US3414727A - Shipping container for radioactive material including safety shield means - Google Patents

Description

3 Sheets-Sheet 1 BONILLA I v2 8. I N2 SN 8 0 mm INCLUDING SAFETY SHIELD MEANS SHIPPING CONTAINER FOR RADIOACTIVE MATERIAL Dec. 3, 1968 Filed April WT. m

3 Sheets-Sheet 2 F. BONILLA INCLUDING SAFETY SHIELD MEANS SHIPPING CONTAINER FOR RADIOACTIVE MATERIAL Dec. 3, 1968 Filed April 26, 1965 l HI HHP -"h h hh ha l-"" l l l l l ll 4 VIII/ll 4 INVENTOR CHARLES E BONILLA AGENT III'IIIIIIIIIIIIIIIIIIIII'IIIIIIII'I III; .1111. i1"! Illdplllll c. F. BONILLA 3,414,727 SHIPPING CONTAINER FOR RADIOACTIVE MATERIAL Dec. 3, 1968 INCLUDING SAFETY SHIELD MEANS 5 Sheets-Sheet 5 Filed April 26, 1965 m l 1| 1" 6 m w. m. m m OM w m m AGENT construction is of such a nature as United States Patent Oflice 3,414,727 SHIPPING CONTAINER FOR RADIOACTIVE MATERIAL INCLUDING SAFETY SHIELD MEANS Charles F. Bonilla, Tenafly, NJ., assignor to National Lead Company, New York, N.Y., a corporation of New Jersey Filed Apr. 26, 1965, Ser. No. 450,776 20 Claims. (Cl. 250-108) ABSTRACT OF THE DISCLOSURE A shipping container for radioactive material includes a central cavity surrounded by radiation shielding material. The shielding material is in turn surrounded by a safety shield means including an enclosed space having a shield substance therewithin which melts at a temperature lower than the radiation shielding material and is adapted to flow out of the enclosed space through discharge means when subjected to external heat.

The present invention relates to a new and novel shipping container including safety shield means, and more particularly to a shipping container which is adapted to ship spent fuel elements utilized in nuclear reactors and the like.

It is apparent that the present invention may be utilized for shipping any sort of radioactive material and in particular may be utilized for shipping irradiated nuclear fuel elements which are normally mounted on railroad cars and the like for transport from one location to another.

These types of shipping containers are principally designed to safely transport the radioactive material without permitting any radiation damage to personnel who may be in the vicinity of the container and further to retain the fuel elements in proper shielded position even when subjected to rough handling and shocks which normally occur during transport.

With the passage of time, the standards of safety required of such shipping containers have been increased, and a particular feature of the present invention is to provide a safety shield means which protects the container against heat which'may occur from accidental fires and the like. The shield means is particularly designed to provide a thermal insulating means which will enable the container to successfully withstand external high temperatures over an extended period of time without causing a dangerous condition to occur.

The arrangement of the present invention is particularly directed to an arrangement wherein the safety shield means provides an automatic built-in protection against accidental exposure to fire, and furthermore wherein this to provide added mechanical strength and protection to the container which increases the deformation and penetration resistance of the container. I By providing a suitable thermal shield means, any melting of the radiation shielding material which is normally lead within the body means of the container will be minimized, and furthermore overheating of the inner cavity and fuel load will be prevented.

The safety shield means of the present invention is formed about the outer periphery of the body means and includes an enclosed space having a shield substance therein which at high temperatures is capable of flowing out of said space through suitable discharge means provided in the body means. Means is provided for normally preventing the escape of fuel substance from the space defined within the safety shield means, but at high tem- 3,414,727 Patented Dec. 3, 1968 peratures this shield substance readily flows out of the safety shield means to provide one or more air spaces therewithin which provides the maximum degree of heat insulation and effective thermal barrier when subjected to a great deal of heat.

A further advantage of the safety shield means of the present invention is the fact that under fire conditions, the outer surface of the container may be sprayed with water and the like from a fire hose, and the enclosed space of the safety shield means may be filled with water so as to assist in cooling off the container while the fire is being put out.

