Radiochemical analysis of 129I in radioactive waste streams

129I is the longest lived of the volatile radionuclides produced in the nuclear fuel cycle. This radionuclide emits soft β-particles, a weak γ-ray and X-rays. Since the half-life of 129I is 1.57 x 107 y, the evaluation of optimum waste management practices, for this radionuclide, has received special consideration. This work proposes an analytical method for 129I in radioactive ion exchange resins and evaporator concentrates based on two methods. The first method consists in direct measurement, without chemical separation, by low energy γ-ray spectrometry. The achieved detection limit of 129I, with 60 h of counting time, is 0.2 Bq. The second method is based on a radiochemical separation process consisting in two precipitation steps of the β-γ emitters present in the samples and 129I measurement by low energy γ-rays spectrometry. The achieved detection limit of 129I, with 5 h of counting time, is 0.02 Bq, ten times lower than those achieved with the direct measurement method. (orig.)