US2891168A

US2891168A - Portable source of radioactivity

Info

Publication number: US2891168A
Application number: US565280A
Authority: US
Inventors: Raymond C Goertz; Kenneth R Ferguson; Rylander Elmer William; Lenard M Safranski
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-02-13
Filing date: 1956-02-13
Publication date: 1959-06-16
Anticipated expiration: 1976-06-16

Description

3 Sheets-Sheet 2 R. C. GOERTZ ET AL PORTABLE SOURCE OF RADIOACTIVITY &

June 16, 1959 Filed Feb. 13, 1956 June 1959 R. c. GOERTZ ET AL v PORTABLE SOURCE OF RADIOACTIVITY 3n 5 f ll M s H m .a W sl .F 7 s /5 m .c a I EM; m 5 w 0% Filed Feb. 13, 1956 Patented June 16,- 1959 United States Patent 'fiiicei .i oiirsiinu sooner: or RADIOACTIVITY fiaymonfl 3C. Goertz, :Downefs Grove,Kenneth. R.;Ferguison, lLisle, ElmerWilliam Rylander, Leniont, and Len- )flidxM- ESafiranski, Downers Grove, 111.,assignors to the ;I.Inited ,States of America, represented .by the United aStatesAtomicEnergy Commission Application February 13, 1956, Seria'INo. sssaso 4 Clainis. r01. zso. 1ti.6

The 'inventionrelates to a source of radioactivity. More specifically, it relates to a radioactive source that is compact, portable, safe, and easily renewed.

It has long been recognized as desirable that 'a source of radioactivity 'be portable. "Such 'a portable rsource qbulflibe used extensively at advanced bases or in the field by ,army surgeons 'for emergency X-ray photography and fiuoroscopy. When :the portable sourcee'mits gamma rays, the source maybe put to good'usein indust-rial plantsgfor testing purposes.

However, di'fiiculty has been encountered in making a portable source of radioactivity and yet light {enough 1.0 .be portable. There is also the problemof conveniently removing and replacing the active core of the portable source when the core has lostits strength.

The present novel design has satisfactorily solved these problems. According to the present invention, the active core is mounted in a tungsten rotor that is in turn mounted in a brass housing containing a lead insert. The rotor moves 180 between a position in which the core is exposed and a position in which the core is shielded. This arrangement enables the core to be easily replaced.

In the drawings:

Fig. 1 is an elevational view of the apparatus of the present invention;

Fig. 2 is a horizontal sectional view taken on the line 2--2 of Fig. 1;

Fig. 3 is a vertical sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary sectional view illustrating the details of theradioactive capsule and the parts with which it directly cooperates;

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

Fig. 6 is a sectional view taken on the line 66 of Fig. 3 .and

Fig. 7 is asectional view taken on the line 7--7 of Fig. 6.

As shown in Fig. 4, a capsule 10 comprises an active Gore -1;l,xan aluminum-foil enclosure 12, innerand outer aluminum cups 13 and 14, and inner and

outer aluminum plugs

15 and 16. The core is formed of a radioactive material that emits radiation of the desired energy. Thulium-170, which emits 52 kev. X-rays, and americiurn-242, which emits 40 kev. gamma rays,'are suitable sources for radiographic purposes, whereas cobaltis-a suitable source of 1.17 and 1.33 mev. gamma rays for radiographic purposes and also for therapeutic purposes. The thulium can be a mixture of thulium-l69 and thulium-l70, which may be formed by the irradiation of thuliurn-l69 in a neutronic reactor. The material of thecore may be in the form of a metal disk, a compound of the metal, or an enclosure containing powder of the metal or a compound of the metal. The inner plug 15 is welded to the inner cup 13 and the outer plug 16 is welded to the outer. cup 14.. Two sets of plugs and cups are used so that there are 'two 2 wlds andiihus ti'oubl'e insurance 'a'lgainst leakage of at ye material from the capsul e 10; flhei recesses =iri th plugs 15 and IG faEiIitat iliewldin'g thereof to the cups- 13 and 14 and-serve purpose in the finished capsule; 1 V v capsule '1-0 is assumed in a ho'le1'7 --whieh extends diametrically eornpleftely through'a rotor 18 formed of a machineable tungsten *allo'y, which 'may consistdf *W, 6% Ni, and-4 Cu in parts *by weight, The capsule 10 rests against a stainless steel disk 19 which in turn rests against ashouldei 219 formed in the opening 17 adjacent one end thereof. The disk 19 is very thin, having a tliick-ness of .002 in., for example. The capsule 10 is held against the disk-19 by a spring 21 having the form -of -a cupped disk of 'Phosphhrbronze. The spring 21 is -l'le lii against the "capsule 10 by a tungsten-alloy plug '22 offthesame composition as the rotor 18. The plug -22 closely fits the hole 17 and has "an enlarged threaded end 23 having threaded engagement with a threaded section of the hole 1'7 and also "a con ical shoulder 24'engaging a conical shoulder in the ro tor hole 18. A snaprin-g of stainless steel fitting in a groove in the rotor hole 17 retains the plug 22 in the rotor 18. "The plug 22 is put in'pl'ace and removed from the rotor 18 by "a screw "driver engaging "a slot, not shown, formed in'the large end of the plug 22.