With the arrangement of the present invention, the safety shield means can be used over and over again after it has been subjected to fire conditions simply by refilling the space of the safety shield means with a suitable shield substance as described hereinafter. This shield substance may comprise a metallic alloy which preferably has a melting point lower than that of the primary radiation shielding material so that it will melt and flow out of the space within the safety shield means when subjected to high temperatures. This shield substance may also comprise a liquid such as water, glycol and the like, or a low melting point salt or similar compound such as sodium hydroxide, and the means for normally preventing escape of the shield substance from the safety shield means may comprise either fusible plug means, which are adapted to melt at predetermined temperatures, or in the case where a liquid is used, pressure relief valve means may be employed which is adapted to open at a predetermined pressure. Also in the case where liquid is used, check valve means may be provided for retaining the liquid in place within the safety shield means.

The safety shield means may extend not only peripherally about the side wall portions of the body means, but may also be incorporated in the structure at the top and bottom of the body means as hereinafter explained.

An object of the present invention is to provide a new and improved shipping container including safety shield means which is particularly adapted for shipping radioactive material and which is so constructed and arranged as to prevent radiation damage to personnel in the adjacent area.

Another object of the invention is the provision of a shipping container including a safety shield means which provides built-in protection against accidental exposure to fire and which operates in an automatic manner to minimize melting of the primary radiation shielding material of the container and which prevents overheating of the inner cavity and radioactive material.

A further object of the invention is to provide a shipping container including safety shield means which not only provides a good thermal barrier 'but which also increases the mechanical stren-gth if the container so as to provide better mechanical protection by increasing deformation and penetration resistance thereof. This increased mechanical strength can be provided, at least in part, by a safety shield alloy which is stronger than the main radiation shielding material which is usually pure lead.

Still another object of the invention is the provision of a shipping container including safety shield means which normally provides greater mechanical strength and which is adapted when subjected to heat to develop an increased resistance to heat.

A still further object of the invention is to provide a shipping container including a safety shield means which defines an enclosed cavity adapted to be filled with water and the like when putting out a fire and in order to enhance cooling of the shipping container.

.Yet another object ofthe invention is the provision of a shipping container including safety shield means which can be used over and over again even after having been subjected to fire conditions.

A still further object of the invention is the provision of a shipping container including safety shield means which is quite simple and inexpensive in construction, and yet which is at the same time efiicient and reliable in use.

Other objects and many attendant advantages of the invention will become more apparent when considered in connection with the specification and accompanying drawings, wherein:

FIG. 1 is a top view of a first modification of a shipping container according to the present invention;

- FIG. 2 is a sectional view taken substantially along line 2-2 of FIG. 1 looking in the direction of the arrows;

FIG. 3 is a sectional view taken substantially along line 3-3 of FIG. 2 looking in the direction of the arrows;

FIG. 4 is a sectional view taken substantially along line 4-4 of FIG. 3 looking in the direction of the arrows; and

FIG. 5 is a sectional view similar to that illustrated in FIG. 2 and showing a further modified form of the invention.

Referring now to the drawings wherein like reference characters designate corresponding parts throughout the several views, a first form of the invention is illustrated in FIGS. 1-4 inclusive. The container of the present invention represents an improvement over a similar container disclosed in copending U.S. patent application Ser. No. 270,212, filed Apr. 3, 1963, noW Patent No. 3,229,096, which corresponds with Belgian Patent No. 646,011, issued Oct. 1, 1964.

The container of the present invention includes a body means indicated generally by reference numeral 20 having a substantially cylindrical outer side wall portion 22. An annular member 24 is secured about the upper end of outer wall portion 22 for reinforcing this area. An annular plate 26 is secured as by welding to the upper portion of members 22 and 24. The upper surface of plate 26 is provided with a circumferentially extending recess 8 within which is disposed an annular gasket 30.

It should be understood that the various components of the present invention are of heavy-duty construction, being formed of steel or the like, except where otherwise specified, so as to readily withstand the loads applied thereto and to support the lead shielding material for the fuel elements.

A plurality of equally spaced blocks 32 being eight in number in the present example are secured as by welding to the undersurface of annular plate 26, each of blocks 32 hav'tng a threaded opening 34 formed therein which is aligned with a threaded opening 36 provided through plate 26. A plurality of threaded studs 38 which are also eight in number are threaded into place within these aligned openings and then tack-welded into operative position. These studs serve as attaching means for securing the closure means in operative position. A pair of guide pins 40 are also supported by plate 26 and extend upwardly therefrom for reception in suitable guide openings provided in the closure means for initially guiding the closure means into proper relationship to receive the threaded studs.

