Efficiency of tritium enrichment by electrolytic cell with multi-nickel-plates electrode and application to determination of tritium in environmental water

For the purpose of speeding up the tritium enrichment by electrolysis, we have produced an electrolytic cell with the multi-plate-electrode system instead of the commonly used single-plate-electrode, and examined the efficiencies for the tritium enrichment under the conditions of different current densities and electrode gaps. From the results, the tritium recovery and the separation factor β were found to be maximised under the condition of 70 mA/cm2 of current density and 1.6 mm of electrode gap, and they were 90 percent and 23, respectively. Using this cell, it took 28 hours to reduce 100 ml of a sample water to 10 ml, and took 2 days, including the time required for other operations, to determine the tritium concentration of 1.85 Bq/l (50 pCi/l) with the counting error of within +-10 percent. This method has been applied to determining the tritium concentrations of environmental samples from Yamato River region during July 1981 -- February 1983. They were in the range of 1.11 -- 9.48 Bq/l (30 -- 256 pCi/l). (author)