Characterisation of stainless steel–synroc interactions under hot isostatic pressing (HIPing) conditions H. Li, Y. Zhang * , P.J. McGlinn, S. Moricca, B.D. Begg, E.R. Vance Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia Received 3 January 2006; accepted 2 May 2006 Abstract Stainless steel/synroc interactions under HIPing conditions (1280 °C/100 MPa/3 h) have been studied. The synroc material was based on the zirconolite-rich ceramic targeted for surplus Pu disposition. A 300 mm-thick complex reaction interface with 8 distinct layers has been identified. Although the Fe diffusion controlled interactions have changed the microstructures of the synroc phases at the interface, they do not affect the integrity of synroc and are unlikely to have any detrimental effect on this synroc derivative. Ó 2006 Elsevier B.V. All rights reserved. 1. Introduction Synroc, a titanate-based ceramic, was first devel- oped in the late 1970s [1,2] for immobilisation of HLW from Purex-type reprocessing of spent nuclear fuels. Since then, various synroc formula- tions targeting different high-level waste streams have been developed [3,4]. Synroc variations have been developed around synroc-C in which zircono- lite (CaZrTi 2 O 7 ) and perovskite (CaTiO 3 ) accom- modate actinides, Sr and rare earth fission products; hollandite [Ba(Al,Ti) 2 Ti 6 O 16 ] incorpo- rates Cs and Rb, while other fission products such as Tc, Ru, Rh, Pd etc. form very fine metal particles. In the early 1990s, some zirconolite-rich and pyrochlore-rich (CaATi 2 O 7 , A = actinides) formu- lations were also developed for immobilisation of surplus plutonium [5,6]. Hf and Gd were included in these formulations as neutron absorbers. Parallel to the synroc formulation development, advanced synroc processing technologies, including hot uniaxial pressing (HUP), sintering, cold crucible induction melting (CCIM) and hot isostatic pressing (HIP), have also been extensively studied [7,8]. HIP- ing has been widely applied in the last 10 years due to its advantages for processing of high-level radio- active wastes. Firstly, the HIPing process uses sealed stainless steel cans which eliminate radioac- tive volatile emissions during the high-temperature consolidation process. Subsequently there is no significant amount of secondary waste to deal with and no high temperature off-gas treatment is required other than that arising during lower temperature calcination. Secondly, the HIPing pro- cess does not require tight control of the electrical properties, melting temperature, or viscosity of the 0022-3115/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2006.05.014 * Corresponding author. Tel.: +61 2 9717 9156; fax: +61 2 9543 7179. E-mail address: yzx@ansto.gov.au (Y. Zhang). Journal of Nuclear Materials 355 (2006) 136–141 www.elsevier.com/locate/jnucmat