Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Radioactive metal
Reexamination Certificate
2000-07-14
2001-04-10
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Radioactive metal
C423S021100, C423S021500, C423S068000, C423S069000, C423S085000, C423S139000, C423S150100, C423S157000, C423S158000
Reexamination Certificate
active
06214301
ABSTRACT:
This invention relates to radioisotope production and radiochemical separations and more particularly to hafnium radioisotope recovery from irradiated tantalum.
BACKGROUND ART
Tantalum is irradiated, generally with protons, for use as a target material. Naturally occurring tantalum having therein tantalum-180 and tantalum-181 is irradiated to form the target materials. After a number of years of decay, depending upon the half-lives of the isotopes, most of the hafnium radioisotopes such as hafnium-172, hafnium-173, hafnium-175 and hafnium-179
m
decay away, leaving higher proportionate amounts of hafnium-178
m2
. After the tantalum is irradiated for employment as a target material, it is useful to be able to recover the hafnium radioisotopes for a variety of uses including use as precursors for radioactive materials for medical diagnosis and treatment and use for nuclear physics studies, including use in gamma ray lasers.
Traditionally, separation techniques for recovering hafnium isotopes from irradiated tantalum which has been irradiated employ solvent extractions with reagents that are now considered hazardous. The solvent extraction techniques are now considered problematic because solvent extraction techniques generate a mixed-waste stream containing radioactive and hazardous components that cannot easily be treated for disposal.
Therefore, there is a need for methods of recovering hafnium radioisotopes from irradiated tantalum targets without creation of undesirable waste streams.
It is an object of this invention to provide a method for obtaining hafnium radioisotopes from irradiated tantalum.
It is another object of this invention to provide a solvent-free method for recovering hafnium-178
m2
from irradiated tantalum.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. The claims appended hereto are intended to cover all changes and modifications within the spirit and scope thereof.
DISCLOSURE OF INVENTION
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, there has been invented a method for recovering hafnium from irradiated tantalum comprising:
(a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum;
(b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution;
(c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate;
(d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution;
(e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange; (f) separating fluoride complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride, adjusting the solution to an alkaline pH, and heating to obtain a second precipitate containing the hafnium and iron;
(g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron;
(h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange;
(i) drying the ion exchanged hafnium solution to obtain hafnium-178
m2
, hafnium-172 and lutetium-172.
Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by an additional cation exchange, then a second anion exchange, can be performed.
REFERENCES:
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Taylor, Wayne A. and David J. Jamriska, “Recovery of Hafnium Radioisotopes from a Proton Irradiated Tantalum Target,” 4thInternational Conference on Methods and Applications of Radioanalytical Chemistry, Kailua-Kona, Hawaii (Apr. 1997).
W. A. Taylor, J. G. Garcia, V. T. Hamilton, R. C. Heaton, D. J. Jamriska, M.A. Ott, D. R. Phillips and S. D. Radzinski, “Recovery of Hafnium Radioistopes from a Proton Irradiated Tantalum Target,” J. of Radioanalytical and Nuclear Chemistry, vol. 236, Nos. 1-2, (1998), pp. 155-157, no month.
Rebecca J. Daniels, Patrick M. Grant and Harold A. O'Brien, Jr. “The Protection, Recovery, and Purification of172Hf for Utilization in Nuclear Medicine as the Generator of172Lu,” International Journal of Nuclear Medicine and Biology, vol. 5, pp. 11-17, 1978, no month.
Yu Ts Oganessaint, S. A. Karamiant, Y.P. Gangrskit, B. Gorskit, B. N. Markovt, Z. Szeglowskit, Ch Briancon, D. Ledu, R. Meuniert, “Production, Chemical and Isotopic Separations of the Long-lived Isomer178HFm2(T{fraction (1/2 )}= 31 years),” Nucl. Part. Phys. vol. 18, (1992) pp. 393-399, no month.
J. B Wilhelmy, G. E. Bentley, K. E. Thomas, Ronald E. Brown, E. R. Flynn, J. Van der Plicht, L. G. Mann and G. L. Struble, “Nuclei from Stability Using Exotic Targets,” 4thInternational Conference on Nuclei From Stability, Helsingor, Denmark, Jun. 7-13, 1981, pp. 684-689.
Jamriska David J.
Taylor Wayne A.
Bennett Gemma Morrison
Bos Steven
The Regents of the University of California
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