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Technetium-99 ( 99Tc) is an artificial radionuclide with long half-life (2.11×105y) and high accumulated fission yield from 235U and 239Pu. 99Tc discharged into the environment originates mainly from nuclear fuel reprocessing plants. In the oxidation conditions, Tc is mainly present as the pertechnetate ion, which is highly soluble and mobile in the environment. Therefore, long-lived 99Tc is considered to be one of the most important radionuclides in environmental safety assessment, nuclear waste management as well as radiation protection.
CIRP studied the determination method of 99Tc in water samples by using liquid scintillation counting (LSC) measurement and stable Re as chemical yield tracer. During the study, TiCl3 was tested as reductant to reduce Tc(IV) and Re(IV) for the first time. The co-precipitation of TcO2 -ReO2 with Ti (OH)3 for the pre-concentration of Tc was firstly observed. The chemical behaviors of Tc and Re on TK200 resin were investigated, and the decontamination factors of main interferences were also evaluated. It was found that TiCl3 was an excellent reductant under HCl medium, and its hydroxide showed a strong co-precipitation ability with Tc and Re at low HCl molarity. Tc can be effectively eluted from TK200 resin at low concentration of NH4 SCN, which can be directly mixed with scintillation cocktail without chemical quenching for LSC measurement compared with high concentration of HNO3. Additionally, the study shows that no chemical differences were observed between Tc and Re in the whole procedure, demonstrating that Re can be used to monitor the chemical yield of Tc.
Comparison of measured and expected activities of 99Tc in spiked water samples
The new method of determination was validated by the analysis of water samples spiked with known amounts of 99Tc. It is proposed by CIRP as a promising method for the determination of 99Tc in water samples. Furthermore, the method could be extended to rapid determination of low levels of 99Tc in large volume seawater samples combined with inductively coupled plasma mass spectrometry (ICP-MS) without any evaporation.
Contact: official@cirp.org.cn
