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.