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Communication Dans Un Congrès Année : 2023

Quantification of 129 I in milk at low level for environmental monitoring

Résumé

Iodine is an extremely volatile element which exist in the environment with different oxidation states: -1, 0, +1, +5 and +7 . These physico-chemical properties complicate its extraction and quantification. Among the 37 iodine isotopes, 127I is the only stable one and 129I is the radioisotope with the longest half-life (16.1 x 106 y) . 129I is chronically and regulatory released by fuel reprocessing plants e.g. La Hague (France) or in case of an accident. These releases can contaminate the French coastline and the adjacent agricultural land to these discharge zones could be enriched with iodine 129. This radionuclide will thus be present into the food chain and can be ingested by humans. A regular monitoring of 129I concentration in milk is therefore necessary to protect the population and estimate the ingestion dose. Currently, in our laboratory, the quantification of 129I in milk is carried out by gamma spectrometry 12 times a year. There is a chemical pre-treatment before the measurement, involving a purification on ionic resin and liquid-liquid extraction using 50 mL of liquid carbon tetrachloride (CCl4). This analysis has two major drawbacks. First, CCl4 is a carcinogenic, mutagenic and reprotoxic (CMR) solvent which is no longer marketed in France under the REACH regulation. On the other hand, because of the low efficiency of γ-spectroscopy for 129I determination, the detection limits with this technic are often higher than the environmental background. In this work, a safe and innovative method to quantify 129I in milk was developed. It is based on an extraction followed by a purification with two different specific resins. The chemical yield determination is based on stable iodine measurement by ICP-MS*. Moreover, the gamma geometry was optimized to improve the limit of detection. Indeed, the use of a well detector has improved detection efficiency and reduced the volume required, enabling a more concentrated sample measurement. This method has proven its effectiveness, offering a good chemical yield (> 80 %) while making chemical treatment safer and faster.
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irsn-04415690 , version 1 (26-01-2024)

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  • HAL Id : irsn-04415690 , version 1

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Coralie Carrier, Azza Habibi, Anh-Thi Tran, Delphine Haloche, Celine Augeray. Quantification of 129 I in milk at low level for environmental monitoring. 66TH RRMC - Radiobioassay & Radiochemical Measurements Conference, Oct 2023, West Palm Beach, Florida, United States. ⟨irsn-04415690⟩
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