Referring now to the lower portion of the body means as seen particularly in FIG. 2, an annular member 44 is secured as by welding to the lower end of outer wall portion 22 and a ring-like member 46 which surrounds the lower part of wall portion 22 and is secured as by welding thereto. A disc-like plug member 48 is in turn welded to the inner periphery of member 44, member 48 being welded in operative position after the interior of the body means has been filled with a body of radiation shieldingmaterial suchas lead indicated by. reference numeral 50.

A safety means to protect the container and prevent damage to the body means thereof in case of excessive heat and pressure within the container which might tend to melt the body of lead 50 is provided in the form of a substantially frusto-conically shaped expansion plate 51 which is provided with a plurality of spaced holes 52 formed therethrough. Plate 51 is secured as by welding to the inner surfaces of an intermediate side wall portion 60 and the plug member 48. It will be noted that member 60 is also substantially cylindrical and spaced inwardly of the outer side wall portion 22 to define an enclosed space in combination with the upper plate 26 and the lower members 44 and 48, this enclosed spacebeing described in more detail hereinafter. A relatively thin frangible plate 54 is sealed-welded around the edges thereof to the plate 51, and the space 56 defined between plate 54 and the inner surfaces of the container comprises a void which is in effect an expansion chamber such that the body of lead 50 within the body means may expand through the holes 52 in plate 51, causing plate 51 to rupture, whereupon the lead can fiow into the void space thereby providing a safety feature as will be well understood.

A plurality of pad members 62 are fixed to the undersurface of member 44 and to the central portion of a bottom wall portion 64, the pad members being suitably spaced about the structure so as to provide a stable support for the body means and any suitable supporting surface. It will be noted that bottom wall portion 64 is disposed in spaced parallel relationship to members 44 and 48 and defines with such members an enclosed space at the bottom of the body means for a purpose hereinafter described. I I

A plurality of holes'70 are provided through member 44 for assisting in tying the base portion of the body means down when shipping the container. In order to facilitate efiicient heat transfer from the body means to the surrounding atmosphere, a plurality of vertically extending finmembers 72 are secured as by welding to the outer surface of the sidewall portion 22 of the body means.

1 the four corners of member 44 A pair of diametrically opposite reinforcing plates 74 are secured between member 44 and the outer surface of the outer side wall portion 22 of the body means, and four spaced reinforcing plates 76 extend inwardly from v to the outer surface of the outer side wall portion 22'for further rigidifying' the structure and providing a rigid interconnection between the base portion and the side wall'portion of the container. I

Lifting means is provided for the body means in the form of a pair of substantially cylindrical trunnion portions 80 disposed at diametrically opposite sides of the container, these trunnion portions extending inwardly and being rigidly atfixed as by welding to support portions or plates 82 which are in turn securedto the outer surface of the outer side wall portion of the body means. Each of the trunnions is reinforced by a vertically extending plate 84 secured to the outer surface of the outer wall portion of the body means above the trunnions and a similar plate extends below the trunnions and is also secured to the outer surface of t e outer wall portion of the body means. i l

Additional reinforcing and strengthening structure for the trunnions includes inner and outer plates 86'and 88 which are disposed in spaced parallelism with one another and which extend upwardly from member 44. Plates 86 and 88 have openings formedtherethrough which receive the trunnions which are secured in place therewithin. Plates 86 and 88 are interconnected by horizontally extending plate members 90. It is apparent that the over-all arrangement of the various reinforcing members interconnected with the trunnions serve to provide a very sturdy and rigid interconnection whereby the trunnions may be engaged by suitable lifting mechanism for raising and lowering the entire apparatus of the present invention.

Referring again to FIG. 2 of the drawings, the details of construction of the means defining the cavity within the body means are illustrated. A substantially frusto-conically shaped member 100 tapers downwardly and inwardly as seen in this figure, and is secured as by welding to the undersurface of plate 26. An annular member 102 is in turn secured as by welding to the lower end of member 100, and a substantially cylindrical member 104 is secured as by welding to the undersurface of member 102 and depends therefrom. A lower wall portion 106 is secured as by welding to the lower end of member 104 and tapers downwardly to an apex portion 108 which represents the lowermost portion of the cavity. The body means incorporates a vent or drain means including a drain conduit 110 which is in communication with said apex portion and which extends upwardly and outwardly through the body of lead within the body means to terminatein an outer end 112 which has a closure member 114 threaded onto the threaded end portion thereof. Closure member 114 may be selectively removed as desired.

