Shipping container for radioactive material using safety closure devices

[57] ABSTRACT

A shipping container for radioactive materials which not only adequately shields the material from endangering a person handling it, but also protects the material during shipment. A series of interrelated, coacting, components must be operated in a step-wise manner before the container can be properly and safely closed.

[56] References Cited

Claims, 16 Drawing Figures

UNITED STATES PATENTS

3,549,888 12/1970 Conlon..............................250/106 S

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PATENTED JAN 91973

3.710,121

SHEET 1 OF 3

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PATENTED JAN 91973

3,710.121

SHEET 2 OF 3

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PATENTED JAN 91973

3,710,121

SHEET 3 OF 3

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3,710,121

SHIPPING CONTAINER FOR RADIOACTIVE MATERIAL USING SAFETY CLOSURE DEVICES The present invention relates to shipping containers and, more particularly, to shipping containers suitable for transporting radioactive material.

As the art of nuclear power develops, the need for refueling reactors and transportation of spent fuel elements from the reactor to a fuel reprocessing establishment has increased. Similarly, the use of nuclear charges in other fields, including medicine, has increased in recent years. These operations present a considerable problem since the nuclear elements give off a large amount of heat, which must be dissipated, and also emit large amounts of radiation, which must be shielded against. Inasmuch as the nuclear elements must often be transported considerable distances by rail, tender or truck, a possibility exists that accidents of varying degrees of seriousness will occur en route. The container must, therefore, be built strongly enough so that in the event of any unforeseeable contingency the public health and safety will not be endangered by the escape of radioactive materials or unnecessary radiations.

In order for the shipping container to be a complete safeguard against injury by the radioactive material it is most important that the container have built-in safety features to insure that the material is always properly located within its shield, and that the container cannot inadvertently be left open or the container lid unlocked. So that these desirable results may be obtained, the container of the present invention has a number of interrelated and cooperating components which must be operated in sequence. Spring-urged latches, sliding bolts, key ways and rotating projections all engage with one another, in step fashion, to secure the various com- ³⁵ponents together, thereby eliminating inadvertent mistakes which would result in unnecessary risk to personnel.

As a further precaution, the invention provides for an inner container designed specifically for use in the shipping unit. This container is a screw cap, steel canister with a steel collar having a horizontally projecting pin. In use, the radioactive material is placed into this container which is then placed within a shield. By means of a special wrench, the screw cap is turned, the container twists until the collar pin engages a vertical plate to stop further twisting. In this manner, the cap is easily applied while the radioactive material is safely shielded from the handler. This process may be reversed for safely removing the source from the shield.

It is, accordingly, an object of the present invention to provide for the safe shipping of radioactive charges.

Another object of the present invention is the provision of a shipping container for radioactive material.

Another object of the present invention is the provision of a shipping container having a number of built-in safety features.

Still another object of the present invention is the provision of a shipping container having a number of interrelated cooperating components.

Yet another object of the present invention is the provision of a shipping container having a plurality of components which must be assembled in a stepwise, prearranged manner.

Another object of the present invention is the provision of a shipping container in which the components have interlocking elements.

Other objects and many of the attendant advantages of the present invention will become more readily apparent as the same becomes better understood by reference to the following detailed description of an ex5 emplary embodiment, when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 is an overall perspective view of the inner ¹⁰ load-locking container with a portion cut away;

FIG. 2 is a perspective view of the inner-load locking container positioned in an outer shipping box;

FIG. 3 is an enlarged perspective view of the inner container which holds the radioactive material;

¹³ FIG. 4 is a partial sectional view taken through the entire container and box;

FIG. 5 is an enlarged sectional view of the lead shield when there is no inner container present with radioac₂₀ five material;

FIG. 6 is an enlarged sectional view of the shield when the inner container is present;

FIG. 7 is a view taken along the line 7—7 of FIG. 6 showing the top part of the inner container;

₂₅ FIG. 8 is a sequence of views of the head assembly handle from open to close positions;

FIGS. 9a and 9b are views showing how the container lid will not shut if the head assembly handle is not closed;

₃₀ FIG. 10 is a view showing the container lid closed;

FIG. 11 is a view showing the safety latch on the container lid;

FIG. 12 is a plan view of the cover plate;

FIG. 13 is an elevation view of the cover plate;

FIG. 14 is a plan view of the head handle; and

FIG. 15 is an elevation view of the head handle.

Referring now to the drawings there is shown in FIG. 1 an overall view of the inner load locking container with the outer shipping box in which it is placed not 40 being shown. In this view the various safety features have been activated to close the container. The shield is normally already in a box and is part of it; all that remains is usually to close the lid of the box and lock it. FIG. 2 shows the container nesting within a shipping 45 box 20, but the lid of the box has not been closed. An alternate procedure is to first close the container and then place it in the shipping box.

