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Measurement of difficult-to-measure isotopes

Measurement of difficult-to-measure isotopes

 With gamma-spectrometry: 108mAg, 129I
 With LSC:3H, 14C,36Cl, 90Sr, 99Tc
 With alpha-spectrometry: transuranic isotopes (e.g. 239+240Pu, 241Am)
 Using ICP-MS: 79Se, 93Zr, 107Pd

Difficult-to-measure (DTM) isotopesare usually either pure alpha/beta emitters or have only very low energy and intensity X-ray or γ-ray lines. As a result, the determination of their concentrationsis possible only after radiochemical separations of various complexities. If the necessary conditions (physical-chemical form and radiochemical purity) are met, the following techniques are used for measurements:

Gamma-spectrometry:

  • 108mAg (silver-oxide precipitation on filter plate),
  • 129I (AgI precipitation on filter plate)

LSC:

  • 3H (high-purity distilled water + UltimaGold LLT)
  • 14C (NaOH/NaHCO3 solution + Hionic-Fluor or BaCO3 precipitate dispersed in InstaGel Plus)
  • 36Cl (NaCl solution in InstaGel Plus)
  • 90Sr (strontium-oxalate precipitate dispersed in InstaGel Plus)
  • 99Tc (TEVA resindispersed in InstaGel Plus)

Alpha-spectrometry

  • NdF3 micro-precipitate plates of transuranic isotopes (e.g. 239+240Pu, 241Am)

ICP-MS:

  • In case of some long-lived beta-emitters (e.g. 79Se, 93Zr, 107Pd), conventional counting methods, like LSC cannot be applied because the radiotracer (95Zr, 103Pd) for chemical yield determination wouldinterfere with it. However, the long half-life of these isotopes mean that they can be effectively measured by ICP-MS if the possible interferences are removed.
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