Quick viewing(Text Mode)

Production of I-123

Production of I-123

United States Patent [191 L I I I 3,971,697 Blue 1451 July 27, 1976

PRODUCTION OF lsnI 3,018,159 111962 Silverman ...... 423/249 3,694,313 911972 Blue et al ...... 176116 Inventor: James W. Blue, Bay Village, Ohio OTHER PUBLICATIONS Assignee: The United States of America as represnted by the National Bulletin of the Chemical Society of Japan, Feb. 1970, Aeronautics and space vol. 43, No. 2, p. 576, Kat0 et al. Administration, Washington, D.C. and Radiation Technology, vol. 4, No. 3, Filed: July 12, 1973 1967, pp. 275-280. Uses of in Chemistry, Metallurgy and Biol- Appl. No.: 380,046 ogy, Proc. Conf., Sept. 1969, pp. 138-148, Blue et al. Related U.S. Application Data Continuation-in-part of Ser. No. 247,434. April 25, Primary Examiner-Harvey E. Behrend 1972. Attorney, Agent, or Firm-N. T. Musial; G. E. Shook; John R. Manning U.S. CI...... 176111; 176116; 176114; 2501400; 2501429; 2501492 R [571 ABSTRACT Int. C1.* ...... G21G 1/10 Field of Search ...... 17611 1, 16, 14; Bombarding a cesium heat pipe with high energy par- 4231249; 2501429, 400, 492, 432 ticles causes a spallation reaction which produces va- pors of lZ3Xeand contaminants. The contaminants are References Cited removed in a dry ice cold trap while the con- denses in a liquid trap where it decays to UNITED STATES PATENTS "',. 2,795,482 611957 McNabney ...... 4231249 6 Claims, 1 Drawing Figure 3,971,697 3,971,697 1 2