The rotor 18 is carried at its lower end by a stub shaft 26' of brass which is silver-soldered to the rotor andhas a locating projection 27 projecting into the rotor. The stub shaft 2:6'is journaled by "means of a stainless-steel ball bearing 28 in a brass plug 29. The rotor-1'8 is carried at its upper "end by a driving shaft 30 of -stainless steel "which is silver-soldered to the rotor and has a locating projection 31 extending into the rotor and a driving projection 32 also extending into the rotor and .functioning to drive the rotor in the event of failure of the soldered connection between the rotor and the driving shaft. The driving shaft .30 extends through an aluminum plug 33 to the exterior thereof and is journaled in the plug by means of a stainless steel ball bearing34.

The rotor 18 and ithe'plugs 29 and33 are positioned in an inner tubular. portion 35 of a body 36 of cast brass, which also has an outerfportion 37 which extends froman end of'the tubular portion 35 Where the plug 33 is vpositioned" radially outwardly from the tubular'po'rtion 35 and along the same in spaced relation thereto. The free end of the inner portion 35 lies beyond' that of the outer portion 37 so that a brass annulus 38, which cooperates with the body '36 in enclosing a lead doughnut 38wcast into place in the space formed between the inner and

outer portions

35 and 37 of the body 36, embraces the free end of the innerportion '35 and abuts the free end of the outer portion 37. The annulus '38 is brazed to the outer portion .37 of the body 36 as indicated at 39 and to the inner portion 35 as indicated at 40. Thea'nnulus 38 has a recess 41 which receives a flange 42 on the plug 29, which is brazed to the annulus 38 as indicated at 43. Theplug 33 has a flange 44 through which screws 45 go which have threaded engagement with the body'36 and thus secure the plug 33 tothe body 36. The body 36,

plugs

29 and 33, and annulus 38 constitute a housing that enclosesthe rotor 18.

The body 36 is provided with a conical opening 46 which goes through the inner and

outer portions

35 and 37 and is formed by a-conical portion'47 which connects the

portions

35 and 37. The opening 46 is covered by a dust shield in the form of a Lucite disk 48, which is held against the body 36 .by a snap ring 49. A closure cap 50-of :brass can be threadedinto the body 36-over the disk 48. The rotor 18 moves between the shielded position of Fig. 3, in which the capsule 10 is at the end of the hole 17 away from the opening 46 and the plug 22 blocks radiations or emanations from going out through the opening 46, and an exposed position, not shown, in which the capsule 10 lies at the opening 46. In moving between these positions the rotor 18 is permitted only 180 of movement by means that will be described presently. Thus, as shown in Fig. 2, the lead doughnut 38a can be, and is, made thinner on one side beneath a fiat section 51 of the outer portion 37 of the body 36, with resultant saving in weight of the lead doughnut, because capsule 10 does' not go past this thinner side of the lead doughnut in moving between exposed and shielded positions, but isforced to go past the opposite side.

As shown in Fig. 3, the driving shaft 30 is rotated by a cable 52 housed in a tubular sheath 53 and carrying a plug 54 having a driving connection with a socket 55 formed on the end of the driving shaft 30. The rotor 18 is urged to the shielded position of Fig. 3 by a spiral spring 56 which, as shown in Figs. 3 and has one end inserted through the shaft 30 and the other end wrapped about a post 57 set in the body. 36. An arm 58 is secured by means of a hub 59 to which it is welded or soldered, to the driving shaft 30. The hub 59 is se cured to the shaft 30 by a taper pin 60 and a nut 61 threaded on the end of the taper pin against a washer 62 pressed against a flat surface 63 of the hub 59. The taper pin 60 fits in a tapered hole in the hub 59 and in a recess in the driving shaft 30. The arm 58 is engageable with a post 64 set in ,the body 36 when the capsule is in shielded position, and with a post 65 set in the body 36 when the capsule 10 is in exposed posltion.

