US2772361A

US2772361A - Radioactive source holder

Info

Publication number: US2772361A
Application number: US399446A
Authority: US
Inventors: Everett N Hiestand
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-12-21
Filing date: 1953-12-21
Publication date: 1956-11-27
Anticipated expiration: 1973-11-27

Description

27, 1956 E. N. HIESTAND 2,772,361

RADIOACTIVE SOURCE HOLDER Filed Dec. 21, 1953 5 Sheets-Sheet l INVENTO'R.

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Nov. 27, 1956 E. N. HIESTAND 3 RADIOACTIVE SOURCE HOLDER Filed Dec. 21, 1953 5 Sheets-Sheet 2 INVENTOR. [Vere/f /V. H/lesrcmd ATTORNEYS.

Nov. 27, 1956 E. N. HIESTAND RADIOACTIVE SOURCE HOLDER 5 Sheets-Sheet. 5

Filed Dec. 21, 1953 mmvmx. Evereff /V. Hieslana BY 1A4) a) M W ATTORNEYS Nov. 27, 1956 E. N. HIESTAND RADIOACTIVE SOURCE HOLDER 5 Sheets-Sheet 4 Filed Dec. 21, 1953- II I III ji i=- INVENTUR.

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1956 E. N. HIESTAND RADIOACTIVE SOURCE HOLDER 5 sneeis-sheet 5 Filed Dec. 21, 1953 INVENTOR. Eve/"eff A Hfesfana" ATTORNEYS.

United States Patent() lice RADIOACTIVE SOURCE HOLDER Everett N. Hiestand, Columbus, Ohio, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application December 21, 1953, Serial No. 399,446

Claims. (Cl. 250-106) This invention relates to shielded containers for radioactive sources, and, more particularly, to a remote-operation container for gamma radiation sources.

Modern industrial radiography utilizes the short penetrating rays of gamma radiation from sources such as cobalt- 60, iridium.192, and other gamma-emitting isotopes, which are enumerated in the Isotopes Catalog, January 1953, Oak Ridge National Laboratory. An inherent property of such penetrating rays is that they will pass through a wood or metal object and indicate such passage by acting upon the emulsion of a photographic film. The radiographs so produced are interpreted by examination of the variation in the densities of the penetrating rays, as indicated by their action on the emulsion of a photographic film, and thus permit a determination to be made of the internal structure of the object being radiographically examined.

Various types of containers have been used for gamma sources, which permit the emission of rays through openings in the container. Such containers usually consistof a lead-lined box provided with a circular aperture fitted with a screwed cap or plug through which the passage of rays may be regulated and directed (collimated) toward objects placed in their path. Another type of container has been designed in the shape of a sphere with a hingedly mounted wedge-shaped cover which is adapted to fit a corresponding opening in the spherical shield.

Still another type of container, which is suitable only,

for low-energy sources, has a tear-drop shape, with a handle operable to open the spherical end of the container, thus permitting the emission of rays.

All of the above-described types of containers require that the operating personnel be in the vicinity of the container when the object being examined is first exposed to radiation. The box-shaped container requires that the aperture can be removed by some manual means. The spherical-shaped container requires that the cover be raised. The tear-drop-shaped container requires that the handle be operated to open the end of the container. In each instance, operating personnel are exposed, at the very least, to stray radiation. t

Another disadvantage of prior-art devices is that the aperture through which the rays are emitted cannot be collimated or varied in shape or size without the danger of exposing personnel to direct. radiation, or else without disassembling and removing the gamma source entirely from the apparatus before the aperture size is changed.

Still another disadvantage of the prior art is that the shielded containers, as described above, do not permit the source-to-object distance to be varied so as to permit variation in radiographic techniques to be made without exposing the operating personnel to at least stray radiation.

A further disadvantage of the above-described types of apparatus is that they will not readily permit radiographic examination under water, or in any medium other than air.