The outer end 112 of conduit 110 is surrounded by a cylindrical portion 116 secured as by welding to the outer surface of the outer side wall portion of the body means. A cup-shaped adaptor member 118 is provided with internal threads which are threaded on the outwardly threaded end portion of cylindrical portion 116. Member 118 is provided with a central metering orifice 120 formed therethrough. An outwardly extending member 122 is secured to the outwardly facing surface of member 118 and is. provided with a standard garden hose thread 124 on the inner central bore formed therethrough which is aligned with the metering orifice 120.

As seen particularly in FIG. 1, a spring-loaded soft seat vapor-tight relief valve is indicated generally by reference numeral 130, this relief valve being in communication with the closure receiving portion defined by member 100 of the body means through the intermediary of a suitable conduit means so as to vent the interior of the body means to atmosphere automatically at a suitable pressure such as 5 p.s.i. A guard means in the form of a substantially U-shaped plate 132 is secured to the outer surface of the outer wall portion of the body means and is disposed in surrounding spaced relationship to the relief valve 130 so as to prevent damage thereto.

As seen in FIG. 2, fuel element basket support means 140 is formed at one side of the cavity within the body means, and second similar support means 142 is disposed at the opposite side of the cavity. Further support means are indicated by reference numerals 144, 146, 148, 150 and 152 which are disposed at spaced intervals about the inner surface of the inner wall portion 104 of the body means. It will be noted that these support means 144-152 inclusive have a substantial vertical dimension for pro? viding adequate support to suitable fuel element baskets and for providing adequate heat transfer and criticality control means (not shown).

It will be understoodthat suitable radioactive material as in the form of fuel elements are supported between such separator plates during shipping operations.

A thermocouple connector 156 may be admitted to the inner surface of the inner wall portion 104 of the body means, the connectorincluding a probe portion 158 which extends downwardly within the central cavity defined within the body means for measuring the temperature of fuel elements disposed therewithin.

The movable closure means of the present invention is illustrated generally by reference numeral 160 and includes a disc-like plate portion 162 and a spaced substantially parallel disc-like plate portion 164, these two plate portions being interconnected by a substantially cylindrical side wall portion 166 which defines with members 162 and 164 an enclosed space for a purpose hereinafter described. A plurality of bushings 168, being eight in number are fixed between plates 162 and 164 and are aligned with holes 170 and 172 formed in members 162 and 164 respectively so as to provide eight spaced openings for receiving the studs 38 previously described. A similar arrangement may be provided for receiving the guide pins 40 so that the closure means can be fitted down upon the remainder of the body means and secured in place by suitable nuts 174 threaded upon the upper end of studs 38.

A substantially frusto-conically shaped member 176 is secured as by welding to the undersurface of plate member 164, and a fiat disc-like plate 178 is suitably secured as by welding to the lower edge of member 176 to form a cavity therewithin. Members 176 and 178 define a downwardly tapered plug portion having a body of lead 180 disposed therewithin, this plug member being adapted to be received within the plug receiving portion defined by member 100 within the body means. As seen most clearly in FIG. 1, plate member 162 is provided with a pair of spaced holes 182 which may be aligned with suitable bushings and corresponding holes provided in plate '164 such that lead may be poured into the space defined by members 176 and 178. After lead has been poured into this space, long members 184 are welded into position in plate 162 to seal the plug portion of the closure means.

A substantially rectangular plate is secured as by welding to the upper surface of plate member 162, plate 190 having a central threaded opening 192 formed therethrough for receiving the lower threaded shank portion of an eye bolt 194. It is apparent that the eye bolt may be utilized for lifting the closure means when in position as shown, and may be removed when the container is being shipped.

A vent means is provided in the closure means, this vent means including a conduit 200 which opens at one end thereof through the member 176, the opposite end of the conduit terminating within an opening formed through plate 162 which is in communication with a tapered threaded hole 202 provided in plate 190 and which is closed oflf by a plug member 204 which is threaded into this tapered opening when desired.

