping cask is of lead depleted uranium or other high density shielding material. It is also well-known that water W in the fuel storage pool P also serves as a radioactive shielding material for spent nuclear fuel stored in the pool, and may also be included for shielding purposes in the shipping cask 15.

The apparatus comprises four upright, tubular water-tight posts -23 of suitable corrosion-resistant material, such as stainless steel, which serve as cylinders of a hydraulic system. The feet of the posts 20-23 are fixedly secured by suitable means to the walls surrounding'the pool P and to the floor of the fuel storage pool P. Suitable braces 24 are employed to reduce flexure of the posts 20-23. Disposed within the posts 20-22, respectively, in water tight engagement therewith, are counterbalancers and velocity limiters 25-27 which constitute the piston part of the hydraulic system. The counterbalancer and velocity limiter for the post 23 is not shown, but it is similar to the counterbalancer and velocity limiter 26 shown in FIG. 6 for the post 21.

Mounted on the upper ends of the posts 20-23, respectively, for free rotation are pulleys 30-33 by means of brackets -38. Trained around the pulleys 30-33 'are suitable stainless steel cables 40-43 respectively, with plastic covers. Suitable retainers 34 (FIGS. 4 and 5) on the brackets 35-38 hold the cables 40-43 onto the associated pulleys 30-33. One of the runs of the cables 40-43 are disposed within the posts 20-23 and are attached to the piston counterbalancers and velocity limiters 25-28, respectively. The counterbalancers and velocity limiters 25-28 are movable in the vertical direction within the posts 20-23. As shown in FIG. 6, seals and guides, such as seals 28a on the .counterbalancer and velocity limiter 26 provide sealing engagement with the inner wall of the associated post. On top of the posts 20-23, respectively, and surrounding the cables 40-43, respectively, are suitable seals (FIG. 5) for maintaining the upper ends of the posts 20-23 relatively water tight. Water or a suitable fluid F (FIG. 5) is disposed in the posts 20-23 below the seals 4548 and above the counterbalancersv and velocity limiters 25-28.

The other runs of the cables 40-43 extend out of the posts 20-23 and are attached to a shipping cask platform support for supporting the same. The fuel pool cask support 50 is made of suitable material, such as stainless steel. As shown in FIG. 2, the shipping cask support 50 is located between the posts 20-23. Seated on the shipping cask support 50 is the cylindrical fuel shipping cask 15.

Under no load condition, the shipping cask support 50 is in the elevated position (FIGS. 1 and 2) and the counterbalancers and velocity limiters 25-28 are at the base of the associated posts 20-23. Formed on.the upper portion of theshipping cask 15 are

suitable trunnions

56 and 57. A conventional overhead crane, not shown, with a cable, sheave and grapple or hook engages the

trunnions

56 and 57 to support, to lower and to raise, and to transport the fuel shipping cask 15. Initially, the shipping cask platform 50 is in the no load position and the crane with the cable and hook lowers the shipping cask 15 to seat upon the shipping cask support 50. Prior to or at this time, a conventional lid or cover is removed from the shipping cask 15. Then suitable stops (not shown) are removed from under the support 50. As the overhead crane releases the cask load, it slowly sinks on the platform into the water pool under its own weight until the platform 50 engages interrnediate plunger seats or stops 60-63 and comes to a dead stop. The system is designed so that a suitable fraction, for example, approximately -80 percent of the cask load, is taken up by the secondary support system leaving the remaining of 20-30 percent of the load to be carried by the overhead crane and hoist. This is readily controlled by adjustment of the velocity limiters. With the cask partly immersed but stopped before the

trunnions

56 and 57 have entered the water, as shown in phantom in FIG. 1, an operator then removes the crane cable and hooks from the

trunnions

56 and 57 of the fuel shipping cask 15 and attaches one end of a conventional extension piece or sling, not shown, to the free end of the crane cable and hook. The other end of the extension piece with a hook thereon is attached to the trunnions of the fuel shipping cask 15 to once again support the same from the crane, not shown. If desired, a short extension piece can be attached to the cask trunnions. This allows the cask to be lowered to a deeper level before stopping and adding the long extension piece. Now, the shipping cask 15 is first raised slightly by the overhead hoist to permit removal of the plunger seats 60-63 from under the platform, and then lowering of the cask is continued until its base rests on the floor of the fuel pool P via the shipping cask support 50. Spent nuclear fuel is loaded into the shipping cask 15 while the shipping cask 15 rests on the floor of the pool P. After fully loading the shipping cask 15 with spent nuclear fuel, the lid or cover is again fitted on the top of the shipping cask 15.