The rotor 18 is held with the capsule 10 in shielded position when, as shown in Fig. 6, the arm 58 is engaged by a latch 66 which passes under the arm 58 and hooks over the depending outer end thereof. As shown in Figs. 6 and 7, the latch 66 is secured to an extension 67 of a rotatable barrel of a lock 68. The lock is operated by akey 69 which can be removed therefrom only when a slot 70 of the lock is in the position shown in Fig. 5, i.el, when the latch 66 engages the arm 58 and thus holds the rotor 18'with the capsule 10 in the shielded position of Fig 4. The .latch 66 can be rotated out of the position of Fig. 6, in which it holds the arm 58 against movement only because clearance is provided for the latch 66 in the form of a recess 71 formed in the hub 59. After the latch 66 has released the arm 58, the latch 66 can return to the position of Fig. 6 only after the arm 58 has been returned to the position of Fig. 6 because in any other position of the arm 58 the recess 71 in the hub 59 will have moved from the posi-' tion of Fig.6, and thus the latch 66 will not clear the hub 59 in attempting to return to the position of Fig. 6. If the latch 66 is not in the position of Fig. 6, the key 69 cannot be withdrawn from the lock 68 as previously described, and so the impossibility of withdrawing the key 69'from the lock 68 provides a warning that the capsule 10 is not in the shielded position of Fig. 4. Another warning is provided by the inability to apply a cover 72 when the key 69 is in the lock 68, because the key piioigects into the space the cover would occupy when app e The cover 72, which is of brass, has threaded engagement with one end of a brass fitting 73' which has its, other end 'in threaded engagement with the body 36 and held there by aset screw 74. .The lock 68 is mounted on the fitting 73 so that its outer portion is held against rotation. The fitting 73' has a short threaded tubular section 75 within which the plug 54 and the socket 55 on, the driving shaft 30 engage oneanothen. A collar 76" threadedon the tubular section 75 engages a flange 77 on the tubular sheath and thus keeps the plug 54 in the socket 55. The fitting 73 has an arcuate slot 78 which accommodates a projection 79 through which an arrow member 80 is secured to the arm 58 and indicates the position of the capsule 10. The words Open and Closed appear on the fitting 73 adjacent the ends of the slot 78 and the location of the arrow member 80 at one or the other of these words indicates that the capsule 10 is in shielded position or in exposed position.

The apparatus of the present invention can be carried by a handle 81 which is connected to the body 36 by

straps

82 and 83 at opposite sides thereof the strap 82 being pivoted on a relatively long projection 84 formed on the flat section 51 of the body 36, and the strap- 83 being pivoted on a relatively short projection 85 formed on the side of the body 36 opposite the flat section 51. The plug 29 has a threaded opening 86 by which the apparatus may be detachably secured to a suitable mounting structure such as a tripod.

The apparatus of the present invention constitutes a portable source of gamma rays. When the capsule 10 is adjacent the opening 46 in the body 36, emanations come out over an angle of 40, the size of the open ing 46. The emanations may be used in X-ray pho; tography and fiuoroscopy for medical purposes and for! industrial testing. The beta particles are taken out by the aluminum cups 13 and 14. Very little reduction in the gamma rays is provided by the thin stainless-steel disk 19, the real purpose of which is to prevent escape ofthe active core 11 in the event of accident where enough heat might be generated to melt the aluminum cups 13 and 14 and plugs 15, and 16. j

The present apparatus hasmany features that cause it to fail safe. The spring 56 tends to return thecap sule 10th the shielded position of Fig. 4. The'key 69 by which the'arm 58 is released from the latch 66 to per mit the capsule 10 to be moved to exposed position can not *be removed unless the capsule 10 is held in shielded position by engagement of the arm 58 by the latch 66.: The cover 72 cannot be applied to the fitting 73 if the key 69 is in the lock 68. The threaded connections of the 'cap' and the fitting 73 with the body 36 and the cover 72 with the fitting 73 provide a very difficult path for radioactivematerial to escape in the event of release of the radioactive material from the capsule 10.

When the capsule 10 is to be replaced it is very easily removed from the rotor 18 upon removal of the plug'22 through the opening 46 in the body 36. When the enlarged end 23 of the plug 22 is being unscrewed from the rotor 18 by a screwdriver inserted through the opening 46, the plug 22 itself adequately shields the operator'of the screwdriver. After the head on the plug 22 is 'completely unscrewed, remote-control apparatus may be used to manipulate the present apparatusto permit the plug 22 and the capsule 10 to fall out. This sample removal of the capsule 10 is made possible, because the opening 17in which the capsule 10 lies extends diametrically through the rotor, and the rotor 18 moves 180 in taking the capsule 10 from its exposed position to its shielded 1 position.

