Evaluation of the sample preparation method for environmental reference matrices suitable for organically-bound tritium interlaboratory comparison exercises

The measurements for tritium in the environmental samples are usually related to the tissue-free water tritium (TFWT). Research studies for the complex behavior of tritium were performed over the years due to the increased probability of elevated tritium concentrations to be released in the environment. Laboratory methods that enable to accurately determine the various forms of tritium, including organically-bound tritium (OBT) were developed and validated through inter-laboratory comparison (ILC) exercises, by the Environmental Control Laboratory of the Cernavoda Nuclear Power Plant (NPP) from Romania. Furthermore, sample preparation methods for OBT determinations were evaluated to develop different types of reference materials of environmental samples to be tested through ILC exercises. This paper describes the international Organically-Bound Tritium (OBT) intercomparison exercise, organized by the Cernavoda Nuclear Power Plant (NPP) in 2024–2025, using fruit sample (grapes) from Cernavoda town and the result evaluation for the participating laboratories performed using robust analysis (Algorithm A) method described in the ISO 13528:2022 standard. The results obtained are encouraging as most of the participating laboratories did not change the observed dispersion of the results for activity concentration level around 80 Bq/L of combustion water, although they performed different methods for sample preparation and different measurement systems for tritium counting.