I 7 Therefore, it is' an object of this invention to provide H 2,772,361 Patented Nov. 27, 1956 Z a shielded container for radioactive sources that will provide adequate shielding for personnel in the area and will permit remotely controlled exposure to the radiation.

Another object of this invention is to provide a shielded container that will permit the radioactive source to be moved from the center to the front of the container by remote operation so as to permit variation in radiographic techniques.

Still another object of this invention. is to provide a shielded container for radioactive sources that will permit controlled aperture sizes, ranging from a pencil beam to a hemispherical volume.

Still another object of this invention is to provide a shielded container for radioactive sources which may be remotely operated for radiographic examination in water, air, or any other medium.

Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof taken in connection with the attached drawings, in which like numerals refer to like parts, in the several views, and in which:

Fig. 1 is a front plan view of a container embodying the invention shown in the open position;

Fig. 2 is a rear plan view of a container embodying the invention shown in the open position;

Fig. 3 is a sectional elevational view on line 3-3 of Fig. 1;

Fig. 4 is a sectional view on line 4-4 of Fig. 3;

Fig. 5 is a sectional view on line 5-5 of Fig. 3;

Fig. 6 is a fragmentary elevational view showing the generally spherical shape of the shield; and

Fig. 7 is a fragmentary elevational view showing the shape of the shutter assembly. The shutter assembly has two convex surfaces and one concave surface, and is hereinafter described as having a biconvexo-concave shape. it i A gamma source suitable for radiography requires that the source be shielded for the protection of the personnel in its vicinity. Thus, for any container, shielding is a primary factor in design. The high density of lead makes it a satisfactory shielding material and enables the container to be made smaller than other materials would permit. For example, in absorbing the radiations of iridium-192, iron is only one-third as effective as lead; hence, an iron sourceholder would be three times as large as one constructed primarily of lead. However, dense and radiation-absorbent materials other than lead may be used as shielding material.

"The thickness of the shielding material is. dependent on the energy of radiation from the source. Two inches of lead are adequate to protect the operating personnel from a 10 curie, iridium-192 source, while 7 inches of lead are required for a higher energy source, such as cobalt-60. Stated generally, the higher the energy of the radiation from this source, the larger the amount of shielding required, and, therefore, the container must be larger and heavier. For example, a lead sphere 5 /2 inches in diameter weighs 36 pounds; however, a lead cube 5 inches on one side would weight 68 pounds. Because of the high density of lead, the relatively small volume of difference between a sphere and a cube makes a significant difference in the total weight of the sourceholder, thus making a spherically shaped container the most desirable.

A preferred embodiment of the invention, as shown by the drawings, includes as basic components: a generally spherically shaped. shield assembly; a biconvexoconcave shaped shutter assembly; a generally cylindrically shaped source-carrier assembly; a shield-assembly actuating mechanism including actuating means; and, a source-carrier actuating. mechanism. including actuating means, all hereinafter described in detail. All compo.- nents are fabricated from stainless steel or other suitable materials, unless otherwise indicated.

The shield assembly comprises the generally spherically shaped metal shell which is filled with lead 11, or another radiation-shielding material, through fitting 12 and which has a cylindrical hole along one-axis thereof (see Fig. 6), two shell-mounting

side plates

13 and 14, and an end brace 17. A flat spiral spring 18 may be attached from the drive shaft 71 to side plate 13, by spring bracket 19 affixed to side plate 13, so as to aid the movement of the shield assembly to the open position in line with the aperture 21 in the shutter assembly.

The shutter assembly comprises the biconvexo-concave-shaped shell 20, one section of this shell having a cylindrical aperture 21 therein, which is filled with lead 11 through fitting 34 and two

shutter side plates

22 and 23. To

side plates

22 and 23 are affixed'a top plate 24 and a base plate 25, thus forming the basic structural frame of the container.

