Limitation of the long-lived 121Te contaminant in production of 123I through the 124Xe(p,x) route

Abstract

The 13.2 h half-life radioisotope (123)I is widely used in clinical nuclear medicine diagnosis. At present it is mostly produced in nca form by proton irradiation of highly enriched (124)Xe in dedicated gas target set-ups and relying on the decay chain (123)Cs-(123)Xe-(123)I. Depending on the irradiation conditions contamination with long-lived (121)Te, a daughter product of the co-produced rather short lived (121)I, occurs and can limit the useful shelf life of the (123)I solution. Excitation function of the (124)Xe(p,α)(121)I, (124)Xe(p,2n)(123)Cs and (124)Xe(p,2p)(123)Xe reactions are measured up to 35 MeV using the stacked gas cell technique and high-resolution γ-ray spectrometry. The experimental data were compared with the earlier literature values, with new results of the ALICE-IPPE and EMPIRE-II codes and with the data taken from the TENDL-2009 database. Existing discrepancies in cross-section data are largely solved and new recommended values are proposed. From fits to the new excitation curves integral (123)I batch yields and (121)Te contaminations for realistic production conditions are derived. Optimization of irradiation and cooling times and energy degradation in the target can strongly influence the contamination level.