[en] Extraction equilibria are studied for aqueous (UO2)(NO3)2-Pu(NO3)4-HNO3 and 20% and 30% TBP in n-dodecane at 25 and 60 degrees C. Data are obtained for the stable two-phase systems. Regions near the critical point [formation of a second organic phase at high Pu(NO3)4 concentration] are also investigated. The behavior of Pa in the system is studied