Third phase formation in the extraction of thorium nitrate by trialkyl phosphates

Abstract

A review. Third phase formation is a key issue in the extn. of plutonium in high concns. by trialkyl phosphates. A no. of parameters influence this phenomenon, among which the nature of the extractant (the carbon chain length, branching) is the important one. Studies on third phase formation in thorium extn. could provide insights into the phenomenon, given the challenges in making measurements on plutonium systems. However, the extrapolation of the results obtained for thorium extn. to plutonium systems is difficult in many instances. In the present paper, results of the extensive investigations carried out at IGCAR on third phase formation in the extn. of Th(NO3)4 by trialkyl phosphates (TalP) are presented. The effects of various parameters such as extractant concn., temp., structure of diluent, equil. aq. phase acidity and extractant structure on third phase formation in the extn. of Th(NO3)4 by trialkyl phosphates are discussed. Empirical equations to predict Limiting Org. Concn. (LOC) with respect to various parameters for third phase formation in the extn. of Th(NO3)4 by trialkyl phosphates from nitric acid media are also derived and the calcd. LOC values are compared with the exptl. values. An effort is made to discuss Pu extn. systems based on the bank of data accumulated. [on SciFinder(R)]