An outrigger means for facilitating handling of the closure means is indicated generally by reference numeral 210, and includes a pair of longitudinally extending side members 212 and 214 which are interconnected by cross brace members 216, 218, 220 and 222, all of these members being rigidly interconnected with one another as by welding or the like. A pair of similar angle members indicated generally by reference numerals 230 include leg portions 232 and 234, the leg portions 232 being suitably secured as by welding to the inner surfaces of side members 212 and 214, the leg portions 232 and 234 each being provided with pairs of spaced holes whichare adapted to be aligned with threaded openings in plate 190 for receiving screw members 236 which are threaded down into the openings in plate 190 for rigidly attaching the outrigger in operative position on the closure means.

Referring now particularly to FIGS. 2, 3 and 4, the construction of the safety shield means defined by and between the outer wall portion 22 and the intermediate wall portion 60 may be most clearly understood. A number of holes 240 are provided through the outer wall portion 22, these holes being spaced circumferentially about the outer wall portion, and also being spaced vertically from one another as seen in FIG. 2. These holes permit filling of the enclosed space defined between walls 22 and 60 with a suitable shield substance, and further permit the shield substance to flow out of this enclosed space at high temperatures. The shield substance is of such composition as to be capable of flowing out of this enclosed space at high temperatures. The shield substance may comprise the same substance such as lead employed as a radiation shielding material. The shield substance is preferably a low melting alloy which is solid at all normal operating conditions as up to approximately 150 C. but will melt as soon as possible above this temperature. The alloy should preferably be an alloy of lead so that it has radiation shielding value as well. This alloy can be stronger than the usual shielding lead, adding deformation and penetration resistance to the container. Lead containing 0.69% of lithium is a preferred alloy, this alloy having a porosity of approximately 10.5 grams per cubic centimeter and a tensile strength above 7,000 p.s.i. This alloy has eutectic properties and its melting point of approximately 235 C. is well below the melting point of approximately 327 C. of the pure lead used as the primary radiation shielding material. This provides the desired result of enabling the shield substance of the safety shield means to melt and run out of the enclosed spaces about the container before the lead shielding material within the body means melts. However, other suitable alloying metals which decrease the melting point of lead, increase the strength, and or increase the wall adhesion, such as other alkali metals, antimony, tin, etc., are also applicable.

As seen most clearly in FIGS. 3 and 4, the shield substance indicated generally by reference numerals 244 substantially fills the enclosed space defined between the outer Wall portion 22 and the intermediate wall portion 60, and in order to improve the operating characteristics of the safety shield means, a plurality of members or layers of material 246 are provided in spaced relationship between these wall portions, these layers of material extending peripherally completely around the body means. Layers of material 246 are formed of a material such as steel which has good heat conducting characteristics for the normal operation when it is desired to transfer the decay heat outward with a minimum temperature drop and which preferably has a shiny surface to enhance its operation as a thermal insulating means for the emergency operation when it is desired to minimize heat flow into the cask from an external fire.

Members 246 are provided with spaced holes 248 formed therethrough so as to permit the shield substance to completely fill the spaces defined between members 246 and the adjacent wall portions of the body means, and to permit this shield substance to readily flow out of the space at high temperatures. Members 246 may be maintained in the desired spaced relationship by integral offset portions 250 formed at spaced parts thereof.

Contrary to the relative thickness shown in FIG. 3 and FIG. 4, the intermediate wall portion 60 may be the principal strength member and made of plain steel, and the outer wall portion 22 may merely provide corrosion resistance and easy decontamination and may be made of thin stainless steel.

As seen most clearly in FIG. 2, the lower portion of the container may also be provided with a safety shield means wherein the enclosed space defined between members 48 and 64 and the peripherally extending side wall portion 260 incorporates a shield means similar to that which extends peripherally about the side wall portion of the body means. Holes 262 are provided in side wall portion 260, and a plurality of members 264 are disposed within the enclosed space at the bottom of the body means, members 264 being similar to members 246 previously described. The entire free space defined between members 264 and the adjacent wall portions of the container are filled with the shield substance 244 previously described.

In a like manner, the movable closure means may be provided with safety shield means by providing a plurality of holes 270 in the side wall portion 166 thereof, a plurality of members 272 similar to members 246 being disposed within the enclosed space defined by various wall portions of the closure means, and here again, the shield substance 244 may be disposed within this enclosed space in the free area thereof between members 272 and adjacent wall portions. An additional hole 276 may be provided to upper plate 162 for adding the shield substance to this last-mentioned enclosed space.

