Electrolytic Enrichment of Tritium with Solid Polymer Electrolyte for Application to Environmental Measurements

We evaluated electrolytic separation factors of hydrogen isotopes by SPE (Solid Polymer Electrolyte) for application to environmental tritium analysis. The apparent separation factors _a for deuterium and _a for tritium were determined as 3.5 ± 0.1 and 6.2 ± 0.5, respectively. The tritium enrichment of 8.4 times was achieved, when a 1000 ml of sample water was electrolyzed to about 60 ml. The chemical composition changes before and after the electrolysis were examined, showing an increase in H⁺ and Na⁺ concentrations and a decrease in Mg²⁺ and Ca²⁺concentrations. F^-, which was not contained in the sample water, was detected after electrolysis accompanying with a reduction of SO₄^2-, Cl^- and NO₃^-. The memory of tritium and ions in the electrolysis cell after electrolysis was possible to be eliminated by washings with de-ionized water. Tritium concentrations of rain at Kumamoto, Japan were determined with a combination of the present electrolytic enrichment system and liquid scintillation counting.