Aflixed to top plate 24 and base plate 25 are two

frame'side plates

26 and 27. Affixed to

side plates

26 and 27 are two bearing

housings

28 and 29 containing two ball-

type bearings

30 and 31, said bearings being held in position in housings 28 and'29 by

closures

15 and 16. The

bearings

30 and 31 are sealed by 0

rings

32 and 33, so that sea water, dirt, etc., will not interfere with the function of the bearings. The shield assembly rotates through an arc segment on the bearings so as to move the source from the closed position behind the completely lead-filled section of the shutter assembly to the open position in line with the aperture 21. After the desired exposure time has elapsed, the shield assembly is returned to the closed position. The source-carrier assembly is of generally cylindrical shape and comprises two parts: the carrier body and the carrier cap. The carrier body has a tubular outer shell and a coaxially located inner shell 41. The annular space between the two shells is filled with'lead 11. The two shells are faced at one end with a thin, metal cap 42 which functions as a window for emission of gamma radiation. The two shells are joined at the other end by a tapped plug 43 which is grooved to receive an O ring 54 which forms a seal between plug 43 and plug 46 to keep sea water, dirt, etc.-, out-of the source-carrier assembly. The carrier body -is strengthened by a spacer 44, which maintains the relative, position of outer shell 40 and inner shell 41. The outer shell 40 is flanged outwardly at the cap end so that the movement of the source-carrier assembly within the shield assembly is restricted when the source-carrier assembly is retracted.

The carrier cap has a tubular shell 45 which is filled with lead 11. At one end of shell 45 is a threaded plug 46 which has fastened thereto a plunger 47, which has a diameter slightly less than the diameter of the inner shell 41 in the carrier body. The plunger 47 is filled with lead 11. In the end of the plunger 47 is a spring retaining plug 48 which servesto provide a seat forthe -mechanism is fastened. In this embodiment of the invention, the interlocking "means is an open C shaped book. The size of the slot in the interlocking means need be limited only by the radius in which the inter-' locking lever 70 will move. A collar 53 is 'adju'stably fitted to the shell 45 so as to limit "the movement'of the source-carrier assembly within the shield assembly as it is extended through the aperture 21 toward the front of the shutter assembly.

The shield-assembly actuating mechanism comprises a control anchor 60 which is pivotably fastened to side plate 14 and control rod 61 affixed to said control anchor. The location of the control anchor in relation to the axis of the

bearings

30 and 31 is such that a force exerted by the control rod, which is connected to the control anchor, aided by fiat, spiral spring 18, if used, will rotate the shield assembly through an arc segment to the open position in line with aperture 21. When the force exerted by control rod 61 is reversed in direction, the shield assembly will return to a closed position behind the completely lead-filled section of the shutter assembly. A lock or catch arrangement (not shown) may be used to secure the shield assembly in the open or closed position. An actuating means, other than through a mechanical linkage, such as hydraulic cylinders or electrical solenoids, can be used to effect movement of the shield assembly.

The source-carrier actuating mechanism comprises an interlocking lever 70 which is contained in its forward or extending movement by interlocking means 52, a drive shaft 71, to which the interlocking lever 70 is rigidly atiixed and which is mounted through

frame side plates

26 and 27 and held in position at one end by collar 72, a drive-shaft crank 73 which is rigidly affixed to the other end of drive shaft 71 and which is separated from side plate 27 by a spacer 74, a connecting rod 75 hingedly fastened to the drive-shaft crank 73, and a con trol rod 76 rigidly affixed to the connecting rod 75. The action of the actuating mechanism is such that when the shield assembly is in the open position in line with aperture 21, a force exerted by control rod 76 will cause the interlocking {lever 70 to engage the interlocking means 52, and the source-carrier assembly will be extended through the aperture 21 toward the front of the shutter assembly. When the force exerted by control rod 76 is reversed in direction, the source-carrier assembly will retract from within aperture 21 and the shield assembly may be rotated to the closed position. An actuating means, other than through a mechanical linkage, such as hydraulic cylinders or electrical solenoids, can file used to effect movement of the source-carrier assem- In the embodiment of the invention which is shown in the drawings, the interlocking lever 70 tends to be in a position such that it cannot readily engage with interlocking means 52 when it is desired to actuate the sourcecarrier assembly. Therefore, means (not shown) for spring loading the interlocking lever 70 against a fixedposition stop 'so as to maintain the interlocking lever in a position such that it will readily engage the interlocking means 52 and be constrained thereby may advantageously be used. Spring loading of the interlocking lever 70 may also function to maintain the extended position of the source-carrier assembly when the shield assembly is in open position.

