US2976423A - Manipulating radioactive material - Google Patents

Description

March 21, 1961 R. J. PREST MANIPULATING RADIOACTIVE MATERIAL 2 Sheets-Sheet 1 Filed May 15, 1956 rap...- III-"II...

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MANIPULATING RADIOACTIVE MATERIAL MANIPULATING RADIOACTIVE MATERIAL Robert J. Prest, Concord, Mass., assignor to Technical Operations, Incorporated, Arlington, Mass., a corporation of Delaware Filed May 15, 1956, Ser. No. 585,081

22 filaims. (Cl. 250-106) This invention relates to a system of manipulating radioactive material, such as sources of gamma radiation consisting of an incapsulated cobalt isotope.

Radioactive material which is used for various industrial purposes, such as for radiographic testing by means of panoramic or directional radiographic exposure devices, has to be exchanged upon exhaustion, for example by means of source changers of the type providing for storing and shipping of a fresh source as well as for receiving an exhausted source. Such exchange involves the detaching and attaching of containers and propelling means for the radioactive material with full attention to the safety of the personnel that carries out these operations, it being understood that sources which are referred to as exhausted are nevertheless capable of inflicting considerable damage if not properly shielded.

Systems according to the invention thus involve devices for utilizing radioactive material, such as the above mentioned radiographic machines, devices for storing and transporting radioactive material, coupling devices for safely attaching and detaching the carrying and propelling components to each other, and apparatus for conveniently manipulating such devices while the radioactive material is amply protected.

.Objects of the present invention are to provide a system of the above type which permits the optimally safe and yet convenient and quick exchange of radioactive material between a storage and transportation device and an exposure device and vice-versa, to provide for positive operation of such a system which does not necessitate possibly unreliable remote control of attaching and detaching operations and which permits direct observation of such operations, to provide such a system which permits directly positive connection and disconnection of radioactive source carrying and propelling apparatus while the sources involved are fully shielded, to provide such a system which inherently promotes a prescribed safe sequence. for Withdrawing, exchanging and storing radioactive material, and generally to provide improved systems of the above type which are safe, certain and reliable as to construction and mode of operation and which are nevertheless comparatively inexpensive since they can be fabricated from mostly quite inexpensive material and commercially readily available components.

Briefly stated by Way of a summary indicating its nature and substance, the invention introduces, in one of its principal aspects, apparatus for manipulating radioactive material that is carried by propelling means for transporting it between shielding devices, which apparatus comprises a guide tube that is connected to a first shielding device and has an open end, bushing means having at one end means for fastening thereto guide means that lead to a second shielding device, and have at the other end bridging guard means which can be axially withdrawn, and expedients for distancing the open end of the guide tube from the bushing means and for aligning the guide tube and the bushing means. The guard Patented Mar. 21, 1961 ice means bridge the gap between the bushing means and the open end of the guide tube and preferably comprise a tube which slides within the bushing means and spring means tending to keep the tube outside the bushing in the aforementioned gap. 7 p

in another important aspect, the invention involves apparatus for transporting and changing radioactive material by means of elongate carrying and propelling means which apparatus comprises a shielding container having two adjacent openings, Within its container a continuously curved conduit such as a metal tube leading with its ends towards respective openings, and within the conduit approximately at the center of the shielding container, means such as a pin inserted transversely of the tube, for stopping the passage of a source of radioactive material from one end to the other end of the conduit. The conduit openings of such apparatus are preferably provided with two gap bridging components, one for each of the two adjacent openings of the shielding container, which duplication provides for and promotes the safe exchange of sources.

In a further important aspect, the invention includes I the spring means accessible, in combination with a plug member fitting the axial recess of the receptable member and having a peripheral groove for engagement with the spring means, and in further combination with a spring lifting releasing means which fits the peripheral groove of the receptacle member and has a projection for lifting the spring means from the transverse recess of the receptacle member, for thus disengaging the receptacle and plug members. This connector, while having other uses, is especially practical in combination with the above characterized system for propelling radioactive material between shielding devices, the entire system then comprising, in addition to the connector, two tubular guide means within or leading to respective shielding devices, support means for the guide means and for establishing a distancing gap therebetween, and elongate source carrying and propelling means such as cables in the tubular guide means, such that ends of a source carrying meanscan. be placed in the gap.

