Abstract: A new method is presented for high purity ~(233)Pa separation from ~(237)Np usingTTA (2-thenoyltrifluoroacetone) as extractant. ~(233)Pa is extracted with an equalvolume of TTA in benzene from 8 mol/1 HNO_3 solution containing ~(237)Np, thenwashed the organic phase with 8 mol/1 HNO_3 three times. Subsequently, ~(233)Pa isreexacted into an equal volume of 1 mol/1 HNO_3-0.1 mol/1 HF from organicphase. The aqueous phase is washed by 0.5 mol/1 TTA in benzene. After all HFis removed by evaparation, and the residue was dissloved in 8 mol/1 HNO_3, theabove procedure is repeated once again. The purity of ~(233)Pa obtained by this method is high enough for study in geochronology of uranium series isotopes.