Abstract: The release of tritium into environment from some nuclear facilities will cause tritium activity concentration variation in adjacent areas. The activity concentrations of tritium samples of air, ground water, rains and sea water around nuclear facilities were measured by a liquid scintillation counting (LSC) apparatus based on an external γ-standard method and an internal standard method. The relative deviations of these measurement data using the above two standard methods were -4.0% to 4.0%. The quenching calibration curves for four kinds of environmental water samples were made out according to internal standard efficiencies and the values of spectral quench parameter of the external standard (SQP(E)). The maximum difference between the efficiencies of two standard methods was 1.6%. The interference effects of carbon-14 and other β nuclides were generally negligible. For samples of efficiency value in the range of 21.5% to 24.5% without serious quench, their tritium activity concentrations were calculated using the external γ-standard quenching calibration curve with direct LSC measurement and relative deviations of results were between -6.35% to 4.41%, satisfying the requirements of routine monitoring of nuclear facilities.

Key words: tritium, liquid scintillation counting measurement, internal standard method, quenching calibration curves, nuclear facility