The intention is to limit the invention only withinthe scope of the appended claims. 5 What is claimed is: 1

l. A portable source of radioactivity comprising a lead body having substantially the form of a surface generated by a semi-circle rotated about an axis lying in its plane and-parallel to but spaced from the flat side of the semicircle thereby providing a cylindrical hole extending through the middle of the body, a brass housing surround ing said body providing a cylindrical cavity therein concentric with said cylindrical hole, a cylindrical tungsten rotor rotatably mounted'on its axis in the cavity and co-' axially therewith, the housing and lead body being provided witha frusto-conical opening extending therethrough with the smaller section opening into said'cylindrical cav ity and having its axis lying along a line which substan said cylindrical cavity, the rotor having a cylindrical hole extending diametrically therethrough and coaxial with said frusto-conical opening and having a diameter approximately equal to that of the smaller end of said opening, a shoulder adjacent one end of said hole in the rotor, a capsule containing thuliurn positioned in the hole in the rotor against said shoulder, a tungsten alloy plug substantially filling the remainder of the hole in the rotor and retaining the capsule against said shoulder, means for rotating the rotor between an exposed position Where the capsule lies adjacent the inner end of said frusto-conical opening and a shielded position 180 away in which the outer end of the tungsten alloy plug is adjacent the inner end of said frusto-conical opening and prevents radiations from the capsule from emanating through said frustoconical opening, the shape of the lead body providing substantially uniform shielding for the capsule in all positions and controlling the beam of radiations, when the capsule is in the exposed position, by limiting it to the shape of that of the opening.

2. A portable source of radioactivity comprising a cylindrical tungsten rotor having a diametrical hole extending through the approximate middle thereof, a shoulder adjacent one end of said hole, a capsule containing thuliurn in said hole, a removable tungsten alloy plug substantially filling the remainder of said hole and retaining the capsule against said shoulder, a lead doughnut-shaped body surrounding said cylindrical rotor and having a cylindrical center hole in which the rotor is coaxially mounted for rotation, a relatively thin housing surrounding the aforesaid elements, said housing and lead body having a frusto-conical opening extending therethrough coaxially located with respect to the hole in the rotor and having its smaller end opening into said center hole, means for mounting the rotor in the housing for rotation about its axis, means to rotate the rotor between an exposed position in which the capsule lies adjacent the smaller end of the opening in the housing and a shielded position 180 away in which the tungsten-alloy plug shields the capsule against emitting radiations through said opening, the structural relationship of the lead body with respect to the rotor providing substantially uniform safe shielding about the capsule in all positions into which and through which the capsule is movable except for the radiation beam in the exposed position in which position that part of the lead body surrounding the frusto-conical opening functions to produce a conical beam of radiation emanating from the capsule having an apex angle equal to that of said opening.

3. An apparatus of the character described comprising a brass cylinder having a flat face along the outside surface parallel to the axis of the cylinder and a central bore coaxial with the axis of the cylinder, the Walls of the cylinder having a substantially semi-toroidal recess therein with its axis coaxial with the axis of the cylinder, said recess being semi-cylindrical in cross-section with the curved portion on the radially outermost surface and having a flat face on its outside surface parallel and adjacent to the flat face on said cylinder, the cylinder being provided with a frusto-conical opening extending therethrough having its axis parallel to said flat faces and lying along the diameter of the recess perpendicular to the axis thereof, the smaller end of said opening being at the inside of said wall, a brass plug in one end of said bore and an aluminum plug in the other end of the bore leaving a cylindrical recess in the middle of the brass cylinder, a cylindrical tungsten rotor substantially filling said cylindrical recess rotatably mounted in said plugs on its axis which is coaxial with the axis of the brass cylinder, the rotor having a diametrical hole therethrough coaxial with the axis of said frusto-conical opening and being provided with a shoulder adjacent one end, a capsule containing thulium positioned in the hole abutting the shoulder, a tungsten-alloy plug substantially filling the remainder of the hole in the rotor and holding the capsule against the shoulder, a lead body filling the semi-toroidal recess and surrounding the frusto-conical opening to act as a shield for the capsule, said rotor being operable to move the capsule between an exposed position adjacent the inner end of the frusto-conical opening and a shielded position therefrom through only that arc of rotation which is opposite from the flat face on the brass cylinder and means for operating said rotor, the capsule always being uniformly shielded by the lead body except when in the exposed position where the lead surrounding the frustoconical opening functions to control the radiations from the capsule to produce a conical beam having an apex angle equal to the apex angle of said opening, and the tungsten-alloy plug functions to prevent radiations from emanating through said opening when the capsule is in the shielded position.