These and other objects and aspects of the invention will appear from the following description of a typical embodiment thereof illustrating its novel'characteristics. i

This description refers to a drawing in which Fig. l is a schematic elevation, partly in vertical section, of a system according to the invention, including exchanging and exposure devices;

Fig. 2 is a top elevation of the bridge top of the source changer shown in Fig. 1;

Figs. 3, 4, 5 and 6 are axial sections of the top of the; source changer, in four difierent conditions indicating its operation;

Fig.v 7 is an elevation, partly in axial section, of a connector according to the invention;

Fig. 8 is a section on lines 8-8 of Fig. 7;

Fig. 9 is the view of a tool for operating the connector according to Figs. 7 and 8; and

Fig. 10 is a section similar to Fig. 8 but with the tool according to Fig. 9 applied thereto.

In Fig. 1 numeral 15 indicates the above mentioned source changer, 45 indicates a panoramic exposure apparatus, and indicates a snout for receiving a radio- 3 that 15 and 45 are merely examples and that the invention can be applied to moving sources between two changers or other shielding apparatus.

The source changer 15 which is of a novel type especially useful for purposes of the present invention, has a steel housing 16 with a lid or top 17 welded thereto. The housing contains a U-shaped or otherwise tortuously shaped tube 21 for example of stainless steel which, with its open ends 21.1, 21.2, penetrates the cover 17 to which it is welded at these points. The housing is filled with shielding material 18, such as lead. Approximately in the center of the shield, the tube 21 has a transversely inserted pin'22 or similar stop device which defines the safe position of sources that are stored in or transported by means of this shield. The stop 22 divides the tube 21 into two halves 21.5 and 21.6. The shield is thus capable of confining (not necessarily simultaneously) two sources 25, 26 attached to respective carrying and propelling means such as cables 27, 28 herein referred to as source cables, each of which has at its other end a cable connector device. Normally, when the changer is used for storing or transporting, only one source and one half of the connector is present, as indicated at 211 of Fig. 1, 211 being the male half of a connector according to Fig. 7. Mounted on the cover plate 17 is a changer mount 31 which consists in this embodiment of a bridge plate 31.1 and two webs 31.2 and 31.3. The plate 31.1 carries, in the manner to be described below, changer heads 100 facing respective ends 21.1, 21.2 of the tube 21. These heads 100 will be described in detail with reference to Figs. 3 to 6 and are individually indicated at 100.1 and 100.2 of Fig. 1.

A detachable housing for the bridge with its exchanging heads is indicated at 39 of Fig. 1, and a device for locking the closed housing to the changer top is indicated at 39.1

The exposure apparatus 45 comprises in essence a housing 46 with a top plate 47 that has openings for the two ends 56.1, 56.2 of a tortuously shaped guiding and confining conduit 56 for example a stainless steel tube. The housing 46 is filled with shielding material 48 such as lead. To the tube end 56.1 is attached as a source guide means a flexible conduit 50 which confines a source propelling cable 51, herein also referred to as exposure cable. For normal operation, the cable 51 carries, by way of a connector 200, a source cable 28, within a flexible conduit 60 attached to the end 56.2 of the tube 56. A source 26 can be held, by means of the cable 28, at the safe position in the center of the shield 48. Also by means of cable 28, the source can be propelled into a snout device 90. The latter has a conventional screw coupling 91 for connecting it to the end of the tube 60, and may comprise a control switch housing 92. Fig. 1 shows the cables 28 and 51 and the connector 200 in dot and dash lines to indicate'the exposure condition when the source 26 is in the snout, in order to distinguish from their position within the tube 60 when the latter is attached to the source changer, at head 100.2, for purposes of changing sources. At the end 56.1 of the tube 56 of exposure apparatus 45 can be arranged a safety control and signalling unit 59 which responds to the position of the connector 200 or to some other correspondingly arranged locating means.

As will become apparent, Fig. 1 shows in full lines the condition hereinbelow identified as V and shown in Fig. 4, when the source 26 is within the shield 15 and the flexible conduit 60 is not yet unscrewed from the exchanger head.

The exchanger heads, marked 100.1 and 100.2 in Fig. 1, constitute means for separately directing carrying means of radioactive material, such as sources 25 and 26, and are preferably of identical design that will now be described with reference to Figs. 3 to 6.

