Reactor production and purification of osmium-191 for use in a new 191Os/ 191mIr radionuclide generator system

• Published in: International journal of radiation applications and instrumentation. Part A, Applied radiation and isotopes Applied radiation and isotopes, 1989, Vol.40 (2), p.183-191
• Main Authors: Brihaye, C., Dewez, S., Guillaume, M., Callahan, A.P., Rice, D.E., Knapp, F.F.
• Format: Article
• Language: English
• ISSN: 0883-2889
• DOI: 10.1016/0883-2889(89)90196-2

The production of osmium-191 by thermal neutron irradiation of enriched osmium-190 has been evaluated at neutron flux values from 4 × 10 14 to 2.5 × 10 15 neutron cm −2 s −1 in the Oak Ridge High Flux Isotope Reactor (HFIR), the High Flux Brookhaven Reactor (HFBR), and the BR2 reactor in Mol, Belgium. The production route has been analyzed and the cross section values evaluated. The existence of a secondary reaction 191Os(n, γ) 192Os with a cross section value of 740 barn has been demonstrated. In order to obtain 191Os with a specific activity of 250 mCi/mg 190Os, irradiation periods at neutron flux values lower than 2.5 × 10 15 neutron cm −2 s −1 have to be extended up to 2–4 weeks. This results in significantly increased levels of the undesirable 192Ir. The 192Ir is produced by capture of a neutron by 191Ir, which is formed by decay of the short-lived 4.96 s 191mIr daughter produced by β-decay of 191Os. Elution of even small levels of 192Ir from the 191Os/ 191mIr generator results in a large proportion of the total absorbed radiation dose from the generator eluate. Purification of 191Os by conversion to osmium tetroxide and isolation by both distillation and solvent extraction methods has been developed for the efficient removal of 192Ir.