Production of Iodine-128 by Small Research Reactor

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A study was conducted on the preparation of a high specific activity ¹²⁸I utilizing hot atom effects.
Crystalline iodine pentoxide, ammonium iodate and iodic acid were irradiated in the pneumatic tube and the rotary rack of a TRIGA-II reactor. Variation of the ¹²⁸I retention with duration of irradiation and with neutron beam intensity was determined. The retention of 128I in the iodate fractions was found to increase during the first 30 min, after which it stabilized. Ammonium iodate showed the lowest values for ¹²⁸I retention. The retention generally increased with neutron beam intensity.
The specific activity of ¹²⁸I was determined from the amount of iodine simultaneously produced by the decomposition of the samples by radiation. The radiation decomposition increased linearly with irradiation time. Ammonium iodate was found to have decomposed much more than iodine pentoxide and iodic acid.
The enrichment factors of ¹²⁸I were calculated on the basis of the results obtained from these experiments. Ammonium iodate showed the highest enrichment factor. Consequently, a high specific activity ¹²⁸I was prepared by irradiating 500 mg of ammonium iodate for 30 min in pneumatic tube. The resulting enrichment factor of 128I was 1.3×10⁴. Active impurities in the product were found to be less than 1 ppm.