Abstract: DETERMINATION OF 99Tc IN UO2（N03）2-Pu（NO3）4-HNO3 BY LIQUID SCINTILLATION COUNTINGZhu Guohui;Xie Wucheng(China Institute of Atomic Energy,P. O. Box 275（26）,Beijins 102413)Abstract:The determination of~(99)Tc in a system of UO2（NO3）2 －Pu（NO3）4 and HNO3 by a liquid scintillation counting is developed．The effects of sample volume,amount of scintillation cocktail,nitric acid, uranium and plutonium on the determination of 99Tc have been investigated．The isolation and purification of 99Tc using 2,6-dimethyl pyridine extraction from alkaline medium followed the stripping of 99Tc from 30％TBP-kerosene loaded with ~(99)Tc using CCl4 as diluent have also been studied．A determination procedure of ~(99)Tc by the liquid scintillation counting with 2,6-dimethyl pyridine extraction is recommended．The relative standard deviation for the determination of ~99Tc using this procedure is 0．6％. The procedure has been adapted to the samples containing uranium,plutonium and ~99Tc. The experimental results show that the analytical procedure for determining~(99)Tc is satisfactory.Keywords:Technetium-99 2,6-dimethly pyridine Liquid scintillation counting