It should be understood that various shield substances may be employed in the enclosed spaces provided about the body means, and that if desired, the layers of heat conducting material disposed within these spaces may also be eliminated so as to simply fill such enclosed spaces with a suitable shield substance. Where the shield substance comprises lead or a lead alloy and the like, the holes provided for allowing the shield substance to flow outwardly under high temperature may simply be filled with the same material.

It is also contemplated that a liquid such as water, glycol or a chlorinated compound may be employed as the shield substance, and in such a case, the holes provided for allowing the shield substance to flow out may be filled with suitable plugs formed of a lead tin alloy and the like. The layers of heat conducting material may be employed with a liquid shield substance if desired.

Referring now to FIG. 5 of the drawings, a modification is illustrated which is particularly designed to employ a liquid such as water which is adapted to boil off when sub jected to high temperatures and to flow outwardly of the enclosed spaces provided about the body means. The construction of this form of the invention is very similar to that previously described, and similar parts have been given the same reference numerals primed.

In this modification of the invention, the enclosed space defined between the outer wall portion 22' and the intermediate wall portion 60' is substantially filled with a liquid such as water indicated generally by reference numeral 290. The holes provided in the outer side wall portion in the previous modification may be eliminated in this form of the invention, and a plurality of spring loaded soft seat vapor-tight relief valves 302 are provided, these valves being supported on the outer portion of the body means and in communication with the enclosed space defined between side wall portions 22' and 60' by means of conduits 304. When the steam pressure developed within the enclosed peripherally extending space about the side wall portion of the body means exceeds a certain predetermined pressure due to high temperature, the water will boil out through these relief valves gradually absorbing heat during this time.

A plurality of check valves 310 are secured to the outer wall portion 22 and are adapted to allow the flow of liquid inwardly into the enclosed space while preventing flow outwardly therefrom. These check valves may be employed for initially filling the enclosed space with the shield material, and furthermore permit water to be forced through the check valve after some of the shield substance has boiled away under the influence of a fire. These check valves thereby permit refilling of the enclosed space and cooling thereof as necessary.

Turning now to the safety shield means provided at the lower portion of the container, the enclosed space defined between members 48', 64' and 262' may be substantially filled with liquid such as water. In this particular position, it may not be feasible to mount pressure relief valves and accordingly, the holes provided in the side wall portion 262' may be closed by fusible plugs 322 formed of a lead tin alloy and the like which are adapted to melt at a predetermined temperature to allow the liquid to fiow outwardlly therefrom.

In a similar manner, the safety shield means provided in the removable closure means may include a body of liquid such as water 324 disposed within the enclosed space of this portion of the safety shield means. Here again, the holes provided in the side wall portion 166' may be closed by plugs 326 which are adapted to melt at a predetermined temperature. It will be understood that when a liquid capable of boiling is employed, it is preferable to provide pressure relief valves which allow the liquid to boil off at a certain setting.

It is apparent that whether pressure relief valves are employed or fusible plugs there is in any event relief means provided for normally closing off the discharge means from the enclosed spaces of the various safety shield means, this relief valve means being adapted to allow the shield substance to flow outwardly of these enclosed spaces at high temperatures.

It is apparent from the foregoing that there is provided according to the present invention a new and novel shipping container including safety shield means and which is particularly adapted for shipping radioactive material such as spent nuclear fuel elements while preventing radiation damage to personnel. The safety shield means of the present invention provides automatic builtin protection against accidental exposure to fire and minimizes melting of the main radiation shielding material and prevents overheating of the inner cavity and the fuel load disposed therewithin. The safety shield means provides additional mechanical protection for the material being shipped, and particularly in the case where a lead alloy is employed as the shield substance, the deformation and penetration resistance of the container is substantially increased. While the container normally has greater mechanical strength at normal temperatures, the safety shield means develops an improved thermal insulation and resistance when subjected to heat due to the fact that the shield material will flow outwardly of the enclosed spaces within which it is disposed. These enclosed spaces may be filled with water while a fire is being put under control to thereby assist in cooling of the container and preventing development of a dangerous condition. A particular advantage of the safety shield means of the present invention is the fact that the shield substance is expendable and may be replaced so that the safety shield means can be used over and over again. The arrangement is at the same time quite simple and inexpensive in construction, and yet is quite effective and reliable in use.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, and since the scope of the invention is defined by the appended claims, all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

I claim:

1. .A shipping container including safety shield means and comprising a body means having a cavity formed therein for receivingmaterial to be shipped, said body means including safety shield means at the outer portion thereof, and spaced outwardly of said cavity said safety shield means including anenclosed area having a shield substance therewithin, said'shield substance at high temperatures being capable of flowing out of said enclosed area, said safety shield means defining discharge means in communication with said enclosed area and the exterior of said container for discharging said shield substance from said enclosed area outwardly of the container to create heat insulation spaces within said enclosed area.

