US2710249A - Iodine-132 generator and shipping container - Google Patents

Description

June'7, 1955 w, E W|N$CHE ET AL 2,710,249

IODINE-la GENERATOR AND SHIPPING CONTAINER Filed Nov. 29, 1951 hr( Il FIG. l.

INVENTOR WARREN E WINSCHE 0l/l5 6. STANG; JR,

BY WAL TER D. TUCKER GERALD J. SELV/N IGIENE-132 GENERATR AND SHIPPING CONTAINER Warren E. Winsche, Wiinlington, Del., and Louis G. Stang, Jr., and Walter D. Tucker, Sayville, and Gerald J. Selvin, East Patchogue, N. Y., assignors to the United States of America as represented by the United States Atomic Energy Commission Application November 29, 1951, Serial No. 258,794

5 Claims. (Cl. 23-216) This invention vrelates to the production of radioactive iodine. More particularly the invention relates to a novel source of iodine-132, a new method of recovering the radioactive iodine-132 in substantially pure form from this source, and apparatus particularly adapted to carry out the method of the invention.

ln recent years extensive uses have been developed for radioactive iodine in the medical and biological elds, wherein it has been used as a tracer for investigative and diagnostic purposes and also, in particular cases as a therapeutic agent. Heretofore it has been customary to use iodine-131 for these purposes, both because ot` the ready availability of this isotope and because its half life of 8 days is in the range where the activity of the iodine remains at a useful level for a sur/iicient period of time to permit its shipment to relatively distant points of use. However for many clinical and therapeutic purposes a short-lived isotope can be used and in fact is more desirable than a long-lived isotope. For example, in the socalled Smith and Quimby method for determining blood circulation time, less than two minutes is required to make the determination. Also in certain known methods of locating rain tumors with di-iodolluorescein containing radioactive iodine the measurement of radiation must be made in the lirst two hours after the radioactive material has been injected, since the tumor starts to throw oli' the dye after that time.

ln cases where the nature of the objective sought permits a short-lived isotope to be used, the use of such an isotope yields substantial advantages. Thus the isotope decays rapidly after it is no longer needed, and hence within a relatively short period of time a second test or treatment can be made. /Also the amount of radiation received by the whole body is minimized, and so is that received by such organs as the kidneys through which the radioisotope must pass before beine eliminated. A further advantage of the shorterived isotope resides in the fact that when such isotopes are used there is no problem of disposing of radioactive wastes eliminated by the body.

A study of the known radioactive isotopes indicates that iodine-132 with a half-lite of 2.4 hours is well suited for many applications of the type outlined above. However, its half-life is so short that it cannot be packaged in the conventional manner and shipped to a considerable distance without losing an excessive proportion of its activity.

l't is accordingly an object of the present invention to provide a novel source of iodine-132 and a novel method of packaging this source which permits eiiective use of iodine-132 from the source after the package has been shipped a considerable distance. lt is another object of the invention to provide a container for the source as well as means for causing the iodine-132 to be delivered from the container or package in controllable amounts at the point of use. Other objects of the invention will be in part obvious and in part pointed outV hereafter.

In general the objects of the present invention can be nited States Patent achieved by dispersing tellurium-l32, which is the radioactive parent of iodine-132, in a solid but readily liqueliable vehicle. The tellurium may be in either elemental form or in the form ofv a suitable tellurium compound. Tellurium-l32, which has a half-life of 77 hours occurs in the fission products resulting from the irradiation of natural uranium in a nuclear reactor and can be readily separated from these fission products. lodine-l32 formed in the solid mixture of telluriu1n-l32 and vehicle remains imprisoned therein until removed by the method described below. The solid mixture is the source of iodine-132 referred to above and is preferably packaged in a special container for shipment and storage, the container being so constructed as to permit the source to be milked at the point of use to obtain controllable quantities of iodinel32 therefrom. This milking can be carried out, for example, by heating the source to liquefy it and passing a stream of a suitable dry gas, such as air, through the liquid mixture to remove the iodine-132 therefrom.

