An electrolytic cell, essentially composed of a solid polymer electrolyte (SPE) film and porous dimensionally stable electrodes (DSEs), was designed to reduce the electrolytic voltage in an electrolyzer. The device achieved a tritium recovery factor of 0.836±0.021 for a volume reduction factor of five when operated at a current of 6 A, while maintaining a water bath temperature below 2 °C. Sample and standard waters were simultaneously enriched by connecting two electrolytic cells in series. The sample water was first enriched using a commercially available apparatus with a large electrolytic current of 50 A until the volume in the sample water was reduced to approximately one fifth of the original volume. This "two-stage electrolysis" enrichment was applied to coastal seawaters from the Aomori prefecture. Tritium concentrations, ranging from 0.2 to 0.5 Bq/L, were found, with a measurement error (i.e. a statistical error of one sigma) of ca. 10% of the obtained values.
