Low-level tritium assay in water samples by electrolytic enrichment and liquid-scintillation counting in the IAEA laboratory

Decreasing tritium concentration in the atmosphere and hydrosphere requires more sensitive methods for tritium assay in environmental water samples. In laboratories where large numbers of samples are processed these methods must be simple and less labour- and time-consuming. Progress in tritium assay during recent years has been achieved mainly through the availability of better liquid-scintillation spectrometers and optimization of the electrolytic enrichment procedure (the helium-3 in-growth method is not discussed in this paper). The paper describes procedures and methods used at present in the IAEA laboratory, including the new electrolysis system (higher enrichment factor) and the new liquid-scintillation spectrometer (large volume). Other factors influencing the tritium measurements such as the possibility of sample contamination, storage of samples, stability of electrolytic cells etc., are also discussed in the paper. (author)