A latch (not shown) may be pivotally mounted on

bearingclosures

15 and 16 and will function to lock the source-carrier assembly in a retracted position while the shield assembly is being rotated to a closed position. .The latch couldbe spring loaded in such a manner that the latch is always tending to engage with a notch atop interlocking means 52.

Various control brackets andmountings (notshown) may be aflixed to frame

side plates

26 or 27, or other components 'of'the container, as are required by the particular shield assembly and source-carrier actuating means used.

If apertures smaller than aperture 21 in theshutterassembly are desired, a lead plug containing the desired aperture may be inserted into the shutter assembly. The lead plug interferes with the passage of the carrier out through the shutter, but results in no inconvenience, because the only way of collimating a beam of radiation is by placing shielding in front of the source to absorb the radiation in all but the region of the desired beam. Hence, it is impossible to have a collimated beam and also have the source up against the object. It is advantageous that the design of this sourceholder permits the insertion of the desired aperture before the sourceholder is moved to the open position. Other units have to be opened before the aperture can be inserted, and in so doing the personnel are exposed to radiation from the source.

The source capsule 50 may be loaded into the sourcecarrier assembly at a safe distance, preferably while the entire container is under several feet of water. The carrier body with cap removed is left in the shield assembly and the container is then lowered in the water. The source capsule is then lifted by a pick-up tool and dropped through the open end of plug 43 into the carrier body. The carrier cap is then lowered and put in place with capsule spring 49 contacting the source capsule 50. There is now sufiicient shielding so that the entire container can be removed from the water and the final assembly operation performed at close range. The container is placed in a vacuum oven and thoroughly dried to remove all traces of moisture. Final assembly is made by tightening the threaded plug 46 into the tapped plug 43, a seal being made by O ring 54. The end brace 17 is fastened to

side plates

13 and 14 and the container is ready for use.

The embodiment of the invention described and shown above may be operated in fresh water or seawater, in air, or in any other medium. When the container is at the desired location, the shield-assembly actuating mechanism is actuated so as to rotate the shield assembly from the closed position to the open position. The sourcecarrier actuating mechanism may then be actuated so as to extend the source-carrier assembly the desired distance into and through aperture 21. This may all be done by remote operating actuating means and the personnel are shielded to a maximum degree from harmful rediation.

The thickness of the lead shielding material 11 and the size of the entire container may optionally be changed to furnish adequate shielding for sources of greater or lesser activity as desired, and may be so dimensioned as to reduce the intensity of radiations from any particular source at the outer surface, below the maximum levels permitted for transportation by common carrier.

One unique feature of this new sourceholder is that the holder can be located with the aperture against the object to be radiographed and fastened rigidly in place without interfering with the opening and closing of the holder. This is possible because neither a hinged cover nor a plug must be removed from the front of the source to expose it. The new holder is opened by swinging the source and its shield from behind the shielded portion of the shutter to a new position behind the aperture and then pushing the source and carrier out through the aperture if the application requires that the source be against the object. Separate remote controls may be provided for performing these two simple operations. In addition to this, a positive locking mechanism may be provided to assure that the holder is aligned in either a completely open or a completely closed position. A third remote control is provided to release this lock so that the holder may be opened or closed. The lock is both a safety feature and a convenience to the operating personnel.

The remote-operation container, according to the invention, may be used for underwater radiography. It may also be used for the examination of large castings and heavy forgings where, in order to obtain satisfactory radiographs, a source of such high intensity must be used that only a remote-operation container could comply with safety requirements.