Mounted on the posts 20-23 a predetermined distance from the respective tops thereof are the remotely activated platform seats, only seats 60 and 61 are shown (FIGS. 4 and 5), respectively, which are operated through air under pressure in a suitable air cylinder, such as air cylinders 62-64. The plunger type seats 60-61 are extended into the downward path of travel of the crane support 50 to support same when an operator remotely activates the associated air cylinders 62-64 to extend the seats 60-61. When an operator remotely removes the air under pressure in the air cylinders, a spring retracts the plunger type seat to remove the same from the path of travel of the downward movement of the crank support 50.

A valve 70 and suitable conduits 71-73 are mounted on the posts 20-23 to control the rate of flow of water trapped in the posts 20-23 between the seals 45 and the counterbalancer and limiters 25-28 from escaping from the posts 20-23 into a suitablefilter, not shown. The valve 70 and the conduits 71-73 are arranged to maintain the same water pressure head in each post 20-23. More specifically, should the fuel shipping cask 15 drop accidentally, because the crane cable breaks, or the hook is inadvertently removed from the

trunnions

56 and 57 of the shipping cask 15, or should the crane lower the shipping cask 15 at too fast a velocity, the water in the posts 20-23 between the seals 45 and the counterbalancers and velocity limiters 25-28, respectively, is trapped to produce a braking action to the dropping or lowering of the cask support 50. The rate at which the trapped water flows through the conduits 71-73 and valve 70 into the filter, not shown, controls the maximum velocity at which the shipping cask and its cask support 50 may be dropped or lowered. Thus, the rate at which the laden shipping cask is dropped or lowered is decelerated by the water trapped in the posts 20-23. The maximum velocity of the dropping or lowering of the laden shipping cask is regulated by adjusting the deceleration control valve 70 to control the rate of flow of trapped water therethrough.

While this embodiment shows a braking action through trapped water, it is apparent that gas, air, or other fluids under pressure may be employed equally as well. For example, a cylinder of gas under pressure can communicate with the posts 23 to supply gas under pressure thereto and a return path to the cylinder of gas of the gas escaping from the posts under a rate controlled by suitable and well-known valves. A pump may be connected to the cylinder of gas for maintaining suitable pressure therein. A pump, not shown, may also be connected to the conduit exiting from the valve 70. During raising of the cask 15 by the overhead hoist, water can be pumped under pressure into the posts driving the pistons 25-28 downward and lifting the platform 50 under the ascending cask to provide additional support therefor and continue the secondary support for the cask while it is being lifted out of the pool. The hydraulic system can be completely closed with its own water supply, or connected to the pool supply to draw water downstream of the pool water supply filter.

DESCRIPTION OF CABLELESS EMBODIMENT The first embodiment above described employs cables which come in contact with the pool water, and which are connected to pistons moving in elongated fixed cylinders anchored to the storage pool. Cables involve certain maintenance problems whose elimination may be preferable at existing reactor facilities. In addition, the construction of water-tight cylinders having the full pool depth may not be feasible in those facilities lacking adequate space for installation of such long cylinders. This second embodiment to be now described and which is my preferred embodiment avoids the use of cables and requires cylinder lengths substantially no more than one-half the pool depth.

