Radioactivity of iodine-126 as radio nuclide impurity at irradiation chamber in iodine-125 production

Center for Radioisotope and Radiopharmaceutical has been successful in iodine-125 production tests using enriched xenon gas. However, the radionuclide impurity of iodine-125 was detected in the 7^th production test. The radioactivity of iodine-126 in irradiation chamber could not be measured directly. The calculation of iodine-126 radioactivity at irradiation chamber, therefore, has been carried out. In this calculation, xenon-124 with enrichment of 82.4% was irradiated for 24 hours with neutron flux of 3x10¹³ n.s^-1.cm^-2. Calculation results showed that irradiation for 24 hours resulted in 11.7 mCi of iodine-126. After moving the xenon gas to the decay pot, the iodine-125 remained in the irradiation chamber. The iodine-125 was irradiated during reactor operation. At the end of 12^th day, the radioactivity of iodine-126 was 367 mCi. It revealed that most of the iodine-125 in the 7^th test product was iodine-125 produced in the previous production test. The mass of iodine in irradiation chamber when the xenon gas moved from irradiation chamber was 0.33 mg. This value was useful as a reference in the iodine filter maintenance. (author)