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

¹ IPSN/DPRE/SERNAT, CEN Saclay, bâtiment 130, 91191 Gif-sur-Yvette cedex, France
² IPSN/DIR-DDP, BP. 6, 92265 Fontenay-aux-Roses cedex, France
³ CEA/DSM/DRECAM/LPS, CEN Saclay, bâtiment 647, 91191 Gif-sur-Yvette cedex, France
⁴ CSNSM/IN2P3/CNRS, bâtiment 108, 91405 Orsay, France

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.