Each head has an adapter tube or bushing 132 which is screwed into the bridge sheet 31.1 of mount 31 which 4 distances it from the top plate 17, and has a locking flange 132.5, an outside thread 132.6, a flared outer opening 132.7 and an inner opening with a rim 132.8.

A tube 114 which is slightly flared out at the upper end 114.1 and has at the other end a shoulder 114.2, is inserted in the opening 132.8 of the bushing 132 such that a spring 114.5 tends to expel it from the inside of the bushing and to press it into the recess 21.5 of the shield tube 21, thus fully closing the gap between the ends of tube 21 and bushing 132.

Each exchanger head has a cap 135 that can be screwed to the bushing thread 132.6 as shown in Fig. 3. The cap has fastened thereto a holddown rod 135.6 that has at its outer end a recess 135.7. With the cap on, and a source wtih its source cable 27 in the changer (for example in tube half 21.5 as shown in Fig. 1), the recess 135.7 receives the plug portion 223 of the connector half 211 thus securing the radioactive source.

Similar to Fig. 1, Figs. 3 to 6 also indicate the source cables with the male connector component 211, and Figs. 4 to 6 show in addition and instead of the cap 135, the coupler 91 for the snout which coupler sits on a coupler flange 60.1 that is fastened to the flexible conduit 60. The coupler 91 has a thread 60.2 and an inwardly extending rim 60.3. By means of this conventional arrangement, the outer end of a conduit such as the snout tube 60 can be firmly attached to each one of the heads, as indicated in Figs. 4 to 6.

Figs. 5 and 6 show in addition an exposure cable 51. The end of this cable 51 carries the other half 212 of the connector 200, whose half 211 was mentioned above as fixed to the source cable 28. In Fig. 5 the two halves are shown in fully connected position, whereas Fig. 6 indicates the uncoupling operation by means of the key T which is also shown in Figs. 7, 9 and 10.

The connector proper, such as indicated at 200 of Fig. 1, will now be described with reference to Figs. 7 to 10.

This connector consists of a plug member 211 and a receptacle member 212. Figs. 7, 8 and 9 show the connector as attached to cables 28 and 51, but it will be understood that the connector can also be used for di rectly attaching thereto a snout capsule, such as indicated at 25 and 26 of Fig. 1.

As shown in Figs. 7 and 8, the stud portion 211 of the connector has a cylindrical plug 223 with an annular recess 223.1 and a rounded conical head 223.2.

The receptacle portion 212 has a cylindrical recess 231 which fits the plug 223, and in its intermediate portion 233 the receptacle member has machined thereinto a generally speaking rectangular recess or box 235.1 which recess extends into the countersunk bore 235.2.

A The spring 241 is generally speaking U-shaped with a transverse intermediate portion 242 which is parallel to an annular recess 235, and to a transverse slot 236 which corresponds to the annular groove 223.1 of the plug member 211, when the latter reaches into the cylindrical recess 231 of the receptacle member 212. The substantially parallel end portions 243.1 and 243.2 (Figs. 8 and 10) of the spring 241 reach into the slot 236 which is deep enough to permit the spring portion 242 to rest in the annular recess 223.1 of the plug member, when the two connector members are attached to each other. Longitudinal recesses 243.5, 243.6 receive the arms of the spring 241 which is fastened to the receptacle member 212 by means of an insert 248 which, after staking is turned to the body diameter.

It will now be evident that the spring 241 in the locking position which is indicated with full lines in Fig. 7, firmly connects the receptacle member 212 to the plug member 211. If the spring 242 is lifted by means of a tool T it can be easily brought into the position which is indicated in dot and dash lines in Fig. 7, and also in Fig. 10. i

It will be understood that the semi-circular inner face cable omitted from that figure.

of the tool T, marked 1 in Fig; 9, accommodates the circular groove 235 of the recess portion 212, and that the two arms t1 and t2 are long enough to lift the spring 241 into the position wherein it releases the stud 223 as shown in Fig. 10.

For purposes of exchanging the exhausted radioactive source of apparatus of the type described above with reference to the shield 45 of Fig. 1, against a fresh source contained within a unit of the type of the shield 15, the above described arrangement operates as follows, it being understood that it can be used analogously with otherinstallations of the same general character.

