Isolation And Analysis Of Technetium - 99 In Solid Samples

Fission products can be used as signatures for many nuclear processes, such as reprocessing spent nuclear fuels, nuclear weapons tests, and for nuclear accidents. Moreover, an inventory of fission products is required, when a new type of fuel and/or reactor operating conditions is being investigated. The characterization of environmental samples collected from the vicinity of a nuclear facility is also necessary in order to control any possible release of radionuclides into the environment. Technetium-99is one of several long-lived fission products which cannot be detected directly from its radio emission, due to its low specific activity and low energy emissions. The most sensitive analytical technique which has been reported is by isotope dilution mass spectrometry with technetium-97as a yield tracer. Technetium-97is, however, not a natural isotope.97Ru can be obtained by the neutron capture of96Ru or from95Mo (a,2n). This isotope then decays to97Tc. Enriched96Ru is, however, not widely available. It would be more convenient to prepare97Tc by irradiating natural ruthenium metal in a high flux reactor. Natural ruthenium consists of96Ru(5.5%),98Ru(1.86%),99Ru(12.7%),100Ru(12.6%),101Ru(17%),102Ru(31.6%), and104Ru(18.7%). This means that at the end of the irradiation there is not only97Tc, but large amounts impurities that there are unchanged ruthenium and many new nuclides, such as103Ru and so on. In order to obtain97Tc of sufficient purity, a chemical separation procedure would be needed after the target has cooled.A method for the preparation of97Tc is first reported in this paper.97Tc was obtained by irradiation of a sample of natural ruthenium metal in a high flux reactor. After cooling for two years, the technetium was isolated from the sample by technique combining; deposition, solvent extraction and ion-exchange chromatography techniques.99mTc and103Ru were used as radio-tracers for the process. The results showed that more than70%of the Tc was recovered, the decontamination factor is more than2.3×107. The97Tc was calibrated by isotope dilution mass spectrometry with99Tc as the yield tracer. The final yield was29.56μg of97Tc suitable for use as a mass spectrometric spike (weight%97Tc spike:97Tc,84.77%;98Tc,15.03%;99Tc,0.20%).And an approach that can efficiently separate and determine technetium-99(as pertechnetate) in solid sample by nuclear materials is reported also. The samples were decomposed by potassium hydroxide/potassium nitrate. After the samples were fusible, technetium remains as anionic pertechnetate (TcO4-). The technetium was isolated from the sample by technique combining solvent extraction, anion exchange and solvent extraction. The recovery of the technetium was approximately70%for the overall process, While the amounts of impurities were too low to interfere with measurement of the technetium. After separation, technetium-99was measured by isotope dilution mass spectrometry with technetium-97as a spike. This method yielded detection limits of technetium-99is down to the order of nanograms. The uncertainty in measurement results is below3.0%. This method can be used for environmental assessment near nuclear fuel facilities, nuclear verification, measurement of nuclide migration, and other research fields.