While a particular embodiment of the present inven tion has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the appended claims are intended to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is: l

1. A radioactive source container comprising a capsule for holding a radioactive source; a radiation-absorbing shield, one surface of which is equidistant at every point from a predetermined axis; a mounting for said capsule within said shield and pivotable about said axis; and a radiation-absorbing member having an aperture therethrough so located that radiation can be emitted through the aperture when said capsule is registering with the aperture and the radiation is absorbed when the capsule mounting has been pivoted away from the vicinity of said aperture, said capsule being axially slidable in said mounting for movement into said aperture.

2. A radioactive source container comprising a capsule for holding a radioactive source; a generally spherically shaped radiation-absorbing shield, one surface of which is equidistant at every point from a predetermined axis; a generally cylindrically shaped carrier for said capsule within said shield and pivotable about said axis; a radiation-absorbing shutter having an aperture therethrough so located that radiation can be emitted through the aperture when said capsule is registering with the aperture and the radiation is absorbed when the capsule carrier has been pivoted away from the vicinity of said aperture, and lever means engaging said capsule carrier for moving the capsule carrier into said aperture.

3. A radioactive source container comprising a radioactive source capsule mounted in a source carrier near the center of a generally spherically shaped shield filled with a radiation-shielding material and having removed therefrom a section conforming to the concave surface of a shutter; said shutter consisting of two sections, either of which serves to complete the generally spherical shape of the shield, one section having an aperture therethrough, the balance being filled with a radiation-shielding material, the other section being completely filled with a radiation-shielding material, lever means engaging the source carrier for moving the carrier and the capsule into said aperture.

4. A radioactive source container according to claim 3 in which the source carrier is generally cylindrical in shape and comprises a carrier body and a carrier cap: the carrier body having a tubular outer shell and a coaxially located inner shell, the annular space between the two shells being filled with a radiation-shielding material, the two shells being faced at one end with a metal cap and joined at the other end with tapped plug; the carrier cap having a tubular shell which is filled with a radiationshielding material, said shell having at one end a threaded plug to which is fastened a plunger at the end of which is a spring-retaining plug and a capsule spring, said shell having at the other end an end plug to which an interlocking means is affixed.

5. A radioactive source container according to claim 3 in which the generally spherically shaped shield comprises a metal shell which has a cylindrical hole along one axis thereof, two shell-mounting side plates affixed to said shell, two shield-bearing closures afilxed to said side plates and an end brace affixed between said side plates.

6. A radioactive source container according to claim 3 in which the shutter comprises a biconvexo-concave shaped metal shell, one section of the shell having a cylindrical aperture therethrough, two shutter side plates afiixed to said shutter and a top plate and a bottom plate aifixed to said side plates so as to form the basic structural unit of the container.

7. A radioactive source container according to claim 6 in which two frame side plates are aifixed to the top plate and bottom plate and two bearing housings'are afiixed to said frame side plates.

8. A remote-operation radioactive source container comprising a spherically shaped shield, a shutter, and a source carrier for a radioactive source capsule; said spherically shaped shield having a section removed so as to conform to the concave surface of the shutter, having a cylindrical hole along one axis thereof, and having rigidly afiixed thereto an actuating means for moving said shield in an arc segment with relation to the shutter; said shutter having one concave surface and two convex surfaces, either of which convex surfaces serves to complete the spherical shape of the shield, one convex surface having an aperture therethrough to the concave surface; said source carrier being generally cylindrical in shape and having an actuating means engaging therewith for moving said radioactive source capsule while within said source the shutter, and the source carrier, are all at least partially filled with a radiation-shielding material.

10. A remote-operation radioactive source container according to claim 8*in which the actuating means may be selected from mechanical, electrical solenoid and hydraulic mechanisms.

References Cited in the file of this patent UNITED STATES PATENTS Piggott et al. Aug. 2, 1949 Pennock et al Feb. 23, 1954