2. A shipping container including safety shield means and comprising body means defining a cavity therewithin for receiving material to be shipped, said body means having safety shield means disposed at the outer periphery thereof and spaced outwardly of said cavity, said safety shield means. defining an enclosed area extending about said body means, a shield substance disposed within said enclosed area, said shield substance at high temperatures being capable of flowing out of said enclosed area, said safety shield means including discharge means in communication with said enclosed area and the exterior of said container for discharging said shield substance from said enclosed area outwardly of the container to create heat insulation spaces within said enclosed area, and closure means for closing the cavity in said body means.

3. A shipping container including safety shield means and comprising body means having a cavity formed therein for receiving radioactive material, movable closure means for closing said cavity, said body means having a pair of spaced side wall portions defining safety shield means spaced outwardly of said cavity and including an area between said side wall portions and extending peripherally about the outer portion of said body means, said area being substantially filled with a shielding substance which at high temperatures is capable of flowing out of said area, one of said side wall portions having discharge means formed therein in communication with said area and the exterior of said container for discharging said shielding substance from said area outwardly of the container to create heat insulation spaces Within said area.

4. A shipping container including safety shield means and comprising a body means having a cavity formed therein for receiving radioactive material, movable closure means for closing off said cavity, said body means including radiation shielding material surrounding said cavity, said body means also including a pair of spaced outer wall portions defining safety shield means including an area between said outer wall portions and extending about the outer periphery of said body means, said area being substantially filled with a shield substance which at high temperatures is capable of flowing out of said area, the outermost wall of said pair of walls having discharge means formed therein in communication with said area and the exterior of said container for discharging said shield substance from said area outwardly of the container to create heat insulation spaces within said area, and means normally preventing discharge of shield substance from said area.

5. A shipping container including safety shield means and comprising body means having a centrally located cavity formed therein for receiving radioactive material, movable closure means for closing said cavity, said body means including an inner wall, an intermediate wall and an outer wall, the area between said inner wall and said intermediate wall being substantially filled with radiation shielding material, the area between said intermediate wall and said outer wall comprising safety shield means adapted to provide good thermal insulating characteristics, said area between said intermediate wall and said outer wall being enclosed and substantially filled with a shield substance which at high temperatures is capable of flowing out of such area, said outer wall having discharge means formed therein for discharging shield substance from said last-mentioned area, said discharge means being in communication with said last-mentioned area and the exterior of said container for discharging said shield substance from said last-mentioned area outwardly of the container to create heat insulation space within said last-mentioned area, and means normally preventing discharge of said shield substance from said area.

6. A shipping container including safety shield means and comprising a body means having a cavity formed therein for receiving material to be shipped, movable closure means for closing said cavity, said body means including safety shield means extending about the outer periphery of said body means and spaced outwardly of said cavity, said safety shield means including means defining an enclosed area, a plurality of spaced members of heat conducting material disposed within said area, the remaining portion of said space being substantially filled with a shield substance which at high temperatures is capable of flowing out of said area, discharge means in communication with said area and the exterior of said container for discharging said shield substance from said area outward-1y of the container to create heat insulation spaces within said area.

7. A shipping container including safety shield means and comprising a body means having a cavity formed therein for receiving radioactive material, movable closure means for closing said cavity, said body means including an outer portion defining safety shield means extending peripherally about said body means and spaced outwardly of said cavity, said safety shield means including an enclosed area having a plurality of spaced members of good heat conducting material disposed therewithin and extending peripherally about said body means, said members of good heat conducting material having holes formed therein to provide communication between the various areas defined therebetween, a shield substance being disposed between said members of good heat conducting material and at high temperatures being in a liquid state and capable of flowing through the holes in said members of good heat conducting material, and discharge means in communication with the area of said safety shield means and the exterior of said container for discharging said shield substance outwardly of the container to create heat insulation spaces within said area.