4-. The assembly specified in claim 2, the means for rotating the rotor including a shaft attached to the rotor and projecting through the housing, an arm secured to the shaft exterior of the housing, a stop against which the arm rests in the shielded position of the capsule, a spiral spring connected to the shaft and housing to urge the rotor to the shielded position, a cable detachably secured to the shaft for remotely rotating the shaft into the exposed position against the force of said spring, a latch pivotally mounted on the housing so as in a locking position to engage the arm to hold it against the stop and to swing away from the arm across the shaft to release and thus permit the rotor to carry the capsule to its exposed position, the shaft having a recess accommodating such swinging of the arm, the latch being unable to return to said locking position when the arm is away from the stop because the recess in the shaft has moved out of the position in which it accommodates movement of the latch across the shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,477,648 Piggott et al. Aug. 2, 1949 2,642,541 Young June 16, 1953 2,719,926 Proctor et al. Oct. 4, 1955 2,772,361 Hiestand Nov. 27, 1956

Claims

1. A PORTABLE SOURCE OF RADIOACTIVITY COMPRISING A LEAD BODY HAVING SUBSTANTIALLY THE FORM OF A SURFACE GENERATED BY A SEMI-CIRCLE ROTATED ABOUT AN AXIS LYING IN ITS PLANE AND PARALLEL TO BUT SPACED FROM THE FLAT SIDE OF THE SEMICIRCLE THEREBY PROVIDING A CYLINDRICAL HOLE EXTENDING THROUGH THE MIDDLE OF THE BODY, A BRASS HOUSING SURROUNDING SAID BODY PROVIDING A CYLINDRICAL CAVITY THEREIN CONCENTRIC WITH SAID CYLINDRICAL HOLE A CYLINDRICAL TUNGSTEN ROTOR ROTATALY MOUNTED ON ITS AXIS IN THE CAVITY AND COAXIALLY THEREWITH, THE HOUSING AND LEAD BODY BEING PROVIDED WITH A FRUSTO-CONICAL OPENING EXTENDING THERETHROUGH WITH THE SMALLER SECTION OPENING INTO SAID CYLINDRICAL CAVITY AND HAVING ITS AXIS LYING ALONG A LINE WHICH SUBSTANTIALLY BISECTS THE LEAD BODY AT RIGHT ANGLES TO THE AXIS OF SAID CYLINDRICAL CAVITY, THE ROTOR HAVING A CYLINDRICAL HOLE EXTENDING DIAMETRICALLY THERETHROUGH AND COAXIAL WITH SAID FRUSTO-CONICAL OPENING AND HAVING A DIAMETER APPROXIMATELY EQUAL TO THAT OF THE SMALLER END OF SAID OPENING, A SHOULDER ADJACENT ONE END OF SAID HOLE IN THE ROTOR, A CAPSULE CONTAINING THULIUM POSITIONED IN THE HOLE IN THE ROTOR AGAINST SAID SHOULDER, A TUNGSTE ALLOY PLUG SUBSTANTIALLY FILLING THE REMAINDER OF THE HOLE IN THE ROTOR AND RETAINING THE CAPSULE AGAINST SAID SHOULDER, MEANS FOR ROTATING THE ROTOR BETWEEN AN EXPOSED POSITION WHERE THE CAPSULE LIES ADJACENT THE INNER END OF SAID FRUSTO-CONICAL OPENING AND A SHIELDED POSITION 180* AWAY IN WHICH THE OUTER END OF THE TUNGSTEN ALLOY PLUG IS ADJECENT THE INNER END OF SAID FRUSTO-CONICAL OPENING AND PREVENTS RADIATIONS FROM THE CAPSULE FROM EMANATING THROUGH SAID FRUSTOCONICAL OPENING, THE SHAPE OF THE LEAD BODY PROVIDING SUBSTANTIALLY UNIFORM SHIELDING FOR THE CAPSULE IN ALL POSITIONS AND CONTROLLING THE BEAM OF RADIATIONS, WHEN THE CAPSULE IS IN THE EXPOSED POSITION, BY LIMITING IT TO THE SHAPE OF THAT OF THE OPENING.