Improvement of Electrode of Tritium Enrichment Cell and Application to Tritium Monitoring in Environmental Surface Water at South Osaka Area

The experimental studies on the improvement of electrode materials used for the electrolytic enrichment of tritium and on the establishment of rapid procedure for the analysis of tritium and its application to tritium monitoring in environmental surface water at south Osaka area were carried out. The more efficient recovery rate and reappearance of tritium were obtained by the trial of the exchange of the electrode material from nickel (Ni) to iron (Fe) at high current condition. However, by considering the electrolytic corrosiveness of iron, a combined multi plate electrode of Fe (-)-Ni (+) (an effective surface area ; 63cm2) was adopted. In the case of such operational conditions that a current density ; 180 mA/cm2 and a cooling temperature ; 5°C using a 100 ml glass cell inserted into the electrode, time required for decreasing the volume of sample solution from 100 ml to 15 ml was more than 22 h. In addition the recovery rate and the concentration ratio of tritium were 90% and 6 times respectively. Then, the tritium activity of the water sample could be counted rapidly with a relative counting error of ±20% for 4 h in a low level liquid scintillation counter. By the trial using the above mentioned method for the tritium monitoring in environmental surface water at south Osaka area from 1986 to 1992, it was proved that the tritium activities decreased to the naturally producing level of tritium (BG) during this term and the decreasing half times of tritium concentration in this area by dilution were about 4 years.