C. HILL, CEA, France

Abstract: This chapter discusses the methodology deployed in the European partitioning strategy to design highly selective extractants for long-lived radionuclide separation: calix[4]arenes for caesium, malonamides for the co-extraction of trivalent minor actinides (Am, Cm) and lanthanides (Ln(III)), and nitrogen-donor ligands, such as bis-triazinyl-pyridines, for the separation of trivalent minor actinides from Ln(III).

Key words: selectivity, calixarene-crowns, diamides, bis-triazinyl-pyridines.

11.1 Introduction

In the quest to develop mature technologies capable of partitioning long — lived radionuclides (LLRN) from spent nuclear fuels, hydrometallurgy has consensually become a reference route, probably because of the successes of PUREX1 process industrial implementations in Europe and elsewhere since the 1970s (Benedict et al., 1981, Schulz et al., 1990, Birkett et al., 2005). Furthermore, solvent extraction allows high selectivity and recovery yields to be reached without generating excessive volumes of secondary waste; its flexibility in adapting to various spent nuclear fuel characteristics and fuel cycle options, as envisaged in the GenIV initiative, appears industrially attractive. Solvent extraction has been a subject of intensive nuclear research activities in Europe, Russia, China, Japan, India, and the United States since the early 1960s (Marcus and Kertes, 1969, Sekine and Hasegawa, 1977, Musikas, 1986, Rydberg et al., 1992, Danesi, 2004, Rydberg et al., 2004).

After a brief introduction on the advantages of the Partitioning and Transmutation (P&T) strategy, this chapter identifies the LLRN targeted in the European P&T policy. The methodology deployed to design highly 1 PUREX process, for Plutonium URanium EXtraction selective lipophilic compounds is then illustrated by three examples: (i) calix[4]arenes for caesium separation, (ii) diamides for the co-extraction of trivalent minor actinides and lanthanides from PUREX raffinates, and

(iii) nitrogen-donor ligands for the discrimination between trivalent minor actinides and lanthanides. Finally, the main progress achieved in these respective processes is described.