Solvent Extraction Recovery of Byproduct137Cs and90Sr from HNO3Solutions—A Technology Review and Assessment

Abstract

A principal purpose of this paper is to call out what is perceived to be a timely need for increased research to develop improved and new solvent extraction technology for recovery of ¹³⁷Cs and ⁹⁰Sr from strong (≥ 0.5M HNO₃) acid media, technology which can be quickly scaled up to routine plant-scale operation with highly radioactive waste solutions when needed. The present and forseeable future (2020) U.S. inventory of ¹³⁷Cs and ⁹⁰sr is listed; much of this inventory is expected to be available only in strongly acidic nuclear waste solutions. Comparison of available methods-precipitation and ion exchange as well as solvent extraction—for recovering ¹³⁷ Cs and ⁹⁰Sr from alkaline and acid media demonstrates, as expected, that very limited technology is available for use with strongly acidic solutions. Solvent extraction procedures which employ either macrocyclic polyethers (crown ethers) or dicarbolide. H⁺{[π-(3)-1, 2-B₉C₂H₁₁Cl₂±₂Co}⁻, to extract ¹³⁷Cs and ⁹⁰Sr from ≥ 0.5M HNO₃ solutions have recently been proposed. But, in their present state of development, both the crown ether and dicarbolide extraction