US2642541A - Shielding container for radioactive sources - Google Patents

Description

lJune 16, 1953 v J, F; 'YOUNG 2,642,541

l SHIELDING CONTAINER FoR RAD1QACT1VE SOURCES Filed Nov. 29, 1951 2 sheets-sheet 1 Inventar,

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June 16, 1953 J. F. YOUNG SHIELDING coNTAINER Foa RAnIoAcTIvE souRcEs 2 sheets-sheet 2 Filed Nov. 29, 1951 l 2.7 Inventor, rfozn if lazgy,

Patented June 16, 1953 UNITED SHIELDING GONTAINER FOR RADIOACTIVE SOURCES John F. Young, Salem, Mass., assigner to Tracerlab, Inc., Boston, Mass., a corporation of Massachusetts Application November 29, 1951, Serial No. 258,818

(Cl. Z50-108) 11 Claims. l

This invention relates to containers for radioactive sources such as those used in industrial radiography. More particularly it is concerned with a new and improved container for safely storing and transporting sources of high radiation intensity, such as Cobalt-60 and having a unique provision for shielding the radiographer even when the container is open for removing or replacing the source.

Non-destructive testing of materials has become increasingly common with the availability of high intensity gamma emitters, e. g., Cobalt-60 as a substitute for the very expensive radium compounds heretofore in use. This type of radiography utilizes the -absorption properties of dense materials to form latent shadow images on i'llm sensitive to the penetrating gamma rays emitted by the isotope. Thick specimen sections interposed between the source and lm produce light areas on the developed film, whereas progressively darker areas are produced Whenever the total thicknesses are less. In solid castings, then less dense volumes such as gas holes would appear as dark spots on the developed film.

The use of these high intensity sources presents the problem of protection to the radiographer from excessive radiation dosage. Remote handling equipment has been devised to remove the source from its shielding container and place it into position for radiographic test. The present art does not, however, have a shielding container which effectively protects the radiographer while he is opening the container to allow for removal of the source.

The primary object of the present invention is to provide a new and improved shielding oontainer for radioactive sources to minimize radiation exposure from the source to the operator in either opening or closing the container and removing or replacing the source.

Another object of the invention is the provision of a compact, sturdy, upright and readily accessible container for radioactive sources, adequately shielded to meet all safety requirements.

With the foregoing in mind, the invention is featured by the provision of a container of the type described including a generally spherical shield composed of lead or other suitable material relatively impermeable to gamma rays, and having a cavity near its center for holding a capsule containing the radioactive source and a slotted opening from its periphery to the cavity giving access to the capsule, a shielding cover composed of the same material fitting the slotted opening and hinged to permit swinging from a closed position completely shielding the source to an open position where it still serves to shield the operator from direct radiations from the source. The shielding cover is so proportioned and arranged that in closed position it will place between the source and the outside wall of the cover a thickness of shielding material comparable to the thickness of the other walls of the shielding sphere. In addition means are provided facilitating the raising of the cover without exposure of the operator to direct radiations from the source and a stop for holding the cover in its predetermined open position above described. Furthermore, a convenient locking arrangement is provided for locking the cover secure in closed position to prevent tampering by unauthorized personnel.

Still other objects, features and advantages of the invention will become apparent from the following detailed description of a preferred embodiment thereof taken in connection with the annexed drawings, in which like numerals refer to like parts in the several views, and in which:

Fig. 1 is a plan View of a container embodying the invention with the cover in closed position, the open position of the latter being indicated by dash and dot lines;

Fig. 2 is a front elevation of the same;

Fig. 3 is a side elevation of the same;

Fig. 4 is an enlarged sectional view on line 4-4 of Fig. 1;

Fig. 5 is a fragmentary elevational view showing only the lead shielding sphere and illustrating its central source holding cavity; and

Fig. 6 is an elevational view with portions cut away of the wedge-shaped cover which is adapted to t the corresponding opening in the spherical shield.

The shielding container of the invention comprises a generally spherical shielding member, which may be a lead casting having a minimum lead wall thickness of 37/8 inches for sources up to 500 millicuries. Generally at the center of the sphere I0 is located a cylindrical cavity I2 for receiving a lead insert I3 in Which the source holder I4 is removably held. The usual source I6 consists of the radioactive material sealed in its holder, a ferromagnetic stainless steel capsule I4. The capsule serves the function of preventing dispersion of the radioactive Cobaltand provides for absorption of the weak beta radiation therefrom to give a pure gamma source.

