Determination of tritium concentration in fuel reprocessing liquid waste by vacuum freeze distillation

The vacuum freeze distillation method was successfully applied to the preparation of radiochemically pure water samples used for determining the tritium concentration in highly radioactive liquid waste produced in nuclear fuel reprocessing. This method yielded a decontamination factor exceeding 105 for radioruthenium and other long-lived fission products. The isotope effect on the tritium concentration was corrected by applying an enrichment factor determined from experiment. A small portion of the high level liquid waste solution was taken from the Reprocessing Plant of the Japan Atomic Energy Research Institute, neutralized with 2N sodium hydroxide, and subjected to the vacuum freeze distillation, The distillate was subsequently analyzed for tritium by liquid scintillation counting. The tritium concentration in the waste solution was found to be approximately 0.13μCi/ml, which corresponded to about 70% of the total tritium contained in the original spent fuel rods. (auth.)