The many objects and advantages of the present invention can best be understood and appreciated by reference to the accompanying drawing which illustrates con tainer apparatus adapted to contain the iodine source of the present invention and capable of being used to carry out the method of the invention. ln the drawing:

Figure l is a schematic vertical section through the container showing the iodine generator centrally located therein, flanked by an air drying chamber on the right and an absorbing chamber on the left, and also showing the piping interconnecting the chambers and a control valve for regulating ilow through the chambers, and

Figure 2 is a horizontal section through the control valve of Figure l taken through the upper set of ports of the valve.

Referring to the drawing, the numeral lt) designates a container or casing within which are located an iodine generator i2, an absorber lli, and an air dryer 16. The generator l2 includes `an inner chamber 18 which contains a body 2t) of the iodine source material referred to above. This material is preferably a solid solution of a suitable tellurium-l32 compound, such as the dioxide, in a suitable readily fusible vehicle, such as, for example, a eutectic mixture of lithium and potassium chlorides. It can be conveniently charged into chamber 18 as an aqueous solution by removal of filling plug 19 at the top of the chamber, and converting to the desired solid form by driving otf the water of solution by heat supplied by a heating element 24.

The chamber i8 is surrounded by a sleeve 22 of insulating material that supports the electrical heating element 2d, the ends of which are connected by conductors 26 to the terminals 28. As shown, generator l2 is supported and positioned by legs 3b which rest upon the bottom of casing itl, and the terminals 28 are located in the space between the bottom of generator l2 and the bottom of casing lb. Electrical energy to heat the element 24 can be supplied to terminals 23 from a suitable source (not shown) by the lead 32. The space between chamber 13 and the outer casing of generator l2 is filled with insulation 34 to minimize heat loss from chamber i8. lt will be understood that the function of element 24 is to heat and thereby fuse the source material 2tl when it is desired vto withdraw radioactive iodine from the generator and that the element 2st is connected to a source of electrical energy only when it is desired to melt the material 20.. To measure the temperature of the source material a thermocouple well 35 containing a rhermocouple 3S is provided, the lower end of which is embedded in the body 2() of source material and the upper endvof which extends through the top of casing lil.

The absorber i4 is sirnilar to the generator 12 in construction in that it includes an inner chamber 4l), in-

sulating sleeve 42, heating element 44, conductors 46, terminals 48, legs 50, lead 52, insulation 54, thermocouple well 56 and thermocouple 58, all similar to the corresponding parts of generator 12. However, in place of the source material 20 of chamber 18 the chamber 40 contains a body 60 of a suitable absorbing agent for iodine, such as for example, silver nitrate. As will be described more fully hereafter, the generator 12 should be purged before it is used as a source of iodine- 132 and the function of absorber 14 is to absorb iodine delivered by generator 12 during this purging step.

The drier 16 comprises a casing 62 supported and positioned by legs 64 that rest on the bottom of causing 10. The drier is charged with a suitable water-absorbing material 66 such as silica gel and is provided with a gas inlet tube 68, the discharge end of which extends into the silica gel bed. The top of drier 16 is conected to generator 12 by a pipe 7), the discharge end of which extends into the body 20 of source material.

In operation of the device a gas, for example atmospheric air, is drawn through pipe 63 into drier 16 wherein it is dried. The dry gas then flows through pipe 70 and bubbles through the molten mixture of tellurium-l32 dioxide and alkali metal chlorides in such a way as to pick up iodine-132 contained in the mixture. Flow of iodinecontaining gas from generator 12 is controlled by a valve 72 comprising a rotatable plug 74 and housing 76. The housing 76 contains a series of three lower ports 78, Si), and 82 and a series of three upper ports 84, 86, and 8S. The plug 74 has a lower passage 9) and upper passage 92 adapted to interconnect adjacent ports as best indicated in Figure 2. Ports 82 and 33 are interconnected within housing 76. The plug 74 is provided with an upwardly extending actuating rod 94 having at its upper end a handle 96 by means of which the valve plug can be turned.