Shortly recapitulating, the exposure unit 45 comprises a flexible tube 60 having at its end a snout unit 90 which is detachable therefrom by means of a coupler 91. Within this flexible tube moves an exposure cable 51 to the end of which is attached to a source cable 28 by means of a connector similar to that described with reference to Figs. 7 to 10. The source cable is in turn attached to the source proper by way of a connector that is not specifically described herein because its construction is immaterial, but which can be of the type of the connector according to Figs. 7 to 10.

Assuming that the exposure device 45 contains a source which is for practical purposes exhausted (herein referred to as old source) and that the source changer contains in one of its tube halves a fresh or only partially exhausted source (herein referred to as new source), a complete cycle of the operations that are necessary for exchanging the old source with the new source is as follows.

It is assumed that the source changer 15 contains a new source in a capsule, indicated at 25, within the half 21.5 of the tube 21, which ends at 21.1 and head 100.1. The other tube half 21.6 which ends at 21.2 is empty, contrary to the showing of Fig. 1 which indicates a later stage as pointed out above. It is further assumed that the exposure apparatus 45 has its old source withdrawn therewithin, again contrary to Fig. 1 for the above reason. It will be remembered that the source cable 27 of the new source 25 and hence the source itself are so:

cured by the holddown rod 135.6 with its recess 135.7 engaging the end of plug 223 (Fig. 3).

In the following explanation, Figs. 3 to 6 are used for describing the operation of both heads, 100.1 and 100.2 in order to reduce the number of figures, which is possible since the heads are and must be identical. The order of the consecutive steps is indicated in these figures, and identified in the following text, with the aid of Roman numerals. Numeral I as applied to Fig. 3 indicates the normal condition of the head 100.1 with the new source 25 secured by cap 135 and holddown rod 135.6. The empty half of the changer, with head 100.2 is not separately illustrated; it looks exactly as Fig. 3 but without source cable 27.

After unlocking and removing the cover 39, the cap 135 with rod 135.6 of head 100.2 is removed and the coupler 91 of the snout end of tube 60 is screwed onto the bushing 132 after the snout 90 has been detached. This step II is illustrated in Fig. 4 but with the source The tube half 21.6 is empty and the source inside of shield 45. The cap 135 of the other head 100.1 is of course left undisturbed for the time being.

The operator now retires to a safe distance and moves the old source 26 into the tube 60 and through its open end through the head 100.2, until the source is at the safe point 22 of the tube 21. The head 100.2 is now in condition III which is exactly shown in Fig. 5. After having made certain that the old source is safely located in the changer 15, the spring loaded guide tube 114 is lifted (Fig. 6), thus exposing both connector components 211 and 212, the one on the source cable 28 and the other on the exposure cable 51. The connector spring 232 is now lifted with the key T, as explained with reference to Figs. 7 to 10. This is the position IV as indicated in Fig. 6. The two halves of the connector are,

ed bushing 132 and the cap is securely replaced therei on, rod 135.6 engaging the coupling half 211. This stage is indicated at VI, Fig. 3.

The old source 26 is now secured safely within the tube half 21.6 and held by head 100.2, whereas the new source 25 is still within 21.5 and held by head 100.1. As mentioned above with reference to position V and indicated in Fig. 1, the connector half 212 at the end of the exposure cable 51 is near the end of its tube 60 from which the snout is still removed so that only the coupler 91 is attached thereto.

In order to transfer the new source 25 from the changer 15 to the exposure apparatus 45, the cap 135 of the head 100.1 is removed, and the snout tube coupler 91 is screwed onto the bushing 132. This is stage VII, indicated by Fig. 4. The exposure cable is now inserted into the bushing 132, aided by its funnel shaped end 132.7 and the flared end 114.1 of the tube 114, at which stage the situation is approximately that as shown in Fig. 5, but with the connector halves not yet engaged. The tube 114 is now again lifted and the two connector ends securely engaged, for which purpose the use of the tool T is not necessary. This stage VIII is indicated in Fig. 6. After having made very certain that the connection is complete, and after the guide tube 114 has been released to engage the shoulder 21.5 which is position IX, illustrated in Fig. 5, the operator retires to a safe distance and moves the new source from the changer 15 into the exposure unit 45, leaving the tube half 21.6 below head 100.2 completely empty.

The snout tube 60 is now disengaged from the bushing 132, the snout piece 99 is attached by screwing it to the coupler 91, the cover 39 of the changer 15 is replaced and padlocked, whereupon the exposure device is ready for operation with the new source and the old source can be shipped for exchange with a new source.

