129I and129I/127I ratio measurements in environmental samples by RNAA, AMS and directγ-X spectrometry. Intercomparison exercises

Abstract

129I, is a natural long-lived isotope, with a half-life of 15.7 million years, also artificially produced in nuclear power plant and released in liquid and gaseous effluents of nuclear fuel reprocessing plants. Due to the lack of environmental international reference material for 129I, interlaboratory comparison exercises are very rare and validation of new measurement techniques is very difficult to achieve. This study presents three intercomparison exercises on the 129I and 129I/127I measurements using three different techniques: Radiochemical Neutron Activation Analysis, Accelerator Mass Spectrometry and direct γ-X spectrometry associated with Ionic Chromatography. The first intercomparison was performed on a Fucus serratus sample, leading to propose it as a reference material. The others intercomparison exercises were performed on samples of different biological matrices, marine and terrestrial, presenting various 129I activity levels. The different intercomparison exercises results showed a good agreement between the three techniques on the considered environmental matrices, for samples with 129I activity comprised between 0.2 and 200 Bq.kg-1 dry weight.