Background : Selenium-73 (T 1/2 =7.1h) and Selenium-75 (T 1/2 =119.8d) are useful radioisotopes in many research fields. The wide ranges of applications of these radioisotopes arose great interest for their production. Simultaneous production of 73 Se and 75 Se is more cost-effective and less time-consuming.

Materials and Methods : 73 As (p, 3n) 73 Se and 75 As (p,n) 75 Se reactions were determined as the best choices for the production of 73 Se and 75 Se radioisotopes, according to the present facilities and conditions. The bombardment was performed by 30 MeV protons in Cyclone 30-IBA accelerator. ALICE and SRIM nuclear codes were used to determine the best energy and target thicknesses. Targets were specifically designed for simultaneous production of the radioisotopes as two consecutive pellets. Chemical processing was performed by no carrier added solvent extraction method. Radio-TLC was performed on polymer backed silica gel. A colorimetricmethod was used for chemical quality control. Radionuclidic quality control of the inal products was carried out by gamma spectroscopy with HPGe detector.

Results: The production yield was 5.3 mCi/µAh for 73 Se and 50 µCi/µAh and 678 µCi/µAh for 75 Se in the first and second pellets respectively. The specific activity of 73 Se was 1.06 mCi/ml and that of 75 Se was 135.6 µCi/ml after one hour of proton bombardment with a current of 5µA. The isotopic purity of 73 Se was 99% in the first pellet and that of 75 Se was 100% in the second, just after the end of bombardment. A 0.04 ppm colorimetric method showed no traces of arsenic in the final product.

Conclusion : The quick and inexpensive procedure used in this research, resulted in high yields,high chemical and high isotopic purity for both radioisotopes. It can be considered as the method of choice for simultaneous production of 73 Se and 75 Se. Iran . J. Radiat. Res., 2004 2 (1): 45-51