As shown in Figure 1, port 78 of housing 76 is connected by a pipe 98 with a point within chamber 40 near the bottom of silver nitrate bed 60; port Sti is connected to the top of chamber 18 by a pipe 100; port 84 is connected to the top of chamber 40 by a pipe 102; and port 86 is connected by a pipe 1M to an absorber 110 containing a suitable absorbing medium through which iodinecontaining gas is pulled by a pump 106, the iodine-free gas being discharged through pipe 108.

It may be noted that the container 10 is adapted to perform the dual function of encasing the generator absorber and drier and also acting as a radiation shield to prevent escape of a harmful amount of radiation.

The manner in which the apparatus shown in the drawing can be used to carry out the method of the present invention should be largely apparent from the foregoing description. The chamber 18 is initially charged with a mixture of tellurium.-132 or a tellurium-l32 compound and a normally solid but readily liqueable vehicle. The use of a solid mixture is advantageous since the radiation hazard that might be created by breakage of a package containing a radioactive liquid or gas can be largely avoided by shipment of the material in solid form. Also the solid vehicle serves to imprison the radioactive iodine- 132 as it is formed by decay of the tellurium-l32.

When it is desired to remove iodine-132 from the apparatus for use, the generator is rst purged free from iodine-132. To accomplish this purging the heating elements 24 and 44 are energized to melt the contents of the generator and absorber, valve 72 is positioned to interconnect the generator and absorber, and a gas is drawn into the system through pipe 63 by pump 166. The gas passes through the molten iodine source 20, where it picks up iodine-132, and then through the molten body of silver nitrate wherein it is absorbed. Upon completion of the purging step the heating elements are de-energized, pump 106 shut off and the apparatus allowed to stand for a predetermined interval until the desired quantity of iodine- 132 has accumulated. The iodine source is then remelted, valve 72 positioned to cause the iodine-bearing gas stream to by-pass the absorber, and gas is drawn through the molten source to remove iodine-132 therefrom for use.

From the known properties of the radioactive materials used and by means of known mathematical relationships it is possible to calculate quite precisely how long the apparatus should stand after completion of a purging step in order to build up in the generator a predetermined desired quantity of radio-iodine. For any given source the maximum build-up of iodine will occur about 12.4 hours after purging. If less than the maximum quantity of iodine is desired this lesser amount can be readily and accurately obtained by using a shorter time interval between purging and milking of the generator.

It is of course to be understood that the foregoing description is illustrative only. Thus the tellurium-l32 may be incorporated in compounds other than the dioxide, such as one of the chlorides, bromides or iodides or tellurous acid. Also although the preferred vehicle material, as previously indicated, is an eutectic mixture of lithium and potassium chlorides, numerous other readily liquetiable vehicles e. g. zinc chloride, may be used and these may or may not be salt mixtures. When elemental tellurium is used it can be conveniently dispersed in ferrie nitrate or elemental sulfur. Also tellurium in the form of telluric acid may be added to a hot gelatine solution to form a jelly. Any iodides formed from the generated iodine are oxidized to free iodine by an excess of the telluric acid. The jelly can be liquefied by heating as described above or by adding water thereto. The tellurium-l32 used may or may not be associated with a non-radioactive vehicle such as natural tellurium.

lt may be further noted that the silica gel in drier 16 can be replaced by other known drying agents, and the silver nitrate of absorber 14 can be replaced by other known iodine absorbing agents. Other modifications within the scope of the invention will be apparent to those skilled in the art.