PRODUCTION OF 1231 DESCRIPTION OF THE PREFERRED EMBODIMENT ORIGIN OF THE INVENTION Referring now to the drawing there is shown a target The invention described herein was made by an em- assembly which extends into a beam duct 12 of a high ployee of the United States Government and may be energy accelerator. It is contemplated the target assem- manufactured and used by or for the Government for bly 10 may be used with the LOS ALAMOS MESON governmental purposes without the payment of any FACILITY, known as LAMF. Another high energy royalties thereon or therefor. accelerator located in Canada, called TRIUMF, would STATEMENT OF COPENDENCY lo be a suitable source of high energy particles. The beam in the duct 12 from such accelerators is characterized This application is a continuation-in-part of applica- by high energy between 200 MeV and 2000 MeV and tion serial No. 247,434 which was filed Apr. 25, 1972. high current. BACKGROUND OF THE INVENTION The target assembly 10 is in the form of a heat pipe l5 which comprises a tubular container 14 having a supply This invention is concerned with the production of 16 of cesium-133 in the end which extends into the high purity radioiodine for measurements and beam duct 12. The opposite end of the tube 14 which as a general . The invention is particularly protrudes from the duct 12 is surrounded by cooling directed to the utilization of a heat pipe in the produc- coils 18. A suitable cooling fluid, such as water, is cir- tion of radioisotopes using very intense particle accel- *O culated through the coils 18. erators. A porous metal plug 20 is mounted in the container Radioactive is used for medical diagnostic 14 adjacent to the cooling coils 18. A wick 22 extends studies. The 1311 has been used for this purpose along the inner wall of the tube 14 between the plug 20 because of its availability. The radioisotope lBI is con- 25 and the cesium 16. sidered much superior to the I3lI in studies where the A tube 24 connects the inside of the container 14 to amount of radiation exposure to a patient is of prime a cold trap 26 through a valve 28. Tygon tubing has concern. Because of the shorter half-life and the decay been satisfactory for the tubular conduit 24. The cold by , the radiation exposure received by trap 26 comprises a U-tube 30 immersed in a coolant in the patient from IZ3I is about one-fortieth that of an 3o an insulated container 32. A one-fourth inch equal amount of l3II. U-tube surrounded by solid COz in a Dewar has been lBI is also superior to 1311 because the satisfactory. The dry ice maintains a trap 26 at a tem- energy of lZ3Iis 159 KEV compared to 364 KEV of 1311. perature of -79°C. Collimators operate more effectively with this lower A valve 34 connects the dry ice trap 26 to a second energy. Also the collimators used with lZ3I are less cold trap 36. A one-fourth inch copper U-tube 38 im- bulky. 35 mersed in liquid nitrogen in a Dewar 40 has been satis- A method of lZ3I production is disclosed in U.S. Pat. factory for the cold trap No. 3,694,3 13. The method disclosed in this patent has 36. The liquid nitrogen main- been quite successful in terms of freedom from radio- tains the trap 36 at a temperature of -196°C. A valve active impurities. However, the method is not capable 42 is used to isolate the trap 36 or connect it to a vac- ' of handling the power densities involved in using high 40 uum pump 44. energy, high current machines. In operation, a beam of high energy protons identi- fied by the arrow in the duct 12 penetrates the tubular SUMMARY OF THE INVENTION container 14 and strikes the cesium-I33 in the target According to the present invention cesium is used assembly 10. The beam penetrating the cesium causes both as the working fluid of a heat pipe and as the 45 what is known in nuclear physics as a spallation reac- target material for high energy protons. A spallation tion which produces Iz3Xe according to the reaction reaction produces lZ3Xeand many radioactive contami- 13Ts (p,p 10n)Iz3Xe. nants which pass from the heat pipe to low temperature This is only one of a number of reactions that to traps where the undesirable contaminants are removed. significant impurities. Some of these reactions are 133C~ The is held for a of time sufficient for it to 50 (p, 2p 8n)1241,'=Cs (p, 2p 7n)lZ5I,133Cs(p, 2p 6n)lZ6I, decay to lZ3l. 13Ts (p, 3p 8n)lZ3Te,lmCs (p, 4p 6n)Iz4Sb. To produce these spallation reactions the incident OBJECTS OF THE INVENTION proton must have an energy greater than 200 MeV. It is, therefore, an object of the invention to produce The first three reactions produce the radioactive io- the radioisotope IBI with high energy particles from 55 dines Iz4I, lZ5I and IZsI. These radioactive would very intense particle accelerators. seriously contaminate the desired lZ3I because they Another object of the invention is to produce lZ3I cannot be chemically separated. The other impurities using a heat pipe that is bombarded with high energy formed by the above listed reactions could be sepa- particles. rated chemically because they are different elements. These and other objects of te invention will be appar- 60 However, this is not necessary in the heat pipe device ent from the specification which follows and from the because all of the imwrities have a lower vapor pres- drawing wherein like numerals are used throughout to sure than the desired lz3Xe and can be coliected on identify like parts. cool surfaces at the heat rejection end of the heat pipe. Radioactive , , , DESCRIPTION OF THE DRAWINGS 65 , , and cesium are all contaminants. The drawing is a schematic view of an apparatus for All of the isotopes of and could be producing radioactive iodine in accordance with the accelerated to hundreds of MeV and produce the de- invention. sired spallation reaction. An example would be 13Ts(cy, 3,97 1,697 3 4 3p Pln)"%e. The same contaminants as produced by fer properties, such as enthalpy, melting point, boiling proton bombardment would also be produced. point and vapor pressure-temperature curve. No other The beam penetrating the cesium-I33 deposits en- element has these properties together with the nuclear ergy in the cesium that heats this target to the point requirements as required by the target material. where it vaporizes. All charged particle beams lose 5 Although the preferred embodiment has been shown energy by ionizing and exciting electrons on the atoms and described it is contemplated that various structural of the stopping material, such as cesium. The individual modifications may be made to the disclosed apparatus particles that make up the beam actually lose velocity without departing from the spirit of the invention or the in a continuous manner. This energy lost by the beam scope of the subjoined claims. By way of example, it is appears as heat, and if the beam current is large enough 10 contemplated that different trap configurations could this heat will melt metallic cesium and vaporize it. The be utilized. The trap 26 could be a chemical trap, such vapor is transported to the end of the tubular chamber as hot , to remove radioiodine impurities. The 14 where it is cooled by the cooling coils 18. The tem- IznXe trap 36 could work on the absorption principle. perature at the hot end of the heat pipe is 670°C which The trap 34 could also contain a pharmaceutical is the boiling point of cesium. The temperature at the 15 compound that would become tagged or labeled when cold end is above the melting point and below the boil- the xenon decays to iodine. It is generally desirable to ing point of cesium. This temperature must be above select a pharmaceutical that goes to a specific organ the melting point for the apparatus to be suitable for its where it is involved in some metabolic process. Hippu- intended use because the cesium must condense as a ran goes to the kidney and has been tagged with lmI by liquid thus giving up the heat of vaporization. Then as 20 placing it on the walls of a container and condensing a liquid the cesium flows back to the hot end of the heat IZ3Xeon these same walls. Other pharmaceuticals that pipe. It is not difficult to achieve this condition in prac- could be labeled are human serum albumin, choles- tice because the cesium vapor column and the cesium terol, dopamine and . condensed on the wall of the heat pipe make the col- What is claimed is: umn nearly isothermal. 25 1. In combination with a high energy accelerator In one embodiment it is possible to have a sharp having a duct containing a beam of particles having temperature drop when the column is run as a two high energy between 200 MeV and 2000 MeV and component heat pipe where one phase is a non-conden- current sufficiently high that the total beam power is sible gas. Even in this embodiment it is not difficult to greater than two kilowatts, apparatus for producing lZ3I achieve heat pipe operation although there may be 30 comprising some solid cesium on the walls. a heat pipe comprising a tubular container extending The cesium condenses at this cool end of the tube. into said duct, a portion of said tubular container The beam power that was deposited in the cesium is being in the path of said high energy beam, rejected to the coolant that flows in the coils 18. a supply of cesium 133 in said portion of said tubular Some small amount of cesium vapor may be trans- 35 container in said beam, said cesium 133 being ported through the plug. However, most of the cesium bombarded by said beam thereby vaporizing the vapor will be collected on the cool walls because the same and producing radioactive vapor has a greater opportunity to contact the cool including lZ3Xeand contaminants selected from the