It should be understood that the present disclosure is.

for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. Apparatus for manipulating radioactive material,

that is carried by propelling means for transporting it between shielding devices, comprising: a guide tubethat is connected to a first shielding device and has an open end; bushing means having at one end means for fastening thereto guide means leading to a second shielding device; means for distancing said bushing means from said open end of said guide tube and for aligning the guide tube and the bushing means, to form a gap between said open end of the guide tube and the other end of the bushing means; and at the other end of said bushing means, guard means bridging said gap which can be axially withdrawn to open the gap.

2. Apparatus according to claim 1 wherein said distancing means comprises a cover plate mounted on said first,

expel-ling the guard tube from the bushing to bridge said gap.

4. Apparatus according to claim 3 wherein said bushing means has a rim at said other end, wherein said guard tube has a flange close to its free end, and wherein said 7 spring means includes a helical spring extending between said rim and said flange.

'5. Apparatus according to claim 3 wherein said guide tube has at said open end a recess fitting said free end of said guard tube, whereby said spring means normally places said free end of the guard tube into said recess of said guide tube.

6. Apparatus according to claim 1 further comprising: shielding means containing said guide tube; means for closing the other end of said guide tube; and flexible pro pelling means in said guide tube for attachment thereto at the closed end of the guide tube of radioactive material, and reaching with the other end into said open end of the guide tube.

7. Apparatus according to claim 6 further including cap means for closing said first end of said bushing means when guide means are not fastened thereto, said cap means including a holddown rod which extends into said bushing and has at its free end a recess capable of engaging and holding in place said other end of said flexible propelling means.

8. Apparatus for transporting and changing radioactive material by means of elongate carrying and propelling means, comprising: a shielding container having two adjacent openings; within said container a continuously curved conduit means leading with its ends towards respective ones of said openings; within said conduit means,

- approximately at the center of said shielding container and in the approximate center of said conduit means, means for stopping the passage of a source of radioactive material from one end to the other end of the conduit means; and, associated with each one of said openings, means for separately directing thereinto carrying means for radioactive material; whereby each half of said conduit means serves as a separate shielding container for radioactive material placed near said passage stopping means, said means at each opening including a removable conduit element immediately outside the associated opening providing access to carrying and propelling means therein.

9. Apparatus according to claim 8 wherein said conduit means includes a tube and said stopping means includes a pin inserted traversely of the tube.

10. Apparatus according to claim 8 further comprising head means mounted adjacent at least one of said openings for supporting said directing means, said directing means including bushing means with its inner end distanced from said opening to form a gap between said bushing and said conduit means, having at the outer end means for fastening thereto guide means for a radioactive source, and having at said inner end guard means for bridging said gap and capable of being withdrawn into the bushing means.

11. Apparatus according to claim 10 further comprising, in one of said halves of said conduit means, flexible propelling means for attachment thereto adjacent said passage stopping means of radioactive material, and reaching with the other end into said gap.

12. Apparatus according to claim 8 further comprising head means mounted on said container, distanced from and facing both openings and supporting said directing means, said directing means including two bushing members each being coaxial with, and distanced from said conduit means at the respective one of said openings, each bushing member including guard means slidingly fastened thereto for withdrawably bridging the gap between the respective opening and its bushing member.

13. Apparatus for manipulating radioactive material for transporting it between shielding devices, comprising: two tubular guide means each leading to a shielding device; means for supporting one end of each of said guide means and for distancing them in axial direction, forming a gap therebetween; an elongate source carrying and propelling means in each of said tubular guide means, such that an end of each carrying means can be placed in said gap;

connector means for joining said carrying means and for detaching them in said gap, including on the end of one of said carrying means a receptacle member having an axial recess, a transverse recess on one side of said axial recess, transverse spring means radially movable in said transverse recess, and a peripheral groove giving access to said spring means, and on the end of the other carrying member a plug member fitting said axial recess of said receptacle member and having a peripheral groove for engagement with said spring means; and spring lifting means fitting said peripheral groove of said receptacle member and having a projection for lifting the spring member from said transverse recess of said receptacle member and for thus disengaging the receptacle and plug members when said ends of the carrying means are placed in said gap.

