Patent Number: 055966110
Section: summary

FIELD AND BACKGROUND OF THE INVENTION The present invention relates, in general, to methods and systems for separating isotopes from nuclear reactors, and in particular to a method employed in reactors and used for medical isotope production. Beginning in 1945, nuclear reactors were used to produce medical isotopes employing various techniques. U.S. Pat. No. 4,487,738 teaches a method for producing a Cu isotope for diagnostic and experimental medical applications. The Cu isotope is produced by proton spallation combined with subsequent chemical separation and purification. U.S. Pat. No. 3,914,373 discloses a method for separating isotopes by contacting a feed solution containing the isotopes with a cyclic polyether. This method has been applied to clinical, biological and medical research. U.S. Pat. No. 4,158,700 discloses a method of producing radioactive Technetium-99m using a solution containing Molybdenum-99 and Technetium-99m in conjunction with a chromatographic column and eluting it with a neutral solvent system comprising an organic solvent for producing Technetium-99m as a dry, particulate residue. U.S. Pat. No. 3,799,883 discloses dissolving uranium material in aqueous inorganic acid then precipitating Mo-99 using alpha-benzoinoxime. An article entitled "Study of the Separation of Molybdenum-99 and Recycling of Uranium to Water Boiler Reactor" by W. L. Cheng, et al., Appl. Radiot. Isot., Vol. 40, No. 4, pp. 315-324, 1989, teaches a process which includes the separation of Molybdenum-99 from uranium sulfate fuel solution with an .alpha.-benzoin oxime precipitation and purification by chelating ion exchanger, alumina, and calcium phosphate hydroxide as adsorbents. Although the isotope Molybdenum-99 (Mo-99) is an isotope commonly used in the medical field, only one method exists for the production of medical isotopes such as Mo-99 that is approved by the United States Food and Drug Administration. This method comprises extracting the fission product, Mo-99, from a Uranium-235 target which has been irradiated in a neutron flux provided by a large nuclear reactor. Because these nuclear reactors are used for other purposes besides producing medical isotopes, the reactor power is high, usually 20,000 to 200,000 kilowatts. When producing medical isotopes this power output by the nuclear reactor is extremely wasteful. SUMMARY OF THE INVENTION The present invention comprises a low power, low cost method for use with a nuclear reactor, which extracts medical isotopes from the fission products produced by the reactor. The present invention is directed toward replacing nuclear reactors employing the reactor-target systems using reactors operating at a power of about 200 kilowatts (e.g. 100 to 300 kilowatts) for producing medical isotopes such as Mo-99. Current reactors using the reactor-target system are operated at a power of 20,000 or more kilowatts when producing medical isotopes resulting in heat and radioactive waste of at least 100 times the basic requirement. The present invention provides a method for producing medical isotopes such as Mo-99 from either an aqueous-homogeneous or water boiler reactor or from a gas-cooled reactor. The present invention provides for the production of medical isotopes using a method for treating the fission products in either liquid or gas form through interaction with inorganic or organic chemicals in order to extract the medical isotopes. An object of the present invention is to provide a nuclear reactor which can be dedicated solely to the production of medical isotopes using a simple and direct treatment procedure. Another object of the present invention is to provide a method of medical isotope production which reduces the amounts of radioactive waste and heat dissipation by two orders of magnitude for each unit of medical isotope produced. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.