Accurate determination of 129I concentrations and 129I/137Cs ratios in spent nuclear resins by Accelerator Mass Spectrometry

•In the context of radioactive waste management, this study aimed at measuring 129I in spent resins using accelerator mass spectrometry.•The treatment procedure included microwave acid digestion of samples, iodine extraction by CL resins and AgI precipitation.•Developed first on synthetic matrices, the chemical treatment procedure was then successfully applied to real resin samples.•129I concentrations ranged from 4 to 12 ng/g of dry resin.•Results are in agreement with previous measurements and support reference values currently used for nuclear resin management.

Determining long-lived radionuclide concentrations in radioactive waste has fundamental implications for the long-term management of storage sites. This paper focuses on the measurement of low 129I contents in ion exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). Iodine-129 concentrations were successfully determined using Accelerator Mass Spectrometry (AMS) following a chemical procedure which included (1) acid digestion of resin samples in HNO3/HClO4, (2) radioactive decontamination by selective iodine extraction using a new chromatographic resin (CL Resin), and (3) AgI precipitation. Measured 129I concentrations ranged from 4 to 12 ng/g, i.e. from 0.03 to 0.08 Bq/g. The calculation of 129I/137Cs activity ratios used for routine waste management produced values in agreement with the few available data for PWR resin samples.