Methods and procedures applied


III. Radiochemical analysis

  1. γ -spectrometry: 134Cs, 137Cs, 110mAg, 129I, 60Co
    • radwaste
    • water from observation wells
    • geological media
  2. LSC or GPC: T, 14C, 85Kr
    • radwaste
    • water from observation wells
    • geological media
  • 63Ni, 36Cl, 90Sr, 99Tc
    • radwaste
    • water from observation wells
    • geological media

Combined method for determination of 3H, 129I and 99Tc:

Inactive KI was added to the samples, weighted into a reaction vessel and dried. H2O2 + H2SO4 were added in small amounts to the dried sample until all the material was digested. The elemental iodine captured into the CCl4 solution was washed with nitric acid and reduced to iodide with NaHSO3 and back extracted to water. Acidified silver nitrate solution was added to precipitate silver iodide. The samples mounted onto aluminum rings were measured for 129I activity using a HPGe γ-ray spectrometer (Canberra Model BE5030).

The evolved CO2 was trapped in the form of BaCO3, which was dried and mixed with phosphoric acid in order to obtain CO2 gas. CO2 may contain traces of SO2, which was trapped in H2O2 solution. The pure CO2 was mixed with dead CO2 and proportional gas counting was used for activity measurement of radiocarbon.

The remaining solution in the reaction vessel was used for measurement of 99Tc. The solution was neutralised with sodium hydroxide. The sodium sulphate precipitation was removed by filtration. KReO4 was added as a carrier. The rhenium together with the technetium were precipitated in the form of Re2S7 and Tc2S7 which were filtrated and dissolved in H2O2. Amberlite XAD-7 resin was used to remove any organic material remaining after peroxide treatment. TEVAˇSpec column was used for separation Tc from the remaining radionuclides after decreasing the ion concentration of the solution. The 99Tc was removed from the column with 8N HNO3 and whole enrichment process was repeated once again. LSC technique was used for activity measurement. The chemical yield was tested using 99mTc tracer.

Vacuum distillation was used to determine tritium activity of the evaporator concentrates and used resin samples. The tritium activity of the collected water was measured with LSC technique. 3H concentration of the dried resin was measured after burning its hydrogen content into water with CuO in a glass ampoule. Tritium in other form than water have not been measured in evaporator concentrates.

The LSC instrument used for 99Tc, 3H measurements is a Tri-Carb 3170 TR/SL, manufactured by Canberra-Packard Instruments.

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