The container proper I0 is provided wi-th a wedge-shaped slotted opening I9 having a horizontal floor Il ush with the upper rim of the 3 opening I2 which holds the insert I3. The opening I9 is arranged to receive the cover I8 in a manner hereinafter more fully described.

The cover I8 which is a wedge or pie shaped segment of the shielding sphere I rotates on the hinge pin 20 which is supported by the hinge plates 22a and 22h forming a part of the outer steel framework. Opening of the cover allows positioning of the source within the shielding sphere I8. As the radiographer opens the container the cover I8 serves as a shield so that he is not exposed to the direct radiation'even while handling the source. A properly trained loperator can keep the shield and cover between'his person and the source during most, if not all, of the duration of the radiography procedure until the same is again safely enclosed in the con'- tainer. This unique safety feature is of Aextreme practical importance in View of the limited tolerance of the human body to penetrative radiations such as gamma rays.

The cover stop rod 24 fun-ctions to maintain the cover I8 in a satisfactory shielding position while in its open position. The cover lift 26 enables the radiographer readily to open the unit by lifting the rather heavy cover I8. The cover consists of an outer framework 2'I of steel about a cored cavity which is filled with lead as indicated by the numeral 28.

Serving as an outer protective framework for the shielding sphere is the cylindrical steel base 30, the bottom steel plateA 32 which is welded to the base, the two hinge plates 22a and 22o and the lifting lug plates 34a and .34h which are provided with handling holes 35. The hinge plates have holes 36 located above the cover lift 26 so that once the source is within the; shielding container means are available to lock the unit With a padlock or other securing means. All the abutting elements of the steel frameworks are welded together to form a rugged unitary structure.

It will be noted that the lead container I8 while generally spherical in contour is nevertheless somewhat elongated in its vertical dimension. Furthermore, the horizontal floor II of the wedge-shaped cover-receiving opening I9 is somewhat above the horizontal center line of the sphere. This construction permits the locating of the cavity I2, lead adapter I3- and capsule I4 in such a way that the source I3 will be close to the geometrical center of the unit, with a maximum thickness of lead on all sides when the cover is closed.

While I have herein disclosed and described a source-holding capsule having a particular configuration, the upper end (as seen in Fig. 4) thereof being enlarged to facilitate handling, it will be understood that the container ofthe invention may be adapted for holding sources of other dimensions by providing lead inserts I3 having sockets of a variety of sizes and shapes. In each case the adapter I3 preferably is provided with a socket precisely tting the source capsule and additionally provides shielding so that a minimum weigh-t of outer shielding is required.

In the use of the container, the radiographer may transport the same to the desired location by means of the handling holes 35. lWhen the subjects to be radiographed have been prepared for exposure the lid I8 is opened by means of a remote handling tool using the ledge 26. The cover will remain suspended in open position by reason of engagement With the bar 24, as in- 4 dicated by the dash and dot lines in Figs. 1 3. The radiographer, operating from a position behind the open cover, and using a remote handling tool such as a magnetic holder, may remove the capsule I4 from its seat in the insert I3 and place it in proper position to expose the 'articles to be radiographed. During the opening of the container and the removal and replacement of the source, the operator is shielded to a maximum degree from harmful radiations by containers spherical walls and the open cover in any of its positions from fully closed to fully opened.

The container, according to the invention, is adapted for transporting radioactive source of high intensity from one place to another with no danger to persons in the vicinity. The thickness of the lead walls may optionally be changed to furnish adequate shielding for sources of greater or lesser activity as desired. Furthermore, the locking arrangement is such as to prevent .opening by unauthorized personnel during transport or storage. The shielding Acontainer may be appropriately dimensioned to reduce the intensity of radiations from the particular source at its outer surface below the maximum levels permitted for transporta-tion by common carrier. l

The unique shielded container of the invention is not limited to usage in the radiography art, but may be used anywhere that radioactive sources are to be transported or stored ready for convenient use with a minimum of danger to personnel.

While I have herein shown and described a container according to the invention employing lead as a shielding medium, it will be understood that other relatively radiation impermeable materials may be used without departing from the invention. Furthermore, while I have herein disclosed and described a preferred embodiment of the invention it Will be understood that the same is susceptible of various modifications and changes Within the spirit and scope of the appended claims.

I claim:

1. A shielding container for the storage and transportation of radioactive sources which comprises, in combination, a generally spherical member composed of radiation shielding material, said member having a cavity located generally at its center for removably holding a radioactive source and having a Wedge-shaped slotted opening from its periphery to said cavity permitting access to the latter, a cover also composed of radiation shielding material fitting said slotted opening, and a hinged mounting for said cover permitting swinging thereof about a horizontal axis from a position lling said opening and shielding said ysource through a predetermined angle to a second position permitting access to said source while affording a maximum of shieldingprotection to the operator during removal from and replacement in said cavity of said source.

