The measurement of technetium-99 and iodine-129 in waste water from pressurized nuclear-power reactors

The program for measuring the dispersal presence of contaminating nuclides in waste streams produced by pressurized-water-reactor (PWR) power plants required the establishment of analytical procedures for a number of nuclides. In this report the procedure to assess 99Tc and 129I content in liquid samples using liquid-scintillation counting is presented. 99Tc and 129I are adsorbed on AG 1 X2 ion-exchange resin. 129I is then eluted with NaOCl and further purified by liquid-liquid extraction using carbon tetrachloride and an aqueous solution of sodium thiosulphate. 99Tc is eluted with hot nitric acid (6 M/60 degrees C). If necessary any 60Co present in the sample is separated by liquid-liquid extraction of the cobalt-TTA complex with iso-BuOH. The overall recovery yield is 96.5 +/- 2.5% for 99Tc and 90.1 +/- 6.2% for 129I. Finally beta-activity is measured by liquid-scintillation counting. A limit of detection of 5 Bq/L can thus be obtained for both 99Tc and 129I.