Evaluation of effective thermal extraction procedures for ³H determinations in radioactive waste characterization - 13147

Tritium is routinely encountered in a diverse range of matrices during decommissioning waste characterisation and land remediation. Measurement of ³H activity concentrations in wastes is integral to the decommissioning of nuclear and military sites, fusion research and radiopharmaceutical manufacturing facilities and research laboratories. As ³H is a low energy pure beta emitting radionuclide, in situ screening at low activities is not practically feasible and waste characterisation will typically involve the collection of a representative sub-sample followed by ex situ laboratory analysis. In order to obtain reliable data, it is vital that the sample is collected and stored in such a way as to prevent loss of ³H prior to analysis and that the analytical approach adopted is capable of quantitatively extracting the form of ³H present. To develop a robust sampling and analytical strategy the association of ³H in the sample must be well understood and this will depend on the origin of the ³H, the chemical form of ³H within the sample and the sample composition. A review of our research into ³H association in a range of commonly encountered sample matrices collected from different sites is presented. The implication of ³H speciation and sample composition on analytical strategies is considered and experience in the application of these procedures to current UK decommissioning programmes in both the nuclear and radiopharmaceutical industries is also discussed. A range of studies have been undertaken by GAU-Radioanalytical and Raddec International Ltd to investigate the association of ³H with a wide range of matrices typically encountered in decommissioning programs. The studies have specifically used operationally-contaminated materials to ensure that the samples are representative. By characterising thermal desorption profiles for these materials it has been possible to demonstrate that ³H association is dependent on the form of the ³H, the source of the ³H and the matrix of the material being contaminated. Such information essential in order to develop and validate sample collection, preservation and analysis strategies and underpins the quality of data being generated by the analytical laboratory.