2. A shielding container for the storage and transportation of radioactive sources which comprises, in combination, a generally spherical me. ber composed of radiation shielding material, a cylindrical metallic holder in which said member is mounted, said holder having portions extending over` the upper portions of said member, said member having a cavity located generally at its center for removably holding a radioactive source and having a wedge-shaped slotted opening in its upper portion extending from its periphery to said cavity permitting access to the latter, a cover, also composed of radiation shielding material conforming in shape to said slotted opening and hingedly mounted on an upwardly extending portion of said metallic holder permitting swinging thereof about a horizontal axis from a position filling said opening and shielding said source through a predetermined angle to a second position permitting access to said source while affording a maximum of shielding protection to the operator during removal from and replacement in said cavity of said source.

3. Apparatus in accordance with claim 2 including a stop bar mounted on an upwardly extending portion of said metallic holder for supporting said cover open in a predetermined position.

4. Apparatus in accordance with claim 2 in which said cover is provided with an overhanging ledge to facilitate opening thereof.

5. Apparatus in accordance with claim 2 in which the upwardly extending portions of said metallic holder include a pair of flanges adjacent said slotted opening, said flanges having means permitting the locking of said cover in closed position.

6. Apparatus in accordance with claim 2 in which said wedge-shaped opening has verticalrear and side walls and a horizontal Hoor, said cavity opening into a rear portion of the latter, said floor being above the center of said member, whereby said source, when positioned in -said cavity, will be located close to the geometrical center of said member.

7. A shielding container for the storage and transportation of radioactive sources comprising, in combination, a generally spherical member formed of radiation shielding material, said member having a wedge-shaped opening extending from its periphery with vertical rear and side walls anda horizontal floor, a cover also formed of radiation shielding material conforming in shape to said opening, and means hingedly mounting said cover along the upper edge of said rear wall of said opening permitting swinging of said cover from a position lling said opening through an angle of approximately 180 degrees, said member having a cavity located generally at its center and communicating with the horizontal floor of said opening for removably `holding a radioactive source.

8. A shielding container for the storage and transportation of radioactive sources comprising, a generally spherical member formed of radiation shielding material, said member having a cavity formed substantially at its geometric center for removably containing a radioactive source and a wedge-shaped opening, extending from its periphery with Vertical rear and side walls and a horizontal floor, said cavity communicating with the floor of said opening near the intersection of said floor and said rear Wall, said side walls being parallel to each other and spaced equidistantly on either side of a vertical axis through the center of said member, said rear wall being perpendicular to said side walls and displaced from said vertical axis whereby the floor of said opening is somewhat longer than said rear wall, a cylindrical metallic holder in which said member is mounted, said holder having portions extending upwardly beyond said member, a cover conforming in shape to said opening also formed of radiation shielding material hingedly mounted along the upper edge of said rear wall on an upwardly extending portion of said holder permitting swinging thereof from a position lling said opening through an angle of approximately 180 degrees to an open position, said cover when in the open position permitting access to said source while affording a maximum of shielding protection to the operator during removal from and replacement in said cavity of said source,

9. Apparatus in accordance with claim 8 including a horizontal stop bar mounted on an upwardly extending portion of said metallic holder for supporting said cover in the open position.

l0. Apparatus in accordance with claim 9 in which the upwardly extending portions of said metallic holder further include a pair of flanges adjacent to the side walls of said opening, said flanges including means permitting the locking of said cover in the closed position.

1l. A shielding container for the storage and transportation of radioactive sources comprising, a generally spherical block of radiation shielding material, said block having a wedgeshaped opening formed therein extending from its periphery with vertical rear and side walls and a horizontal floor, said side walls being parallel to each other and spaced equidistantly on either side of a vertical axis through the center of said block, said block also having a cylindrical cavity formed therein coaxial with said vertical axis and communicating with the floor of said wedge-shaped opening, a protective framework for said block including a cylindrical metallic base having a pair of hinge plates extending upwardly therefrom beyond the upper portion of said block, said hinge plates being arranged adjacent to the side walls of said opening, a cover conforming in shape to said opening also formed of radiation shielding material hingedly mounted along thel upper edge of the rear wall thereof between said hinge plates permitting swinging thereof from a closed position filling said opening to an open position, a stop bar JOHN F. YOUNG.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Gilks l May 1, 1951 Number

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