14. Connector means for joining elongate carrying means for radioactive material, comprising: a receptacle member having an axial recess, a transverse recess on one side of said axial recess, transverse spring means radially movable in said transverse recess, and a peripheral groove giving access to said spring means; a plug member fitting said axial recess of said receptacle member and having a peripheral groove for engagement with said spring means; and spring lifting means fitting said peripheral groove of said receptacle member and having a projection for lifting the spring member from said transverse recess of said receptacle member and for thus disengaging the receptacle and plug members.

15. Connector means for joining elongate carrying means for radioactive material, comprising: a receptacle member having an axial recess, a transverse recess on one side of said axial recess, transverse spring means radially movable in said transverse recess, a plug member fitting said axial recess of said receptacle member and having a peripheral groove for engagement with said spring means, and a peripheral groove on a side of said receptacle member giving access to said spring means for lifting said spring means out of said transverse recess and disengaging the receptacle and plug members.

16. Connector means for joining elongate carrying means for radioactive material, comprising: a receptacle member having an axial recess in one end thereof, a transverse recess on one side of said axial recess, a transverse spring means radially movable in said transverse recess, a plug member fitting said axial recess of said receptacle member and having a peripheral groove for engagement with said spring means, and two parallel grooves one on each side of said receptacle member directed transversely to said axial recess and to said transverse recess giving access to said spring means for lifting said spring means out of said transverse recess and disengaging the receptacle and plug members.

17. Apparatus for manipulating radioactive material that is carried by propelling means for transporting it between shielding devices, comprising: a guide tube that is connected to a first shielding device and has an open end; coupling means having means for fastening thereto guide means leading to a second shielding device; means for spacing said coupling means from said open end of said guide tube and for aligning the guide tube and the coupling means, to form a gap between said open end of the guide tube and said coupling means; and removable guard means bridging said gap forming substantially a continuation of said guide tube from said open end thereof to said coupling means.

18. Apparatus for manipulating radioactive material that is carried by propelling means for transporting it be tween shielding devices, comprising: a guide tube that is connected to a first shielding device and has an open end; coupling means having means for fastening thereto guide means leading to a second shielding device; means for spacing said coupling means from said open end of said means, to form a gap between said open end of the guide tube and said coupling means; guard means adapted to bridge said gap forming substantially a continuation of said guide tube from said open end thereof to said coupling means, said guard means being movably attached to said apparatus relative to said coupling means and said open end of said guide tube to permit said gap to be opened, and means releasably to hold said guard means in position bridging said gap.

19. Apparatus according to claim 17 further comprising: shielding means containing said guide tube; means for closing the other end of said guide tube; and flexible propelling means in said guide tube for attachment thereto at the closed end of the guide tube of radioactive material, and reaching with the other end into said open end of the guide tube.

20. Apparatus according to claim 19 further including cap means for closing said coupling means when guide means are not fastened thereto, said cap means including a holddown rod which extends into said coupling means and has at its free end a recess capable of engaging and holding in place said other end of said flexible propelling means.

21. Apparatus for manipulating radioactive material for transporting it between shielding devices, comprising: two tubular guide means each leading to a shielding device; means for supporting one end of each of said guide means and for distancing them in axial direction, forming a gap 'therebetween; an elongate source carrying and propelling means in each of said tubular guide means, such that an end of each carrying means can be placed in said gap; connector means for joining said carrying means and for detaching them in said gap, including on the end of one of said carrying means a receptacle member having an axial recess, a transverse recess on one side of said axial recess, transverse spring means radially movable in said transverse recess, and an external groove giving access to said spring means, and on the end of the other carrying a means a plug member fitting said axial recess of said receptacle member and having a peripheral groove for f engagement with said spring means, said external groove giving access to said spring means for lifting said spring means out of said transverse recess and disengaging the receptacle and plug members when said ends of the carrying means are placed in said gap.

22. Apparatus for transporting and changing radioactive material by means of elongate carrying and propelling means, comprising: a shielding container having two openings, a continuous curved conduit connecting said openings and having its mid-point substantially, in the a center of shielding material in said container, a barrier across said conduit approximately at said mid-point,

means at each of said openings for separately and independently directing into and removing from said conduit a carrying means for radioactive material, said means at each opening including conduit coupling means spaced from and aligned with said opening, and removable guard means bridging the gap between each of said coupling means and the associated opening, said guard means forming substantially a continuation of said conduit to each of said conduit coupling means.

References Cited in the file of this patent UNITED STATES PATENTS France May 19,

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