Immobilization of fission products arising from pyrometallurgical reprocessing in chloride media G. Leturcq * , A. Grandjean, D. Rigaud, P. Perouty, M. Charlot CEA Marcoule DTCD, BP 17171, 30207 Bagnols sur Ce `ze, France Received 4 January 2005; accepted 14 June 2005 Abstract Spent nuclear fuel reprocessing to recover energy-producing elements such as uranium or plutonium can be performed by a pyrochemical process. In such method, the actinides and fission products are extracted by electrodeposition in a molten chloride medium. These processes generate chlorinated alkali salt flows contaminated by fission products, mainly Cs, Ba, Sr and rare earth elements constituting high-level waste. Two possible alternatives are investigated for managing this wasteform; a protocol is described for dechlorinating the fission products to allow vitrification, and mineral phases capable of immobilizing chlorides are listed to allow specification of a dedicated ceramic matrix suitable for containment of these chlorinated waste streams. The results of tests to synthesize chlorosilicate phases are also discussed. Ó 2005 Elsevier B.V. All rights reserved. 1. Introduction In order to recover high-energy elements such as uranium or plutonium, the reprocessing of spent nuclear fuel can be performed by a pyrochemical process [1]. In one such method developed at the Argonne National Laboratory [2], the actinides andfissionproductsareextractedbyelectrodeposit- ion in a molten chloride medium. This extraction process is based on the distribution of the elements between a dense liquid or solid phase in which the elements are present in the metallic state, and a salt phaseinwhichtheelementsarepresentaschlorides. Reprocessing then comprises several successive steps: separation of the reducible elements (noble metals and other elements: Mo, Pd, Tc, Ru, Rh, Zr), separation of the actinides and lanthanides, and treatment of the bath for recycling. During extraction, the chloride bath becomes concentrated with radionuclide chlorides including alkali metals (Cs, Na, etc.), alkaline earth metals (Sr,Ba)andafewrareearthelements.Thesefission products significantly modify the physical and chemical characteristics of the salt, e.g. by increas- ing the salt melting point and contaminating the extractioncathodewithfissionproducts.Thechlori- nated salt must then be regenerated or replaced. Since it contains radionucleides such as 137 Cs and 90 Sr the salt is a high-level waste and highly water- soluble thus requires a specific treatment to insure 0022-3115/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2005.06.026 * Correspondingauthor.Tel.:+33466796376;fax:+33466 79 18 80. E-mail address: gilles.leturcq@cea.fr (G. Leturcq). Journal of Nuclear Materials 347 (2005) 1–11 www.elsevier.com/locate/jnucmat