Referring now to FIGS. 7-10, the cask secondary support system comprises two generally H-shaped main supports 80 which extend the full depth of the pool and are anchored and fixed therein. The top support for the H-shaped members 80 comprises

elements

81, 82 anchored to the refueling floor 79 and which secure the members 80 in a corner of the pool. Reinforcement at the bottom is provided by struts 83. As is normal, the various parts of this structure that are immersed in the pool are constituted of suitable corrosion-resistant materials, such as stainless-steel. Four hydraulic cylinders 85 are provided. Each cylinder 85 contains a suitable piston 86 and fittings 87, only one of which are shown, at opposite ends of the cylinder for introducing and withdrawing fluid within each cylinder above and below the piston. Pipes 88 connected to the fittings 87 ultimately are connected to suitable valves, pumps, sumps, controls, etc., all well known in the art and therefore not illustrated herein, for the purpose of controlling the fluid pressure above and below the pistons. Each piston 86 is connected to a solid connecting rod 90 which passes through a hole in the

upper support elements

81, 82 and forms an enlarged member terminating in an eye bolt 89. The cylinders are supported by and are suspended from the

upper support elements

81, 82 via the piston connecting rod 90.

A cask platform 91 is supported on the cylinders 85. The cask platform comprises a floor 92, side walls 93, and a rear wall 94 dimensioned to accommodate the cask bottom. The platform corners are each provided with projections 95 which enbrace 97, the adjacent support 80 and each containing a rectangular opening 1 96. All the rectangular openings are oriented in the same direction. Each of the cylinders contain at their top end two oppositely disposed lugs 100. The dimension across the top of the lugs 100 is longer than the short side of the rectangular opening 96 but shorter than the long side of the rectangular opening. Thus in the position illustrated in FIGS. 7-9, the projections abut the lugs 100 and the platform 91 is thus supported by the four cylinders 85. At the bottom of the cylinders 85 are provided two similarly dimensioned lower lugs 101 but oriented at right angles to the upper lugs 100. With the platform load lifted off the cylinders 85, each of the connecting rods 90 can be lifted via their eye bolts 89, rotated 90 until the upper lugs 100 are oriented in the long dimension of the opening 96, and then the cylinder pulled through the opening or the platform lowered until the lower cylinder lugs 101 are contacted, which will now, due to their 90 rotation, be oriented to contact the projection 95. This allows the platform to be supported alternatively by the lower cylin- I der lugs 101 or by the upper cylinder lugs 100. It is also possible to provide projection openings that are square rather than rectangle. In this case, the dimension across the top of the lugs must be larger than the square side but smaller than a diagonal of the square opening. Passage of the lugs through the opening is then obtained by a 45 rotation, and reengagement by the bottom lugs obtained with a second 45 rotation.

Two stop systems for the platform 91 are provided. The first, similar to that of the first embodiment, comprises electrically activated solenoids 103 mounted at the top of the side supports 80 just under the platform 91 in its upper rest position. Until these are activated, the platform 91 cannot descend. Suitable sensors can be located in the platform floor for activating an interlock system (not shown) which prevents removal of the upper stops unless the cask is properly positioned on the platform. .The second stop system 104 is located approximately at the center of the side supports 80, and they may in this case comprise opposite shelves which can be manually activated into or out of the downward path of travel of the platform 91. If desired, an electrically or pneumatically activated stop system can be substituted for the manual system illustrated.

Before the cask 15 is loaded onto the platform 91, it is first preferably seated in a flanged base member 105 (see FIG. 11) whose flange 106 is secured as by a tightening strap 107 to the cask bottom. Secured to the flange 106 is a flexible substantially water-tight shroud 108, for example of plastic reinforced by light metal rings encased in the plastic to provide horizontal support, which can be manually lifted up to cover the whole length of the cask 15 and there secured in position as by straps 109 or the like. Suitable openings may be provided in the sides of the shroud 108 for passage of the

cask trunnions

56, 57. This is readily provided by soft flexible loops 116 as of stretchable material attached to the plastic and stretched over the trunnions to secure the shroud 108 around and seal to the trunnions. Nipples 113 are provided at top and bottom of the shroud 108, which can be connected to hoses and a suitable pumping system, not shown, in order to continuously flush clean water between the cask exterior and the shroud at a slightly'higher pressure than the pool water to prevent the latter from entering any small openings in the shroud and thus contact and possibly contaminate the cask outer surfaces.