walls than the plug. The lZ3Xe, lZ5Xe,lZ3I t, lZ4I lZ5I, lZ6I, consisting of iodine, tellurium, antimony, tin, and lz9I will pass through the plug plus smaller amounts 40 indium and cesium by spallation, of other contaminants. All these elements passing the cooling means around a portion of said tubular con- plug will be subsequently stopped by cooler surfaces tainer remote from said portion of said beam for except for xenon. Xenon will not be collected until it is condensing said vaporized cesium, pure and free of contaminants. a first trap connected to said heat pipe for receiving The IZ3Xeand other volatile contaminants also travel 45 said radioactive isotopes of xenon and the contami- to the cool end of the tube 14 where they pass through nants after the same have vaporized and removing the tube 24 and valve 28 to the cold trap 26. The po- said radioactive isotopes of said contaminants, and rous metal plug 20 prevents accidental transport of a second trap connected to said first trap for receiv- liquid cesium into the trap 26 which might take place ing said radioactive isotopes of xenon therefrom where boiling occurs. The vapors of radioactive con- 50 and removing the same, said second trap forming a taminants condense in the trap 26. container for holding said radioactive isotopes of The lzsXe is still a vapor and passes to the trap 36 at xenon for a period of time sufficient for the Iz3Xe to liquid nitrogen temperature. The IZ3Xe condenses in decay to IUI. the trap 26. The removal of the xenon from the vapor 2. Apparatus.. as claimed in claim 1 wherein the first phase produces a pumping action that causes almosi all 55 trap contains solid dioxide. the xenon that is produced to be transported to the trap 3. Apparatus as claimed in claim 1 wherein the 36. cooled portion of the heat pipe extends outside the The cesium vapors that condense in the heat pipe at duct. the coils 18 are transported back to the target area by 4. Apparatus as claimed in claim 1 including a porous capillary action of the wick 22. It is also contemplated 60 metal plug in said heat pipe adjacent to said cooling that grooves in or on the inner wall of the tubular con- means for preventing cesium from being transported to tainer 14 may be used to transport the condensed ce- said first trap. sium vapors back to the target area. 5. Apparatus as claimed in claim 1 wherein the sec- It is apparent the target assembly 10 uses cesium as ond trap contains a pharmaceutical compound both a heat pipe working material and as a target mate- 65 whereby said Pharmaceutical compound is tagged rial for the production of radioisotopes by high energy when the IzsXe decays to IZ3I. charged particles. Cesium -133 is the preferred work- 4. In apparatus for producing wherein radioactive ing material because of the uniqueness of its heat-trans- isotopes of xenon including IZ3Xe and contaminants 3,97 1,697 5 6 selected from the group consisting of iodine, tellurium, and the other end in communication with said cold antimony, tin, indium and cesium are passed through traps, and cold traps to sequentially remove the radioactive iso- a supply of cesium 133 target material in said one end topes of contaminants and xenon, the improvement of said heat pipe whereby said cesium 133 is bom- comprising barded by said beam thereby vaporizing the same a beam of protons having an energy greater than 200 and producing the radioactive isotopes of xenon MeV, and contaminants by spallation. a heat pipe having one end extending into said beam ***** 10

15

20

25

30

35

40

45

50

55

60

65

Top View