BEHAVIOR OF TRITIUM IN THE PUREX PROCESS

The tri-n-butyl phosphate(TBP) extraction behavior of tritium was stud ied to support the evaluation of tritium confinement in the Purer proc ess. The tritium distribution ratio in the system of U - 30 % TBP/n-do decane(nDD) - HNO3 -H2O was measured in batch-wise experiments. The tr itium decontamination factor in a tritium scrubbing step was measured in chemical flow sheet experiments using a 6 stage mixer-settler havin g an internal recycle system of aqueous solution in each stage. Tritiu m was mainly extracted in the forms of water and nitric acid in the sy stem. Less than 1 % of the amount of tritium in the organic phase was fixed in the degradation products of the solvent. A tritium decontamin ation factor of about 500 in the tritium scrubbing step was obtained u nder the conditions of about 85 g-U/dm(3) of uranium concentration in the irradiated solvent(30 % TBP/nDD), 3 M nitric acid in the tritium s crubbing solution and an organic : aqueous phase ratio of 25.