Mounted on the refueling floor 79 are two opposed cask guides 115 in the form of channels spaced from each other and above the refueling floor 79 a short distance to accommodate the wide bottom of the flanged base member 105. The cask guide channels 115 extend a short distance in front of the open side of the platform floor 92, which as will be observed from FIG. 7 is located slightly above the plane of the pool curb 116.

In operation, the empty cask is lifted by the overhead hoist, shown schematically at 120 in FIG. 7, and placed into the flanged base member 105, the strap 107 tightened, the shroud 108 lifted up to enclose the cask, the loops 1 16 fitted over the

trunnions

56, 57, the shroud strap 109 tightened, and the nipples 113 secured to its water pumping system, which is activated. Then the cask 15 with attached shroud 108 is lifted and guided into the entrance of the cask guides 115 and then slowly moved to the right of FIG. 7 until the cask is positioned over the center of the platform 91 and then lowered to rest on the platform. Then the usual cask cover (not shown) is removed. I

The guides 115 are provided to prevent tilting ofthe cask on a malfunction of the overhead hoist causing the cask to pitch into the storage pool P. Similarly, the position of the platform floor 91 slightly above the pool rim 116 further ensures that the cask will be slightly tilted in a direction away from the pool should the overhead hoist fail. If the cask is properly positioned on the platform, then the upper stops 103 are removed. The platform load is now carried by the four cylinders 85. By appropriate adjustment of the fluid pressure on opposite sides of the piston.86 to carry approximately 7080 percent of the load, as the overhead hoist 120 releases the load, the platform will slowly descend into the pool advancing the cylinders 85 before it while the pistons slowly ascend within their respective cylinders, with the overhead hoist attached.

Before the pistons reach the top of their respective cylinders, the platform engages the middle stop shelves 104 and comes to a dead stop. The cylinder pressure is now adjusted to cause the cylinders 85 to descend alone to the end of their travel. Next, the connecting rods 90 are lifted by their eyebolts 89, rotated 90, and then the cylinder fluid pressure reversed causing the cylinders 85 to be drivenupward, in this process the upper lugs 100 pass through the long side of the rectangular openings 96 of the platform projections 95. Finally, the lower lugs 101 engage the projections 95 and the cylinders 85 stop their upward movement. The pistons 86 are now located at the bottom of the cylinders (see FIG. 10.). The connecting rods are lifted a small distance to raise the platform 91 above the center stops 104, the shelves 104 now moved out of the downward path of travel of the platform, and the cylinder pressure readjusted again to take up 70-80 percent of the cask load. Again, as the overhead hoist releases the load, the platform continues its descent until it comes to rest on the pool floor 121. As before, the spent fuel elements are loaded into the water filled cask, the cover replaced, and the procedure reversed to lift the cask and the platform out of the pool. That is to say, adjusting the cylinder pressure drives the movable cylinders upward raising the platform with loaded cask to just above the center stop 104. Then the stop is moved outward and the platform rested on the center stop. Next the cylinders are driven downward until the upper lugs 100 pass through the projection openings 96, the connecting rods rotated 90, and the upper lugs brought into contact with the projections 95. Then, the cylinders are again hydraulically driven upward until the platform arrives at its upper rest position shown in FIG. 7, and the upper stops 103 activated to hold the platform. During substantially this entire lowering and raising process, both the platform and-the overhead hoist, each independently capable of taking up the full cask load, have been simultaneously supporting the cask providing a continuous double load cask support system. This also offers the advantage of limiting the strain on the hoist increasing its lifetime.

As was described in connection with the first embodiment, the descending empty cask is stopped by the middle stop 104 just before the

trunnions

56,57 and attached hoist hook, sheaves and cable become immersed in the pool, and at this point an extension sling (not shown) is attached to the hook to avoid immersion of the latter. The sling, which may be soildand of corrosion-resistant material, and is more easily decontaminated, becomes the only hoist part immersed in the water. Thus contamination of the pure water in the pool by a corrosive cable and hook is obviated. Also, the cask shroud 108 has prevented contact of the pool water P with the cask outer surfaces thereby avoiding the necessity for decontamination thereof.