The inner container, which actually holds the radioactive material, is shown in FIG. 3 and it consists 50 of a cylindrical body portion 22 that measures about 2 inches, approximately, in length and is made of heavy gauge steel, e.g. a casting, or like material. Around the topmost end of body portion 22, and forming an integral part thereof is a collar 24, the collar at one place ⁵⁵ on its outer periphery having a projection pin 26 extending outwardly therefrom. The inner container is completed by a screw cap 28 which has an inner thread that mates with a like thread on the outer end of the cylindrical body 22, above the collar 24, so that a tightly sealed inner container is provided when the cap and body are screwed together.

In the sectional view of FIG. 4 there is shown the middle container constituting a shield 30 which, in this embodiment, is in the form of a lead cylinder, or else which may be a steel container filled with lead, to effectively absorb any radiation which may be emanating through the walls of inner container 22. Down through

3,710,121 the center of the lead shield 30 there is a hollowed out portion which has the general shape of an inverted cone, except that the tapering sides are in the form of steps with periodic horizontal portions alternating with the vertical portions as the taper narrows. The widest part of the cavity is at the top, with the narrowmost part at the bottom, such bottom part being the right dimensions to accurately receive the inner container 22.

To complete the shielding of the inner container 22 there is provided a lead plug 32 which has the same general shape as the tapering, hollowed out, portion in the shield body 30, except that it does not extend more than about half-way down into the cavity. The stepped sides of the plug 32 precisely match the stepped sides of the cavity so that when the plug is in place it acts like a large stopper to seal the inner container 22 in the cavity of the shield body 30.

Across the lower end of lead plug 32 there is a metal plate 34 (see FIGS. 4, 5 and 6), through the center of which is drilled a hole 36 to loosely accommodate a cylindrical rod 38 and permit the rod 38 to easily slide back and forth axially through the hole. Across the lower end of cylindrical rod 38, and integrally attached thereto is a plate 40 which extends substantially across the cavity at that point and which is wider than the screw cap 28 for the inner container 22. Coiled around the periphery of the cylindrical rod 38 is a coil spring 42 which normally urges the rod and plate 40 downwardly toward the inner container 22. On the upper sides of plate 34, and extending into the body of the lead plug 32, is a square channel 44 which is larger than hole 36 in the plate 34 and aligned therewith, so that the cylindrical rod 38 moves up into the channel 44 as it moves against the pressure of the spring 42.

Attached to the upper end of the rod 38, and positioned so that it moves freely in the channel 44, there is provided a C-shaped square member 46 which cooperates with a latch 48 located in the lead plug 32; the latch 48 functions transversely to the axis of channel 44 and C-shaped member 46. Latch 48 has a pin 50 with a triangular shaped bolt 52 at the inner end shaped to slide into the C-shaped member 46, latch 48 being urged toward C-shaped member 46 by a coil spring 54 wrapped around the pin 50.

Turning briefly to FIGS. 5 and 6 it will be noted that there is a bar 56, imbedded in the leadshield 30 just to the side of where the inner container collar 24 is to be located. The purpose of the bar 56 is to serve as a stop for the projection pin 26 on the inner container 22 and thus the pin 26 helps to hold the inner container 22 from turning while the screw cap 28 is being screwed either on or off.

Across the top of the middle container, and forming a closure therefor is a cover plate 58 (see FIGS. 1, 4 and 12) which is fixed to and an integral part of the middle container 30. The cover plate 58 is circular in configuration and has a hole 60 the precise size of the lead plug 32, so that the cover plate can fit down over the plug, with the top of the plug projecting up through the hole. Attached to the top of the cover plate 58, and essentially diametrically opposite each other at 180° are two Z-bar hold downs elements 62 for holding a handle in place, as will be described hereinafter. Also extending upward from the cover plate is a short guide pin 64. Extending through the cover plate 58 there are provided two generally rectangular holes 66 and 68, spaced 180° opposite to each other, for fastening a carrying handle, as will be described below.

In order to lift and remove the lead plug 32, to gain access to the inner container 22 there is provided a carrying handle 70 (FIG. 14) having a circular portion 72 which is the upper portion of the lead plug 32 extending above the hole 60 in the cover plate, the circular portion 72 encircling the plug (see FIGS. 1 and 4) and being pinned thereto. A hand handle 74 extends across circular portion 72, and two arcuate fan-shaped plates 76 and 78 are attached to the circular portion 72 and extend outwardly therefrom. Through the countermost area of fan-shaped plates 76 and 78 are drilled circular holes 80 and 82 for respective use of a pair of latches 84. Attached to the outer edge of one fan-shaped plate 76 there is a vertically projecting wedge member 94, the function of which will be described more fully hereinafter.

In order to ship the container, it is enclosed in a shipping box 20 which may be made of wood, or other material capable of supporting heavy objects and also able to withstand adverse stress applied during shipping. The box 20 has a hinged lid 86 with a downwardly projecting lid rest 88 near the center thereof. Also extending downward from the outer edge or hinged lids 86 there is a C-shaped bracket 90 (FIG. 4) with the face of the C turned inwardly toward the shipping box 20. Forming part of the lower arm of the C-shaped bracket 90 there is an inclined plane latch 92.

