A Suite of Robust Radioanalytical Techniques for the Determination of Tritium and Other Volatile Radionuclides in Decommissioning Wastes and Environmental Matrices

Tritium is ubiquitous in and around nuclear plants, being formed via neutron capture by ²H, ⁶Li, ¹⁰B and ¹⁴N and via ternary fission. The highly mobile nature of ³H species results in widespread distribution of the radionuclide. Predictive modeling of ³H activity concentrations is challenging and direct measurement of ³H activities in materials is the preferred approach to underpin waste and environmental assessments. For well over a decade, the UK nuclear industry has engaged in a significant program of site decommissioning of its first generation reactors. This has resulted in a high demand for the rapid characterization of ³H in a diverse range of matrices, including concretes, metals, plastics, sludges, resins, soils and biota. To support such assessments, it has been necessary to develop dedicated instrumentation in parallel with robust radioanalytical methodologies; namely a multi-tube furnace and a high-capacity, closed (pressurized) oxygen combustion system. Data are presented on the development and validation of these instruments, designed specifically to enable the quantitative extraction of ³H (and other volatile radionuclides) from diverse sample types. Furthermore the furnace system has been employed as a tool to gain insights into the ³H association in decommissioning and environmental matrices exposed to ³H arising from nuclear power plant operations through tritium evolution with temperature profiling. The impact of the chemical speciation of ³H on analytical strategy is discussed. A major benefit of the multi-sample furnace is its ease of use and applicability to ³H determination in virtually any sample type. The complementary HBO₂ oxygen combustion system has been developed for the quantitative oxidation of organic-rich samples (e.g. wood, plastic, oil, biota) and analytical data prove its effectiveness.