Influence on the Chemistry Quenching of Low Level Tritium in Natural Water by the Solid Polymer Electrolysis Enrichment Method

The Solid Polymer Electrolysis (SPE) enrichment method is a practical way to measure low level tritium (<1 Bq/m³) in natural water samples. However, the concentrated liquid samples are acidified by impurity ions from water samples or the process of water sample pretreatment with a SPE electrolysis device, which results in perturbation when liquid scintillation is added progressively to the concentrated liquid. Consequently, the radioactive activity of tritium will be lower than the reference value because of the chemistry quenching effect occurring in the measurement process. The influence of chemistry quenching caused by impurity ions, pH value and electrical conductivity of the low level tritium samples in the tritium measurement results are discussed in this paper. The results show that, to avoid the chemistry quenching caused by impurity ions deposited in SPE electrolysis device and improve the accuracy of measurement counting, it is necessary to keep the pH value neutral and the electrical conductivity ≤1 μS/cm. Using the ion and acid-base hybrid exchange resin column separates impurity ions for high electrical conductivity (>1 μS/cm) or acidification pH samples. For water samples the impurity ions taken by the polymer film, can be used to adjust the pH value with tiny amounts of ammonia to avoid chemistry quenching and thus reduce the low counting of the tritium natural water samples.