Apr 18 – 23, 2010
Casino Conference Centre
UTC timezone

Optimisation of the long lived <sup>121</sup>Te contaminant in production of <sup>123</sup>I trough the <sup>124</sup>Xe(p,x) route

Apr 20, 2010, 4:00 AM
Red Hall (Casino Conference Centre)

Red Hall

Casino Conference Centre

Reitenbergerova 4/95, Marianske Lazne, Czech Republic
Verbal Production and Application of Radionuclides Production and Application of Radionuclides 1


Prof. Alex Hermanne (Cyclotron, Vrije Universiteit Brussel)


At present the preferred route for 123I (T1/2 = 13.2 h) production is bombardment of highly enriched 124Xe with 35 MeV protons and taking advantage of the cascade decay 123Cs-123Xe-123I. After irradiation the gas targets are allowed to cool for 7 h ensuring optimal in-growth of 123I from its precursors. A separation of I from all other elements is performed resulting in a nca, pure solution. An unavoidable contaminant is 121I (T1/2 = 2.12 h) produced by 124Xe(p,α) reaction with a cross section maximum around 20 MeV. This rather short lived radioiodine will disappear quickly from the 123I solution, but its long lived decay product 121gTe (16.8 d) accumulates and impairs the late use (several half lives of 123I after calibration date) of the solution.This situation could be improved by lowering the 121I production through limitation of the target thickness and imposing a higher exit energy. As the only values for the 124Xe(p,α) reaction were reported by Tarkanyi et al. [1] at higher energy, reliable data on the excitation function need to be measured for the first time. Highly enriched 124Xe was bombarded with protons between 13 and 37 MeV with the double aim of determining cross sections for 121I production and resolving discrepancies existing in the previously published values for production of 123Cs and 123Xe [2]. Here only results for 121I are presented and compared with results from different theoretical codes. In the experimental (and production) conditions formation of 121Cs and 121Xe are impossible or extremely low (practical threshold of 1 mb at 38 MeV [1]). Direct formation of 121gTe (16.8d) or 121mTe (154d) through the (p,3pn) reaction are not of importance because of the needed chemical separation at EOB+ 7 h . The cross sections for 121I production show a practical threshold at 9.5 MeV rising to a maximum of 13 mb at 21 MeV, not in agreement with theoretical results. From a fit to our excitation curve, production yields for short irradiations on thick targets are calculated. The 121I activity present at the optimal cooling time is then calculated for different energy degradation in the target and for different irradiation times (up to 13 h, 1 half life of 123I, saturation of 121I ). By comparing to the cumulative produced 123I in the same irradiation conditions, the evolution of the relative activity of both 121I (decreasing in time) and 121Te (increasing in time) is calculated. By defining maximal admissible contaminations levels for late use of the 123I solution, limits on target thickness are defined. [1] F. Tarkanyi et al. , Applied Radiation and Isotopes, 42, 1991, p221 [2] IAEA TECDOC 1211, Vienna 2001.

Primary author

Prof. Alex Hermanne (Cyclotron, Vrije Universiteit Brussel)


Prof. Anatoly Ignatyuk (Institute of Physics and Power Engineering (IPPE), Obninsk, Russia) Dr Ferenc Tarkanyi (Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen, Hungary) Dr Hermann Schweickert (Zyklotron AG ,Eggenstein, Germany) Mr Razvan Adam Rebeles (Vrije Universiteit Brussel (VUB), Brussels, Belgium) Mr S Spellerberg (3 Institut für Nuklearchemie, Forschungszentrum Jülich, Jülich, Germany) Dr Sandor Takacs (Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen, Hungary)

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