After the loaded cask has been removed from the platform and exited from the pool via the cask guides 115, then the shroud 108 and base 105 may be removed, and the cask loaded on a suitable carrier for shipment to the fuel reprocessing plant.

In this second embodiment, no cables are exposed to the contaminated pool water, and the cylinders need only have a length of about one-half the pool depth.

Both embodiments are adapted for installation in presently existing or designed reactor facilities to provide protection against malfunction of the single overhead hoist system presently used for cask movement.

To avoid the possibility that the cylinder lugs 100, 101 are not properly seated on the projections 95, the latter can be provided with slots for receiving of the lugs, and sensors, if desired, can be located in the slots to prevent movement of the platform if the lugs are not seated in the slots. v

While my invention has been described in connection with specific embodiments thereof, those skilled in the art will recognize that various modifications are possible within the principles enunciated herein and thus the present invention is not to be limited to the specific embodiments disclosed.

What is claimed is:

1. Apparatus for supporting a nuclear fuel shipping cask during lowering into or raising from a storage pool, comprising a mechanical supporting structure at least partly immersed in and anchored to the pool, a cask support platform, fluid pressure responsive means supporting said platform and mounted on said supporting structure to provide vertical movement of the platform along a path from an upper position at the pool top to a lower position at the pool floor, means for controlling the fluid pressure means, mechanical stop means mounted on the supporting structure intermediate the pool top and floor and selectively movable into the vertical path of the platform for arresting downward motion of and supporting the arrested platform, in combination with independent hoist means mounted above the storage pool for engaging and lifting the cask, said mechanical stop being capable of fully supporting the loaded platform enabling disengagement of the hoist from the cask or of the fluid support for said platform.

2. Apparatus as set forth in claim 1 wherein the fluid pressure responsive means comprises hydraulic cylinders supporting the platform, said hydraulic cylinders each containing a piston supported by the supporting structure.

3. Apparatus for supporting a nuclear fuel shipping cask during lowering into or raising from a storage pool, comprising a supporting structure at least partly immersed in and anchored to the pool, a cask support platform, fluid pressure responsive means supporting said platform and mounted on said supporting structure to provide vertical movement of the platform from an upper position at the pool top to a lower position at the pool floor, said fluid pressure responsive means comprising hydraulic cylinders supporting the platform, said hydraulic cylinders each containing a piston supported by the supporting structure, the hydraulic cylinders each having outwardly extending lugs at top and bottom with the bottom lugs oriented in a different direction than the top lugs, the platform comprising apertured projections for engagement by the lugs in a flrst orientation and for passing the cylinder and lugs in a second orientation, means for controlling the fluid pressure means, means on the supporting structure intermediate the pool top and floor for arresting downward motion of the platform, in combination with independent hoist means mounted above the storage pool for engaging and lifting the cask.

4. Apparatus for supporting a nuclear fuel shipping cask during lowering into or raising from a storage pool, comprising a supporting structure at least partly immersed in and anchored to the pool, a cask support platform, fluid pressure responsive means supporting said platform and mounted on said supporting structure to provide vertical movement of the platform from an upper position at the pool top to a lower position at the pool floor, means for controlling the fluid pressure means, means on the supporting structure intermediate the pool top and floor for arresting downward motion of the platform, in combination with independent hoist means mounted above the storage pool for engaging and lifting the cask, a flanged base member having means for securing same to the cask bottom, and a flexible substantially water-tight shroud secured to the flanged base member and adapted to envelope the cask exterior.

5. Apparatus as set forth in claim 4 in combination with channel members mounted at the pool top for guiding the flanged base member secured to the cask onto the platform.

