Abstract
The purpose of this study is to develop a neutron activation method to determine trace amounts of <sup>129</sup> I in cement-solidified radwastes. The radwaste samples were alkaline fused using KOH and then <sup>129</sup> I and iodine carrier were chemically separated by solvent extraction before and after neutron irradiation. Both stable iodine ( <sup>127</sup> I) and <sup>129</sup> I can be activated by neutrons through <sup>127</sup> I (n, 2n) <sup>126</sup> I and <sup>129</sup> I (n, γ) <sup>130</sup> I reactions; their activated radionuclides were counted together with a high-purity germanium detector. The chemical recovery yields ranged from 30 to 60 %, and it was found that more than 99.9 % of interfering radionuclides can be removed using solvent extraction after neutron irradiation. The minimum detectable amounts can be lowered to less than 1 mBq g <sup>-1</sup> , which is superior to low energy γ-ray spectrometry by a factor of >10 <sup>2</sup> , on average. The established technique can be applied to re-evaluation of <sup>129</sup> I content in radwastes that can be re-classified to lower classes, and the cost for designing a final disposal facility can be significantly reduced. © 2013 Akadémiai Kiadó, Budapest, Hungary.