Production and purification of no-carrier-added 139Ce at the Leipzig cyclotron CYCLONE® 18/9


Production and purification of no-carrier-added 139Ce at the Leipzig cyclotron CYCLONE® 18/9

Mansel, A.; Franke, K.

The global demand for the lanthanides has dramatically increased. Therefore, a detailed understanding of ore chemistry and separation methods is needed. To study these processes, the use of the radiotracer technique is a marvellous method to observe the chemical behaviour of such elements. 139Ce (T1/2 = 137.6 d, Eγ = 166 keV, Iγ = 80%) was chosen as a representative element (radionuclide) for the lanthanide elements. We produced 139Ce using the nuclear reaction 139La(p,n)139Ce by means of irradiation of a few tens mg [natLa]La2O3 at the Leipzig cyclotron CYCLONE® 18/9[1]. At an irradiation time of 3 h, an effective proton current of 2.9 µA and a maximal proton energy of 12.5 MeV, an activity of ~0.5 MBq 139Ce was achieved. The irradiated La2O3 was dissolved in conc. nitric acid and fumed to dryness. For the separation of the radionuclide from the target material, we used the tetravalent oxidation state of cerium by means of an oxidative application with a mixture of dichromate/sulfate in 9 M nitric acid. For the first time, UTEVA® Resin was used to separate the tetravalent cerium (Ce4+) in no-carrier-added (n.c.a.) form from the trivalent lanthanum (La3+) by ion exchange chromatography in column technique, as used for plutonium (Pu4+) separations from trivalent actinides (e.g. Am3+)[2]. The 139Ce4+ ions were washed from the column by 1 mM nitric acid. After evaporation of the combined cerium fractions, the 139Ce was dissolved in 1 mM nitric acid to give a stock solution with an activity concentration of ~1 MBq/ml. The radiochemical yield of n.c.a. 139Ce was 94% ± 5%. With a detection limit of 10 Bq/ml, a concentration range down to ~0.3 pmol/l n.c.a. 139Ce can be achieved. From the dissolution of the irradiated target until preparation of the stock solution, only 5 h are necessary. The chemical purity of the stock solution was evaluated by ICP-MS.
By a weekly in-house production of n.c.a. 139Ce, we can use this radionuclide in our institute (or cooperation partners) for actual studies in liquid-liquid extraction by means of calixarenes or radiolabelling of CeO2-nanoparticles.
References:
[1] C. Vermeulen et al. (2007) Nucl. Instr. Meth. B 255, 331. [2] E. P. Horwitz et al. (1992) Anal. Chim. Acta 266, 25.

Keywords: Lanthanides; No-carrier-added Cerium-139; Proton induced nuclear reaction; Radiochemical separation; UTEVA® Resin

  • Poster
    9th International Conference on Nuclear and Radiochemistry NRC9, 29.08.-02.09.2016, Helsinki, Finland

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Publ.-Id: 23526