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Purification and activity standardisation of a (166m)Ho solution
Youcef Nedjadi1, Philippe Spring, Claude Bailat
1Institut Universitaire de Radiophysique Appliquée, Grand Pré 1, 1007 Lausanne, Switzerland.
Summary
This study standardized a holmium-166m solution for use as a reference source. After purification to remove europium impurities, precise measurements confirmed its activity concentration, contributing to international standards.
Area of Science:
- Nuclear physics and metrology
- Radiochemistry and analytical chemistry
- Applied radiation science
Background:
- The need for reliable reference sources in ionization chambers.
- Challenges in standardizing long-lived radionuclides like holmium-166m.
- Presence of europium impurities in commercially sourced (166m)Ho solutions.
Purpose of the Study:
- To standardize a commercially available (166m)Ho solution for use as a reference source.
- To accurately determine the activity concentration of the purified (166m)Ho solution.
- To contribute to the Système International de Référence (SIR) through accurate radionuclide standardization.
Main Methods:
- Purification of (166m)Ho from europium impurities using ion-exchange chromatography.
- Activity concentration determination via 4π(PC)β-γ coincidence spectrometry.
- Activity concentration measurement using 4πγ (NaI) integral counting with Monte Carlo simulations (GEANT code).
- High-purity germanium (HPGe) gamma spectrometry for impurity analysis.
Main Results:
- Successful separation of holmium from europium impurities, confirmed by HPGe measurements (detection limits <0.03%).
- Consistent results from 4πβ-γ coincidence measurements at different gamma energy settings.
- Activity concentration of the purified (166m)Ho solution determined as 45.640 ± 0.098 kBq/g (0.21%, k=1).
- Agreement within 0.15% between 4πβ-γ coincidence and 4πγ (NaI) methods.
Conclusions:
- The developed purification and standardization methods provide a reliable reference source of (166m)Ho.
- The standardized solution and its activity concentration are suitable for international intercomparisons.
- This work enhances the traceability of radioactivity measurements within the international system of units.
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