As to the operation of the invention and the assembly of the components so that the various safety locks will fasten in the proper sequence, the radioactive material which must be shipped is first placed in the inner container 22, and the container is then lowered to the bottom of the recess or cavity, bored or otherwise provided in the center of lead shield 30, itself preferably already located within the shipping box 20. Once the inner container 22 is at the bottom of the recess, screw cap 28 is put on the container to seal it tight by means of a special magnetic wrench which is turned to engage the threads. When the wrench is turned, the container 22 twists within the cavity until the projection pin 26 on collar 24 engages a vertical steel plate, or bar stop 56, which is part of the inside surface of the shield cavity. The steel plate or stop 56 acts to prevent movement of the cap 28 for the twisting inner container and thereby permits the cap to be tightly screwed on. In this manner, the cap is easily applied while the radioactive material is safely shielded from the handler.

The cover plate 58 (FIG. 4), consisting of several essential features enables the following operations to occur. The plug 32 or closure head is picked up by its handle 70 and placed into the cavity in the lead shield 30 through the central opening 60 in the cover plate 58, guided by the short vertical pin 64 in cover plate 58 projecting about 1½ inches above the top surface thereof alongside the cavity. As the head or plug is lowered into the cavity with the bolt 50 protruding into its vertical groove of the shield wall, the plate 40 on the bottom side of cylindrical rod 30, and urged downward by coil spring 42, comes to rest on screw cap 28 of the inner container 22. When the head is lowered to its final resting position, cylindrical rod 30 is pushed upward a prescribed distance, carrying the C-shaped

3,710,121 member 46 with it, up into the channel 44 in the lead plug 30. The upward motion of rod 30 and C-shaped member 46, permits triangular bolt 52, on the inner end of pin 50 and urged horizontally by oil spring 54, to be retracted into the C-shaped member (FIG. 4) and out of its groove in the side of the plug 30.

Once this is achieved, the entire head may be twisted to a fixed position where it is automatically locked to the shield 30 and cover plate 58 by the spring-loaded latches 84 protruding through holes 66 and 68 in the cover plate 58 (FIGS. 4 and 12). Since holes 66 and 68 are of different sizes, one of the latches 84 will enter hole 66 first and then later the other latch will protrude through hole 68. As the twisting of the head progresses, the fan shaped plates 76 and 78 (FIGS. 8 and 14) of the handle structure 70 move under the horizontally extending arms of the Z-bar hold down elements 62 on the cover plate 58 (See FIG. 1). These Z-bar hold downs serve not only as a stop limit for the twisting of the head, but they also function to hold the head securely to the shield 30.

When the shield and head assembly are integrally joined together in the heavy shipping box 20, its lid 86 is closed down. It should be noted from FIGS. 9 and 10 that lid 86 will not close unless handle 74 has been rotated its prescribed distance so that lid rest 88 will pass beside handle 74 and not abut the top of it. This safety feature assures that the container is properly secured with the self-locking latches 84 engaged in holes 66 and 68.

Once the lid rest 88 is allowed to pass beside handle 74, lid 86 will close permitting the C-shaped bracket 90 to move along a wedge member 94, over the edge of cover plate 58 and extend along the side of the shipping box 20 until the inclined plane latch 92 rests alongside 58. Once the lid is shut it may be locked by a padlock (not shown) as the final locking means which guarantees that the radioactive material is securely and positively encased within the shield and shipping box.

Returning briefly to FIG. 5 it should be obvious that if, for some unknown reason, the radioactive material and inner container 22 were to be left out of the shield, then through the operation of the sequential safety features of the invention the shipping box could not be shut and locked. In this situation, the plate 40 would not be raised to the dotted line position, C-shaped member 46 would not be raised and thus the triangular bolt 52 on pin 50 could not enter C-shaped member 46, and cover assembly 32 would not be twisted while in the recess in the shield because bolt pin 50 had not cleared the vertical groove in the shield wall.

In addition, if the head assembly 32 were omitted, the box lid could not be closed without direct efforts to circumvent the interlocking sequence. The reason for this is that when plug 32 is left out, the wedge 94 which enables latch 92 to retract and not abut on cover plate 58 is not present. Also if the cap 28 were not screwed on completely the pin 50 would not retract and plug 32 could not be rotated and the box could not be closed and locked. For the system to work the container 22 must be in the shield; cap 28 must be screwed on completely, then plug 32 must be lowered in guided by pin 64 and plug 32 must be rotated to its locked position. Only then can the lid be closed.

From the above description of the structure and operation of the invention it is clear that the device offers many improvements and modifications over other similar prior art devices. The invention discloses a shipping container for radioactive material which is sturdy in construction, provides complete shielded protection to personnel handling the material, and which comprises a plurality of interrelated, interlocking components which must be activated in a stepwise prearranged fashion before the shipping container can be closed and locked.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. For example, while the disclosed embodiment is said to have a cylindrical body portion 22 of 2 inches, it is understood that it may be of any desired practical size which depends only on the size of the source to be shipped; once the container size is established, the shield and closure head can be designed to fit accordingly, and the entire device can be made small to fit a quart container or larger than a 50-gallon drum. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.