6. Apparatus for supporting a nuclear fuel shipping cask during lowering into or raising from a storage pool, comprising a supporting structure at least partly immersed in and anchored to the pool, a cask support platform, fluid pressure responsive means supporting said platform and mounted on said supporting structure to provide vertical movement of the platform along a vertical path from an upper position at the pool top to a lower position at the pool floor, said fluid pressure responsive means comprising hydraulic cylinders supporting the platform with said hydraulic cylinders each containing a piston connected to and supported by the supporting structure, means for causing said hydraulic cylinders to be selectively movable with and without said platform along said vertical path, means for controlling the fluid pressure means, means on the supporting structure intermediate the pool top and floor for arresting downward motion of the platform, in combination with independent hoist means mounted above the storage pool for engaging and lifting the cask.

7. Apparatus as set forth in claim 6 wherein the selectively movable means comprises means for selectively supporting said platform at at least two different locations along the length of the hydraulic cylinders.

8. Apparatus as set forth in claim 7 wherein the cylinders have a length about one-half the pool depth.

9. Apparatus for supporting a nuclear fuel shipping cask as claimed in claim 1 comprising:

a. a plurality of upright hollow posts;

b. a cable with a run disposed in each of said posts and having a run extending out of its associated post;

c. means for each of said posts around which is trained the associated cable;

weight means disposed in each of said posts for up and down movement, each of said weight means being attached to the run of the cable disposed in its associated post, each of said weight means forming a fluid seal with its associated post;

each of said posts isfluid sealed around its associated cable above its associated weight means, each of said posts having a supply of fluid therein between its fluid seal and its associated weight means; valve means on said posts disposed between the fluid seal of the associated post and its associated weight means for controlling the flow of fluid trapped between the fluid seal of the associated post and the associated weight means and escaping from its associated post; and

g. a shipping cask support attached to the runs of said cables extending out of said posts to be supported thereby.

10. Apparatus as claimed in claim 9 wherein said shipping cask support is disposed between said posts for up and down movement, and further comprising a fuel shipping cask seated on said shipping cask support.

11. Apparatus as claimed in claim 10 and including means with a plunger on each of said posts disposed a predetermined distance from the top of its associated post, said plunger means being activated to move in the downward path of travel of said cask support holding the same against further downward movement within its associated post.

12. The combination as claimed in claim 10 wherein said fuel shipping cask includes means on the upper portion thereof adapted for engagement by the cable of acrane.

Claims

3. Apparatus for supporting a nuclear fuel shipping cask during lowering into or raising from a storage pool, comprising a supporting structure at least partly immersed in and anchored to the pool, a cask support platform, fluid pressure responsive means supporting said platform and mounted on said supporting structure to provide vertical movement of the platform from an upper position at the pool top to a lower position at the pool floor, said fluid pressure responsive means comprising hydraulic cylinders supporting the platform, said hydraulic cylinders each containing a piston supported by the supporting structure, the hydraulic cylinders each having outwardly extending lugs at top and bottom with the bottom lugs oriented in a different direction than the top lugs, the platform comprising apertured projections for engagement by the lugs in a first orientation and for passing the cylinder and lugs in a second orientation, means for controlling the fluid pressure means, means on the supporting structure intermediate the pool top and floor for arresting downward motion of the platform, in combination with independent hoist means mounted above the storage pool for engaging and lifting the cask.

9. Apparatus for supporting a nuclear fuel shipping cask as claimed in claim 1 comprising: a. a plurality of upright hollow posts; b. a cable with a run disposed in each of said posts and having a run extending out of its associated post; c. means for each of said posts around which is trained the associated cable; d. weight means disposed in each of said posts for up and down movement, each of said weight means being attached to the run of the cable disposed in its associated post, each of said weight means forming a fluid seal with its associated post; e. each of said posts is fluid sealed around its associated cable above its associated weight means, each of said posts having a supply of fluid therein between its fluid seal and its associated weight means; f. valve means on said posts disposed between the fluid seal of the associated post and its associated weight means for controlling the flow of fluid trapped between the fluid seal of the associated post and the associated weight means and escaping from its associated post; and g. a shipping cask support attached to the runs of said cables extending out of said posts to be supported thereby.

12. The combination as claimed in claim 10 wherein said fuel shipping cask includes means on the upper portion thereof adapted for engagement by the cable of a crane.