We claim:

l. A method of producing a gaseous stream containing radioactive iodine which comprises forming a solid mixture comprising a liquefiable vehicle and tellurium-l32, confining said mixture in a closed vessel to cause iodine-132 formed by decay of said Te132 to accumulate therein, liquefying said mixture in said vessel, and passing a dry gas inert to the vehicle containing the iodine through the molten mixture to remove iodine therefrom.

2. A method of producing a gaseous stream containing radioactive iodine which comprises forming a low melting point, solid mixture comprising tellurium-l32 and a fusible vehicle, confining said mixture in a closed vessel to cause iodine-132 formed by decay of said tellurium-l32 to accumulate therein, heating said mixture in said vessel to melt the same, and passing a dry gas inert to the vehicle containing the iodine through the molten mixture to remove iodine therefrom.

3. The method of producing a gaseous stream containing radioactive iodine which comprises forming a low melting point, solid mixture of a tellurium-l32 compound and a fusible vehicle, confining said mixture in a closed vessel to cause iodine-132 formed by decay of said tellurium-l32 to accumulate therein, heating said mixture in said vessel to melt it, passing a stream of dry air in sequence through the molten mixture and then through a bed of a substance capable of absorbing iodine from said stream for a period sufficient to purge said molten mixture of iodine, and thereafter continuously passing air through said molten mixture and conducting it to a point of use without passing it through said absorbent bed whereby said stream contains freshly formed iodine-132.

l. The method of producing a gaseous stream contain- .ing radioactive iodine which comprises forming a solid solution of tellurium-l32 dioxide in a mixture of lithium and potassium chlorides, confining said solid solution in a closed vessel to cause iodine-132 formed by decay of said tellurium-l32 to accumulate therein, heating said y therefrom.

5. Apparatus for generating a radioactive vapor comprising in combination a casing; a generating chamber, a purging chamber and a gas drying chamber mounted in said casing, said generating chamber being interconnected with both said drying chamber and said purging chamber, both said generating chamber and said purging chamber having a container located therein for receiving a quantity of a solid material, each of said containers being provided with heating means for heating the solidl contained therein; pump means connected to said chambers to produce a flow of gas through said drying chamber, generating chamber, and purging chamber in sequence to a discharge conduit; and valve means connected to said generator chamber, said purging chamber, and said discharge conduit and selectively movable to interconnect directly said generating chamber and discharge conduit to bypass said purging chamber.

References Cited in the le of this patent UNITED STATES PATENTS 6 1,461,340 Adams July 10, 1923 1,594,491 Bilstein Aug. 3, 1926 1,705,614 Griswold Mar. 19, 1929 1,708,287 Turrentine Apr. 9, 1929 1,844,563 Curtin Feb. 9, 1932 1,956,948 Fattinger et al. May 1, 1934 1,994,416 Girvin Mar. 12, 1935 2,086,825 Simpson July 13, 1937 2,120,218 Heath et al. June 7, 1938 2,314,827 Hortvet Mar. 23, 1943 2,462,241 Wallhausen et al. Feb. 22, 1949 2,559,259 Rapter July 3, 1951 OTHER REFERENCES Coryell and Sugarman, Radio-Chemical Studies, the Fission Products, Natl Nuclear Energy Series, 1951, Book 1, page 124.

Claims (1)

1. A METHOD OF PRODUCING A GASEOUS STREAM CONTAINING RADIOACTIVE IODINE WHICH COMPRISES FORMING A SOLID MIXTURE COMPRISING A LIQUEFIABLE VEHICLE AND TELLURIUM-132, CONFINING SAID MIXTURE IN A CLOSED VESSEL TO CAUSE IODINE-132 FORMED BY DECAY OF SAID TE132 TO ACCUMULATE THEREIN, LIQUEFYING SAID MIXTURE IN SAID VESSEL, AND PASSING A DRY GAS INERT TO THE VEHICLE CONTAINING THE IODINE THROUGH THE MOLTEN MIXTURE TO REMOVE IODINE THEREFROM.

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