8. Apparatus as defined in claim 7 wherein said members of heat conducting material are formed of metal and are provided with a shiny surface.

9. Apparatus as defined in claim 7 wherein said shield substance comprises a eutectic metal alloy.

10. Apparatus as defined in claim 9 wherein said alloy includes as principal ingredients, lithium and lead.

11. A shipping container including safety shield means and comprising body means having a centrally located cavity therewithin for receiving radioactive material, movable closure means for closing said cavity, said body means including a side wall portion defining a peripherally extending enclosed area about the body means and spaced outwardly of said cavity, said enclosed area being included between a pair of spaced peripherally extending side walls, a plurality of layers of material of good heat conducting material disposed within said area and extending peripherally around said body means, said layers being spaced from one another and having holes formed therein to provide communication between the spaces defined between the layers and between the adjacent side walls, the free area between said spaced side walls being substantially filled with a shield substance which at high temperatures is in a liquid state and which is capable of flowing out of the space between said side walls, discharge means in one of said side walls in communication with said area and the exterior of said container for discharging said shield substance outwardly of the container to create heat insulation spaces within said area, and means normally preventing discharge of shield material from said area.

12. Apparatus as defined in claim 11 wherein said shield substance comprises a metal alloy having as a major ingredient thereof lead.

13. A shipping container including safety shield means and comprising body means defining a centrally located cavity formed therewithin and being defined by an inner wall of the body means, movable closure means for closing said cavity, said body means including an intermediate wall spaced from said inner wall and an outer wall spaced outwardly of said intermediate wall, radiation shielding material disposed between said inner wall and said intermediate wall, safety shield means disposed between said intermediate wall and said outer wall and extending peripherally about said body means, said safety shield means including a plurality of layers of material of good heat conducting characteristics which extend peripherally about the body means within the area defined between said intermediate and outer walls, said layers being spaced from one another and having holes formed at spaced points therein, the remaining free area benormal-1y preventing discharge of shield substance fromsaid area.

14. A shipping container including safety shield means and comprising a body means having a cavity formed therein for receiving material to be shipped, movable.

closure means for closing said cavity, said body means including a safety shield means at the outer portion there-.

of spaced outward of said cavity and extending therearound, said safety shield means including an enclosedarea, said enclosed area being substantially filled with a liquid substance, said safety shield means including discharge means in communication with said area and the exterior of said container for discharging said liquid substance from said area outwardly of the container to create a heat insulation space within said area, and relief means normally preventing discharge of said substance through said discharge means.

15. Apparatus as defined in claim 14 wherein said relief means comprises a relief valve adapted to open at a predetermined pressure.

16. Apparatus as defined in claim 14 wherein said relief means comprises fusible plug means adapted to melt at a predetermined temperature.

17. A shipping container including safety shield means and comprising body means having a centrally located cavity for receiving radioactive material, movable closure means for closingsaid cavity, said body means including an inner wall, an intermediate wall and an outer wall each of which is disposed in spaced relationship to the adjacent wall, the area between said inner wall and said intermediate wall being substantially filled with the radiation shielding material, the area between said intermediate wall and said outer wall comprising safety shield means and including an enclosed area, a liquid substance disposed within said enclosed area, discharge means formed in said outer wall and being in communication with said enclosed area and the exterior of; said container for discharging said liquid substance from said enclosed area outwardly of the container to create a heat insulating space within said enclosed area, and relief means normally preventing discharge of said substance from said enclosed area.

18. Apparatus as defined in claim 17 wherein said relief means comprises relief valve means adapted to open at a predetermined pressure.

19. Apparatus as defined in claim 17 wherein said relief means comprises fusible plug means adapted to melt at a predetermined temperature.

20. Apparatus as defined in claim 17 including check.

valve means operatively connected with said outer wall for filling said enclosed area with said liquid substance.

References Cited UNITED STATES PATENTS 2,872,651 2/1959 Treanor 17415 3,005,105 10/1961 Lusk 250-106 X 3,046,403 7/1962 Montgomery 250-106 3,113,215 12/1963 Allen 250108 3,133,197 5/1964 Allen 250-106 3,215,194 11/1965 Sununu et al. 17415 X ARCHIE R. BORCHELT, Primary Examiner.

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